No abstract

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.

Propanidid is a good anaesthetic and analgesic agent, and, unlike the ultra shortacting barbiturates, it is non-cumulative. After intravenous injection into the maternal circulation at Caesarean section, propanidid crosses the placental barrier. Despite rapid equilibration between mother and foetus, reports indicate that drug-induced neonatal depression occurs infrequently after propanidid admini~tration.'-~ In contrast, the biodegradation of thiopentone is slow, as recovery from anaesthesia occurs by redistribution. Depression of the newborn at birth by barbiturates has been described, particularly when large doses of the drug areThe authors have previously detailed the use of propanidid as the sole anaesthetic agent for Caesarean ~e c t i o n .~ Their results confirmed the relative lack of drug induced neonatal depression with propanidid but the infants exhibited an undesirable degree of metabolic acidaemia with the technique described-a finding possibly related to the assumption of the supine position by the mother during surgery.**' This report describes the use of propanidid for the induction of anaesthesia at Caesarean section in the lateral tilt position. The results are compared with those of a previous similar series anaesthetised with thiopentone.' Material and methodsFifty patients in the lower socio-economic group were included in this study. All the mothers, who gave their consent to the investigation, fulfilled the criteria of Crawford's 'clinically acceptable ideal case'. There was no evidence of placental insufficiency, and the parturients were clinically free of serious systemic disease. Gestational age was between 36 and 42 weeks; cases of multiple pregnancy were excluded. The patients were not in labour and their membranes were intact. The pre-operative management of the mothers has been described in previous communications.'*" An infusion of Ringer's lactate solution was commenced in the

'Lissive anaesthesia', is an anaesthetic technique popularly employed for minor surgical and gynaecological procedures.' It involves the administration of a small dose of non-depolarising relaxant to a patient spontaneously breathing nitrous oxide, oxygen and anaesthetic vapour. This method is said to lessen the amount of volatile agent required, while at the same time providing a smoother anaesthetic.Tobias & Beswick' investigated the use of gallamine 40 mg with nitrous oxide trichloroethylene and oxygen after premedication with atropine alone in such a technique; they concluded that the arterial carbon dioxide tension (Paco,) was not significantly elevated by the use of this technique in healthy women undergoing minor gynaecological procedures.The study reported in this paper investigated the effects of the intravenous injection of 40 mg of gallamine triethiodide during general anaesthesia in patients undergoing minor gynaecological or surgical procedures, under oxygen, nitrous oxide and halothane anaesthesia after pethidine and atropine premedication in order to determine whether, by affecting the respiratory muscles, the relaxant adversely influences ventilatory efficiency. MethodThe 30 patients studied, who gave their consent, weighed between 50 and 80 kg, and were clinically free of cardiopulmonary or neurological disease. Haemoglobin levels were within normal limits in all cases.Premedication with pethidine 100 mg and atropine 0.6 mg was given routinely.