Calculating the probability of random sampling for continuous variables in submitted or published randomised controlled trials

In a previous paper, one of the authors (JBC) used a chi-squared method to analyse the means (SD) of baseline variables, such as height or weight, from randomised controlled trials by Fujii et al., concluding that the probabilities that the reported distributions arose by chance were infinitesimally small. Subsequent testing of that chi-squared method, using simulation, suggested that the method was incorrect. This paper corrects the chi-squared method and tests its performance and the performance of Monte Carlo simulations and ANOVA to analyse the probability of random sampling. The corrected chi-squared method and ANOVA method became inaccurate when applied to means that were reported imprecisely. Monte Carlo simulations confirmed that baseline data from 158 randomised controlled trials by Fujii et al. were different to those from 329 trials published by other authors and that the distribution of Fujii et al.'s data were different to the expected distribution, both p < 10(-16) . The number of Fujii randomised controlled trials with unlikely distributions was less with Monte Carlo simulation than with the 2012 chi-squared method: 102 vs 117 trials with p < 0.05; 60 vs 86 for p < 0.01; 30 vs 56 for p < 0.001; and 12 vs 24 for p < 0.00001, respectively. The Monte Carlo analysis nevertheless confirmed the original conclusion that the distribution of the data presented by Fujii et al. was extremely unlikely to have arisen from observed data. The Monte Carlo analysis may be an appropriate screening tool to check for non-random (i.e. unreliable) data in randomised controlled trials submitted to journals.

Efficacy of cardiopulmonary resuscitation in the supine position with manual displacement of the uterus vs lateral tilt using a firm wedge: a manikin study

Prevention of aortocaval compression is essential for effective cardiopulmonary resuscitation in late pregnancy. This can be achieved by either lateral maternal tilt or lateral uterine displacement. Results from a previous manikin study show that a firm foam-rubber wedge allowed successful chest compressions whilst providing stable and reliable lateral tilt. However, it did not investigate resuscitation in the supine position with manual uterine displacement. The aim of this study was to compare the effectiveness of chest compressions in a manikin in the supine position vs lateral tilt using a foam-rubber wedge, both on the floor and on a typical patient bed. Overall, we found that compressions were easier to perform in the supine position (p = 0.007 (bed) and 0.048 (floor)), and with greater stability in the supine position on the floor (p = 0.011). The effectiveness of chest compressions was similar in both the supine/uterine displacement and the lateral tilt positions, suggesting that either method may be suitable for CPR.

Pregnant women's views on informed consent for research in labour

BACKGROUND

Studies of the optimal treatment of accidental dural puncture occurring during epidural insertion in labour are difficult for practical reasons and because of the ethical issues around seeking consent. In a recent study of accidental dural puncture, participants were assigned to one of two treatment groups and only informed about the study and consent sought, after treatment. We sought the views of parturients on the timing of consent for such a study.

METHODS

After ethical approval and written consent, 100 nulliparous women in the third trimester of pregnancy completed a structured, facilitated questionnaire, rating the acceptability of the consent process occurring: (i) in antenatal clinic; (ii) after the epidural was requested in labour; (iii) after the accidental dural puncture had occurred but before treatment; (iv) after the allocated treatment; or (v) without consent (waived consent). Results were analysed with the Friedman and Wilcoxon signed-rank tests.

RESULTS

Antenatal consent was considered the most acceptable option, whilst consent on request for epidural analgesia and after accidental dural puncture were least acceptable. Consent after treatment and waived consent were rated in-between these extremes. There was a statistically significant difference between these three groups (P<0.0001). There was a wide range of opinions on each option presented.

CONCLUSIONS

Antenatal consent was the preferred option but if this is not possible and the need for the research is strong, consent for the use of women's data after intervention, or waived consent, is acceptable to many women. It is important to seek the views of the participants themselves before planning research with difficult ethical aspects.

Reference ranges for thromboelastography (TEG(®) ) and traditional coagulation tests in term parturients undergoing caesarean section under spinal anaesthesia*

There has been little published work defining 'normal' thromboelastography (TEG(®) ) values in healthy parturients, and few large studies defining reference ranges for traditional coagulation tests in this patient group. Our aim was to establish peri-operative reference ranges for TEG and for standard laboratory coagulation tests in our pregnant population. Fifty healthy term parturients presenting for elective caesarean section under spinal anaesthesia had blood samples taken pre-operatively, on arrival in the recovery room and, in a subset of 33 women, 4 h after routine thromboprophylaxis with enoxaparin 40 mg. All three samples had TEG analysis, the first and second having standard laboratory coagulation tests in addition. Reference ranges for our pregnant population were established, demonstrating a hypercoagulable state in term parturients and a significant effect of enoxaparin. The standard coagulation reference ranges were within 98% of the local non-pregnant ranges. These reference ranges provide a useful comparator for peri-operative TEG and routine coagulation analysis in term parturients.