What is a peripheral nerve block?
A peripheral nerve block (PNB) is an injection of local anaesthetic close to nerves to block pain signals to the brain. PNBs can be used alone or together with other pain relief medicines. They may be given as a single injection or continuously, using a catheter (drip).
Why is this question important?
Hip fractures commonly occur in older people. Surgery is usually needed to repair the bone. Hip fractures are very painful. Opioids such as morphine, which are strong painkillers, are often used to manage hip fracture pain. Older people do not tolerate high doses of opioids well. Also, people with hip fracture may have complications such as confusion, myocardial infarction and chest infection.
By reducing the use of opioids and better treating pain, PNBs may improve the mobility of people with hip fracture and reduce risks of complications.
What did we want to find out?
We wanted to know whether using PNBs compared to no nerve block (no block at all or a placebo nerve block), in people with hip fracture could reduce:
• pain on movement;
• confusion, myocardial infarction, and chest infection;
• death from any cause within six months;
• length of time until people were mobile after surgery; and
• costs of drugs used to manage pain.
What did we do?
We searched medical databases for studies that investigated the use of PNBs versus no effective nerve block (i.e. no block at all or a placebo block) for pain in people with hip fracture. Study participants had to be over 16 years of age and had to have a hip fracture. We looked for randomized controlled trials (RCTs), where the treatment people receive is decided randomly.
What we found
We included 49 studies with 3061 participants (average age 59 to 89 years); 1553 participants received PNBs and 1508 received no nerve block. Additional pain relief, including opioids, was available for all participants when required. Studies were conducted in various countries and published between 1980 and 2020. Twenty-six studies received non-commercial funding, and the source of funding was not stated for the other studies.
Main results
PNBs reduced pain on movement by 2.5 on a scale of 1 to 10, compared with no nerve block (11 studies, 503 participants). PNBs reduced the risk of confusion; for every 12 people with a hip fracture, one person less will become confused with PNBs (13 studies, 1072 participants). We did not find a difference in risk of myocardial infarction (1 study, 31 participants).
PNBs probably reduce the risk of chest infection (3 studies, 131 participants) and time to first mobilization after surgery by 11 hours (3 studies, 208 participants). We did not find a difference in deaths from any cause within six months (11 studies, 617 participants). Costs of drugs used for pain management were slightly lower when a single-injection PNB was compared to no PNB (1 study, 75 participants).
How reliable are the results?
Our confidence (certainty) in the evidence for reduced pain on movement and for reduced confusion was high; we are moderately confident in the evidence for reduced chest infection. However, we are less confident about the evidence for myocardial infarction, death, time to first mobilization, and costs of drugs used for pain management, mainly because this evidence came from small studies with few participants.
What does this mean?
We found enough good-quality evidence to support the use of PNBs in patients with hip fracture. Larger studies are required to clarify the effects of PNBs on myocardial infarction and death.
How up-to-date is this review?
This is an updated review. Evidence is up-to-date to 16 November 2019.
PNBs reduce pain on movement within 30 minutes after block placement, risk of acute confusional state, and probably also reduce the risk of chest infection and time to first mobilization. There may be a small reduction in the cost of analgesic drugs for single-injection PNB. We did not find a difference for myocardial infarction and mortality, but the numbers of participants included for these two outcomes were insufficient. Although randomized clinical trials may not be the best way to establish risks associated with an intervention, our review confirms low risks of permanent injury associated with PNBs, as found by others.
Some trials are ongoing, but it is unclear whether any further RCTs should be registered, given the benefits found. Good-quality non-randomized trials with appropriate sample size may help to clarify the potential effects of PNBs on myocardial infarction and mortality.
This review was published originally in 1999 and was updated in 2001, 2002, 2009, 2017, and 2020. Updating was deemed necessary due to the high incidence of hip fractures, the large number of official societies providing recommendations on this condition, the possibility that perioperative peripheral nerve blocks (PNBs) may improve patient outcomes, and the major role that PNBs may play in reducing preoperative and postoperative opioid use for analgesia.
To compare PNBs used as preoperative analgesia, as postoperative analgesia, or as a supplement to general anaesthesia versus no nerve block (or sham block) for adults with hip fracture. Outcomes were pain on movement at 30 minutes after block placement, acute confusional state, myocardial infarction, chest infection, death, time to first mobilization, and costs of an analgesic regimen for single-injection blocks.
We undertook the update to look for new studies and to update the methods to reflect Cochrane standards.
For the updated review, we searched the following databases: the Cochrane Central Register of Controlled Trials (CENTRAL; 2019, Issue 11), in the Cochrane Library; MEDLINE (Ovid SP, 1966 to November 2019); Embase (Ovid SP, 1974 to November 2019); and the Cumulative Index to Nursing and Allied Health Literature (CINAHL) (EBSCO, 1982 to November 2019), as well as trial registers and reference lists of relevant articles.
We included randomized controlled trials (RCTs) assessing use of PNBs compared with no nerve block (or sham block) as part of the care provided for adults 16 years of age and older with hip fracture.
Two review authors independently screened new trials for inclusion, assessed trial quality using the Cochrane Risk of Bias-2 tool, and extracted data. When appropriate, we pooled results of outcome measures. We rated the certainty of evidence using the GRADE approach.
We included 49 trials (3061 participants; 1553 randomized to PNBs and 1508 to no nerve block (or sham block)). For this update, we added 18 new trials. Trials were published from 1981 to 2020. Trialists followed participants for periods ranging from 5 minutes to 12 months. The average age of participants ranged from 59 to 89 years. People with dementia were often excluded from the included trials. Additional analgesia was available for all participants.
Results of 11 trials with 503 participants show that PNBs reduced pain on movement within 30 minutes of block placement (standardized mean difference (SMD) -1.05, 95% confidence interval (CI) -1.25 to -0.86; equivalent to -2.5 on a scale from 0 to 10; high-certainty evidence). Effect size was proportionate to the concentration of local anaesthetic used (P = 0.0003). Based on 13 trials with 1072 participants, PNBs reduce the risk of acute confusional state (risk ratio (RR) 0.67, 95% CI 0.50 to 0.90; number needed to treat for an additional beneficial outcome (NNTB) 12, 95% CI 7 to 47; high-certainty evidence). For myocardial infarction, there were no events in one trial with 31 participants (RR not estimable; low-certainty evidence). From three trials with 131 participants, PNBs probably reduce the risk for chest infection (RR 0.41, 95% CI 0.19 to 0.89; NNTB 7, 95% CI 5 to 72; moderate-certainty evidence). Based on 11 trials with 617 participants, the effects of PNBs on mortality within six months are uncertain due to very serious imprecision (RR 0.87, 95% CI 0.47 to 1.60; low-certainty evidence). From three trials with 208 participants, PNBs likely reduce time to first mobilization (mean difference (MD) -10.80 hours, 95% CI -12.83 to -8.77 hours; moderate-certainty evidence). One trial with 75 participants indicated there may be a small reduction in the cost of analgesic drugs with a single-injection PNB (MD -4.40 euros, 95% CI -4.84 to -3.96 euros; low-certainty evidence).
We identified 29 ongoing trials, of which 15 were first posted or at least were last updated after 1 January 2018.