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The design of clinical trials is typically based on marginal comparisons of a primary response under two or more treatments. The considerable gains in efficiency afforded by models conditional on one or more baseline responses has been extensively studied for Gaussian models. The purpose of this article is to present methods for the design and analysis of clinical trials in which the response is a count or a point process, and a corresponding baseline count is available prior to randomization. The methods are based on a conditional negative binomial model for the response given the baseline count and can be used to examine the effect of introducing selection criteria on power and sample size requirements. We show that designs based on this approach are more efficient than those proposed by McMahon et al. (1994).

SummaryThe effect of intra-operative fluid and dextrose administration upon recovery was tested in a randomised, double-blind trial. Key wordsComplications; postoperative. Fluid balanceMost anaesthetists suspect that the well-being and recovery of patients after anaesthesia and surgery is prejudiced by dehydration and possible starvation, and recent studies',2 have suggested that patients benefit significantly from the administration of peri-operative fluid. However, some questions remained unanswered, since the relative contribution of a fluid load compared with a fluid load with calories was not studied, nor was the fluid load related to body weight, and only subjective measurements of recovery were used.We investigated the relative effects of fluid alone compared with calorie-containing fluid, in a controlled, double-blind study with objective tests of psychomotor function during recovery. MethodThe protocol was approved by the local ethics committee. An information sheet was sent to each patient before admission, and informed, witnessed, verbal consent was obtained. Seventy-five female patients aged 18 to 40 years were studied in a double-blind, randomised, single-centre trial. They were ASA 1 or 2, took no routine medication and underwent day-case laparoscopic examination.Day case laparoscopic examination was chosen to provide a population with a relatively high rate of side effects7 and one might expect any major influence or improvement to be significant for the numbers studied. Patients were seen before operation by one of the authors for baseline assessments and to enable demographic details to be recorded. No premedication was prescribed. Each patient was allocated a t random to one of three groups.The patients were usually in the morning theatre session, and a t worst would endure a period of approximately 16 hours' fast, from 2100 hours the previous night until 1300 hours in the afternoon after surgery. The control group received no peri-operative fluid, the compound sodium lactate (CSL) group 20 mljkg compound sodium lactate solution, and the compound sodium lactate solution/ dextrose (CSLjdext) group 20 ml/kg compound sodium lactate solution with 1 g/kg added dextrose. The fluid load was based on a daily water requirement of approximately 30 ml/kg. The caloric supplement was chosen to represent a typical oral intake which would not induce hyperglycaemia.An 18-G intravenous cannula was inserted under local anaesthesia, and connected to a premeasured bag of the designated infusion fluid. The intravenous fluid containers were covered by a large paper bag for concealment, and the infusion was given over 45 minutes. The blood glucose level was measured a t the time of intravenous cannulation using a dextrostix (BM-test-glycemi, Boehringer Mannheim, W. Germany) and reflomat system (Reflomat, Boehringer Mannheim, W. Germany), which correlated well with local laboratory assays.

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The effect of intra-operative fluid and dextrose administration upon recovery was tested in a randomised, double-blind trial. Three groups of 25 patients, each undergoing laparoscopic examination as day cases, were studied. The two groups who received fluid (20 mljkg compound sodium lactate solution) showed signijicant improvement ( p < 0.05) in the variables that reflected hydration. The Jluid group who also received dextrose ( I glkg) exhibited further signijicant improvement. Intra-operative fluid and dextrose administration appears to confer some benefit upon recovery in patients who have minor surgery.