2.3. Postoperative pain management

Postoperative pain is one of the main barriers to increasing the range of ambulatory procedures. Persistent pain has been shown to lead to postoperative nausea and vomiting (Anderson et al. 1996), delayed discharge (Chung 1995c), contact with medical facility after discharge (Fortier et al. 1996) and unanticipated admissions (Gold et al. 1989, Fortier et al 1996). Undertreatment of pain is common in outpatients (Beauregard et al. 1998). Beauregard et al. reported that 40% of discharged outpatients suffered from moderate to severe pain during the first 24 hours. Chung and colleagues (1997) found that orthopedic procedures and the duration of anaesthesia were predictors of postoperative pain.

Opioids are the mainstay of postoperative pain therapy in ambulatory surgery (Tong & Chung 1999); however, opioid analgesia has to be balanced against the potential side effects, mainly nausea and vomiting (Anderson et al. 1996). Therefore, outpatient studies on opioids have focused on finding the particular opioid and the timing of administration that would lead to a lower incidence of postoperative nausea and vomiting (Claxton et al. 1997). To avoid postoperative nausea and vomiting, the use of postoperative opioids should be minimized (Tong & Chung 1999). In painful outpatient procedures, opioids may be needed to treat patients with severe pain. In this case, the use of lower doses (0.1 mg/kg) of intravenous morphine in the PACU did not cause more nausea and vomiting during the patients’ hospital stay compared with fentanyl (Claxton et al. 1997).

Niemi et al. (1994) showed that postoperative analgesia in patients undergoing knee arthroscopy under local anaesthesia with 1% lidocaine plus adrenaline, but not under hyperbaric 0.5% bupivacaine spinal anaesthesia, could be improved with a single intra-articular injection of 1 mg of morphine. Allen et al. (1993) showed that morphine, at 1 mg intra-articularly, in 30 ml of 0.25% bupivacaine, with 1:200,000 epinephrine may provide superior postoperative analgesia compared to bupivacaine or morphine alone after ambulatory knee surgery under general anaesthesia. Van Ness et al. (1995) concluded that intra-articular morphine after general anaesthesia reduces postoperative pain and analgesic requirements more effectively and at a lower average patient cost than bupivacaine.

There are also opposite findings showing no benefit from intra-articular administration of morphine or bupivacaine compared to isotonic saline after elective knee arthroscopy (McSwiney et al. 1993, Björnsson et al. 1994, Laurent et al. 1994, Ruwe et al. 1995, Aasbo et al. 1996). Morphine is a poorly lipid-soluble opioid and it can be absorbed from any anatomical tissue, which is why the results can be attributed to either local or systemic effects (Debruyne et al. 1985). An intra-articular alpha(2) agonist clonidine has been shown to enhance patient analgesia after arthroscopic knee surgery, and the combination of clonidine with morphine resulted in decreased postoperative pain and analgesic use as well as increased analgesic duration compared with either drug alone (Joshi et al. 2000). Intra-articular sufentanil (5–10 µg) administration has been shown to improve, in a double-blinded fashion, postoperative management after day-case diagnostic arthroscopic knee procedures (Vranken et al. 2001).

The efficacy of preoperative NSAID administration for postoperative pain has been extensively investigated in randomized, controlled trials. Most comparisons of NSAIDs with placebo demonstrated a decrease in postoperative pain scores or analgesic requirements (Dueholm et al. 1989, Comfort et al. 1992, Ben-David et al. 1996b, Jakobsson et al. 1996, Murrell et al. 1996). NSAIDs also gave rise to a lower side effect profile during recovery (Rosenblum et al. 1991, Wong et al. 1993, Forse et al. 1996, Sukhani et al. 1996). Most outpatient studies comparing NSAIDs with opioids in perioperative use have demonstrated that opioids provide comparable or better pain relief in the early recovery period (McLoughlin et al. 1990, Wong et al. 1993, Twersky et al. 1995), whereas NSAIDs provide better pain relief in the late recovery period (McLoughlin et al.1990, Rosenblum et al. 1991, Twersky et al. 1995). Combination of opioids with NSAIDs involves a rapid effect of opioids followed by a longer analgesic duration of NSAIDs (McLoughlin et al. 1990, Rosenblum et al. 1991, Twersky et al. 1995, Sukhani et al. 1996).

The efficacy of NSAIDs for postoperative pain relief depends on the timing and route of administration (Tong & Chung 1999). Because of their peripheral mechanisms of action, NSAIDs have longer onsets than opioids, and parenteral NSAIDs are therefore usually administered at induction or intraoperatively, allowing adequate time for them to exert their peak effect (Tong & Chung 1999). Norris et al. (2001) found no difference in pain relief regardless of whether the NSAID (diclofenac) was given preoperatively or postoperatively in patients undergoing unilateral day-case knee arthroscopy. There is no scientific documentation of the superiority of any individual NSAID for perioperative use (Morrow et al. 1993). The choice of preparation, therefore, depends on availability, the desired route of administration, the duration of effect and cost (Kehlet & Mater 1992).

Several studies have investigated the use of low-concentration, low-dose spinal anaesthetics and the addition of an intrathecal opioid to take advantage of prolonged postoperative analgesia, while avoiding postoperative motor block, urinary retention, and prolonged recovery time (Orr et al. 1987, Urmey et al. 1995, Chilvers et al. 1997).