Cardiac Flashcards
Formula for ppoFEV1?
Pre-operative FEV1 x (19-number of segments to be resected)/19
Pre-op FEV1 x (remaining segments/total functioning segments)
Constituents of CARDIOPLEGIA?
JCUH uses:
- Potassium - 20mmol
- Procaine
- Magnesium
Potential for: Calcium Mannitol Bicarbonate/Histadine Aspartate Glutamate Adenosine
What dose of KCl in cardioplegia?
How does it work?
20mmol
Inactivates fast Na channels which decreases resting membrane potential preventing the upstroke of the cardiac action potential
Myocardium becomes un-excitable and arrests
What does calcium do in cardioplegia?
At a low dose - to reduce the amount available for contraction
Maintains cell membrane integrity
What does Magnesium do in cardioplegia?
Prevents loss from cells
Maintains role as enzymatic co-factor
Competes with Ca to decrease Ca induced contraction
Role of mannitol in cardioplegia?
Raises osmolality which means decreased tissue oedema
Role of Bicarbonate/Histadine in cardioplegia?
Offset metabolic acidosis caused by ischaemia
Role of Procaine in cardioplegia?
Decreases excitability/conduction/reduction of arrhythmia at reperfusion
Describe the route(s) of administration of cardioplegia solution
- Antegrade - cannula in aortic root/coronary ostium
- Retrograde - cannula in coronary sinus and perfuses backwards; may not reach RV well
Usually a bit of both every 15-20 minutes
Complications of cardioplegia?
- Direct damage to myocardium from cannulae
- Failure to attain widespread cardiac perfusion (e.g. RV)
- Myocardial oedema, haemorrhage and injury
- Incorrect composition
- Arrhythmias
- Fluid overload
- Reperfusion injury
What are the benefits of using blood cardioplegia vs crystalloid cardioplegia?
Blood has: O2 carrying capacity [Hb is usually 5]; pO2 on L side of OHDC H+ buffer O2 free radical scavenging Delivery of other nutrients Reduced myocardial oedema Improved micro vascular flow
When do you perfuse your coronary arteries?
Well, that depends… on L or R or if branch is supplying atrial or ventricular myocardium
Mainly during diastole for Left coronary arteries BUT some is throughout the cardiac cycle (e.g. RCA)
What is normal coronary blood flow?
250ml/min
Or 5% of CO
List 3 different types of resp and cardiac function tests for pneumonectomy
FEV1/PPOFEV1 >2L (or more than >30% PPO value); if <30%, need CPET
Diffusion capacity - DLCO >30%
CPET >11ml/kg AT
VO2 Max >20 ideally
List 3 lung protective strategies when doing OLV
Vt 6ml/kg of IDEAL body weight Peak pressure <30cmH2O FiO2 to keep SpO2 94-98% Aim for normal PaCO2 Plateau pressure <24cmH2O PEEP at 5cmH2O Avoid hYPERoxia
What is the final test that is done (intra-op) to assess patient suitability for pneumonectomy?
Clamping of ipsilateral pulmonary artery: resulting in shunting of blood supply into non-operative lung
Done for ALL patients
What are the adverse physiological responses to pulmonary artery clamping that would make the team reassess whether to continue with pneumonectomy?
CVS instability or excessive rise in CVP
Hypoxia despite FiO2 1.0
List 4 possible post op complications SPECIFIC to a pneumonectomy
Arrhythmias - 40% develop AF
Post pneumonectomy pulmonary oedema
Broncho-pleural fistula
Cardiac herniation
Symptoms of severe AS?
Angina
Syncope
Shortness of breath
What specific cardiac investigations may be used to assess AS
ECHO - LV contractility
Angiogram - to assess need for grafting at the same time
ECG - for ischaemia or LVH
In SEVERE AS, what are the values for:
- Peak aortic flow velocity
- Mean pressure gradient
- Valve area
- 4m/s
- > 50mmHg
- 0.6cm2/m2/BSA
(Normal velocity of any blood flow in the body is 1m.s)
Describe the pathophysiological features of Aortic Stenosis
- Valve stiffens -> progressive decrease in aortic valve area
- Increased LV afterload
- Compensatory LV hypertrophy
- Early diastolic dysfunction
- Decreased compliance with increased LVEDP
- Late systolic dysfunction
- Decreased systolic contractility and SV
- Heart failure and ischaemia
List the haemodynamic goals for intraoperative management of AS
Avoid arrhythmias Avoid tachycardia (maintain adequate diastolic time) Maintain afterload (maintain normal to high SVR) Maintain pre-load/euvolaemia Maintain SpO2 >94% Normothermia Maintain Hb
List the ways in which Dilated Cardiomyopathy may present
Sudden death
Increasing shortness of breath/LV failure
Embolism
List the pharmacological treatments for DCM
Beta blockers Diuretics ACEi Aldosterone antagonist Anti-coagulants (as stasis in LV increases risk of LV clot)
List NON-pharmacological treatments for DCM
LVAD
ICD
L ventriculotomy
Heart transplant
List predictors of poor outcome in DCM patients undergoing surgery
LVEF <20%
Elevated LVEDP
LV hypokinesia
Non-sustained VT
What are the haemodynamic goals when anaesthetising a DCM patient?
Avoid arrhythmias Avoid tachycardia Maintain preload Maintain afterload Avoid myocardial depression
How would you achieve your haemodynamic goals for a DCM patient?
Choice of anaesthetic - regional vs GA Control arrhythmias Arterial line Fentanyl heavy GA Low dose peripheral vasoconstrictor infusion
Define Pulm HTN
PASP >25mmHg at rest
>30mmHg on exercise
(On R heart catheterisation)
List the 5 classifications of Pulmonary HTN
- Idiopathic PAH
- LV disease
- Lung disease
- VTE
- Misc - e.g. sarcoidosis
How does pulmonary hypertension cause R heart failure
Raised Pulm artery pressure requires increase from RV
RV hypertrophy
Increased O2 demand
RV dilates, decreasing contractility and output
L septal shift and decreased LV compliance
What drugs would you use to treat CHRONIC pulmonary HTN?
Prostacyclins - Flolan/iloprost
Endothelin receptor antagonists - Bosentan
Phosphodiesterase V inhibitors - sildenafil
Nitric Oxide
Calcium channel blockers
What factors increase PVR?
Hypoxia Acidosis Pain Hypercapnea Hypothermia PEEP
What surgical options are there for Pulm HTN?
Lung transplant
Pulmonary endarterectomy for VTE
What is the normal innervation of the heart?
Vagus nerve - CN X
T1-T4 of spinal cord post-ganglionic cardiac accelerator fibres from cardiac plexus
List the alterations in physiology in the transplanted heart
Resting tachycardia due to loss of vagal tone
No response to DIRECT autonomic influence or drugs that act via ANS (e.g. atropine)
Absent rate response to baroreceptors - no Valsalva response/carotid sinus stimulation/hypovolaemia/light anaesthesia
Stimulated only through direct acting agents such as catecholamines
Absent sensory innervation - silent MI
SV is pre-load dependent, therefore need to maintain filling pressures
PPM or pacemaker wires will be present - avoid RIJ
No catecholamine stores in the myocardium = decreased response to ephedrine
What concerns do you have when anaesthetising a patient with a heart transplant for non-cardiac surgery?
Physiology - denervation of orthoptic heart
Defib/PPM presence
Problems with rejection
Complications of transplant - leaky valve/conduction defects
Immunosuppression and its complications
Infection
Difficult IV access
Close monitoring pre-, intra- and post-operative
ECG will show double P wave (?)
Risk of silent MI
What drugs are used for immunosuppression following heart transplant?
Steroids
Calcineurin antagonists - cyclosporin and tacrolimus
Antiproliferative drugs - MMF
What are the implications of immunosuppression for perioperative care of the patient with a heart transplant?
Renal impairment
Hepatic impairment
Need to ensure immunosuppression still delivered
Steroids require supplementation to account for stress response
Pre-op blood essential for renal function/LFTs
Strict asepsis
Abx prophylaxis
Dyslipidaemia
HTN
Diabetes
Calcineurin inhibitors enhance the effect of NMBD
Skin malignancy
List some long term health problems in the patient with a heart transplant
Chronic rejection Renal impairment/failure Hepatic impairment/failure Skin malignancy Diabetes Infection Sarcoidosis Amyloidosis
What are the indications for pneumonectomy?
Trauma with uncontrolled haemorrhage
Bronchial carcinoma
Chronic infection - TB/fungal
Pneumonectomy is incredibly aggressive, so lobectomy is much preferred
List the central neurological complications of ON-PUMP cardiac surgery
Stroke
Post op cognitive impairment
Fatal brain injury
Seizures
Visual field defects
Focal spinal cord injury: paraplegia/spinal stroke
Type 1 = actual brain injury (e.g. stroke); Type 2 = delirium
List the peripheral neurological complications of ON PUMP cardiac surgery
Brachial plexus injury
Saphenous nerve injury
Phrenic nerve injury
Anterior intercostal nerve injury
What are the patient specific risk factors for the central neurological complications after cardiac surgery?
Older age >65 Female>male Diabetes LVSD Previous CVA AF PVD - atheromatous aorta Low CO state post op
What are the procedural factors for central neurological complications after cardiac surgery?
Valve surgery (multivalve>mitral>aortic replacement) +/-CABG
Re-do or emergency surgery
Cannulation of atheromatous proximal aorta
Intra-operative hyperglycaemia
Poor temperature control
Deep hypothermic circulatory arrest (when required for the surgery)
List the monitoring that could be used to reduce the incidence of POCD
Transcranial Doppler
NIRS
BIS
Cerebral oximetry
How can hypothermia be neuroprotective?
Reduce CMRO2 (7% decrease for every 1 degree fall)
Attenuates neuroinflammatory response
Reduce apoptosis
Inhibit free radical generation
List some methods to reduce the incidence of neurological complications
TOE checking for atheromatous aorta prior to cannulation
Use high quality line filters
Avoid hyperthermia
Avoid multiple cross clamp of aorta
Close glycaemic control
Maintain cerebral perfusion
Use NMDA antagonist (Mg, lidocaine) for pharmacological neuroprotection
Use alpha stat (which is default for adults anyway)
How do you confirm a (LEFT) double lumen tube is placed correctly?
Insert the DLT to the L side
Attach Y connector
Sealing caps closed
Inflate tracheal cuff - ventilate both lumens and check for CO2 etc
Ventilate via endobronchial lumen by occluding tracheal lumen of Y connector; listen for air leak when you have opened cap on tracheal side and deflated tracheal cuff (check CO2, chest movement/auscultation)
Ventilate via tracheal lumen by occluding the bronchial lumen of Y connector; listen for air leak (after opening cap of bronchial lumen)/observe chest movement/auscultate
What may be different with a right sided DLT?
Need to think about the RUL and having an eye to ventilate the RUL
Outline the possible complications associated with the use of double lumen tubes
Damage: anything that gets in the way… Teeth/lips/tongue/pharynx/trachea/carina/palate Arytenoid cartilage & cords Eye Mucosal sloughing Hypoglossal and lingual nerves Oesophagus
What size DLT would you use in a man? A woman?
39 for men
37 for women
Name some complications from using a DLT
Failure to ventilate Diffuse fibrosis of glottis Emphysema (subcutaneous) Pneumothorax Endobronchial aspiration Laryngeal obstruction Vocal cord paralysis Submucosal haemorrhage
What can you use if you cannot get the DLT in place?
Single lumen tube and bronchial blocker
Use fibreoptic scope to check placement of bronchial blocker
How would you manage the development of hypoxaemia during OLV?
Increase FiO2 to 1.0
Inform the surgeon
Apply PEEP/adjust PEEP to ventilated lung
Oxygen insufflation to non-ventilated lung (without using PEEP etc)
Ventilate both lungs/intermittent two lung ventilation
Optimise cardiac output
Optimise Hb
What factors can lead to the development of high airway pressures during OLV?
Bronchospasm
Obstruction of the ETT by sputum/blood
Malposition of DLT (e.g. missing out RUL) - use scope to reposition
Malposition of bronchial blocker - use scope to reposition
Pneumothorax of ventilated lung