Principles of Cardiac Anaesthesia

Cardiothoracic surgery has the anaesthetist and surgeon sharing the circulation. Anaesthetic management of the circulation needs to adapt dynamically to surgical requirements.

This covers the general considerations of cardiac anaesthesia except those relating to cardiopulmonary bypass, which are covered here.

Goals are to prevent decompensation by avoiding:

Preoperative Evaluation

Note that the phrase ‘open-heart’ means surgery where the cardiac chambers are opened, and so includes most cardiac operations, with the notable exception of CABG.

Basics:

  • Planned operation
  • Age, weight, and height
    For indexing and drug doses.

History:

  • Allergies
    Particularly:
    • Heparin
    • Protamine
      Seafood.
    • Iodine
    • Antibiotics
  • Preoperative medications
    • Cease antiplatelets prior:
      • Clopidogrel 5-7 days
      • Tirofiban 1-2 days
      • Streptokinase 3 hours
    • Heparin
      May be continued into the anaesthetic bay.
    • Continue beta-blockers
      Consider initiating if not already instituted.
    • Stop ACE-Is
    • Continue statins perioperatively
  • Exercise tolerance
  • Co-existing disease
    Cardiac patients tend to be sicker. Particularly relevant features:
    • COAD and smoking history
      Smoking cessation should be encouraged.
    • Hypertension
    • Valvular disease
    • Coronary artery disease
    • Cerebrovascular disease
    • Peripheral vascular disease
      Affects graft sites and arterial line placement.
    • Cognitive function
      Baseline level of impairment.
    • DM
      Associated with poorer outcomes.
    • CKD
      Associated with poorer outcomes.
    • Dysphagia or oesophageal problems Affects use of TOE.
  • Previous cardiac surgery
    Re-do sternotomy is associated with substantial additional risk:
    • Pericardium is usually obliterated
    • RV or innominate vein may be adherent to sternum
      Risk of massive haemorrhage due to sternal saw.
    • Internal paddles may not be able to be applied
      External defib pads should be used.
    • Peripheral bypass (femoral) may need to be established
    • Significantly prolonged case with substantial blood loss
      Dissection of adhesions and identification of old grafts.
  • Contraindications for echocardiography
    Ask about swallowing disability.
    • Absolute
      • Perforated viscous
      • Oesophageal stricture/tumour/diverticulum
      • Active upper GI bleed
    • Relative
      • Neck/mediastinal radiation
      • Atlantoaxial disease
      • Dysphagia
      • Odynophagia

Examination:

  • Vital signs
  • Airway assessment
  • Respiratory and CVS exam
  • Peripheral and central vascular access sites

Investigations:

  • Bloods
    • FBE
    • UEC/
    • Coagulation profile
    • G+H +/- crossmatch
  • General
    • ECG
    • CXR
    • PFTs if indicated by respiratory disease
  • Cardiac-specific
    • Angiogram
      • Number, site and severity of stenoses
      • Left main or equivalent stenosis
    • Echocardiogram
      • LV function
      • RV function
      • Valvular function

Preparation

Premedication:

  • Highly stressful period
  • Stress may lead to myocardial ischaemia
  • Consider:
    • Lorazepam 2mg
      Night prior and on call to OT.
    • Morphine 5-10mg or oxycodone 10-20mg PO
      On call to OT.

Lines and monitoring:

  • 5-lead ECG
  • SpO2
  • Arterial line and large bore cannula
    Should be placed awake and on the right side if surgeons are not planning on using this vessel.
    • Left sided arteries and vessels lie closer to the sternum
      Damage to left innominate vein will render any left upper limb venous access useless.
  • Consider external defibrillation pads for:
    • Re-do cases
    • High risk arrhythmia
      Includes:
      • Ischaemic emergencies
      • Critical left main
    • Modified access
    • Deactivated AICD
    • Removal of PPM leads
  • Consider awake central access in sick or unstable patients
    MAC lines are excellent choice for volume as well as providing a route of administration of centrally acting drugs.
  • Pulmonary artery catheter
    • Indication varies depending on centre; strong indications include:
      • Severe LV dysfunction (EF ⩽30%)
      • MV dysfunction
      • AKI
    • Floating after induction preferable in patients with:
      • Severe AS
      • Left main/left main equivalent
      • Conduction deficits (BBB))
  • Consider hot line for small patients or those with high risk of bleeding
  • Use of TOE
    • ~5% of the time an unexpected abnormality will be identified

Drugs (Push):

  • 2% lignocaine in 3ml syringe with 25G needle for vascular access
  • Midazolam 5mg in 5ml
  • Fentanyl 500ug-1mg in 10-20ml syringe
  • Induction agent
    Propofol 200mg in 20ml (can use syringe driver if required), thiopentone 500mg in 20ml.
  • Cephazolin 2g
  • Vasopressor
    e.g. Metaraminol 10mg in 20ml.
  • Rocuronium 100mg in 2x5ml
  • Heparin
    • 300 units/kg if heparin naïve
    • 400 units/kg if has been on heparin or enoxaparin preoperatively

Drugs (Infusions):

  • TXA 5g in 50ml
  • Propofol 500mg in 50ml
  • +/- Noradrenaline 3mg in 50ml
  • +- GTN 6mg in 50ml

Induction

Induction:

  • Don’t induce unless:
    • Surgeon capable of instituting CPB present
    • Perfusionist present
  • Aim is a haemodynamically stable induction
    • No myocardial depression
    • No autonomic response
    • No change in SVT
    • Most inductions are equivalent, with the exception desflurane and ketamine
  • Typical doses
    • Fentanyl 5-10ug/kg
      Up to 100ug/kg may be given over the course of the case in some centres.
    • Midazolam 0.05mg/kg
    • Propofol
      Classically reduced doses; e.g. ~0.25-0.5mg/kg.
  • Antibiotics prior to skin incision

Intraoperative

Position:

  • Head ring
  • Leg padding
  • Place head frame
  • Arms positioned
    Tucked if not used for grafts.

Sternotomy:

  • Highly stimulating - requires re-dose of analgesia
    e.g. 250μg fentanyl.
  • Cease ventilation with ZEEP prior to sternotomy
    Prevents surgeon from damaging lung.
    • Lungs may be left on during resternotomy to protect the other cardiac structures

Postoperative

ICU Handover:

  • Should be formulaic

References