Intergroup comparability is of paramount importance in clinical research since it is impossible to draw conclusions on a treatment if populations with different characteristics are compared. While an adequate randomization process in randomized controlled trials (RCTs) ensures a balanced distribution of subjects between groups, the distribution in observational prospective and retrospective studies may be influenced by many confounders.
Propensity score (PS) is a statistical technique that was developed more than 30 years ago with the purpose of estimating the probability to be assigned to a group. Once evaluated, the PS could be used to adjust and balance the groups using different methods such as matching, stratification, covariate adjustment, and weighting. The validity of PS is strictly related to the confounders used in the model, and confounders that are either not identified or not available will produce biases in the results. RCTs will therefore continue to provide the highest quality of evidence, but PS allows fine adjustments on otherwise unbalanced groups, which will increase the strength and quality of observational studies.

Background: While laparoscopic surgical procedures have various advantages over traditional open techniques, artificial pneumoperitoneum is associated with severe bradycardia and cardiac arrest. Dexmedetomidine, an imidazole derivative that selectively binds to α2-receptors and has sedative and analgesic properties, can cause hypotension and bradycardia. Our primary aim was to assess the association between dexmedetomidine use and intraoperative bradycardia during laparoscopic cholecystectomy. Methods: We performed a systematic review with a meta-analysis and trial sequential analysis using the following PICOS: adult patients undergoing endotracheal intubation for laparoscopic cholecystectomy (P); intravenous dexmedetomidine before tracheal intubation (I); no intervention or placebo administration (C); intraoperative bradycardia (primary outcome), intraoperative hypotension, hemodynamics at intubation (systolic blood pressure, mean arterial pressure, heart rate), dose needed for induction of anesthesia, total anesthesia requirements (both hypnotics and opioids) throughout the procedure, and percentage of patients requiring postoperative analgesics and experiencing postoperative nausea and vomiting and/or shivering (O); randomized controlled trials (S). Results: Fifteen studies were included in the meta-analysis (980 patients). Compared to patients that did not receive dexmedetomidine, those who did had a higher risk of developing intraoperative bradycardia (RR: 2.81, 95% CI [1.34, 5.91]) and hypotension (1.66 [0.92,2.98]); however, they required a lower dose of intraoperative anesthetics and had a lower incidence of postoperative nausea and vomiting. In the trial sequential analysis for bradycardia, the cumulative z-score crossed the monitoring boundary for harm at the tenth trial. Conclusions Patients undergoing laparoscopic cholecystectomy who receive dexmedetomidine during tracheal intubation are more likely to develop intraoperative bradycardia and hypotension.

Background: Different regional anesthesia (RA) techniques have been used for laparoscopic cholecystectomy (LC), but there is no consensus on their comparative effectiveness. Our objective was to evaluate the effect of RA techniques on patients undergoing LC using a network meta-analysis approach. Methods: We conducted a systematic review and network meta-analysis. We searched PubMed, the Cochrane Central Register of Controlled Trials (CENTRAL), Scopus, and Web of Science (Science and Social Science Citation Index) using the following PICOS criteria: (P) adult patients undergoing LC; (I) any RA single-shot technique with injection of local anesthetics; (C) placebo or no intervention; (O) postoperative opioid consumption expressed as morphine milligram equivalents (MME), rest pain at 12 h and 24 h post-operation, postoperative nausea and vomiting (PONV), length of stay; and (S) randomized controlled trials. Results: A total of 84 studies were included. With the exception of the rectus sheath block (P = 0.301), the RA techniques were superior to placebo at reducing opioid consumption. Regarding postoperative pain, the transversus abdominis plane (TAP) block (−1.80 on an 11-point pain scale) and erector spinae plane (ESP) block (−1.33 on an 11-point pain scale) were the most effective at 12 and 24 h. The TAP block was also associated with the greatest reduction in PONV. Conclusions RA techniques are effective at reducing intraoperative opioid use, postoperative pain, and PONV in patients undergoing LC. Patients benefit the most from the bilateral paravertebral, ESP, quadratus lumborum, and TAP blocks.