Introduction
According to the National Joint Registry for England and Wales, there were over 70,000 hip joint replacement procedures carried out in 2008, in contrast to the 53,000 in 2004. 91% of the 70,000 cases were recorded as primary procedures and the remaining 9% as revision procedures. 17% of the 70,000 patients were ASA grade 1, 68% grade 2 and the remaining 15% grade 3 or above1. A great proportion of patients undergoing hip arthroplasty are aged over 65 years. The physiological changes of ageing and the presence of coexisting pathology usually put the elderly patient at a greater risk from surgery and anaesthesia than their younger counterpart. This clearly questions the grading of the elderly patient in the ASA scoring system.
The debate as to which anaesthetic technique is best for elderly people has continued for many years. In many instances it is the postoperative care that is crucial in determining the outcome of surgery. The optimal control of postoperative pain in the elderly patient undergoing hip surgery may allow earlier mobilisation, lower the risk of opiate-related complications and earlier discharge from hospital.
We attempt to provide a critical review of the available anaesthetic techniques for patients undergoing hip arthroplasty, culminating in what we believe to be best clinical practice.
Pain relief
Historically, general anaesthesia (GA) has been the gold standard for major hip surgery. The recent introductions of improved techniques and catheters for continuous infusions of local anaesthetic agents in blocks have made regional anaesthesia more attractive.
Adequate analgesia postoperatively is a major aspect in the delivery of best patient care. The intense pain experienced by the patient after major hip surgery may delay mobilisation and prolong rehabilitation and hospitalisation. Postoperative pain relief after hip arthroplasty has been achieved by a variety of techniques such as;
- intravenous opiate analgesia (PCA),
- Neuraxial blockade through either epidural analgesia or spinal anaesthesia
- Psoas blocks and other peripheral nerve block techniques depending on the extent of the procedure. However, the evidence for this method in this type of surgery continues to be weak.
Modern regional anaesthesia for major hip surgery includes the use of a variety of techniques with or without a GA:
- a single bolus dose and continuous epidural top-ups via an epidural catheter,
- a single bolus dose and continuous spinal top-ups
- single bolus dose or continuous peripheral nerve blockade.
Epidural analgesia
The use of epidural anaesthesia has been linked to a reduced risk of perioperative complications such as:
- deep venous thrombosis,
- myocardial infarction,
- postoperative ileus,
- blood loss
- and deterioration of cerebral and pulmonary functions in patients who are at high risk for complications2.
Epidural analgesia has the potential to provide suitable patients with complete analgesia for as long as the epidural is continued. There may be a variety of reasons for failure including technical problems (e.g. leaks, catheters falling out, patchy or unilateral blocks and catheter occlusions) and a lack of facilities and acute pain practitioners to care for patients with epidurals.
In the MASTER study by Rigg et al. in 2002, only 50% of patients achieved satisfactory epidural analgesia for the intended duration of the block3. The complications of epidural analgesia can be related to:
- the insertion (dural puncture, neurological damage),
- the catheter in-situ (epidural haematoma, epidural abscess, catheter migration)
- and the drug (drug errors, respiratory depression, hypotension, CNS toxicity, motor block)2.
Combined spinal-epidural technique (CSE)
CSE has become increasingly popular in recent years. The advantage of the CSE is that neuraxial block can be achieved rapidly using the spinal component while the epidural catheter can be used to prolong or modify the block4.
Complications of CSE include: failure of spinal or epidural component, misplacement or migration of epidural catheter, damage to spinal needle or catheter, subarachnoid spread of drug, neurological damage, post-dural puncture headache, infection and drug related complications4.
Although both these techniques usually provide good and reliable postoperative pain relief, they may also cause urinary retention, nausea, hypotension, diminished muscle control and delayed mobilisation.
Evidence of improved outcome with neuroaxial blocks (spinal and epidural)
A meta-analysis of the effects of neuroaxial blocks showed that the postoperative mortality was reduced by 30% in patients receiving blocks2. Almost 10