No abstract

We have reviewed 5802 Caesarean sections performed during general anaesthesia. Our use of general anaesthesia had decreased from 83% in 1981 to 23% in 1994. Despite this, the incidence of failed intubation has increased from 1 in 1984 to 1 in 250 in 1994. The problems associated with general anaesthesia in the obstetric population are increasing. Asians and African/Afrocaribbeans were represented disproportionately because of the increased use of general anaesthesia in these patients. Exposure of trainees to obstetric general anaesthetics has decreased by one-third.

The Louisville Twin Study includes nearly 500 pairs of twins and their siblings who have participated in a longitudinal study of mental development, beginning in infancy and extending to adolescence. The results show that individual differences beginning in infancy and extending to adolescence. The results show that individual differences in intelligence progressively stabilized by school age, and each child followed a distinctive pattern of spurts and lags in mental development. Monozygotic twins became increasingly concordant over ages and matched each other closely for developmental trends. By contrast, dizygotic twins regressed to an intermediate level of concordance, comparable with that found for siblings and parent-offspring sets. A comprehensive home assessment was performed to identify the home/family variables that contributed to mental development. The overall results pointed to a strong developmental thrust in the growth of intelligence, which was principally guided by an intrinsic genetic ground plan. Qualitative features of home and family did, however, add significantly to prediction of offspring IQ. The results are interpreted in the context of Waddington's developmental model, and some recent advances in neurobiology and genetics are surveyed for their implications for developmental behavior genetics.

Despite the in vitro ciliotoxicity of tobacco smoke and the abnormal mucociliary clearance found in smoking related chronic bronchitis, studies of mucociliary clearance in healthy smokers have produced variable results. The nasal mucociliary clearance of saccharin and the in vitro nasal ciliary beat frequency were studied in healthy smokers and non-smokers. One of 29 smokers had a nasal mucociliary clearance time of over 60 minutes; in the remaining 28 the mean (SD) clearance time was 20.8 (9.3) minutes, which was significantly longer (p < 0.001) than the mean time of 11.1 (3.8) minutes in 27 lifelong non-smokers. There was no significant difference between the mean nasal ciliary beat frequency of 10 smokers and 10 non-smokers. There were no significant differences in mean ciliary beat frequency or mean nasal mucociliary clearance time after 10 healthy non-smoking volunteers had smoked two cigarettes each, exhaling the smoke through their nostrils. Unless there is a prompt reversal of any ciliotoxic effect of tobacco smoke when cilia are removed for in vitro examination, the defective clearance seen in chronic cigarette smokers seems unlikely to be due to slowed ciliary beat frequency. It may be due to reduction in number of cilia or to change in the viscoelastic properties of mucus. The failure to detect any acute effect of tobacco smoke is in keeping with this hypothesis.Compounds such as hydrogen cyanide, acrolein, formaldehyde, ammonia, and phenols in tobacco smoke are toxic to mammalian cilia in vitro,' and small quantities of whole smoke or its aqueous extract cause ciliostasis in human respiratory epithelium in vitro.2 ' Patients with chronic bronchitis related to smoking have been shown to have delayed pulmonary mucociliary clearance4 but studies in healthy subjects have not shown a consistent difference between smokers and non-smokers. Whole lung clearance, assessed with inhaled radiolabelled particles, has been shown by some workers to be slower in healthy smokers than in non-smokers,5 6 while others report no significant difference between these groups.7 Studies of acute exposure to tobacco smoke from one or more cigarettes have produced even more variable results, including no change,8 acceleration,9 and slowing'0 of pulmonary clearance, and a variable effect on tracheal mucus velocity." These discrepancies may be due to differences in technique. There is considerable variation between individuals in measurements of

This study demonstrates a potency ratio of 81.2 (95% CI 73.0-89.7) for equivalence between phenylephrine and ephedrine in prevention of hypotension after spinal anaesthesia for Caesarean section.