Cardiothoracic anaesthesia Flashcards
1
Q
What is the mortality for lobectomy and pneumonectomy?
A
2-4% and 6-8% respectively
2
Q
What is ppoFEV1?
A
Predicted postoperative forced expiratory volume in 1 second. It is the most validated marker for post operative respiratory complications.
3
Q
How can you calculate the ppoFEV1?
A
(Pre-op FEV1) X (% lung remaining) = ppoFEV1 (functionally inactive lung pre-operatively doesn’t contribute)
4
Q
What is TLCO or DLCO?
A
This is the transfer co-efficient using carbon monoxide. A measure of diffusion capacity of the lung. When referenced to lung volume it is given as KCO.
5
Q
What are the risk categories for ppoTLCO?
A
low risk: >40% moderate-high risk:
6
Q
What are the boundaries of the paravertebral space?
A
Anteriorly: Parietal pleura Posteriorly: Costotransverse ligament Medially: spinal foramina
7
Q
What are the risk categories for ppoFEV1?
A
Low risk: > 40% Moderate risk: 30-40% High risk:
8
Q
Name structure 1.
A
Dorsal root ganglion (sensory)
9
Q
Coronary Perfusion Pressure
A
CPP = Aortic Root Diastolic Pressure - LVEDP
10
Q
Myocardial O2 Extraction Ratio
A
70%
11
Q
Coronary sinus saturation
A
30%
12
Q
Standard approach to cardiac anaesthetics
A
- Consider Lorazepam 2-3mg 2 hours pre-op
- Fentanyl 5 - 15 mcg/kg
- NB, Fentanyl is filtered out in CPB
- Propofol up to 1.5 mg/kg
- Pancuronium / Vecuronium preferred
- Isoflurane (mimics ischaemic pre-conditioning, lowers myocardial O2 demand, steal syn. probably not an issue)
13
Q
Institution of CPB - Anticoagulation requirements
A
ACT > 480 seconds
Requires Heparin 300-400 units/kg
14
Q
Establishing CPB
A
- Heparinise, aim SBP 100 mmHg
- Cannulate aorta
- 100 mL bolus, test bounce
- Check not carotid
- Site venous pipes (Bicaval/Right Atrium)
- Attach cardioplegia lines
- Increase flow from CPB
- Aortic cross clamp
15
Q
What are the essential component of CPB
A
- 1 or 2 Venous cannulae
- Venous reservoir
- Fresh gas supply (and volatile vapouriser)
- Oxygenator
- Heat exchanger
- Pumps
- Arterial cannulae (and filter)
16
Q
Qualities of a bubble oxygenator
A
- Positive
- Efficient
- Cheap
- Low resistance
- Negative
- Difficult to control O2/CO2 independently
- Causes haemolysis and clotting abnormalities
- Limited to a few hours use
17
Q
Qualities of a membrane oxygenator
A
- High resistance
- Less damaging to blood components
- Provides long term support (12 hours or more)
18
Q
What is a membrane oxygenator?
A
Cellulose or polypropylene membrane arranged in hollow fibres. Blood and gas phases are separated, gas exchange occurs by diffusion
19
Q
Myocardial Preservation Techniques
A
- Cardiostable GA
- Pre-conditioning
- CPB - offloading heart reduces myocardial work
- Aim:
- Hb 7-10
- MAP > 70
- CPP > 50
- Slow heart rate
- Turn off ionotropes once on CPB
- Venting of LV
- Avoid LV distention (AR very difficult)
- Cardioplegia
- Hypothermia
20
Q
St. Thomas’ (No.2) Cardioplegia Solution
A
- K - 16 mmol/L
- Mg - 16 mmol/L
- Ca 1.2 mmol/L
- NaCl - 120 mmol/L
- NaBicarb - 10 mmol/L
21
Q
Blood cardioplegia
A
- Good supply of protein buffers, nutrients and O2
- Superior to crystalloid
- Excellent if myocardium ischaemic
- Cold intermittent administration
- Warm administartion rarely used
22
Q
Cardioplegia route of administration
A
- Antegrade:
- Via aortic root, direct into ostia
- Problems if CA obstruction, AR, LVH
- Retrograde:
- Via coronary sinus
- May not garuntee protection of RV
- Often a combnination technique is ued
23
Q
Protamine dose
A
1mg per 100 units of Heparin
24
Q
Problems with protamine
A
- Histamine release
- Myocardial depression
- Systemic vasodilatation
- Severe anaphylactoid reactions
- Acute catastrophic pulmonary hypertension and RV failure
- GIVE SLOWLY (5-6 mins)
25
Proceedure for coming of CPB
* Warm to 36.5
* Establish cardiac rate and rhythm compatible with CO
* Lungs ventillating
* Iontropes back on if needed
* IABP monitoring functional
* Check metabolic disturbance
* Perfusionist ready with adequate blood in reservoir
26
pH-STAT or alpha-STAT
* alpha stat - typically in adults (reduces risk of neurological injury from microemoli)
* pH stat - typically neonates (reduces risk of neurological injury from hypoperfusion)
27
pH Stat regulation
* Maintains pH in normal range when corrected for temperature, by the addition of CO2 into CPB
* Creates a mild acidosis when measured at 37°C
* Promotes vasodilitation with increased risk of microemboli.
28
alpha stat regulation
* Maintains pH in normal range when measured at 37°C
* Alpha describes the unprotonated fraction of imidazole moiety of histidine (most important intracellular buffer)
* Thought to be more physiological
* Promotes acid load removal from metabolically active tissues
* Preffered in adults
29
CPB's effect on blood and complement
* Activates **alternative** pathway
* **C3a** and **C5a** increase on CPB
* Triggers **polymorphonuclear leukocytes** (PMN) to marginate and adhere
* PMNs increase **capillary leakage**
* Platelets activated (Increased **adherance**, **reduced function**)
* Erythrocytes (increased **haemolysis**)
* Cytokines (Increased **TNF** and **IL-8**)
* **Kallikrein-Kinin** system activation (bradykinin release)
30
CPB's endocrine response
* Increased:
* Catecholamine release
* ADH
* Cortisol
* Renin, Angiotensin, Aldosterone
* Reduced:
* Insulin response
31
Organ Dysfunction following CPD
* Brain: 1-2% Major CVA, Post Op cognitive impairement
* Macro/Micro emboli
* Hypoperfusion
* Inflammatory response
* Respiratory: Post pump pulmonary dysfunction
* Emboli causing V/Q mismatch
* Complement PMN activation
* Increased pulmonary hydrostatic pressure (poor venting)
* TRALI
* Renal: dysfunction in 15%
* Hypothermia
* Hypoperfusion
* Haemoglobinuria 2° to haemolysis can cause ATN
* Liver: Hepatic dysfunction in 20%
* Hypotention, hypoxia
* Worse with high Right pressures
32
MIDCAB
Minimally invasive direct coronary artery bypass. A left anterolateral thoracotomy for single LIMA to LAD graft
33
OPCAB
Off Pump Coronary Artery Bipass. Also called Beating Heart Surgery
34
Why is OPCAB beneficial
Avoids all the pitfalls of CPB
35
Anaesthetic implications of OPCAB
* Prepare for sudden loss of CO (prepare for CPB)
* Expect high bleeding
* Arrythmias are common (cardiac manipulation)
* Potential for severe MR and TR (and severe pulmonary oedema)
* Challenging to maintain normothermia (lots of the body exposed)
* Myocardial ischaemia detection difficult as ECG unreliable
36
Anaesthetic technique for OPCAB
* Cardiostable GA
* Consider thorassic epidural
* Monitor for ischaemia
* TOE
* PAC (increased PA pressure with LV ischaemia)
* Avoid ionotropes
* Small doses phenylephrine to maintain coronary perfusion pressure
* Minimise arrythmias from handling
* 8 mmol Mg over 15 mins
* K \> 4.5
* Beaware of pulmonary oedema - diuretics as needed
* Consider cell salvage
* Fluid warming, heated mattress
* Aim ACT \> 350
37
Insidious signs of postoperative cardiac tamponade
* CVS deterioration
* Increasing ionitropic requirements
* Rising CVP
* Dropping urine output
* Evolving metabolic acidosis
* Poor end of the bed-o-gram
38
Treatment of postoperative cardiac tamponade
Return to theatre for re-sternotomy under GA. note, needle pericardiocentesis is inappropriate in this setting as it will not remove clot
39
Moving a patient back to theatre for re-sternotomy (intubated)
* Maintain all monitoring
* Hand ventillate and maintain appropraite sedation
* Maintain all ionotropic infusions
* X-Match 2 units minimum (plus other products)
* Ensure NMB
* Switch onto Isoflurane
* Consider BIS
* Take baseline ABG
* Small dose fentanyl
* Start
40
Moving a patient back to theatre for re-sternotomy (non-intubated)
* Maintain all monitoring
* FiO2 = 1 via 15 L NRB mask
* Maintain all ionotropic infusions
* X-Match 2 units minimum (plus other products)
* Patient is heavily dependent on sympathetic drive to maintain CO - GA will remove this
* Prepare for surgery proir to induction
* Etomidate 0.15-0.2 mg/kg
* Rocuronium 1 mg/kg
* Consider RSI
* Expect loss of output
* Start
41
Causes of excessive bleeding post cardiac surgery
* Surgical haemostatic problem
* Inadequte reversal of heparin
* Excessive fibrinolysis
* Reduced platelet count/function
* Clotting factor deficiency
* Complement activation
42
Anaesthetic considerations for heart transplanted patients
* Note cardiac denervation
* CO cannot increase by HR easily
* CO can increase by SV (i.e fluid)
* Chronically elevated catecholamine levels
* Epedrine / Atropine ineffective
* Adrenaline / Isoprenaline better
* Maintrain pre-load at all costs
* Note accellerated athersclereosis and silent ischaemia
43
44
Describe the different parameters in TEG
1. R-time: reaction time (s); time of latency from start of test to initial fibrin formation (amplitude of 2mm); **initiation**
2. K-time: kinetics (s); time taken to achieve a certain level of clot strength (amplitude of 20mm); **amplification**
3. alpha angle: slope between R and K; measures the speed at which fibrin build up and cross linking takes place, hence assesses the rate of clot formation; **thrombin burst**
4. MA: maximum amplitude (mm); represents the ultimate strength of the fibrin clot; **clot strength**
5. LY-30: amplitude at 30 minutes; percentage decrease in amplitude at 30 minutes post-MA; **fibrinolysis**
45
What are the treatment options availible for different TEG traces?
* Increased R time =\> FFP
* Decreased angle =\> cryopreciptate
* Decreased MA =\> platelets (consider DDAVP)
* Fibrinolysis =\> tranexamic acid (or aprotinin or aminocaproic acid)
46
What does this trace show?
Hypercoagulability
* R and K Decreased
* Angle and MA Increased
47
What does this trace show?
Hyperfibrinolysis
* R and K normal
* MA normal or continuously decreasing
* LY-30 \> 7.5%
48
What does this trace show?
DIC Stage 1
* R, K, Alpha, MA Increased
* LY-30 Increased (Secondary fibrinolysis)
49
What characteristics will platelet dysfunction show on TEG?
* Normal R (normal initiation)
* Decreased K (slow amplification)
* Decreased MA
* Normal LY-30
50
Describe the blood supply to the heart
* Right and Left coronary arteries branch from the aorta
* The left coronary artery divides itself into:
* Left anterior descending artery (LAD)
* Ramus circumflexus (RCX)
* The right coronary artery (RCA) connects to the ramus descendens posterior (RDP)
* In 20% of the normal population the RDP is supplied by the RCX (left dominance)
51
Describe the ECG findings for an anterior MI
* ST Elevation in:
* V1-V6
* Reciprocal ST Depression in:
* Nill
* Coronary artery teritory
* LAD
52
Describe the ECG findings for a septal MI
* ST Elevation in:
* V1-V4, disappearance of septum Q in leads V5,V6
* Reciprocal ST Depression in:
* Nill
* Coronary artery teritory
* LAD-septal branches
53
Describe the ECG findings for a lateral MI
* ST Elevation in:
* I, aVL, V5, V6
* Reciprocal ST Depression in:
* II,III, aVF
* Coronary artery teritory
* LCX or MO
54
Describe the ECG findings for an inferior MI
* ST Elevation in:
* II, III, aVF
* Reciprocal ST Depression in:
* I, aVL
* Coronary artery teritory
* RCA (80%) or RCX (20%)
55
Describe the ECG findings for a posterior MI
* ST Elevation in:
* V7, V8, V9
* Reciprocal ST Depression in:
* high R in V1-V3 with ST depression V1-V3 \> 2mm (mirror view)
* Coronary artery teritory
* RCX
56
Describe the ECG findings for a Right Ventricle MI
* ST Elevation in:
* V1, V4R
* Reciprocal ST Depression in:
* I, aVL
* Coronary artery teritory
* RCA
57
Describe the ECG findings for an atrial MI
* ST Elevation in:
* PTa in I,V5,V6
* Reciprocal ST Depression in:
* PTa in I,II, or III
* Coronary artery teritory
* RCA
58
What is a CM5 ECG configuration?
CM5 detects 89% of ST-segment changes due to left ventricular ischaemia. (Right arm electrode on manubrium, left arm electrode on V5 and indifferent lead on left shoulder).
59
What is a CB5 ECG confirguration?
CB5 is useful in thoracic anaesthesia. Right arm electrode over the centre of the right scapula and left arm electrode over V5.
60
What ppoFEV1/ppoTLCO should prompt for further investigations.
Less than 40%
61
A patient undergoing pneumonectomy has a ppoFEV1 less than 40%, which investigation is most appropriate?
CPET
62
What is the cut off VO2 Max on CPET for pneumonectomy?
Less than **15 ml/kg/min** would be of concern
63
Grades of AS
* Mild: area \< 1.5cm2, gradient \< 25 mmHg
* Moderate: 1-1.5cm2, gradient 25-40 mmHg
* Severe: \< 1cm2, gradient \>40 mmHg
* Critical: area \< 0.6cm2, gradient \> 70 mmHg
64
What is the blood supply to the sino-atrial and atrio-ventricular nodes?
* SAN - 2/3rds by right coronary
* AVN - Majority by right coronary
