Endotracheal intubation in pets

Arvind Sharma

Assistant Professor

Deptt. Of Veterinary Surgery & Radiology,DGCN COVAS, CSK HPKV, Palampur (H.P)

Introduction

• An Endotracheal tube is a device that is placed inside the trachea of an unconscious /anaesthetized patient usually attached to a breathing circuit

• used to administer oxygen and inhalant anaesthetics.

Uses of ET tube

• increase patient safety

• they maintain an open airway

• minimizes the likelihood of pulmonary aspiration of blood, stomach contents.

• facilitates administration of supplemental oxygen

• allows the anaesthetist to ventilate the patient when necessary.

Material & size of ET tube

• Endotracheal tubes come in a variety of sizes, lengths and types

• to accommodate the wide size variation of veterinary patients.

• made of red rubber, silicon rubber or polyvinyl chloride (PVC).

• Murphy tubes have a side hole called the Murphy eye at the beveled end

• permits airflow in the event of blockade of the tip.• scale of measurement of diameter of an endotracheal

tube is the internal diameter of the tube (ID). • Tubes for dogs and cats range in size from 3.0 to 14mm

ID.

Parts of ET tube

• Connector is attached to the breathing circuit of the anaesthetic machine or to ambu bag (AMBU-Assisted Manual Breathing Unit).

• Cuff is a balloon like part at the beveled patient end which when inflated, creates a seal between the tube and tracheal mucosa.

• This prevents the mixture of room air and anaesthetic gases

• prevents aspiration of liquid or solid materials around the tube.

• The cuff is connected by a small tube to the pilot balloon and a valve which is used to inflate the cuff.

• The pilot balloon allows the anaesthetist to monitor the cuff inflation.

Equipment needed for ET intubation

• Appropriate sized Endotracheal tubes

• Cotton bandage or IV tubing to secure tube

• A gauze sponge to grasp the tongue

• A syringe to inflate the cuff (12ml for small animals and 20ml for large animals)

• A good examination light

• Lidocaine spray or solution to control laryngospasms in cats.

Selection of ET tube

• Always prepare at least three tubes of different sizes so that you are prepared if your first choice does not fit the patient’s trachea.

• Most cats require 3 to 4.5mm tube. • The appropriate size for a dog is based on its body weight. • Prepare a 8 mm tube for a patient weighing 20 kg (9mm for a

Brachycephalic breed). • Increase or decrease size 0.5mm for each 2.5kg body weight under or over

20kg. In other words prepare a 7.0 mm tube for a 15 kg patient or 9 mm tube for a 25kg patient.

• The Endotracheal tube should ideally extend from the tip of the nose to the thoracic inlet.

• If inserted too far -supply one lung with oxygen and anesthetic. • If inserted only to the thoracic inlet - will increase mechanical dead space. • Either situation will predispose the patient to hypoventilation and hypoxia. • If it is too short, it may not be long enough to reach the trachea.

Preparing the tube

• Check tube for blockages, holes or other damage.

• Check to be sure that the connector is securely attached and check the cuff by inflating it.

• If intact, the cuff should remain inflated after detaching the syringe from the valve.

• The tube can be lubricated with Lidocaine jelly before placement or any sterile water soluble lubricant.

Intubation procedure• Proper restraint, positioning and visualization are critical to a successful intubation.

• Characterized by unconsciousness, lack of voluntary movement, sufficient muscle relaxation to allow the mouth to be held open and absent pedal and swallowing reflexes.

• Place the patient in sterna or lateral recumbency.

• Have an assistant grasp the maxilla behind the canine teeth, extend the neck and raise the head

• Pass a cotton bandage or IV tubing behind the canines on the upper jaw to open the jaw.

• Grasp the tongue with a gauze sponge and open the mouth fully by firmly pulling the tongue out and down

• Adjust the light so that you have good illumination of the larynx

• Use the tube or laryngoscope to gently displace the epiglottis ventrally or the soft palate dorsally until the glottis can be visualized.

• Gently insert the tube past the vocal folds using a rotating motion. never force the tube

• Check the tube to ensure that the it is in the appropriate distance and is oriented to match the natural curve of the trachea

• Secure the tube with cotton bandage or used IV tubing (over the nose for dolichocephalic dogs and behind the head for cats and brachycephalic dogs. Be sure the tie is secure enough not to slip but does not compress the tube.

• Inflate the cuff and check for leaks

• Ensure a patent airway by checking the position of the patient and tube.

Checking for proper placement• An Endotracheal tube can be easily misplaced in

oesophagus• Revisualize the larynx to confirm successful intubation• Feel for air movement from the tube connector as the

patient exhales• Palpate the neck. The only natural firm structure in the

neck is the trachea. • If the tube is properly placed, only one firm structure

should be palpable. Palpation of two firm structures (tube and the trachea) indicates placement of the tube inside the oesophagus.

• If the patient can vocalize (whine or cry), it is not in correct location

• Although a cough reflex during intubation is indicative of proper placement, not all patients exhibit this sign.

Cuff Inflation

• The cuff of the endotracheal tube must be gently inflated until a seal is formed between the trachea and the cuff.

• This will prevent leakage of anaesthetic gases and mixing with room air, which will be hazardous for the personnel.

• Avoid over inflation of the cuff which may lead to necrosis of tracheal mucosa and tracheal rupture in extreme cases.

Laryngospasms• Laryngospasm is a complication in which the glottis forcibly closes during

intubation. • This complication is most commonly encountered in cats. It is extremely difficult to

place a tube in a patient experiencing laryngospasms because the glottis closes as soon as it is touched and cannot be safely forced open.

• Laryngospasms can lead to hypoxia and cyanosis in severe cases• Apply 2% injectable Lidocaine via a syringe directly to the glottis before placement.

Wait 30-60 seconds for the Lidocaine to take effect before intubation attempt; 0.1ml is appropriate for cats; 1-2ml for dogs

• Be sure that the patient is adequately anaesthetized before attempting intubation because laryngospasms decrease with increasing depth of anaesthesia.

• Prepare carefully, wait for glottis to open before attempting placement and try to get the tube in the first time.

• Repeated attempts worsen laryngospasms• Do not force the tube. This can lead to severe and potentially life threatening

complications like tracheal rupture, pneumothorax and pneumomediastinum.

Thank You

Trilokinath Temple, Lahaul Valley, Himachal Pradesh