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      Using Capnography to Detect Anesthetic Complications


      By measuring carbon dioxide (CO2) in a patient’s breath, capnography provides a more complete picture of the patient’s respiratory process (metabolism, circulation, and ventilation) during an anesthetic procedure. It can also provide valuable insights on physiologic factors affecting CO2 levels and assist in detecting a multitude of equipment problems and malfunctions to help care teams identify—and mitigate—potential complications.

      The American Animal Hospital Association (AAHA) recognizes the importance of monitoring ventilation by end-tidal CO2 (EtCO2) and noted, “most patient complications will first be detected through use of an anesthetic monitor. For that reason, the anesthetist should be comfortable interpreting patient parameters such as ECG, EtCO2, BP, SpO2, and body temperature.”1



      Why is measuring CO2 important to patient safety?

      In a closed-claim analysis, anesthesiologists who reviewed 346 anesthetic-related closed malpractice claims that resulted in death or serious injury of human patients determined that pulse oximetry and capnometry (applied together and each alone) may have potentially prevented 93% of the preventable negative outcomes.2

      Despite the potential for preventing anesthetic mishaps by monitoring CO2, not all veterinary clinics utilize capnography. Yet many veterinary clinicians can attest that changes in the CO2 waveform provide the earliest indication of complications.



      Capnography’s clinical application

      Monitoring capnography and watching for changes in the capnogram or waveform can help teams detect common anesthetic complications such as:

      • Hypoventilation
      • Hyperventilation
      • Rebreathing CO2
      • Malfunctioning Unidirectional Valve
      • Exhausted CO2 Absorbent
      • Esophageal Intubation
      • Effectiveness of Chest Compressions During CPR

      The Reassessment Campaign on Veterinary Resuscitation (RECOVER3) initiative has guidelines that recommend EtCO2 monitoring for patients at risk of cardiopulmonary arrest.



      How can a CO2 library support decision-making?

      Some monitoring devices are designed with an integrated CO2 library that enables care teams to quickly match their CO2 waveform with a common anesthetic occurrence or a life-threatening obstruction. When your team has questions about a patient’s capnogram, they can easily scroll through the library to find a visual match eliminating some of the guesswork in identifying possible problems—major or minor. In-the-moment access to this kind of information can boost your team’s confidence in making clinical decisions during a procedure.



      What about equipment issues and malfunctions?

      Equipment problems and malfunctions can also be detected through capnography. In addition to accidental esophageal intubation, monitoring CO2 can alert staff to other complications including unidirectional valve malfunction or exhausted CO2 absorbent.



      Final Thoughts

      Capnography is a valuable tool for evaluating and monitoring anesthetized patients. Understanding the waveform of a normal capnograph and recognizing different variations enables your staff to identify abnormal capnograms and act quickly to avert complications. The result? Your team will be more confident during anesthetic procedures and positioned to deliver a safer patient care experience.




      1 American Animal Hospital Association, 2020 AAHA Anesthesia and Monitoring Guidelines for Dogs and Cats.
      2 John H. Tinker, David L. Dull, Robert A. Caplan, Richard J. Ward, Frederick W. Cheney; Role of Monitoring Devices in Prevention of Anesthetic Mishaps: A Closed Claims Analysis. Anesthesiology 1989;71(4):541-546.
      3 RECOVER Initiative: