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Arterial lignocaine concentrations were measured in twenty-six patients who had carotid endarterectomy performed under deep and superficial cervical plexus blockade. A dose of 6 mg/kg of 1.5% lignocaine with 1:200,000 adrenaline was used, as well as additional supplementation by the surgeons when required. Concentrations obtained produced a mean peak of 5 micrograms/ml and were similar to those previously reported from multiple bilateral intercostal blockade, which is the regional technique widely considered to produce the highest systemic levels of local anaesthetic. Apart from one peak concentration of 16.9 micrograms/ml, levels were well below the convulsion threshold. We find the technique acceptable and safe for carotid surgery and lignocaine toxicity is not identified as a problem.

One hundred and twenty-eight patients having carotid endarterectomy under superficial and deep cervical plexus blocks were prospectively audited. The aim of the audit was to determine the incidence of intra-operative and postoperative neurological and cardiovascular complications and to establish patient acceptance of the technique. Twenty-seven patients who had intra-operative neurological changes following carotid artery clamping responded to shunt insertion. Six patients had transient neurological changes after the operation but there were no permanent neurological complications. Tachycardia (55%) and hypertension (67%) were the most common intra-operative cardiovascular changes and there was one clinical postoperative myocardial infarction. Ninety-two per cent of patients who could be adequately assessed preferred to have the same method of anaesthesia for future carotid endarterectomy. The authors concluded that carotid endarterectomy under superficial and deep cervical plexus blocks was associated with a high patient acceptance, low neurological complication rate and an acceptable rate of cardiovascular complications.

A new processed EEG machine, the Lifescan, which uses aperiodic analysis, was used to monitor cerebral activity prospectively in twenty-one patients undergoing carotid artery surgery under general anaesthesia. The machine was easy to apply, use and read. Volatile agents caused a bilateral decrease in high frequency activity. Unilateral changes consistent with cerebral ischaemia at the time of carotid cross-clamping were also seen. One such prolonged change was not associated with neurological deficit. A further patient awoke with neurological deficit without displaying Lifescan evidence of ischaemia. The machine requires further assessment.

A processed electroencephalogram (EEG) produced by the Lifescan monitor (Neurometrics), was compared to awake neurological assessment for detecting cerebral ischaemia in seventy patients undergoing carotid endarterectomy under cervical plexus block. Of the six patients demonstrating neurological signs on cross-clamping the carotid, five displayed simultaneous EEG changes, four being detected during surgery, and one being detected after reviewing the EEG postoperatively. Another four patients displayed EEG changes indicative of ischaemia but unassociated with neurological signs. A further patient displayed contralateral intraoperative EEG changes. Hypotension resulted in one EEG change and two cases were associated with technical difficulties with the monitor. The presence of false negatives, possible false positives, technical errors and subjective interpretation associated with the processed EEG make it less reliable than awake neurological assessment for the detection of cerebral ischaemia.

Blood pressure changes following carotid endarterectomy were studied in 39 patients undergoing 42 carotid endarterectomies, in order to establish the incidence of hypertension and to study the use of hydrallazine for its treatment. Hypertension occurred in 28 cases (66%) and was treated with intravenous hydralazine in a dose of 20 +/- 8 mg; this resulted in a systolic blood pressure fall of 46 +/- 22 mmHg, diastolic blood pressure fall of 24 +/- 12 mmHg, mean blood pressure fall of 31 +/- 15 mmHg, and a pulse rate increase of 7 +/- 9 beats per minute. Hydrallazine is a safe, effective drug for the treatment of intraoperative hypertension.

The Cerebral Electrical Activity (CEA) was monitored by Lifescan in 38 patients undergoing carotid surgery under general or regional anaesthesia and another 20 patients during cardiopulmonary bypass undergoing open heart surgery. This monitor uses aperiodic analysis to process the electroencephalogram. Abrupt changes in CEA were observed when blood flow was disrupted due to surgical intervention or administration of thiopentone. Gradual changes in CEA were due to anaesthesia or hypothermia. In one patient a long period of depressed CEA did not result in a neurological deficit and in another patient a neurological event was undetected by the monitor.