MCQ Flashcards
40-year-old man with Marfan’s syndrome is to undergo thoraco-abdominal aortic reconstruction for chronic aortic dissection. An intrathecal catheter is inserted. The purpose for this is to
A. allow drainage of cerebrospinal fluid (CSF)
B. allow intrathecal administration of metabolic substrates
C. allow intrathecal administration of neuroprotective drugs
D. cool the spinal cord
E. facilitate spinal cord function monitoring
ANSWER A
The blood supply to the spinal cord and the kidney is reduced by 84-90% after cross-clamping the descending thoracic aorta at the level of the left subclavian artery.
Elective thoracic aortic repair has a 0.4% incidence of permanent cord injury, but emergency repair of an aortic rupture has a 24-40% incidence.
The incidence of perioperative spinal cord injury is increased by:
* cross-clamp times of greater than 30 mins, as the warm ischaemia time for the cord is 20-30 mins;
* high level of thoracic cross-clamping;
* emergency surgery (eg acute dissection or rupture when there are no collaterals);
* greater longitudinal extent of the aneurysm;
* patient age greater than 70 years; and,
* no prophylactic measures undertaken
Intraoperative methods of spinal cord protection include
-swift surgery, with identification and preservation of vital cord supply blood vessels
-cross-clamp times of less than 30 minutes
-Lumbar CSF drainage to increase the spinal cord perfusion pressure
-mild hypothermia (34-35 °C), which decreases the cerebral metabolic rate for oxygen by 20%
-Preliminary reports suggest intrathecal papaverine may provide some cord protection, as a result of its arteriolar vasodilating, calcium channel blocking and oxygen free radical scavenging properties
-Spinal cord somatosensory evoked potential (SSEP) monitoring has been recommended to detect spinal cord ischaemia ,
Shunts to improve perfusion distal to the cross-clamp have not influenced the incidence of paraplegia, due to the high resistance to retrograde flow in the ASA above the artery of Adamkiewicz inflow.
Describe the effect on ventilation/oxygenation with these misplaced DLT
AL = correct positioning of the a left sided DLT
BL = L DLT too far in, resulting in ventilation of left lower or left upper lobe through the bronchial lumen, hypoxemia
CL = L DLT no for in enough, resulting in partial obstruction when ventilating through the tracheal lumen
DL = intubation of operative lung, resulting in severe hypoxemia when ventilating through bronchial lumen, but improvement during ventilating through tracheal lumen.
BR = introduced to far, resulting in ventilation of right middle and right lower lobe only, right upper is not ventilated, resulting in hypoxemia
The most appropriate method for improving oxygenation during one lung anaesthesia, after institution of an FiO2 of 1.0, is application of
A. 5cm H2O CPAP to the non-dependent lung
B. 10cm H2O CPAP to the non-dependent lung
C. 5cm H2O PEEP to the dependent lung
D. 5cm H2O CPAP to the non-dependent and 5cm H2O PEEP to the dependent lung
E. intermittent re-inflation to the non-dependent lung
ANSWER C
OLV used for almost all thoracic operations : lung, esophageal, aortic or mediastinal surgery, to improve surgical access.
Although one lung is ventilated, both lung are perfused. Resulting in
-trans pulmonary shunting
-impairment of oxygenation
-hypoxemia
Treatment of hyoxemia during OLV
- Increasing FiO2
-effective in immediately treating
-will not improve with shunt fractions > 40% - Check position of DLT (using FOB)
- ensure adequate CO, reduce volatile to <1MAC
- Apply recruitment maneouvre
- Apply 5cm H2O PEEP to dependent lung
- Apply 1-2cm H2O CPAP to non-dependent lung after recruitment maneouvre
- Intermittent Reinflation
- Partial ventilation techniques including oxygen insufflation, HFJV, mechanical obstruction of blood flow to non-dependent lung
- clamp pulmonary artery of non ventilated lung (rare)
The patient most likely to desaturate significantly during one lung anaesthesia is one who is having
A. a left sided thoracotomy, has reasonable PaO2 values during two-lung ventilation, but poor pre-operative spirometry
B. a right-sided thoracotomy, has relatively poor PaO2 values during two-lung ventilation but good pre-operative spirometry
C. a left-sided thoracotomy and has diminished perfusion but not ventilation to the operative lung on a V/Q scan
D. a right-sided thoracotomy, has relatively poor PaO2 values during two-lung ventilation and poor pre-operative spirometry
ANSWER B
OLV used for almost all thoracic operations : lung, esophageal, aortic or mediastinal surgery, to improve surgical access.
Although one lung is ventilated, both lung are perfused. Resulting in
-trans pulmonary shunting
-impairment of oxygenation
-hypoxemia
Prediction of Hypoxemia during OLV
1. Side of operation
-size R>L
-therefore operation on left lung (ei larger right lung is dependent and ventilated) results in better oxygenation
-FiO2 1, results in 280mmHg for left sided operation and 170mmHg for right sided operations
- Lung Function Abnormalities
a. airway obstruction with low FEV1 results in better oxygenation during OLV, perhaps due to autoPEEP resulting in reduced atelecatasis and improving oxygenation
b. low PaO2 on pre-operative ABG is a predictor for hypoxemia during OLV. - Distribution of perfusion - less perfusion of non ventilated lung and more to ventilated lung results in high PaO2 during OLV
a. large tumors in non ventilated lung = better PaO2 as they present for lobectomies or pneumonectomies
b. gravity, if ventilated lung is dependent = better PaO2; in one study in COAD pts, FiO2 1.0 resulted in PaO2 300mmHg in supine versus PaO2 490mmHg in lateral
Complications, which usually present early following pneumonectomy, include all of the following EXCEPT
A. Broncho-pleural fistula
B. Respiratory failure
C. Right heart failure
D. Right to left shunt
E. Supraventricular arrhythmia
ANSWER A
Pneumonectomy is the surgical removal of an entire lung
-mainly for bronchogenic carcinoma in main stem bronchus
-rarely for pulmonary metastases, pulmonary tuberculos, fungal infections and broncheicatasis, traumatic lung injury, congential disease and bronchial obstruction
IMMEDIATE
Contralateral pneumonthorax
Sputum retention
Prolonged air leakage
Haemorrage
Phrenic nerve injury
R-L shunt through PFO due to increase in PA pressures
Acute respiratory insufficiency
EARLY
A. Respiratory :
-ARDS/post pneumonectomy pulmonary oedma - treatment is supportive, mortality>50%
-hemothorax, chylothorax
-empyema
B. Cardiac
-arrthymias AF
-AMI
-PE
-Cardiac herniation
LATE
A. postpneumonectomy syndrome
-extrinsic compression of distal trachea and mainstem bronchus due to shifting of the mediastinum
-progressive dyspnea, cough, inspiratroy stridor, recurrent pneumonia after 6 months of surgery
-treatment surgical repositioning of mediastinum
B. Bronchopleural fistula
-1.5-4.5%, mortality of 30-70%
-assocaited with empyema
C. Esophagopleural fistula
The most appropriate investigation to diagnose Type A aortic dissections in potentially unstable patients is
A. angiography
B. CAT scan
C. magnetic resonance imaging (MRI)
D. transoesophageal echocardiography
E. transthoracic echocardiography
ANSWER D
Patient is potentially unstable.
A patient is scheduled for emergency coronary artery bypass surgery (CABG) 2 hours after receiving tirofiban (Aggrastat) during coronary angiography and an unsuccessful coronary stenting procedure. The most useful strategy to treat or prevent excessive perioperative bleeding is:
A. administration of concentrated Factor VIII
B. administration of cryoprecipitate
C. delaying surgery another 2 hours
D. haemofiltration during cardiopulmonary bypass
E. platelet transfusion
Sign in
Flashcards » FINALS MCQ CARDIOTHORACIC
Finals Mcq Cardiothoracic
by hh8118@gmail.com, Apr. 2011Subjects: 111 2 anzca cardiothoracic finals mcq-facts partFavoriteAdd to folderFlag
Flashcards
Related Essays
Epidural Anesthesia
Patients receiving a thoracotomy often have an extensive list of associated co-morbidities that need to be taken into consideration when planning an anesthet…
Summary: Nutrition After Transplantation
The study was a cross-over design between two groups. One group underwent CPT the first half of their day on post op day three, and they underwent HFCWO for …
The Effect Of Cardiac Surgery On The Human Respiratory System
Introduction Heart and lung work hand to hand daily, nonstop until we die. Some people may have experienced heart surgery because of many reasons. Some reas…
Rapid Sequence Induction Process
One potential side effect of delivering high levels of oxygen to the apneic patient is the resultant washout of nitrogen from the respiratory system, which…
Fib Case Study
My management of this patient included: • Administration of oxygen via a 100% non-rebreather mask to alleviated the effects of hypoxemia. • The Paramedic pr…
Pneumothorax: The Cause Of Distress
because there was no precise cause or preventive measure, the doctor had a negative opinion about surgery. Although the probability of a recurrence of pneumo…
Respiratory Therapy Essay
Respiratory therapy evaluated the patient’s response to the oxygen that was prescribed to help the patient breathe easier. Respiratory therapy recommended t…
Gastroparesis Research Paper
This is a great treatment because it has a high success rate. However, it’s very taxing on the patient and the patient may need to a ventilator during the
Giovanni’s Hypervolemia Case Study
One collaborative intervention applicable for his impaired oxygenation includes the use of CPAP to ensure that he is receiving enough oxygen supply. As ident…
Essay On Tracheostomy
In the case of an obstruction, the trachea becomes less open due to the formation of essentially scar tissue, which can cause a difficulty in breathing even …
CARD RANGE TO STUDY
1
through
47
Click or Press Spacebar to Begin »
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
Share Print Export Clone
47 Cards in this Set
ANZCA July 2007 Q118
A 40-year-old man with Marfan’s syndrome is to undergo thoraco-abdominal aortic reconstruction for chronic aortic dissection. An intrathecal catheter is inserted. The purpose for this is to
A. allow drainage of cerebrospinal fluid (CSF)
B. allow intrathecal administration of metabolic substrates
C. allow intrathecal administration of neuroprotective drugs
D. cool the spinal cord
E. facilitate spinal cord function monitoring
ANSWER A
The blood supply to the spinal cord and the kidney is reduced by 84-90% after cross-clamping the descending thoracic aorta at the level of the left subclavian artery.
Elective thoracic aortic repair has a 0.4% incidence of permanent cord injury, but emergency repair of an aortic rupture has a 24-40% incidence.
The incidence of perioperative spinal cord injury is increased by:
* cross-clamp times of greater than 30 mins, as the warm ischaemia time for the cord is 20-30 mins;
* high level of thoracic cross-clamping;
* emergency surgery (eg acute dissection or rupture when there are no collaterals);
* greater longitudinal extent of the aneurysm;
* patient age greater than 70 years; and,
* no prophylactic measures undertaken
Intraoperative methods of spinal cord protection include
-swift surgery, with identification and preservation of vital cord supply blood vessels
-cross-clamp times of less than 30 minutes
-Lumbar CSF drainage to increase the spinal cord perfusion pressure
-mild hypothermia (34-35 °C), which decreases the cerebral metabolic rate for oxygen by 20%
-Preliminary reports suggest intrathecal papaverine may provide some cord protection, as a result of its arteriolar vasodilating, calcium channel blocking and oxygen free radical scavenging properties
-Spinal cord somatosensory evoked potential (SSEP) monitoring has been recommended to detect spinal cord ischaemia ,
Shunts to improve perfusion distal to the cross-clamp have not influenced the incidence of paraplegia, due to the high resistance to retrograde flow in the ASA above the artery of Adamkiewicz inflow.
Describe the effect on ventilation/oxygenation with these misplaced DLT.
AL = correct positioning of the a left sided DLT
BL = L DLT too far in, resulting in ventilation of left lower or left upper lobe through the bronchial lumen, hypoxemia
CL = L DLT no for in enough, resulting in partial obstruction when ventilating through the tracheal lumen
DL = intubation of operative lung, resulting in severe hypoxemia when ventilating through bronchial lumen, but improvement during ventilating through tracheal lumen.
BR = introduced to far, resulting in ventilation of right middle and right lower lobe only, right upper is not ventilated, resulting in hypoxemia
AT08c [Apr97] [Jul98] [2001-Apr] Q50, [2001-Aug] Q31, [2003-Apr] Q3, [2003-Aug] Q54, [2005-Apr] Q38, [Jul05] [Mar06]
The most appropriate method for improving oxygenation during one lung anaesthesia, after institution of an FiO2 of 1.0, is application of
A. 5cm H2O CPAP to the non-dependent lung
B. 10cm H2O CPAP to the non-dependent lung
C. 5cm H2O PEEP to the dependent lung
D. 5cm H2O CPAP to the non-dependent and 5cm H2O PEEP to the dependent lung
E. intermittent re-inflation to the non-dependent lung
ANSWER C
OLV used for almost all thoracic operations : lung, esophageal, aortic or mediastinal surgery, to improve surgical access.
Although one lung is ventilated, both lung are perfused. Resulting in
-trans pulmonary shunting
-impairment of oxygenation
-hypoxemia
Treatment of hyoxemia during OLV
- Increasing FiO2
-effective in immediately treating
-will not improve with shunt fractions > 40% - Check position of DLT (using FOB)
- ensure adequate CO, reduce volatile to <1MAC
- Apply recruitment maneouvre
- Apply 5cm H2O PEEP to dependent lung
- Apply 1-2cm H2O CPAP to non-dependent lung after recruitment maneouvre
- Intermittent Reinflation
- Partial ventilation techniques including oxygen insufflation, HFJV, mechanical obstruction of blood flow to non-dependent lung
- clamp pulmonary artery of non ventilated lung (rare)
AT15 [Apr97] [Apr98] [Jul98] [Apr99] [Aug99] [2003-Apr] Q66, [2003-Aug] Q30, [Mar06] ANZCA version
Q42
The patient most likely to desaturate significantly during one lung anaesthesia is one who is having
A. a left sided thoracotomy, has reasonable PaO2 values during two-lung ventilation, but poor pre-operative spirometry
B. a right-sided thoracotomy, has relatively poor PaO2 values during two-lung ventilation but good pre-operative spirometry
C. a left-sided thoracotomy and has diminished perfusion but not ventilation to the operative lung on a V/Q scan
D. a right-sided thoracotomy, has relatively poor PaO2 values during two-lung ventilation and poor pre-operative spirometry
ANSWER B
OLV used for almost all thoracic operations : lung, esophageal, aortic or mediastinal surgery, to improve surgical access.
Although one lung is ventilated, both lung are perfused. Resulting in
-trans pulmonary shunting
-impairment of oxygenation
-hypoxemia
Prediction of Hypoxemia during OLV
1. Side of operation
-size R>L
-therefore operation on left lung (ei larger right lung is dependent and ventilated) results in better oxygenation
-FiO2 1, results in 280mmHg for left sided operation and 170mmHg for right sided operations
- Lung Function Abnormalities
a. airway obstruction with low FEV1 results in better oxygenation during OLV, perhaps due to autoPEEP resulting in reduced atelecatasis and improving oxygenation
b. low PaO2 on pre-operative ABG is a predictor for hypoxemia during OLV. - Distribution of perfusion - less perfusion of non ventilated lung and more to ventilated lung results in high PaO2 during OLV
a. large tumors in non ventilated lung = better PaO2 as they present for lobectomies or pneumonectomies
b. gravity, if ventilated lung is dependent = better PaO2; in one study in COAD pts, FiO2 1.0 resulted in PaO2 300mmHg in supine versus PaO2 490mmHg in lateral
AT23 [2003-Apr] Q105, [2003-Aug] Q86, [2004-Aug] Q95, [2005-Apr] Q86, [Jul05] [Mar06] ANZCA version
Q106
Complications, which usually present early following pneumonectomy, include all of the following EXCEPT
A. Broncho-pleural fistula
B. Respiratory failure
C. Right heart failure
D. Right to left shunt
E. Supraventricular arrhythmia
ANSWER A
Pneumonectomy is the surgical removal of an entire lung
-mainly for bronchogenic carcinoma in main stem bronchus
-rarely for pulmonary metastases, pulmonary tuberculos, fungal infections and broncheicatasis, traumatic lung injury, congential disease and bronchial obstruction
IMMEDIATE
Contralateral pneumonthorax
Sputum retention
Prolonged air leakage
Haemorrage
Phrenic nerve injury
R-L shunt through PFO due to increase in PA pressures
Acute respiratory insufficiency
EARLY
A. Respiratory :
-ARDS/post pneumonectomy pulmonary oedma - treatment is supportive, mortality>50%
-hemothorax, chylothorax
-empyema
B. Cardiac
-arrthymias AF
-AMI
-PE
-Cardiac herniation
LATE
A. postpneumonectomy syndrome
-extrinsic compression of distal trachea and mainstem bronchus due to shifting of the mediastinum
-progressive dyspnea, cough, inspiratroy stridor, recurrent pneumonia after 6 months of surgery
-treatment surgical repositioning of mediastinum
B. Bronchopleural fistula
-1.5-4.5%, mortality of 30-70%
-assocaited with empyema
C. Esophagopleural fistula
SC13 [2003-Apr] Q89, [2003-Aug] Q58, [Jul05] [Mar06]
The most appropriate investigation to diagnose Type A aortic dissections in potentially unstable patients is
A. angiography
B. CAT scan
C. magnetic resonance imaging (MRI)
D. transoesophageal echocardiography
E. transthoracic echocardiography
ANSWER D
Patient is potentially unstable.
SC26 [Mar06] [Jul06] ANZCA version
Q147
A patient is scheduled for emergency coronary artery bypass surgery (CABG) 2 hours after receiving tirofiban (Aggrastat) during coronary angiography and an unsuccessful coronary stenting procedure. The most useful strategy to treat or prevent excessive perioperative bleeding is:
A. administration of concentrated Factor VIII
B. administration of cryoprecipitate
C. delaying surgery another 2 hours
D. haemofiltration during cardiopulmonary bypass
E. platelet transfusion
ANSWER E
Tibrofiban (Aggrastat) is an antiplatelet agent
-Gycoprotein IIb/IIIa inhibitor (block the final common pathway of platelet aggregation)
-does not block platelet adhesion, screction of platelet products, inflammatory effects or thrombin activation
Used in the management of STEMI or unstable angina in patients awaiting PCI
Parental dosage
-2.5mg in 250ml NS (50mcg/ml)
-Loading dose 0.4mcg/kg/min for 30 minutes
-Maintenance of 0.1mcg/kg/min for up to 72 hours
-Infusion should continue through PCI and 12-24 hours after
-Stop for 8 hours prior to CABGs
Rapid onset and short duration of action
-coagulation returns to normal after 4-8 hours of ceassation
-half life 2 hours
Contraindications
-hypersensitivity
-active bleeding
-history of ICH, AV malformation, aneurysm
-thrombocytopenia induced by tibrofiban in past
-CVA in last 30 days
-recent surgery
-suggestive funding of aortic dissection
Complications
-major bleeding : ICH, retroperiotoneal, pulmonary, spinal-epidural haematoma
-anaphylaxis
-thrombocytopenia
During elective major vascular surgery the best way to reduce the risk of acute renal failure is to maintain a normal
A. central venous pressure
B. mean arterial blood pressure
C. renal blood flow
D. systemic vascular resistance
E. urine output
ANSWER C
Describe the effects of the level of aortic occlusion on changes in CVS variables
Proximal decending Aox
MAP : increased 35%
CVP : increased 56%
Mean PAP : increased 43%
PWCP : increased 90% (due to blood volume distribution and increased afterload)
CI : decreased 30%
HR : no change
LV stroke work : no change
Supracaeliac AoX
MAP : increased 54%
PCWP : increased 38%
EF : decreased by 38%
LV end-systolic area : increased 69%
LV end-diastolic area : increased 28%
Wall motion changes in 92%
New AMI : 8%
Suprarenal AoX cause similar but smaller CVS changes.
Infrarnal AoX associated with only minimal change and no wall motion abnormalities
Infra-renal aortic cross-clamping usually results in
A. decreased cardiac contractility
B. decreased coronary blood flow
C. decreased renal blood flow
D. minimal change in cardiac output
E. increased heart rate
ANSWER D
Systemic haemodynamic response to aortic cross-clamping
-preload does not always increase
-infra-renal aortic cross-clamping blood volume shifts into splanchnic circulation and preload does not increase
MAP : no change
PAP : no change
End-diastolic area : increase 9%
End-systolic area : increases 11%
Abnormal wall motion : 0
New AMI : 0
Describe the non-cardiovascular responses to AoX.
ANZCA July 2007 Q118
A 40-year-old man with Marfan’s syndrome is to undergo thoraco-abdominal aortic reconstruction for chronic aortic dissection. An intrathecal catheter is inserted. The purpose for this is to
A. allow drainage of cerebrospinal fluid (CSF)
B. allow intrathecal administration of metabolic substrates
C. allow intrathecal administration of neuroprotective drugs
D. cool the spinal cord
E. facilitate spinal cord function monitoring
ANSWER A
The blood supply to the spinal cord and the kidney is reduced by 84-90% after cross-clamping the descending thoracic aorta at the level of the left subclavian artery.
Elective thoracic aortic repair has a 0.4% incidence of permanent cord injury, but emergency repair of an aortic rupture has a 24-40% incidence.
The incidence of perioperative spinal cord injury is increased by:
* cross-clamp times of greater than 30 mins, as the warm ischaemia time for the cord is 20-30 mins;
* high level of thoracic cross-clamping;
* emergency surgery (eg acute dissection or rupture when there are no collaterals);
* greater longitudinal extent of the aneurysm;
* patient age greater than 70 years; and,
* no prophylactic measures undertaken
Intraoperative methods of spinal cord protection include
-swift surgery, with identification and preservation of vital cord supply blood vessels
-cross-clamp times of less than 30 minutes
-Lumbar CSF drainage to increase the spinal cord perfusion pressure
-mild hypothermia (34-35 °C), which decreases the cerebral metabolic rate for oxygen by 20%
-Preliminary reports suggest intrathecal papaverine may provide some cord protection, as a result of its arteriolar vasodilating, calcium channel blocking and oxygen free radical scavenging properties
-Spinal cord somatosensory evoked potential (SSEP) monitoring has been recommended to detect spinal cord ischaemia ,
Shunts to improve perfusion distal to the cross-clamp have not influenced the incidence of paraplegia, due to the high resistance to retrograde flow in the ASA above the artery of Adamkiewicz inflow.
Describe the effect on ventilation/oxygenation with these misplaced DLT.
AL = correct positioning of the a left sided DLT
BL = L DLT too far in, resulting in ventilation of left lower or left upper lobe through the bronchial lumen, hypoxemia
CL = L DLT no for in enough, resulting in partial obstruction when ventilating through the tracheal lumen
DL = intubation of operative lung, resulting in severe hypoxemia when ventilating through bronchial lumen, but improvement during ventilating through tracheal lumen.
BR = introduced to far, resulting in ventilation of right middle and right lower lobe only, right upper is not ventilated, resulting in hypoxemia
AT08c [Apr97] [Jul98] [2001-Apr] Q50, [2001-Aug] Q31, [2003-Apr] Q3, [2003-Aug] Q54, [2005-Apr] Q38, [Jul05] [Mar06]
The most appropriate method for improving oxygenation during one lung anaesthesia, after institution of an FiO2 of 1.0, is application of
A. 5cm H2O CPAP to the non-dependent lung
B. 10cm H2O CPAP to the non-dependent lung
C. 5cm H2O PEEP to the dependent lung
D. 5cm H2O CPAP to the non-dependent and 5cm H2O PEEP to the dependent lung
E. intermittent re-inflation to the non-dependent lung
ANSWER C
OLV used for almost all thoracic operations : lung, esophageal, aortic or mediastinal surgery, to improve surgical access.
Although one lung is ventilated, both lung are perfused. Resulting in
-trans pulmonary shunting
-impairment of oxygenation
-hypoxemia
Treatment of hyoxemia during OLV
- Increasing FiO2
-effective in immediately treating
-will not improve with shunt fractions > 40% - Check position of DLT (using FOB)
- ensure adequate CO, reduce volatile to <1MAC
- Apply recruitment maneouvre
- Apply 5cm H2O PEEP to dependent lung
- Apply 1-2cm H2O CPAP to non-dependent lung after recruitment maneouvre
- Intermittent Reinflation
- Partial ventilation techniques including oxygen insufflation, HFJV, mechanical obstruction of blood flow to non-dependent lung
- clamp pulmonary artery of non ventilated lung (rare)
AT15 [Apr97] [Apr98] [Jul98] [Apr99] [Aug99] [2003-Apr] Q66, [2003-Aug] Q30, [Mar06] ANZCA version
Q42
The patient most likely to desaturate significantly during one lung anaesthesia is one who is having
A. a left sided thoracotomy, has reasonable PaO2 values during two-lung ventilation, but poor pre-operative spirometry
B. a right-sided thoracotomy, has relatively poor PaO2 values during two-lung ventilation but good pre-operative spirometry
C. a left-sided thoracotomy and has diminished perfusion but not ventilation to the operative lung on a V/Q scan
D. a right-sided thoracotomy, has relatively poor PaO2 values during two-lung ventilation and poor pre-operative spirometry
ANSWER B
OLV used for almost all thoracic operations : lung, esophageal, aortic or mediastinal surgery, to improve surgical access.
Although one lung is ventilated, both lung are perfused. Resulting in
-trans pulmonary shunting
-impairment of oxygenation
-hypoxemia
Prediction of Hypoxemia during OLV
1. Side of operation
-size R>L
-therefore operation on left lung (ei larger right lung is dependent and ventilated) results in better oxygenation
-FiO2 1, results in 280mmHg for left sided operation and 170mmHg for right sided operations
- Lung Function Abnormalities
a. airway obstruction with low FEV1 results in better oxygenation during OLV, perhaps due to autoPEEP resulting in reduced atelecatasis and improving oxygenation
b. low PaO2 on pre-operative ABG is a predictor for hypoxemia during OLV. - Distribution of perfusion - less perfusion of non ventilated lung and more to ventilated lung results in high PaO2 during OLV
a. large tumors in non ventilated lung = better PaO2 as they present for lobectomies or pneumonectomies
b. gravity, if ventilated lung is dependent = better PaO2; in one study in COAD pts, FiO2 1.0 resulted in PaO2 300mmHg in supine versus PaO2 490mmHg in lateral
AT23 [2003-Apr] Q105, [2003-Aug] Q86, [2004-Aug] Q95, [2005-Apr] Q86, [Jul05] [Mar06] ANZCA version
Q106
Complications, which usually present early following pneumonectomy, include all of the following EXCEPT
A. Broncho-pleural fistula
B. Respiratory failure
C. Right heart failure
D. Right to left shunt
E. Supraventricular arrhythmia
ANSWER A
Pneumonectomy is the surgical removal of an entire lung
-mainly for bronchogenic carcinoma in main stem bronchus
-rarely for pulmonary metastases, pulmonary tuberculos, fungal infections and broncheicatasis, traumatic lung injury, congential disease and bronchial obstruction
IMMEDIATE
Contralateral pneumonthorax
Sputum retention
Prolonged air leakage
Haemorrage
Phrenic nerve injury
R-L shunt through PFO due to increase in PA pressures
Acute respiratory insufficiency
EARLY
A. Respiratory :
-ARDS/post pneumonectomy pulmonary oedma - treatment is supportive, mortality>50%
-hemothorax, chylothorax
-empyema
B. Cardiac
-arrthymias AF
-AMI
-PE
-Cardiac herniation
LATE
A. postpneumonectomy syndrome
-extrinsic compression of distal trachea and mainstem bronchus due to shifting of the mediastinum
-progressive dyspnea, cough, inspiratroy stridor, recurrent pneumonia after 6 months of surgery
-treatment surgical repositioning of mediastinum
B. Bronchopleural fistula
-1.5-4.5%, mortality of 30-70%
-assocaited with empyema
C. Esophagopleural fistula
SC13 [2003-Apr] Q89, [2003-Aug] Q58, [Jul05] [Mar06]
The most appropriate investigation to diagnose Type A aortic dissections in potentially unstable patients is
A. angiography
B. CAT scan
C. magnetic resonance imaging (MRI)
D. transoesophageal echocardiography
E. transthoracic echocardiography
ANSWER D
Patient is potentially unstable.
SC26 [Mar06] [Jul06] ANZCA version
Q147
A patient is scheduled for emergency coronary artery bypass surgery (CABG) 2 hours after receiving tirofiban (Aggrastat) during coronary angiography and an unsuccessful coronary stenting procedure. The most useful strategy to treat or prevent excessive perioperative bleeding is:
A. administration of concentrated Factor VIII
B. administration of cryoprecipitate
C. delaying surgery another 2 hours
D. haemofiltration during cardiopulmonary bypass
E. platelet transfusion
ANSWER E
Tibrofiban (Aggrastat) is an antiplatelet agent
-Gycoprotein IIb/IIIa inhibitor (block the final common pathway of platelet aggregation)
-does not block platelet adhesion, screction of platelet products, inflammatory effects or thrombin activation
Used in the management of STEMI or unstable angina in patients awaiting PCI
Parental dosage
-2.5mg in 250ml NS (50mcg/ml)
-Loading dose 0.4mcg/kg/min for 30 minutes
-Maintenance of 0.1mcg/kg/min for up to 72 hours
-Infusion should continue through PCI and 12-24 hours after
-Stop for 8 hours prior to CABGs
Rapid onset and short duration of action
-coagulation returns to normal after 4-8 hours of ceassation
-half life 2 hours
Contraindications
-hypersensitivity
-active bleeding
-history of ICH, AV malformation, aneurysm
-thrombocytopenia induced by tibrofiban in past
-CVA in last 30 days
-recent surgery
-suggestive funding of aortic dissection
Complications
-major bleeding : ICH, retroperiotoneal, pulmonary, spinal-epidural haematoma
-anaphylaxis
-thrombocytopenia
ANZCA March 2006 Q71.
During elective major vascular surgery the best way to reduce the risk of acute renal failure is to maintain a normal
A. central venous pressure
B. mean arterial blood pressure
C. renal blood flow
D. systemic vascular resistance
E. urine output
ANSWER C
Describe the effects of the level of aortic occlusion on changes in CVS variables
Proximal decending Aox
MAP : increased 35%
CVP : increased 56%
Mean PAP : increased 43%
PWCP : increased 90% (due to blood volume distribution and increased afterload)
CI : decreased 30%
HR : no change
LV stroke work : no change
Supracaeliac AoX
MAP : increased 54%
PCWP : increased 38%
EF : decreased by 38%
LV end-systolic area : increased 69%
LV end-diastolic area : increased 28%
Wall motion changes in 92%
New AMI : 8%
Suprarenal AoX cause similar but smaller CVS changes.
Infrarnal AoX associated with only minimal change and no wall motion abnormalities
Describe the cardiovascular response to aortic unclamping.
Systemic hemodynamic response to aortic unclamping. AoX = aortic cross-clamping; Cven venous capacitance; R art = arterial resistance; Rpv = pulmonary vascular resistance; [arrow up] and [arrow down] = increase and decrease, respectively.
G. Response to unclamping
-SVR and MAP decrease by 70-80%
-CO may increase, decrease or remain unchanged
-LV end-diastolic pressure decreases
-myocardial blood flow increases
-flow through the terminal aorta and femoral arteries increases
-reactive hyperemia due to both metabolic and hormonal responses, lasting 15 minutes
-washout distal to the AoX occurs returning vaso and cardio-depressant compounds
-blood redistribution to vessels distal to AoX decrease venous return, cardiac output and MAP (hypovolemia)
To minimize cardiovascular responses
1. Gradual release of aortic clamp and reapplication : slow down the washout
2. Volume replacement
3. Sodium bicarbonate adminstration
SZ18 [2004-Aug] Q147, [2005-Apr] Q76, [Mar06] ANZCA version
Q148
Infra-renal aortic cross-clamping usually results in
A. decreased cardiac contractility
B. decreased coronary blood flow
C. decreased renal blood flow
D. minimal change in cardiac output
E. increased heart rate
ANSWER D
Systemic haemodynamic response to aortic cross-clamping
-preload does not always increase
-infra-renal aortic cross-clamping blood volume shifts into splanchnic circulation and preload does not increase
MAP : no change
PAP : no change
End-diastolic area : increase 9%
End-systolic area : increases 11%
Abnormal wall motion : 0
New AMI : 0
Describe the cardiovascular response to aortic clamping.
A. Primary variables
-MAP increases
-SVR increases
-HR no change
-CO generally decreases, but increases in thoracic AoX
B. Afterload, Preload and Blood volume redistribution
-impedance to aortic flow : increased afterload in all Aox
-preload changes depends on level of Aox
-thoracic AoX : passive recoil and emptying of capacitance vessels (both splanchnic and lower limbs) into the systemic circulation results a marked increased in preload and therefore cardiac output
-CVP, PWCP, LV end-diastolic area all increase depending on the level of AoX
-this effect is abolished if the IVC is clamped or blood is removed from the system (ei. phebotomy)
-differences in CVS response after AoX at difference levels is explained by different degrees and patterns of blood volume distribution
-infracaelic Aox maintains the splanchnic circulation, blood is redistributed to these capacitance vessels and preload is not significantly changed
-however this response depends on the sympathetic discharge to the splanchnic system, activation of the SNS may decrease venous capacitance resulting in increased preload
- Metabolism
-reduced total body oxygen consumption
-thoracic AoX results in 55% reduction
-anaerobic metabolism in tissues below Aox
-reduced O2 uptake in tissues above AoX
-proximal hypervolemia, vasodilation and increase in flow through these tissue may result in microcirculatory disturbances which jeopardize oxygen exchange
-activation of SNS constricts arterioles and decrease capillary flow results in shunting of blood away from tissue beds (possibly similar to hyperdynamic state in sepsis)
-Increase in mixed venous O2 sat (SVO2)
D. Coronary blood flow and myocardial contractility
-Aox increases both preload and afterload, leading to an increase in myocardial oxygen demand
-autoregulation : an increase in demand is met by an increase in supply by increasing coronary blood flow
-thoracic AoX 65% increase in CBF
-myocardial contractility is initially increased due SNS stimulation and physiological repsonse to increases in preload and afterload
-gradual decrease due to accumulation of cardiodepressant metabolites (H+, K+, adenosine) from ischaemic tissues
E. Duration of AoX
-with increased duration, SVR increases, while CO decreases
-possibly explained by capillary leak and reduction in circulating blood volume
-also release of cardiodepressant metabolites
F. Haemodynamic response distal to AoX
-aortic pressure decreases
-distal pressure is directly dependent on proximal aortic pressure through existing collateral vessels, therefore, proximal and distal aortic pressures must be maintained as great as the heart can withstand, otherwise a temporary shunt inserted.
-a decrease in arterial and subsequently, capillary pressure below AoX results in absorption of interstitial fluid (Starling’s forces)
-this mat increase venous return and circulating volume above AoX
Describe the non-cardiovascular responses to AoX.
A. Hormoral changes
1. Metabolic Lactic Acidosis
-degree of acidosis depends on degree of disease, time of AoX, level of AoX, collateral vessels
- RAS
-activation of renin-angiotension system
-suprarenal AoX results in reduced perfusion pressure in the afferent arterioles of the kidney
-infrarenal AoX also increases RAS but the mechanism is less clear
-?activation of SNS
-?effect of prostaglandins - Catecholamines and SNS
-thoracic AoX is consistently associated with large increases in adr and norad concentration
-lower levels are associated with smaller increases in blood catechols
-adr increases during clamping
-norad increases after unclamping
-mechanism s complex and multifactoral : hypotension, shock, direct ischemic excitation of spinal cord and adrenal medulla. - Free oxygen radicals
-hypoxic conditions, the metabolism of adenosine triphosphate produces adenosine, hypoxanthine, xanthine oxidase, purines, and oxygen free radicals. - Prostaglandins
-increase during and after clamping
-PGE, TXA A2 and TXA B2
-increased production of vasodilating prostaglandins during aortic cross-clamping
-vasoconstricting prostaglandins during unclamping - Platelets and neutrophils
-sequestration in lung
-attributable to anaerobic metabolic products and microaggregates released from the ischemic tissues
-Lymphocyte count decreases, whereas leukocyte and neutrophil counts increase, after unclamping of the aorta - Complement activation
-concentrations of the anaphylatoxins C3a and C5a increased
-Epidural anesthesia virtually prevented an increase in C5a and significantly modified an increase in C3a
-mechanism is unclear - Other
-increase in IL-1 and IL-6 due to increased sheer stress on endothelium
-increase in TNF due to ischemia
B. Respiratory
-increase in PVR especially during thoracic AoX
-mainly due to blood redistribution
-neutrophil sequestration and accumulation of microaggregates results in pulmonary edema
-can progress to ARDS which carries a high mortality
C. Kidneys
-infrarenal 5% incidence of renal failure requiring haemodialysis, associated large increase in renal vascular resistence and 30% decrease in renal BF
-suprarenal 15%
-thoracic 50% incidence of RF, severe 85-95% decrease in renal BF, GFR and UO
-renal failure always results from ATN
-ischemia-reperfusion insult
D. Spinal Cord
-incidence of paraplegia is 0.4-40%
-depends on urgency of operation, the presence of aortic dissection, hypotension, the age of the patient, and the duration and level of the aortic cross-clamping (<30min prefered)
-Approximately half of the patients with initial paraplegia make no neurologic recovery
-mechanism is due to decrease in spinal perfusion pressure
-survival depends on collaterial arteries and communications : Artery of Adamkewicz
-spinal perfusion pressure is made worse by blood volume shifts, which increase cerebral blood volume = increase in ICP
-therapeutic role of lumbar spinal drain to reduce CSF volume
-cooling
E. Abdominal viscera
-The reported incidence of visceral ischemia varies from 1-10%, with mortality exceeding 50%.
-The most common site of ischemia is the left part of the colon.
-Hypovolemia, thrombosis, cardiac insufficiency, and microembolism should also be considered in the development of bowel ischemia
Describe the non-cardiovascular responses to AoX.
ANZCA July 2007 Q118
A 40-year-old man with Marfan’s syndrome is to undergo thoraco-abdominal aortic reconstruction for chronic aortic dissection. An intrathecal catheter is inserted. The purpose for this is to
A. allow drainage of cerebrospinal fluid (CSF)
B. allow intrathecal administration of metabolic substrates
C. allow intrathecal administration of neuroprotective drugs
D. cool the spinal cord
E. facilitate spinal cord function monitoring
ANSWER A
The blood supply to the spinal cord and the kidney is reduced by 84-90% after cross-clamping the descending thoracic aorta at the level of the left subclavian artery.
Elective thoracic aortic repair has a 0.4% incidence of permanent cord injury, but emergency repair of an aortic rupture has a 24-40% incidence.
The incidence of perioperative spinal cord injury is increased by:
* cross-clamp times of greater than 30 mins, as the warm ischaemia time for the cord is 20-30 mins;
* high level of thoracic cross-clamping;
* emergency surgery (eg acute dissection or rupture when there are no collaterals);
* greater longitudinal extent of the aneurysm;
* patient age greater than 70 years; and,
* no prophylactic measures undertaken
Intraoperative methods of spinal cord protection include
-swift surgery, with identification and preservation of vital cord supply blood vessels
-cross-clamp times of less than 30 minutes
-Lumbar CSF drainage to increase the spinal cord perfusion pressure
-mild hypothermia (34-35 °C), which decreases the cerebral metabolic rate for oxygen by 20%
-Preliminary reports suggest intrathecal papaverine may provide some cord protection, as a result of its arteriolar vasodilating, calcium channel blocking and oxygen free radical scavenging properties
-Spinal cord somatosensory evoked potential (SSEP) monitoring has been recommended to detect spinal cord ischaemia ,
Shunts to improve perfusion distal to the cross-clamp have not influenced the incidence of paraplegia, due to the high resistance to retrograde flow in the ASA above the artery of Adamkiewicz inflow.
Describe the effect on ventilation/oxygenation with these misplaced DLT.
AL = correct positioning of the a left sided DLT
BL = L DLT too far in, resulting in ventilation of left lower or left upper lobe through the bronchial lumen, hypoxemia
CL = L DLT no for in enough, resulting in partial obstruction when ventilating through the tracheal lumen
DL = intubation of operative lung, resulting in severe hypoxemia when ventilating through bronchial lumen, but improvement during ventilating through tracheal lumen.
BR = introduced to far, resulting in ventilation of right middle and right lower lobe only, right upper is not ventilated, resulting in hypoxemia
AT08c [Apr97] [Jul98] [2001-Apr] Q50, [2001-Aug] Q31, [2003-Apr] Q3, [2003-Aug] Q54, [2005-Apr] Q38, [Jul05] [Mar06]
The most appropriate method for improving oxygenation during one lung anaesthesia, after institution of an FiO2 of 1.0, is application of
A. 5cm H2O CPAP to the non-dependent lung
B. 10cm H2O CPAP to the non-dependent lung
C. 5cm H2O PEEP to the dependent lung
D. 5cm H2O CPAP to the non-dependent and 5cm H2O PEEP to the dependent lung
E. intermittent re-inflation to the non-dependent lung
ANSWER C
OLV used for almost all thoracic operations : lung, esophageal, aortic or mediastinal surgery, to improve surgical access.
Although one lung is ventilated, both lung are perfused. Resulting in
-trans pulmonary shunting
-impairment of oxygenation
-hypoxemia
Treatment of hyoxemia during OLV
- Increasing FiO2
-effective in immediately treating
-will not improve with shunt fractions > 40% - Check position of DLT (using FOB)
- ensure adequate CO, reduce volatile to <1MAC
- Apply recruitment maneouvre
- Apply 5cm H2O PEEP to dependent lung
- Apply 1-2cm H2O CPAP to non-dependent lung after recruitment maneouvre
- Intermittent Reinflation
- Partial ventilation techniques including oxygen insufflation, HFJV, mechanical obstruction of blood flow to non-dependent lung
- clamp pulmonary artery of non ventilated lung (rare)
AT15 [Apr97] [Apr98] [Jul98] [Apr99] [Aug99] [2003-Apr] Q66, [2003-Aug] Q30, [Mar06] ANZCA version
Q42
The patient most likely to desaturate significantly during one lung anaesthesia is one who is having
A. a left sided thoracotomy, has reasonable PaO2 values during two-lung ventilation, but poor pre-operative spirometry
B. a right-sided thoracotomy, has relatively poor PaO2 values during two-lung ventilation but good pre-operative spirometry
C. a left-sided thoracotomy and has diminished perfusion but not ventilation to the operative lung on a V/Q scan
D. a right-sided thoracotomy, has relatively poor PaO2 values during two-lung ventilation and poor pre-operative spirometry
ANSWER B
OLV used for almost all thoracic operations : lung, esophageal, aortic or mediastinal surgery, to improve surgical access.
Although one lung is ventilated, both lung are perfused. Resulting in
-trans pulmonary shunting
-impairment of oxygenation
-hypoxemia
Prediction of Hypoxemia during OLV
1. Side of operation
-size R>L
-therefore operation on left lung (ei larger right lung is dependent and ventilated) results in better oxygenation
-FiO2 1, results in 280mmHg for left sided operation and 170mmHg for right sided operations
- Lung Function Abnormalities
a. airway obstruction with low FEV1 results in better oxygenation during OLV, perhaps due to autoPEEP resulting in reduced atelecatasis and improving oxygenation
b. low PaO2 on pre-operative ABG is a predictor for hypoxemia during OLV. - Distribution of perfusion - less perfusion of non ventilated lung and more to ventilated lung results in high PaO2 during OLV
a. large tumors in non ventilated lung = better PaO2 as they present for lobectomies or pneumonectomies
b. gravity, if ventilated lung is dependent = better PaO2; in one study in COAD pts, FiO2 1.0 resulted in PaO2 300mmHg in supine versus PaO2 490mmHg in lateral
AT23 [2003-Apr] Q105, [2003-Aug] Q86, [2004-Aug] Q95, [2005-Apr] Q86, [Jul05] [Mar06] ANZCA version
Q106
Complications, which usually present early following pneumonectomy, include all of the following EXCEPT
A. Broncho-pleural fistula
B. Respiratory failure
C. Right heart failure
D. Right to left shunt
E. Supraventricular arrhythmia
ANSWER A
Pneumonectomy is the surgical removal of an entire lung
-mainly for bronchogenic carcinoma in main stem bronchus
-rarely for pulmonary metastases, pulmonary tuberculos, fungal infections and broncheicatasis, traumatic lung injury, congential disease and bronchial obstruction
IMMEDIATE
Contralateral pneumonthorax
Sputum retention
Prolonged air leakage
Haemorrage
Phrenic nerve injury
R-L shunt through PFO due to increase in PA pressures
Acute respiratory insufficiency
EARLY
A. Respiratory :
-ARDS/post pneumonectomy pulmonary oedma - treatment is supportive, mortality>50%
-hemothorax, chylothorax
-empyema
B. Cardiac
-arrthymias AF
-AMI
-PE
-Cardiac herniation
LATE
A. postpneumonectomy syndrome
-extrinsic compression of distal trachea and mainstem bronchus due to shifting of the mediastinum
-progressive dyspnea, cough, inspiratroy stridor, recurrent pneumonia after 6 months of surgery
-treatment surgical repositioning of mediastinum
B. Bronchopleural fistula
-1.5-4.5%, mortality of 30-70%
-assocaited with empyema
C. Esophagopleural fistula
SC13 [2003-Apr] Q89, [2003-Aug] Q58, [Jul05] [Mar06]
The most appropriate investigation to diagnose Type A aortic dissections in potentially unstable patients is
A. angiography
B. CAT scan
C. magnetic resonance imaging (MRI)
D. transoesophageal echocardiography
E. transthoracic echocardiography
ANSWER D
Patient is potentially unstable.
SC26 [Mar06] [Jul06] ANZCA version
Q147
A patient is scheduled for emergency coronary artery bypass surgery (CABG) 2 hours after receiving tirofiban (Aggrastat) during coronary angiography and an unsuccessful coronary stenting procedure. The most useful strategy to treat or prevent excessive perioperative bleeding is:
A. administration of concentrated Factor VIII
B. administration of cryoprecipitate
C. delaying surgery another 2 hours
D. haemofiltration during cardiopulmonary bypass
E. platelet transfusion
ANSWER E
Tibrofiban (Aggrastat) is an antiplatelet agent
-Gycoprotein IIb/IIIa inhibitor (block the final common pathway of platelet aggregation)
-does not block platelet adhesion, screction of platelet products, inflammatory effects or thrombin activation
Used in the management of STEMI or unstable angina in patients awaiting PCI
Parental dosage
-2.5mg in 250ml NS (50mcg/ml)
-Loading dose 0.4mcg/kg/min for 30 minutes
-Maintenance of 0.1mcg/kg/min for up to 72 hours
-Infusion should continue through PCI and 12-24 hours after
-Stop for 8 hours prior to CABGs
Rapid onset and short duration of action
-coagulation returns to normal after 4-8 hours of ceassation
-half life 2 hours
Contraindications
-hypersensitivity
-active bleeding
-history of ICH, AV malformation, aneurysm
-thrombocytopenia induced by tibrofiban in past
-CVA in last 30 days
-recent surgery
-suggestive funding of aortic dissection
Complications
-major bleeding : ICH, retroperiotoneal, pulmonary, spinal-epidural haematoma
-anaphylaxis
-thrombocytopenia
ANZCA March 2006 Q71.
During elective major vascular surgery the best way to reduce the risk of acute renal failure is to maintain a normal
A. central venous pressure
B. mean arterial blood pressure
C. renal blood flow
D. systemic vascular resistance
E. urine output
ANSWER C
Describe the effects of the level of aortic occlusion on changes in CVS variables
Proximal decending Aox
MAP : increased 35%
CVP : increased 56%
Mean PAP : increased 43%
PWCP : increased 90% (due to blood volume distribution and increased afterload)
CI : decreased 30%
HR : no change
LV stroke work : no change
Supracaeliac AoX
MAP : increased 54%
PCWP : increased 38%
EF : decreased by 38%
LV end-systolic area : increased 69%
LV end-diastolic area : increased 28%
Wall motion changes in 92%
New AMI : 8%
Suprarenal AoX cause similar but smaller CVS changes.
Infrarnal AoX associated with only minimal change and no wall motion abnormalities
Describe the cardiovascular response to aortic unclamping.
Systemic hemodynamic response to aortic unclamping. AoX = aortic cross-clamping; Cven venous capacitance; R art = arterial resistance; Rpv = pulmonary vascular resistance; [arrow up] and [arrow down] = increase and decrease, respectively.
G. Response to unclamping
-SVR and MAP decrease by 70-80%
-CO may increase, decrease or remain unchanged
-LV end-diastolic pressure decreases
-myocardial blood flow increases
-flow through the terminal aorta and femoral arteries increases
-reactive hyperemia due to both metabolic and hormonal responses, lasting 15 minutes
-washout distal to the AoX occurs returning vaso and cardio-depressant compounds
-blood redistribution to vessels distal to AoX decrease venous return, cardiac output and MAP (hypovolemia)
To minimize cardiovascular responses
1. Gradual release of aortic clamp and reapplication : slow down the washout
2. Volume replacement
3. Sodium bicarbonate adminstration
SZ18 [2004-Aug] Q147, [2005-Apr] Q76, [Mar06] ANZCA version
Q148
Infra-renal aortic cross-clamping usually results in
A. decreased cardiac contractility
B. decreased coronary blood flow
C. decreased renal blood flow
D. minimal change in cardiac output
E. increased heart rate
ANSWER D
Systemic haemodynamic response to aortic cross-clamping
-preload does not always increase
-infra-renal aortic cross-clamping blood volume shifts into splanchnic circulation and preload does not increase
MAP : no change
PAP : no change
End-diastolic area : increase 9%
End-systolic area : increases 11%
Abnormal wall motion : 0
New AMI : 0
Describe the cardiovascular response to aortic clamping.
A. Primary variables
-MAP increases
-SVR increases
-HR no change
-CO generally decreases, but increases in thoracic AoX
B. Afterload, Preload and Blood volume redistribution
-impedance to aortic flow : increased afterload in all Aox
-preload changes depends on level of Aox
-thoracic AoX : passive recoil and emptying of capacitance vessels (both splanchnic and lower limbs) into the systemic circulation results a marked increased in preload and therefore cardiac output
-CVP, PWCP, LV end-diastolic area all increase depending on the level of AoX
-this effect is abolished if the IVC is clamped or blood is removed from the system (ei. phebotomy)
-differences in CVS response after AoX at difference levels is explained by different degrees and patterns of blood volume distribution
-infracaelic Aox maintains the splanchnic circulation, blood is redistributed to these capacitance vessels and preload is not significantly changed
-however this response depends on the sympathetic discharge to the splanchnic system, activation of the SNS may decrease venous capacitance resulting in increased preload
- Metabolism
-reduced total body oxygen consumption
-thoracic AoX results in 55% reduction
-anaerobic metabolism in tissues below Aox
-reduced O2 uptake in tissues above AoX
-proximal hypervolemia, vasodilation and increase in flow through these tissue may result in microcirculatory disturbances which jeopardize oxygen exchange
-activation of SNS constricts arterioles and decrease capillary flow results in shunting of blood away from tissue beds (possibly similar to hyperdynamic state in sepsis)
-Increase in mixed venous O2 sat (SVO2)
D. Coronary blood flow and myocardial contractility
-Aox increases both preload and afterload, leading to an increase in myocardial oxygen demand
-autoregulation : an increase in demand is met by an increase in supply by increasing coronary blood flow
-thoracic AoX 65% increase in CBF
-myocardial contractility is initially increased due SNS stimulation and physiological repsonse to increases in preload and afterload
-gradual decrease due to accumulation of cardiodepressant metabolites (H+, K+, adenosine) from ischaemic tissues
E. Duration of AoX
-with increased duration, SVR increases, while CO decreases
-possibly explained by capillary leak and reduction in circulating blood volume
-also release of cardiodepressant metabolites
F. Haemodynamic response distal to AoX
-aortic pressure decreases
-distal pressure is directly dependent on proximal aortic pressure through existing collateral vessels, therefore, proximal and distal aortic pressures must be maintained as great as the heart can withstand, otherwise a temporary shunt inserted.
-a decrease in arterial and subsequently, capillary pressure below AoX results in absorption of interstitial fluid (Starling’s forces)
-this mat increase venous return and circulating volume above AoX
Describe the non-cardiovascular responses to AoX.
A. Hormoral changes
1. Metabolic Lactic Acidosis
-degree of acidosis depends on degree of disease, time of AoX, level of AoX, collateral vessels
- RAS
-activation of renin-angiotension system
-suprarenal AoX results in reduced perfusion pressure in the afferent arterioles of the kidney
-infrarenal AoX also increases RAS but the mechanism is less clear
-?activation of SNS
-?effect of prostaglandins - Catecholamines and SNS
-thoracic AoX is consistently associated with large increases in adr and norad concentration
-lower levels are associated with smaller increases in blood catechols
-adr increases during clamping
-norad increases after unclamping
-mechanism s complex and multifactoral : hypotension, shock, direct ischemic excitation of spinal cord and adrenal medulla. - Free oxygen radicals
-hypoxic conditions, the metabolism of adenosine triphosphate produces adenosine, hypoxanthine, xanthine oxidase, purines, and oxygen free radicals. - Prostaglandins
-increase during and after clamping
-PGE, TXA A2 and TXA B2
-increased production of vasodilating prostaglandins during aortic cross-clamping
-vasoconstricting prostaglandins during unclamping - Platelets and neutrophils
-sequestration in lung
-attributable to anaerobic metabolic products and microaggregates released from the ischemic tissues
-Lymphocyte count decreases, whereas leukocyte and neutrophil counts increase, after unclamping of the aorta - Complement activation
-concentrations of the anaphylatoxins C3a and C5a increased
-Epidural anesthesia virtually prevented an increase in C5a and significantly modified an increase in C3a
-mechanism is unclear - Other
-increase in IL-1 and IL-6 due to increased sheer stress on endothelium
-increase in TNF due to ischemia
B. Respiratory
-increase in PVR especially during thoracic AoX
-mainly due to blood redistribution
-neutrophil sequestration and accumulation of microaggregates results in pulmonary edema
-can progress to ARDS which carries a high mortality
C. Kidneys
-infrarenal 5% incidence of renal failure requiring haemodialysis, associated large increase in renal vascular resistence and 30% decrease in renal BF
-suprarenal 15%
-thoracic 50% incidence of RF, severe 85-95% decrease in renal BF, GFR and UO
-renal failure always results from ATN
-ischemia-reperfusion insult
D. Spinal Cord
-incidence of paraplegia is 0.4-40%
-depends on urgency of operation, the presence of aortic dissection, hypotension, the age of the patient, and the duration and level of the aortic cross-clamping (<30min prefered)
-Approximately half of the patients with initial paraplegia make no neurologic recovery
-mechanism is due to decrease in spinal perfusion pressure
-survival depends on collaterial arteries and communications : Artery of Adamkewicz
-spinal perfusion pressure is made worse by blood volume shifts, which increase cerebral blood volume = increase in ICP
-therapeutic role of lumbar spinal drain to reduce CSF volume
-cooling
E. Abdominal viscera
-The reported incidence of visceral ischemia varies from 1-10%, with mortality exceeding 50%.
-The most common site of ischemia is the left part of the colon.
-Hypovolemia, thrombosis, cardiac insufficiency, and microembolism should also be considered in the development of bowel ischemia
Classify aortic dissections.
DeBakey
-based on where the original intimal tear is located and the extent of dissection
* Type I – Originates in ascending aorta, propagates at least to the aortic arch and often beyond it distally.
* Type II – Originates in and is confined to the ascending aorta.
* Type III – Originates in descending aorta, rarely extends proximally but will extend distally.
Standford
* A – Involves the ascending aorta and/or aortic arch, and possibly the descending aorta. The tear can originate in the ascending aorta, the aortic arch, or, more rarely, in the descending aorta. It includes DeBakey type I, II and retrograde type III[6] (dissection originating in the descending aorta or aortic arch but extending into the ascending aorta).
* B – Involves the descending aorta (distal to left subclavian artery origin), without involvement of the ascending aorta or aortic arch. It includes DeBakey type III without retrograde extension into the ascending aorta.
What are the advantages and disadvantages of a endoluminal AAA repair
A 25-year-old man with Marfan’s syndrome is scheduled for aortic arch reconstruction under circulatory arrest. Cooling to 18 degrees is planned. The maximum time for circulatory arrest at this temperature after which the risk of long term neurological injury increases markedly is
A. 15 minutes
B. 25 minutes
C. 35 minutes
D. 45 minutes
E. 55 minutes
ANSWER B
Hypothermic cardiac arrest at18°C provided electrocerebral silence is obtained, rewarmed correctly and hemodynamic stablity
<30 minutes : safe
<40 minutes : safe or transient neurological dysfunction
>40 minutes : neurological deficit is prone to occur especially in high risk (elderly, diabetes, hypertension)
-further cooling of the brain to 13°C to 15°C reduces the risk again how careful rewarming with close monitoring must occur
Oxford states
-45 min in adults
-60 min in neonates
A 40-year-old man with Marfan’s syndrome has undergone successful thoracoabdominal aortic reconstruction for aortic dissection. He has a CSF (cerebrospinal fluid) drain in situ. 48 hours post-operatively the CSF is noted to be bloodstained and he becomes obtunded. The most appropriate urgent investigation is
A. CSF microscopy and culture
B. MRI (magnetic resonance imaging) brain
C. MRI spine
D. non-contrast head CAT scan
E. serum electrolytes
ANSWER D
Decreased CSF pressure from drainage causing stretching then tearing of fragile subdural veins and consequent development of SDH
Marfan is associated with intracranial aneurysms and lowering pressure in the CSF compartment via lumbar drain increases the transmural pressure gradient in the aneurysm (if there is one), hence increases the risk of rupture.
During surgery for tracheostomy insertion, surgical diathermy is being used at the tracheal incision. You are ventilating with 100% oxygen. As the trachea is opened you notice a blue flame shooting up from the incision. Your first action should be to
A. disconnect the breathing circuit from the endotracheal tube
B. douse the wound with saline
C. insert a tracheostomy tube
D. remove the endotracheal tube
E. turn off oxygen and ventilate with air
ANZCA July 2007 Q118
A 40-year-old man with Marfan’s syndrome is to undergo thoraco-abdominal aortic reconstruction for chronic aortic dissection. An intrathecal catheter is inserted. The purpose for this is to
A. allow drainage of cerebrospinal fluid (CSF)
B. allow intrathecal administration of metabolic substrates
C. allow intrathecal administration of neuroprotective drugs
D. cool the spinal cord
E. facilitate spinal cord function monitoring
ANSWER A
The blood supply to the spinal cord and the kidney is reduced by 84-90% after cross-clamping the descending thoracic aorta at the level of the left subclavian artery.
Elective thoracic aortic repair has a 0.4% incidence of permanent cord injury, but emergency repair of an aortic rupture has a 24-40% incidence.
The incidence of perioperative spinal cord injury is increased by:
* cross-clamp times of greater than 30 mins, as the warm ischaemia time for the cord is 20-30 mins;
* high level of thoracic cross-clamping;
* emergency surgery (eg acute dissection or rupture when there are no collaterals);
* greater longitudinal extent of the aneurysm;
* patient age greater than 70 years; and,
* no prophylactic measures undertaken
Intraoperative methods of spinal cord protection include
-swift surgery, with identification and preservation of vital cord supply blood vessels
-cross-clamp times of less than 30 minutes
-Lumbar CSF drainage to increase the spinal cord perfusion pressure
-mild hypothermia (34-35 °C), which decreases the cerebral metabolic rate for oxygen by 20%
-Preliminary reports suggest intrathecal papaverine may provide some cord protection, as a result of its arteriolar vasodilating, calcium channel blocking and oxygen free radical scavenging properties
-Spinal cord somatosensory evoked potential (SSEP) monitoring has been recommended to detect spinal cord ischaemia ,
Shunts to improve perfusion distal to the cross-clamp have not influenced the incidence of paraplegia, due to the high resistance to retrograde flow in the ASA above the artery of Adamkiewicz inflow.
Describe the effect on ventilation/oxygenation with these misplaced DLT.
AL = correct positioning of the a left sided DLT
BL = L DLT too far in, resulting in ventilation of left lower or left upper lobe through the bronchial lumen, hypoxemia
CL = L DLT no for in enough, resulting in partial obstruction when ventilating through the tracheal lumen
DL = intubation of operative lung, resulting in severe hypoxemia when ventilating through bronchial lumen, but improvement during ventilating through tracheal lumen.
BR = introduced to far, resulting in ventilation of right middle and right lower lobe only, right upper is not ventilated, resulting in hypoxemia
AT08c [Apr97] [Jul98] [2001-Apr] Q50, [2001-Aug] Q31, [2003-Apr] Q3, [2003-Aug] Q54, [2005-Apr] Q38, [Jul05] [Mar06]
The most appropriate method for improving oxygenation during one lung anaesthesia, after institution of an FiO2 of 1.0, is application of
A. 5cm H2O CPAP to the non-dependent lung
B. 10cm H2O CPAP to the non-dependent lung
C. 5cm H2O PEEP to the dependent lung
D. 5cm H2O CPAP to the non-dependent and 5cm H2O PEEP to the dependent lung
E. intermittent re-inflation to the non-dependent lung
ANSWER C
OLV used for almost all thoracic operations : lung, esophageal, aortic or mediastinal surgery, to improve surgical access.
Although one lung is ventilated, both lung are perfused. Resulting in
-trans pulmonary shunting
-impairment of oxygenation
-hypoxemia
Treatment of hyoxemia during OLV
- Increasing FiO2
-effective in immediately treating
-will not improve with shunt fractions > 40% - Check position of DLT (using FOB)
- ensure adequate CO, reduce volatile to <1MAC
- Apply recruitment maneouvre
- Apply 5cm H2O PEEP to dependent lung
- Apply 1-2cm H2O CPAP to non-dependent lung after recruitment maneouvre
- Intermittent Reinflation
- Partial ventilation techniques including oxygen insufflation, HFJV, mechanical obstruction of blood flow to non-dependent lung
- clamp pulmonary artery of non ventilated lung (rare)
AT15 [Apr97] [Apr98] [Jul98] [Apr99] [Aug99] [2003-Apr] Q66, [2003-Aug] Q30, [Mar06] ANZCA version
Q42
The patient most likely to desaturate significantly during one lung anaesthesia is one who is having
A. a left sided thoracotomy, has reasonable PaO2 values during two-lung ventilation, but poor pre-operative spirometry
B. a right-sided thoracotomy, has relatively poor PaO2 values during two-lung ventilation but good pre-operative spirometry
C. a left-sided thoracotomy and has diminished perfusion but not ventilation to the operative lung on a V/Q scan
D. a right-sided thoracotomy, has relatively poor PaO2 values during two-lung ventilation and poor pre-operative spirometry
ANSWER B
OLV used for almost all thoracic operations : lung, esophageal, aortic or mediastinal surgery, to improve surgical access.
Although one lung is ventilated, both lung are perfused. Resulting in
-trans pulmonary shunting
-impairment of oxygenation
-hypoxemia
Prediction of Hypoxemia during OLV
1. Side of operation
-size R>L
-therefore operation on left lung (ei larger right lung is dependent and ventilated) results in better oxygenation
-FiO2 1, results in 280mmHg for left sided operation and 170mmHg for right sided operations
- Lung Function Abnormalities
a. airway obstruction with low FEV1 results in better oxygenation during OLV, perhaps due to autoPEEP resulting in reduced atelecatasis and improving oxygenation
b. low PaO2 on pre-operative ABG is a predictor for hypoxemia during OLV. - Distribution of perfusion - less perfusion of non ventilated lung and more to ventilated lung results in high PaO2 during OLV
a. large tumors in non ventilated lung = better PaO2 as they present for lobectomies or pneumonectomies
b. gravity, if ventilated lung is dependent = better PaO2; in one study in COAD pts, FiO2 1.0 resulted in PaO2 300mmHg in supine versus PaO2 490mmHg in lateral
AT23 [2003-Apr] Q105, [2003-Aug] Q86, [2004-Aug] Q95, [2005-Apr] Q86, [Jul05] [Mar06] ANZCA version
Q106
Complications, which usually present early following pneumonectomy, include all of the following EXCEPT
A. Broncho-pleural fistula
B. Respiratory failure
C. Right heart failure
D. Right to left shunt
E. Supraventricular arrhythmia
ANSWER A
Pneumonectomy is the surgical removal of an entire lung
-mainly for bronchogenic carcinoma in main stem bronchus
-rarely for pulmonary metastases, pulmonary tuberculos, fungal infections and broncheicatasis, traumatic lung injury, congential disease and bronchial obstruction
IMMEDIATE
Contralateral pneumonthorax
Sputum retention
Prolonged air leakage
Haemorrage
Phrenic nerve injury
R-L shunt through PFO due to increase in PA pressures
Acute respiratory insufficiency
EARLY
A. Respiratory :
-ARDS/post pneumonectomy pulmonary oedma - treatment is supportive, mortality>50%
-hemothorax, chylothorax
-empyema
B. Cardiac
-arrthymias AF
-AMI
-PE
-Cardiac herniation
LATE
A. postpneumonectomy syndrome
-extrinsic compression of distal trachea and mainstem bronchus due to shifting of the mediastinum
-progressive dyspnea, cough, inspiratroy stridor, recurrent pneumonia after 6 months of surgery
-treatment surgical repositioning of mediastinum
B. Bronchopleural fistula
-1.5-4.5%, mortality of 30-70%
-assocaited with empyema
C. Esophagopleural fistula
SC13 [2003-Apr] Q89, [2003-Aug] Q58, [Jul05] [Mar06]
The most appropriate investigation to diagnose Type A aortic dissections in potentially unstable patients is
A. angiography
B. CAT scan
C. magnetic resonance imaging (MRI)
D. transoesophageal echocardiography
E. transthoracic echocardiography
ANSWER D
Patient is potentially unstable.
SC26 [Mar06] [Jul06] ANZCA version
Q147
A patient is scheduled for emergency coronary artery bypass surgery (CABG) 2 hours after receiving tirofiban (Aggrastat) during coronary angiography and an unsuccessful coronary stenting procedure. The most useful strategy to treat or prevent excessive perioperative bleeding is:
A. administration of concentrated Factor VIII
B. administration of cryoprecipitate
C. delaying surgery another 2 hours
D. haemofiltration during cardiopulmonary bypass
E. platelet transfusion
ANSWER E
Tibrofiban (Aggrastat) is an antiplatelet agent
-Gycoprotein IIb/IIIa inhibitor (block the final common pathway of platelet aggregation)
-does not block platelet adhesion, screction of platelet products, inflammatory effects or thrombin activation
Used in the management of STEMI or unstable angina in patients awaiting PCI
Parental dosage
-2.5mg in 250ml NS (50mcg/ml)
-Loading dose 0.4mcg/kg/min for 30 minutes
-Maintenance of 0.1mcg/kg/min for up to 72 hours
-Infusion should continue through PCI and 12-24 hours after
-Stop for 8 hours prior to CABGs
Rapid onset and short duration of action
-coagulation returns to normal after 4-8 hours of ceassation
-half life 2 hours
Contraindications
-hypersensitivity
-active bleeding
-history of ICH, AV malformation, aneurysm
-thrombocytopenia induced by tibrofiban in past
-CVA in last 30 days
-recent surgery
-suggestive funding of aortic dissection
Complications
-major bleeding : ICH, retroperiotoneal, pulmonary, spinal-epidural haematoma
-anaphylaxis
-thrombocytopenia
ANZCA March 2006 Q71.
During elective major vascular surgery the best way to reduce the risk of acute renal failure is to maintain a normal
A. central venous pressure
B. mean arterial blood pressure
C. renal blood flow
D. systemic vascular resistance
E. urine output
ANSWER C
Describe the effects of the level of aortic occlusion on changes in CVS variables
Proximal decending Aox
MAP : increased 35%
CVP : increased 56%
Mean PAP : increased 43%
PWCP : increased 90% (due to blood volume distribution and increased afterload)
CI : decreased 30%
HR : no change
LV stroke work : no change
Supracaeliac AoX
MAP : increased 54%
PCWP : increased 38%
EF : decreased by 38%
LV end-systolic area : increased 69%
LV end-diastolic area : increased 28%
Wall motion changes in 92%
New AMI : 8%
Suprarenal AoX cause similar but smaller CVS changes.
Infrarnal AoX associated with only minimal change and no wall motion abnormalities
Describe the cardiovascular response to aortic unclamping.
Systemic hemodynamic response to aortic unclamping. AoX = aortic cross-clamping; Cven venous capacitance; R art = arterial resistance; Rpv = pulmonary vascular resistance; [arrow up] and [arrow down] = increase and decrease, respectively.
G. Response to unclamping
-SVR and MAP decrease by 70-80%
-CO may increase, decrease or remain unchanged
-LV end-diastolic pressure decreases
-myocardial blood flow increases
-flow through the terminal aorta and femoral arteries increases
-reactive hyperemia due to both metabolic and hormonal responses, lasting 15 minutes
-washout distal to the AoX occurs returning vaso and cardio-depressant compounds
-blood redistribution to vessels distal to AoX decrease venous return, cardiac output and MAP (hypovolemia)
To minimize cardiovascular responses
1. Gradual release of aortic clamp and reapplication : slow down the washout
2. Volume replacement
3. Sodium bicarbonate adminstration
SZ18 [2004-Aug] Q147, [2005-Apr] Q76, [Mar06] ANZCA version
Q148
Infra-renal aortic cross-clamping usually results in
A. decreased cardiac contractility
B. decreased coronary blood flow
C. decreased renal blood flow
D. minimal change in cardiac output
E. increased heart rate
ANSWER D
Systemic haemodynamic response to aortic cross-clamping
-preload does not always increase
-infra-renal aortic cross-clamping blood volume shifts into splanchnic circulation and preload does not increase
MAP : no change
PAP : no change
End-diastolic area : increase 9%
End-systolic area : increases 11%
Abnormal wall motion : 0
New AMI : 0
Describe the cardiovascular response to aortic clamping.
A. Primary variables
-MAP increases
-SVR increases
-HR no change
-CO generally decreases, but increases in thoracic AoX
B. Afterload, Preload and Blood volume redistribution
-impedance to aortic flow : increased afterload in all Aox
-preload changes depends on level of Aox
-thoracic AoX : passive recoil and emptying of capacitance vessels (both splanchnic and lower limbs) into the systemic circulation results a marked increased in preload and therefore cardiac output
-CVP, PWCP, LV end-diastolic area all increase depending on the level of AoX
-this effect is abolished if the IVC is clamped or blood is removed from the system (ei. phebotomy)
-differences in CVS response after AoX at difference levels is explained by different degrees and patterns of blood volume distribution
-infracaelic Aox maintains the splanchnic circulation, blood is redistributed to these capacitance vessels and preload is not significantly changed
-however this response depends on the sympathetic discharge to the splanchnic system, activation of the SNS may decrease venous capacitance resulting in increased preload
- Metabolism
-reduced total body oxygen consumption
-thoracic AoX results in 55% reduction
-anaerobic metabolism in tissues below Aox
-reduced O2 uptake in tissues above AoX
-proximal hypervolemia, vasodilation and increase in flow through these tissue may result in microcirculatory disturbances which jeopardize oxygen exchange
-activation of SNS constricts arterioles and decrease capillary flow results in shunting of blood away from tissue beds (possibly similar to hyperdynamic state in sepsis)
-Increase in mixed venous O2 sat (SVO2)
D. Coronary blood flow and myocardial contractility
-Aox increases both preload and afterload, leading to an increase in myocardial oxygen demand
-autoregulation : an increase in demand is met by an increase in supply by increasing coronary blood flow
-thoracic AoX 65% increase in CBF
-myocardial contractility is initially increased due SNS stimulation and physiological repsonse to increases in preload and afterload
-gradual decrease due to accumulation of cardiodepressant metabolites (H+, K+, adenosine) from ischaemic tissues
E. Duration of AoX
-with increased duration, SVR increases, while CO decreases
-possibly explained by capillary leak and reduction in circulating blood volume
-also release of cardiodepressant metabolites
F. Haemodynamic response distal to AoX
-aortic pressure decreases
-distal pressure is directly dependent on proximal aortic pressure through existing collateral vessels, therefore, proximal and distal aortic pressures must be maintained as great as the heart can withstand, otherwise a temporary shunt inserted.
-a decrease in arterial and subsequently, capillary pressure below AoX results in absorption of interstitial fluid (Starling’s forces)
-this mat increase venous return and circulating volume above AoX
Describe the non-cardiovascular responses to AoX.
A. Hormoral changes
1. Metabolic Lactic Acidosis
-degree of acidosis depends on degree of disease, time of AoX, level of AoX, collateral vessels
- RAS
-activation of renin-angiotension system
-suprarenal AoX results in reduced perfusion pressure in the afferent arterioles of the kidney
-infrarenal AoX also increases RAS but the mechanism is less clear
-?activation of SNS
-?effect of prostaglandins - Catecholamines and SNS
-thoracic AoX is consistently associated with large increases in adr and norad concentration
-lower levels are associated with smaller increases in blood catechols
-adr increases during clamping
-norad increases after unclamping
-mechanism s complex and multifactoral : hypotension, shock, direct ischemic excitation of spinal cord and adrenal medulla. - Free oxygen radicals
-hypoxic conditions, the metabolism of adenosine triphosphate produces adenosine, hypoxanthine, xanthine oxidase, purines, and oxygen free radicals. - Prostaglandins
-increase during and after clamping
-PGE, TXA A2 and TXA B2
-increased production of vasodilating prostaglandins during aortic cross-clamping
-vasoconstricting prostaglandins during unclamping - Platelets and neutrophils
-sequestration in lung
-attributable to anaerobic metabolic products and microaggregates released from the ischemic tissues
-Lymphocyte count decreases, whereas leukocyte and neutrophil counts increase, after unclamping of the aorta - Complement activation
-concentrations of the anaphylatoxins C3a and C5a increased
-Epidural anesthesia virtually prevented an increase in C5a and significantly modified an increase in C3a
-mechanism is unclear - Other
-increase in IL-1 and IL-6 due to increased sheer stress on endothelium
-increase in TNF due to ischemia
B. Respiratory
-increase in PVR especially during thoracic AoX
-mainly due to blood redistribution
-neutrophil sequestration and accumulation of microaggregates results in pulmonary edema
-can progress to ARDS which carries a high mortality
C. Kidneys
-infrarenal 5% incidence of renal failure requiring haemodialysis, associated large increase in renal vascular resistence and 30% decrease in renal BF
-suprarenal 15%
-thoracic 50% incidence of RF, severe 85-95% decrease in renal BF, GFR and UO
-renal failure always results from ATN
-ischemia-reperfusion insult
D. Spinal Cord
-incidence of paraplegia is 0.4-40%
-depends on urgency of operation, the presence of aortic dissection, hypotension, the age of the patient, and the duration and level of the aortic cross-clamping (<30min prefered)
-Approximately half of the patients with initial paraplegia make no neurologic recovery
-mechanism is due to decrease in spinal perfusion pressure
-survival depends on collaterial arteries and communications : Artery of Adamkewicz
-spinal perfusion pressure is made worse by blood volume shifts, which increase cerebral blood volume = increase in ICP
-therapeutic role of lumbar spinal drain to reduce CSF volume
-cooling
E. Abdominal viscera
-The reported incidence of visceral ischemia varies from 1-10%, with mortality exceeding 50%.
-The most common site of ischemia is the left part of the colon.
-Hypovolemia, thrombosis, cardiac insufficiency, and microembolism should also be considered in the development of bowel ischemia
Classify aortic dissections.
DeBakey
-based on where the original intimal tear is located and the extent of dissection
* Type I – Originates in ascending aorta, propagates at least to the aortic arch and often beyond it distally.
* Type II – Originates in and is confined to the ascending aorta.
* Type III – Originates in descending aorta, rarely extends proximally but will extend distally.
Standford
* A – Involves the ascending aorta and/or aortic arch, and possibly the descending aorta. The tear can originate in the ascending aorta, the aortic arch, or, more rarely, in the descending aorta. It includes DeBakey type I, II and retrograde type III[6] (dissection originating in the descending aorta or aortic arch but extending into the ascending aorta).
* B – Involves the descending aorta (distal to left subclavian artery origin), without involvement of the ascending aorta or aortic arch. It includes DeBakey type III without retrograde extension into the ascending aorta.
What are the advantages and disadvantages of a endoluminal AAA repair
TBA
SC28 ANZCA Version [Jul06]
Q143
A 25-year-old man with Marfan’s syndrome is scheduled for aortic arch reconstruction under circulatory arrest. Cooling to 18 degrees is planned. The maximum time for circulatory arrest at this temperature after which the risk of long term neurological injury increases markedly is
A. 15 minutes
B. 25 minutes
C. 35 minutes
D. 45 minutes
E. 55 minutes
ANSWER B
Hypothermic cardiac arrest at18°C provided electrocerebral silence is obtained, rewarmed correctly and hemodynamic stablity
<30 minutes : safe
<40 minutes : safe or transient neurological dysfunction
>40 minutes : neurological deficit is prone to occur especially in high risk (elderly, diabetes, hypertension)
-further cooling of the brain to 13°C to 15°C reduces the risk again how careful rewarming with close monitoring must occur
Oxford states
-45 min in adults
-60 min in neonates
SC29 ANZCA Version [Jul06] Q120
A 40-year-old man with Marfan’s syndrome has undergone successful thoracoabdominal aortic reconstruction for aortic dissection. He has a CSF (cerebrospinal fluid) drain in situ. 48 hours post-operatively the CSF is noted to be bloodstained and he becomes obtunded. The most appropriate urgent investigation is
A. CSF microscopy and culture
B. MRI (magnetic resonance imaging) brain
C. MRI spine
D. non-contrast head CAT scan
E. serum electrolytes
ANSWER D
Decreased CSF pressure from drainage causing stretching then tearing of fragile subdural veins and consequent development of SDH
Marfan is associated with intracranial aneurysms and lowering pressure in the CSF compartment via lumbar drain increases the transmural pressure gradient in the aneurysm (if there is one), hence increases the risk of rupture.
AC132 [2004-Aug] Q136, [Jul06] ANZCA version Q76
During surgery for tracheostomy insertion, surgical diathermy is being used at the tracheal incision. You are ventilating with 100% oxygen. As the trachea is opened you notice a blue flame shooting up from the incision. Your first action should be to
A. disconnect the breathing circuit from the endotracheal tube
B. douse the wound with saline
C. insert a tracheostomy tube
D. remove the endotracheal tube
E. turn off oxygen and ventilate with air
ANSWER A
Miller covers this under laser anaesthesia airway fire protocol chapter 67:
1. remove source of flame (Surgeon)
2. stop ventilation (Anaesthetic)
3. disconnect breathing circuit
4. extinguish with bucket of water, flood oropharynx, consider flushing saline down ETT to extinguish intraluminal fire
5. consider removing ETT and ventilate with 100% O2 via face mask (doesn’t actually talk about removing the ETT but I got the impression this is when it would be taken out - when no flame, no gas to combust)
6. re-intubate and assess damage and remove debris - direct laryngoscopy, rigid bronchoscopy, +/- gentle lavage and distal FOB
7. If damage, retube and if severe damage may need low tracheostomy
8. Consider steriods and antiobitcs
9. Post event CXR
Prevention of airway fires for surgeric tracheostomy insertion :
The following anaesthetic and surgical recommendations are suggested.
- Anaesthetic
- Use the minimum concentration of oxygen to maintain arterial saturation.
- Use other non-oxidizing agents such as helium, air or nitrogen in place of nitrous oxide.
- Position the ETT near the carina to minimize exposure of the cuff to injury in opening the trachea.
- A good seal on the cuff is essential to prevent leaking of anaesthetic gases.
- Fill the cuff with water to act as a fire retardant.
- Consider using fire resistant ETT (silicone/metallic) often used in laser surgery.
- Surgical
- Minimize use of diathermy particularly once the trachea is opened.
- Use bipolar diathermy if bleeding occurs once the trachea is opened.
- Use suction to remove oxygen rapidly from the field.
- Surround the operating field with moist pack if diathermy has to be used.
- Always have sterile saline at hand in case of fire.
Major complications of mediastinoscopy include all of the following EXCEPT
A. compression of the great vessels
B. air embolism
C. pneumothorax
D. major haemorrhage
E. phrenic nerve damage
ANSWER A
Complications of mediastinoscopy
* Death
* MAJOR complications
Major haemorrhage
Tracheobronchial laceration
Oesophageal perforation
Recurrent nerve paralysis
Phrenic nerve paralysis
Thoracic duct injury
Cerebrovascular accident
Mediastinitis
Venous air embolism
Tumour implantation
* MINOR complications
Pneumothorax
Superficial wound infection
Recurrent nerve paresis
Minor bleeding
Autonomic reflex braydcardia
Mediastinal lymph node necrosis
Compression of the great vessels occurs and warrents invasive blood pressure monitoring, however it is rarely a complications as it is transient.
