Electrocardiography during Posterior Fossa Operations.

SUMMARY Continuous electrocardiography was performed during eighty operations on the posterior fossa of the skull and fifty-seven other neurosurgical operations, all in the sitting position. There was little difference between the two groups in the incidence of arrhythmia before operation and during the surgical approach; more serious irregularities were almost entirely confined to periods when the surgeon was operating in the vicinity of the pons, the medulla, and the roots of the fifth, ninth and tenth cranial nerves. Severe arrhythmias may indicate or be the cause of medullary failure in this position and may also give an early warning of air embolism. Therefore continuous electrocardiography is valuable provided that its limitations are understood. During the last five years continuous electrocardio-graphy has been carried out during operation in a series of eighty consecutive posterior fossa operations and, for comparison, in forty-three cases of cervical laminectomy and in fourteen cases of trigeminal root section by the lateral extra-dural approach. All patients were operated on in the sitting position, but for trigeminal root section a table was used instead of a chair and the patient's legs were horizontal. The average age was less in the posterior fossa group as it included thirty-seven children. The posterior fossa cases were premedicated with atropine only. The remainder were given a small dose of morphine sulphate, 11 mg or less, in addition to the atropine. Anaesthesia was induced with thiopentone in all patients with the exception of two infants in whom open ether was used. It was maintained with nitrous oxide, oxygen, and trichloroethylene using aT-piece technique. One child, whose cardiac rhythm remained normal throughout, received a small amount of halothane. Electrocardiographic recording was started as soon as the patient had been placed in the sitting position. taken from lead 2. P-wave abnormalities include absent or inverted P-waves and atrial extra-systoles, but not alterations in the height of the P-wave or in the length of the P-R interval. Runs of ventricular extrasystoles refer to bursts of three or more consecutive extra systoles. Severe brady-cardia was defined as a heart rate of less than 50 beats a minute or of less than 60 beats a minute when the rate had dropped suddenly by more than 40 a minute. A swinging pulse rate refers to cases in which the pulse rate was rapidly and repeatedly altering by more than 40 beats a minute. In five instances this was due …