A. J. Asbury

Studies in postoperative sequelae. Nausea and vomiting—still a problem

We collected data on postoperative nausea and vomiting from 3850 patients aged 11–91 years. Thirty‐seven percent of the 3244 patients who received a general anaesthetic reported nausea and 23.2% vomited. Twenty percent of the 606 patients who received a local anaesthetic reported nausea and 11.4% vomited. Of the general anaesthetic patients reporting nausea, 72.2% were women, and the mean age was lower than for those who did not (p < 0.001). Similarly for vomiting, 74.0% were women and again the mean age was lower (p < 0.001). Of the local anaesthetic patients reporting nausea, 62.0% were women and the mean age was lower than for those who did not (p < 0.001). Similarly for vomiting, 68.1% were women and again the mean age was lower (p < 0.001). Anxiety before general, but not local, anaesthesia was associated with postoperative nausea (p < 0.001) but not vomiting. Patients from the gynaecological, orthopaedic, ENT and general surgical wards had higher incidences of postoperative nausea and vomiting. Linear visual analogue pain scores were higher in patients with postoperative nausea and vomiting in both general and local anaesthesia groups (p < 0.001).

Inhaled fentanyl as a method of analgesia

A study was undertaken to investigate the use of fentanyl by aerosol for postoperative analgesia. Seven patients had placebo, six received fentanyl 100 μg and seven were given fentanyl 300 μg. A significant improvement in postoperative pain, as assessed by linear visual analogue scale, was achieved in the higher dose group, and in both fentanyl groups the time to alternative analgesia was significantly longer than in the control group. Serum fentanyl levels after inhalation of 100 μg reached a plateau around 0.04 ng/ml and after 300 μg at around 0.1 ng/ml after 15 minutes. Inhaled fentanyl may have a useful analgesic effect despite these low serum levels; this supports the hypothesis that the mode of analgesia from inhaled opioids may be different from that after other routes of administration. There were no adverse effects such as respiratory depression, bronchospasm, nausea or drowsiness.

Patient knowledge of anaesthesia and peri-operative care.

One hundred and sixty six patients were questioned by means of a multiple choice questionnaire, to determine their knowledge of peri‐operative care, anaesthesia and the role of anaesthetists. In general, knowledge was good, but there were some important misconceptions; in particular, 28.3% of respondents thought that fasting referred to food only, and not to fluid intake. In addition, 47.6% of respondents considered pain to be a necessary part of the healing process and 38.6% believed that it was something that just had to be endured. When forthcoming anaesthesia is discussed, anaesthetists need to ascertain that patients really do understand the language used.

Music in theatre: not so harmonious. A survey of attitudes to music played in the operating theatre.

Music played to staff in the operating theatre is thought to improve surgeons’ concentration but its effects on other theatre staff are unknown. We surveyed 200 anaesthetists to determine the prevalence of music playing in the operating theatre and anaesthetists’ attitudes to it. The response rate was 72% and of these 72% (104) worked in a theatre where music was played regularly. Around 26% of the sample felt that music reduced their vigilance and impaired their communication with other staff while 11.5% felt that music might distract their attention from alarms. Fifty‐one per cent felt that music was distracting when a problem was encountered during the anaesthetic.

A novel device for patient-controlled sedation: laboratory and clinical evaluation of the Baxter Intermate LV250 infusor and patient-control module

The Baxter Intermate LV250 infusor is a large capacity, high flow mechanical infusor, designed to deliver viscous solutions and suspensions. The objective of the laboratory study was to evaluate the LV250 infusor when used with either 0.9% sodium chloride solution or an emulsion, propofol 1%. Following this, the LV250 infusor with the patient‐control module was assessed in the clinical setting as to its suitability for use in patient‐controlled sedation with a propofol and lignocaine mixture. Between reservoir volumes of 250 and 55 ml, the L V250 infusor was found to infuse a propofol 1% and lignocaine mixture at a lower flow compared with the sodium chloride solution, 170ml.h‐1 and 260ml.h‐1 respectively. The lower flow with the propofol mixture may be a result of its higher viscosity. All patients using the LV250 infusor for patient‐controlled sedation found it easy to use and stated that they were able to achieve their desired level of sedation. All patients maintained arterial oxygen saturations above 95%. The LV250 infusor performed reliably and with little inter‐device variation, and with the patient‐control module could be used as an alternative to electronic devices for providing patient‐controlled sedation. Compared with electronic infusors, its advantages include compactness and simplicity of design.

The occupational hazard of human immunodeficiency virus and hepatitis B virus infection

We have conducted a postal survey of members of the Association of Anaesthetists to ascertain perceived risks and preventive measures adopted with regard to the occupational hazard of Human Immunodeficiency Virus and Hepatitis B Virus infection. Despite recognition of the infection risk and the adoption of appropriate measures when managing known infected patients, the majority of anaesthetists have not implemented simple precautions in their daily routine work. Less than 16% of respondents routinely wear gloves and more than one in three still resheath needles. It would appear that the recommendations of the Association with regard to universal safety precautions have not been implemented by the majority of its members.

An evaluation of the Datex Normac anaesthetic agent monitor

A new monitor for volatile anaesthetics, the Datex Normac, was assessed in the laboratory and operating theatre. The instrument had a warm up time of 90 minutes from cold, but only 5 minutes from standby. Zero drift was less than 0.01% over 7 hours, and repeated measurements of gain showed a coefficient of variation of less than 1%. However, gain drift of 6% occurred when the instrument was switched off between periods of use. Signal noise was less than 0.02 vol % on a new instrument, but was about six times greater on an instrument that had been in use for a year. The response time of 550 ms is short enough to allow breath by breath monitoring. When the instrument was calibrated on the enjurane setting, measurements made on the enflurane, halothane and isojlurane settings were accurate to within 6% of the reading. This is satisfactory for clinical purposes, but not for more demanding applications. Calibration canisters are available, and two that we tested were accurate to better than 0.1 vol %. Nitrous oxide, carbon dioxide and water vapour have very small effects on the monitor. The instrument provided trouble‐free monitoring in theatre.

The effect of music on anaesthetists' psychomotor performance.

Music is frequently played in operating theatres, but may prove distracting to anaesthetists. We undertook a laboratory‐based study of the effects of music on the psychomotor performance of 12 anaesthetic trainees. Using part of the computer‐based PsychE psychomotor evaluation programme, we were unable to demonstrate any effect of self‐chosen music, silence, white noise or classical music on their performance in these tests.

Pupil response to alfentanil and fentanyl. A study in patients anaesthetised with halothane.

The pupillary response to alfentanil, fentanyl and a saline placebo was measured in patients anaesthetised in a standard manner with halothane, to determine whether the pupil diameters changed in a way which could be distinguished from background activity. Measurements were made to the nearest 0.1 mm using a purpose‐built pupillometer. The response to the drugs can be clearly distinguished from the background activity seen in the placebo group. The time courses of constriction caused by the two drugs are significantly different from the placebo group responses. The time to maximum to response with alfentanil is 4 minutes compared with 8 minutes for fentanyl. Both drugs produced at least 35% reduction in mean pupil diameter compared with the placebo group. The duration of the response to alfentanil was 25 minutes, whereas the fentanyl response lasted more than one hour.

Dinamap arm and thigh arterial pressure measurement.

Two automatic arterial pressure monitors (Model 1846 P) were used in 30 patients to measure arterial pressures and heart rates in the thigh and arm. Significant differences were found in thigh‐arm sytolic (p < 0.001) and diastolic pressures (p < 0.05). Arm pressures could be predicted from leg pressures and correction factors are suggested. Mean pressures in the thigh approximated more closely to the calculated mean pressures than in the arm. These differences were of little clinical importance.