Continuous Measurement of Multiple Inert and Respiratory Gas Exchange in an Anaesthetic Breathing System by Continuous Indirect Calorimetry

A method was tested which permits continuous monitoring from a breathing system of the rate of uptake of multiple gas species, such as occurs in patients during inhalational anaesthesia. The method is an indirect calorimetry technique which uses fresh gas rotameters for control, regulation and measurement of the gas flows into the system, with continuous sampling of mixed exhaust gas, and frequent automated recalibration to maintain accuracy. Its accuracy was tested in 16 patients undergoing pre-cardiopulmonary bypass coronary artery surgery, breathing mixtures of oxygen/air and sevoflurane with/without nitrous oxide, by comparison with the reverse Fick method. Overall mean bias [95% confidence interval (CI)] of rate of uptake was 17.9 [7.3 to 28.5] ml min⁻¹ for oxygen, 0.04 [−0.42 to 0.50] ml min⁻¹ for sevoflurane, 10.9 [−16.1 to 37.8] for CO₂, and 8.8 [−14.8 to 32.4] ml min⁻¹ for nitrous oxide where present. The method proved to be accurate and precise, and allows continuous monitoring of exchange of multiple gases using standard gas analysis devices. Stuart-Andrews C, Peyton P, Humphries C, Robinson G, Lithgow B. Continuous measurement of multiple inert and respiratory gas exchange in an anaesthetic breathing system by continuous indirect calorimetry.     

A fibreoptic intubation technique for children with mucopolysaccharidoses using the laryngeal mask airway

Children with mucopolysaccharidoses present the anaesthetist with both a difficult airway and often an impossible intubation using conventional techniques. A technique for airway management and tracheal intubation is described utilizing the Brain laryngeal mask airway, the fibreoptic bronchoscope, a guide wire and a ureteral dilator. Two case reports of children with mucopolysaccharidoses are presented who were managed successfully with this technique. The advantages of the technique are discussed.     

Sublingual Glyceryl Trinitrate for Uterine Relaxation at Caesarean Section—a Prospective Trial

Summary: We report a prospective study on the use of sublingual glyceryl trinitrate at Caesarean section to induce uterine relaxation; 23 women were entered into the study with both emergency and elective cases considered. A metered dose spray was used to deliver a dose of 400 or 800 microgrammes of glyceryl trinitrate to the women. There were no major side-effects of hypotension or postpartum haemorrhage. The mean maximal systolic blood pressure drop in the patients following drug administration was 18% of the systolic pressure prior to drug administration. Subjective assessment of uterine tone showed the uterus to contract well postdelivery in response to standard oxytocic regimens. Minimal maternal side-effects were reported. We conclude that glyceryl trinitrate is a safe form of uterine relaxation at Caesarean section which may be used in emergency situations and may also be given prophylactieally in cases such as breech presentation and in delivery of the preterm infant where fetal trauma is possible. The use of a metered-dose sublingual spray is ideally suited to obstetric practice, being both easy to use and also rapidly administered.