British journal of anaesthesia
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Randomized Controlled Trial Comparative Study Clinical Trial Controlled Clinical Trial
Comparison of the effects of sub-hypnotic concentrations of propofol and halothane on the acute ventilatory response to hypoxia.
To compare the effects of sub-anaesthetic concentrations of propofol and halothane on the respiratory control system, we have studied the acute ventilatory response to isocapnic hypoxia (AHVR) in 12 adults with and without three different concentrations of propofol and halothane. Target doses for propofol were 0, 0.05, 0.1 and 0.2 of the effective plasma concentration (EC50 = 8.1 micrograms ml-1). Target doses for halothane were 0, 0.05, 0.1 and 0.2 minimum alveolar concentration (MAC = 0.77%). ⋯ The decline in AHVR with increasing dose for both drugs was statistically significant (ANOVA, P < 0.001); there was no significant difference between the two drugs with respect to this decline. Normoxic ventilation with propofol declined from 13.2 (1.6) litre min-1 (0.01 EC50) to 8.3 (0.9 litre min-1 (0.26 EC50), and with halothane declined from 13.5 (2.0) litre min-1 (0 MAC) to 11.8 (1.6) litre min-1 (0.2 MAC). This was significant for both drugs (ANOVA, P < 0.001).
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Randomized Controlled Trial Comparative Study Clinical Trial
Cerebrospinal fluid progesterone in pregnant women.
To assess the possible relationship between an increase in progesterone concentration in cerebrospinal fluid (CSF) and enhancement of spread of spinal anaesthesia, we have measured CSF progesterone concentrations in 134 patients undergoing spinal anaesthesia with hyperbaric amethocaine 8 mg. Patients were allocated to one of five groups according to the gestational period: non-pregnant group (n = 13), first trimester group (8-12 weeks, n = 16), second trimester group (13-24 weeks, n = 18), third trimester group (25-36 weeks, n = 38) and term group (37-41 weeks, n = 49). Progesterone concentration in CSF was higher in the third trimester and term groups than in the non-pregnant, first trimester and second trimester groups. ⋯ Although an increase in CSF progesterone concentration in the second trimester group was similar in magnitude to that observed in the first trimester group, enhanced spread of spinal anaesthesia, comparable in magnitude with that observed in the term group, occurred in the second trimester group. There was no significant correlation between CSF progesterone concentration and spread of spinal anaesthesia in any of the groups. These data suggest that not only a minimum level of progesterone in CSF but also a certain duration of exposure to elevated CSF progesterone concentrations may be necessary for enhancement of spread of spinal anaesthesia, and that values of CSF progesterone concentration do not correlate directly with enhancement of spread of spinal anaesthesia.
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We present an unusual complication of left internal jugular vein catheterization in an 11-week-old infant which we believe has not been described previously. After failed subclavian catheterization, a left internal jugular catheter was placed without apparent difficulty. Confirmatory chest x-ray revealed that the tip of the catheter was in the extradural space.
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S.c. infusions of morphine have been advocated for postoperative analgesia in children, but experience with this technique is limited. We report a case in which an s.c. infusion of morphine given after operation to a neonate failed to provide acceptable analgesia until the child had been adequately rehydrated. However, restoration of peripheral perfusion with a fluid challenge was followed by sudden ventilatory arrest which required resuscitation and naloxone infusion. This report emphasizes the dangers of giving morphine by a peripheral route in the dehydrated or hypovolaemic infant.
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The physiological changes occurring during pregnancy and labour may reveal or exacerbate the symptoms of hypertrophic obstructive cardiomyopathy (HOCM). We describe the management of labour in a patient with severe HOCM during which esmolol, a short-acting beta adrenergic antagonist, was used together with extradural analgesia and invasive cardiovascular monitoring to achieve an assisted vaginal delivery with minimal haemodynamic disturbance. The effects on the infant are described and the literature on the use of esmolol in pregnancy is reviewed.