BP and capnography work together to ensure perfect harmony
When asked about her favorite anesthesia monitoring parameters, Tasha McNerney, BS, CVT, CVPP, VTS (anesthesia and analgesia), says blood pressure (BP) and capnography are the most valuable tools in her anesthesia monitoring arsenal. Wondering what these tools can do for you? Read on for insight gleaned from her Fetch dvm360 Launchpad Learning session, “Anesthesia basics and beyond: Things you learned in school but have forgotten.” (Psst, you can catch a repeat of this moment in anesthetic history at Fetch dvm360 conference West.)
You down with ol’ BP?
When it comes to BP, what should you be looking for? When do you alert the doctor?
McNerney stresses the importance of developing a protocol for your clinic so that everybody knows what to expect and the technicians know what to do—such as starting a fluid bolus or dobutamine if the pressure is too low. This not only empowers the technician, but it frees up brain space for the veterinarian. At McNerney’s clinic, they aim for a systolic BP > 90 mm Hg, a diastolic > 40 mm Hg, and a mean arterial pressure (MAP) > 65 mm Hg for all patients, regardless of who is performing the anesthesia. Most textbooks will say MAP > 60 mm Hg, but McNerney says if you are trending three measurements in a row with a MAP < 60 mm Hg, then blood flow to vital organs could be compromised. To avoid that, keep MAP > 65 mm Hg.
Want to take your anesthesia monitoring skills to the next level? Consider learning how to perform invasive BP monitoring. This requires some training but it’s considered the gold standard, and McNerney highly recommends it for cardiovascularly compromised patients. Learning this technique can increase your value to your clinic and increase the safety for your patients. By the way, McNerney works in private practice and performs invasive BP monitoring—so if she can do it, you can do it!
Aye aye, cap(nography)!
End-tidal carbon dioxide (CO2) is one of McNerney’s favorite monitoring parameters. Capnography tells you how your patient is ventilating and indirectly gives you information on cardiac output and volume status. End-tidal CO2 can tell you very early if there’s a problem within your breathing circuit. For example, is there a problem in the tubing or machine? The capnograph can tell you before you detect it, even if you have done a leak test! All sorts of mechanical dysfunctions, such as sticky valves or closed pop-off valves, can cause an elevated baseline and alert you to problems in your system.
Here are McNerney’s pro tips for capnography:
• Capnography is very helpful with cardiopulmonary resuscitation (CPR). CO2 levels below 20 mm Hg will show you that you have ineffective chest compressions and you either need to tag out for another person or switch your position.
• An abnormal plateau that trails down is due to a leak somewhere. McNerney finds that this is often caused by a leak around the cuff after a pet has been anesthetized for a while due to relaxation and depth of anesthesia.
• Cardiogenic oscillations are due to vibrations in deep-chested dogs and are an artifact. Don’t treat.