Cochrane in CORR®: Peripheral Nerve Blocks for Hip Fracture Surgery in Adults

Importance of the Topic Studies on managing hip fractures often focus on fracture reduction and implant selection [2, 13] as well as the ways to make surgery safer for patients with serious comorbidities. Researchers have good reason to set their sights on this aspect of hip fracture treatment. Ultimately, the goal is to reduce the risk of serious or life-threatening postoperative complications [3, 14]. But another important element is making the experience more comfortable for patients; hip fracture surgery is painful. This does not always receive the attention it deserves. Some comprehensive-care teams have advocated for the adoption of a multimodal approach to pain management [5, 18], aiming to reduce opioid use and its associated harms in older adults. Previous studies found peripheral nerve blocks (PNBs) to be effective for a variety of procedures [10, 11, 16, 19]. Although performing PNBs is relatively straightforward and requires minimal equipment [1, 12], integrating new techniques into institutions’ protocols has been problematic. One challenge is that many clinicians still perceive that the additional time, effort, and supervision required to perform PNBs outweighs the potential benefits [17]. Another challenge is the perception that hip fractures are too proximal to benefit from a PNB, when in fact a femoral nerve block or a fascia iliaca compartment block will provide effective analgesia to the main nerves innervating the hip joint [21]. Previous systematic reviews on the topic may have supported the views of those who were hesitant to adopt the use of PNBs after hip fracture surgery, as they found no evidence of reduction in the incidence of postoperative complications such as myocardial infarction [4, 9], delirium [9, 15, 21], and mortality [4, 9] despite the opioid-sparing effect of PNBs [9, 15, 21]. The trials included in these reviews primarily focused on pain score results, while contemporary studies have included assessments on the efficacy of PNBs on global care. Hence, we believe that the results reported in the updated Cochrane review [8] may be a gamechanger in terms of supporting the implementation of PNBs widely. Based on 43 randomized controlled trials, the authors concluded with high level of certainty that the use of PNBs provided superior analgesia of hip fracture pain and reduced the risk of acute confusional state regardless of timing of administration and type of surgery compared with no nerve block (or to a sham block). Upon Closer Inspection The authors of this Cochrane review [8] included randomized controlled trials directly comparing the use of PNBs (psoas compartment, fascia iliaca, femoral nerve, lateral femoral cutaneous and obturator) during the perioperative period (preoperative, postoperative, or as a supplement to general anesthesia) to no nerve block (or sham block). Only five studies were determined to be at risk of bias. Among the included studies, there was substantial variability in the types and PNB techniques, regimens (single injection versus continuous), timing of intervention perioperatively, and surgical technique (fixation or replacement). In an attempt to circumvent methodological diversity, subgroup analyses were performed. Although these investigations were specified a priori, no explanations were provided on what these subgroup choices were based on. Considering that postoperative pain levels are procedure-specific, with patients experiencing less postoperative pain following hip replacement compared with internal fixation [7, 20], pooling results from all types of surgery may have led to inaccurate estimation of pain reduction provided by PNBs. Nevertheless, this Cochrane review reports a clinically meaningful reduction in pain scores 30 minutes after PNB: an equivalent of -2.11 (95% CI -2.57 to -1.68) on a 11-point numerical rating scale for pain, which exceeds the minimal clinically important difference reported as ≥ 1.7 points [6]. Additionally, their results are further strengthened by a dose-dependent relationship between local anesthetic concentration and reduction in pain scores. Perhaps the most important finding of this Cochrane review is a reduced incidence of postoperative disorientation with the use of PNBs (risk ratio [RR] = 0.67 [95% CI 0.50 to 0.90]; I2 = 16%). The effects of PNBs are likely multifactorial and could be partially explained by other findings from the same review, perhaps including decreased time to mobilization in the groups that received the blocks (mean difference = -11.17 hours [95% CI -13.07 to -9.26]) and decreased risk of chest infection in those same groups (RR = 0.41 [95% CI 0.19 to 0.89]; I2 = 3%). In this Cochrane review, a subgroup analysis was performed for the localization technique, but variability in time to surgery (means ranging between 3.5 to 7.7 days after admission), anesthetic technique (neuraxial or general anesthesia), and timing of PNB and regimens, was unaccounted for and likely affect clarity of mind postoperatively. Additionally, the true incidence of delirium in these trials may have been underestimated, the definition of “confusional state” and screening methodology among the included studies were only vaguely described. Nonetheless, the number needed to treat for an additional beneficial outcome (NNTB) was estimated at 12 (95% CI 5 to 72). NNTB is the number of people needed to treat over a given period to prevent one additional person from experiencing a confusional state in comparison with control treatments; with that number being only 12, that reflects a relatively large effect size, which would seem to strongly justify considering a PNB in this context. Take-home Message This review provides strong evidence to implement PNBs in institutional protocols for patients undergoing hip fracture surgery. PNBs represent a low-risk intervention (no major complications were reported except for one case of 4-month duration of persistent numbness after a femoral nerve block), they are effective for immediate pain reduction, and may contribute to delirium prevention. Further randomized controlled trials should focus on direct comparison of PNB regimens to determine the best timing of injection. Despite high clinical heterogeneity and dubious subgroup analyses, the strength of this meta-analysis comes from its ability to be generalized to the elderly population. This review reports beneficial effects from implementation of PNBs within institutions with established protocols; those institutions were as varied as the patients they treated. While we tend to measure the effect of an intervention on major clinical outcomes such as mortality, opioid-sparing effect, or pain, it is not plausible that one intervention alone leads to drastic changes. Hence, future research should analyze interventions in context of comprehensive care, which implies more than the physical domain. Multimodal pain management is important in patients with hip fractures; the results from this Cochrane review strongly support the addition of PNBs to this regimen. As the authors mentioned [8], the 29 ongoing trials will likely be the last comparisons of PNBs against sham or no nerve block, and further research should direct their objectives toward improved regimens.

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