Pain management for oral surgery in dogs and cats

Pain management for oral surgery in dogs and cats

A review of continuous-rate infusion, chronic and cancer pain
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Jan 01, 2008

Oral surgery in canine and feline patients often requires extended periods of anesthesia necessitating optimal anesthetic management. A safe and effective mode of pain management for the oral-surgery patient is intravenous continuous-rate infusion (CRI), using a multimodal approach to affect various levels of the nociceptive pathway.


Table 1: IV Fluid Bag Based CRI Infusions
The administration of opiates in various veterinary species has been shown to be safe and effective in decreasing MAC. Lidocaine acts to decrease central hypersensitivity in significant pain states and when given with opiates has a sparing effect on those agents. In a recent study, dogs undergoing limb amputation that received ketamine infusions had significantly lower pain scores 12 and 18 hours after surgery and were significantly more active on postoperative day three than dogs that did not. Furthermore the combination of morphine, lidocaine and ketamine delivered as a low-dose CRI provides significant decreases in required isoflurane MAC in dogs. No adverse hemodynamic effects were experienced. Medetomidine has been used as a CRI in veterinary patients; however, a recent study warned of adverse hemodynamic effects of this drug when used in this manner, noting that further investigation needs to be done before its use is advocated.


Table 2: Sample CRI protocol and nerve-block calculation for a feline patient undergoing four quadrant extractions
Detailed spreadsheets are available for calculation of rates, volumes and loading doses for CRI in dogs and cats using morphine, lidocaine and ketamine (Tables 1 and 2). Weight/volume calculations for commonly used analgesics are particularly convenient resources and can be found at the Veterinary Anesthesia Support Group Web site ( http://www.vasg.org/.)

Chronic pain

The pathophysiology of chronic pain involves the complex mechanisms of peripheral and central sensitization. Significant pain states arise frequently in oral disease because the pathology is hidden from casual owner observation. Many patients suffering chronic pain do not become anorectic. Feline lymphocytic plasmacytic gingivostomatitis (LPGS), canine stomatitis, chronic ulcerative paradental stomatitis (CUPS), untreated oral trauma and some types of oral cancer are common examples of chronic oral pain.

In the presence of persistent central and peripheral sensitization, traditional perioperative and postoperative pain management fall considerably short of the desired outcome. In order to effectively manage postoperative pain in chronic conditions, more aggressive means must be employed. A novel approach to managing chronic pain states termed the "analgesic reverse-pyramid" protocol shows considerable promise in effectively managing these patients. With this approach, immediate intense multimodal analgesic management is employed, using agents targeted to different portions of the nociceptive pathway. The chronic pain is targeted aggressively from the initiation of pain management and then tapered as desired based upon patient observation. This is in contrast to the traditional approach of adding analgesics from different classes if the initial response was less than desired.

Feline patients with LPGS particularly suffer pain. Using multimodal, pre-emptive and analgesic reverse-pyramid concepts, the author initiates pain management for these patients 6-24 hours prior to initiation of the surgical stimulus for caudal mouth extractions. Meloxicam is instituted to minimize the inflammatory peripheral sensitization experienced in these patients. Loading doses and a subsequent CRI of ketamine and morphine are commonly employed. Hydromorphone and fentanyl are alternative opioids that are particularly effective as well.

CRI is continued in the intraoperative and postoperative period. Postoperative analgesics consisting of buprenorphine (transmucosal or transdermal) or a fentanyl transdermal patch and meloxicam are continued for up to four days. If a fentanyl patch is used, it is placed such that the onset of therapeutic serum levels coincides with the anticipated culmination of the procedure. Regional nerve blocks are always employed preoperatively following achievement of a surgical plane of anesthesia. Table 1 provides an example of CRI protocol and regional nerve-block calculations for a feline patient undergoing four quadrant extractions.