Arterial lignocaine concentrations following cervical plexus blockade for carotid endarterectomy.

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.

Carotid endarterectomy under cervical plexus block--a prospective clinical audit.

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.

Pre-bypass myocardial ischaemia in patients undergoing coronary artery surgery.

One hundred patients undergoing elective coronary artery surgery were studied to determine the incidence of pre-bypass myocardial ischaemia. Leads II, aVF and V5 of the electrocardiogram (ECG) were recorded at five-minute intervals from arrival in the anaesthetic room until onset of cardiopulmonary bypass. Thirteen patients developed sixteen episodes of significant ST depression on the ECG during the study period. Three patients were diagnosed as having postoperative myocardial infarction by ECG criteria and creatine phosphokinase-MB rise above 80 units. None of these patients had pre-bypass ST depression. Comparisons of these results with similar studies are presented.

EEG monitoring using aperiodic analysis during carotid and open heart surgery.

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.

Comparison of the processed electroencephalogram and awake neurological assessment during carotid endarterectomy.

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.

The use of aperiodic analysis of the EEG during carotid artery surgery.

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.

An experimental in vivo study of the canine internal mammary artery and its response to vasoactive drugs.

The internal mammary artery is clearly the preferred conduit for most patients undergoing coronary artery bypass grafting. However, the hemodynamic responses of this graft to vasoactive agents immediately after bypass have not been documented. We have therefore studied blood flow in the canine internal mammary artery after anastomosis to the left anterior descending artery, and its response to epinephrine, metaraminol, isoproterenol, and calcium chloride. Blood flow in the internal mammary artery clearly paralleled changes in systolic blood pressure with perfusion pressure being of prime importance in maintaining flow in the internal mammary artery. No deleterious effect of systemic vasoconstricting agents was demonstrated. We suggest that the administration of these drugs is safe in patients with internal mammary artery grafts.

Radial artery cannulation--the influence of method on blood flow after decannulation.

A prospective randomised study of two hundred patients undergoing open-heart surgery was carried out to determine if the method of radial artery cannulation (direct threading or transfixion) had any influence on the incidence of abnormal flow after decannulation. A standard 20-gauge non-tapered teflon-coated cannula was used and the groups were well matched for age, sex, wrist circumference, duration of cannulation and haematoma formation, all of which have been postulated to influence thrombosis rate. We were unable to demonstrate a statistically significant difference between the two methods of cannulation. The overall abnormal flow rate at five days assessed by Doppler ultrasound was low at 5%.

A prospective randomised trial comparing spinal anaesthesia using hyperbaric cinchocaine with general anaesthesia for lower limb vascular surgery.

One hundred and one patients were randomly allocated to have their peripheral vascular surgery performed under general anaesthesia (51 patients) or spinal anaesthesia (50 patients). Intraoperative haemodynamic changes were markedly different between the two groups with a higher incidence of hypotension in the spinal group (72% vs 31%) and a higher incidence of hypertension in the general anaesthesia group (22% vs 0%). Blood loss was significantly less in the spinal group (560, SD 340, ml vs 792, SD 440, ml). Postoperatively three patients from the general anaesthesia group died from causes unrelated to the anaesthesia, and one had a myocardial infarct. Two patients in the spinal group had myocardial infarcts, both had been treated for bradycardia and hypotension intraoperatively, and one died. There was a significantly higher incidence of postoperative chest infection in the general anaesthesia group (33% vs 16%). There was no significant difference between the groups in the incidence of postoperative confusion, or lower limb amputation rate or need for further surgery prior to hospital discharge.

Blood conservation in elective surgery.

Blood conservation for elective surgery involves both the reduction of blood loss and the reduction of homologous blood transfusion. Methods of reducing blood loss such as the use of tourniquets, vasoconstrictor drugs, regional anaesthetic supplements and hypotensive anaesthesia are considered briefly. Preoperative and intraoperative techniques of autotransfusion and haemodilution are considered in detail, including a technique of scavenging and reinfusing blood aspirated from the surgical site.

Cardiovascular risk factors in patients for vascular surgery.

Various attempts have made been made to quantify the cardiovascular risk factors associated with anaesthesia and surgery. Two such schemes are the "Multifactorial Index of Cardiac Risk" developed by Goldman et al., and the one devised by Cooperman et al. The validity of these two schemes in relation to anaesthesia for vascular surgery was investigated by carrying out a prospective study of 100 patients. Cooperman's scheme was found to be much more accurate than Goldman's scheme in assessing patient risk. The study confirms the impression that the vascular patient falls into a higher risk group than most other surgical patients with regard to cardiovascular complications.

Haemodilution for major vascular surgery--using 3.5% polygeline (Haemaccel).

Intra-operative haemodilution and autotransfusion was carried out in 32 patients having major vascular surgery. The intra-operative blood loss and peri-operative blood replacement was compared with that in 25 patients having similar surgery in whom haemodilution was considered to be contraindicated. Both groups of patients had similar mean intra-operative blood loss measured but homologous blood transfusion requirements were significantly different; 2.6 units (SD 1.9) in the haemodiluted patients compared with 6.0 units (SD 3.5) in the non-diluted patients. There was no mortality in the haemodiluted patients nor was any morbidity attributed to the procedure. Polygeline (haemaccel) was used as the diluent and proved satisfactory for this purpose.

Pulmonary artery catheterisation. An assessment of risks and benefits in 220 surgical patients.

The benefits and risks of pulmonary artery catheterisation were assessed in 220 patients having cardiac or vascular surgery. Prior to induction of anaesthesia 20% of patients had pulmonary artery wedge pressure measurements which indicated the need for blood volume support, vasodilator therapy or modification of the anaesthetic induction technique. Of those patients for cardiac surgery, 38% had important changes before cardiopulmonary bypass requiring blood volume support or vasodilator therapy. These changes were not reflected by similar changes in the central venous pressure. The risks of the technique were minimal. Minor complications occurred in 25% of patients (transient arrhythmias) and more serious complications occurred in 3.6% of patients. There was no mortality or long-term sequelae. We conclude that the benefits of pulmonary artery catheterisation outweigh its risks in patients having major cardiac and vascular surgery.

The prevention of hypertension at intubation. A controlled study of intravenous hydrallazine on patients undergoing intracranial surgery.

Arterial blood pressure and pulse rate changes following tracheal intubation were studied in 20 patients undergoing intracranial surgery who received a thiopentone/suxamethonium anaesthetic induction sequence. Ten of the patients were pretreated with 0.4 mg/kg of hydrallazine and 10 with saline to determine whether hydrallazine prevents intubation hypertension. The results show that the incidence of intubation hypertension can be reduced using this dose of hydrallazine. Hydrallazine pretreatment is therefore recommended in patients at risk from hypertension following tracheal intubation.

Post carotid endarterectomy hypertension.

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.

Assessment of sympathectomy--the skin potential response.

Objective assessment of the results of surgical sympathectomy and sympathetic block (both temporary and permanent) are not widely practised. This article comments briefly on the available methods, and describes the use of the abolition of the skin potential response (formerly known as the psychogalvanic reflex) to assess the abolition of sympathetic function. This method of assessment has proved useful in clinical practice.

Intercostal block for post operative pain relief.

Intercostal nerve blocks with 0-5 per cent bupivicaine were used for post operative pain relief in 100 patients having upper abdominal operations. The blocks were very effective in 86 patients and had an average duration of 11 hours. Two asymptomatic pneumothoraces occurred.