Nitrous oxide and cerebrospinal fluid markers of ischaemia following cardiopulmonary bypass.

Twenty patients with good ventricular function undergoing coronary artery bypass surgery were studied to determine whether the pre-bypass use of nitrous oxide resulted in any differences in cerebrospinal fluid markers indicative of cerebral ischaemia. All patients were anaesthetised with diazepam, fentanyl and pancuronium, after which ten patients received 50-60% nitrous oxide in oxygen until commencement of bypass, and the remaining patients 100% oxygen. Because of the known effect of nitrous oxide in expanding gaseous bubbles, any neurological dysfunction of gaseous microembolic origin may be worsened in the presence of nitrous oxide. Patients were lumbar punctured 24 hours after cardiopulmonary bypass and cerebrospinal fluid analysed for the following markers of central nervous system ischaemia: creatine kinase, lactate, total protein, noradrenaline, adrenaline and adenylate kinase. There was a statistically significant difference in cerebrospinal fluid lactate between the two groups. There were no statistically significant differences in the other cerebrospinal fluid markers of ischaemia.

Precipitous bradycardia induced by laryngoscopy in cardiac surgical patients.

We present three patients with severe ischaemic heart disease who developed profound bradycardia (heart rates of 15 beats.min-1, 10 beats.min-1 and asystole) at the time of laryngoscopy and spraying of the trachea with topical lidocaine. All patients had received fentanyl 20-30 micrograms.kg-1 and pancuronium 0.1-0.13 mg.kg-1 and in each case laryngoscopy was performed three minutes after the administration of these agents. We believe that in these cases the dosage of fentanyl was inadequate and since increasing the dosage of fentanyl to at least 50 micrograms.kg-1 and eliminating the manoeuvre of laryngeal spraying with topical anaesthesia, we have not encountered this problem.

Anaesthesia and Marfan's syndrome: case report.

An 18-year-old male with Marfan's syndrome underwent surgery for repair of an ascending aortic dissection. The clinical features of this congenital syndrome and the acute management of its complications are described. As elective surgery is frequently required for ocular, musculo-skeletal or cardiovascular problems in people with Marfan's syndrome, patients must be carefully assessed preoperatively for specific complications. Significant pulmonary problems include restriction of lung function due to pectus excavatum or kyphoscoliosis and intrinsic pulmonary involvement with emphysema, bronchogenic cysts and "honeycomb lung." This leads to a significant incidence of spontaneous pneumothorax and the danger of tension pneumothorax with positive pressure ventilation. The commonest causes of sudden death are cardiovascular complications, in particular rupture and dissection of the ascending aorta. Preoperative assessment should include echocardiography to determine the size of the aortic root. The anaesthetic technique chosen should both decrease myocardial contractility and avoid sudden increases in contractility, in order to minimise the risk of aortic dissection or rupture.