Vet360 Vet360 Vol 05 Issue 03 - Page 11

Article reprinted with permission of DVM360 – June 23, 2016. DVM360 MAGAZINE is a copyrighted publication of Advanstar Communications inc. All rights reserved ANAESTHESIOLOGY Just Ask the Expert Light Anaesthesia Anxiety By Andrew Claude, DVM, DACVAA Are your surgical patients all sufficiently anesthetised? There are lessons for all veterinary practices in deciphering the cause of inadequate anesthetic depth in routine procedures. Here is a step-wise guide on what to consider as you perform your root-cause analysis. Based on the context of the question above it seems you have placed most of the concerns for the patient issues on the scavenging system. Granted, there are key points about the scavenging system to consider, but there are also important details concerning the patient that are of equal importance. Q. Recently, we have noticed that our anesthetized patients have heart rates that don't correspond with their respiration rates in terms of their plane of anaesthesia. Their heart rates seem to reflect stage 3, plane 2 anaesthesia, but their respiration rates reflect stage 3, plane 1 anaesthesia (e.g. a 100-lb dog with a heart rate of 100 to 110 beats/minute but respiration is 60 breaths/minute or more). These patients are easily awakened by stimuli such as turning them over or stimulating a sore tooth when performing a dental cleaning. We find we are constantly having to turn up the isoflurane. We originally thought we had a problem with our medical gas scavenging system. However, we recently performed a test to determine if the scavenging system has the correct amount of suction, and the results were normal. We are back to square one. I would greatly appreciate any thoughts you have on this. 1. What are the typical anaesthetic protocols being used for these patients? A. This is a very interesting question with two major categories to consider—the circumstances regarding the patient and those of the scavenger system. Commonly, premedication protocols use the combination of a tranquilizer and an opioid (neuroleptanalgesia). Multiple publications state that analgesics used before and during surgery decrease the dose of both the induction drugs and the maintenance inhalants (mean alveolar concentration, or MAC). Local and regional anesthetic techniques are also effective in decreasing the MAC of inhalant anesthetics. Without preoperative and intraoperative analgesia, anesthetised patients will be subject to sudden light planes of anaesthesia necessitating multiple top-up administration of induction drugs and increased doses of inhalant anaesthesia. In my opinion, in dogs and cats, if you are routinely running your isoflurane vaporizer greater than 1.75% (sevoflurane > 2.5%) during surgical procedures (e.g. ovariohysterectomy, orthopaedics), your analgesia protocols should be reconsidered. Contrary to Issue 03 | JULY 2018 | 11