Methaemoglobin (Hb, FE+++OH), a derivative of haemoglobin, is produced in the red blood corpuscles by oxidation of the ferrous porphyrin complex', but prompt reduction of the resultant ferric form maintains the normal level of methaemoglobin in the blood at low levek2 Methaemoglobin does not combine with oxygen and therefore plays no part in its carriage.Cyanosis, a blue discolouration of the skin and mucous membranes, may be observed when 5 g% or more of reduced haemoglobin, is present in the blood. A blood level of 1.5 g% or greater, of methaemoglobin, causes a similar abnormal discolouration, described as 'chocolate brown' rather than 'blue'.3Methaemoglobinaemia may cause clinical symptoms, their severity depending on the levels of methaemoglobin in the blood, but symptoms rarely occur if less than 20% is present. Levels of from 20 to 50% may cause fatigue, dyspnoea, tachycardia, headaches and dizziness. These may be a sufficient concentration to cause coma and even death on rare occasion^.^^^ This report describes the management of two cases of methaemoglobinaemia, who were deeply cyanosed and comatose on admission to hospital. Case reports Case 1A 29-year-old African female presented in coma.The history, which was obtained retrospectively after recovery of consciousness, was as follows. The patient had complained of lower abdominal pain with burning on micturition and infertility. She had decided to seek the help of the traditional inyanga or witch-doctor about 7 weeks before her admission because she was dissatisfied with the results achieved by conventional medical management. The inyanga prescribed a M.

The deleterious effects on maternal haemodynamics of inferior vena-caval compression by the gravid uterus are well e~tablished.'-~ The resultant decrease in cardiac output may constitute a threat to both mother' and f~e t u s .~-~ These problems may be alleviated by lateral displacement of the uterus,'", by tilting the patient with a wedge," or by operating in the left lateral position.'3 Lateral table tilt may be advantageous for Caesarean section using spinal analgesia, but results appear less conclusive under general anaesthesia.' MethodA hundred mothers scheduled for elective Caesarean section under general anaesthesia have been studied. Fifty patients were managed in the supine posture with no tilt; the rest were tilted, either to the left or the right side by adjustment of the operating table. A standard technique of anaesthesia was used, and the induction to delivery interval was limited to less than 12 minutes whcre possible.The patients studied were in the lower socio-economic group, but otherwise conformed to the 'clinically acceptable ideal case'.I5 Placental function was believed to be normal, and there was no evidence of pre-cclamptic toxaeniia, renal disease, hypertension, diabetes, antepartum haeniorrhage, or rhesus incompatibility with antibodies. Gestational age was between 36 and 42 weeks; cases of multiple pregnancy were excluded. Patients were not in labour and membranes were intact.Mothers were divided at randoin into two groups of fifty (group 1 and group 2). Group I received no special attention prior to entering theatre, and were operated on in thc supine position. Disturbing drops in blood pressure, or changes in heart rate, were managed by left lateral displacement of the uterus pcrforrned by the surgical assistant.

Althesin (Glaxo CT-1341), a steroid anaesthetic induction agent, was recently introduced into clinical practice.'-' The drug has a high therapeutic index and is rapidly eliminated by the liver,4, which accounts for its short duration of action. Induction of anaesthesia and recovery after Althesin is pleasant; undesirable post-anaesthetic sequelae are minimal. The haemodynamic effects of the drug have been reported;8-' ' following intravenous administration, systemic vascular resistance, central venous and arterial blood pressures are significantly reduced ; cardiac output is maintained by significant increases in heart rate.We have previously described the use of Althesin as a sole anaesthetic agent for Caesarean section." The drug appeared to be responsible for dose-related clinical and biochemical depression of the newborn. Painful awareness in the mothers and unpleasant dreaming, however, were not encountered.In this study Althesin was compared with thiopentone as an anaesthetic induction agent for Caesarean section. All subjects were tilted 10" laterally on the operating table to alleviate the effects of aorto-caval compression.13, l 4 Material and methodsThe 100 patients studied were in the lower socio-economic group, and fulfilled the criteria of 'clinically acceptable ideal cases'. All mothers, who gave their informed consent, were free of serious systemic disease and there was no evidence of placental malfunction. Gestational age was between 36 and 42 weeks; cases of multiple pregnancy were excluded. Patients were not in labour and membranes were intact.In the period preceding surgery, mothers were placed on their sides; in the operating room they were tilted 10" laterally by adjustment of the operating table. The majority were turned towards the right, according to the surgeon's preference; the direction of tilt was reversed if significant hypotension or tachycardia followed tilting.