Oops-anesthetic accidents: prevention and response (Proceedings)


Anesthetic mishaps can lead to patient morbidity and mortality. Most problems anesthesia-related problems can be prevented by advanced planning, training, patient monitoring, and the development of standard operating protocols.

Anesthetic mishaps can lead to patient morbidity and mortality. Most problems anesthesia-related problems can be prevented by advanced planning, training, patient monitoring, and the development of standard operating protocols.

Anesthesia-associated mortality:

Pet owners expect their veterinarians to choose safe anesthetic protocols, use functional anesthesia equipment, monitor their animals while anesthetized, and prevent and treat pain associated with diagnostic or therapeutic procedures. Over the past decade, technology to anesthesia monitoring and our understanding of physiology and pharmacology has advanced rapidly. Unfortunately, the actual practice of veterinary anesthesia has not evolved quite as rapidly. Thus, it is not surprising that anesthetic mortality in animals is higher than seen in human beings. A recent study in small animals reported that overall risk of anesthesia and sedation-related death was 0.17, 0.24, and 1.39% in dogs, cats, and rabbits (Vet Anes Analg 2008). The risk in 'healthy' animals was ~0.05%. This is better than the risk reported for horses (0.9%) but much worse than reported for human beings (~ 0.0075%). Here are a few findings of interest:

     • More than one-half of all anesthetic-related mortalities occurred in the postoperative period.

           o Could increased postoperative monitoring decrease mortality?

     • Sick animals are more likely than healthy animals to suffer an anesthetic-related death

           o ASA status 3-5: The ASA Classification system does help to stratify risk

           o How should we alter anesthetic management for sick animals?

     • Cats have higher anesthetic-related mortality than dogs (even 'healthy' ASA 1-2 animals)

           o Smaller

           o difficult to monitor

           o easily stressed

           o physiological differences

     • Risk for anesthetic death in small animals appears to be decreasing

           o Better drugs?

           o Better monitoring?

           o Better training?

     • Animals given sedation alone MAY be at decreased risk compared to anesthetized animals.

Other studies in veterinary medicine have shown:

     • monitoring decreases mortality

     • alpha two agonists may increase mortality

     • acepromazine may decrease mortality.

Preanesthetic Assessment:

Attention to signalment, history, physical examination and laboratory findings may be useful in minimizing anesthesia-related problems. The following is a list of common problems that should be associated with an adjustment in management:

     • Breed issues

     • Heart Disease (especially when patient is in failure)

     • Renal failure

     • Liver disease

     • Neurologic disease

Anesthesia Equipment:

Anesthesia equipment used in veterinary medicine today is generally simple and reliable. However, safe use requires an understanding of the principles of operation and effects of anesthetic drugs. Moreover, regular maintenance is important to insure reliable machine operation.

          • Common sources of problems include:

          • One-way valve operation

     • Leaks

     • Oxygen supply

     • Pressure-relief valve

     • Disconnections

Patient Monitoring:

Monitoring of patient well-being is important to recognizing anesthetic-related problems before they lead to morbidity or mortality. Assigning a trained individual to assess patient well-being is probably the most important part of veterinary anesthetic management.

The advantages and disadvantages of specific monitoring tools will be discussed:

     • Pulse oximetry

     • Capnography

     • Blood pressure monitoring

Personnel, Planning, and Procedures

A recent investigation of anesthetic mishaps in a human hospital showed that most (82%) preventable incidents involved human error (Qual Saf Health Care 2002). Some of the most frequent errors identified in this study included breathing circuit disconnections, inadvertent changes in gas flow, and 'syringe' swap'. This study showed that about half of the preventable errors occurred during anesthesia maintenance.

The high prevalence of human error points to the need to develop systems, training, and protocols that minimize the risks for these errors. Most of the things that we can do in our practices to decrease morbidity and mortality are simple and inexpensive. The following practices are summarized from a report generated by the UCSF-Stanford University Evidence Based Practice Center called 'Making Health Care Safer: A Critical Analysis of Patient Safety Practices'. There are several interesting conclusions related to anesthesia and surgery that may have a place in your practice:

     • Practice makes perfect: There is a statistical relationship between the number of times a physician performs a procedure in a year and the outcome.

     • Unless high volume becomes a distracting priority!!!

     • Technical training decreases morbidity: The relationship between technical training and success has been documented particularly well in minimally invasive surgery.

     • Keep your patients warm! Hypothermai is commonly associated with anesthesia. and has been shown to decrease immune function, affect healing, and increase the risk of surgical infection.

     • Oxygen is almost always a good thing! Studies looking at intra and perioperative oxygen supplemention have shown that oxygen administration can reduce the risk of postoperative infection. There is some evidence that it may decrease incidence of admission into the intensive care unit and may decrease mortality! Remember that high concentrations of oxygen are a fire hazard and may increase the risk of lung injury when given for an extended time.

     • Create a check list for your practice's anesthesia SOP: Your Check list should include (but need not be limited to assessment of anesthesia and monitoring equipment, patient preparation, and supply preparation

     • Monitor your patients: Routine noninvasive monitoring carries minimal risk for our patients, and should be considered. Pulse oximetry and capnography are frequently cited as the most important noninvasive monitors in human anesthesia practice. Pulse oximeters may also be valuable in the recovery period and after extubation. The American Society of Anesthesiologists recommend the following standards for basic anesthesia monitoring:

     • QUALIFIED anesthesia personal should be present for anesthesia procedures

     • The patient's oxygenation, ventilation, circulation, and temperature should be continually evaluated.


A comprehensive approach to the prevention of anesthesia-related problems is essential for practitioners. Proper training of staff, equipment maintenance, patient assessment/preparation and patient monitoring are the cornerstones of safe anesthesia. The following is a ten step approach that can help to set a standard of care for the anesthesia portion of your practice. It is adapted from a list published by Dr. Sandra Forsyth and presented at the World Small Animal Veterinary Association in 2007:

      1. Weigh the patient

      2. Do a physical examination on every patient

      3. Perform routine checks on your anesthetic equipment and provide for routine maintenance

      4. Preoxygenate patients with cardiopulmonary disease (or critical patients)

      5. Use proper intubation technique

      6. Use intravenous catheters

      7. Monitor the patient under anesthesia

      8. Double-check doses

            a. Adjust when necessary

      9. Don't forget about recovery

     10. Be a pessimist (i.e., expect and plan for the worst)

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