Pain issues and management in veterinary dentistry and oral surgery: Part 3 (Proceedings)

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Pain issues and management in veterinary dentistry and oral surgery: Part 3 (Proceedings)

CRI, chronic, and cancer Pain
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Aug 01, 2008

Continuous Rate Infusions (CRI)

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 utilizing a multimodal approach to affect various levels of the nociceptive pathway.

The administration of opiates in various veterinary species has been studied and has been shown to be both safe and effective in decreasing MAC.1,2,3 Lidocainea acts to decrease central hypersensitivity in significant pain states and when given with opiates has a sparing effect on those agents.4 In a recent study dogs undergoing limb amputation that received ketamineb infusions had significantly lower pain scores 12 and 18 hours after surgery and were significantly more active on postoperative day 3 than dogs that did not.5 Furthermore the combination of morphinec , lidocainea and ketamineb delivered as a low dose CRI provides significant decreases in required isoflurane MAC in dogs.6 No adverse hemodynamic effects were experienced. Medetomidined 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.7


IV FLUID BAG BASED CRI INFUSIONS
Detailed spreadsheets are available for calculation of rates, volumes and loading doses for CRI in dogs and cats utilizing morphinec , lidocainea and ketamineb (Table 1) (1) (2). Weight/volume calculations for commonly used analgesics are particularly convenient resources and can be found at the Veterinary Anesthesia Support Group website.(2)

Drug CRI Dose Range

MORPHINE - 0.12 to 0.36 mg/kg/hr (2 to 6 ug/kg/min).

LIDOCAINE - 0.6 to 1.5 mg/kg/hr (10 to 25 ug/kg/minute).

Dogs can be given a max. dose of 3.0 mg/kg/hr (50 mcg/kg/min)

Cats should be limited to a max. dose of 1.5 mg/kg/hr (25 mcg/kg/min)

KETAMINE - 0.12 to 1.2 mg/kg/hr (2 to 20 ug/kg/minute).

Loading Doses

MORPHINE - 0.5 mg/kg IM (or very slowly IV)

At 0.5 mg/kg this patients needs a loading dose of: 0.17 ml

LIDOCAINE - 0.5 to 1 mg/kg IV

At 0.25 mg/kg this patients needs a loading dose of: 0.06 ml

At 1.0 mg/kg this patients needs a loading dose of: 0.25 ml

CATS - Limit cats to 0.25 mg/kg loading dose

DOGS - 1.0 mg/kg is the normal loading dose

KETAMINE - 0.25 to 0.50 mg/kg IV bolus

At 0.25 mg/kg this patients needs a loading dose of: 0.01 ml

Drug Concentrations

MORPHINE - 15 mg/ml

LIDOCAINE - 20 mg/ml

KETAMINE - 100 mg/ml