Patient-Controlled Analgesia 
The International Association for the study of pain defines pain as "an unpleasant sensory and emotional experience associated with actual and potential tissue damage or described in terms of such damage, or both (Cole, 2002). The degree of post operative pain depends on the site of the surgery. Surgery on the thorax and upper abdominal regions are usually more painful and complicated than the lower abdominal regions. Pain causes an increase in the heart rate, cardiac work and oxygen consumption. Chronic pain reduces physical activity and leads to venous stasis and an increased risk of deep vein thrombosis and consequent pulmonary embolism, urinary tract motility that may lead, in turn, to postoperative ileus, nausea, vomiting and urinary retention. These problems are unpleasant for the patient and may prolong hospital stay. The standard method of treating postoperative pain is the use of intramuscular opioid (usually morphine). Recently, patient-controlled analgesia (PCA) has often been shown to be better than the intermittent delivery of intramuscular opioids. Patient-controlled analgesia is a process where the patients can determine the pain relief process. With PCA, patients can self-administer small analgesic doses into a running intravenous infusion, intramuscularly, subcutaneously or even into the spinal space (Lehmann, 1999).

Published Evidence
A recent research to compare the outcomes during conventional analgesia in the form of intramuscular dosing and patient-controlled analgesia (PCA) in postoperative patients by analyzing data of 15 randomized control trials with seven hundred eighty-seven adult patients aged between 16 to 65 undergoing various operative procedures has revealed greater analgesic efficacy when PCA is used, with a mean additional benefit of 5.6 on a scale of 0 to 100 and a 42% difference in the proportion of patients expressing satisfaction over PCA taking us to the conclusion that patient preference strongly favours PCA over conventional analgesia with better pain relief than those using conventional analgesia, without an increase in side effects (Ballantyne et.al, 1993). Study results have proved that patient-controlled analgesia (PCA) with intravenous morphine and patient-controlled epidural analgesia (PCEA), using an opioid either alone or in combination with a local anesthetic, is effective in the management of pain after a major surgery. A randomized study done to compare the effectiveness on postoperative pain and safety of PCEA and PCA after major abdominal surgery in seventy patients older than 70 years of age undergoing a major abdominal surgery assigned randomly to receive either combined epidural analgesia and general anesthesia followed by postoperative PCEA, using a mixture of 0.125% bupivacaine and sufentanil (PCEA group), or general anesthesia followed by PCA with intravenous morphine (PCA group) has shown that patient-controlled analgesia, regardless of the route (epidural or parenteral), is effective after a major abdominal surgery in the elderly patients (Mann et.al, 2000). The study has also proved that patient-controlled analgesia (PCA) allows patients to self-administer small doses of narcotic, allowing better dose titration, enhanced responsiveness to variability in narcotic requirements, and reduction in serum narcotic level fluctuation (Egbert et.al, 1990).

A prospective controlled trial carried out with 83 higher-risk elderly men after  a major elective surgery to assess PCA containing morphine sulfate with intramuscular morphine injections has shown that analgesia significantly improves by PCA without an increase in sedation and patient-controlled analgesia can be adapted by patients with no major problems referable to its use (Egbert et.al, 1990). The influence of three analgesic techniques on postoperative knee rehabilitation after total knee arthroplasty (TKA) has been assessed in a research study with forty-five patients randomly divided into three groups as A, B and C. Patients in Groups B and C in the study who were given continuous 3-in-1 block and epidural analgesia have been shown to have reported significantly lower pain scores than those in Group A who were given intravenous postoperative analgesia with morphine. This study based on the pain scores, supplemental analgesia, side effects, degree of maximal knee flexion, day of first walk, and duration of hospital stay has shown that, after TKA, continuous 3- in-1 block and epidural analgesia provide better pain relief and faster knee rehabilitation than intravenous PCA with morphine (Singelyn,1992).

A double-blinded, randomized controlled trial in which seventy-one patients were allocated to receive morphine 1 mg/mL or morphine 1 mg/mL plus ketamine 1 mg/mL delivered via PCA after surgery to test if the addition of ketamine to morphine for patient-controlled analgesia (PCA) results in improved analgesic efficacy and lower pain scores compared with morphine PCA alone after a major abdominal surgery has shown that small-dose ketamine combined with PCA morphine provides no benefit to patients undergoing major abdominal surgery highlighting the efficiency of morphine in PCA and the increased side effects of Ketamine (Reeves et.al, 2001). A prospective, double-blind, cross-over study comparing epidural and intravenous (IV) administration of fentanyl in sixteen patients for the first twelve hours after lower abdominal or lower extremity surgery to test the hypothesis that Fentanyl, unlike morphine, is highly lipophilic and rapidly diffuses out of the epidural space causing respiratory depression and much of fentanyl's analgesic effect is mediated by systemic rather than spinal receptor binding has shown that the analgesic effects of epidural fentanyl appear largely mediated by systemic absorption. The study has also shown that intravenous fentanyl achieves a similar degree of analgesia without the need for epidural catheterization (Glass et.al, 1992). A recent study to investigate if the nasal route for fentanyl administration in patient-controlled analgesia (PCA) provides as effective postoperative analgesia as intravenous PCA has shown that intranasal PCA with fentanyl was an effective alternative to intravenous PCA in postoperative patients (Toussaint et.al,2000).

A randomized, prospective trial of patient-controlled analgesia (PCA) performed in eighty two children and adolescents after major orthopaedic surgery to compare intramuscularly administered morphine, PCA morphine and PCA morphine with a low-dose continuous morphine infusion (PCA-plus) has elucidated that patients receiving PCA and PCA-plus had lower pain scores and greater satisfaction than patients receiving intramuscularly administered morphine. The study has also shown that PCA and PCA-plus do not increase the incidence of opioid-related complications and patients receiving PCA-plus are less sedated than patients receiving intramuscular therapy. A study to compare patient-controlled analgesia with intramuscular injection of analgesics for the management of pain after an orthopaedic procedure has shown that the patients who control the analgesic use a smaller amount of the analgesic on the first postoperative day and walked farther on the first postoperative day than those who received intramuscular injections (Colwell and Morris, 1995).A recent study to investigate if PCA pump use enhances the incidence of postoperative surgical site infections among patients undergoing open intestinal surgery has shown that there exists no significant association between PCA pump use and in-hospital post operative surgical site infection (Horn et.al,2002). An experimental study to compare the degree of satisfaction with nursing care among patients receiving post-operative pain relief via patient-controlled analgesia (PCA) and those receiving traditional intramuscular injection (IMI) regimes involving 79 adult female patients has shown that PCA saves time and this time saving improves the nursing care quality of the whole ward (Koh and Thomas,1994).

Conclusion
Patient controlled analgesia is an effective method for post operative pain management as evidenced by the research studies. It has been proved more patient centered than other practice methods in pain control with no significant aggravation in side effects. Patient preference strongly favours PCA over conventional analgesia with better pain relief. The patients who use patient controlled analgesia exhibit reduced opioid-related complications. 

References

• A.M. Egbert, L. H. Parks, L. M. Short and M. L. Burnett (1990). Randomized trial of postoperative patient-controlled analgesia vs. intramuscular narcotics in frail elderly men. Achieves of Internal Medicine150 (9).
• Ballantyne JC et al (1993). Postoperative patient-controlled analgesia: meta-analyses of initial randomized control trials. J Clin Anesth. 5(3):182-93.
• Berde, Lehn, Yee, Sethna, Russo (1991).Patient-controlled analgesia in children and adolescents: a randomized, prospective comparison with intramuscular administration of morphine for postoperative analgesia. J-Pediatr 118(3): 460-6.
• F. Michael Ferrante, Francis A. Rosinia, Charles Gordon and sanjay Datta (1994).The Role of Continuous Background Infusions in Patient-Controlled Epidural Analgesia for Labor and Delivery. Anesth Analg 79:80-84.
• FJ Singelyn et.al (1992). Effects of intravenous patient-controlled analgesia with morphine, continuous epidural analgesia, and continuous three-in-one block on postoperative pain and knee rehabilitation after unilateral total knee arthroplasty. Anesthesia & Analgesia, 87; 88-92.
• Mann and Claude (2000). Comparison of Intravenous or Epidural Patient-controlled Analgesia in the Elderly after Major Abdominal Surgery, Anesthesiology 92(2): 433.
• Mark Reeves et.al (2001). Adding Ketamine to Morphine for Patient-Controlled Analgesia after Major Abdominal Surgery: A Double-Blinded, Randomized Controlled Trial. Anesth Analg 93:116-120.
• Max MB, Payne R, Edwards WT, et al (1999). Principles of Analgesic Use in the Treatment of Acute Pain and Cancer Pain. 4th ed. Glenview, IL. American Pain Society.
• ME Abdel-Ghaffar, MA Abdulatif, A al-Ghamdi, H Mowafi and A Anwar (1998). Epidural ketamine reduces post-operative epidural PCA consumption of fentanyl/bupivacaine. Canadian Journal of Anesthesia, Vol 45, 103-109.
• P. S. A. Glass, P. Estok, B. Ginsberg, J. S. Goldberg and R. N. Sladen (1992). Use of Patient-Controlled Analgesia to Compare the Efficacy of Epidural to Intravenous Fentanyl Administration. Anesth Analg 74:345-351.
• Paulin Koh and Veronica J. Thomas (1994). Patient-controlled analgesia (PCA): does time saved by PCA improve patient satisfaction with nursing care? Journal of Advanced Nursing.20 (1); 61-70.
• Simon LS, Lipman AG, Jacox A, et al (2000). Guideline for the Management of Pain in Osteoarthritis, Rheumatoid Arthritis, and Juvenile Chronic Arthritis. APS Clinical Practice Guidelines Series No. 2. Glenview, IL. American Pain Society.
• Susanne Toussaint, Julia Maidl, Rolf Schwagmeier and Hans Walter Striebel (2000). Patient-controlled intranasal analgesia: effective alternative to intravenous PCA for postoperative pain relief. Canadian Journal of Anesthesia 47:299-302.