Cardiothoracic And Vascular Surgery Flashcards
Left sided DLT with both bronchial and tracheal cuffs inflated
You will have a DLT placement question on your boards. It will unlikely be as easy as this on unfortunately. A properly positioned L-DLT has the bronchial lumen in the left main bronchus with the bronchial cuff inflated and occluding the left main bronchus just below the carina. The tracheal lumen should be above the carina. Therefore isolated bronchial ventilation should only be heard on the left and isolated tracheal ventilation should only be heard on the right.
Lady has thoracic aortic aneurysms which displaces trachea. How to manage plan to intubate?
Thoracic aortic aneurysm can invade the bronchus and have high risk for aortic-tracheal fistula formation with massive haemorrhage. With direct visualization under FOB the DLT can be placed slowly and carefully so that the ETT does not come into contact with the area of the trachea that is pulsating. Fluoroscopy could not delineate where in the trachea the aorta is direct contact as specifically as FOB. Insertion of a tube exchanger could cause direct trauma to the trachea and aorta leading to bleeding. Other options to DLT include bronchial blockers, apneic oxygenation and intermittent double lung ventilation with a single lumen ETT well above the carina.
Patient to have wedge resection for cancer, but complains of weakness and lethargy and altered consciousness. Do you cancel he case? Why or why not?
Small-cell lung cancer is a classic paraneoplastic syndrome offender. Common syndromes include Lambert-Eaton (weakness improving with exercise), arginine vasopressin (hyponatraemia, confusion, lethargy), parathyroid hormone (hypercalcaemia), and ACTH (cushing’s syndrome). Weakness may be apparent on PFTs, but will not explain the underlying problem. Lethargy, hypercalcaemia, and fevers are common for patients with cancer, especially metastases, but given the high likelihood of paraneoplastic syndrome with small cell cancer, this should be evaluated. Furthermore, lung resection would not be standard therapy for a patient with known metastases.
Poor predictors of pneumonectomy. Expound on the FEV part
Patients with poor pulmonary status tend to tolerate pneumonectomy very poorly. Patients that have such poor lungs that they have low FEV1s, FEV1/FVC ratios, CO2 retention, and low breathing capacities are unable to survive with one lung because it typically takes two ‘bad’ lungs to produce such awful results. (Review question 28 in respiratory physiology section). Patients unlikely to recover from pneumonectomy are classically cited as PaCO2 > 45; PaO2 < 50 on RA; FEV1 < 2L; FEV1/FVC < 50%; maximum breathing capacity < 50% predicted; maximum VO2 < 10 ml/ kg/ min.
FEV1 < 2L is a bit more complicated because the data points to post pneumonectomy patients with FEV1 < 800 ml (single lung) do poorly. To generate a preoperative single lung FEV1, an awake double lumen tube can be placed for lung isolation or the FEV1 (both lungs) can be multiplied by the amount of perfusion it receives on VQ scan. For example if the FEV1 were 2L but the lung scheduled for resection receives only 20% of the perfusion, then the predicted post op FEV1 of the remaining lung would be 2 L X 80% = 1.6 L. Reread this last sentence.
Lower lung syndrome in the dependent lung? How? And how can this develop in the upper lung?
Transudation of fluids to the lower lung leading to increased shunting and hypoxia
Lower lung syndrome is a common result of over-aggressive crystalloid administration during one lung ventilation in the lateral decubitus position. It’s due to gravity dependent movement of fluid towards the dependent lung, which of course, is exacerbated with high volumes of crystalloid administration. The upper surgical lung is also very prone to pulmonary oedema, but from a different mechanism. In this case, surgical manipulation as well as repeated inflation and deflation lead to lung damage leading to non-cardiogenic pulmonary oedema. Capillary leak is likely a large contributor to this syndrome, but is exacerbated as well with large amount of fluid administration, especially crystalloid.
OLV and order of which to do things with destaurations
D: 5 cm H20 of CPAP to surgical lung
The problem here is shunt, and despite hypoxic pulmonary vasoconstriction (HPV) the non-dependent surgical lung is receiving enough blood flow to account for the decreased saturations. By administering CPAP (with 100% oxygen), a portion of the previously shunted flow will now be able to participate in oxygen exchange, therefore decreasing shunt. PEEP to the dependent lung is also usually effective, although not as consistently as CPAP. The reason for this is, theoretically, the increased positive pressures at end-expiration (compared to 0 with no PEEP) could divert flow away from the ventilated dependent lung and towards the nonventilated surgical lung. The advantage of PEEP in increasing oxygenation by way of opening previously atalectatic alveoli in the dependent lung typically outweighs this, but not always. Double lung ventilation is the best way to increase oxygen sats in most circumstances, but can make dissection difficult for the surgeon. In this case, the surgeon is at a critical portion of the dissection and should not be used as it may result in damage to the PA. Blood transfusion may increase oxygen carrying capacity, but will not affect the patient’s oxygen saturation.
Three hours following a pneumonectomy a patient in the PACU is repositioned by the nurses and has a BP drop from 120/60 to 70/ 30, HR from 80 to 100, and saturations drop from 90% on nasal cannula to 75%. You notice that the patient’s external jugular veins are distended, you hear diffuse wheezing as well as increasing rales on auscultation of the chest and new st segment depressions are apparent on the continuous ECG monitor. Chest tubes are in place and tidaling appropriately. What most likely occurred:
Cardiac herrniation can occur following (or during) pneumonectomy as the heart is (typically) pushed out through a pericardial defect (from positive pressure ventilation or position changes) and into the space where the resected lung previously occupied. Twisting of the SVC can cause SVC syndrome, twisting of the trachea can present with wheezing, twisting of pulmonary veins can present with pulmonary oedema, pericardial constriction can cause hypotension and ischaemia.
Pt had right sided strike during mediastinoacopy:
Either the arterial line or pulse oximeter should have been placed on the right arm
During mediastinoscopy, the scope can compress the innominate artery, which can go undetected save for specific monitoring in its vascular distribution. In this case the right innominate was compressed which would have presented as loss of waveform on either pulse oximeter or arterial blood pressure monitor. Hypotension (inferred by answer choice:”Non-invasive BP cuff should have been used to confirm arterial line accuracy” ) would present with bilateral ischaemia to the brain as would air embolism (TEE monitor).
Mentally challenged patient with SVS syndrome. What’s your plan for induction?
SVS is due from mass effect in the mediastinum leading to superior vena cava compression. This results in a couple problems: the oedema of the head, neck and extremities leads to a difficult ventilation and intubation, difficult iv access, and mediastinal mass can lead to airway compression. Airway compression can be secondary to position (supine vs sitting vs lateral decubitus) and loss of muscle tone, especially with muscle relaxants can lead to further vascular and airway obstruction, precipitating cardio-pulmonary collapse. The vascular compression decreases preload, and decreasing preload further with induction of anesthesia can in itself lead to severe hypotension. Therefore induction of anesthesia should have the following goals of maintaining spontaneous ventilation, avoiding muscle relaxation, and avoiding coughing and straining (leading to airway obstruction). Given her severe mental retardation, the patient is uncooperative. Of the available options, ketamine induction is probably best as it does not require patient cooperation and meets all of the goals listed above. Option A is also a reasonable choice, however given the increased likelihood of impossibility to ventilate if the airway obstructs, ketamine is a better choice. Thiopental is primarily a preload reducer and a poor choice in this situation. Also all choices using muscle relaxants would be contraindicated. Awake trach requires patient cooperation.option A was prop pushes
Surgeon reports massive hemorrhage in pt with SVC syndrome-where to place the access?
With SVC syndrome, administering fluids above the obstruction (on the SVC) leads to further oedema, but does little to nothing to increase volume to the heart. Therefore, lower extremity access should be obtained. For massive haemorrhage, large volumes of fluid will need to be delivered, and the introducer sheath can deliver fluid faster than the triple lumen. Recall that resistance to flow is proportional to eight times its length and inversely proportional to its radius to the fourth power.
Three months following lung transplant, which of the following would be expected to be fully intact:
A. Mucociliary function
B. Cough reflex
C. Hypoxic pulmonary vasoconstriction (HPV)
D. Immune function
Explain the others that are incorrect
The correct answer is: C: Hypoxic pulmonary vasoconstriction (HPV)
Following lung transplant, the transplanted lung(s) will be denervated and lose the cough reflex in the transplanted portion of the airways (tracheal and carinal will be unaffected, but bronchial will be denervated distal to anastomosis). Mucociliary function is significantly reduced in these patients as well. Immunosupressants are continued for maintenance of rejection prevention. HPV is intrinsic property of the lung and remains intact.
Order of cannula and cross lamp with CPB
Aortic cannula is placed first, followed by venous cannula(s). Aortic cross-clamp cannot be applied until bypass has been established.
Which of the following procedures is hypotension MOST likely expected during cardiac surgery utilizing cardiopulmonary bypass (CPB):
A. Insertion of venous cannula
B. Insertion of aortic cannula
C. Sternal splitting
D. Harvesting of grafts
Explain the hemodynamics of the wrong ones also
The correct answer is: A: Insertion of venous cannula
During insertion of the venous cannulas, preload is significantly decreased by physical obstruction. Aortic cannula insertion typically results in far less haemodynamic derangements. Sternal splitting is an expected time of stimulation with associated hypertension. Harvesting the grafts is a time of low level stimulation where hypotension can be problematic, but not as predictable as during venous cannula insertion.
During cardiac surgery utilizing cardiopulmonary bypass (CPB) the aortic cannula is placed while the BP on arterial line was 190/100. Following initiation of CPB, extreme unremitting hypotension occurs. Venous return is noted to be decreased and the CPB machine appears to be working properly. Inspection of airway, head and neck reveal no abnormalities. What was the MOST likely cause of the hypotension:
A. Switching of the cannulas (venous for aortic) B. Massive venous air embolism C. Aortic dissection D. Aortic cannula misdirection E. Haemodilution
The correct answer is: C: Aortic dissection
Insertion of the aortic cannula during periods of uncontrolled hypertension is a risk factor for aortic dissection with resultant aortic flows into the false lumen leading to hypotension and decreased venous return. Switching of cannulas is not the right answer because the stem reported that the CPB was most likely functioning properly. Aortic cannula misdirection and air embolism are not correct, and will be discussed below. Haemodilution does decrease resistance and can decrease BP, but does not explain decreased venous return.
45 year old woman with DM1 with a preoperative glucose of 275 was started on an insulin gtt immediately after induction for cardiac surgery utilizing cardiopulmonary bypass (CPB). 20 minutes following CPB facial blanching and oedema is noted, mydriasis, and a MAP of 90 is read on right arterial line while left non invasive BP cuff reads 70/ 35. The most likely reason for this presentation is:
A. Uncontrolled hyperglycaemia with generalized oedema
B. Uncontrolled hyperglycaemia with cerebral oedema
C. Switching of cannulas
D. Aortic cannula misdirection
E. Massive venous air embolism
The correct answer is: D: Aortic cannula misdirection
Misplacement of the aortic canulla, into the innominate or carotid artery can present with facial oedema, blanching, mydriasis, conjunctival injection, and hypertension (HTN) on the side of misdirection. Misdirection tends to occur towards the right innominate, which would lead to HTN on the right and hypotension on the left arm. Switching of cannulas (venous for arterial) would lead to global hypotension. Uncontrolled hyperglycaemia may lead to worsened neurologic outcome, but cereberal oedema would not occur this early (as it is due to upregulation of osmotically active proteins within the brain to counteract the osmotic effects of hyperglycaemia in the serum).
Following massive air emboli in CPB Circuit, what should you do-positioning? Additional maneuvers to make flow backwards? What temp should the blood be? After blood has been purged-then what? What should your pressures be, and why? What are some other options?
Following massive air embolism CPB should be immediately interrupted and the patient placed in steep trendelenberg (air will move up away from brain due to gravity). Additional maneuvers for possible improvement of neurologic outcome are to have retrograde CPB through the SCV cannula, essentially pushing air backwards and out the aortic cannula site. Intermittent carotid compression can theoretically induce backwards flow through the vertebral arteries to purge air from that system as well. The blood should be cooled as hypothermia decreases brain oxygen consumption. After the air has been purged, CPB can resume. Induced HTN at this time may push small microbubles through the circulation. Steroids, barbiturate coma, and hyperbaric chambers are additional options.
Minimally invasive off pump has what advantages? What doesn’t change?
Minimally invasive off-pump cardiac surgery is associated with decreased respiratory infections (perhaps due to earlier extubation but patient selection may confound this), decreased incidence of atrial fibrillation post operatively, less ionotropes use, and fewer blood transfusions. There is no difference in mortality, stroke, MI, or renal function.
Prior to removing the final cannula after cardiac surgery utilizing cardiopulmonary bypass (CPB), the cardiac surgeon requests 100 cc of blood be delivered to the patient due to hypotension via the perfusion tech. Through which cannula is this delivered:
The correct answer is: B: Aortic cannula
The venous cannula is removed first after CPB due to obstruction of preload, therefore additional volume by the perfusionist is delivered through the aortic cannula (see question 14).
Where do you look to make sure the heart is de-Aires?
Left ventricular apex
In the trendelenberg position air accumulates at the apex of the ventricle which will be expelled through the outflow tract when repositioned supine. Surgeries in which the heart is opened (valvular, muscle resection, etc) have a higher incidence of neurologic insult due to air embolism.
Prior to removing the final cannula after cardiac surgery utilizing cardiopulmonary bypass (CPB), the cardiac surgeon requests 100 cc of blood be delivered to the patient due to hypotension via the perfusion tech. Through which cannula is this delivered:
The venous cannula is removed first after CPB due to obstruction of preload, therefore additional volume by the perfusionist is delivered through the aortic cannula
