Postoperative Pain Management

Management of pain, a primary concern after surgery, involves pharmacologic measures (eg, systemic analgesia) and nonpharmacologic measures. Regional analgesia may be used postoperatively. A major goal of pain management is patient comfort; an equally important goal is decreased morbidity and mortality. In the elderly, assessment of pain may be difficult because of cognitive impairment due to acute illness or dementia.

Postoperative pain in the elderly is best managed by a dedicated acute pain service consisting of physicians (generally anesthesiologists) and nurses who specialize in various modalities of postoperative pain control. Hemodynamic parameters and mental status must be closely monitored, and the altered effects of drugs in the elderly must be thoroughly understood. A collaborative approach among surgical, nursing, and acute pain service staff members can result in safe, effective pain management for even the most frail elderly patient.

Pain management in the elderly has been addressed in clinical practice guidelines by the Agency for Health Care Policy and Research and by the American Geriatrics Society and in reports by the American Society of Anesthesiologists and International Association for the Study of Pain. Adequate pain management may improve cardiovascular and pulmonary function and, by preventing the stress response to postoperative pain, may lower the incidence of postoperative myocardial events. Decreased ventilatory function after thoracic or abdominal surgery is caused mainly by surgical trauma and by splinting due to postoperative pain. Pain management cannot restore ventilatory function but can help prevent splinting by enabling patients to breathe deeply and cough, thus improving mucus removal and avoiding atelectasis. Prevention of atelectasis reduces the postoperative risk of pneumonia and hypoxia.

Generally, adequate postoperative pain management helps patients walk sooner and improves functional status, hastening their return to the community. Pain management also enables patients to be discharged earlier, thus reducing medical care costs.

Regional analgesia: Regional anesthetic techniques range in complexity from instillation of a local anesthetic into the surgical incision to specific nerve blocks to continuous epidural infusion of a local anesthetic, an opioid, or both. The technique is chosen based on the surgical site and on the technique's relative complexity and potential advantages or disadvantages.

The primary advantage of using regional anesthetic techniques is that intravenous opioid use can be reduced or eliminated. A regional anesthetic block performed before surgery provides longer pain relief than is expected from a local anesthetic. When the anesthesia wears off and pain recurs, the pain is less intense, and lower opioid doses can be used. The mechanism for this effect involves modulation of impulses sent to the brain; this action appears to occur at the spinal cord level. Disadvantages of regional techniques include the hemodynamic effects of local anesthetics administered epidurally and the potential for intravascular injection, infection, bleeding, and nerve damage.

For pain after limb surgery, a single-dose nerve block or continuous opioid infusion is often used. For hand or elbow surgery, the axillary approach is used to block the brachial plexus because of its relative ease and lower incidence of complications compared with other approaches. If prolonged pain relief is needed, a catheter is inserted preoperatively and an infusion of a local anesthetic is begun postoperatively. Often, bupivacaine 0.125% provides complete pain relief. The infusion is usually started at 8 to 10 mL/hour and titrated to desired effectiveness.

For pain after knee surgery, a continuous infusion of a local anesthetic solution through a femoral sheath catheter can be effective, even though the sciatic nerve is not blocked. If necessary, femoral catheter infusion may be supplemented by small amounts of intravenous or intramuscular opioid or ketorolac.

For pain after hip, abdominal, or thoracic surgery, a continuous epidural infusion is often selected, especially for medically high-risk patients. Infusion of bupivacaine 0.0625% to 0.125% with fentanyl 2 to 4 µg/mL at 8 to 10 mL/hour usually relieves pain, but upward titration may be needed. Ropivacaine, a relatively new local anesthetic, has less cardiovascular toxicity and is used in the same concentrations as bupivacaine.

Insertion of an epidural catheter at the site of perceived discomfort can reduce the amount of local anesthetic and opioid needed, minimizing the possibility of toxicity. For hip surgery, the catheter is inserted in the lumbar region; for abdominal surgery, the lower thoracic region; and for thoracotomy, the midthoracic region. Fentanyl is lipophilic and does not spread widely in the epidural space, so the catheter must be placed near the nerve source of the pain. Epidural morphine spreads more readily; however, the rostral spread of morphine may cause late respiratory depression.

The most common complication of continuous epidural infusion is the inadvertent removal of the catheter during routine nursing care. Meticulous taping of the catheter and nursing education can help solve this problem. Urinary retention due to the local anesthetic and the opioid occurs more commonly among elderly men than among women or younger men. The catheter may migrate to subcutaneous tissues, terminating pain relief. Rarely, the catheter migrates to the spinal space, sometimes resulting in high levels of anesthetic that may be life threatening.

In the elderly, epidural infusion must be titrated precisely, and intravascular volume must be maintained by closely monitoring fluid status and promptly replacing fluids if needed. In an elderly patient with a sympathetic block, blood loss of 300 to 500 mL from a hip wound drain can result in dangerously low blood pressure unless fluids are promptly replaced.