MK2 Kit Dosages & Usages

Performing general anesthesia in the field can be impractical as well as stressful for wildlife managers, veterinarians and their support staff; even under ideal conditions, it can cause morbidity and mortality in animals.¹ Thus, immobilization protocols that employ heavy sedation with analgesia are largely favored over general anesthesia in many wildlife applications.

According to Thurmon and Short, anesthesia is defined as the loss of sensation to the entire or any part of the body.² General anesthesia involves central nervous system depression resulting in the loss of consciousness and sensation. Characteristics of general anesthesia include

1) complete unconsciousness
2) analgesia
3) muscle relaxation
4) absence of reflex responses

Anesthesia should not be mistaken for simple immobilization and recovery, without regard for the importance of monitoring and maintaining a stable patient during the procedure.³ However, immobilization and recovery involving heavier sedation (often being the preferred method in the field) can produce far less stress, risk and a more expeditious procedure overall. According to Chinnadurai et. al., “a veterinarian lacking field experience may incline towards over-instrumentation when expeditious completion of a brief procedure would optimize patient safety. Anesthesia also must be a rapidly reversible process, which presents special challenges when working with free-ranging wildlife for which residual sedation or renarcotization can result in injury or death after release. Short-acting or reversible agents (or both) are therefore preferred for field anesthesia.”³

With the current technology and variety of medications available today, it is now possible to design appropriate anesthetic and analgesic protocols for nearly any field situation. With careful planning and adequate communication, field team members will be able to smoothly execute most immobilization protocols, as well as anticipate and prepare for potential complications.

Applications and Field Considerations

Apart from highly-invasive surgical procedures (which would likely require the immobilization and transport of an animal for surgery under general anesthesia), the chemical immobilization of wildlife is generally required for tagging, collaring, blood collection, various medical assessments, semen collection and artificial insemination.

In general, the two broad categories of anesthetic agents are inhalant and injectable agents. Injectable anesthetics are further differentiated as reversible and nonreversible. Injectable agents are typically administered by an intravenous (IV) or intramuscular (IM) route, and some drugs are appropriate for either route (such as ketamine) while others can only be administered intravenously (such as propofol).³

Problems inherent in field anesthesia can include environmental obstacles (such as rough terrain, forests, swamps etc.) which can pose problems if the animal becomes difficult to track or if the anesthesia takes effect in an area where the animal is hard to reach. Lack of supportive equipment can also be problematic in that physiological parameters which are easily monitored using general anesthesia in a clinic are simply not available in the field, increasing the risk of complications. Weather conditions can also play a role in the difficulty (or lack thereof) in the field: Many anesthetic agents impair an animal’s ability to thermoregulate, also increasing the risk of complications.

Finally, since most large animals in the field are sedated via remote delivery, injection sites factor into the success or failure of procedures. The drug injection site can influence absorption of a drug and the time to induction.

Amongst seasoned veterinarians and their teams, protocols for the chemical immobilization of large wildlife have been refined and streamlined to the degree that barring drastic unforeseen circumstances, the only variable remaining is a reliable and efficacious drug regimen. Considering the risks posed to humans in working with large animals in the field (as well as risks to the animals themselves), one of the top-tier concerns of wildlife veterinarians and veterinary pharmacists has been the development and refinement of efficacious drugs and drug combinations specifically for large animals being anesthetized in the field.

The MK2 Kit for the Field

The MK2 Kit by NexGen Pharmaceuticals is a premixed formulation developed to provide veterinarians and wildlife handlers with a field-tested immobilization anesthesia option that can be effectively used to immobilize a broad range of exotic animal species. This formulation consists of medetomidine (10mg/ml), which provides superior pain relief and muscle relaxation to other compounds employing α-2 adrenergic agonists, and ketamine HCL (200 mg/ml), which supplies an effective paralytic. In combination, the two provide safe, smooth induction times and excellent recovery results.

MK2 was originally developed by NexGen with the assistance of exotics industry veterinarians and Dennis Smith (Ranch Manager of Schmidt Ranch in Neiderwald, Texas) as a superior solution for anesthetizing larger animals in a more efficient manner. The MK2 Kit includes the MK2 formulation with accompanying reversal agent (and a manufacturer discount for purchasing the two in combination).

Primarily used for Whitetail Deer, MK2 is twice the strength of NexGen’s MK formulation, thus, the kit allows for use of smaller dart. It can be used for larger Whitetail bucks, for capture, relocation and transport, general assessments (routine doctoring) and for the artificial insemination (AI) of does.

For those who are new to utilizing MK to manage their exotic animals, it is important to understand that the level of anesthesia being administered with medetomidine/ketamine in the MK2 Kit is a deep sedation, not to be confused with other sedations that are moderate.

Routes of Administration and Dosages

The preferred route for the administration of an immobilizing drug by remote delivery is via intramuscular injection. The aim is to hit the animal in a specifically-selected site, causing injection into vascular tissue and facilitating rapid absorption of the drug. Not all areas of an animal's body are equally well-suited for injection by remote delivery; thus, the injection site should be carefully chosen.

The neck is generally a suitable site for large animals with muscular necks. Care should be taken to avoid hitting the jugular vein, the upper neck and the head. The ideal injection site is the trapezius muscle mass at the upper base of the neck. This injection site is suitable for species such as elk, moose, buffalo, bear, the equids and larger antelopes, rhinoceros, hippopotamus and elephant (if the ears can be avoided). Animals with slender necks, such as gazelle, gerenuk, giraffe and impala should not be darted in this area.

The shoulder is a suitable injection site in many larger species. This region is well-muscled, presenting a flat, perpendicular target. It is surrounded by relatively resilient areas and presents a fair-sized target in animals that are robust enough to be darted with remote delivery equipment.

To prevent the needle from becoming embedded in cartilage, the upper end of the scapula should be avoided. In sensitive species, the sight and smell of a dart in the shoulder may cause panic and flight. Some carnivores will destroy the dart by pulling it out with their teeth. The shoulder is not a suitable injection site for smaller species, due to their lesser size and limited muscle mass.

Recommended dosages for large animal sedation with MK2 are as follows:

• White Tail doe/sm buck – 0.5-1.0cc
• White Tail large buck – 1-1.5cc
• Bison cow/small bull – 1cc
• Bison Bull – 1.25cc
• Fallow deer doe – 0.5-1cc
• Fallow deer buck – 1-1.5cc

For reversal dosages, please consult MK2 Kit reversals documentation.