American College of Veterinary Anesthesiologists Monitoring Guidelines Update, 2009
This document may be accessed on line at http://acva.org/under “ACVA Position Statements.”
The American College of Veterinary Anesthesiologists (ACVA) has revised the set of guidelines for anesthetic monitoring that were originally developed in 1994 and published in 1995.∗ Since then many factors have caused a shift in the benchmark used to measure a successful anesthetic outcome, moving from the lack of anesthetic mortality toward decreased anesthetic morbidity.
This shift toward minimizing anesthetic morbidity has been facilitated by more objective definition and earlier detection of pathophysiologic conditions such as hypotension, hypoxemia, and severe hypercapnia. This has resulted from the incorporation of newer monitoring modalities by skilled attentive personnel during anesthesia.
The ACVA recognizes that it is possible to adequately monitor and manage anesthetized patients without specialized equipment and that some of these modalities may be impractical in certain clinical settings. Furthermore, the ACVA does not suggest that using any or all the modalities will ensure any specific patient outcome, or that failure to use them will result in poor outcome.
However, as the standard of veterinary care advances and client expectations expand, revised guidelines are necessary to reflect the importance of vigilant monitoring. The goal of the ACVA guidelines is to improve the level of anesthesia care for veterinary patients. Frequent and continuous monitoring and recording of vital signs in the perianesthetic period by trained personnel and the intelligent use of various monitors are requirements for advancing the quality of anesthesia care of veterinary patients.
1. Palpation of peripheral pulse to determine rate, rhythm, and quality and evaluation of mucous membrane (MM) color and capillary refill time (CRT).
2. Auscultation of heartbeat (stethoscope; esophageal stethoscope or other audible heart monitor). Continuous (audible heart or pulse monitor) or intermittent monitoring of the heart rate and rhythm.
3. Pulse oximetry to determine the % hemoglobin saturation.
4. Electrocardiogram (ECG) continuous display for detection of arrhythmias.
Continuous awareness of heart rate and rhythm during anesthesia, along with gross assessment of peripheral perfusion (pulse quality, MM color, and CRT) are mandatory. Arterial blood pressure and ECG should also be monitored. There may be some situations where these may be temporarily impractical—for example, movement of an anesthetized patient to a different area of the hospital.
1. Observation of thoracic wall movement or observation of breathing bag movement when thoracic wall movement cannot be assessed
2. Auscultation of breath sounds with an external stethoscope, an esophageal stethoscope, or an audible respiratory monitor
3. Capnography (end-expired CO2 measurement)
4. Arterial blood gas analysis for carbon dioxide partial pressure (Paco2)
For any patient in which neuromuscular blockade is used, it is essential to control ventilation, monitor closely for signs of awareness, and be certain of recovery of blockade before anesthesia recovery. Recovery of neuromuscular function may be assumed if the evoked response (twitch and/or tetanic fade) to a nerve stimulus, and respiratory tidal volume as measured with a spirometer, return to at least 70% of preblockade status. End tidal CO2 may also be used as an indication of adequate ventilation in spontaneously ventilating patients.
1. Record all drugs administered to each patient in the perianesthetic period and in early recovery, noting the dose, time, and route of administration, as well as any adverse reaction to a drug or drug combination.
2. Record monitored variables on a regular basis (minimum every 5 to 10 minutes) during anesthesia. The minimum variables that should be recorded are heart rate and respiratory rate, as well as oxygenation status and blood pressure if these were monitored.
3. Record heart rate, respiratory rate, and temperature in the early recovery phase.
4. Any untoward events or unusual circumstances should be recorded for legal reasons, and for reference should the patient require anesthesia in the future.
1. Observation of respiratory pattern
2. Observation of MM color and CRT
3. Palpation of pulse rate and quality
4. Measurement of body temperature, with appropriate warming or cooling methods applied if indicated
5. Observation of any behavior that indicates pain, with appropriate pharmaceutical intervention as necessary.
6. Other measurements as indicated by patient’s medical status—for example, blood glucose, pulse oximetry, PCV, TP, blood gases, and so on.
To ensure that a responsible individual is aware of the patient’s status at all times during anesthesia and recovery and is prepared either to intervene when indicated or to alert the veterinarian in charge about changes in the patient’s condition
1. Ideally, a veterinarian, technician, or other responsible person should remain with the patient continuously and be dedicated to that patient only.
2. If this is not possible, a reliable and knowledgeable person should check the patient’s status on a regular basis (at least every 5 minutes) during anesthesia and recovery.
3. A responsible person may be present in the same room, although not necessarily solely occupied with the anesthetized patient (for instance, the surgeon may also be responsible for overseeing anesthesia).
4. In either 2 or 3 above, audible heart and respiratory monitors must be available.
5. A responsible person, solely dedicated to managing and caring for the anesthetized patient during anesthesia, remains with the patient continuously until the end of the anesthetic period.
Sedation is a state characterized by central depression accompanied by drowsiness during which the patient is generally unaware of its surroundings but responsive to noxious manipulation.†
If a sedated patient is sufficiently obtunded to lose control of protective airway reflexes, it should be monitored as under general anesthesia.
Intermittent monitoring of basic respiratory and cardiovascular parameters in the heavily sedated animal should be routine. Supplemental oxygen, an endotracheal tube, and materials for IV catheterization should always be readily available. Particular attention should be paid to brachycephalic breeds that are particularly at risk for airway obstruction under heavy sedation.