COMMENTARIES

reactivite foetale aux stimulations sonores.J Gynecol Obstet Biol Reprod (Paris) 10,307-314. Querleu D., Lefebvre C., Titran M., Renard X., Morillion M. & Crepin G. (1984)Reactivite du nouveau-ne de moins de deux heures de vie a la voix maternelle. J Gynecol Obstet Biol Reprod (Paris) 13,125-134. Read J. A. & Miller F. C. (1977) Fetal heart rate acceleration in response to acoustic stimulation as a measure of fetal well-being. Am J Obstet Gynecoll29 (3,512-7. Rosner B. S. & Doherty N. E. (1979) The response of neonates to intra-uterine sounds. Develop Med Child Neurol21,723-729. Salk L. (1962) Mothers’ heartbeat as an imprinting stimulus. Transactions: Journal of the New York Academy of Sciences 24 ( 7 ) , 753-763. Serafini P, Lindsay M. B. J., Nagey D. A., Pupkin M. J., Tseng P. & Crenshaw C. Jr. (1984) Antepartum fetal heart rate response to sound stimulation: the acoustic stimulation test. Am J Obstet Gynecol148 (l), 4 1 4 5 . Shalev E., Benett M. J., Megory E.. Wallace K.M. & Zuckerman H. (1989) Fetal habituation to repeated sound stimulation. Is J Med Sci 25,77-80. Schmidt W., Boos R., Gnirs J., Auer L. & Schulze S. (1985) Fetal behavioural states and controlled sound stimulation. Early H u m Dev 12,145-153. Simmons F. B. & Russ F. N. (1974) Automated newborn hearing screening,the crib-o-gram.Arch Otolaryngol 100, 1-7. Spelt D. K. (1948) Conditioning of the human fetus in utero. J Exp Psycho1 38,338-346.

789

Spence M. J. & De Casper A. J. (1982) Human fetuses perceive maternal speech. Paper presented at the International Conference on Infant Studies. Austin, Texas. Starr A,, Amlie R. N., Martin W. H. & Sanders S. (1977) Devclopment of auditory function in newborn infants revealed by auditory brainstem potentials. Pediatrics 60, 831-839. Suzuki S. (1969) Nurtured by Love. Exposition Press, Smithtown, New York. Tanaka Y. & Arayama T. (1969) Fetal responses to acoustic stimuli. Pract Oto-Rhino-Luryngol31,269-273.

Trudinger B. J. & Boylan P. (1980) Antepartum fetal heart rate monitoring: value of sound stimulation. Obstet Gyriaecol55,265-268. Walker D., Grimwade J. &Wood C. (1971)Intrauterine noise: acomponent of the fetal environment.Am .I Obstet GynecollO9,Y 1-95 Weir C. G. & Lamb J. (1990) Differential sensitivity of newborns to synthetic vowel stimuli. B r J Audio1 24, 429-430. Woodward S. C., Guidozzi F., Hofmeyer J., Kent A. & Warton C. (1990) Fetal heart rate response to a vibroacousticstimulus and a music stimulus. Proc 12th Scientific Meeting, Cuthbert Crichton Research Society, Cape Town, South Africa. Woodward S. C., Guidozzi F., Coley N.. Anthony J . & De Jong P. (1992) The penetration of music into the intrauterine acoustic environment.Proc 11th Conference on Priorities in Perinatal Cure in South Africa.

Zimmer E. Z.. Divon M. Y.,Vilensky A., Sarna Z., Perctz B. A. & Paldi E. (1982)Maternal exposure to music and fetal activity. Eur J Obstet Gynecol Reprod B i o l l 3 (4). 209-213.

British Journal of Obstetrics and Gynaecology October 1992, Vol. 99. pp. 789-790

Antibiotic prophylaxis and caesarean section Although more than 10 000 women have been enrolled in controlled studies of antibiotics for the prevention of infection following caesarean section, there remains ambivalence over the efficacy. Should prophylactic antibiotics be routinely given to all women, should women undergoing an elective caesarean section receive prophylaxis, what antibiotic is appropriate, when and how should it be given, and for how long? The risk of infection after both emergency and elective caesarean section appears to be substantial. The varying outcomes such as fever, endometritis and wound infection make it difficult to estimate this risk accurately; however, one in four women in the control groups of the randomised studies developed a fever o r endometritis. The increased risk of infection associated with prolonged rupture of the membrane and length of labour is well recognised. Many obstetricians will still not acknowledge the real likelihood of infection after elective caesarean section. Although serious infectious complications are uncommon in this population, data from untreated control groups suggest that one in ten women undergoing elective caesarean section will develop a wound infection and that the incidence of fever or endometritis post-partum is similar to that in the group undergoing emergency caesarean section. Post-operative infection can certainly be reduced by the use of prophylactic antibiotics. In an overview of 69 controlled studies of antibiotics given at the time of caesarean section. there was unequivocal evidence that the use of antibiotics resulted in both clinically and statistically signifi-

cant reductions in the incidence of fever or endometritis (odds ratio 0.30; CI 0.27-0.34), wound infection (odds ratio 0.38: CI 0.31-0.45) and serious infection, e.g. pelvic abscess, peritonitis or septicemia (odds ratio 0.24; CI 0.1 9-0.30). Evidence from 17 trials of antibiotic prophylaxis for elective caesarean section confirms that prophylaxis also will reduce the risk of febrile morbidity o r endometritis (odds ratio 0.30; CI 0.21-0.42) and wound infections (odds ratio 0.45; CI 0.23-0.88). A s the rates of infection associated with elective caesarean section are lower than those of an emergency procedure there were too few serious effects in the elective section group to be able to demonstrate a beneficial effect (odds ratio 0.09; CI 0.01-1.57). Given that there is convincing evidence that antibiotic prophylaxis is indicated for all types of caesarean section, what is an appropriate antibiotic regimen? Infections are generally either wound infections, where Staphylococcus aureus is usual, o r associated with endometritis, where gram negative aerobes and anaerobes are most commonly implicated. It is reasonable to suppose that an antibiotic regimen chosen for prophylaxis should have activity against at least some of the potential pathogens, but there is no evidence that it needs to be active against all pathogens. Studies have been published using practically every antibiotic known and all are superior to placebo in reducing infection. Antibiotics with no staphylococcal activity, e.g. metronidazole, and agents with poor activity against resistant anaerobes, e.g. cefazolin, are effective. There is n o strong evidence that antibiotics with a broader spectrum of activity

790

COMMENTARIES

such as a second o r third generation cephalosporin, are any more efficacious. In the ten trials comparing the three generations of cephalosporins a trend towards an improved outcome with a second or third generation cephalosporin (odds ratio for fever or endometritis 0.82: CI 0.67-1.02) was observed but the difference was not statistically significant. Until further large controlled studies convincingly show that agents with a broad spectrum of activity are better, I currently recommend the use of cefazolin as the prophylactic agent of choice. In the absence of clinical evidence of infection prior to surgery, there is no reason to choose antibiotics such as cefoxitin, cefotetan, cefotaxime or pipericillin for prophylaxis. It is relatively easy to perform studies of prophylactic antibiotics in caesarean section, as evidenced by the vast number of published trials. The intervention is short and relatively straight-forward and infectious outcomes that are easy to measure occur often. Pharmaceutical companies are eager to include surgical prophylaxis in the approved indications for their drug and support these studies. I am concerned, however, that many of the recent studies performed lack a scientifically valid question. Comparison groups often are inappropriate, costs are not considered and as the new drug is always shown to be as effective o r better (because anything works!) iinplicit approval of the new agent is given. The current preference for studying drugs that have very broad antimicrobial activity as prophylactic agents must not be condoned. Recent trends in surgical antimicrobial prophylaxis are for shorter courses to be given, with one or at the most two doses. There have been 17 studies that have examined the question of length of prophylaxis in caesarean section: no statistically significant difference between one dose and 3-5 doses of antibiotic on fever or endometritis has been demonstrated (odds ratio 1.09: CI 0.86-1.39). In an overview of five trials that compared a one day course of antibiotics with a 3-5 day course, the longer course may have been more effective in preventing post-partum infection (odds ratio for fever or endometritis 1.80: CI 1.11-2.93). Subclinical infection already present at the time of caesarean section could explainthe failure of a short prophylactic course. Further clinical trials may be useful, however, to identify those patients in whom longer treatment is warranted. Antibiotic irrigation o r peritoneal lavage at the time of caesarean section will prevent post-partum infection and eight controlled trials have clearly shown a reduction in fever o r endometritis (odds ratio 0.24; CI 0.18-0.31) and serious infections (odds ratio 0.27: CI 0.16-0.46). When peritoneal irrigation is compared to systemic antibiotics, there is no significant difference between the groups although a trend approaching statistical significance for an increase in wound infections with antibiotic irrigation was observed (odds ratio 2.96: CI 0.99-8.91). Unfortunately. despite the thousands of women who have

been involved in trials of prophylaxis, information on adverse events following prophylactic antibiotics is scanty and generally poorly collected. Although there is an acknowledged reluctance to give any drugs in pregnancy, all antibiotics, apart from tetracycline, are likely safe for the mother and infant if appropriately administered. It has become a routine practice to try to prevent exposure of the baby to any antibiotic by giving the first dose to the mother after the cord has been clamped; while not unreasonable it probably is being over-cautious given the safety of the drugs used for prophylaxis. There is, however, the theoretical concern that prophylactic antibiotics may decrease the chance of culturing an infecting organism and this may be a valid argument for waiting until the cord is clamped, albeit at the expense of possibly decreased effectiveness of prophylaxis. Principles of surgical prophylaxis have established that the maximum concentration of antibiotic should be present in the tissues when the incision is made. A n argument against routine antibiotic prophylaxis is concern about the potential development of resistant organisms. This is a real issue but unfortunately the magnitude of the problem is unknown because few studies have prospectively looked for resistance. Shortening the duration of prophylaxis and avoiding the use of broad spectrum agents should minimize the development of resistant bacteria. The microbiology laboratory should regularly monitor the antibiotic sensitivity pattern of clinical isolates to detect changes. The evidence strongly supports the routine use of prophylactic antibiotics for caesarean section. No particular regimen is clearly superior; cefazolin is cheap and effective and, unless there are other contributing factors, should be the standard regimen. Unless infection is already present, two or at the most three doses of antibiotic are adequate and systemic treatment is preferable to local peritoneal irrigation. There is no good evidence that side effects are so significant that they outweigh the benefits of prophylaxis. The administration of prophylactic antibiotics should be standard care for patients undergoing caesarean section. Fiona Smaill McMaster University Hamilton, Ontario Canada

References Enkin M., Eleanor E., Chalmcrs I. & Hemminki E. (1989) Prophylactic antibiotics in association with caesarean section. In Effective Care in Pregnancy and Childbirrh. (Chaimers 1.. Enkin M. W. & Keirse M. J. N. C.. eds,), Oxford University Press, pp. 1246-1269. Smaill E, Enkin M. W. (1992) Prophylactic antibiotics in caesarean section. In Oxford Database of Perinatul Trials, (Chaimers I., ed), Version 1.3, Disk Issue 7.

Antibiotic prophylaxis and caesarean section.

COMMENTARIES reactivite foetale aux stimulations sonores.J Gynecol Obstet Biol Reprod (Paris) 10,307-314. Querleu D., Lefebvre C., Titran M., Renard...
245KB Sizes 0 Downloads 0 Views