NIHR Signal Two types of anaesthesia are safe for hip and knee replacements but one may reduce the time spent in hospital by a few hours
Published on 15 March 2016
Neuraxial anaesthesia, administered around the nerves in the spine, was found to be as safe as general anaesthesia for people undergoing total hip or knee replacements. This review found a similar risk of dying, infection, nerve damage and blood clots in people regardless of the type of anaesthesia. Hospital stay was reduced on average by 0.4 days in the neuraxial anaesthesia group, though the significance to patients or impact on costs was not explored. Using neuraxial anaesthesia took no longer to perform than general anaesthesia.
Hip and knee replacements are two of the three most common operations performed in the NHS. Given the numbers of operations being performed, even a small reduction in length of hospital stay should save costs.
- Anaesthetics, Musculo-skeletal disorders, Orthopaedics, Surgery
Why was this study needed?
The hips and knees are the major load-bearing joints in the body and are vulnerable to damage and disease. This leads to significant pain and disability in many people, which can be successfully treated by removing the damaged joint surfaces and inserting an artificial joint. Nearly 200,000 hip or knee replacements were performed in 2013/2014 in England.
These operations can be performed under general or neuraxial anaesthesia but there is little conclusive evidence as to which technique is safer, more effective or less expensive.
General anaesthesia renders the patient unconscious. Pain is managed with drugs such as morphine during and after the surgery.
Neuraxial anaesthesia (spinal or epidural anaesthesia) involves administering a local anaesthetic around the spinal cord to numb the body from the waist down. Sedation is often used as well, to reduce anxiety and awareness of the operating room.
This systematic review aimed to compare patient-important outcomes when total hip or knee replacements were performed either using general or neuraxial anaesthesia.
What did this study do?
This systematic review identified 19 randomised controlled trials and 10 prospective observational studies, with a total of 10,488 people. The studies compared outcomes in people receiving either general (median age 67 years) or neuraxial (median age 68 years) anaesthesia when undergoing a total hip or knee replacement or both hip and knee replacement.
A high risk of bias was identified in seven out of 19 trials, and five out of 10 observational studies. The risk of bias was usually due to incomplete follow-up of patients or not blinding the people assessing outcomes as to which anaesthesia the patient received. The authors performed a subgroup analysis excluding the studies at a high risk of bias and found that there was no significant change to their results. Overall this review followed a high quality approach and we can be confident in its findings. International studies were conducted from 1985 to 2015 and current UK practice may be different in some of the detail.
What did it find?
- There was a lower risk of developing either a deep vein thrombosis (relative risk [RR] 0.51, 95% confidence interval [CI] 0.41 to 0.62) or pulmonary embolism (RR 0.36, 95% CI 0.22 to 0.60) in people receiving neuraxial rather than general anaesthesia, when anticoagulant therapy was not used. In the UK people undergoing hip or knee replacement are routinely offered anticoagulants; in this review no significant difference was found in the risk of thrombosis or embolism between groups where anticoagulants were used.
- There was no statistically significant difference between groups in other outcomes, including deaths, infections, nerve damage, nausea or vomiting.
- People receiving neuraxial anaesthesia stayed in hospital an average of 0.4 fewer days than people receiving general anaesthesia (95% CI ‑0.76 to –0.03).
- Operations using neuraxial anaesthesia were also on average 10 minutes shorter than those using general anaesthesia, although this difference was not statistically significant.
What does current guidance say on this issue?
2011 NICE Guidelines on hip fracture recommend that people undergoing an operation are offered a choice of general or neuraxial anaesthesia, after discussion with their doctor about the risks and benefits.
To prevent blood clots following surgery, 2010 NICE Guidelines recommend that people undergoing either hip or knee replacement are offered “mechanical” prevention – such as elasticated stockings – before their operation until they are mobile afterwards. NICE recommends anticoagulant drugs are given post-operatively for 28 to 35 days after a hip operation and 10 to14 days following a knee operation. The choice of drug used depends on other conditions or risks the individual may have.
What are the implications?
Neuraxial anaesthesia and general anaesthesia are each safe for total knee and/or hip operations. Neuraxial anaesthesia may reduce the time the patient needs to stay in hospital, which may reduce costs.
This review did not examine self-limiting but common side effects of general anaesthesia, such as sore throat, drowsiness or breathing difficulties, which may be a consideration when patients are choosing an anaesthetic. Other outcomes that were not considered, because of the lack of available data, were intermediate- to long-term persistent pain, patient satisfaction, rehabilitation milestones (e.g. walking ability), or long-term outcomes in activities of daily living or quality of life.
Citation and Funding
Johnson RL, Kopp SL, Burkle CM, et al. Neuraxial vs general anaesthesia for total hip and total knee arthroplasty: a systematic review of comparative-effectiveness research. Br J Anaesth. 2016;116(2):163-76.
Mayo Clinic Robert D. and Patricia E. Kern Center for the Science of Health Care Delivery and the Department of Anesthesiology at Mayo Clinic, Rochester, MN, USA.
NICE. Hip fracture: management. CG124. London: National Institute for Health and Care Excellence; 2011.
NICE. Minimally invasive total hip replacement. IPG363. London: National Institute for Health and Care Excellence; 2010.
NICE Mini-incision surgery for total knee replacement. IPG345. London: National Institute for Health and Care Excellence; 2010.
NICE. Total hip replacement and resurfacing arthroplasty for end-stage arthritis of the hip. TA304. London: National Institute for Health and Care Excellence; 2014.
NICE. Venous thromboembolism: reducing the risk for patients in hospital. CG92. London: National Institute for Health and Care Excellence; 2010.
RCOA. Anaesthetic choices for hip or knee replacement Information for patients. London: Royal College of Anaesthetists, 2014.
RCS. Surgery and the NHS in numbers. London: Royal College of Surgeons of England; 2014.
It is encouraging that neuraxial techniques shorten length of stay, which is important to patients, and there were no advantages of general anaesthesia over neuraxial anaesthesia.
The review is from US-based authors, where the practice of neuraxial anaesthesia is less than in the UK. Despite these operations being common, the quality and quantity of studies is poor. Most of the studies were over 10 years old and the majority used epidural anaesthesia, which is now rarely practiced in the UK for primary hip and knee replacements.
The perceived advantage of neuraxial anaesthesia may be lost if patients receive too much sedation.
The review is hampered by the low quantity and age of the studies. Perhaps we should rely more on good observational database investigations, such as the National Joint Registry to guide clinical practice.
Dr Richard Griffiths, Consultant Anaesthetist, Peterborough City Hospital
Spinal (or subarachnoid) anaesthesia involves the injection of a local anaesthetic into the layer of fluid which surrounds the nerves in the spine. Epidural anaesthesia is similar, but the injection is into the fatty layer which lies just outside the fluid layer. Epidural and spinal anaesthesia are grouped together within the term neuraxial anaesthesia.