Anesthetics and sedatives are routinely given to veterinary patients having surgery. Additionally, these drugs are often administered to pets needing certain procedures in which they need to lay still or where movement of the patient could be detrimental such as a CT scan, MRI or a biopsy. Anesthetics may be delivered by injection or by inhalation (of a gas by way of a tube in the trachea).

Today's veterinarian has many options to choose from, and these modern day drugs are generally considered safe for use in healthy animals. However, many of the commonly used anesthetic drugs and sedatives can have an affect on vital processes such as heart rate, breathing, and blood pressure. In addition, there are certain animal breeds that metabolize certain drugs differenty than others. An example is the sight hound (Greyhound, Whippet, etc.) which is better suited to be administered certain types of drugs versus others. Furthermore, some pets requiring anesthesia are not always "normal and healthy." As such, monitoring the patient under anesthesia is essential to ensuring his or her well-being and provides the veterinary team valuable information, the ability to quickly intervene on behalf of the patient, and helps to minimize risks associated with anesthesia.

Monitoring Vital Signs

Veterinarians have access to instruments and equipment capable of monitoring a variety of parameters in patients under anesthesia. These include:

  • Heart rate and rhythm
  • Blood pressure
  • Oxygen levels in the blood
  • Carbon dioxide levels in the blood stream
  • Body temperature
The "A-B-C's" of CPR (principals of ensuring Airway - Breathing - Circulation) are the same for patients under anesthesia. Patients under anesthesia can develop abnormalities in any of these parameters, and the information provided through monitoring can make a difference to the outcome of the procedure, and potentially affect whether a patient survives their anesthetic event. Real-time monitoring allows the veterinarian to make rapid decisions and take prompt action to correct any problem that arises - thus, minimizing the risks associated with anesthesia.
Blood Pressure
There are a few types of blood pressure monitors used by veterinarians in the hospital or clinic setting. During an anesthetic event, if a veterinarian notices an increase in blood pressure, they will assess to make sure that the level of anesthesia is sufficient, as this can sometimes indicate that the patient is "light" and needs slightly more anesthetic to prevent the patient from sensing any discomfort associated with the procedure. Conversely, if the blood pressure drops, the veterinarian may decide to decrease the amount of anesthetic being delivered to the patient, or increase the amount of intravenous fluids being administered, and in some instances, give medications to increase the blood pressure.  
There are several significant consequences to a drop in blood pressure including an interruption of oxygen delivery to vital organs such as the brain, kidney, and the heart. Prolonged hypotension (low blood pressure) can have significant implications to the well-being of the patient (animal or human). For example, multiple studies have shown that humans, who develop a drop in blood pressure (hypotension) during an anesthetic event, have up to a five-times increase in mortality (death) and two-times increase in the risk for stroke after their procedure.
Without a blood pressure monitor, the veterinarian simply does not have the information and cannot make the necessary and critical adjustments for the patient.
Heart Rate and Rhythm
Heart rate can be estimated by feeling a patient's pulse - the pulse rate is usually a good indicator of the heart rate. However, the rhythm of the heart's beating and pumping cannot be determined without an electrocardiogram or ECG. A continuous ECG monitor helps the veterinarian and anesthetist to monitor for arrhythmias or irregular heart beats. If changes in heart rate or rhythm are determined durning anesthesia, the veterinary team can take appropriate action to intervene.
Oxygen and Carbon Dioxide
Patients under anesthesia may experience changes in their breathing. One of the safeguards that veterinarians often take is to place a tube into the trachea (airway) to ensure a direct and immediate path for delivering oxygen to the lungs. In patients that receive inhalation (gas) anesthesia, this tube is always placed as it delivers the gas mixed with oxygen. Oxygen is critical for life, and even a brief deprivation can have life-threatening implications.

There are a few ways that the veterinary team can monitor the respirations or breathing in the patient, and there are various types of monitors that can track the blood oxygen and carbon dioxide levels to ensure that the patient is adequately ventilating (breathing oxygen in and exhaling carbon dioxide). A decrease in oxygen saturation or high levels of carbon dioxide can have significant consequences to a patient under anesthesia. Through monitoring, the veterinary team can take steps to intervene.
If Your Pet is Having a Procedure or Anesthesia
If your pet is having a procedure - whether it's a "routine" spay/neuter or a more complicated surgery - talk to your veterinarian about the anesthetic plan for your pet. An informed pet owner should ask questions about the type of anesthesia, pain management, and monitoring that the pet will receive. Some pet owners resort to "price shopping" when it comes to care for their pets - especially elective procedures such as a dentistry or spay or neuter. Keep in mind that the sophistication of care and monitoring of patients under anesthesia may account for the difference in fees quoted between veterinary hospitals. Veterinarians who provide high quality care in their hospital have invested in equipment and resources to ensure the best of care for their patients. This may be reflected in the fee estimates provided to pet owners.