Biomedical subjects
Publications and source records attributed to A R Aitkenhead.
This retrospective study found that the long-term (greater than 6 months) postoperative survival in ASA 4E and 5E patients was 41% and 21% respectively, in 1986. This supports the Confidential Enquiry into Peri-operative Deaths' recommendation that life-saving surgery should not be withheld from patients who present in so serious a condition that they are unlikely to survive surgery.
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101 critically ill patients admitted to five intensive-care units were allocated randomly to receive a continuous intravenous infusion of either propofol or midazolam for sedation for up to 24 h. In addition, morphine was given to provide analgesia. The mean duration of infusion was 20.2 h (range 3.0-24.5) in the propofol group and 21.3 h (4.0-47.0) in the midazolam group and infusion rates were 1.77 mg/kg/h (range 0.40-5.00) and 0.10 mg/kg/h (0.01-0.26), respectively. The infusion rates were adjusted as necessary, and the desired level of sedation was achieved easily in most patients in both groups. There were slight falls in arterial pressure, but there were no significant differences between the groups. Heart rate was lower in patients who received propofol. Some small changes occurred in biochemical and haematological variables in both groups, but they were not clinically significant. There was no indication that either drug substantially impaired adrenal steroidogenesis. When the infusion was discontinued, there was less variability in recovery of consciousness in patients who had received propofol. In a subgroup of patients, weaning from mechanical ventilation was achieved significantly faster after discontinuation of propofol than of midazolam. Propofol proved to be a satisfactory agent for sedation of these critically ill patients and compared favourably with midazolam.
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We have investigated, in volunteers, the effect of inhaling 50% nitrous oxide in oxygen on subsequent oxygenation. Subjects breathed either 50% nitrous oxide in oxygen or 50% nitrogen in oxygen during hyperventilation and normal ventilation. Arterial oxygen saturation and end-expired oxygen concentrations were lower after 50% nitrous oxide in oxygen than after the other mixture with both patterns of ventilation and were lowest after hyperventilation with 50% nitrous oxide in oxygen.
Recent evidence has shown that there may be leakage of anaesthetic drugs into the systemic circulation during the tourniquet inflation phase of intravenous regional anaesthesia. This, together with increased pressure in forearm vessels during manipulation of fractures, prompted the measurement of arterial levels of local anaesthetic to assess potential toxicity. Prilocaine levels were measured in nine patients undergoing manipulation of Colles' fractures and six patients undergoing other upper limb procedures. Eleven patients had measurable concentrations of prilocaine in the arterial circulation during the time the tourniquet was inflated, the maximum levels being measured in those patients having fractures manipulated. Considerable vigilance should be ensured during the time of tourniquet inflation in intravenous regional anaesthesia, particularly for fracture manipulation.
In a randomized, prospective study of patients undergoing large bowel anastomosis, 47 patients received subarachnoid block and light general anaesthesia, and 51 received conventional general anaesthesia with intermittent positive pressure ventilation. Anastomotic dehiscence occurred in 17.0% of the spinal group and in 17.6% of patients anaesthetized by the conventional technique. Blood loss was significantly (P less than 0.001) lower in the spinal group than in the general anaesthesia group. Blood transfusion was required in 10.6% of patients in the spinal group and 21.6% of patients receiving general anaesthesia.
The pharmacokinetics of nalbuphine were studied in 10 healthy volunteers on two separate occasions following administration by either the intravenous (20 mg) or oral (60 mg) route. After administration, serum concentrations of nalbuphine were measured for 12 h using a high pressure liquid chromatography assay, and pharmacokinetic parameters were derived using a three compartment model. After i.v. administration, elimination half-life was 222 (111-460) min (mean and range) and total body clearance was 1.5 (0.8-2.3) 1 min-1.Cmax after oral administration was 21.4 (6.0-36.2) ng ml-1 and tmax was 46.6 (15.3-89.0) min. Bioavailability of the oral preparation was 11.8 (6.1-20.1)%.
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Twelve patients presenting to an accident and emergency department in asystolic cardiac arrest were randomly allocated to treatment with endotracheal adrenaline (five patients) or peripheral intravenous adrenaline (seven patients). Femoral-artery blood samples were taken for assay of adrenaline and noradrenaline. After intravenous adrenaline there was a good clinical and biochemical response, but after endotracheal adrenaline there was no change in serum adrenaline and no measurable clinical response. The endotracheal route of adrenaline administration is not reliable in out-of-hospital cardiac arrest.
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Vecuronium was used to provide muscle relaxation in a patient who subsequently developed prolonged neuromuscular blockade (8 h) after anaesthesia. The aetiology of this condition, and the possible role of vecuronium, are discussed.
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