GENERAL PRINCIPLES OF CHEMICAL RESTRAINT OF WILD AND ZOO ANIMALS

GENERAL PRINCIPLES OF CHEMICAL RESTRAINT OF WILD AND ZOO ANIMALS

CHEMICAL IMMOBILIZATION OF WILD ANIMALS

·         Wild animals are chemically restrained for the following reasons

o    Animal translocation and transportation

o    To study the ecology and population estimate

o    For veterinary studies

o    To relieve wild animals in distress

o    Control of animals causing distress to the public

·         Various devices used for injecting the drug from a distance are drug darts, projectile syringes (short range, long range, and extra long range), blow gun rifle, blow pipe, and stick syringe.

Primates

• Ketamine – 5-20 mg /kg intramuscular
• Xylazine 2 mg/kg intramuscular

Chimpanzee

• Ketamine 10-15 mg/kg body weight
• Xylazine 2 mg/kg

Kangaroo

• Xylazine 8 mg/kg body weight and Ketamine 3 mg/kg combination
• Thiopentone less than 20 mg/kg body weight

Antelope

·         Xylazine 0.23 mg /kg and Ketamine 11.54 mg/kg body weight combination

Deer

• Xylazine 0.89-8.0 mg/kg body weight
• Ketamine 10-20 mg/kg body weight

Camels

• Xylazine 0.27-0.51 mg/kg intramuscular

Bears

• Xylazine 2-4 mg/kg and Ketamine 4.5-9mg/kg (Combination)

Bison

• Chloral hydrate 250mg/kg body weight

Elephant

·         Asian elephant 100-175 mg Xylazine (total dose)

·         Etorphine-Acepromazine combination (2.4 mg/ml-Etorphine and 10mg/ml of Acepromazine per ml) Dose 1 ml/4 feet of shoulder height

Reptiles

• Ketamine 20 mg/kg intramuscular
• Xylazine 1 mg/kg

Snakes

• Ketamine 50-130 mg/kg intramuscular
• Tiletamine 10-20 mg/kg intramuscular

Fish

Carbon dioxide 400ppm/20 mints

Tricaine methanosulfonate(FDA approved) -0.5 to 1 gm/gallom of water at 40-60 deg F.

Anaesthesia in fish is indicated by decreased opercular movements,  muscle tone at the end of tail and tactile and vibrational stimuli.

Bats

Chlorpromazine 2.5 mg/100gm I/M

Inhalation by Halothane or Isoflurane at 0.05mg/gm I/P.

Squirrels

Isoflurane/Halothane in induction chamber

Ketamine at 10-20mg/kg.

Wild dogs

Ketamine -10mg/kg, and (Xylazine 2mg/kg, or Meditomedine at 0.1mg/kg)

 

Wild cats

Ketamine -10-20mg/kg, and Xylazine 2mg/kg.

Tigers/Lions

Ketamine 10-15mg/kg

Etorphine(M-99) 0.5mg/100kg BW, if tremors are exhibited , to be controlled by acepromazine.

Medetomidine at 0.03mg/kg and ketamine 2.5mg/kg.

Hippopotamus

Etorphine 4-8mg I/M and Xylazine 0.1mg/kg.

 

ANAESTHESIA OF LABORATORY ANIMALS

This module deals with

• Injectable Anesthesia
• Inhalant Anesthesia 
• Gas Delivery Systems
• Anesthetic Machine
• Preparation, Monitoring and Maintenance of normal physiology

Generally Rats, Rabbits Hamsters and Guniea pigs are used in lab.

Rats

Thiopental 25-50mg/kg I/V and 50mg/kg I/P.

Ketamine 50mg/kg I/V and 100mg/kg I/P.

Xylazine 2.5mg/kg I/M

Diazepam 5mg/kg I/P

Fentanyl+Droperidol(Neuroleptanalgesia) 0.001-0.01ml/gm of 10% Innovar-vet solution)

Inhalation of CO2 at 50-70% CO2 +Oxygen.

 

Rabbits:

Atropine 0.04-2mg/kg

Diazepam 5-10mg/kg

Thiopental 15-30mg/kg

Ketamine 20-60mg/kg

Propofol 1.5mg/kg.

Hamsters

Pentobarbital 70-80mg/kg

Ketamine 40-80mg/kg

Innovar-vet 0.15ml/100gm

Guniea pigs

Xylazine 5-40mg/kg

Diazepam 2.5-5mg/kg

Pentobarbital 15-40mg/kg

Ketamine 40mg/kg

INJECTABLE ANESTHESIA

·         Anesthetic induction using injectable anesthetics is fairly simple. It involves admininsistration of the drug and monitoring the depth of anesthesia.

·          Maintenance of injectable anesthesia can be through repeated bolus doses,typically, 1/2 of the original dose is given for repeat doses.

·         The most frequently used routes of administration in laboratory animals are intraperitoneal, intramuscular and intravenous.

·          

·          Intravenous(IV)

·          For large animals, the saphenous, cephalic or jugular veins are best. For rodents, the tail veins are best. For rabbits and swine, ear veins may be used.

·         Advantages - rapid delivery of drug, ability to titrate dose, irritating substances may be given IV

·          

·         Intramuscular(IM)

·         For small animals, the caudal thigh muscles. For larger animals, the lateral dorsal spinal muscles or the cranial or caudal thigh muscles may be used.

·          Advantages - Fairly rapid absorption, technique is simple

Intraperitoneal (IP)

·         The animal is usually restrained in dorsal recumbency. The drug may be injected anywhere in the caudal 2/3 of the abdomen. However, it is best to try to avoid the left side in rodents and rabbits because of the presence of the cecum.

·         Advantages - relatively large volumes may be injected (0.5 ml in mice, 2 ml in rats, etc.)

Subcutaneous (SQ)

·         Pinch an area of loose skin. Inject into the center of the "tent" created by pinching.

·         Disadvantages - Irritating substances cannot be given this way, absorption is slow

 

INHALANT ANESTHESIA

·         Anesthetic gases are irritating to eyes and nasal passages. Animals may resist as they begin to lose consciousness or they may stop breathing temporarily. For this reason induction using a mask or nose cone held over the animal's nose can only be performed on smaller or non-fractious animals. In smaller animals gas can be delivered into an induction chamber large enough to contain the entire animal. Induction via a nose cone or chamber requires delivery of the anesthetic gas at 2-3x MAC. Frequently an injectable anesthetic is used to induce anesthesia and the inhalation agent is used for maintenance.

·         Maintenance of inhalation anesthesia is normally accomplished by delivering approximately 1.2 MAC to an animal via a mask or nose cone, or directly into the lungs via an endotracheal tube. Intubation is recommended whevever possible, particularly when a procedure will be prolonged.

•  

Apparatus for rodent anesthesia

• Left: a non-re-breathing nose cone that can be used with a large animal anesthetic machine; Middle: a typical drop system closed anesthetic chamber; Right: a gas scavenging system that can be used with a drop system.

 

 

PREPARATION, MONITORING AND MAINTENANCE OF NORMAL PHYSIOLOGY

·         Normal physiologic functions such as body temperature, respiration and cardiovascular function must also be monitored and supported while the animal is anesthetized.

PREPARATION

·         Withhold food and water from large animals for 12 h prior to anesthesia and from small animals for 2 h to prevent regurgitation and aspiration. It is not necessary to withhold food and water from rodents prior to anesthesia. Prolonged food or water deprivation are distressful to animals and are rarely necessary.

·          Have all drugs and equipment ready

·         Have an assistant

·         Premedication with atropine or glycopyrrolate (anticholinergics) may reduce the respiratory tract secretions in some animals

·         Protect the eyes from drying out using an ophthalmic ointment.

·         Prevent bed sores in prolonged cases.

RESPIRATION

·          When an animal is in lateral recumbency the lung that is down is being compressed by the rest of the body. Likewise, animals in dorsal recumbency may experience compression of the diaphragm by abdominal viscera.

·         The airway may be compromised by regurgitated food or pharyngeal and tracheal secretions that normally would be removed by reflex swallowing or coughing.

·         There are several ways to monitor and support the ventilation of an anesthetized animal.

·         Intubate the trachea whenever possible. Intubation can be achieved on animals as small as a rat. This will prevent aspiration pneumonia and allow you to assist respiration if the animal stops breathing.

·          Assist respiration during the procedure. This can be done with a mechanical ventilator.

•  AMBU bag to the endotracheal tube or using an anesthetic machine's rebreathing bag will allow you to administer a deep breath every 2-5 min during the procedure.
• Monitor respiratory function throughout the procedure and recovery.

o    Monitor respiratory rate and depth

o    Monitor the color of the mucous membranes.A bluish color means the animal is not getting enough oxygen- ventilate!

o    Red-tinged foam present in the airway along with dyspnea (difficulty breathing) may indicate pulmonary edema. A diuretic like furosemide can be administered.

o    Sophisticated respiratory monitoring can be achieved by measuring blood gasses, or expired oxygen and carbon dioxide concentration or by use of a pulse oximeter

FLUID THERAPY

·         Fluid requirements are increased because: breathing dry, cold oxygen increases respiratory fluid loss; the animal has not received its normal fluid intake since it was fasted; fluid may be lost through hemorrhage or exposure of moist viscera to room air; many anesthetics are metabolized in the kidney.

• To minimize the effects of surgery and anesthesia on hydration:

o    Place an intravenous catheter whenever possible to provide access for fluids and medications

o    Supplement fluids, intravenously if possible; otherwise intraperitoneally or subcutaneously

§  Fluid should be supplemented at the rate of 5-10 ml/kg/hour during anesthesia

§  To replace blood loss with saline or lactated ringers, administer 3X the volume of blood lost by slow IV drip. Monitor the hematocrit. If it drops below 20%, whole blood replacement may be necessary.

·         Monitor cardiovascular function by monitoring one or more of the following:

o    Mucous membrane color and capillary refill time

o    Heart rate and rhythm - stethescope or esophageal stethoscope

o    Pulse rate and pressure - using your fingers

o    Blood pressure - arterial catheter or Doppler cuff required

o    ECG - If the animal has pale mucous membranes, the capillary refill time is greater than 2 seconds.

THERMOREGULATION

·         Animals frequently become hypothermic during anesthesia because of inhalation of cold gases, exposure of body cavities to the room air, and loss of normal thermoregulatory mechanisms and behaviors.

·         To thermoregulate your patient:

o    Monitor the body temperature While animal normals vary from species- to-species, in general, when body temperature drops below 99° F, an animal is considered hypothermic. Below 95-96° F an animal cannot regain normal body temperature without supplementation.

o    Prevent heat loss by insulating with a blanket

o    Prevent heat loss during gas anesthesia by utilizing low flow techniques that conserve heat

o    Supplement heat with a thermal blanket or with pre-warmed fluids

o    Treat hyperthermia by administering intravenous fluids or applying water to foot pads or exposed skin. Only use an ice bath as a last resort, as it may cause cardiovascular shock.

 

 

MONITORING ANESTHESIA

Monitoring anesthesia

• To monitor the depth of anesthesia, perform the following:
• Reflexes - these reflexes disappear as the animal becomes deeper in the following order:

§  Palpebral reflex - touching the eyelids causes blinking.

§  Toe pinch reflex - pinching the toe or foot web will cause a pain response.

§  Corneal reflex- touching the cornea of the eye with a tuft of cotton results in a blink. 

o    Muscle tone increases as the depth of anesthesia decreases.

 

 Monitor cardiopulmonary function and body temperature

·         As an animal becomes too deeply anesthetized, respiration and cardiac output decrease, resulting in poor blood oxygenation and tissue perfusion and decreased blood pressure and temperature..

Anesthetic Emergency Drugs	Dose (mg/kg)	Indications
Doxopram (Dopram)	1-5 IV (10x in farm animals)	Respiratory stimulant, for complete respiratory arrest only, use with CPR
Furosemide (Lasix)	2- IV, IM	For pulmonary edema.
Naloxone (Narcan)	0.04 IV	For reversal of narcotic sedation
Yohimbine	0.1-0.15 IV	Reversal of xylazine or detomidine sedation
Atropine	0.02-0.04 IV	For bradycardia
Epinephrine (1:1000)	0.1 ml/kg IV	For cardiac arrest only.
Lidocaine	2, IV	For  ventricular tachycardia.

Recovery

·         Monotoring and support must continue until the animal is completely recovered from anesthesia, to normal body temperature and all physiological indices are within normal limits.