COINDUCTION OF ANESTHESIA - THE CARDIAC PATIENT

Cardiac patients pose special problems to the anaesthetist because of their underlying disease and the nature of the corrective surgery. Inf ormation about new methods of induction of anaesthesia obtained in fit patients may not be applicable directly to patients with heart diseas e. More suitable are patients undergoing cardioversion. Titrating intr avenous induction agents to response elicited appears to be more impor tant than the agent used, although it is possible to inject too slowly with drugs whose offset of action is by distribution. Anaesthetic age nts alone are not sufficient to ablate the response to tracheal intuba tion, skin incision and sternotomy. Balancing induction of anaesthesia with small doses of opioid can obtund the haemodynamic responses. The effects of a drug used solely for induction of anaesthesia are unlike ly to be present at the end of 3 or 4 h of surgery However, this is no t the case with agents used to maintain anaesthesia if early extubatio n after anaesthesia is practised. Reports of anaesthetic techniques fo r cardiac surgery tend to give total doses used rather than the timing and dose of the constituent agents. At Papworth Hospital, Cambridge, UK, after opioid premedication, midazolam sedation is used during inse rtion of some, or all, vascular cannulae. Two main techniques then exi st. Either an intravenous or volatile anaesthetic agent is started imm ediately, supplemented by an opioid and muscle relaxant, or anaesthesi a is induced with opioid and relaxant and the anaesthetic agent is beg un only after transfer to the operating theatre, just before skin prep aration. Either way, the end-point of induction of anaesthesia is diff icult to discern in heavily premedicated patients with midazolam sedat ion.