Anesthetic risk management (Proceedings)

Anesthetic related mortality would appear to be an easily quantifiable statistic that could be used to measure the outcome of the profession's current anesthetic practices. However, to rely solely on death rate as the measure of the quality of anesthetic care provided is inadequate. The anesthetist's goal should be to minimize the risks to the patient's health while reducing pain and stress.

Anesthetic mortality statistics

Veterinary studies

Statistics for veterinary medicine are difficult to compile. There are no systematic methods for reporting anesthetic complications and objective independent assessment of the clinical course of events leading to anesthetic morbidity and mortality are virtually non-existent. However, several retrospective studies have been published which provide insight into the perioperative death rate and provide some guidance to identification of risk factors. Many of these studies have been summarized in a review by Dr. R.S. Jones.

Equine patients

Equine anesthesia has been associated with greater risk due to the size, physiology, and innate behavior of horses. Overall, the death rate is approximately 1.9%. However, when colic surgery is excluded the rate falls to near 0.9%. For horses undergoing anesthesia for colic surgery, the rate is considerably higher (7.9%). The most common causes of death are cardiac arrest, fractures during recovery, and ischemic myopathy. Anesthesia on an emergency basis carries a significantly greater risk. It is important to note that the anesthetic period was defined as being up to seven days following surgery and the records that were reviewed were primarily in referral hospitals.

Small animal patients

Several retrospective studies have been performed over the last 50 years documenting the anesthetic death rate in dogs and cats. In 1955, one study reported that at a single institution the death rate was 1.1% in dogs and 1.8% in cats. The same institution was re-evaluated in 1979 and the death rate decreased to 0.43% in dogs and 0.25% in cats. The main causes of death were human error leading to overdosage and hypoxia. Equipment malfunctions, hypothermia, and cardiovascular failure were also prevalent. In a similar study of 10,000 feline anesthetics, the death rate was similar (0.3%). In this study the main risk factors identified were failure to obtain accurate body weights, failure to utilize premedications, and failure to intubate patients.

A 1990 study in the UK reported mortality rates in dogs and cats of 0.23% and 0.29% respectively. This study stratified patients based on the presence of preexisting pathology and when analysis was complete the death rate increased to 3.12% for dogs with preexisting disease (0.11% for healthy dogs). Cats also had increased risk with pathology (3.33%) and decreased risk when healthy. Subsequent studies have provided similar results.

The most recent study published was an examination of anesthetic related mortality in feline patients in the United Kingdom. The results indicated the overall risk of death is 0.24%. Interestingly they also examined the risk of sedation and general anesthesia and found no increase in risk of death with anesthesia vs. sedation, including sedation with medetomidine. This is contrary to most veterinarians' perceptions. Unexpectedly, an increase risk of death was found with endotracheal intubation and fluid therapy. This confirms earlier reports that endotracheal intubation should be done carefully to avoid tracheal lacerations in cats, but may also be due to the fact that usually older or ill animals are anesthetized with inhalants and given fluids. These studies suggest that as the patient population ages, and more animals with concurrent diseases are anesthetized, anesthetic care must improve in order to reduce or even maintain current mortality rates.

Informed consent

Informed consent is a legal concept which is being re-evaluated in the current political climate. While it has its legal basis in human medical malpractice law, there are peculiarities in veterinary medicine which have led some to suggest the term assumed risk is better in the context of veterinary law. Regardless of the terminology used, the basic legal constructs are similar. A recent review details the concepts and requirements of veterinary informed consent.

Table 1. Information that must be disclosed for consent to be informed.

Anesthetic-related risks are only one item that must be disclosed to clients before anesthetics are delivered. Overstating the risk may result in clients refusing to provide necessary medical or surgical treatments while understatement of risk may lead to legal problems. An additional factor that must be considered is the increasing availability of board certified anesthesiologists in private practice settings. The presence of anesthesiologists in private practice likely increases the level of anesthetic care available to the client (should they be offered a referral) and could impact future malpractice litigation just as it has for surgery and internal medicine.

Conclusions

Good anesthesia is probably best defined as anesthetic protocols and practices which reduce patient morbidity and mortality risk to the lowest level that is reasonably possible while minimizing patient stress and pain. Anesthetic risk will likely never be eliminated, but there are many things that every practice can do to reduce it. The first step is an honest and thorough practice self-evaluation. Areas of high risk should be identified and solutions sought. Simple solutions such as standardizing locations of anesthetic equipment, routine machine checks, intravenous catheterization, airway management, proper supportive care, utilization of appropriate monitoring, and ongoing education of staff can have immediate returns. Communication with the client will also reduce the risk of misunderstanding or unrealistic expectations that may lead to client dissatisfaction or litigation. Finally, communication with an anesthesiologist, either on a consultation or referral basis can improve overall care, reduce risk, and enhance your practice's image.

References

Jones RS. Comparative mortality in anaesthesia. British Journal of Anaesthesia 2001; 87(6):813-5.

Johnston G, Taylor P Holmes M, Wood J. Confidential enquiry of perioperative equine fatalities (CPEF-1): preliminary results. Equine Vet J 1995; 27: 193-200.

Lumb W, Jones E. Veterinary Anaesthesia, 2nd Edn Philadelphia: Lea and Febiger 1973; 611-29.

Dodman N. Feline anesthetic survey. J Small Animal Practice 1977; 10: 653-8.

Clarke K, Hall L. A survey of anaesthesia in small animal practice. AVA/BSAVA report. J Ass Vet Anaesth 1990; 17: 4-10.

Dodman N, Lamb L. Survey of small animal anesthetic practice in Vermont. J Anim Hosp Ass 1992; 28: 439-45.

Gaynor J, Dunlop C, Wagner A, Wertz E, Golden A. Complications and mortality associated with anesthesia in dogs and cats. J Anim Hosp Ass 1994; 35: 13-7.

Dyson D, Maxi M. Morbidity and mortality associated with anesthetic management in small animal veterinary practice in Ontario. J Anim Hosp Ass 1998; 35: 325-35.

Broadbelt DC, et al. Risk factors for anaesthetic-related death in cats: results from the confidential enquiry into perioperative small animal fatalities (CEPSAF). British J of Anaesthesia 99 (5) Sept 2007. 617-23.

Flemming D, Scott J. The informed consent doctrine: what veterinarians should tell their clients. JAVMA 224(9) May 2004, pg 1436-40.