Anaesthesia for the Patient with a Cardiac Transplant
The curriculum is generic here, asking for knowledge of 'the anaesthetic management of patients with transplanted organs for non-transplant surgery '.
This topic appeared as a CRQ in September 2024, with marks lost on the 'action of drugs on a denervated heart, the cardiovascular conditions a transplanted heart develops and the physiological properties of a denervated heart '.
Physiological differences
There is a relatively high (90 - 100bpm), fixed heart rate due to interrupted autonomic innervation
The heart rate is determined by the donor heart atrium
Increases in cardiac output therefore come from increased SV
Preload optimisation is thus important to combat anaesthesia-induced vasodilation
Changes in heart rate are not an indicator of depth of anaesthesia/analgesia
There are delayed chronotropic responses to normal stimuli
Dysrhythmias are more common
50% of patients will have an atrial arrhythmia
5% will have a permanent pacemaker
There is no baroreceptor reflex; hypotension does not trigger tachycardia
Carotid sinus massage is ineffective for treatment of supraventricular tachycardias
Laryngoscopy will not cause a tachycardic reflex
Pneumoperitoneum will not cause a bradycardia
Pharmacological differences
No effect from vagolytics e.g. atropine or glycopyrrolate
No effect from indirectly acting sympathomimetic agents e.g. ephedrine
Increased sensitivity to:
Endogenous catecholamines/directly-acting sympathomimetics e.g. noradrenaline, adrenaline
Adenosine - need to reduce the dose e.g. 1mg rather than 3mg
GTN - no reflex tachycardia
Suxamethonium / neostigmine - no bradycardia
Reduced efficacy of digoxin in controlling atrial arrythmias
Dopamine - reduced efficacy
Immunosuppression
Immunosuppressive agents reduce the incidence, and severity, of rejection episodes
Regimens typically include triple therapy:
Steroids e.g. prednisolone - impair IL-1 metabolism and therefore interfere with antigen presentation
Anti-metabolites e.g. azathioprine, mycophenolate - prodrugs which impair lymphocyte proliferation by reducing nucleotide synthesis
Calcineurin inhibitors e.g. cyclosporin, tacrolimus - inhibit T-cell function by reducing IL-2 transcription
Immunosuppressive drugs have a variety of side-effects that may be present
Immunosuppressives should be continued up until the time of surgery
If the normal route of administration is impaired, the transplant team should be contacted on advice as to how to circumvent this
Long-term sequelae of heart transplant
Chronic allograft vasculopathy
There is accelerated coronary atherosclerosis (50% of patients by 5yrs)
Thought to be due to a chronic rejection mechanism
Patients may have silent cardiac ischaemia i.e. painless ischaemic due to denervation
Malignancy, esp. skin cancers, due to immunosuppression
Side-effects of immunosuppressive agents:
Renal failure
Diabetes mellitus
Hypertension (90%)
Opportunistic infections e.g. PJP
Anaemia
Perioperative management of the patient with a heart transplant
Pre-operative
Full history of transplant, immunosuppressive regimen, transplant team
Screen for comorbidities e.g. coronary vascular disease, diabetes, renal failure, hypertension
Rejection, which can be hyperacute, acute or chronic, should be excluded if there is functional deterioration of the transplanted organ
Bloods: U&E, LFT's, glucose/HbA1c, as side-effects of immunosuppressive drugs
ECG
TTE to assess graft function
CMV status to help determine need for CMV negative blood
Consider need for more robust cardiovascular testing e.g. stress echo ± cardiac catheterisation
Early involvement of the patient's transplant team is vital
Continue immmunosuppressive drugs up until the morning of surgery
Ensure parenteral preparations of necessary immunosuppressives are present in case oral route unavaiable perioperatively
Drug level monitoring as concentrations may be increased/decreased through drug-drug interactions
Ensure first on the list or surgery timed so as to minimise interruptions in dosing regimen
Intra-operative
AAGBI as standard
Arterial line
If CVC is required, avoid RIJ as the patients have repeated cardiac biopsies via RIJ due detect chronic rejection
Urinary catheter to monitor fluid balance
Aim for normovolaemia or even mild hypervolaemia prior to induction due to dependence on SV for increased cardiac output
Maintain CPP and avoid hypotension; ensure adequate afterload
Avoid pro-arrhythmogenic states e.g. disordered acid/base, dyselectrolytaemia, hypo/hyperthermia, hypoxia, hypo/hypercarbia
Ensure directly acting inotropic drugs are available, as well as an external pacemaker
Strict asepsis is necessary for all procedures, owing to the greater risk of infection in the immunosuppressed patient
Avoid nasogastric or nasotracheal interventions as these might cause bacteraemia
Patients may be taking prophylactic anti-microbials, which should be continued
Ensure appropriate perioperative steroid dosing
Antibiotic prophylaxis as indicated
Temperature management
Appropriate perioperative VTE prophylaxis
Post-operative
Further liaison with transplant team regarding immunosuppressive management and Abx therapy
Normal post-operative multi-modal analgesia, but avoiding NSAIDs
Remove exogenous lines, drains and tubes as soon as possible to avoid infection