Sedation - Analgesia

All Cardiac Surgical patients unless otherwise specified

• Most adults arrive from theatre on a Propofol infusion with the aim being to have the patient extubated within 6 hours.
• On arrival from theatre, the infusion rate should be reduced to 15mls per hour.  The patient should be kept sedated with Propofol 5-25ml/hr until:
• Core temperature > 36°C
• Haemodynamically  stable
• Chest drainage < 150ml/hr
• As soon as the patient has met the criteria, the infusion should be stopped, not reduced.
• Morphine 1-3mg increments are given as primary analgesia.  Morphine is also useful in managing hypertension (may be associated with pain or vasoconstriction)
• Midazolam should not be given to patients on Propofol and infusions.  If a patient is not in pain but is adequately sedated, give a bolus of Propofol and increase the infusion rate.

Patients must be ADEQUATELY sedated if paralysis is indicated for

• Difficult ventilation
• Shivering
• Gross haemodynamic instability
• Chest re-opening

Shivering

 
Shivering may occur in the post-op re-warming phase particularly after high dose Fentanyl anaesthesia.  It is potentially harmful in severe cases as shivering will increase peripheral oxygen consumption and will generate CO₂ production thereby increasing acidosis.

Management

• Give bolus of sedation – usually Propofol 1-3ml (may cause hypotension)
• Give bolus of morphine 1-3mg

If shivering continues:

• Give slow bolus of pethidine 25-50 mg IV (may cause hypotension via vasodilation)

If shivering continues:

• Give bolus IV rocuronium 15-25 mg (non depolarising muscle relaxant)

Valsalva Response when Initially emerging From anaesthesia

 
Often when the patient first begins to emerge from sedation (may not even appear to be awake at this point) the increase in intrathoracic pressure may be enough to cause this phenomenon.

Assessment

• Difficult to ventilate, high rate and airway pressures
• Profound hypotension
• High filling pressures
• Relative bradycardia (NOT always)

This situation may mimic acute low output state caused by cardiac tamponade

Management

1. Sedate (Propofol or morphine bolus)
   Once adequately sedated the intrathoracic pressure should decrease and the blood pressure stabilise if vagal response is the primary problem.
2. Paralyse if unresponsive to sedation
   Give rocuronium 15-25mg stat and ensure ventilation
3. Volume load if hypovolaemic
4. Consider reducing PEEP if > 5cm H2O
5. Notify Surgeon and IC Specialist if hypotension persists despite above actions
6. Prepare to reopen urgently

Anaesthetic drugs to be used during emergency chest reopening

 
Sleep inducing agents

 
Muscle Relaxants

​