Drug Combinations

Chapter 2 Drug Combinations



HORSES



IV Sedation



Uses



▪ Examinations

▪ Standing procedures

▪ Premedication before inhalation anesthesia



Xylazine 0.5 mg/kg IV or Detomidine 0.02 mg/kg IV


For greater effect:


+ Butorphanol 0.03 mg/kg IV


Acepromazine 0.05 mg/kg IV


For greater effect:


+ Butorphanol 0.03 mg/kg IV or


Detomidine 0.01-0.02 mg/kg IV


Xylazine 0.66 mg/kg IV


Morphine 0.66 mg/kg IV very slowly


See important note below



Features


Xylazine or detomidine ± butorphanol:


▪ Shorter duration with xylazine than detomidine

Acepromazine ± butorphanol or detomidine:


▪ Acepromazine has relatively long onset, up to 10 minutes even when used IV

▪ Ideal for sedation of mares during anesthesia of foal (especially with detomidine)

▪ Drug metabolites may pass into milk

Xylazine + morphine:


▪ Suitable for use only during long procedures (approximately 3 hours; e.g., perineal laceration repair, standing abdominal procedures)

▪ Must wait for heavy sedation before morphine is used

▪ Inject morphine slowly, and watch carefully for signs of histamine release (cutaneous wheals)

▪ Sweating occurs on head and neck

▪ Horse has rigid sawhorse stance with head and neck leaning forward; take care that trachea is not occluded by ropes, etc.

▪ Duration of effect of xylazine is much shorter than that of morphine; horse becomes restless as xylazine wears off; repeated doses are required approximately every 20 to 30 minutes initially, then at longer intervals with successive doses; use as needed

▪ Personnel must monitor horse closely for at least 3 to 4 hours

▪ Morphine can be reversed with naloxone, if necessary; reverse slowly


IV Anesthesia



▪ Short procedures (e.g., 20 minutes)

▪ Can prolong to approximately 1 hour by using “triple drip”

▪ Can use the following combinations before inhalant anesthesia


image


Features



▪ Wait for full sedation before continuing with induction

▪ Horses may react to sudden stimuli even if apparently fully sedated after xylazine administration

▪ Do not prolong by using Pentothal, because of slow and rough recovery

▪ Ensure good padding and eye protection, especially for procedures lasting longer than approximately 20 minutes


“Triple Drip”: Guaifenesin + Xylazine + Ketamine



image


Advantages



▪ Usually associated with smooth recovery

▪ Depth of anesthesia is fairly easily manipulated; use palpebral reflex as a guide

▪ Causes good muscle relaxation


Disadvantages



▪ Respiratory depression and bradycardia occur with excess; monitor carefully

▪ Must record ketamine use in controlled-drug log


RUMINANTS



IV or IM Sedation



Uses



▪ Examinations

▪ Standing procedures with local anesthesia blocks (e.g., dehorning)


Cattle, Sheep, and Goats




Xylazine


0.01-0.05 mg/kg IM*


Goats are most sensitive to xylazine


Xylazine


0.02 mg/kg IM + Butorphanol


0.05-0.07 mg/kg IM


Butorphanol IV


1.1 mg/kg



* At the higher end of this range, animals may become recumbent.



Goats




Diazepam 0.1-0.5 mg/kg IM or IV


Midazolam 0.05-0.25 mg/kg IM or IV


Butorphanol 0.01 mg/kg IM + Acepromazine 0.05 mg/kg IM + Glycopyrrolate 0.01 mg/kg IM



Features



▪ Do not use detomidine in ruminants because of its prolonged action

▪ Do not use xylazine in goats with blocked urinary tract; increased urine volume may cause rupture of urinary bladder

▪ Effects of drugs depend on temperament of animal

▪ Acepromazine has long duration and is best avoided in ruminants


IM Premedication, Then IV Anesthesia



Use



▪ For minor procedures (e.g., wound repair, radiographs)


Calves, Sheep, and Goats




Premedication



image


Induction



image


Advantages



▪ Associated with smooth induction and recovery

▪ Depth of anesthesia is fairly easily manipulated

▪ Causes good muscle relaxation

▪ Suitable for use in goats with blocked urethra


Disadvantages



▪ Animals must be intubated to protect airway (regurgitation is always a risk with ruminants)

▪ Not suitable for use during major surgery or prolonged procedures

▪ Must record use of butorphanol, ketamine, and diazepam in controlled-drug log


Precautions



▪ Ensure adequate fasting

▪ If possible, use padding under neck and have animal’s head tilted downward so that any regurgitated material can drain from the mouth

▪ Move anesthetized animal as smoothly as possible

▪ Keep animal in sternal recumbency for recovery


IV Anesthesia: Guaifenesin + Xylazine + Ketamine




Cattle and Sheep



image


Advantages



▪ Associated with smooth induction and recovery

▪ Depth of anesthesia is fairly easily manipulated

▪ Causes good muscle relaxation


Disadvantages



▪ Must use IV route

▪ Must intubate animal to protect airway (regurgitation is always a risk with ruminants)

▪ Large volume required

▪ Not suitable for use during major surgery or prolonged procedures; can be used for induction before maintaining anesthesia with inhalant agents designed for such situations

▪ Must record use of ketamine in controlled-drug log


Precautions



▪ Ensure adequate fasting

▪ If possible, use padding under neck and have animal’s head tilted downward so that any regurgitated material can drain from the mouth

▪ Move anesthetized animal as smoothly as possible

▪ Keep animal in sternal recumbency for recovery


PIGS



IM Anesthesia: Xylazine + Ketamine + Oxymorphone



image


Advantages



▪ Easy to administer; best in muscles behind ear (thinner skin; little fat; pig cannot bite easily; minimal damage to muscle)

▪ Associated with smooth induction and recovery

▪ Causes good analgesia

▪ Causes good muscle relaxation (sufficient for easy intubation)

▪ Duration approximately 45 minutes to 1 hour

▪ Can hasten recovery with naloxone and yohimbine


Disadvantages



▪ Relatively costly (oxymorphone)

▪ Must record use of ketamine in controlled-drug log


Precautions



▪ Intubate pigs to protect airway

▪ Fast pigs sufficiently to prevent them from vomiting

▪ Always monitor pigs carefully during recovery to ensure adequate respiratory function


IM Anesthesia: Xylazine + Ketamine + Telazol



image


Advantages



▪ Easy to administer; best in muscles behind ear (thinner skin; little fat; pig cannot bite easily; minimal damage to muscle)

▪ Associated with smooth induction and recovery

▪ Causes good analgesia

▪ Causes good muscle relaxation (sufficient for easy intubation)

▪ This combination has a reduced concentration of zolazepam as compared with telazol; less hindlimb weakness in recovery


Disadvantages



▪ Costly (telazol)

▪ Recovery may be prolonged in older animals

▪ Must record use of telazol and ketamine in controlled-drug log


IM Premedication, Then IV Anesthesia



Use



▪ For minor procedures (e.g., trimming feet, radiographs)

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Oct 14, 2016 | Posted by in SUGERY, ORTHOPEDICS & ANESTHESIA | Comments Off on Drug Combinations

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