Meta-epidemiology and the MetaBLIND study: Response to Tack

In 2020 we published MetaBLIND, a large meta-epidemiological study on the impact of masking on effect estimates in randomized clinical trials (RCTs). While masking is an established methodological practice in RCTs it is not clear to what extent results of non-masked RCTs are biased. Surprisingly, we found no evidence of an impact of masking on effect estimates, on average. Michiel Tack commented on the MetaBLIND study, and here we respond. The issues he raised were examples of standard themes when interpreting meta-epidemiological studies, which we have discussed at some length elsewhere, and did not warrant change of our conclusion. We maintain that the MetaBLIND results do not provide a sufficient basis for recommending abandoning masking as a methodological safeguard.

Problems with the MetaBLIND study: An examination of data on blinding patients in trials with patient-reported outcomes

MetaBLIND is the largest meta-epidemiological study on the impact of blinding in randomized trials to date. We examined MetaBLIND data on the impact of blinding patients on patient-reported outcomes. 68 out of 132 included trials tested knowledge recall and had questionable relevance to clinical trials. In 17 out of 18 comparisons, the number of trials in the blinded or nonblinded group was 2 or lower. In several key trials, the blinding status was uncertain. Effect sizes compared in MetaBLIND appear to reflect random differences in study design and setting rather than the impact of blinding trial participants.

Deep Sedation or Paracervical Block for Daycare Gynecological Procedures: A Prospective, Comparative Study

Context:

Many minor gynecological procedures are done for diagnostic and therapeutic reasons. A balance has to be struck between ability to discharge a patient at the earliest with minimum procedure-related discomfort to ensure patient safety as well as satisfaction.

Aim:

This prospective randomized study was designed to compare deep sedation versus paracervical block for minor gynecological surgeries comparing the time to discharge readiness, pain after the procedure, and overall patient satisfaction.

Setting and Design:

This prospective randomized comparative study was conducted at a tertiary level hospital after institutional ethics committee approval and registry of trial at CTRI (India).

Methods:

Seventy young women underwent minor gynecological procedures under these two modes of anesthesia. Time to discharge readiness from hospital to home was assessed using modified postanesthesia discharge score system (PADSS). Pain after procedure as well as patient satisfaction was evaluated. Patients were also asked whether they would recommend the same anesthetic technique for the procedure in the future. Answers were noted on a Likert scale.

Results:

Patients were ready to be discharged faster in deep sedation group compared to paracervical block group based upon modified PADSS score (1 h 9.6 min vs. 1 h 18 min) (P = 0.005). Pain in the perioperative period was analyzed using repeated-measures ANOVA and found to be significantly lesser in deep sedation group when considered till 80 min after surgery. The mean satisfaction score in patients who underwent deep sedation was 91.24 (standard deviation [SD] 2.8) compared to patients given paracervical block which was low at 64.67 (SD 15.8). All patients given deep sedation were ready to recommend the anesthesia technique as compared to only 53.3% of patients who were given paracervical block.

Conclusions:

Deep sedation may be preferred over paracervical block for daycare minor gynecological procedures.

Methods of pain control during endometrial biopsy: A systematic review and meta-analysis of randomized controlled trials

AIM

To review effectiveness of methods for reducing pain during endometrial biopsy.

METHODS

PubMed, Scopus, Cochrane Central Register of Controlled Trials and ClinicalTrials.gov databases were searched for randomized controlled trials that examined effectiveness of pain control methods for endometrial biopsy. Risk of bias was assessed from sequence generation, allocation concealment, blinding, incomplete outcome data and selective outcome reporting. Heterogeneity was examined from forest plot, statistical tests of homogeneity, and I² statistic. For meta-analysis of pain scores, weighted mean difference with 95% confidence interval (CI) were estimated.

RESULTS

Twenty-six studies were included in the review. Marginally significant reduction in the pain score during the procedure in participants with intrauterine lidocaine relative to control was observed (mean difference [MD] -1.31, 95% confidence interval [CI] -2.70 to 0.09, P = 0.07). Subgroup analysis showed that in studies that used low-pressure suction devices, intrauterine lidocaine was associated with statistically significant reduction in pain during the procedure (MD -2.22, 95% CI -3.72 to -0.73, P = 0.004). There was a significantly lower pain score during biopsy in the anesthetic spray group compared to control (MD -0.96, 95% CI -1.53 to -0.39, P = 0.001). Significant heterogeneity on types of intervention and outcome measures among studies that examined paracervical block and nonsteroidal anti-inflammatory drugs (NSAID) was observed. However, paracervical block and NSAID were associated with significant pain reduction compared to placebo in most of the related studies.

CONCLUSION

Intrauterine anesthetics, anesthetic cervical spray, paracervical block and oral NSAID provide effective pain control during endometrial biopsy.

Paracervical local anaesthesia for cervical dilatation and uterine intervention

BACKGROUND

Cervical dilatation and uterine intervention can be performed under sedation, local or general anaesthesia for obstetrics and gynaecological conditions. Many gynaecologists use paracervical local anaesthesia but its effectiveness is unclear. This review was originally published in 2009 and was updated in 2013.

OBJECTIVES

The objectives of this review were to determine the effectiveness and safety of paracervical local anaesthesia for cervical dilatation and uterine intervention, versus no treatment, placebo, other methods of regional anaesthesia, sedation and systemic analgesia, and general anaesthesia.

SEARCH METHODS

We reran our search to August 2013. We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2013, Issue 8), MEDLINE (1966 to August 2013), EMBASE (1980 to August 2013), and reference lists of articles. The original search was performed in January 2006.

SELECTION CRITERIA

We included randomized or controlled clinical studies involving women who underwent cervical dilatation and uterine intervention for obstetrics and gynaecological conditions. We included studies which compared paracervical anaesthesia with no treatment, placebo, other methods of regional anaesthesia, systemic sedation and analgesia, or general anaesthesia.

DATA COLLECTION AND ANALYSIS

Two authors independently evaluated the studies, extracted data, and checked and entered data into Review Manager.

MAIN RESULTS

This updated review includes nine new studies, in total 26 studies with 28 comparisons and involving 2790 participants. No study of local paracervical versus general anaesthesia met our criteria. Ten studies compared local anaesthetic versus placebo. Paracervical local anaesthetic (PLA) reduced pain on cervical dilatation with a standardized mean difference (SMD) of 0.37 (95% CI 0.17 to 0.58) and a relative risk (RR) of severe pain of 0.16 (95% CI 0.06 to 0.74). PLA also reduced abdominal pain during, but not after, uterine intervention (SMD 0.74, 95% CI 0.28 to 1.19); there was no evidence of any effect on postoperative back or shoulder pain. Comparisons against no treatment did not demonstrate any effect of PLA. Five studies compared paracervical block with uterosacral block, intracervical block, or intrauterine topical anaesthesia. Two of these studies showed no significant difference in pain during the procedure. Compared to intrauterine instillation, PLA slightly reduced severe pain (from 8.3 to 7.6 on a 10-point scale), which may be negligible. Six studies compared PLA with sedation. There were no statistically significant differences in pain during or after the procedure, postoperative analgesia requirement, adverse effects, patient satisfaction, and the operator's perception of analgesia. We performed risk of bias assessment using six domains and found that more than half of the included studies had low risk of bias.

AUTHORS' CONCLUSIONS

We found that no technique provided reliable pain control in the 26 included studies. Some studies reported that women experienced severe pain (mean scores of 7 to 9 out of 10) during uterine intervention, irrespective of the analgesic technique used. We concluded that the available evidence fails to show whether paracervical block is inferior, equivalent, or superior to alternative analgesic techniques in terms of efficacy and safety for women undergoing cervical dilatation and uterine interventions. We suggest that woman are likely to consider the rates and severity of pain during uterine interventions when performed awake to be unacceptable in the absence of neuraxial blockade, which are unaltered by paracervical block.

Paracervical local anaesthesia for cervical dilatation and uterine intervention

BACKGROUND

Cervical dilatation and uterine intervention can be performed under sedation, local or general anaesthesia for obstetrics and gynaecological conditions. Many gynaecologists use paracervical local anaesthesia (PLA) but its effectiveness is unclear.

OBJECTIVES

To determine the effectiveness and safety of paracervical anaesthesia for cervical dilatation and uterine intervention when compared with no treatment, placebo, other methods of regional anaesthesia, systemic sedation and analgesia, or general anaesthesia (GA).

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2006, Issue 1), MEDLINE (1966 to January 2006), EMBASE (1980 to January 2006) and reference lists of articles.

SELECTION CRITERIA

We included randomized or controlled clinical studies involving cervical dilatation and uterine intervention for obstetric and gynaecological conditions.

DATA COLLECTION AND ANALYSIS

Two authors independently evaluated studies, extracted data, checked and entered data into Review Manager.

MAIN RESULTS

We included 17 studies involving 1855 participants. No study of PLA versus GA met our criteria; eight studies compared PLA versus placebo. Injection of local anaesthetic was slightly less painful than injection of saline placebo, a reduction of 0.87 points (95% CI 0.14 to 1.60) on a 10-point pain scale. Compared to placebo, PLA reduced abdominal pain during uterine intervention equivalent to two or three points on a 10-point pain scale and reduced the risk of severe pain (RR 0.16, 95% CI 0.06 to 0.74). There was no evidence that PLA reduced pain after the uterine intervention and little evidence for any effect on postoperative back or shoulder pain. Pain reduction by PLA was not confirmed in four studies that compared PLA with no treatment. Three studies compared PLA with uterosacral block; intracervical block; and intrauterine topical anaesthesia. Two of these studies showed no significant difference in pain during the procedure. Compared to intrauterine instillation, PLA slightly reduced severe pain (from 8.3 to 7.6, on a 10-point pain scale), which may be negligible. This benefit appeared to be greater for women who required cervical dilatation. Two studies compared PLA with sedation. There were no statistically significant differences in pain during or after the procedure, postoperative analgesia requirement, adverse effects, patient satisfaction, and the operator's perception of analgesia.

AUTHORS' CONCLUSIONS

No technique provided reliable pain control in the 17 included studies. Some studies reported that women experienced severe pain (mean scores of 7 to 9 out of 10) during uterine intervention, irrespective of the analgesic technique used. We concluded that the available evidence fails to show whether paracervical block is inferior, equivalent or superior to alternative analgesic techniques, in terms of efficacy and safety, for women undergoing uterine interventions.