Chemical Immobilization Equipment: Hand Injection and Pole Syringes

There are several different methods for the delivery of immobilizing agents (drugs) to free-ranging and captive wild animals. Among these are hand held syringes, pole syringes and projected darts or syringes (remote delivery systems). The decision as to which method is most appropriate usually rests with the attending veterinarian, wildlife manager, research scientist or animal control officer.

In the United States, the Food and Drug Administration (FDA) determines what drugs can be used on certain animals. The FDA also requires a registration certificate for those using controlled substances; these can be obtained through the US Drug Enforcement Agency (DEA). These medications also must be dispensed through an established and valid veterinarian/client/patient relationship as defined by the Animal Medicinal Drug Use Clarification Act of 1994.¹

Chemical Immobilization: Direct Administration Devices

Two types of devices for the direct administration of injectable drugs to animals are:

• Syringes (hand-held)
• Pole Syringes (push poles or jab sticks)

When using hand held syringes on free-ranging wild animals, the animal is typically captured and restrained using a net. In a zoo setting, this may be practical with smaller or acclimatized animals, or with larger animals that have been pre-sedated with drugs placed in bait.^2,3 Pole syringes essentially extend the range for the injection of immobilizing drugs. These are practical in the case of larger, more dangerous animals in a zoo setting, or with free-ranging animals of the same species that have been captured in nets or culvert traps.

Hand-Held Syringes

A syringe consists of a barrel and a plunger, and can be used for direct hand injection of drugs into an animal. The barrel holds the medication and the plunger pushes the medication out of the syringe. Syringes are designed to hold volumes of fluid that vary from 0.5 ml to 60 ml.

There are two basic syringe types

• Friction-tip (or slip-tip)
• Luer-lock

Friction-tip (slip-tip) syringes rely on friction to maintain a needle that is pushed onto the tip of the barrel. With these syringes, there is a risk that the needle can separate from the syringe during forced movement of the plunger if the needle hub is not securely pushed onto the tip of the syringe barrel. This can result in injection failure, with a portion of the medication being delivered onto the animal’s fur or skin, or on the skin of the handler.¹

Luer-lock syringes have screw threads in the tip of the syringe barrel that allow the hub of the needle to be twisted onto the syringe barrel point, forming a secure connection. With these syringes, the needle is less likely to separate from the syringe, making injection failure far less likely.¹ Thus, it is highly recommended that all injections made by hand syringe be done with Luer-lock syringes.

Needles come in a variety of lengths and diameters (gauges), with smaller numbers representing larger needle diameters. Smaller diameter needles (20, 22, or 25 gauge) should be used to draw medication out of vials to avoid leakage, whereas larger diameter needles (14, 16, or 18 gauge) should be used to inject medication into animals in order to reduce fluid resistance and minimize induction time. It is important to remember that routes of administration (intramuscular, intravenous, intraperitoneal, subcutaneous and oral) affect the rate of drug absorption.¹

Pole Syringes

Most animals that are not accustomed to direct human interaction will move away or struggle when attempts are made to handle them, and this includes the administration of drugs. Secure and rapid injection techniques are required to administer the full volume of medication into an animal and avoid broken or bent needles or syringes during the injection.^1,2 Thus, in cases where this is unlikely or unattainable via hand injection, pole syringes are often employed.

A pole syringe is basically a syringe mechanism contained within or mounted on the end of an extendable pole. These are an essential component of all capture kits. Pole syringes come in a variety of types, each with varying mechanisms of action and safety features.¹ Pole syringes are available from a variety of manufacturers and come in various lengths. They may be used for direct injection of drugs into wild animals in traps, transport containers or handling facilities. They can also be used to deliver supplemental drugs in sedated animals, from a distance or behind a barrier.

Interested in learning more about safe capture? The San Diego Zoo now offers courses in safe capture techniques and best practices. Learn reliable, safe, and effective techniques for the species you work with and the scenarios you encounter!