Anaesthesia and Intensive Care

The effect of oral premedication was studied in a double-blind, randomised trial of 200 children undergoing day-stay anaesthesia. Midazolam 0.25 mg/kg, midazolam 0.5 mg/kg, diazepam 0.5 mg/kg or a placebo was given orally one hour prior to anaesthesia. Patient state was assessed at nine stages, from administration of the premedication up to and including induction of anaesthesia, using a four-point behavioural scale. Patient state was also assessed postoperatively in the recovery area and the day-stay ward. There was no difference between the four groups until induction of anaesthesia. At this stage 82% of children were either asleep or awake and calm. Patients who received midazolam 0.5 mg/kg were more likely to be asleep or awake and calm at induction rather than other groups (P= 0.05). Children receiving midazolam 0.5 mg/kg or diazepam 0.5 mg/kg slept longest in the post anaesthetic recovery room (P < 0.005), and spent most time there (P <. 005). There was no difference between groups in the length of time spent in the day-stay ward or in the number of overnight admissions.

The study shows that a high proportion of unsedated children are calm at induction of anaesthesia and that oral midazolam is an effective premedication in children for day-stay anaesthesia.

A randomised, single-blind study was conducted among 52 gravida in active labour, to investigate two variants of patient-controlled epidural analgesia — bolus only versus bolus plus infusion. Patient-controlled analgesia variables, using an epidural solution of 0.125% bupivacaine plus fentanyl 3 mcg per ml, were a 4 ml incremental bolus with 15 minute lockout, plus or minus a 4 ml per hour infusion. Up to three additional staff-administered supplements of 0.5% bupivacaine 4 ml (20 mg) were allowed.

There was no significant difference between groups with respect to pain relief, supplementary boluses required, satisfaction, side-effects or details of patient-controlled epidural analgesia, with the exception of greater fentanyl usage in the bolus plus infusion group (P < 0.003).

Both groups had high quality analgesia, low rates of bupivacaine usage and were highly satisfied. However, under the conditions of the study, the addition of a continuous background infusion to self-administration conferred no benefit.

We measured haemodynamic effects and uptake of enflurane in patients undergoing cardiac surgery utilizing a standard anaesthetic technique of fentanyl 15 mcg/kg nitrous oxide 50%/enflurane 1%. We divided 22 patients preoperatively into two groups according to standard criteria: good and poor myocardial function. Regression lines could be drawn illustrating the relationship of cardiac output and uptake (at 1 minute: r = −0.56, P < 0.01; at 5 minutes: r = −0.43, P < 0.05; at 30 minutes: r = −0.31, P=0.08). Although patients with poor myocardial function had decreased uptake of enflurance (approximately 10–20%), this did not reach statistical significance. Fentanyl/nitrous oxide/enflurane anaesthesia provided stable haemodynamics, even in patients with poor myocardial function. Both groups had a shunt fraction of approximately 10% and an arterial: end-tidal carbon dioxide difference of approximately 3–4 mmHg.

The cardiovascular and haematological effects of purified prothrombin activator derived from the venom of the Australian Common Brown Snake (Pseudonaja textilis) were studied in anaesthetised, mechanically ventilated dogs. Severe depression of systemic blood pressure and cardiac output and a rise in central venous pressure were observed. Thrombocytopenia, prolongation of both prothrombin time and activated partial thromboplastin time and a reduction in serum fibrinogen were also observed. All of these observed effects were prevented by the prior administration of heparin — a naturally occurring anticoagulant. We conclude that the prothrombin activator in Pseudonaja textilis venom may cause cardiovascular depression due to myocardial dysfunction secondary to disseminated intravascular coagulation.

The efficacy of heparin therapy after subcutaneous injection of Common Brown Snake (Pseudonaja textilis) venom was studied in anaesthetised, mechanically ventilated dogs. Intravenous heparin (100 U/kg), administered fifteen minutes after envenomation, neither prevented nor hastened the recovery from cardiovascular depression and coagulopathy observed after venom administration. Heparin therapy is not recommended for the treatment of established human envenomation.

Fentanyl is commonly used as an adjunct to general anaesthesia for day-surgery procedures. We have prospectively studied the effect of this practice on postoperative analgesia in 304 day-surgery patients, 164 undergoing termination of pregnancy and 140 having various other minor gynaecological procedures. Approximately half the patients received fentanyl, the mean dose being 50 mcg. Fentanyl given during anaesthesia had no effect during recovery on analgesic requirements or on nausea or vomiting in either pregnant or non-pregnant patients.

Patient acceptance is a particularly relevant method of assessing currently employed epidural and intravenous techniques of opioid analgesia after elective caesarean section. We have prospectively studied 71 such patients, randomised postoperatively to receive epidural morphine, intravenous morphine or intravenous pethidine. When compared with either intravenous opioid, epidural morphine provided twofold better average or excellent analgesia with 30% less drowsiness but with about 50% more pruritus. In spite of this troublesome complication, more patients (83% vs 74%) preferred epidural to intravenous opioid analgesia.

This double-blind randomised study compared postoperative analgesia after a loading regimen of methadone or morphine in thirty women undergoing abdominal hysterectomy. Methadone or morphine, 0.25 mg.kg⁻¹, was given intravenously at induction of anaesthesia with further increments in the recovery room for analgesia if required. The mean (SD) total doses of methadone and morphine required were 0.43 (0.13) mg.kg⁻¹ and 0.45 (0.15) mg.kg⁻¹ respectively. Patients in the methadone group had lower pain scores in the subsequent 48 hours (P < 0.001) and required less supplementary intramuscular opioids (P < 0.001). Ten patients in the methadone group did not request any further opioid analgesics while all patients in the morphine group made at least two requests for opioids. The overall postoperative course was remembered as less painful by patients in the methadone group (P < 0.001). There was no significant respiratory depression or excessive sedation in either group.

A preliminary study of 24 hours’ postoperative analgesia using a patient-controlled analgesia technique was undertaken in eight European and fourteen Asian adult patients. All patients had upper abdominal surgery and received weight-related doses of pethidine postoperatively via a Cardiff Palliator. Both groups had a similar degree of analgesia as assessed by visual analogue score but the Asian patients were more sedated in the postoperative period. The Asian patients made 24% fewer demands for analgesia and had a smaller mean (SD) pethidine consumption, 7.62 (2.04) mg.kg⁻¹, compared with the European patients, 9.97 (2.14) mg.kg⁻¹, (P < 0.05) during the first 24 hours. Further research is necessary to determine whether the smaller requirement for analgesia in Asian patients is a result of pharmacokinetic or pharmacodynamic differences.

In a retrospective survey of all adults admitted to the Intensive Care Unit with acute theophylline poisoning over the last five years, we identified 38 patients (6.8% of all admissions for poisoning), two of whom died. Thirty-five (92%) had taken a sustained-release preparation. Eight patients had grand mal seizures and six developed arrhythmias (ventricular fibrillation, 3; atrial fibrillation, 2; supraventricular tachycardia, 1). Severe vomiting was present in 34 (89%) and proved to be a serious obstacle to the administration of enteral charcoal. The vomiting was controlled by intravenous metoclopramide in seventeen patients (50%), but the remaining seventeen required mechanical ventilation with sedation and muscle relaxation for the effective delivery of nasogastric charcoal. Importantly, in nine (24%), the serum theophylline concentration continued to rise despite enteral charcoal. Charcoal haemoperfusion was used in seven (18%). We present an algorithm for the management of severe, acute theophylline poisoning.

Using the APACHE II scoring system, the risk of death was calculated for 189 patients in the Wanganui Intensive Care Unit and 194 patients in the Harare Intensive Care Unit. Using tables of actual and predicted outcome, the predictive power of the system was compared in patients grouped according to the length of time that they spent in the ICU. The predictive error increased from 15% in those patients staying less than six days, to 38% in those staying six days or more (P < 0.01). The predictive accuracy of the APACHE II system appeared to decrease with the length of time the patient stayed in the Intensive Care Unit.

Xenon has many of the properties of the ideal anaesthetic agent and has been proposed as a suitable replacement for nitrous oxide in routine clinical anaesthesia. Xenon, krypton and argon are chemically inert under most circumstances, yet all have anaesthetic properties. Xenon is of particular interest because it is the only ‘inert’ gas which is an anaesthetic under normobaric conditions. Because of this property, xenon has an important place in the history of the development of theories of anaesthetic action and of concepts such as MAC. Cost is likely to be a major impediment to the regular use of xenon.

A new technique is described to aid in achieving a correct blind insertion of an endobronchial tube. The tube is selected by length to fit the distance from the patient's mouth to carina. As the tube is inserted, the position of the endobronchial cuff is monitored. This is done by inflating the bronchial cuff in the trachea and after each breath, advancing the tube down the trachea until only one lung is inflated. This accurately identifies the bronchial cuff as just beyond the carina, at the entrance to the main bronchus. From here, the tube can be advanced precisely into the bronchus to give the optimal conditions for isolation of the right and left lungs.

The first human infection with Chromobacterium violaceum was recorded in 1927,¹ but since men mere have been about 33 cases reported worldwide, including two from Australia.^2,3 Chr. violaceum occurs in the tropics and subtropics and is generally considered to be nonpathogenic, but infection can occur in patients who are immunosuppressed⁴ and it has a high mortality rate.³ This paper presents the intensive care management of two cases of Chr. violaceum infection occurring in Far North Queensland. The patients’ predisposition appears to have been malnourishment and alcohol abuse. The increased use of immunosuppressive drugs and the appearance of diseases such as acquired immune deficiency syndrome (AIDS) make it possible that we will see more of this condition in Australian intensive care units.