Inducing Anaesthesia

Introduction

Induction of anaesthesia can be performed using either an injectable agent or an inhalation agent. It is most commonly performed after a premedication has been administered and had time to take effect, but this is not always necessary. Endotracheal intubation also occurs at this stage after the animal has been induced and is an appropriate anaesthetic depth.

Premedication

Premedication is often given to an animal prior to an anaesthetic procedure. In some cases, however, it is not necessary or possible to premedicate the patient due to it's current status or underlying medical conditions. The advantages of premedication are that they reduce the require dose of induction agent and most will have a sedative effect to calm the patient helping to ensure a smooth induction.

Equipment

Before any patient is induced it is vitally important to have the appropriate and necessary equipment ready and prepared in case of an emergency. As well as monitoring equipment, it is important to have endotracheal tubes, laryngeoscope, and oxygen (often via an anaesthetic machine) ready as well as crash drugs, if available, easily accessible.

Intravenous Catheterisation

Most commonly a patient receives an induction agent that is given intravenously as this route often gives the quickest induction. Many patients will also be receiving fluids during their procedure which will also require placement of a catheter. It is therefore recommended that an intravenous (IV) catheter is placed in all patients undergoing an anesthetic procedure. This also means that clinicans have intravenous access in the face of an emergency also. In small animal patients, a catheter is usually placed in the cephalic vein if it is not within the surgical field, or the saphaneous vein may be used. In horses, a jugular catheter is placed.

Induction Environment

It is important that the environment a patient is in at time of induction is quiet with little going on around. This is to help ensure a smooth induction. Other considerations include keeping cats and dogs separate to prevent stressing out patients, and no banging or clattering in the background at induction.

Induction Agents

Induction can be performed using either injectable agents or inhalation agents. If an injectable agent is to be used, it should be drawn up before the patient is brought through for induction and it is recommended that an extra syringe is drawn up in case the calculated dose is not effective, or intubation is difficult and the patient begins to rouse before it is placed on an maintenance agent.