A comparison of spinal anaesthesia and propofol-sevoflurane-anaesthesia for ambulatory knee arthroscopy

Background: The aim of this study was to compare spinal anaesthesia (SA) and general anaesthesia (GA) for outpatient knee arthroscopy in terms of recovery profiles and discharge times. Methods: Sixty ASA I–II patients were randomized to receive either SA (N = 30) with lidocaine 50 mg/ml, 1 mg/kg or standardized propofol-sevoflurane-fentanyl GA (n = 30). Postoperative pain, need for analgesics, recovery profiles, complications, discharge times and patient satisfaction were evaluated. Patients were asked to complete a questionnaire after 24 h and 1 week. Results: After GA, 27% of patients needed supplemental opioid analgesics in contrast to 3% after SA (P < 0.01). Also, after GA 21(71%) patients suffered knee pain during the postoperative week compared to 10 (33.3%) after SA (P < 0.004). Intensity of postoperative pain was low (VPS-values <2). Duration of knee pain tended to be longer in GA group: 2.97 days versus 1.37 days in SA group. There were no differences in discharge times. High degree of patient satisfaction was associated with both techniques without statistical difference. Conclusion: SA provided superior postoperative pain management and leads to reduced consumption of analgesics, especially strong opioids. Both techniques provide a high grade of patient satisfaction.     

The effects of lowering fresh gas flow during sevoflurane anaesthesia: a clinical study in patients having elective knee arthroscopy

The potential for minimising anaesthetic gas consumption with a circle absorber system is related to fresh gas flow. This study measured the actual sevoflurane consumption during elective arthroscopy of the knee in 75 ASA I–II patients randomised to three fresh gas flow rates (6, 3, and 1.5 l/min) using sevoflurane and O₂:N₂O (1:2) after intravenous induction with fentanyl and propofol. A circle absorber system was used with a laryngeal mask airway. Anaesthetic duration, discharge time and postoperative pain did not differ between groups. Sevoflurane consumption was more than doubled with each doubling of fresh gas flow (0.07±0.03; 0.16±0.05; 0.41±0.12 ml sevoflurane/min; for gas flow 1.5, 3, 6 l/min; P<0.01). The hourly sevoflurane related cost decreased from 15.5 to 2.8 US$ when reducing the fresh gas flow from 6 to 1.5 l/min. Decreasing the fresh gas flow from 6 to 1.5 l/min provides good anaesthetic depth with effective reduction in anaesthetic consumption, cost and environmental burden.     

Regional anaesthesia for outpatient knee arthroscopy: a randomized clinical comparison of two different anaesthetic techniques

BACKGROUND: The purpose of this prospective, randomized study was to evaluate the time required to perform anaesthesia, achieve surgical block and fulfil standardized discharge criteria in outpatients receiving knee arthroscopy with either spinal anaesthesia or combined sciatic-femoral nerve block. METHODS: After a standard midazolam/ketoprofen premedication and baseline measurement of cardiovascular parameters, 50 ASA I-II patients scheduled for elective outpatient knee arthroscopy were randomized to receive spinal anaesthesia with 8 mg of 0.5% hyperbaric bupivacaine (group Spinal, n=25), or combined sciatic-femoral nerve block with 25 ml of mepivacaine 20 mg ml(-1) and a multiple injection technique (15 ml for femoral nerve block and 10 ml for sciatic nerve block). Times lasting from skin disinfection to the end of local anaesthetic injection (preparation time) and then to achieve surgical anaesthesia (readiness for surgery), as well as times required for block resolution, micturition, unassisted ambulation, and home discharge were recorded by a blinded observer. Occurrence of adverse events was also recorded. RESULTS: Preparation time (mean+/-SD) was longer with sciatic-femoral block (8+/-2.7 min) than spinal anaesthesia (5+/-2.1 min) (P=0.0002) while no differences were observed in the time required to achieve readiness for surgery (14+/-5 min and 15+/-6 min in the Spinal and Sciatic-femoral groups, respectively). No differences in haemodynamic side effects and need for intraoperative additional analgesia were observed. Patients receiving spinal anaesthesia showed a faster resolution of nerve block and longer time to micturition (137+/-49 min and 231+/-101 min) than patients receiving peripheral nerve blockade (206+/-51 min and 145+/-36 min) (P<0.0005 and P=0.002, respectively); however, no differences were observed in the time required to fulfil standardized discharge criteria (241+/-101 min in group Spinal and 209+/-70 min in group Sciatic-femoral; P=0.86). CONCLUSION: In patients receiving elective outpatient knee arthroscopy, using a combined sciatic-femoral nerve block with 25 ml of mepivacaine 20 mg ml(-1) and a multiple injection technique results in a slightly longer preoperative time but provides similarly effective anaesthesia with no differences in home discharge times as compared to spinal anaesthesia with 8 mg hyperbaric bupivacaine.     

One-week recovery profiles after spinal, propofol, isoflurane and desflurane anaesthesia in ambulatory knee arthroscopy

There are comprehensive findings on the immediate recovery of patients from different types of anaesthesia, but more information is needed on how patients manage at home after ambulatory surgery. One hundred and seventy-three elective knee arthroscopy patients were randomised into four different anaesthesia groups to receive either spinal anaesthesia (SA) with 5% lidocaine or general anaesthesia (GA) with propofol infusion, isoflurane inhalation or desflurane inhalation. The patients were interviewed over the phone on the next day and asked to complete a questionnaire after 1 week. One hundred and sixty-eight patients (97%) were reached by phone. The questionnaire was returned by 163 patients (94%). After 24 h, all the patients were satisfied with the type of anaesthesia they had received, but 2% of the SA patients would have chosen GA and 4.3% of the GA patients would have chosen SA for the next operation. Based on the questionnaires returned after 1 week, 8.3% of the SA patients would have wanted to have GA, and 4.7% of the GA patients would have wanted to have SA in the future. The incidence of nausea (4.2%) and vomiting (1.8%) was very low in the whole series, with no differences between the anaesthesia groups. Headache after 24 h was experienced by 15.7% of the SA and 10.3% of the GA patients. After 1 week, SA patients reported headache upon standing in 13.5% of the cases, backache in 36.5% and lower leg pain in 59.6%. The corresponding figures for GA patients were 4.5, 9.9 and 39.6% (P<0.05). In spite of the good immediate recovery profile in the all anaesthesia groups, the fact that SA patients reported a higher incidence of headache, backache and lower leg pain after 1 week may be signs of post spinal headache and transient neurologic symptoms (TNS). For overall patient comfort, GA might be a better anaesthetic choice in ambulatory surgery.     

Unconscious learning during surgery with propofol anaesthesia

Background. Learning during anaesthesia has been demonstrated,but little is known about the circumstances under which it mayoccur. This study investigated the hypothesis that learningduring anaesthesia occurs during, but not before, surgical stimulation. Methods. Words were played through headphones to 64 day-surgerypatients during propofol anaesthesia. Fourteen words were playedrepeatedly (15 times) for 1 min each either before (n=32) orduring (n=32) surgical stimulation. The depth of anaesthesiawas estimated using the bispectral index^TM (BIS^TM). Heart rate,ventilatory frequency, mean arterial pressure, end-tidal carbondioxide concentration, and infusion rate of propofol were recordedat 1 min intervals during word presentation. On recovery, memorywas assessed using an auditory word stem completion test andword recognition test. Results. The mean BIS^TM, arterial pressure, end-tidal carbondioxide and heart rate during word presentation did not differbetween the groups. The infusion rate of propofol and the ventilatoryfrequency were significantly greater in the during-surgicalstimulation group. There was no evidence for explicit recallor recognition, nor of awareness during anaesthesia (medianmean-BIS^TM=38 in the before-surgical stimulation group and 42in the during-surgical stimulation group). Only patients whowere played words during surgical stimulation showed significantimplicit memory on recovery (mean score=0.08, P<0.02) However,their scores were not significantly higher than those of thebefore-surgical stimulation group (mean score=0.01). Conclusions. Learning during anaesthesia seems more likely tooccur during rather than before surgical stimulation at comparableanaesthetic depth. We hypothesize that surgical stimulationfacilitates learning during anaesthesia, independently of itseffects on anaesthetic depth. Br J Anaesth 2004; 92: 171–7     

A comparison of three regional anaesthesia techniques for outpatient knee arthroscopy

Purpose

The purpose of this study was to compare intraoperative conditions and postoperative pain control of three penpheral regional anaesthesia techniques for outpatient knee arthroscopic procedures.

Methods

Sixty patients were randomized to one of three groups. Group IA received portal injections (10 ml lidocaine 1%), intraarticular lidocaine (20 ml CO₂ lidocaine 2% with 1/200.000 adrenaline) and a placebo femoral nerve block (20 ml saline). Group FNB received a femoral 3-in-1 nerve block (20 ml chloroprocaine 2% with 1/200.000 adrenaline), placebo portal injections (10 ml saline) and placebo intraarticular saline (20 ml saline with 1/200.000 adrenaline). Group FNB + IA received a femoral 3-m-1 nerve block, intraarticular hdocaine and placebo portal injections. The following were assessed: intraoperative pain (10 cm VAS: 0 = no pain. 10 = extreme pain), surgical operating conditions (1 = excellent. 4 = unacceptable), intraoperative use of sedation and analgesia, time to discharge, patient satisfaction score (1= very satisfied, 5 very unsatisfied) and postoperative analgesia. Data were analyzed using ANOVA, Kruskal-Wallis, and Chi-square tests as appropriate. P< 0.05 was considered significant.

Results

There were no differences among the groups regarding any of the vanables tested. Considerable postoperative pain (VAS> 5) was expenenced by 20/54 (37%) patients.

Conclusion

Any of the three anaesthetic techniques tested provide reliable intraoperative patient and surgical conditions for outpatient knee arthroscopy. Patient discomfort postoperatively was considerable in all groups and requires further investigation.     

Comparison of sevoflurane and propofol for ambulatory anaesthesia in gynaecological surgery

PURPOSE: To analyse the cost-efficiency ratio of sevoflurane compared with propofol for gynaecological ambulatory anaesthesia. METHODS: In a prospective randomised study 52 ASA I patients scheduled for ambulatory pregnancy termination were premedicated with lorazepam and received alfentanil prior to anaesthesia induction with propofol (group P, n = 26) or with sevoflurane 8% (group S, n = 26) using the single breath vital capacity technique. Anaesthesia was maintained with N2O in both groups supplemented with sevoflurane (group S) or propofol boluses (group P). RESULTS: The quality of induction and maintenance of anaesthesia was similar between groups except for the incidence of movement during anaesthesia (14/26 patients in group P and 4/26 in group S, P < 0.05). The incidence of post-operative emesis was increased in the sevoflurane group (P < 0.05) but the patients felt able to perform normal activity after a similar delay (18.4 +/- 2.9 hr vs 20.6 +/- 2.8 hr, P > 0.05). The direct cost of anaesthesia was lower in the sevoflurane group (679 FF, n = 24 vs 1153 FF, n = 2-5 in propofol group) but the weight of uterine aspiration products was higher (293 +/- 66 g, median = 230 g, Range 110-800 g, n = 13 vs 108 +/- 8 g, median = 110 g, Range 60-160 g, n = 12, group S vs group P respectively, P = 0.004). Four patients needed reoperation and ambulatory anaesthesia failed in six patients because of uterine haemorrhage. CONCLUSION: Ambulatory anaesthesia with sevoflurane offers a good alternative to propofol but further investigation concerning blood loss with sevoflurane needs to be performed in gynaecological practice.     

Inhalation induction with sevoflurane: a double-blind comparison with propofol

We conducted a randomized, double-blind comparison of 8% sevoflurane and propofol as induction agents for day-case cystoscopy in 102 patients. All patients received an i.v. cannula and breathed oxygen 5 litre min-1. Anaesthesia was induced with propofol i.v. or inhalation of 8% sevoflurane and 10% Intralipid (as a placebo) i.v., delivered by a blinded observer. Anaesthesia was maintained in all patients with 2% sevoflurane via a face mask. Induction of anaesthesia with sevoflurane was significantly slower compared with propofol (mean 84 (SD 24) s vs 57 (11) s), but was associated with a lower incidence of apnoea (16% vs 65%) and a shorter time to establish spontaneous ventilation (94 (34) s vs 126 (79) s). Induction complications were uncommon in each group but the transition to maintenance was smoother with sevoflurane and was associated with less hypotension compared with propofol. Emergence from anaesthesia induced with sevoflurane occurred significantly earlier compared with propofol (5.2 (2.2) min vs 7.0 (3.2) min) and anaesthetic induction was also significantly cheaper with sevoflurane. According to a postoperative questionnaire, the majority of patients found both anaesthetic techniques acceptable. Nevertheless, significnatly more patients (14%) rated induction with sevoflurane as unpleasant compared with propofol (0) and significantly more patients (24%) would not choose sevoflurane induction compared with propofol (6%). This phenomenon may have been related to the particular patient population studied, however. Inhalation induction with 8% sevoflurane would appear to offer several objective advantages compared with induction with propofol in day-case patients, although a significant minority may dislike this technique.      

Thiopentone or propofol for induction of isoflurane-based anaesthesia for ambulatory surgery?

This study compares psychomotor recovery following induction of anaesthesia with either thiopentone or propofol in 30 healthy, unpremedicated patients undergoing outpatient arthroscopic procedures of the knee. A battery of tests including simple reaction time (SRT), choice reaction time (CRT), perceptive accuracy test (PAT) and digit symbol substitution test (DSST) were done before anaesthesia. The patients were randomly divided into two groups: Group 1 was induced with thiopentone 5-6 mg/kg while Group 2 was induced with propofol 2-3 mg/kg. Anaesthesia was then maintained with isoflurane (0.5-2%) in oxygen and air, and supplements of alfentanil were given for analgesia during spontaneous respiration with a face mask. Psychomotor recovery assessed every 30 min postoperatively for 120 min showed that patients in Group 1 had not returned to baseline values until 120 min after the operation on the PAT, while those in Group 2 had returned to baseline values at 60 min. No patient had any significant side effects. The SRT, CRT and DSST proved to be relatively insensitive in the detection of residual effects of anaesthesia and had a significant learning effect. This study suggests that induction of anaesthesia with propofol followed by maintenance with isoflurane in oxygen and air during spontaneous ventilation is associated with rapid psychomotor recovery and is a suitable method for ambulatory surgery. The PAT is sensitive and not associated with some of the problems found with other commonly used tests.     

Spinal,epidural or propofol anaesthesia for out–patient knee arthroscopy?

Background : We have compared three different methods of anaesthesia for out–patient knee arthroscopy in terms of perioperative conditions, postoperative pain, time taken and economy.
Methods : 91 ASA I–II patients scheduled for elective knee arthroscopy were included. After premedication with diazepam 10 mg and naproxene 500 mg orally, they were randomly assigned into one of three groups: Group S (n=32) received spinal anaesthesia with lidocaine 50 mg/ml 1.5–2 ml in 7.5% glucose through a 27–G Quincke needle, Group E (n=29) received epidural anaesthesia with mepivacaine 20 mg/ml and epinephrine 5 μg/ml, 15–20 ml, and Group P (n=30) received propofol anaesthesia with a bolus induction of 2 mg/kg followed by infusion.
Results : The time from start of anaesthesia until start of operation was significantly less in Group P than in the two other Groups: 7.45.4 min as compared to 23.04.8 min in Group S and 31.09.1 min in Group E (meanSD, P<0.05). After end of surgery, the duration of the postoperative regional block was 7528 min in Group S and 125 79 min in Group E (P<0.05). In Group S and Group E the postoperative pain was significantly less than in Group P at admission to the recovery unit and 60, 120 and 180 min later (P<0.05). The overall incidence of postoperative nausea or vomiting was less than 5% with no differences between the groups. One patient in Group E had block failure and one patient in Group S had a post–spinal headache. The perioperative costs of drugs and disposables were highest in Group P (30 USD) and lowest in Group S (6.5 USD).
Conclusion : Propofol anaesthesia results in the shortest stay in the operation theatre but a higher degree of postoperative pain and a higher cost of drugs and disposables.     

Differences between bispectral index and spectral entropy during xenon anaesthesia: a comparison with propofol anaesthesia

We enrolled 114 patients, aged 65–83 years, undergoing elective surgery (duration > 2h) into a randomised, controlled study to evaluate the performance of bispectral index and spectral entropy for monitoring depth of xenon versus propofol anaesthesia. In the propofol group, bispectral index and state entropy values were comparable. In the xenon group, bispectral index values resembled those in the propofol group, but spectral entropy levels were significantly lower. Mean arterial blood pressure was higher and heart rate was lower in the xenon group than in the propofol group. Bispectral index and spectral entropy considerably diverged during xenon but not during propofol anaesthesia. We therefore conclude that these measures are not interchangeable for the assessment of depth of hypnosis and that bispectral index is likely to reflect actual depth of anaesthesia more precisely compared with spectral entropy.     

Recovery from sufentanil anaesthesia for outpatient arthroscopy: a comparison with isoflurane

This study compares the recovery from sufentanil and isoflurane anaesthesia in patients undergoing outpatient arthroscopy of the knee under general anaesthesia. In 40 unpremedicated patients, divided at random into two groups, anaesthesia was induced with methohexitone and vecuronium bromide and, after intubation, maintained with nitrous oxide 66% in oxygen supplemented with sufentanil or isoflurane. Patients in Group A received sufentanil (1 microgram/kg) at induction and if necessary an incremental dose of 10 micrograms. Patients in Group B received 3% isoflurane prior to intubation and 0.9% during maintenance. Awakening from anaesthesia was more rapid with sufentanil than isoflurane. Recovery was assessed from the time patients took to open their eyes, to give correct answers to five questions and to recover from ocular imbalance. (Maddox wing test), and by comparing pre- and postoperative performance of a paper and pencil test (the p-deletion test). After 2 h, there was no difference between the two groups. Both anaesthetic techniques provided satisfactory operating conditions, but the sufentanil group showed a higher incidence of nausea and vomiting (45%) than the isoflurane group (15%).     

Intrathecal ropivacaine and clonidine for ambulatory knee arthroscopy: a dose-response study

BACKGROUND: The aim of this study was to evaluate the association of a small dose of intrathecal ropivacaine with small doses of intrathecal clonidine for ambulatory surgery. METHODS: One hundred twenty patients, classified as American Society of Anesthesiologists physical status I and scheduled for knee arthroscopy, were studied. Patients were randomly assigned to receive 4 ml of one of the following double-blinded isobaric intrathecal solutions: 8 mg of ropivacaine (group 1; n =30); 8 mg ropivacaine plus 15 microg clonidine (group 2; n =30); 8 mg ropivacaine plus 45 microg clonidine (group 3; n =30); and 8 mg ropivacaine plus 75 microg clonidine (group 4; n =30). The level and duration of sensory anesthesia were recorded, along with the intensity and duration of motor block. Patient and surgeon were interviewed to evaluate the quality of anesthesia. RESULTS: Intrathecal ropivacaine (8 mg alone) produced short sensory anesthesia and motor blockade (132 +/- 38 min and 110 +/- 35 min; mean +/- SD). However, the quality of anesthesia was significantly lower than in any other group (P < 0.05). Ropivacaine (8 mg) plus 75 microg clonidine produced significantly longer sensory and motor anesthesia (195 +/- 40 min and 164 +/- 38 min; P < 0.05). However, this was associated with systemic effects, such as sedation and reduction of arterial blood pressure. Ropivacaine (8 mg) plus 15 microg clonidine did not prolong sensory or motor blockade, afforded high quality anesthesia, and was not associated with detectable systemic effects. CONCLUSION: Small-dose intrathecal clonidine (15 microg) plus 8 mg intrathecal ropivacaine produces adequate and short-lasting anesthesia for knee arthroscopy.     

Unconscious auditory priming during surgery with propofol and nitrous oxide anaesthesia: a replication

Background. Priming during anaesthesia has been hard to replicateand the conditions under which it occurs remain poorly understood.We replicated and extended a recent study to determine whetherintraoperative priming during propofol and nitrous oxide anaesthesiais a reliable phenomenon, whether it occurs due to awarenessduring word presentation and whether it is suppressed by a doseof fentanyl at induction. Methods. Words were played through headphones during surgeryto 62 patients receiving propofol and nitrous oxide anaesthesia.Thirty-two patients received fentanyl 1.5 µg kg^–1at induction and 30 received no fentanyl. Neuromuscular blockingdrugs were not used. Depth of anaesthesia was measured usingthe bispectral index (BIS). Anaesthetic variables were recordedat 1 min intervals during word presentation. On recovery, implicitand explicit memory were assessed using an auditory word-stemcompletion test and a yes–no word-recognition test, respectively. Results. BIS, blood pressure, end-tidal carbon dioxide and heartrate during word presentation did not differ between the studygroups. The infusion rate of propofol and the patients' ventilatoryfrequency were significantly higher in the group not receivingfentanyl. No patient had unprompted explicit recall of surgery,although there was above-zero performance in six patients onthe yes–no recognition task (P<0.05). There was nophysiological evidence of awareness during anaesthesia (medianmean-BIS=38 in the no-fentanyl group and 42 in the fentanylgroup). There was evidence for priming (mean priming score=0.09,P<0.05 in the no-fentanyl study group; mean priming score=0.07,P<0.05 in the fentanyl group) even when patients with momentarylight anaesthesia (maximum recorded BIS     

Home readiness after day-case knee arthroscopy: spinal, desflurane, isoflurane or propofol anaesthesia?

In this study, four accepted methods of anaesthesia were compared during out-patient knee arthroscopy (KA). Immediate (<2 h) postoperative recovery was evaluated in terms of pain, sedation, nausea and time for home readiness. 173 patients undergoing elective KA were randomised to receive either spinal, propofol infusion, isoflurane or desflurane inhalation anaesthesia. Postoperative pain, sedation and nausea were recorded at 30, 60, 90 and 120 min after arrival in the recovery unit (RU). Discharge readiness was defined as fulfilment of the following criteria in all groups: alert, stable vital signs, able to ambulate, able to take oral fluids, no nausea and pain controllable by oral medication. Postoperative pain, in general, was low in all groups. The spinal patients had significantly lower VAS scores (p<0.001) than the general anaesthesia patients at 30, 60 and 90 min after arrival in RU. At 120 min the pain level was equal in all groups. No remarkable differences between the general anaesthesia groups were noted in terms of pain and nausea. The overall incidence of nausea was 3.4%. Propofol and isoflurane patients were more sedated at 30 min postoperatively than spinal and desflurane patients. At 60 min postoperatively all groups were alert. The time required for home readiness was significantly shorter in all the general anaesthesia groups (propofol 55 min, isoflurane 56 min and desflurane 46 min) than in the spinal anaesthesia group (168 min) (p<0.001). General anaesthesia is a practical alternative in elective knee arthroscopy. The immediate recovery profile is smooth with low levels of pain and nausea and home readiness is achieved significantly sooner than after spinal anaesthesia.     

Cost comparison between three different general anaesthetic techniques for elective arthroscopy of the knee

INTRODUCTION: We compared three anaesthetic techniques for elective knee arthroscopy with special reference to cost-effectiveness. METHOD: Seventy-five ASA I-II patients having elective arthroscopy of the knee joint were randomised to receive an anaesthetic technique based on propofol, fentanyl for induction followed by sevoflurane in oxygen:nitrous oxide (1:2 l/min) for maintenance of one of two intravenous techniques: propofol alfentanil or propofol-remifentanil infusions in combination with oxygen in air. RESULTS: All patients had an uncomplicated course. No differences were seen with regard to emergence, postoperative pain or emesis or time to discharge. The anaesthetic technique based on sevoflurane was associated with the lowest cost US$ 14.7 as compared to US$ 18 for the propfol/alfentanil and US$ 19.9 for the propofol/remifentanil technique, including both cost for wastage as well as premedication and other fixed drug costs. Looking only at the anaesthetic drugs consumed, the cost per minute was US$ 0.56 for sevoflurane/nitrous oxide as compared to US$ 0.68 and 0.63 per minute for the propofol/alfentanil and proprofol/remifentanil, respectively. When the cost for wastage was taken into account, the difference in mean anaesthetic drug cost was more pronounced: the sevoflurane anaesthetic technique US$ 0.58, the propofol/alfentanil US$ 0.74 and the propofol/remifentanil US$ 0.84 per minute respectively. CONCLUSION: From a cost-minimisation point of view, anaesthesia based on sevoflurane in oxygen:nitrous oxide is the technique of choice.     

Heat loss during induction of anaesthesia for elective aortic surgery

We have studied core temperature changes occurring during induction of general anaesthesia and surgery in 18 patients undergoing elective aortic aneurysm repair. In the operating theatre, all patients were warmed with a forced-air warmer and a warming mattress, and received warmed (37 degrees C) intravenous fluids. Despite this, mean (SD) [range] core temperatures in the anaesthetic room decreased by 1.5 (0.3)[1.1-2.2] degrees C, while intravascular lines, epidural and urinary catheters were inserted before the introduction of warming methods in theatre. In one-third of patients, the core temperature was still below 36 degrees C at the end of surgery. The overall temperature decrease correlated significantly with the duration of time between induction of general anaesthesia and surgical incision (R2 = 0.6912), when the patients were not being warmed. Hypothermia may thus be prevented by minimising the period that the patient is anaesthetised without being warmed. Vascular lines, urinary and epidural catheters should be inserted before the induction of general anaesthesia or, alternatively, warming methods should be introduced in the anaesthetic room.