Delayed Recovery After Anæesthesia

A PATIENT has recovered from an anasthetic when consciousness has fully returned and any disability remaining is due to the surgical condition.Knowing the agent used and the length and depth of ana?sthesia maintained in a particular patient the time interval between withdrawal of the anaesthetic and recovery under standard conditions can be predicted with reasonable accuracy.This interval varies from several hours after prolonged etherisation to a few minutes following nitrous oxide anasthesia.Here it should be noted that if in the latter case pentothal has been used for induction and no nikethamide given post-operatively to counteract its influence, patients may sleep for several hours if the standard conditions allow of comfort and quiet ; such patients, however, can be awakened by ordinary stimuli.It is therefore disconcerting if after the expected time of recovery .onefinds the patient stuporous, and it is a matter of some urgency to diagnose the cause of the condition.This may be due to one or other of the well-recognised causes of coma, and although the anasthetic state may have initiated the process, the diagnosis and treatment are little influenced by the preceding anasthetic.Thus cerebral hamorrhage or thrombosis may follow upon profound disturbances of blood pressure in the arteriosclerotic patient undergoing operation ; an unrecognised diabetes mellitus may advance into deep ketosis ; in the tropics a latent infection may result in cerebral malaria after trauma', or the anasthetised, and perhaps also atropinised, patient may suffer from heatstroke during or immediately after operation.Severe shock with its associated tissue anoxia can result in such damage to the higher centres that their functions are impaired and unconsciousness supervene.Morphia given in relatively large or repeated doses to the shocked patient may give rise to dangerous morphinisation when the peripheral circulation improves.Such cases will not be considered here.Two further causes of post-anasthetic stupor must be reviewed.True coma may occur after an anasthetic in which anoxia has been present.Courville3 drew attention to this danger especially during nitrous oxide anasthesia, but he emphasised that it is the anoxia which is the causative factor and not the anathetic agent in use.Clearly defined cases in his series usually regained consciousness following the anoxic episode ; but often recovery was not complete, the brain was irreparably damaged and, possibly due to vasomotor instability, the destructive process continued.The patients died after a varying period.In less severe cases there may be recovery with residual symptoms suggestive of cortical or lenticular damage, Finally, there is the group of patients who show transitory emotiqnal or mental manifestations before recovering completely.Pathological