Feasibility of the current-duration approach to studying human fecundity.

Approaches for monitoring time trends in couples' fecundity and for studying its sensitivity to environmental factors are needed. Two approaches rely on the inclusion of a cross-sectional sample of couples currently "at risk" of pregnancy either with follow up (prevalent cohort) or without follow up (current-duration design). To illustrate the feasibility of the current-duration design, we contacted a random sample of 1204 French women age 18 to 44 years in 2004 and recruited those who were currently having unprotected sexual intercourse. The current duration since the beginning of unprotected intercourse was defined for 69 women (5.7%). An additional 15 women (1.2%) were planning to start trying to become pregnant within the next 6 months. Parametric methods allowed, based on current duration of unprotected intercourse, estimation of fecundity as if the couples had been followed prospectively. The estimated proportion of couples not pregnant after 12 months of unprotected intercourse was 34% (95% confidence interval [CI] = 15-54%). The accelerated-failure time model allows study of the influence of environmental factors on fecundity. As an illustration, tobacco smoking by the woman was associated with a doubling in the median duration of unprotected intercourse before pregnancy (adjusted time ratio = 2.4; 95% CI = 1.1-5.2). We quantified the influence of time trends in the prevalence of smoking on this estimate. We suggest ways to quantify or avoid other potential bias. In conclusion, it is possible to recruit a sample of couples currently having unprotected intercourse. The current-duration design appears feasible with approximately 5 times as many women eligible for study as for an incident cohort design.

Cost-effectiveness of propofol anesthesia using target-controlled infusion compared with a standard regimen using desflurane.

The cost-effectiveness of propofol anesthesia using target-controlled infusion (TCI) versus a standard regimen using desflurane for anesthesia maintenance was analyzed. This observational study consisted of 100 inpatients 18 to 75 years old with an American Society of Anesthesiologists physical status of I or II who were scheduled for otological surgery lasting less than four hours. Patients received one of two treatments. The desflurane-maintenance group received propofol 2-4 mg/kg and sufentanil 0.15-0.30 microg (as the citrate)/kg. A constant fresh gas flow of 1 L/min was used during maintenance of anesthesia. The propofol-maintenance group received TCI propofol and an additional infusion of sufentanil. Anesthesia was induced with 0.15-0.30 microg/kg. One blinded evaluator assessed the postoperative recovery from anesthesia for all patients. The cost of drugs and medical devices used during the intraoperative and postoperative periods was calculated. Effectiveness was defined as the absence of postoperative nausea and vomiting (PONV), while the cost-effectiveness of each procedure was the cost per PONV-free episode. The efficiency of each procedure represented the production of effectiveness per dollar invested. Chi-square and t tests, sensitivity analysis, and logistic regression were also performed. The only intergroup difference detected was the frequency of PONV occurring in the early recovery phase (11 in the desflurane group versus 2 in the propofol group). Of those patients requiring antiemetic rescue, 9 were in the desflurane group and only 2 were in the propofol group (p < 0.05). The TCI propofol regimen was more expensive than the desflurane regimen ($45 versus $28 per patient, respectively) (p < 0.001). The differential cost-effectiveness ratio was $94.7 per PONV-free episode. PONV 24 hours after surgery and patient satisfaction were similar between groups. A standard regimen of desflurane was more cost-effective than TCI propofol for anesthesia maintenance in achieving PONV-free episodes.