Anesthesia Monitoring and Safety

If your horse ever needs surgery, how does Kleider Veterinary Services provide your horse with safer anesthesia?

Monitoring blood pressure of a horse is one of the most important steps in assessing depth of anesthesia as well as circulatory status. Why don't' vets routinely take blood pressure readings on your horse like your doctor does?

Historically it always has been a difficult value to obtain since the horse's skin is thicker than a humans and therefore the normal technique of listening to the rush of blood with a stethoscope is not possible as it is in people.

Listening to that rush of blood with a stethoscope is possible with a Doppler ultrasound machine which is the technology we have used until now. This has its drawbacks in that it must be positioned on the tail which is one of the few places that an artery is superficial enough to allow application of a cuff necessary to compress the artery.

Being an indirect technique means less precision. Direct blood pressure monitoring equipment to the rescue!

We now routinely catheterize an artery and attach this arterial line to produce a constant digital readout of systolic, diastolic or mean arterial pressure. The same unit gives us an ECG tracing and a body temperature from a rectal monitor.

What does all this mean to your horse? Monitoring allows us to maintain a higher blood pressure resulting in safer anesthesia, better recoveries and fewer complications.

Other Monitoring

A pulse oximeter measures oxygenation, a capnograph measures carbon dioxide values and the level of anaesthetic gas the horse breaths in and out are constantly monitored by a gas analyzer off the endotracheal tube. This lets us know a) if the anaesthetic depth is too light or too deep and b) allows us to decide if your horse needs to go on the respirator!

These are anesthetic monitoring devices. The picture above shows the device with a horse in the foreground. It is measuring the carbon dioxide level, the isoflurane (anesthetic) level and also measures the oxygen level from a clip on the tongue

Routine Use of Local Anaesthesia - No Pain, All Gain!

Horses feel pain even when asleep under general anaesthetic. Our goal is for them to be lightly anaesthetized- just enough for them to be immobilized. A lightly anaesthetized horse can still be stimulated by painful procedures. A common solution is to deepen the plane of anaesthesia but this results in a lowered blood pressure.

Other techniques are safer and include routine use of local anesthetic in joints or along nerves of horses undergoing surgery. This technique is used for all our arthroscopies and we have found that this "insurance" of no pain results in a smoother surgical plane and no pain on recovery. Use of Banamine and other pain relieving agents prior to surgery compliments this protocol.

This device measures the direct blood pressure of the horse and gives a continuous ECG tracing.	Indirect blood pressure monitoring is also used with a Dynamap Critikon system attached to a cuff around the tail	Istat blood gas monitor

Indirect blood pressure monitoring is also used with a Dynamap Critikon system attached to a cuff around the tail. This backup system is useful for short procedures or until an arterial line can be established. Since it is placed at the tail it also allows us to continuously monitor rectal temperatures as noted by the probes in the picture. This is especially important in foals which are more susceptible to hypothermia (low body temps). Besides hypothermia certain adult horses can have a condition called malignant hyperthermia (high temps) with gas anesthesia being a triggering factor.

Use of Isoflurane vs. Halothane

The gas anaesthetic that we use is isoflurane. This is the same gas anaesthetic used on people and has replaced halothane in the majority of hospitals. Because Horses seem to recover quickly and we have not noticed any cardiac related problems that had previously been documented with Halothane.

Foal Anaesthesia

For foal anaesthesia we try to decrease the stress level as much as possible by allowing "Mom" to attend surgery as long as it doesn't jeopardise sterile technique.

Frequently we use an injectable anesthetic in young foals which is the same drug used in people. A downsized anesthetic system with smaller tubing, ventilator and soda lime canister makes anesthetizing a small foal safer because of less resistance while breathing.