Anesthetic agents coupled with invasive procedures can cause dramatic hemodynamic changes in the patient’s cardiorespiratory system. In addition, each patient exhibits different physiologic and pharmacologic responses to various anesthetic agents. Because these responses are not always predictable, it is vital to monitor each patient closely and provide supportive care throughout the anesthetic and surgical event. Prompt detection of respiratory and/or hemodynamic changes allows the anesthetist time to properly identify the problem and intervene. This page provides ARC best practice recommendations for performing/monitoring anesthesia on non-rodent species.
- The patient’s initial vitals should be taken and recorded manually as soon as the animal is sedated and removed from the cage (stethoscope used to monitor HR and RR), and every 15 minutes following initial assessment (using monitoring equipment or manually).
- Shaving for catheter placement and surgical sight shaving should be done in a prep space and not in the operating room to prevent hair contamination of the area.
- IV access should be maintained in all anesthetized animals even if injectable anesthesia is not being utilized. This can be achieved by placing an intravenous catheter during pre-procedural preparation of the animal. Intravenous access provides a means to administer fluids and administer emergency drugs if the need should arise. The catheter should remain in place as long as possible, and removed only when the animal is nearly fully recovered.
- Appropriate physiological parameters should be monitored during anesthesia. This includes (but is not limited to) monitoring of heart rate, oxygen saturation, respiratory rate, end tidal CO2, and body temperature. If at any point the ability to monitor any of these values is lost (due to equipment malfunction), all attempts should be made to restore the monitoring capabilities. If they cannot be restored and the animal is stable according to all other parameters being monitored, the animal assessed manually.
- IV fluids should be administered throughout anesthesia at a rate of 5-10 mls/kg/hour unless the blood pressure is being continuously monitored and the animal’s mean arterial pressure (MAP) remains above 90 mmHg throughout the procedure. This fluid support will help maintain blood pressure during anesthesia, allow for adequate perfusion of vital organs, prevent intra-anesthetic dehydration, and allow for a more rapid recovery following anesthesia. A good rule of thumb is to administer fluids at 10 mls/kg/hour for the first 2 hours, and then turn fluids down to 5 mls/kg for the remainder of the procedure unless hypotension requires additional fluid.
- During anesthesia, animals are not able to thermoregulate normally, which leads to a lower core body temperature that may progress to hypothermia. Hypothermia can result in prolonged recovery from anesthesia as well as other complications. External heat support and temperature monitoring should be provided throughout the anesthetic event, beginning at induction of anesthesia. Care should always be taken with any supplemental heat source to avoid burns or hyperthermia. Warming devices and hot water bottles should be wrapped in a towel or other barrier so that the heat source is not in direct contact with the animal’s skin. Supplemental heating should be discontinued if the body temperature reaches 99.0°F. Additional heating should be added if the patient’s temperature falls below 96.0°F.
- All animals should be intubated. To ensure proper placement of the tube, it should be of appropriate size (2/3 size of the trachea) and should not extend past the carina (~4th intercostal space). If the animal is not deep enough to intubate following initial sedation drugs, supplemental isoflurane should be given via mask to provide a plane of anesthesia sufficient for intubation. Cetacaine spray or lidocaine gel on the larynx can be used to minimize spasms and facilitate intubations. Tracheal tube stylets will make placement of ET tubes easier.
- Once the animal is intubated, correct placement should be confirmed by ausculting the upper and lower quadrants of both right and left lung fields and ensuring breath sounds can be heard throughout all quadrants. Improper placement can lead to only one lung field being ventilated with resultant collapse of the other side. Additionally, when placing the tube it is important not to be too forceful or to overinflate the cuff as tissue damage may occur, leading to inflammation of the airways and potential recovery complications.
- Pre-emptive analgesia should be used (provision of pain management drugs prior to the onset of pain). However, NSAIDS do have a risk to increase bleeding and decrease blood flow to the kidneys. As such, it is good practice to administer Buprenorphine prior to beginning surgery, and then every 8-12 hours after. Carprofen can be given when the surgery is complete prior to turning the animal off anesthesia.
- Mechanical ventilation should be provided for all patients that will be under anesthesia for longer than 2 hours. If this is not feasible due to the available equipment or type of procedure, the patients should be manually ventilated with one deep breath (to 20 cm/H20) every 5-10 minutes.
- If animals will be anesthetized for shorter periods and are able to maintain EtCO2 between 35-45 mmHg (or 5-6%) while breathing spontaneously, mechanical ventilation is not required. If spontaneous respiration is unable to maintain EtCO2 between 35-45 mmHg at any point, mechanical ventilation should be employed. Until the ventilator is in place, the patient should be bagged once the ETCO2 reaches 50 with several deep breathes (keeping the pressure below 20 cm H20) until the CO2 returns to normal range.
Starting points for ventilation: Tidal volume – BW (in KG) X = 12
Respiratory Rate = 12
I:E = 1:2
- Following any anesthetic or sedation event, animals should be monitored per the ARC post- operative best practice guidelines:
Macaques should be continuously monitored until the animal is sitting up in its cage with the squeeze fully retracted to open up the floor space, at which time people can leave the room for brief periods while the animal continues to be checked every 5-10 minutes for another 60-90 minutes. Postoperative care records should clearly document these checks.
- Bonded macaque pairs often suffer from anxiety (leading to incision picking) when separated. Re-pairing can be done as soon as the anesthetized animal is ambulatory and no longer ataxic. Repairing of marmosets following surgery should be made on a case by case basis.