Clinical and economic choices in anaesthesia for day surgery: a prospective randomised controlled trial

We compared the cost-effectiveness of general anaesthetic agents in adult and paediatric day surgery populations. We randomly assigned 1063 adult and 322 paediatric elective patients to one of four (adult) or two (paediatric) anaesthesia groups. Total costs were calculated from individual patient resource use to 7 days post discharge. Incremental cost-effectiveness ratios were expressed as cost per episode of postoperative nausea and vomiting (PONV) avoided. In adults, variable secondary care costs were higher for propofol induction and propofol maintenance (propofol/propofol; p < 0.01) than other groups and lower in propofol induction and isoflurane maintenance (propofol/isoflurane; p < 0.01). In both studies, predischarge PONV was higher if sevoflurane/sevoflurane (p < 0.01) was used compared with use of propofol for induction. In both studies, there was no difference in postdischarge outcomes at Day 7. Sevoflurane/sevoflurane was more costly with higher PONV rates in both studies. In adults, the cost per extra episode of PONV avoided was pound 296 (propofol/propofol vs. propofol/ sevoflurane) and pound 333 (propofol/sevoflurane vs. propofol/isoflurane).

Anaesthesia for day case surgery: a survey of adult clinical practice in the UK

BACKGROUND AND OBJECTIVE

In October 2000, we conducted a national postal survey of consultant day case anaesthetists in the UK to explore the range and variation in the practice of anaesthetizing a patient for day case surgery (paediatrics, urology and orthopaedics). The survey was carried out as part of a larger study that comprised a major two-centre randomized controlled trial designed to investigate the costs and outcome of several anaesthetic techniques during day care surgery in paediatric and adult patients (cost-effectiveness study of anaesthesia in day case surgery). We report the findings of this national survey of adult urology and orthopaedic day case anaesthetic practice in the UK.

METHODS

The survey used a structured postal questionnaire and collected data on the duration of the surgical procedure; the use of premedication; the anaesthetic agents used for induction and maintenance; the fresh gas flows used for anaesthesia; the use of antiemetics; and the administration of local anaesthesia and analgesia.

RESULTS

The overall response rate for the survey was 74% (63% for urology, 67% for orthopaedics). The survey indicated the following practice in adult urology and adult orthopaedic day case surgery: 6 and 12% used premedication; propofol was the preferred induction agent (96 and 97%) and isoflurane the preferred maintenance agent (56 and 58%); 32 and 41% used prophylactic antiemetics; 86 and 93% used a laryngeal mask.

CONCLUSIONS

This survey identifies the variation in current clinical practice in adult day surgery anaesthesia in the UK and discusses this variation in the context of current published evidence.

Anaesthetic agents in adult day case surgery

This study reports a review of all comparative published studies of adult day case anaesthesia in the English language up to December 2000. Ten databases were searched using appropriate keywords and data were extracted in a standardized fashion. One hundred-and-one published studies were examined. Recovery measurements were grouped as early, intermediate, late, psychomotor and adverse effects. With respect to induction of anaesthesia, propofol was superior to methohexital, etomidate and thiopental, but equal to sevoflurane and desflurane. Desflurane and sevoflurane were both superior to thiopental. There was no detectable difference between sevoflurane and isoflurane. With respect to the maintenance of anaesthesia, isoflurane and halothane were the worst. There were no significant differences between propofol, desflurane, sevoflurane and enflurane. Propofol is the induction agent of choice in day case patients. The use of a propofol infusion and avoidance of nitrous oxide may help to reduce postoperative nausea and vomiting.

Anaesthetic agents in paediatric day case surgery: do they affect outcome?

Both the numbers of children undergoing day case surgery and the type of procedures performed in this way are increasing. This expansion will only be beneficial if anaesthesia and surgery are provided with minimal post-operative morbidity e.g. postoperative delirium or nausea and vomiting. The choice of anaesthetic technique is considered critical to optimizing the service provided to patients and for this reason much research has addressed this question. This review considers the effect of anaesthetic technique on postoperative outcome in paediatric day case surgery. The outcome measures reviewed by this article are induction of anaesthesia, effects on the cardiovascular system, recovery from anaesthesia and postoperative nausea and vomiting. In each section both quantitative and qualitative outcome measures are discussed. Comparisons are made between sevoflurane and halothane, sevoflurane and propofol, propofol and halothane, desflurane and halothane and the presence or absence of nitrous oxide.

Antagonism of rapacuronium using edrophonium or neostigmine: pharmacodynamics and pharmacokinetics

We have studied the pharmacodynamics and pharmacokinetics of rapacuronium (Org 9487) in 70 healthy patients. Neuromuscular transmission was monitored using TOF stimulation of the ulnar nerve and mechanomyography of the adductor pollicis muscle. Half of the patients were given a single dose of rapacuronium 1.5 mg kg-1 and the remainder rapacuronium 1.5 mg kg-1 with three incremental doses of 0.5 mg kg-1, each given when T1/T0 had recovered to 25%. In all patients, neuromuscular block was antagonized using neostigmine 0.05 mg kg-1 or edrophonium 1.0 mg kg-1 (allocated randomly), 2 min after the final dose of rapacuronium. All patients developed complete block after rapacuronium 1.5 mg kg-1. Mean onset time was 66 (SD 24) s. In patients who received an antagonist 2 min after the first dose of rapacuronium, time to recovery of T1/T0 to 25% was similar after neostigmine (9.8 (3.8) min) and edrophonium (10.3 (4.3) min): in patients who received incremental doses of rapacuronium, spontaneous recovery of T1/T0 to 25% after the first dose was 18.9 (4.7) min. In those who received an antagonist 2 min after the first dose of rapacuronium, times to recovery of T4/T1 to 0.7 were also similar after neostigmine (23.7 (7.7) min) and edrophonium (29.1 (10.7) min). After three incremental doses of rapacuronium, there was a longer time to recovery of T1/T0 = 25% after neostigmine compared with edrophonium (5.1 (1.0) vs 3.3 (1.3) min; P < 0.05) but more rapid recovery to T1/T0 = 75% (10.1 (2.9) vs 16.8 (10.1) min; P < 0.05) and T4/T1 = 0.7 (19.8 (6.3) vs 35.1 (10.4) min; P < 0.05). A three-compartment pharmacokinetic model was justified. Typical values for clearance and initial volume of distribution (V1) were 4.4 ml kg-1 min-1 and 94.8 ml kg-1, respectively. In females, clearance was decreased by 38.5% compared with males and V1 was decreased by 25% in patients aged more than 65 yr.

Anaesthesia clinical directors in the United Kingdom: organisation, objectives and support needs

A postal survey of all 269 acute hospital trusts identified in the United Kingdom was carried out to study the work of Clinical Directors of anaesthesia. Initial responses from 163 Clinical Directors and 129 completed questionnaires were analysed. Four main areas of concern revealed by the survey were contracts and objectives, funding of managerial sessions, access to information and perceived need for support. Most Clinical Directors had no job description and most had no formal written objectives, despite a substantial body of advice that these should be provided. There was generally substantial underfunding of managerial hours compared with those actually worked and approximately 20% of Clinical Directors surveyed had no funding for managerial duties. Clinical Directors' ratings of the information available to assist their decision making were also a cause of concern. Clinical Directors perceived that they need better networking, more training particularly on human resource management and improved management information.

Anaesthesia for assisted conception: a survey of UK practice

A telephone survey was undertaken of all UK centres (total 70) licensed for performing in vitro fertilization (IVF) and gamete intra-fallopian transfer (GIFT) by the Human Fertilisation and Embryology Authority (HFEA). The survey was carried out during the months of November and December 1997. Thirty-seven (52.1%) centres were in the NHS sector and 33 (47.8%) in the private sector. A response was available from 60 (84%) centres. A standard questionnaire was used which requested information about the procedures carried out, anaesthetic technique and pharmacological agents used. Forty-seven centres carried out IVF, two centres GIFT and 11 centres both. Out of 58 centres carrying out IVF, sedation was used in 28, general anaesthesia in 17, sedation combined with regional anaesthesia in seven and regional anaesthesia in one. Five centres gave a choice. Out of 22 centres using general anaesthesia for IVF, 12 used inhalational agents (isoflurane eight, enflurane four, sevoflurane two), eight used total intravenous anaesthesia (TIVA) with propofol and two centres inhalational agents or TIVA. Propofol was the induction agent in all but two centres. For IVF under sedation, 18 centres used midazolam, five used diazepam, three used opioids, one used entonox and the remaining ones a combination. When sedation was combined with regional anaesthesia, four centres used midazolam, two used propofol, one used midazolam with propofol, one used opioids and one used entonox. The regional technique in the 11 centres was either paracervical block with lignocaine (eight) or subarachnoid block with bupivacaine (three). Systemic analgesia was secured with fentanyl (22), pethidine (16), alfentanil (15), diclofenac (14), piroxicam (two), ketorolac (one) and ibuprofen (one). Five centres did not use any opioids; 40 centres did not use any nonsteroidal agents (NSAIDs). Out of the 13 centres that carried out GIFT, 12 used general anaesthesia while the thirteenth gave the patient a choice between general or regional anaesthesia. 11 centres used inhalational agents (isoflurane nine, enflurane two) while two used TIVA with propofol; propofol was the induction agent used in six centres while thiopentone was used in five. The range of analgesics was wide--fentanyl in six centres, alfentanil in three, morphine in two, diclofenac in five and ketorolac in one. Two centres did not use any opioids and seven centres did not use an NSAID. The only agreement at present appears to be that halothane is an unwise choice for IVF. No other technique has yet been proven to be either advantageous or detrimental.

The influence of premedication on heart rate variability

Analysis of heart rate variability has been used to study the effects of midazolam, morphine and clonidine on the autonomic nervous system, when administered to patients for premedication. Ninety-five patients were studied 60 min before and 60 min after premedication. Normal saline (n = 25), midazolam 0.08 mg.kg-1 (n = 24), morphine 0.15 mg.kg-1 (n = 23), or clonidine 2 micrograms.kg-1 (n = 23) were administered intramuscularly by random allocation. A Holter device was connected to the patient during the study period. Using power spectral analysis the low-frequency and high-frequency components were calculated from the Holter recordings. These are markers for sympathetic and parasympathetic activity respectively; the low- to high-frequency ratio was also calculated, a ratio of > 1 signifying sympathetic dominance. A significant reduction was noticed in both low-frequency and high-frequency power in the three premedicated groups, whereas no changes were observed in the normal saline group. In the case of midazolam, both the low and high frequencies were decreased but the low- to high-frequency ratio did not change significantly. Morphine and clonidine depressed the low-frequency component more than the high-frequency component and the low- to high-frequency ratio was decreased, suggesting parasympathetic dominance. We conclude that heart rate variability may be a useful tool for investigating the effect of drugs on the autonomic nervous system.

Mivacurium or vecuronium for muscular relaxation in day-case surgery

Anaesthetic agents for day-case surgery ideally should have a short duration of action. This study was designed to compare the efficacy and safety of mivacurium and vecuronium for healthy adults undergoing dental day-case surgery. Thirty fit healthy adult patients (ASA I or II) randomly received either mivacurium 0.15 mg kg-1 (n = 15) or vecuronium 0.1 mg kg-1 (n = 15). Anaesthesia included propofol, fentanyl, nitrous oxide and isoflurane. Maximum depression of T1 was greater in the vecuronium group (99.8%) than in the mivacurium group (98.3%). There was no difference between grade of intubation at 2 min between the two groups, although patients receiving vecuronium had a more profound block at the time of intubation than those who received mivacurium (89.2% vs. 78.9%). Recovery to 10% T1 was faster in the mivacurium group (11.2 min vs. 33.1 min). All patients in the vecuronium group received neostigmine at the termination of surgery. The neostigmine evoked recovery index in the vecuronium group (4.39 min) was less than the spontaneous recovery index in the mivacurium group (6.78 min). One patient in the mivacurium group had a low plasma cholinesterase concentration (0.43 ku L-1); recovery times however, fell within the 95% confidence intervals (CI) for the group. There was no correlation between cholinesterase levels and recovery time. Mivacurium may be the more appropriate agent for dental day-case surgery because it has a shorter duration of action and does not generally require antagonism with an anticholinesterase.

A comparison of cisatracurium (51W89) and atracurium by infusion in critically ill patients

OBJECTIVE

To evaluate and compare the safety and efficacy of cisatracurium (51W89) and atracurium administered by continuous infusion to critically ill patients requiring neuromuscular blocking agents to facilitate mechanical ventilation.

DESIGN

Open, randomized, multicenter study of patients receiving cisatracurium or atracurium infusion to facilitate mechanical ventilation.

SETTING

Five university teaching hospital intensive care units in the United Kingdom.

PATIENTS

Sixty-one adult patients requiring neuromuscular blocking agents to facilitate mechanical ventilation.

INTERVENTIONS

Bolus doses followed by continuous infusions of cisatracurium or atracurium were administered. Onset, maintenance, and recovery of neuromuscular blockade were measured, using transcutaneous ulnar nerve stimulation and an accelerometer.

MEASUREMENTS AND MAIN RESULTS

Forty patients received cisatracurium (mean duration 48.1 +/- 4.2 [SEM] hrs), and 21 patients received atracurium (mean duration 46.1 +/- 5.8 hrs). The infusion rate for patients receiving cisatracurium was 3.1 +/- 0.2 microg/kg/min, and for patients receiving atracurium 10.4 +/- 0.9 microg/kg/min. There were no significant differences in mean times to 70% recovery of Train-of-Four ratio (cisatracurium 60 mins, atracurium 57 mins), although there was considerable interpatient variation (20 to 175 mins with cisatracurium vs. 35 to 85 mins with atracurium). One patient who received cisatracurium exhibited intermittent bronchospasm during and after the study period.

CONCLUSIONS

Cisatracurium, an isomer of atracurium, appears to be a suitable agent for providing muscle relaxation in critically ill patients.

Rocuronium and cisatracurium

Rocuronium and cisatracurium are the two most recent muscle relaxant additions to our pharmacopocia. These two drugs are significant advances and are likely to have an increasingly important role in clinical anaesthesia in the future.

The effects of midazolam or propofol followed by suxamethonium on the QT interval in humans

Prolongation of the QT interval may produce potentially hazardous arrhythmias. The effects of midazolam or propofol, followed by suxamethonium on the QT interval have been investigated. Thirty patients, ASA I or II, without cardiovascular disease, electrolyte abnormalities or receiving any medication were studied. All patients were premedicated with midazolam 0.08 mg kg-1 i.m., 30-60 min prior to surgery. Anaesthesia was induced with either midazolam 0.4 mg kg-1 i.v., (15 patients) or propofol 1 mg kg-1 i.v. bolus, followed by a continuous infusion (15 patients). ECG, heart rate and arterial pressure were measured before induction of anaesthesia and at 1 and 3 min after the bolus of midazolam or propofol. Further recordings were obtained at 1 and 3 min after a bolus of suxamethonium 1.5 mg kg-1 i.v. and also immediately after tracheal intubation and 1 min later. Neither midazolam nor propofol had any significant effect on QTc interval. Prolongation of QTc was observed in both groups after suxamethonium and this was further prolonged following intubation. Heart rate and arterial pressure were also increased significantly in both groups following intubation.

The infusion requirements and recovery characteristics of cisatracurium or atracurium in intensive care patients

OBJECTIVE

To investigate the infusion requirements and recovery characteristics of cisatracurium compared with atracurium when both are administered by prolonged continuous infusion.

DESIGN

A prospective, randomised, single-blind study.

SETTINGS

The Intensive Care Unit of the Manchester Royal Infirmary.

PATIENTS

20 patients requiring a continuous infusion of a neuromuscular blocking agent to facilitate mechanical ventilation. 12 patients received cisatracurium and 8 received atracurium.

INTERVENTIONS

Cisatracurium or atracurium was administered by continuous infusion for a minimum of 24 h. The level of neuromuscular blockade was measured by recording the train-of-four responses using acceleromyography, the aim being to maintain 1-2 twitch responses of the adductor pollicis. At the end of the infusion period, the train-of-four was recorded until the ratio was greater than 0.7.

MEASUREMENTS AND RESULTS

The mean infusion rate of cisatracurium was 0.23 mg kg-1 h-1, compared to 0.62 mg kg-1 h-1. No time-related increase in infusion requirements was seen for either drug. The mean recovery time to a train-of-four ratio greater than 0.7 was the same (46 min). There was no correlation between recovery time and age, duration of infusion or mean infusion rate.

CONCLUSIONS

Cisatracurium provides a satisfactory level of neuromuscular blockade in adult ICU patients at approximately one-third the infusion rate of atracurium and with a similar recovery time.

Anaesthesia and the QT interval in humans. The effects of isoflurane and halothane

Prolongation of the QT interval may cause potentially hazardous arrhythmias. The effects on the QT interval (QTc, corrected for heart rate) of isoflurane and halothane followed by vecuronium have been investigated during induction of anaesthesia in 51 patients. All patients were ASA 1 or 2, without cardiovascular problems or electrolyte abnormalities and were not receiving medication. Midazolam 0.08 mg.kg-1 was administered intramuscularly for premedication. Anaesthesia was induced with either isoflurane (n = 26) or halothane (n = 25), and the inspired concentration increased to reach an end-tidal concentration of 2.5% to 3%. Recordings of ECG, heart rate, systolic and diastolic arterial pressure were obtained at the following times: prior to induction of anaesthesia; 1 min and 3 min after a stable end-tidal concentration had been reached; 1 min and 3 min following vecuronium administration, at the time of tracheal intubation and 1 min and 3 min later. Halothane significantly shortened QTc (p < 0.05 to p < 0.001), in contrast to isoflurane which prolonged it (p < 0.01). The heart rate decreased (p < 0.01 to p < 0.001) after induction of anaesthesia with halothane and returned to pre-induction values after tracheal intubation. In contrast, heart rate increased after induction with isoflurane and increased further after laryngoscopy and tracheal intubation (p < 0.001). In the isoflurane group, ST depression was noticed in seven patients and nodal rhythm in two, while in the halothane group seven patients developed nodal rhythm and, in two patients, ventricular ectopics were recorded. There were no sequelae. In both groups, systolic and diastolic arterial pressure decreased after induction of anaesthesia (p < 0.01 to p < 0.001), increasing again after intubation.

Intubation conditions and time-course of action of low-dose rocuronium bromide in day-case dental surgery

A relatively small dose of rocuronium (0.45 mg kg-1) was compared with equipotent doses of atracurium (0.35 mg kg-1) and vecuronium (0.075 mg kg-1) for ease of intubation at 60 s. All patients could be intubated but the proportion with excellent or good conditions was much greater with rocuronium. Mean clinical duration of effect of this dose was 22.2 min. There was no correlation between intubating conditions and the degree of block of the adductor policis.

The role of muscle relaxants in total intravenous anaesthesia

For total intravenous anaesthesia (TIVA), all drugs that are required as part of the anaesthetic method are administered intravenously. This is usually taken to imply the use of intravenous infusions. It is normal practice to administer muscle relaxants intravenously, although other routes have been used. A muscle relaxant is required firstly to secure paralysis and secondly to maintain paralysis. The rate of onset of all the nondepolarizing neuromuscular blocking agents which are routinely available at present is similar; it takes about 3-6 min for a normal clinical dose to reach maximum effect. Maintenance of an adequate level of block is necessary, and it is usually helpful to the surgeon for the level of block to be relatively constant. The choice of drug is important. It should cause negligible side-effects. For administration by infusion, an agent with an intermediate (e.g., atracurium) or short (e.g., mivacurium) duration of action is essential to ensure a rapid recovery of effect on termination of the infusion. The routine use of neuromuscular monitoring is recommended when a continuous infusion of a relaxant is used.

Prediction of infusion rates of vecuronium using the bolus test dose technique

Fifty neurosurgical patients were given loading doses of vecuronium 0.1 mg kg-1 followed by boluses of 1, 2 or 4 mg after return of T1 of the train-of-four. Neuromuscular function was assessed simultaneously by palpation of the great toe after peripheral nerve stimulation of the lateral popliteal nerve using a handheld nerve stimulator and also using a Relaxograph attached to one arm. The time taken for the return of T1 after the bolus dose was recorded and an infusion of vecuronium was begun and subsequently adjusted to maintain steady state neuromuscular block. It was possible to predict the infusion rate of vecuronium from the duration of action of a 2-mg or 4-mg but not a 1-mg bolus dose using the handheld stimulator. The infusion rate could also be predicted from the duration of action of the initial loading dose.

The use of propofol for sedation of critically ill patients undergoing haemodiafiltration

OBJECTIVE

To assess the requirement for propofol to provide sedation in critically ill patients in established renal failure during the commencement of haemodiafiltration.

DESIGN

Prospective clinical study.

SETTING

ICU, University Hospital.

PATIENTS

10 adult patients. All were mechanically ventilated, had acute oliguric renal failure which necessitated continuous veno-venous haemodiafiltration and were receiving a continuous intravenous infusion of propofol for sedation. Sedation was assessed using a scoring system.

INTERVENTION

Veno-venous haemodiafiltration.

MEASUREMENTS AND RESULTS

Connection of the extracorporeal circuit produced a reduction in plasma propofol concentration in 7 out of 9 patients (one sample misplaced) with subsequent awakening in 3 of these 7 patients. The commencement of haemodiafiltration itself did not significantly influence the requirement for propofol (8 out of 10 patients).

CONCLUSION

Haemodiafiltration does not substantially influence the requirement for propofol but the initial introduction of the extracorporeal circuit will reduce plasma concentrations in the majority of patients. This may be due to haemodilution alone or absorption of plasma albumin (with propofol) onto the membrane.

Pulmonary function and head lift during spontaneous recovery from pipecuronium neuromuscular block

We have studied in seven healthy conscious volunteers the correlation between the electromyographic (EMG) and clinical criteria used to identify adequate recovery from sub-paralysing doses of pipecuronium. Pipecuronium (mean dose 1.88 (range 0.92-3.16) mg) was administered to reach a T4/T1 ratio of 0.5; full recovery to 1.0 was produced in a mean time of 25.3 (14-39) min. During recovery from neuromuscular block, we measured tidal volume, forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1) negative inspiratory pressure (NIP), peak expiratory flow rate (PEFR), mid-expiratory flow rate (MEFR) and 5-s head lift. The assessments were started when the train-of-four (TOF) ratio reached 0.5 +/- 0.001 and repeated at each 0.1 +/- 0.001 increase up to a ratio of 1.0. All volunteers showed ptosis and diplopia after the first dose and difficulty in swallowing with subsequent doses. They also experienced a pleasant, relaxing sedative sensation. All could sustain head lift for 5 s at a TOF ratio of 0.5 and higher, except for one subject who could not lift his head only at a ratio of 0.5. There was a statistically significant decrease in FVC, FEV1 and PEFR with a nonsignificant decrease in other pulmonary measurements, except for NIP which only decreased significantly at a ratio of 0.5. These changes are probably of no clinical importance. All the measured respiratory variables returned to control values at a TOF ratio of 0.9.

Molecular mechanisms of neuromuscular blocking agents: is the increased understanding of importance to the practising anaesthetist?

A neuromuscular blocking agent is an essential component of many general anaesthetics. Although a great deal is known about the neuromuscular junction, the site of action of these agents, their precise mode of action remains unclear. This article reviews our present knowledge of the anatomy and physiology of neuromuscular transmission and the ways in which clinically useful drugs may modify this system. The decisions involved in clinical choice of which agent to use are described with particular respect to basic physiology and pharmacology and also to potential interactions with other drugs.

Recovery after oral surgery with halothane, enflurane, isoflurane or propofol anaesthesia

We have compared the recovery characteristics of four different techniques for maintenance of anaesthesia in 99 day-case patients admitted for oral surgery. All patients received propofol for induction of anaesthesia followed by halothane, enflurane, isoflurane or propofol infusion for maintenance of anaesthesia. Each patient was subjected to a battery of psychometric tests which included Spielberger state, trait, mood stress and mood arousal questionnaires, Maddox-Wing test and five-choice serial reaction time. All tests were performed before operation and at 0.5, 1, 2, 4, 24 and 48 h after operation. Performance in the reaction time test decreased significantly in the immediate postoperative period, returning almost to preoperative values by 4 h. However, only those patients who received enflurane or propofol had returned to their performance level before surgery by 4 h, although all four groups had achieved this target by 24 h. There was a further improvement in performance at 48 h. Anxiety and stress were high before surgery and decreased rapidly in the postoperative period. The Maddox-Wing test demonstrated a significant impairment in performance in the first 1 h after surgery, which returned to normal by discharge at 4 h. There were no significant differences between the four groups in these latter tests.

Autonomy and paternalism in medicine

The role of ethics in medical practice is now receiving close scrutiny, so it is timely that ethical concepts, such as autonomy and paternalism, be re-examined in their applied contexts. As neither autonomy nor paternalism has a current universally accepted meaning, their significance varies in both ethical and clinical discussion. Of the two, autonomy has moved further from its original moral context, to the extent that it often now signifies no more than a person's expressed intention. Paternalism, characterised as the antithesis of autonomy, is widely thought not to have any role in medicine. The transforming effects of illness, which may radically alter a person's decision making capacity, are commonly ignored.

The use of midazolam and flumazenil for invasive radiographic procedures

This study has examined the use of flumazenil to improve recovery following sedation with midazolam in elderly patients undergoing invasive radiological procedures. Forty patients received either flumazenil or placebo in a randomized double-blind fashion following midazolam sedation. Nalbuphine 10-15 mg was given for premedication. All but one of the patients in the flumazenil group were fully awake immediately following the reversal agents compared to only one in the placebo group (P = 0.016). This statistically significant difference remained after 20 minutes (P = 0.029). There were no adverse effects on heart rate, blood pressure, forced expiratory volume in one second, vital capacity or oxygen saturation. The majority of patients (78% overall) could not recall their procedure. All patients said that they would be willing to undergo a similar technique in the future.

Haemodynamic effects of the position chosen for the insertion of an epidural catheter

An epidural catheter may be inserted with the patient either in the flexed left lateral or the sitting position. We have studied, non-invasively, the haemodynamic changes associated with these positions, using the thoracic bio-impedance method (BOMED NCCOM3 Monitor). Maternal arterial pressure and fetal heart rate were monitored simultaneously. Twenty healthy pregnant patients at term and 20 non-pregnant healthy controls, matched for age and height, were studied. The pregnant patients were scheduled for elective caesarean section and had singleton healthy fetuses. A significant reduction in stroke index (SI) occurred when the pregnant patients were repositioned from supine 15degrees wedged position to either flexed left lateral (P < 0.01) or sitting positions (P < 0.05). Similar reductions in SI with positioning were observed in the non-pregnant patients: flexed left lateral (P < 0.01); and sitting (P < 0.01). These changes in SI produced significant reductions in cardiac index (CI) in both groups. In the pregnant patients the CI was significantly lower in the flexed left lateral than in the sitting position (P < 0.01). Consequently maternal systolic blood pressure was lower in the flexed left lateral position (P < 0.01).

Extending a pipecuronium neuromuscular block. Increments of atracurium or vecuronium as an alternative to pipecuronium

Ten patients received increasing doses of pipecuronium at induction of anaesthesia. A dose response relationship was then constructed from which ED90 and ED95 values were measured as 43.4 micrograms.kg-1 and 50.5 micrograms.kg-1 respectively. A further 30 patients received pipecuronium in a dose sufficient to produce greater than 90% neuromuscular block. When the first contraction of the train-of-four had returned to 10% of control, a small increment of atracurium (1.1 mg), vercuronium (0.25 mg) or pipecuronium (0.21 mg) was administered, and this was repeated subsequently using the same criterion of recovery on each occasion. The duration and intensity of the block with pipecuronium increments remained constant. The duration of the block following atracurium or vecuronium was progressively less with subsequent increments until steady state was reached. The final mean durations at steady state were pipecuronium 7.37 min, atracurium 6.99 min, and vecuronium 5.15 min.

The onset of alcuronium and tubocurarine: alone and in combination

The rates of onset of neuromuscular blockade have been measured following 0.25 mg.kg-1 alcuronium (ED95), 0.51 mg.kg-1 tubocurarine (ED95), a combination of 50% of the ED95 of each and a combination of 33% of the ED95 of each. Train-of-four stimulation of the ulnar nerve was used with recording of the amplitude of the evoked compound electromyogram from the thenar prominence. The rate of increase in blockade in patients receiving the 50% combination was significantly greater than for either agent given alone, or than for the 33% combination. The mean time to 75% block of the first contraction of the train (T1) with the 50% mixture was 90 s, significantly faster than alcuronium alone (132 s), tubocurarine alone (174 s) or the 33% mixture (127 s). These latter three groups did not differ significantly. In conclusion, the rate of onset of the 50% combination resulted in a more rapid onset of neuromuscular blockade, whereas the rate of onset of the 33% combination was no different to that of either drug alone. This small degree of acceleration with agents which are known to be markedly synergistic makes it unlikely that this technique will prove to be of clinical importance.

EFFECT OF DOXAPRAM ON NEOSTIGMINE EVOKED ANTAGONISM OF VECURONIUM NEUROMUSCULAR BLOCK

We have examined the effect of doxapram on neostigmine-evoked antagonism of vecuronium neuromuscular block in a double-blind study in anaesthetized patients. Neuromuscular transmission was measured with a Datex Relaxograph. The mean time to recovery of the first contraction of the train-of-four (T1) from 25% to 75% was significantly longer in the presence of doxapram (138 (SEM 21) s; n = 23) than in its absence (95 (13) s; n = 29) (P = 0.014). The recovery of the train-of-four ratio was prolonged also in the presence of doxapram, although this difference was not statistically significant.

Effect of physiotherapy on the auditory evoked response of paralysed, sedated patients in the intensive care unit

Auditory evoked response (AER) was recorded before, during and after physiotherapy in 11 paralysed (atracurium 0.56 (SD) 0.13 mg kg-1 h-1), sedated (propofol 2.2 (1.0) mg kg-1 h-1; fentanyl 4.4 (2.3) micrograms kg-1 h-1) and critically ill patients undergoing ventilation in the intensive care unit (ICU). The latency of the negative wave, NB, was reduced by physiotherapy (mean 44.8 (SD) 7.9 ms before, 41.0 (6.8) ms during (P less than 0.01, non-parametric Friedman test) and 45.6 (6.3) ms after physiotherapy); NB amplitude showed no consistent change (-0.81 (1.4) microV, -0.81 (1.5) microV and -0.71 (1.3) microV, respectively). NB latency responded to patient arousal at constant levels of sedation and this requires further evaluation as a means of monitoring sedation in paralysed patients in the ICU.

Nasal CPAP after coronary artery surgery

Two groups of 14 patients were compared after coronary artery bypass surgery where the left internal mammary artery had been used as a conduit. One group received nasal continuous positive airway pressure for 1 h, the other group acted as a control. Mean pulmonary shunt fraction was 16.3% before, 12.6% during and 15.7% after continuous positive airways pressure. In the control group the shunt fraction fell from 17.3% to 16.8%. The reduction in shunt fraction was significantly greater with nasal continuous positive airways pressure than in the control group (p = 0.016). There was a significant reduction (p = 0.025) in respiratory rate from 18.3 to 16.7 breath.min-1 during continuous positive airway pressure. Other measured cardiorespiratory variables did not differ significantly between the groups. Visual analogue scores showed no significant difference in chest pain or mask comfort between the groups. The ease of breathing score was, however, significantly better in the continuous positive airways pressure group, 7.5 (SD 1.8) cm and control 5.6 (SD 2.6) cm.

A nasal CPAP system. Description and comparison with facemask CPAP

Nasopharyngeal pressures were compared in eight subjects breathing through either a nasal CPAP system or facemask CPAP system at a fresh gas flow of 50, 75 and 100 l.min-1. During nose breathing there was no significant difference in nasopharyngeal pressure between the two systems. During mouth breathing pressures were significantly lower with nasal CPAP. During nose breathing at 75 l.min-1 the mean inspiratory and expiratory pressures in cmH2O (SD) were 3.4 (0.68) and 5.9 (0.55) for nasal CPAP and 3.3 (0.71) and 6.3 (0.73) for facemask CPAP. The respective pressures during mouth breathing were 0.3 (0.73) and 2.9 (1.74) for nasal CPAP and 3.9 (0.73) and 5.8 (0.82) for facemask CPAP.

General anaesthesia for gamete intra-fallopian transfer

A retrospective survey was undertaken of all patients who had gamete intra-fallopian transfer (GIFT) under general anaesthesia at this hospital over an 18-month period. Of 47 patients, 21 (44.7%) became pregnant although only 10 (21.3%) proceeded to term. All of those who proceeded to term had had enflurane as part of their general-anaesthetic technique. Although a number of the patients who received halothane became pregnant, none proceeded beyond the second trimester. It would appear that the use of halothane may be inadvisable for general anaesthesia for this procedure.

Non-invasive measurement of cardiac output during induction of anaesthesia and tracheal intubation: thiopentone and propofol compared

We have investigated the haemodynamic changes in response to induction of anaesthesia and tracheal intubation in patients who received either thiopentone 5 mg kg-1 or propofol 3 mg kg-1 followed by atracurium 0.5 mg kg-1 and fentanyl 1.5 micrograms kg-1. Anaesthesia was maintained with 0.6% enflurane and 50% nitrous oxide in oxygen with assisted ventilation. Cardiac output and heart rate (HR) were monitored continuously with a transthoracic impedence monitor. Mean HR did not change after induction in each group, but increased after tracheal intubation in both groups (P less than 0.01). Mean cardiac index (CI) decreased after induction (P less than 0.05) and decreased further after tracheal intubation in both groups (P less than 0.05). There was no difference between the two groups with respect to changes in CI and HR. Mean arterial pressure (MAP) and systemic vascular resistance (SVR) did not change significantly after induction in the thiopentone group. Both variables increased from preinduction values 1 min after tracheal intubation (P less than 0.001). In contrast, both MAP and SVR decreased after induction in the propofol group (P less than 0.001) and did not differ from preinduction values 1 min after tracheal intubation. MAP and SVR were greater in the thiopentone group compared with the propofol group after induction and tracheal intubation (P less than 0.01).

Bioimpedance versus thermodilution cardiac output measurement: the Bomed NCCOM3 after coronary bypass surgery

Values obtained for cardiac output (CO) were compared using thermodilution (TD) with those obtained using bioimpedance (Bi) as measured using the Bomed NCCOM3 (Revision 6) in 28 consecutive patients in the first 24 h after coronary artery bypass surgery (CABS). In 46 paired measurements made in the first 12 h after CABS Bi values for CO were significantly lower than TD values, the limits of agreement between the two methods were also unacceptably large (mean Bi 4.38 (SD 1.40) l/min, mean TD 5.46 (SD 1.19) l/min, limits of agreement -3.05 to +0.89). In 55 paired measurements made after 12 h (all in spontaneously breathing patients) there was no significant difference between the two methods and acceptable limits of agreement, mean Bi 5.69 (SD 1.2) l/min mean TD 5.6 (SD 1.2) l/min, limits of agreement -0.99 to +1.17). The significantly lower BiCO values obtained in the first 12 h after CABS show that BiCO measurement is not consistently reliable in the intensive care setting.