Is Anesthesia Safe?

Authored by: Laura McLain Madsen DVM

Veterinarians anesthetize animals on a daily basis.  At least once per week in any clinic, a pet owner expresses concern about anesthesia: Is it safe?  Will my pet survive the procedure?

Modern anesthesia is very safe.  The risk of a pet dying under anesthesia is less than 1%.  The rare patients that are lost under anesthesia are generally emergency surgeries, when the patient's condition is extremely critical.  The risk of a pet dying under anesthesia while undergoing a routine spay, neuter, dental or mass removal  is extremely low, but this risk can be affected by the anesthetic drugs used and the monitoring of the patient.

 Can you imagine an anesthesiologist in a human hospital using ether or chloroform in the 21st century?  Of course not.  But, unfortunately (and surprisingly), there are no standards of care for veterinary anesthesia, and some clinics are still using out-of-date techniques.  Here is a list of questions to ask your veterinarian the next time your pet is scheduled for an anesthetic event:

1) Is pre-anesthetic blood work run?  All patients, not just the old or sick, should have basic pre-anesthetic blood tests performed checking the blood sugar, kidney values, and red blood cell count.  Many animals will require more extensive pre-anesthetic blood work.  Even in animals under one year old, blood work will occasionally detect abnormalities that could affect anesthesia.

2) Are intravenous fluids administered during anesthesia?  Many drugs used for general anesthesia tend to cause blood pressure to decrease.  Intravenous fluids will combat this decrease.  In addition, if there are any adverse reactions under anesthesia, an intravenous catheter allows immediate administration of emergency drugs.

3) Is the pet's body temperature maintained during and after anesthesia?  All animals,  especially cats and small dogs, lose a lot of body heat under anesthesia.  The resulting hypothermia can slow the anesthetic recovery.  Anesthetized pets should be placed on a recirculating warm water pad and/or under a warm air blanket.  Conventional heating pads are risky because they can cause burns.

4) Is the pet intubated, and what anesthetic gas is used? 
Intubation means that the patient has an endotracheal tube placed through the mouth and into the trachea, through which gas anesthetic is administered.  The endotracheal tube allows controlled respirations if the patient is not breathing well on his or her own, and prevents accidental inhalation of stomach contents if the pet vomits under anesthesia.  Virtually every surgical procedure done in dogs and cats requires intubation and gas anesthesia.  The modern gas anesthetics are halothane, isoflurane and sevoflurane.  Methoxyflurane is out-of-date.

a. What pain control is used?  Surgery hurts!  It doesn't matter if the patient is a human, a dog, or a guinea pig.  Analgesia is the relief of pain, and in modern anesthetic protocols we strive for pre-emptive analgesia (blocking the pain pathways before the painful procedure starts), and balanced anesthesia (trying to block the pain pathways from as many directions as possible). 

5) What monitoring techniques are used?  It is critical to monitor the patient's vitals while under anesthesia to ensure that the respiratory and cardiovascular systems are functioning well, and to ensure that the patient is not under too lightly or too deeply.  Most important is that someone besides the surgeon (who is occupied) is monitoring the heart rate, respiratory rate, and anesthetic depth.

Additional commonly used monitoring techniques include:

• An electrocardiogram (EKG) to monitor the heart rhythm for arrhythmias.
• A pulse oximeter to monitor the percentage oxygenation of the blood, which should be close to 100%.
• A machine to monitor the blood pressure.
• A machine (apnea monitor or capnograph) to monitor the respiratory rate and carbon dioxide level.

Another concern many pet owners have is the cost of anesthesia: Why is it so expensive?  Why does Dr. X charge $300 for a dental while Dr. Y down the street only charges $100?  As you can see, modern anesthesia involves a lot of equipment and expertise, and this unfortunately costs money.  Cutting corners by not intubating patients, not keeping patients warm, or skimping on pain medications and monitoring can save money, but the price is decreased comfort and safety for your pet.

by Laura McLain Madsen, DVM

Copyright 2004 - 2005 by the Veterinary Information Network, Inc. All rights reserved.