Making Anesthesia Safer
Attention should be paid to brachycephalic breeds, such as bulldogs, under sedation or anesthesia.
Dr. Phil Zeltzman
As the saying goes, “There are routine surgeries, but there is no routine anesthesia.”
The risk of peri-anesthestic death in small-animal practices is 0.23 percent in cats and 0.15 percent in dogs, according to the CEPSAF study.1 Although these numbers are higher than in human medicine (0.02–0.05 percent), it’s a remarkable achievement, knowing that this is the average for all types of patients, healthy or sick.
Lowering this percentage significantly may be difficult. But can we do better? The American College of Veterinary Anesthesiologists (ACVA) certainly believes so. The ACVA is the specialty board that sets standards for advanced professionalism in veterinary anesthesia. Our colleagues recently posted their revised “Recommendations for Monitoring Anesthetized Veterinary Patients”2 on ACVA.org.
The previous guidelines were published in 1995.3
Dr. Cheryl Blaze, a native of Australia and a board-certified anesthesiologist at Tufts’ Cummings School of Veterinary Medicine in Massachusetts, explains: “Our goal is to move from decreased anesthetic mortality toward decreased anesthetic morbidity.”
To reach this ambitious goal, the ACVA suggests guidelines to assess and improve circulation, oxygenation, ventilation and temperature. They also address record keeping, the recovery period, personnel and sedation.
Six ways to evaluate the patient’s circulation are described:
• Palpation of the pulse to determine its rate, rhythm and quality.
• Evaluation of mucous membrane color and capillary refill time.
• Auscultation of the heart, either with a standard or esophageal stethoscope, or with various heart monitors.
• Pulse oximetry to show the percentage of hemoglobin saturation.
• A continuous electrocardiogram (ECG) to detect arrhythmias.
• Blood pressure, either direct, via an arterial catheter, or indirect, via oscillometric method or a Doppler ultrasonic flow detector.
The patient’s oxygenation can be assessed routinely by using a pulse oximeter. For more critically ill patients, a blood gas sample can be analyzed.
The patient’s ventilation can be evaluated through simple observation of sufficient movements of the thoracic wall or the breathing bag. Breath sounds can be auscultated with an external or esophageal stethoscope, or with an audible respiratory monitor. Most accurate means of assessing ventilation include capnography (CO2 measurement) and blood gas analysis.
Body temperature can be measured intermittently with a rectal thermometer, or continuously with a rectal or esophageal probe. Temperature should be measured regularly during anesthesia, throughout recovery and after returning to the kennel.
The ACVA advises: “Frequent or continuous monitoring and recording of vital signs in the peri-anesthetic period by trained personnel and wisely using various monitors are requirements for advancing the quality of anesthesia care of veterinary patients.”
Record keeping is critical, both for medical and legal reasons. From a medical standpoint, the goal is to help recognize trends or unusual values, which allows reacting quickly with the appropriate response.
From a legal standpoint, things are easy to understand. Should a serious problem arise, how do you prove that no human error was responsible when our good friends from the state board show up?
What to Record?
• All drugs administered during the peri-anesthetic period and in early recovery. Note doses, times and route of administration.
• Vital signs, at a minimum of every five to 10 minutes. At the very least, record heart and respiratory rates, oxygenation status and blood pressure.
• Any special procedure performed, such as “a second 18G IV catheter was placed in the left cephalic vein” or “placed urinary catheter and connected to closed collection system.”
Record any unusual circumstance, again for medical and legal reasons. For example, if you notice reflux of gastric fluid in the oral cavity or sudden blood loss, document it and what was done about it. Similarly, document adverse drug reactions so that, should the patient require anesthesia again, the protocol can be altered.
Dr. Phil Zeltzman
Patients under sedation also should be monitored, including the use of pulse oximetry.
Continue monitoring during the recovery period to ensure a safe and comfortable recovery from anesthesia.
Respiratory pattern (especially in brachycephalic breeds), mucous membrane color, CRT and pulse should be monitored. The patient’s status will guide other requirements, such as glycemia, pulse oximetry, hematocrit, total protein and blood gases.
The patient’s temperature should be checked every 30 minutes until it is normal. It is the only way to know when to stop rewarming procedures. After that, the temperature can be measured every few hours. Occasionally, a cat receiving opioids can become hyperthermic.
“We should pay close attention to signs of pain and try to understand its cause. Is it related to the surgery, or could it be because the bandage is too tight or the patient has a full bladder? Finding out the source of the pain or discomfort or anxiety is important before we automatically reach for more drugs,” Dr. Blaze suggests.
Ideally, a veterinarian, technician or other responsible person should remain with the patient continuously during anesthesia and be dedicated to that patient only. The goal is to be aware of the patient’s status at all times through recovery.
If something needs to be corrected, or something goes wrong, that person should be prepared either to intervene or to alert the clinician in charge.
If that is not possible, a reliable and knowledgeable person should check the patient’s status at least every five minutes during anesthesia and recovery.
The ACVA makes very clear recommendations for sedated patients: “If a sedated patient is ‘deep’ enough to lose control of protective airway reflexes, it should be monitored as well as if under general anesthesia.”
Vital signs monitored should include pulse, mucous membrane color, CRT, respiratory rate, auscultation and pulse oximetry.
“This should be routine,” Dr. Blaze says.
Supplemental oxygen, an endotracheal tube and materials for IV catheterization should be readily available. Pay scrupulous attention to brachycephalic breeds that are particularly at risk for airway obstruction under heavy sedation and anesthesia.
Following the American College of Veterinary Anesthesiologists’ recommendations is a sure way to improve the level of anesthesia care of your patients.
1. DC Brodbelt et al. “The risk of death: the Confidential Enquiry into Perioperative Small Animal Fatalities.” Veterinary Anaesthesia and Analgesia, 2008, Vol. 35, p. 365–373. www.vmedtech.com/Post-surgical%20deaths.pdf
2. http://acva.org/professional/Position/Recommendations_Monitoring_Anesthetized_Veterinary_Patients_2009.htm 1. JAVMA 1995, Vol 206, N 7, p. 936-937.
Dr. Phil Zeltzman is a mobile, board-certified surgeon near Allentown, Pa. His website is DrPhilZeltzman.com.