Anesthetic Procedures and Techniques in Ruminants

Anesthetic Procedures and Techniques in Ruminants

“Moo may represent an idea, but only the cow knows.”

Overview

Local anesthetic techniques and sedation are frequently coupled with physical restraint to provide analgesia and immobility sufficient for surgery in ruminants. General anesthesia, when indicated, is accomplished using techniques that are similar to those used for horses but can be limited by regulations limiting anesthetic and analgesic drug use in ruminants. Potential hazards are regurgitation of rumen contents and bloat (distention of the rumen). Palpebral and ocular reflexes, eyeball position, and pupil size can be used to monitor the depth of anesthesia. Recovery from anesthesia is generally quiet and uneventful and does not routinely require assistance.

General Considerations

I Preparation of ruminants for anesthesia and surgery

A Decrease rumen size and pressure before anesthesia

1. Withhold food for 12 to 18 hours in large ruminants

2. Withhold water for 8 to 12 hours in large ruminants, if possible

3. Withhold food for 12 to 18 hours in sheep and goats; do not withhold water

4. Withhold food for 2 to 4 hours in calves, lambs, and kids; when younger than 1 month of age, they are essentially monogastric and are less prone to regurgitation during anesthesia

B Side effects of withholding food are minimal

1. Mild metabolic alkalosis is observed in healthy animals

2. Bradycardia in adult cattle results from increased vagal tone

C Orotracheal and rumen tubes should be placed when appropriate to avoid bloat and aspiration of rumen contents

II Most surgical techniques in cattle can be performed with local or regional anesthesia (see Chapter 5)

III General anesthesia may be required when local or regional anesthetic techniques are inadequate or if dorsal recumbency is required for surgery; inadequate anesthesia predisposes the animal to stress, which may result in tachycardia and hypertension

Preanesthetic Evaluation

I Preanesthetic evaluation is similar to horses (see Chapter 22)

B Physical examination

C Basic laboratory tests

1. Packed cell volume or hemoglobin

2. Plasma total protein

3. Serum glucose in neonates

4. Other tests as suggested by physical examination

Preanesthetic Medication

I Preanesthetic drugs are used to calm or sedate ruminants or to decrease the dose of more potent intravenous (IV) or inhalant drugs

II Tranquilizers are not approved for use in food animals; drug residues in milk and meat products are problematic. Information about suggested withdrawal times is available from the Food Animal Residue Avoidance & Depletion Program’s Food Animal Residue Avoidance Databank (FARAD) at www.farad.org. (Table 23-1)

TABLE 23-1

Approximate Withdrawal Times for Anesthetic Drugs in Ruminants

Drug	Withdrawal Time		Comments
Drug	Meat	Milk	Comments
Diazepam	7 days	3 days
Midazolam	7 days	3 days
Xylazine	7 days	3 days	Withdrawal times established in Canada
Acepromazine	7 days	2 days	Withdrawal times established in Canada
Butorphanol	>3 days	>3 days	Believed to be rapidly eliminated
Morphine	>3 days	>3 days	Believed to be rapidly eliminated
Oxymorphone	>3 days	>3 days	Believed to be rapidly eliminated
Lidocaine	3 days	2 days	Rapidly eliminated in sheep
Mepivacaine	3 days	2 days	Rapidly eliminated in sheep
Ketamine	2 days	2 days	Short half-life in cattle (<1 hr) and swine (<3 hr)
Guaifenesin	>2 days	>2 days	Rapid elimination in ruminants
Inhalant Anesthetics
Isoflurane	>3 days	>3 days
Sevoflurane	>3 days	>3 days

III Preanesthetic medications include (Table 23-2):

TABLE 23-2

Drug Dosages Used to Sedate and Tranquilize Ruminants (mg/kg)*

Drug	Cattle		Calves		Sheep		Goats
Drug	IV	IM	IV	IM	IV	IM	IV	IM
Acepromazine	0.03-0.05	0.05-0.1	0.03-0.05	0.05-0.1	0.03-0.05	0.05-0.1	0.03-0.05	0.05-0.1
Diazepam	0.2-0.5	0.5-1.0	0.2-0.5	0.5-1.0	0.2-0.5	0.5-1.0	0.2-0.5	0.5-1.0
Alpha-2 Agonists
Xylazine	0.02-0.1	0.02-0.5	0.02-0.1	0.1-0.2	0.02-0.1	0.1-0.3	0.02-0.1	0.1-0.3
Detomidine	0.01-0.02	0.02-0.05	0.01-0.02	0.03-0.05	0.01-0.02	0.02-0.05	0.01-0.02	0.02-0.05
Medetomidine		0.02-0.05		0.02-0.05		0.01-0.03		0.01-0.03
Alpha-2 Antagonists^†
Yohimbine	0.1-0.2		0.1-0.2		0.1-0.5		0.1-0.2
Tolazoline	1.0-2.0		1.0-2.0		1.0-2.0		1.0-2.0
Atipamezole	0.02-0.05		0.02-0.05		0.02-0.05		0.02-0.05

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Tags: Handbook of Veterinary Anesthesia

Sep 6, 2016 | Posted by admin in SUGERY, ORTHOPEDICS & ANESTHESIA | Comments Off

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