By: 1 March 2011

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;

  1. intravenous opiate analgesia (PCA),
  2. Neuraxial blockade through either epidural analgesia or spinal anaesthesia
  3. 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:

  1. a single bolus dose and continuous epidural top-ups via an epidural catheter,
  2. a single bolus dose and continuous spinal top-ups
  3. 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 10,000 patients in 141 randomised controlled trials were analysed. However, the majority of fatalities occurred in a fairly small number of the studies involving a minority of the total number of patients2. This raises concerns over the ability to extrapolate these results into clinical practice.

Rigg et al. in 2002 performed a prospective randomised controlled trial of epidural anaesthesia and analgesia versus general anaesthesia and postoperative systemic opioids in high risk patients undergoing major surgery (MASTER study)3. Epidural analgesia was continued for three days after operation. The results showed that there was no significant difference in overall mortality between the groups. However, they did show a reduced incidence of pulmonary complications and thromboembolic events and significantly better analgesia in the epidural group3.

Patient-controlled analgesia (PCA)
The underlying principle of PCA is that the patient self administers and thereby controls the dose of analgesia. This allows each patient to receive the appropriate dose of analgesia for them at that particular time in their postoperative course. Therefore, it is assumed that the patient will have been titrated to comfort with a loading dose of opioid prior to the commencement of PCA. Variables of the PCA prescription are the choice of opioid drug and settings of the PCA pump i.e. bolus dose, lockout interval, dose limits and background infusion5.

The widely used morphine PCA regimen of a 1mg bolus dose with a 5min lockout interval and no background infusion allows the patient to administer a maximum of 12mg/hr. This maximum dose is adequate for the majority of patients in pain and ineffective analgesia is usually due to failure to use the device properly. Pre-operative patient education and postoperative re-enforcement are more likely to improve analgesia than merely increasing the bolus dose or introducing a background infusion5.

In addition to being an efficacious analgesia, several advantages such as high patient acceptability, faster postoperative recovery, earlier hospital discharge and reduced nursing time have been attributed to PCA. However side effects of opioid drugs include nausea, vomiting, respiratory depression, reduced gut motility, and urinary retention, the most important of which, particularly in elderly patients, is respiratory depression5.

Continuous peripheral nerve blocks
Absolute and relative contraindications include: skin infection at or near the puncture site, systemic infection, pyrexia, bleeding diasthesis, systemic anticoagulation, changing neurology and peripheral neuropathy and risk of compartment syndrome.

Continuous peripheral nerve blocks represent an adjunctive, effective, and safe technique for postoperative pain control after hip arthroplasty, allowing for lower opioid consumption, lower side effect profile e.g. nausea and vomiting, improved and earlier rehabilitation and high patient satisfaction6. Many anaesthetists now perform lower limb blocks in combination with general anaesthesia or spinal anaesthesia to provide prolonged postoperative pain relief. The most commonly performed block is the 3:1 femoral block which is assumed to block the femoral nerve, obturator nerve and the lateral cutaneous nerve of the thigh.

The psoas block is another common block used for hip surgery. In addition, these blocks can provide a useful adjunct to GA where central neural blockade is either technically difficult or contraindicated. They are particularly useful when a widespread sympathectomy is undesirable, as in low cardiac output states or aortic stenosis.

Complications for using continuous peripheral catheters include: bruising, haematoma, local anaesthetic toxicity, peripheral nerve damage, catheter kinking and migration7.

Local infiltration analgesia (LIA)
The multimodal infiltration technique is simple, apparently safe, cheap, and requires minimal technical skill. In essence, the technique includes an intraoperative infiltration of the whole surgical area with a mixture solution of ropivacaine, ketorolac (NSAID) and adrenaline. A catheter can also be left within the joint cavity to the skin, allowing repeated infusion in the evening if needed. The anaesthetic technique varies depending on patient safety and concerns regarding the potential of wound site infection.

Andersen et al. in 2007(a) performed a randomised study on this local infiltration analgesia (LIA) technique in hip arthroplasty, comparing LIA to continuous epidural infusion in 80 patients. In this study, 200mg ropivacaine, 30mg ketorolac and 0.5mg adrenaline was used. It was found that opioid consumption was significantly reduced. Pain relief at rest was good, but similar in the two groups in the immediate postoperative period, and significantly reduced in the LIA group from the second day when active treatment had ended. Furthermore, side effects were significantly lower due to avoidance of epidural analgesia, walking ability was better and the hospital stay was reduced by two days in the LIA group8.

Kerr and Kohan in 2008, in an open, nonrandomised case series, used LIA to manage postoperative pain in all 325 patients from Jan 1, 2005 to Dec 31,2006 for elective hip resurfacing, primary total hip replacement or primary total knee replacement arthroplasty9. They recorded pain scores, mobilisation times, and morphine usage for the entire group.

The results showed that pain control was generally satisfactory (numerical rating scale pain score range 0-3). No morphine was required for postoperative pain control in two-thirds of the patients. Most patients were able to walk with assistance between 5 and 6 h after surgery and independent mobility was achieved 13-22 h after surgery. Orthostatic hypotension, nausea, and vomiting were occasionally associated with standing for the first time, but other side effects were unremarkable. 230 (71%) of the 325 patients were discharged directly home after a single overnight stay in hospital9.

In a randomised, double-blinded, placebo-controlled study from Odense University Hospital, forty consecutive patients undergoing total hip replacement were randomised into two groups; either to an intervention group receiving local infiltration analgesia, or to a control group receiving pure saline solutions10. In this study, 300mg ropivacaine, 30mg ketorolac and 0.5mg adrenaline was used. The results revealed that the patients treated with LIA experienced less pain up to two weeks postoperatively. They needed less additional analgesics and were more satisfied. Interestingly, this treatment regimen also resulted in less joint stiffness and better function one week postoperatively10.

In the authors' medical institute, a variety of volumes and concentrations were used by various surgeons leading to an audit of practices. Various ropivacaine combinations included doses of 120 mgs (60mls 2mg/ml), 190 mg (20mls 7.5mg/ml+20mls 2mg/ml, 40 mls) and 285 mg (30mls 7.5mg/ml+30mls 2mg/ml, 60 mls), depending on the patient's weight. This is based on the acceptable doses of ropivacaine as 4mg/kg, assuming this is below the toxicity level. Neither adrenaline nor NSAIDs were used due to the lack of adequately powered studies and concerns of side-effects associated with healing and renal function. 30 patients were selected from each surgeon and the notes reviewed.

The results of the audit were that there was a significant reduction in total post-operative morphine consumption in the groups that by having either 285mgs or 190 mgs of ropivacaine, the amount of post-operative morphine consumption was significantly reduced, as compared to patients who had not received a LIA. This led to a hospital policy of the following: patients under 70kg to have 190mg ropivacaine and patients over 70kg to have 285mg ropivacaine.

The technique of LIA at ROH ensures that all the surgical areas are covered. Depending on the surgeon, this may involve:

-half of the LIA into the joint capsule and half into the tensor fascia lata, or -third into capsule, tensor fascia lata and subcutaneous tissue.

This preliminary trust wide audit highlighted the analgesic benefits of the use of LIA. The authors are now currently seeking ethical approval for a full scientific study into the use of plain ropivacaine LIA at our institution.

In assessing the validity of the components, ropivacaine is a long-acting local anaesthetic. The benefit of using Ketorolac is pain relief and inhibition of the inflammatory process. Ketorolac is approved for intra-articular use, with a well-documented positive effect on postoperative pain11. The reason for adding adrenaline is to act as a vasoconstrictor and slow down the uptake of the drugs and thereby reduce potentially toxic blood concentrations and to prolong the effects of the drugs in the wound. In addition, NSAIDs have a positive effect on soft-tissue healing and prevention of heterotopic ossification12. Common questions are:

1) High plasma concentrations of ropivacaine are neurotoxic and cardiotoxic. The toxicity threshold and safe amount of injected ropivacaine has been well defined13,14. The dosages of ropivacaine injections selected appeared to be sufficient and distinctly below the safe dosage limit used in well-documented studies. Infiltration with 400 mg ropivacaine in relation to total knee arthroplasty15,16, showed plasma concentrations far below the toxic threshold (0.6