Haemodynamic instability and myocardial ischaemia during carotid endarterectomy: a comparison of propofol and isoflurane.

The purpose of this study was to compare two anaesthetic protocols for haemodynamic instability (heart rate (HR) or mean arterial pressure (MAP) < 80 or > 120% of ward baseline values) measured at one-minute intervals during carotid endarterectomy (CEA). One group received propofol/alfentanil (Group Prop; n = 14) and the other isoflurane/alfentanil (Group Iso; n = 13). Periods of haemodynamic instability were correlated to episodes of myocardial ischaemia as assessed by Holter monitoring (begun the evening before surgery and ceasing the morning of the first postoperative day). In Group Prop, anaesthesia was induced with alfentanil 30 micrograms.kg-1 i.v., propofol up to 1.5 mg.kg-1 and vecuronium 0.15 mg.kg-1, and maintained with infusions of propofol at 3-12 mg.kg-1.hr-1 and alfentanil at 30 micrograms.kg-1.hr-1. In Group Iso, anaesthesia was induced with alfentanil and vecuronium as above, thiopentone up to 4 mg.kg-1 and maintained with isoflurane and alfentanil infusion. Phenylephrine was infused to support MAP at 110 +/- 10% of ward values during cross-clamp of the internal carotid artery (ICA) in both groups. Emergence hypertension and/or tachycardia was treated with labetalol, diazoxide or propranolol. Myocardial ischaemia was defined as ST-segment depression of > or = 1 mm (60 msec past the J-point) persisting for > or = one minute. For the entire anaesthetic course (induction to post-emergence), there was no difference between groups for either duration or magnitude outside the < 80 or > 120% range for HR or MAP. However, when the period of emergence from anaesthesia (reversal of neuromuscular blockade to post-extubation) was assessed, more patients were hypertensive (P = 0.004) and required vasodilator therapy in Group Iso (10/13 vs 5/14; P = 0.038 Fisher's Exact Test). The mean dose of labetalol was greater in Group Iso (P = 0.035). No patient demonstrated myocardial ischaemia during ICA cross-clamp. On emergence, 6/13 patients in Group Iso demonstrated myocardial ischaemia compared with 1/14 in Group Prop (P = 0.029). Therefore, supporting the blood pressure with phenylephrine, during the period of ICA cross-clamping, appears to be safe as we did not observe any myocardial ischaemia at this time. During emergence from anaesthesia, haemodynamic instability was associated with myocardial ischaemia. Under these specific experimental conditions, with emergence, hypertension and myocardial ischaemia were more prevalent with more frequent pharmacological interventions in patients receiving isoflurane.

Canadian anaesthesia physician resource planning--is it possible?

This study was undertaken with the objective of assessing current sources of information for anaesthesia Physician Resource Planning (PRP). Four major data bases, the annual reports of Health and Welfare Canada (H&W), the education statistics from the Canadian Post-M.D. Education Registry (CAPER), the Royal College of Physicians and Surgeons of Canada (RCPSC) and the Physician Resource Data System of the Canadian Medical Association (PRDS), were examined for the period 1982 to 1991. The ratio of the number of surgical (S) to anaesthesia (A) clinicians decreased over this period despite an increase in the S:A ratios for trainees and certificants. The number of female anaesthetists has progressively increased. A steady decline in the number of rural anaesthetists has occurred. Age distribution of active certified anaesthetists revealed marked inter-regional differences. Little change was noted in the total mean hours worked per week. Each database provided valuable, but limited, data. The PRDS data is useful in assessing trends (age, sex and practice activity). Information provided by H&W tends to underestimate anaesthesia resource information by at least 10%. While information obtained from RCPSC and CAPER is accurate, the current mode of presentation of data limits their usefulness. Integrating data from all the databases appears to provide a meaningful assessment for PRP rather than assessing each database in isolation. Interpretation of the information and its value must take into account the limitations of the data being provided. Assessing present and planning future needs based on the current information structure will prove extremely difficult.

Continuous opioid infusions for neurosurgical procedures: a double-blind comparison of alfentanil and fentanyl.

The ability of continuous infusions of opioids to control hypertension at the end of neurosurgical procedures without compromising prompt emergence was studied in patients undergoing craniotomy for supratentorial tumours. Four infusion regimens were compared in a randomized double-blind fashion; three of alfentanil and one of fentanyl. Low-dose alfentanil was administered to nine patients (35.1 micrograms.kg-1 then a continuous infusion of 16.2 micrograms.kg-1.hr-1); mid-dose alfentanil to eight patients (70.2 micrograms.kg-1 then 32.4 micrograms.kg-1.hr-1); high-dose alfentanil to eight patients (105.3 micrograms.kg-1 then 48.6 micrograms.kg-1.hr-1). Eight additional patients were given fentanyl (8.3 micrograms.kg-1 then 1.6 micrograms.kg-1.hr-1). Using published values for the pharmacokinetic variables of alfentanil and fentanyl, modelling predicted stable concentrations of 60, 120, 180 ng.ml-1 for the alfentanil infusion regimens respectively and 2 ng.ml-1 with the fentanyl regimen. Maintenance anaesthesia comprised the opioid infusion, 50% N2O in O2 and isoflurane titrated to control mean arterial pressure (MAP) within 20% of ward MAP. Isoflurane was discontinued after closure of the dura. Nitrous oxide was discontinued at the same time as reversal of neuromuscular blockade. The opioid infusion was discontinued with closure of the galea. A greater time-averaged isoflurane concentration was required to control MAP within the prescribed limits in the low alfentanil group (ANOVA; P less than 0.05). The PaCO2 at two, five and 30 min after extubation were not different among groups. The times from discontinuing N2O to eye opening and tracheal extubation were not different. The time to follow commands was longer in the low alfentanil group (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of intravenous anaesthetic agents on human neutrophil chemiluminescence.

Intact neutrophil function is essential for the defence against infection. Any alteration in neutrophil function, which decreases their ability to phagocytose and kill bacteria, might contribute to mortality and morbidity. We investigated the effects of clinical concentrations of thiopentone, Alfathesin, methohexitone, morphine, lidocaine and diazepam on the microbicidal oxidative function of human neutrophils. The oxidative activity was assessed utilizing the technique of chemiluminescence, which is a measure of free radical generation. Thiopentone and Alfathesin produced a significant dose dependent depression in chemiluminescence. There was a 27 per cent reduction in activity with thiopentone 5 micrograms X ml-1, a concentration equivalent to the free plasma concentration achieved following an anaesthetizing dose of thiopentone. There was a 55 per cent reduction in chemiluminescence at an alphaxolone concentration of 1.25 micrograms X ml-1, a concentration equivalent to the free plasma level obtained after induction of Alfathesin anaesthesia. The effect of thiopentone and Alfathesin was reversed by cell washing. Methohexitone, morphine, diazepam, and lidocaine caused no significant reduction in chemiluminescence over the dose ranges studied. These observations indicate that thiopentone and Alfathesin can adversely affect leucocyte function in vitro and, therefore, may contribute to impaired host resistance in the perioperative period and in the intensive care unit.

Anaesthesia and the elderly.

The peri-operative management of elderly patients presents a variety of problems to the anaesthetist. These include organ dysfunction associated with the ageing process and the high incidence of serious disease affecting major organ systems. In addition, elderly patients commonly require multiple drug therapy. As such they are likely to suffer adverse drug effects and interactions, events more liable to occur in these patients as a result of both pharmacokinetic and pharmacodynamic factors. Occasionally serious interactions may occur with drugs used during anaesthesia. The importance of adequate pre-operative assessment and preparation cannot be overemphasized, as well as the need for a team approach to the management.

Topical analgesia of the upper airway with lignocaine. Absorption and its relationship to toxic and anti-arrhythmic levels.

After routine topical application of lignocaine to the upper airway before passage of an endotracheal tube during general anaesthesia, plasma lignocaine levels were assayed in 20 artificially ventilated and 21 spontaneously ventilating patients. Systemic absorption was found to be rapid but very variable. Mean peak level were attained 15 minutes before spraying and were well below the convulsive threshold for anaesthetized patients, while reputedly anti-arrhythmic levels were achieved by 5 minutes and maintained until 40 minutes. Levels in the ventilated group were significantly higher 20 minutes after administration.

Anaesthesia for surgical correction of fractured femoral neck. A comparison of three techniques.

Sixty patients with fractured neck of femur and scheduled for surgical correction were randomly allocated to receive one of three anaesthetic techniques: general anaesthesia; spinal analgesia; psoas compartment block. The patients in the local anaesthetic groups also received a light general anaesthetic. There was little difference in the pre-, intra- and postoperative events, and no difference in postoperative mortality.

Safety restraints for children travelling in motor vehicles.

The parents of 202 children were questioned about their use of safety restraints for their children while they were passengers in a motor vehicle. The result of the survey shows a low incidence of use of safety restraints by both parents and their children and that the type used for children was, in the majority of cases, both inadequate and dangerous. There was a correlation between the use of safety restraints by both parent and child on the day of questioning, but no association was found between the use of these restraints and the social class, educational standard achieved, income group, home language or home province of the parents. Neither was there any association between the use of safety restraints and a history of previous traffic accidents which had involved the family or close friends. In South Africa, the number of deaths in childhood as a result of motor vehicle accidents exceed those from the same cause in the United Kingdom. We consider that the medical profession in this country should inform the public of the desirability of fitting and using safety restraints of the correct type for children while they are passengers in motor vehicles. Reasons for the high incidence of serious injuries to children who are passengers in motor vehicles are reviewed and the methods of restraining children of different ages are discussed.