Discussion
This multi-institutional study was designed to determine if pain management for traumatic hip fractures using FICB reduces development of delirium and opioid consumption and improves pain. Our study demonstrated that FICB resulted in significantly lower pain scores than systemic analgesics only. However, there was no effect of FICB on delirium or opioid consumption. Both methods of acute pain management were equally effective when assessed with the primary outcome of delirium.
Despite being considered a ‘negative’ study, our findings contribute substantially to the literature because this study was designed to examine delirium, rather than pain, as the primary outcome and was powered a priori to test this hypothesis. These results, along the growing body of literature, demonstrate no clear benefit of regional blockade on delirium incidence. Prior studies that evaluated delirium report disparate findings: in patients receiving FICB, delirium was similar to control in one study (n=161, 16% continuous FICB vs 17% control, p=0.83),14 non-significantly lower than control in one study (n=65, cognitive dysfunction: 6% FICB vs 41% control),15 and significantly higher than control in one study (n=104, 20% FICB vs 6% control, p=0.03).16
The rate of delirium from these prior studies was greater than our reported rate of 5.4%. It is possible our lower delirium incidence was due to required documentation via the CAM assessment tool, or because physicians are no longer waiting to medically optimize patients for surgery. While there were no differences in delirium by FICB status, it was interesting to find that patients who developed delirium were more likely to receive a second block than those who did not develop delirium (18% vs 2%, p=0.002), and delirium was also higher in patients who had block failure than success (18% vs 5%, p=0.06). Our block failure rate of 4.5% was lower than the range of 6%–60% in the literature.17–19
Regarding opioid use, a recent meta-analysis of 11 clinical trials reported clinical inferiority of postoperative FICB to placebo for total morphine consumption.20 Our observational study also did not identify any differences in opioid consumption with FICB. We examined opioid consumption separately in the preoperative and postoperative periods because surgery and anesthesia could equalize or negate any treatment effects of FICB. After adjustment, there were no differences by use of FICB preoperatively (p=0.74) or postoperatively (p=0.51).
Similar to the literature, we reported a significant treatment benefit with FICB on preoperative and postoperative pain. Relief of postoperative pain is a valuable achievement by itself. However, it is well established that regional blockade is effective for reducing self-reported pain, and it is our view that it would be unproductive to further study pain as the primary outcome in studies examining the efficacy of FICB in geriatric hip fracture. This study provides evidence of clinical equipoise using end points of delirium and opioid requirements, and a well-controlled trial examining one of these outcomes is encouraged.
We initially anticipated that the incidence of delirium would be lower with FICB compared with systemic analgesics, partially because improved pain with FICB may reduce analgesia requirements, subsequently reducing delirium. FICB demonstrated significant benefit on self-reported pain but without a concomitant reduction in opioid consumption or delirium. The major limitation of this study is the analgesia prescribing practices at the participating institutions. Current practice is to prescribe non-opioid medications and to increase opioids (per oral then intravenous), once the patient’s pain is not adequately controlled based on self-reported pain scores. This study would have benefited from a more standardized approach to pain management that involved less subjective use of self-reported pain scores, which could partly explain our findings of no difference in opioid requirements or delirium for FICB and no FICB groups. Moreover, this study captured what was administered, not what was prescribed. Likely, there were some instances where a patient did not receive the prescribed dose in the submitted pain order set, but rather additional or fewer opioids based on patient, nurse, or family member request. As such, one interpretation of the study is that, when opioid dosages are not appreciably modified, an FICB does not reduce the rate of delirium. Either way, there are costs and hospital resources associated with regional blockade and block failure was associated with a clinically relevant increase in delirium in this study. The benefits of reducing pain scores without subsequent reductions in narcotic use or delirium should be weighed against the costs and time of the procedure and development of analgesic-related complications. One of the unforseen findings from this study is the necessity of a well-controlled randomized trial examining narcotic use or delirium.
There are additional limitations to this study. Second, the lack of randomization and uniformity in the approach to administering FICB is a major limitation. Still, it is noteworthy that the use of FICB was similar for patients who developed delirium and those who did not, overall, and when examined as type (continuous or single) timing (preoperatively or postoperatively), whether an anesthesiologist placed the block, and whether it was placed in the ED. Third, patients with hip fracture are a complex population due to their age and the wide variability in presence and severity of comorbidities. We considered myriad confounding factors, including ASA score, individual comorbidities, and patient age. We did not directly collect any markers of frailty, nor are they routinely documented in the patient’s electronic medical record. Previous studies suggest that frailty scores are prognostically superior to ASA scores in the hip fracture population, and this study could have benefited from a frailty assessment.21 22 Fourth, regional blockade fell out of favor over the course of the study. This change in practice should not be attributed to selection bias (ie, providers did not choose to place a block in patients that were expected to have better outcomes or who had more or less pain). Rather, there were a host of factors that contributed to the decision to use FICB, and it was frequently made in consultation with the care team including the orthopedic surgeon and anesthesia. Some reasons patients did not receive a block were: provider preference, procedural costs, resources were unavailable, and patients did not consent. Future trials should randomize patients to limit temporal bias that might occur with the use of nerve blocks. Finally, we excluded patients with cognitive impairment because there is insufficient data to determine the performance of the CAM and CAM-ICU tools in the setting of delirium superimposed on dementia.23 The exclusion of patients with pre-existing cognitive impairment might have prevented us from seeing differences in delirium because patients with chronic cognitive impairment are more likely to develop delirium.6 24 This important group of patients are frequently excluded from regional blockade trials even though patients with cognitive impairment receive fewer pain medications and may experience inadequate pain relief.25 In one study where these patients were not excluded, but rather given a risk score for developing delirium, FICB significantly decreased delirium in patients at intermediate risk.26 We encourage other investigators to consider evaluating patients with dementia in studies examining FICB for geriatric hip fracture.
Randomized trials to date examining the effects of nerve blocks on delirium have suffered pitfalls that differed from the limitations we encountered in our prospective observational study. A recent systematic review of eight RCTs identified small trial sizes, all conducted outside the USA, with differing block techniques and differences in timing of block placement.27 Future controlled trials might resolve these design limitations by: using 1:1 randomization; implementing a standard analgesia regimen, not based on self-reported pain; using one standardized nerve block approach, placed on arrival or preoperatively; including patients with pre-existing cognitive impairment, while ensuring the delirium assessment tool is appropriate for patients with dementia or using block randomization based on pre-existing cognitive impairment; and adequately powering the study for delirium incidence.
