Anesthesia Guidelines: Macaques

Research Animal Resources (RAR) veterinary staff designed these guidelines to be general recommendations, not an inclusive list of all possible drug combinations that can be used for non-human primates (NHPs), or macaques.

Consequently, they do not include reference to specific research-associated concerns. If you have questions about using anesthetics for your particular situation, please work with your area veterinarian to develop the most effective anesthetic plan.

General Considerations

Heat Support

Because most anesthetic drugs cause hypotension and hyperthermia, provide supplemental heat under anesthesia. Supplemental heat sources include circulating water blankets, air heating devices or commercial products that can be heated up or create heat via a safe chemical reactions. NO electric heating pads are allowed for use with nonhuman primates. Regardless of heat source, never place animals directly on the heat.

Catheterization

Following sedation, place an indwelling catheter to administer anesthetic drugs, emergency drugs, and intravenous fluid support. The most common sites for catheter placement are the saphenous and cephalic veins.

Fluid Support

Provide supplemental fluid support for animals that will be under anesthesia for longer than 30 minutes. Appropriate fluid rates range from 5-10 mls/kg/hour, and may vary based on the anesthetic combination used.

Monitoring

Standard mammalian monitoring techniques apply to NHPs. The goal of monitoring should be to maintain cardiovascular homeostasis and core body temperature.

Understanding the basic physiologic effects of the anesthetics used is paramount to correctly interpreting monitoring parameters. View descriptions of anesthetic agents.

Parameters to monitor in anesthetized NHPs include anesthetic depth, heart rate, respiratory rate, oxygen saturation, expired CO2 (EtCO2), temperature, blood pressure, and mucous membrane color.

Normal ranges (without anesthesia)

Temperature = 98.0-102.5°F
Heart rate (beats/minute) = 150-220
Respiratory rate (breaths/minute) = 10-40 resting
Blood pressure = >60 mm Hg (mean) and >90 mm Hg (systolic)
Oxygen saturation = >95%
EtCO2 = 35-45
Mucous membranes = pink, not pale, white, gray, or blue

Normal ranges (with anesthesia)

Respiratory rate (breaths/minute): A 10-20% decrease is acceptable during anesthesia
EtCO2: A CO2 up to 55 is acceptable during general anesthesia

For more involved procedures, EKG, invasive pressure monitoring, and blood gas analysis may be indicated. For long procedures, mechanical ventilation is recommended.

Anesthetic Drugs & Procedures

NHP anesthesia is generally broken into premedication (sedation), anesthetic induction, and anesthetic maintenance.

As with other species, anesthesia (maintenance) can be accomplished via inhalation or parenteral methods.

SEDATION

Administering sedative drugs decreases excitement and causes relaxation to allow for the placement of indwelling catheters (for IV drug and fluid administration) or allow for intubation (for inhalation anesthesia).

Induction (see below) is often required in addition to sedation to provide a sufficient level of sedation/anesthesia for intubation.

Ketamine (5-10 mg/kg) is the most commonly used agent for chemical restraint of nonhuman primates. It has a wide margin of safety and is generally combined with drugs that provide a component of muscle relaxation. See chart below for suggested drug combinations.

The anticholinergics glycopyrrolate (0.004-0.01 mg/kg IM) or atropine (0.04 mg/kg IM) may be used as a premedication to dry oral and respiratory secretions and for its vagolytic effects (i.e., ability to block vagal nerve stimulation and consequent bradycardia) during endotracheal intubation.

Ketamine

Dose: Ketamine: 5-25 mg/kg
Route: Intramuscular (IM)

Ketamine + Dexmedetomidine

Dose: Ketamine: 5-10 mg/kg + Dexmedetomidine: 0.01- 0.03 mg/kg
Route: Intramuscular (IM)
Comments: Dexmedetomidine can be reversed with the same volume of Atipamezole as the volume of Dexmedetomidine used.

Ketamine + Diazepam

Dose: Ketamine: 5-10 mg/kg + Diazepam: 0.5 mg/kg
Route: IM

Ketamine + Xylazine

Dose: Ketamine: 7 mg/kg + Xylazine: 0.6 mg/kg
Route: IM
Comments: Yohimbine can be used for Xylazine reversal: 0.1-1.0 mg/kg IV. Atipamezole may also be used for reversal: 0.1-0.2 mg/kg IV or IM.

INDUCTION

Induction refers to an anesthetic administered to place an animal in an unconscious state and allow for tracheal intubation.

Isoflurane

Dose: 2-4%
Route: Inhalation/facemask

Propofol

Dose: 2-5 mg/kg bolus
Route: IV
Comments: Give slowly to effect. Propofol causes respiratory depression. Animals receiving propofol should be intubated following administration. Propofol given as a bolus can cause hypotension.

MAINTENANCE

Maintenance refers to drugs administered to keep animals unconscious and allow for surgical (or other) procedures to be performed.

Endotracheal intubation: Inhalation anesthesia may be delivered by a facemask, but is generally delivered via endotracheal intubation.

NHPs can be intubated using a laryngoscope.
Endotracheal tube sizes vary and generally range from 3-5 mm for NHPs. When attempting intubation, have several sizes available and ready with appropriate ties. Use the largest size that can be passed through the larynx without causing trauma.
Applying sterile surgical lubricant to the tip of the endotracheal tube will help facilitate intubation.
The endotracheal tube should extend approximately from outside of the mouth to the thoracic inlet. This can be used as a guide for how far the tube should be inserted upon intubation.
Verify proper placement of the endotracheal tube by ausculting all lung fields for strong breath sounds. If no breath sounds are heard, back the tube out until sounds are heard in all lung fields.
Endotracheal tubes need to have a cuff, and cuffs need to be inflated during anesthesia. Inflate the cuff just enough to stop gas leakage. Over-inflation of the endotracheal tube cuff can damage the trachea.

Gas anesthesia machines: Facemasks and intubation require gas anesthesia machines with an oxygen source and a precision vaporizer. For most macaque species (> 5 kg), use a rebreathing system.

Gas scavenging systems: When using inhalant anesthesia, use an anesthetic system equipped with a gas scavenging system to minimize occupational exposure to exiting gases.

Ophthalmic ointments: For anesthetic events lasting more than five minutes and whenever facemasks are used, apply an ophthalmic ointment (e.g., Paralube® or Lacrilube®) to eyes to prevent corneal drying and trauma.

Isoflurane

Dose: 1-2%
Route: Inhalation/endotracheal tube