Alveolar recruitment strategy improves arterial oxygenation after cardiopulmonary bypass

Atelectasis occurs during general anaesthesia. This is partly responsible for the impairment of gas exchange that occurs peri-operatively. During cardiopulmonary bypass, this atelectasis is exacerbated by the physical collapse of the lungs. As a result, poor arterial oxygenation is often seen postoperatively. We tested the effect of an 'alveolar recruitment strategy' on arterial oxygenation in a prospective randomised study of 78 patients undergoing cardiopulmonary bypass. Patients were divided equally into three groups of 26. Group 'no PEEP' received a standard post bypass manual lung inflation, and no positive end-expiratory pressure was applied until arrival at intensive care unit. Group '5 PEEP' received a standard post bypass manual inflation, and then 5 cmH2O of positive end-expiratory pressure was applied and maintained until extubation on intensive care. The third group, 'recruitment group', received a pressure-controlled stepwise increase in positive end-expiratory pressure up to 15 cmH2O and tidal volumes of up to 18 ml x kg(-1) until a peak inspiratory pressure of 40 cmH2O was reached. This was maintained for 10 cycles; the positive end-expiratory pressure of 5 cmH2O was maintained until extubation on intensive care. There was a significantly better oxygenation in the recruitment group at 30 min and 1 h post bypass when compared with the no PEEP and 5 PEEP groups. There was no significant difference in any of the groups beyond 1 h. Application of 5 cmH2O positive end-expiratory pressure alone had no significant effect on oxygenation. No complications due to the alveolar recruitment manoeuvre occurred. We conclude that the application of an alveolar recruitment strategy improves arterial oxygenation after cardiopulmonary bypass surgery.

No response to trigger agents in a malignant hyperthermia-susceptible patient

Malignant hyperthermia susceptibility is an inherited disorder, where a life-threatening condition can result from exposure to a trigger agent or agents. Succinylcholine and volatile anaesthetic agents are well established to be trigger agents in anaesthetic practice. We describe a case of a previously investigated malignant hyperthermia-susceptible patient who did not declare his status and was exposed to both succinylcholine and isoflurane, without any detectable reaction. Possible explanations for the lack of reaction include a subnormal temperature when exposed to isoflurane, and a significant interval between exposure to succinylcholine and isoflurane. Absence of a reaction to trigger agents on this occasion is not thought to indicate an incorrect diagnosis and labelling.