Peri-op Management of Heart Transplantation

 

The transplanted heart

 

Physiology:

Summary

·      Preload-dependent

·      Slow response to pain

·      Slow response to blood loss

·      Absence of angina

Autonomic systems

·      PSNS: absent

·      Neural SNS: absent

·      Humoral SNS: present

Heart rate

·      Resting: ↑ (90-100)

·      Max: ↓

·      Variability: ↓

Slow response to

·      Pain

·      Hypovolaemia, hypotension

·      Exercise

Absent responses to

·      Carotid sinus massage

·      Valsalva

Atrial dysfunction

·      Asynchrony

·      Filling impairment

·      AF and AFL in 25%

Preserved autoregulation

·      Coronary autoregulation

·      Heterometric autoregulation (Frank-Starling)

 

Pharmacology:

↑Response to catecholamines
(upregulation)

·      Adrenaline

·      Noradrenaline

·      Dobutamine

·      Isoprenaline

↓Response to indirect acting pressors

·      Ephedrine

Response to direct acting pressors

(why not increased??)

·      Metaraminol

·      Phenylephrine

↓Response to anti-muscarinics

·      Atropine

·      Glycopyrrolate

Beware negative chronotropes

·      Beta blockers

·      Calcium channel blockers

·      Neostigmine

 

Anaesthesia for transplant recipients:

 

Assessment:

Goals

·      Function of transplant?

·      Severity of comorbidities?

·      Severity of present illness?

·      Urgency of surgery?

History/Exam/Tests

·      Function of transplant

o  Details regarding surgery

o  History of rejection

o  Exercise capacity (DASI)

o  Recent echo

·      Severity of comorbidities

o  Accelerated coronary artery disease

o  Arrhythmia

o  HTN

o  T2DM

o  CKD

o  CLD (liver)

o  Cytopaenias

o  Cancer

·      Severity of present illness

o  End-organ dysfunction

o  Volume status

·      Urgency of surgery

o  Discussion with surgeon

Specific tests

·      Blood tests:

o  FBE, UEC, LFT, coag, lactate

·      ECG:

o  Signs of Tx: double P wave, 1st degree AV block, RBBB

o  Signs of IHD

·      PPM/AICD interrogation

o  PPM dependence

o  Response to magnet

Optimisation

·      Medications plan:

o  Immunosuppressants

o  Anticoagulants

o  Antihypertensives

·      Fluid resuscitation

o  Preload-dependent

Planning

·      Discussion

o  Transplant centre

o  Local cardiology

o  Local ICU

·      Decision:

o  If urgent and low risk: proceed

o  If non-urgent and high risk: transfer

o  If in between: depends on discussion and goals

 

Anaesthesia:

Goals

·      No cardiovascular collapse

·      No myocardial ischaemia

·      No infection (wound, lines)

Preparation

·      Access:

o  Strict asepsis

o  Avoid IJ CVC (facilitate future biopsies)

·      Personnel:

o  Second anaesthetist if complex

·      Monitoring

o  5 lead ECG

o  Low threshold for arterial line

·      Drugs:

o  Metaraminol for infusion (0.5mg/mL)

o  Adrenaline for boluses (10mcg/mL)

o  Adrenaline or isoprenaline for infusion

Induction

·      IV fluid bolus 10mL/kg

·      Midazolam 0.025mg/kg

·      Fentanyl 5mcg/kg

·      Propofol 2mg/kg

·      Metaraminol infusion at 5mg/h

·      Low threshold for small adrenaline boluses

·      Antibiotic 30-60 mins pre-incision

Maintenance

·       

Emergence

·      No myocardial ischaemia

o  Deep extubation if safe

o  Plenty of opioid if extubating awake

Post-op

·      Consider ICU/HDU monitoring

 

 

 

Heart transplantation itself:

 

Indications:

Clinical

·      NYHA 3,4 heart failure (dilated > ischaemic > congenital > other)

·      Refractory arrhythmia

·      Refractory angina

Testing

·      VO2peak <12mL/kg/min

·      Severe LV systolic dysfunction

Scores

·      Heart failure survival score medium-high risk

·      Seattle heart failure survival model at 1 year <80%

Goldilocks timing

·      Too early: pointless and wasteful

·      Too late: dangerous

 

Contra-indications:

Absolute

·      Severe kidney disease (CrCl <40)

·      Severe liver disease (BR >50)

·      Severe lung disease (FEV1 < 1L)

·      Severe pulmonary vascular disease (PASP >60mmHg or PVR >4)

·      Severe psychological problems (expect non-compliance)

Relative

·      Uncontrolled diabetes (HbA1c >7.5%)

·      Obesity

·      Substance abuse

·      Cancer

·      Blood-borne virus

·      Systemic infection

 

Ideal donor:

Demographics

·      Young

·      Sex match

·      Race match

·      Body size match

Health

·      Normal heart

·      Normal pulmonary vasculature

·      Normal lungs

·      Normal kidneys

·      No substance abuse

·      No infection

·      (And total ischaemic time <4 hours)

 

Ventricular assist devices:

Benefits

·      Allow exercise

·      Allow weight gain

·      Improved organ function (esp kidneys)

*Almost half of transplant recipients were bridged with a VAD*

Risks

·      Infection

·      Thrombosis

·      Malfunction

·      RV failure

Peri-op consideration

·      Record the settings

·      ↑Risk of bleeding because:

o    Re-sternotomy

o    Acquired coagulopathy (incl vWF deficiency)

 

Investigations:

CPET

·      VO2peak (<12 gets transplant, note underestimated in the obese)

·      VEVCO2 (strongest predictor)

RHC

·      Direct: CO, SvO2, RAP, RVP, mPAP, PASP, PADP, PCWP

·      Indirect: PVR, TPG, DPG

*If severe PHTN, then donor RV won’t cope*

 

Anaesthesia:

Goals

·      No arrest at induction

·      No awareness

·      No bleeding to death

·      No clotting to death (bypass)

Pre-induction

Medication:

·      Reverse anticoagulation (Vit K, PCC, FFP)

·      Continue pulmonary vasodilators

·      Continue inotropes

·      Immunosuppression (glucocorticoid, azathioprine etc) – d/w home team

·      Antibiotic prophylaxis

 

Fluid:

·      Crystalloid resuscitation

·      Blood crossmatch

 

Access:

·      Big peripheral IV

·      Arterial line

·      CVC with PAC

 

Monitoring:

·      TOE

·      NIRS

·      BIS

 

Pacing:

·      Reprogramme AICD/PPM:

o  Deactivate shock and anti-tachy

o  Activate DOO

·      Apply external defib pads

 

VAD:

·      Note settings

Induction

Goals:

·      Maintain heart rate

·      Maintain contractility

·      Maintain afterload

·      Maintain preload

·      Maintain normal O2 and CO2

Drugs:

·      Midazolam 1-5mg

·      Fentanyl 2-4mcg/kg

·      Propofol 0-1mg/kg

·      Rocuronium (fast onset)

·      (can substitute etomidate for propofol)

Going on bypass

·      Withdraw PAC

·      Clamp VAD outflow graft (surgeons)

Coming off bypass

·      LV and RV function

·      Anastomosis sites

·      Air in LV apex

·      Flow through pulmonary veins

Post-op

Homeostasis:

·      Oxygenation

·      Ventilation

·      Blood volume

·      Heart rate (80-100)

·      mAP

·      mPAP and PVR (Rx milrinone, iNO, PDE5i, PGI2)

·      Temperature

·      Acid-base

Watch out for:

·      Signs of tamponade

·      Signs of RV failure

·      Arrhythmia

Other complications:

·      Primary graft dysfunction

·      Secondary graft dysfunction

·      Cardiac allograft vasculopathy

·      Drug nephrotoxicity

 

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