Anaesthesia

Electrosurgery, patient motion and some types of lighting can cause errors in saturation readout; it is recommended that probes should be shielded from ambient lighting. Intravenous dyes can introduce gross but transient errors, which may also be present in in vitro measurements. Carboxyhaemoglobin causes overestimation of fractional saturation by an amount less than, but possibly close to, the percent of carboxyhaemoglobin present. Methaemoglobin causes the pulse oximeter readout to tend towards 85%. Fetal haemoglobin and bilirubin introduce no significant error, although they may interfere with in vitro measurements. Skin pigmentation can result in a slight decrease in accuracy. Nail polish may cause up to 6% underestimation of saturation; it is recommended that probes should be mounted sideways on fingers with nail polish or long nails. Adhesive tape or a vinyl glove across the probe has no demonstrable effect on accuracy. A blood sample should be analysed by a multiwavelength in vitro oximeter when an erroneous pulse oximeter reading is suspected, although errors may be introduced in the in vitro reading by fetal haemoglobin, bilirubin and intravenous dyes.

A patient with Mönckeberg's calcinosis is presented in whom a pneumatic limb tourniquet failed to be effectitie because of calcification of the femoral artery wall. Bleeding from the operation site was noticed to be appreciably greater while the tourniquet was inflated since the cuff, though not occluding the femoral artery, acted as a very effective venous tourniquet.

Theoretical risks which might be associated with the use of tourniquets in the presence of arterial calcification are fracture of the calcified vessel wall and systemic overdose of local anaesthetic agent following attempted regional intravenous block.

The problem of tourniquet failure in general, and the dangers which might be associated with the use of tourniquets in patients with incompressible arteries, are briefly discussed.

The aim of this study was to determine the reliability and validity of relatives' assessment of patients' quality of life and to measure the agreement between patients' and relatives' responses to the Short Form 36 quality of life questionnaire, at discharge from and 6 months following intensive care treatment. Ninety‐nine patient–relative pairs were studied. Reliability was quantified by using measures of internal consistency (Cronbach's alpha and correlation coefficients) and reliability coefficients. Relatives' responses met the required standards of reliability and validity, but reliability was consistently weaker in the mental health dimension. Relatives' and patients' scores differed significantly in six dimensions at discharge; however, agreement between patients' and relatives' responses, as measured by the Kappa statistic, was fair, improved over 6 months, and was greatest in aspects concerning physical health. We conclude that relatives are able to give a good proxy assessment of functional aspects of quality of life.

Apnoeic oxygenation refers to oxygenation in the absence of spontaneous respiration or mechanical ventilation. It has been described in humans for over half a century and has seen a resurgence in interest given its potential to delay oxygen desaturation during airway management, especially with the advent of high‐flow nasal cannulae. This narrative review summarises our current understanding of the mechanisms of gas exchange during apnoeic oxygenation and its diverse range of clinical applications, including its use at induction of anaesthesia and for the facilitation of ‘tubeless anaesthesia’. Additional discussion covers use in critical care, obese, obstetric and paediatric sub‐populations. The article also highlights current research efforts aiming to enhance the evidence base for the use of this technique.

As the incidence of diabetes mellitus continues to increase in the United Kingdom, more diabetic patients will present for both elective and emergency surgery. Whilst the underlying pathophysiology of type 1 and type 2 diabetes differs, there is much good evidence that controlling the blood glucose to > 10 mmol.l⁻¹ in the peri‐operative period for both types of diabetic patients improves outcome. This should be achieved with a glucose–insulin–potassium regimen in all type 1 diabetics and in type 2 diabetics undergoing moderate or major surgical procedures. After surgery, a decrease in the catabolic hormone response resulting from good analgesia and the avoidance of nausea and vomiting should allow early re‐establishment of normal glycaemic control.

The plasma concentrations of bupivacaine and the latency and duration of anaesthesia after supraclavicular block with 30 ml of 0.5% bupivacaine were measured in 10 patients with chronic renal failure and in 10 patients with normal renal function. No significant difference was found between the two groups in respect of pharmacokinetic parameters, or in block latency or duration.

One hundred and sixty‐two Chinese women undergoing emergency Caesarean section were allocated at random on admission to the labour ward to receive one of three regimens for orally administered chemoprophylaxis against acid aspiration: ranitidine 150 mg 6 hourly with sodium citrate at induction of anaesthesia, omeprazole 40 mg 12 hourly with sodium citrate, or omeprazole 40 mg 12 hourly alone. Intragastric pH and volume were measured immediately after induction of anaesthesia. Ten patients (17%) in the omeprazole‐only group, three (6%) in the omeprazole and citrate group and one (2%) in the ranitidine group had an intragastric pH < 2.5 and volume > 25 ml (p < 0.05). The use of sodium citrate resulted in higher intragastric pH but larger intragastric volumes (p < 0.05). The sodium citrate and ranitidine regimen was the most cost‐effective among the three.