In this lecture, participants will be invited to interact with the speaker and discuss the anesthetic and analgesic management for a variety of patients and situations. There will be a “bit of everything” related to feline anesthesia and unique challenges in this species. The discussion will go from anesthesia in healthy cats undergoing routine procedure such as ovariohysterectomy and dentistry but also those in critical condition with urethral obstruction and lower urinary tract disease, and gastrointestinal foreign body. Some life-saving therapies and stabilization of the patient will be presented (e.g., treatment of hyperkalemia and acidemia; fluid resuscitation). The lecture will explore novel concepts and techniques in feline anesthesia and pain management with a practical and interactive approach including protocols with dosage regimens. Treatment of perioperative pain relief and considerations on the use of analgesics in cats with chronic pain will be discussed. Controversial topics will be broken down using current literature and evidence.
The following cases should be discussed during the lecture
1. Anesthetic and analgesic management of cats undergoing ovariohysterectomy.
2. Anesthetic and analgesic management of cats undergoing dental procedures.
In these two situations, the choice of anesthetics and special pharmacological considerations for these agents will be presented. Local anesthetic blocks for dentistry, the use of injectables protocols including videos will be demonstrated.
3. Anesthetic and analgesic management of cats with urethral obstruction.
4. Anesthetic and analgesic management of cats with gastrointestinal foreign body.
In these two situations, emphasis will be given to patient stabilization such as in hyperkalemia (Box 1) and undergoing celiotomy (Box 2).
5. The analgesic management of cats with osteoarthritis. We will explore the multifactorial cause of osteoarthritis, chronic pain assessment and treatment including therapy with NSAIDs.
Box 1—Patient Stabilization in Cats with Hyperkalemia
A list of problems is presented. Cats with urethral obstruction have reduced glomerular filtration rate, hypothermia, hyperkalemia, acidemia and circulatory collapse with weak peripheral pulses.
An electrocardiogram (ECG) identifies bradycardia and signs of hyperkalemia; it includes an increased T wave amplitude, decreased R wave amplitude, ST segment depression, decreased P wave amplitude, prolonged PR, QRS and QT intervals and not uncommonly loss of P wave with possible ventricular arrhythmias.
Venous catheterization is mandatory for fluid and electrolyte administration such as 10% calcium gluconate, dextrose, sodium bicarbonate, among others. Acidemia is partially induced by potassium ions moving extracellularly in exchange for hydrogen ions which are buffered intracellularly. Metabolic disturbances will lead to hypovolemia and cardiovascular depression since the resting membrane potential is raised in hyperkalemia, and cardiac automaticity, conductivity and contractility are decreased.
Rapid fluid resuscitation is required especially if poor perfusion and severe dehydration are present in the absence of cardiac disease. A bolus of balanced isotonic crystalloid fluid such as saline 0.9% is administered at 45–60 mL/kg/h while relief of obstruction relief. Cats with a serum potassium concentration greater than 6 mEq/L should not be anesthetized until hyperkalemia is treated. Warming techniques will prevent and treat hypothermia.
A sacro-coccygeal epidural block has been recently described to facilitate urethral catheterization in cats with urethral obstruction. The technique is performed under aseptic conditions and produces anesthesia of the perineal area, penis, urethra, colon and anus. Preservative-free lidocaine 2% (0.1–0.2 mL/kg) is injected for this block. Relaxation of tail and perineal region is normally observed.
Box 2—Special Considerations for Cats with Urethral Obstruction
Emergency abdominal exploratory surgery is commonly required due to intestinal obstructions (foreign body, intussusception, neoplasias, megacolon, etc.), GI ulceration, uroabdomen, GI biopsies, etc. Some complications include fluid losses, proliferation of intestinal bacteria and secondary intestinal inflammation, GI perforation, peritonitis, systemic inflammatory response, severe hypotension, hypovolemia and shock. Clinical findings are variable, but tachycardia is observed in hypovolemic patients.
The list of problems includes hyper- or hypothermia, electrolyte imbalances and acid-base abnormalities. Hypochloremia, hypokalemia, hypoglycemia and hyperlactatemia are not uncommon, but again fluid imbalance will vary with condition (vomiting versus diarrhea, dehydration, hypovolemia, septic versus non-septic). Dehydration with cardiovascular collapse including hypovolemia, hypotension, hypoproteinemia requires aggressive fluid therapy.
Severe abdominal pain is treated with opioid and ketamine infusions since NSAIDs are contra-indicated. The intraperitoneal administration of bupivacaine is recommended at the end of the surgery and it provides postoperative analgesia for up to 8 hours.
Regurgitation followed by aspiration pneumonia can occur after induction of anesthesia. Positioning for induction should take this issue in consideration. Suction should be available, and a stomach tube can be used to empty GI contents.