This brief article is intended to clarify some of the misinformation veterinarians have seen and heard regarding the use of the nasogastric tube in the treatment of endurance horses suffering from metabolic problems. It is meant to be informative and to serve as a reminder of its usefulness.

The basics

The tubes can vary in specific design and composition, but all are flexible, about ten feet long and 1/2" to 5/8" in diameter (for adult horses). As the name implies, the tube is passed through the horse"s nasal passage into the esophagus ("food tube") and down into the stomach. Other names for the nasogastric tube include "Ng. tube," "stomach tube," "stomach pump," "nosetube" or just plain "tube."

The Ng. tube has been used by veterinarians for over a century to administer fluids and medications, to deworm horses ("tube worming"), to relieve obstructions from the pharynx and esophagus, and to decompress and relieve the stomach of excess gas and fluid.

Passage of the Ng. tube appears to be a relatively easy procedure when performed on a quiet and cooperative horse; excitement or pain can make it more challenging and restraint with a twitch or sedation may be required.

Indications for use

Specific situations indicating the use of a Ng. tube in an endurance horse include:

Fluid administration in a dehydrated horse, provided there is no reflux from the stomach and the gut is functioning, i.e., gut motility present. This can be a relatively quick way to administer one to two gallons of fluid, and electrolytes if needed. It can be repeated at 30 to 60 minute intervalsÑagain, provided there is no reflux (check frequently as conditions can change quickly) and that gut motility is present.

Relief of "choke" or esophageal obstruction. This is occasionally seen in compromised endurance horses (usually due to voracious eating combined with dehydration and/or electrolyte deficiency).

Colic. This is common in compromised endurance horses. Other articles will elaborate on the specific causes of colic in endurance horses but a generalized sequence of events are a decrease in gut motility due to blood shifting to muscle groups resulting in a slowed progression of intestinal contents through the gut and, if combined with dehydration, ileus (a condition where gut motility has shut down) or obstruction in the gut with subsequent pain and colic symptoms.

In severe cases fluid and intestinal contents build up and even back up into the stomach causing dilation of the stomach and this can result in significant pain, perhaps spontaneous reflux from the nostrils and ultimate stomach rupture. In this type of case, passing a nasogastric tube and relieving the pressure (reflux) can be a life-saving procedure.

It is important for riders and veterinarians to realize the significance of this. Rumors that passing a Ng. tube can cause stomach rupture are unfounded. If this were to occur it is more likely that the stomach was at the point of rupture at the time of the tubing. Therefore, early passing of a Ng. tube in a horse with significant colic pain is indicated to possibly relieve pressure and reflux.

Precautions and complications

I assure riders that all licensed veterinarians know how to pass a nasogastric tube and are familiar with the precautions to be taken and the potential complications which can occur when performing the procedure, e.g., we do this routinely when treating colic in our everyday practice settings. With this in mind I list them here for general awareness and review.

Precautions:-- Correct passage and location of the tube, i.e., passage into the stomach and not the lungs.

-- Visualization of the tube on the left side on neck as the tube is passed.

-- Feel of "resistance" as tube is passed through the esophagus.

-- Appreciation of passing through the cardiac sphincter muscle into the stomach.

-- Appreciation of the smell of stomach content in the tube.

-- "Shaking" the neck to make sure the tube is not "rattling" in the trachea.

-- Check for reflux.

-- It is best to make several attempts to get reflux before administering fluid into the stomach (consider motility).

-- If significant reflux occurs and if shipping the horse to a referral center, consider leaving the tube in place (taped or sutured in place). All endurance vets should have two to three Ng. tubes of different sizes with them at endurance rides.

-- Consider motility. If motility is absent consider not administering large volume fluids.

-- Avoid intense force when administering oral fluids. The fluid should flow readily through the pump.

Complications:

-- Misplacement of the tube into the lungs. This should not occur if the checks described above are followed. All veterinarians know this.

-- Nose bleeds may be unavoidable at times. In cold weather the mucous membranes of the nasal passages are quite sensitive and can become irritated when initially passing the tube.

-- Also, small amounts of dirt or grit in the nasal passage can result in some bleeding from the procedure. The blood can appear to be significant in amount but it always stops and is rarely a problem.

-- Gastric rupture is almost always due to an already severely compromised and dilated stomach, i.e., one that is near to rupturing at any moment. It can be avoided if a Ng. tube is passed early and reflux is relieved prior to the stomach becoming too dilated and stretched.

In conclusion

Passage of a nasogastric tube in the treatment of endurance horses with certain metabolic symptoms can be a life-saving procedure. Endurance veterinarians must be aware of the indications for its use as well as complications which can occur and use caution when passing the tube. Endurance riders should be aware that passing a nasogastric tube in a metabolically compromised horse can be a life-saving procedure and they should not decline to allow a veterinarian to perform the procedure when it is indicated.

A 1982 veterinary school graduate of UC Davis, Jamie Kerr has been vetting rides for nearly 20 years, including five years as head veterinarian at Tevis. He has served on the Veterinary Committee for 10 years. Dr. Kerr also rides, and currently has 3350 endurance and 155 LD miles. He lives and practices in the Petaluma/Santa Rosa area of Northern California.