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
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