Answering your questions: Sedating and anesthetizing patients that have organ system dysfunction - Veterinary Medicine
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Answering your questions: Sedating and anesthetizing patients that have organ system dysfunction
What agents and monitoring devices might be better in these patients? This anesthesiologist tells you how to handle common situations.


VETERINARY MEDICINE


Withhold food eight hours before anesthesia, but be sure to schedule the procedure for early in the morning. Administer half the typical insulin dose in the morning, and obtain a glucose sample before the procedure. If the value is less than 80 mg/dl, start a 5% dextrose intravenous infusion before surgery. If the value is greater than 300 mg/dl, administer regular insulin (0.2 IU/kg subcutaneously). Dextrose administration during the procedure is often not necessary, but a balanced electrolyte solution with 2.5% dextrose (5 to 10 ml/kg/hr intravenously) may be used.

I avoid alpha agonists because of reports of hyperglycemia,11 and mask inductions may cause unnecessary stress. Obtain a glucose sample after the procedure or during a lengthy procedure. Return the patient to small portions of food as soon as is reasonable after the patient has recovered.

Q: Should practitioners incorporate nitrous oxide more often in their anesthetic protocols?

I have found nitrous oxide useful during mask inductions in attempts to avoid an excitement stage and during general anesthesia as one means of providing additional analgesia in patients that are too light. Nitrous oxide provides additional analgesia and can produce more rapid changes in anesthetic depth without the characteristic cardiovascular effects of other inhalant anesthetics (e.g. isoflurane, sevoflurane). Nitrous oxide can also be used for economical reasons.

While people are frequently anesthetized with nitrous oxide, I don't expect the popularity of nitrous oxide to change in veterinary medicine. The advantages of using nitrous oxide are often over shadowed by the desire to avoid complex anesthetic protocols. Administering a hypoxic mixture of gases is much more likely when using nitrous oxide, and I wouldn't recommend its use in practices that do not have technicians dedicated to anesthesia services.

Nitrous oxide should be avoided or used with extreme caution in patients that are hypoxemic preoperatively or that have pneumothorax. Nitrous oxide is delivered in concentrations of 50% to 70%. This decreases the maximum percentage of oxygen that can be delivered, making some patients more susceptible to hypoxemia. Nitrous oxide crosses membranes faster than nitrogen found in air-filled spaces in the body (e.g. pneumothorax, gastric dilatation); nitrous oxide can expand these gas-filled spaces and create additional problems.

John D. Jacobson, DVM, MS, DACVA
College of Veterinary Medicine
Western University of Health Sciences
Pomona, CA 91766

*Current address: 243 Earhart Circle, Lawrence, KS 66049

REFERENCES

1. Roizen MF. More preoperative assessment by physicians and less by laboratory tests. N Engl J Med 2000;342:204-205.

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4. Pypendop B, Serteyn D, Verstegen J. Hemodynamic effects of medetomidine-midazolam-butorphanol and medetomidine-midazolam-buprenorphine combinations and reversibility by atipamezole in dogs. Am J Vet Res 1996;57:724-730.

5. Jacobson JD, McGrath CJ, Ko JC, et al. Am J Vet Res 1994;55:835-841.

6. Steffey EP, Howland D Jr. Isoflurane potency in the dog and cat. Am J Vet Res 1977;38:1833-1836.

7. Klide AM. Cardiopulmonary effects of enflurane and isoflurane in the dog. Am J Vet Res 1976;37:127-131.

8. Quandt JE, Robinson EP, Rivers WJ, et al. Cardiorespiratory and anesthetic effects of propofol and thiopental in dogs. Am J Vet Res 1998;59:1137-1143.

9. Andress JL, Day TK, Day DG. The effects of consecutive day propofol anesthesia on feline red blood cells. Vet Surg 1995;24:277-282.

10. Matthews NS, Brown RM, Barling KS, et al. Repetitive propofol administration in dogs and cats. J Am Anim Hosp Assoc 2004;40:255-260.

11. Thurmon JC, Steffey EP, Zinkl JG, et al. Xylazine causes transient dose-related hyperglycemia and increased urine volume in mares. Am J Vet Res 1984;45:224-227.


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Source: VETERINARY MEDICINE,
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