Anesthetic Monitoring – What Should You Look For?

When a patient undergoes anesthesia for any procedure, their immediate and future organ health are directly affected by the drugs given to them and by how well the doctors adjust for any physiological changes during the procedure. Pain control from the anesthetic protocol is equally as important, as studies have proven that pain increases healing time.

The minimum standard for monitoring a patient under anesthesia as set out by the College of Veterinarians of Ontario is a stethoscope to measure heart rate and at least one device to measure respiration or oxygen saturation (to determine whether the patient is breathing adequately)[1]. Technically, a veterinarian can act as both surgeon and anesthesiologist; they may direct orders to an untrained individual if assistance is required.

The minimum standard is not good enough. 

So how do you determine how safe your clinic is with regard to general anaesthesia?

Firstly, it is important to investigate whether the clinic treats each patient as if it were their own treasured pet under anesthesia.  Does each pet receive a detailed, individual anesthetic plan mapped out by their doctor based on their species, age, breed, and the procedure they are undergoing?  Ask for examples. Do any of the doctors have specializations or certifications in areas of anaesthesia or pain management?

Second, during the procedure, does each patient have one Registered Veterinary Technician directly responsible for anesthetic monitoring? This technician should be with your pet from induction (initiation of anesthesia) right through to their full recovery. Their job is to pay attention to the smallest details, and to make sure that the veterinarian is apprised of the pet’s physiological status and pain control throughout the procedure.

Finally, what equipment has the clinic invested in to help monitor physiological parameters during anaesthesia? The medical profession is learning that even if just one of these parameters is left unmonitored and becomes outside the normal range for a prolonged period of time, doctors could be setting up their patients for organ damage that is not apparent until many years down the road.  Monitoring is crucial to patient safety and comfort. Below is a list of vital monitoring equipment that you should ask about if you are considering having your pet put under anaesthesia for a procedure. An easy way to start this conversation is to ask for a tour of the clinic and its equipment, then bring this sheet with you to discuss.

1.     Monitoring Heart Rate and Rhythm

ECGWhat: Heart rate and rhythm are ideally monitored by an electrocardiogram, often displayed on a portable laptop screen. An electrocardiogram detects and amplifies tiny electrical changes on the skin that are caused when the heart muscle “fires” electrical impulses during each heart-beat. It produces a graph of electrical ‘firing’ from the heart, as well as displays the heart-rate of the patient.

How: This is hooked up to the patient by means of either small conductible clips on the limbs, or through an esophageal stethoscope. Which method used often depends on the procedure.  A technician should also double check the heart rate readings with their stethoscope to ensure accuracy.

Importance: The graph produced by this monitoring system helps to detect changes in rhythm that can be caused by anesthesia or an underlying condition. The veterinarian can adjust drugs or anesthesia accordingly. In the rare case of an anesthetic cardiac arrest, the electrocardiogram is crucial in assessing what life-saving measures are necessary. Finally, the heart rate itself provides a wealth of information, including assessing anesthetic depth (making sure the patient is adequately ‘asleep’), drug reactions, and pain.

2.     Monitoring Respiratory Rate and Oxygen Saturation

pulseoxWhat: Respiratory rate (breaths taken per minute by the patient) and the level of oxygen dissolved in the blood stream are monitored by a ‘pulse-oximeter’. This small clip is placed between the toes of the patient, or sometimes on their tongue.

How: This paddle-like clip illuminates the skin and measures changes in light absorption. This determines how much oxygen is being carried by the red blood cells of the patient. This parameter is also displayed on our portable laptop screen.

Importance: Lowered oxygen saturation can be a result of inadequate breathing or other underlying conditions preventing adequate ventilation. Ultimately, if the tissues are not getting

enough oxygen during anesthesia, the anaesthesiologist will ‘breathe for the patient’ to ensure every organ is receiving enough oxygen and/or adjust the anesthesia.

3.     Monitoring Carbon Dioxide

What: Monitoring oxygen in the bloodstream is often not enough to ensure the patient is ventilating correctly. The anaesthesiologist also must make sure they are exhaling enough carbon dioxide, and not having it buildup in the bloodstream.

How: A device called a ‘capnographer’ can be attached to the patient’s breathing tube. It measures carbon dioxide exhaled. Certain procedures lend themselves to this type of monitoring better than others; this is up to the anaesthesiologist to decide.dvmsol

Importance: Increased carbon dioxide levels can change the rhythm of the heart, alter blood flow to the brain, and potentially cause death. This is especially important to consider in patients with airway disease (such as asthma), overweight animals, and extremely small patients who may have difficulty exhaling air into the tube circuitry of the anesthetic machine. By measuring carbon dioxide levels, the anaesthesiologist can make anesthesia adjustments well before any problems arise.

4.     Monitoring Blood Pressure

What:  Blood pressure drives oxygen-delivering blood through vessels to organs and tissue beds of the body. Heart rate and anesthetic drugs directly affect blood pressure.

bpHow: Ideally a non-invasive blood pressure monitor is hooked up to the pet at all times. It is an inflated cuff around a limb, which can be programmed to take readings at regular intervals.  In this way, changes in blood pressure can be determined quickly and accurately. Alternatively, some clinics may use a technician to manually assess blood pressure at timed intervals using a “Doppler”. Additionally, you can ask if the clinic has the option of using a second type of unit to confirm any blood pressure measurements in question (for example, a ‘high-definition oscillometric’ unit).

Importance:  Low blood pressure results in decreased oxygen delivery, resulting in the death of important cells and organ damage. Health professionals worry most about the kidney and the brain. Because lowered blood pressure is a common side effect of many anesthetic drugs, monitoring these values under anesthesia is crucial.

Ask what options the clinic has if blood pressure becomes of concern during the procedure. Most clinics should be able to increase fluid rate and/or change the amount of anesthetic agent delivered. If you have a pet with an underlying condition prior to anesthesia (such as kidney disease), ask if the clinic is capable of constant rate infusions of blood pressure medications (such as ‘dobutamine’); this would be a pre-emptive measure to ensure blood pressure is maintained.

5.     IV Catheter and Fluids

IVEvery patient undergoing any length of anesthesia should have an intravenous (IV) catheter placed prior to anesthesia. This provides direct and rapid access to the patient’s venous system for drug administration in case of emergency. Additionally, fluids are given through this IV catheter to maintain blood pressure (as discussed above) and to keep the animal hydrated during surgery. Extra pain management drugs may also be incorporated into these fluids. No human anaesthesiologist would ever consider putting a patient under general anaesthesia without an IV catheter.

6.     Temperature

What: Core body temperature is reduced by anesthesia. This is especially true in long procedures and with smaller patients. Temperature can be taken with just a thermometer. However, ask if the clinic has invested in either a rectal probe or an esophageal stethoscope for a continuous reading of temperature. This way trends can be monitored and warmth added even if there is a drop in temperature by 0.1 degrees.

How:  It is much easier and more beneficial to the patient to prevent a drop in temperature, rather than to try and warmingwarm them up after a drop has occurred. To this end, attention to temperature should start when the patient has their premedication prior to putting them under anesthesia. Ask the clinic what strategies they have to keep their patients warm. Effective strategies include warm oat bags in their kennel whilst their sedative and analgesic combination takes effect, and then a constant source of heat during the procedure. A ‘Bair Hugger’ or ‘Hot Dog Conductive Warming Blanket’ at all times throughout the procedure are both very effective warming devices, especially if coupled with warm oat bags if required.

Importance: Decreased body temperature is associated with prolonged recovery and an increase in post-surgical infections. It adds incredible stress to the body; stress that is very preventable through proper monitoring and protocol.

7.     Pain

What: There are variable degrees of pain associated with different types of procedures. Pain perception is also very individual – some of our pets are more sensitive than others.

How:  Pain management starts with strong pain medication such as an opioid prior to the procedure – a proven method of reducing post-operative pain. When appropriate, during the procedure local anesthetic blocks should be used to ‘numb’ the surgical site for up to 6 hours. A Registered Veterinary Technician then should not only monitors depth of anesthesia and all of the above-discussed physiological parameters, but also use clues such as heart rate to adjust for any unanticipated pain response.  Additional pain control drugs may be added to the animal’s fluids to control for pain during and after the procedure. Once the pet is awake, the doctor should choose from an array of pain medications both for in-hospital and at-home management. Ask what the clinic if sending pain medication home is standard.

Additionally, it can be helpful for clinics to assign a ‘pain score’ for each pet at regular intervals during their in-hospital stay to trend their comfort. Ask the clinic if this is part of their post-operative protocol.

Importance:  Multi-modal pain management is most effective and best medicine. Pain delays healing and reduces life quality, and so every single patient undergoing anesthesia should have a ‘pain plan’ built into their protocol by their doctor.

In Summary

Your pet is a beloved family member. It is worth taking the time to assess whether a clinic meets not just the minimum standard for an anesthetic procedure, but whether it follows protocols and uses technology similar to those in human anaesthesia to ensure safety and comfort.


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