by Veterinary Practice News Editors | May 30, 2012 12:35 pm
A recent white paper published by AAHA is dedicated to the art of anesthesia. The guidelines “are not meant to establish a universal anesthetic plan or legal standard of care,” explain the authors,* but they are an excellent review of common practices in 2012.
Full disclosure: What follows is not a summary of the article, but the second part of our review of a few great points made by the authors. Click here to read Part 1.
“Increases in the liver enzymes of an otherwise healthy patient are not an absolute reason to avoid anesthesia,” the authors write. With severe liver conditions, dextrose supplementation can fight hypoglycemia and fresh frozen plasma may be required with hypoproteinemia.
Anesthetic drugs metabolized by the liver may lead to delayed recovery, so reversible drugs may be a better choice, such as opioids and alpha-2 agonists.
Acepromazine is often avoided in “seizure patients.” Yet, the authors write, “There is no evidence to show that ‘ace’ increases the risk of seizures in epileptic patients or patients with other seizure disorders.”
“Indiscriminant use of anticholinergic drugs […] as part of a premedication protocol is controversial,” the authors write.
Proponents like the protection against opioid-induced bradycardia, as well as vagal bradycardia, for example during ocular surgery. In addition, brachycephalic dogs may benefit from anticholinergics: “higher resting vagal tone [makes] these dogs more prone to developing bradycardia.”
Opponents consider that atropine and glycopyrrolate cause tachycardia, which increases the heart’s oxygen needs, and which many lead to myocardial hypoxemia.
Another controversy: Should we use an anticholinergic with alpha-2 agonists to fight bradycardia and improve cardiac output? As stated above, increased myocardial work may lead to myocardial hypoxemia. The authors conclude that “use of anticholinergics should be based on individual patient risk factors and monitored parameters, such as heart rate and blood pressure.”
The authors provide a chart with “things to do” while preparing for anesthesia. They include:
• Checking the entire anesthesia system: CO2 absorbent freshness, oxygen level, anesthetic gas level
• Choosing the correct size bag and a few endotracheal tubes
• Having a laryngoscope available
• Testing the cuff of the endotracheal tube
• Monitoring equipment
Whenever you consider performing anesthesia, be prepared for any emergency situation. This includes being prepared for tracheal suction, having a well-supplied and up-to-date crash cart nearby as well as either a chart of emergency drug doses or pre-calculated doses for your particular patient.
Every patient should have a written anesthetic log of everything pertaining to the anesthesia episode: ASA status, drugs, dosages and route administered, vitals, various events (IV catheter placement and location, intubation, surgery start, surgery end, recovery, extubation, etc.). Record patient vitals every 5-10 minutes.
IV catheters serve at least four purposes:
• administering IV fluids
• avoiding perivascular administration of drugs
• fighting hypovolemia (secondary to vasodilation or hemorrhage) with crystalloids or colloids
• quickly accessing a vein if you need to inject emergency drugs
As long as it doesn’t stress out the patient unnecessarily, preoxygenation is beneficial to lower the risk of hypoxia during induction. This is especially helpful in patients who already need oxygen supplementation or if you anticipate that intubation might be difficult.
How far should the endotracheal (ET) tube be inserted? “The distal tip of the tube [should] lie midway between the larynx and the thoracic inlet,” write the authors.
Which diameter should we choose? For the sake of minimizing airflow resistance, we should pick “the largest diameter ET tube that will easily fit through the arytenoid cartilages without damaging them.
Do lubricate the cuff of the tube to help inserting it and to reduce the risk of aspiration. For more information, refer to our December 2011 “Surgical Insights” column.
Do inflate the cuff just enough to create a seal. This will prevent anesthesia gas leakage and will allow positive pressure ventilation if needed.
Don’t overinflate the cuff of the ET tube.
Don’t rotate a patient without disconnecting the ET tube from the anesthesia breathing circuit.
Both incidents may cause a tracheal tear, a common cause of liability claims.
Another common liability complaint is related to thermal burns, often related to heat sources not intended for the purpose of warming up a patient. Accepted warming devices include IV fluid warmers, feet covering such as bubble wrap, warm-water or warm air blankets.
The authors remind us that most anesthesia-related deaths do not occur during anesthesia, but during recovery. The most critical period is the first three hours following surgery.
Indeed, 47 percent of canine and 60 percent of feline deaths occur in the post-op period. Close monitoring and heat support of these patients is critical.
For more information on this important topic, refer to our Feb. 1, 2010 “Cutting Edge” blog entitled “Anesthesia: It Ain’t Over Till It’s Over.”
The authors suggest two excellent, yet often forgotten tips:
• Reapply eye ointment during the recovery period, especially when an anticholinergic was administered.
• Express the bladder to improve the patient’s comfort.
A patient’s pain level should be assessed periodically and treated as needed. A quiet environment is preferable.
The authors suggest assessing four criteria before deciding to send patients home: They should be “awake, aware, warm and comfortable.”
This excellent article, published last fall, provides many more practical tips than we can share in this column. To read AAHA's article in its entirety, click here.
* R. Bednarski et al. "AAHA Anethesia Guidelines for Dogs and Cats." JAAHA 2011, Vol. 47, p. 377-385
Dr. Zeltzman is a mobile, board-certified surgeon near Allentown, Pa. He is the co-author of “Walk a Hound, Lose a Pound: How You and Your Dog Can Lose Weight, Stay Fit, and Have Fun Together.”
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