4 ways to avoid anesthesia complications
You can reduce your patients' potential for problems by staying clear of these common pitfalls.
Inducing anesthesia in your veterinary patients can be challenging. Complications may arise, and we can make mistakes. But you can decrease the likelihood for error by taking steps to ensure you and your colleagues eschew practices that can lead to blunders. Taking the time to consider the following smart practices hopefully will help you offer better patient care. (Also see the Related Article "4 anesthesia mistakes you might not know you're making" below)
1. Watch for mismanagement of endotracheal tubes.
Failure to measure the tube length correctly can cause inadequate anesthesia and oxygen delivery, bronchial intubation, and atelectasis, which is the collapsing of alveoli. It can also cause dead space, which is when the tube extends out too far, causing an inadequate exchange of gases. This inadequate exchange can lead to a buildup of arterial carbon dioxide (hypercapnia), which causes respiratory acidosis, thus greatly increasing the possibility for other complications.
Cuff inflation also can be done incorrectly. Overinflation can cause tracheal necrosis and trauma, while underinflation may expose team members to anesthetic gas and can cause inadequate anesthesia delivery. What's more, the potential for aspiration is increased if the patient vomits, regurgitates, has an abundance of saliva, or is undergoing a dental procedure in which its mouth is continuously being rinsed.
Because of these risks, a technician should inflate the cuff and check that there are no leaks before continuing with the anesthetic procedure. This process can entail slowly inflating the cuff while listening for an airway leak at the level of the animal's mouth and administering a positive pressure breath. It can be helpful to ensure the chest rises with inflation to indicate tracheal intubation. Proper endotracheal tube cuff inflation is achieved when the sound of air escaping is no longer heard at a pressure of 20 mm Hg. Since relaxation can cause air to leak around the cuff, the technician should check the cuff after the patient goes deeper into anesthesia.
2. Be sure to use the correct equations for fluid administration, reservoir bag size, and oxygen flow rates.
Some technicians give fluids at too low a rate, eyeball the patient to determine reservoir bag size, or administer oxygen at the same rate regardless of the patient's size. Oxygen is a cooling gas, and administration at too high a flow rate can cause hypothermia more rapidly than administration at the proper flow rate. Also, the patient can get more inhalant anesthesia than intended as it is going in with the oxygen.
An acceptable flow rate for oxygen is 30 ml/kg/min on a rebreathing system. For example, a 44-lb (20-kg) dog only needs oxygen at 0.6 L/kg/min (20 kg x 30 ml = 600 ml). The flow rate must be at a minimum of 500 ml/min on a nonrebreathing system. If the patient is obese or has inhibited ventilation, the flow rate can be increased to 60 ml/kg/min for the first hour of anesthesia.
A commonly accepted surgical fluid rate for a patient that has no malady that would affect its ability to tolerate fluids is 5 ml/lb/hr (10 ml/kg/hr). This rate can be increased or reduced in response to blood pressure measurements. The reservoir bag size is usually 30 ml/lb while always rounding up, so a 50-lb dog would require a 2-L bag (1.5 L rounded up). Proper bag size affects anesthesia, oxygen delivery, and the removal of waste gases (carbon dioxide).
3. Don't approach monitoring with a one-size-fits-all mindset.
The body uses many mechanisms to remain in balance, so if one parameter is abnormal, another area will usually try to compensate. Although a patient can hyperventilate if it is at an inadequate plane of anesthesia ("getting light"), another cause of hyperventilation is hypercapnia, or an increase in arterial carbon dioxide, which is brought about when the patient is not ventilating adequately. Since the commonly assumed cause of hyperventilation is inadequate anesthesia, some technicians just increase the inhalant anesthesia in response. But, if the patient is hypercapnic, the increased inhalant will bring the patient into a deeper plane of anesthesia, worsening the hypercapnia.
Tachycardia also can indicate a light patient, or it can be a sign of hypotension, dehydration, or hypoxia since the body can increase its heart rate in order to increase cardiac output and tissue perfusion. Tachycardia also can be a result of the administration of medications such as ketamine and atropine or glycopyrrolate. Again, increasing the anesthetic depth can have detrimental effects if the patient is already in a sufficient anesthetic plane and suffering negative effects. In addition to tachycardia, watching for responses to surgical stimulation such as increased respiratory rate, active reflexes, or spontaneous movement along with vital signs can lead the technician to the proper treatment.
Regardless of condition, the patient must be continually monitored and reassessed throughout the procedure. Technicians should watch and be aware whenever vitals (including temperature) are out of the normal range. They should also evaluate pulse quality, mucous membrane color, and capillary refill time while checking the pulse oximeter reading and the patient's blood pressure. The proper course of action for complications is best determined when the technician and veterinarian look at the patient as a whole throughout the anesthetic procedure.
4. Work as a team.
Every member of the veterinary team has the same goal: Provide patients with the best care possible. Knowing as much as you can about the patient's medical history is imperative to accomplishing this goal. Clients' fears are eased when they see those caring for their pets showing familiarity with the patients. Every team member should feel comfortable voicing concerns or asking questions relating to a patient's care. For more specifics about every team member's role in successful anesthesia, visit http://dvm360.com/AnesthesiaTeam.
Jennifer Keefe, CVT, VTS (ECC, anesthesia), has 14 years' experience working in veterinary emergency and critical care in southern New Hampshire and eastern Massachusetts.