Pain: management

Introduction

• The growth in scientific knowledge of the pathophysiology of pain in small animals allows us to select a wide variety of pharmaceutical agents combined with other techniques for pain management. Pain management can be divided into 2 very broad categories: acute and chronic pain control. This article primarily discusses pain management drugs and includes recent information and developments.
• The goal of pain management for trauma patients is to immediately alleviate the intensity of pain by administering appropriate primary analgesics. This usually involves opioids in combination with sedatives.
• The goal of acute pain management for patients undergoing elective surgery is to prevent pain by using analgesics pre-emptively, intraoperatively, and postoperatively according to need . This usually involves one, or a combination of the following: opioids ; local anesthetics ; constant rate of infusion with an NMDA (N-methyl-D-aspartate) receptor antagonist, opioids, and local anesthetics; and NSAIDs (non-steroidal anti-inflammatory drugs) .
• The goal of managing non-malignant chronic pain is not only to alleviate pain daily but also to improve the function of the patient over time and improve quality of life. This may involve the use of opioids, NSAIDs, tramadol, and drugs used to treat neuropathetic pain, such as amantidine, gabapentin , and NMDA receptor antagonists.
• The goal of managing malignant pain is to provide comfort and may involve using the whole spectrum of analgesics and sedative agents over the course of the disease.
• Using various analgesic agents at different times or in different combinations may drastically improve the quality of pain management. Strategies such as pre-emptive analgesia and balanced analgesia (or multimodal analgesia) are frequently used.
• Pre-emptive analgesia operates on the principle of administering analgesic drugs before the painful stimulation occurs, thereby preventing central nervous system sensitization (or wind up), which amplifies the sensation of pain. The use of the balanced analgesic technique allows practitioners to use the various mechanisms of action of the different analgesic agents to provide pain control, minimizing the side-effects of a single large-dose of any one analgesic agent. The use of various low-dose analgesic agents may also provide synergistic analgesic effects, benefiting the patient more than a single analgesic agent.

Sources

Publications

Refereed papers

• Recent references from PubMed.
• Goyenechea Jaramillo L A, Murrell J C, Hellebrekers, L J (2006) Investigation of the interaction between buprenorphine and sufentanil during anaesthesia for ovariectomy in dogs. Vet Anaesth Analg 33 (6), 399-407 PubMed.
• Valverde A, Cantwell S, Hernandez J et al(2004) Effects of acepromazine on the incidence of vomiting associated with opioid administration in dogs. Vet Anaesth Analg 31 (1), 40-45 PubMed.
• Muir W W 3rd, Wiese A J, March P A (2003) Effects of morphine, lidocaine, ketamine, and morphine-lidocaine-ketamine drug combination on minimum alveolar concentration in dogs anesthetized with isoflurane. Am J Vet Res 64 (9), 1155-1160 PubMed.
• Wagner A E, Walton J A, Hellyer P W et al(2002) Use of low doses of ketamine administered by constant rate infusion as an adjunct for postoperative analgesia in dogs. J Am Vet Med Assoc 221 (1), 72-75 PubMed.
• Lucas A N, Firth A M, Anderson G A et al(2001) Comparison of the effects of morphine administered by constant-rate intravenous infusion or intermittent intramuscular injection in dogs. J Am Vet Med Assoc 218 (6), 884-991 PubMed.
• Muir W W III, Woolf C J (2001) Mechanisms of pain and their therapeutic implications. J Am Vet Med Assoc 219 , 1346-1356 PubMed.
• Ko J C H, Lange D G, Mandsager R E et al(2000) Effects of butorphanol and carprofen on the minimal alveolar concentration of isoflurane in dogs. J Am Vet Med Assoc 217 (7), 1025-1028 PubMed.
• MacPherson R D (2000) The pharmacological basis of contemporary pain management. Pharmacol Ther 88 (2), 163-185 PubMed.
• Kehlet H, Dahle J B (1993) The value of multimodal or balanced analgesia in postoperative pain treatment. Anesth Analg 77 , 1048-1056 PubMed.
• Beaver W T (1984) Combination analgesics. Am J Med 77 , 8-53 PubMed.