Management of anaesthesia, perfusion and supportive care during open intracardiac operations and extracorporeal circulation.

In selecting an anaesthetic agent the goal must be to provide anaesthesia with the least derangement of the normal physiological processes. This is attained by utilising the lightest levels of anaesthesia consonant with the surgical procedure. Since intracardiac surgical procedures do not require deep anaesthesia, amnesic and analgesic levels of anaesthesia that interfere least with the normal compensatory mechanisms of the patient may be employed. Strict observance of the principles of good anaesthesia is much more important than the selection of agent or technique. It is advantageous to eliminate spontaneous respiration by manual hyperventilation, by intravenous use of relaxants, or by both means, rather than by deep anaesthesia, since the latter would result in a greater depression of the myocardium and medullary vasomotor centre. Previous experience should dictate the choice and dosage of premedicant drugs. The advantage of heavy premedication is reduction of the metabolic rate, whereas light premedication preserves homeostatic mechanisms to a greater extent. We take the intermediate position, that of moderate premedication. Pentobarbitone sodium, 1 or 2 mg per pound of body weight, is given orally or rectally respectively 2 hours pre-operatively. Morphine sulphate, 1 mg per 10 pounds, is given intramuscularly 1 hour before operation. Belladonna drugs are not given. This omission has not resulted in an increase of endotracheal secretion or vagal reflexes. There is ample evidence that a variety of anaesthetic agents and techniques have proved to be satisfactory (Gain, 1957; Matthews et al., 1957; Mendelsohn et al., 1957; Patrick et aL, 1957; Bourgeois-Gavardin et al., 1958; Keats et aL, 1958; Norlander et al., 1958; Musicant et aL, 1959). As a general principle, first choice must be the agent and technique with which the individual anaesthetist is most familiar. Myocardial depression and dilatation of the peripheral vascular bed are pharmacological properties common to all anaesthetic agents. The degree of these effects is proportional to the depth of anaesthesia. While it is of considerable importance that the level of anaesthesia be kept as light as possible, it is probably of no importance which agent is used.