Equine Anesthetic Issues Flashcards
Are anticholinergics (atropine, glycopyrrolate) used as preanesthetic drugs for horses?
No
What do atropine and glycopyrrolate treat?
Severe bradycardia
Decrease GI motility, gas distention, colic
What is acepromazine (tranquilizer) not recommended in? Why?
Stallions
Abnormal erection of penis, tenderness, pain
What can diazepam and midazolam (tranquilizers) cause?
Ataxia
Muscle weakness
Recumbency
What do sedatives (xylazine, detomidine, dexmedetomidine) cause?
Profound sedation Analgesia Muscle relaxation Bradycardia Hypertension Hypotension
When can narcotic analgesics be used as preanesthetic drugs?
Only after sedation
What do preanesthetic drugs for horses do?
Decrease induction doses
Calming effect, less stress
Provide analgesia
Combined with local techniques for standing anesthesia
What are induction considerations?
Horse must be restrained Premedication (xylazine +/- butorphanol) Large IV catheter Draw up more induction drug (ketamine: 200-400 mg total dose) Rapid induction: ketamine + midazolam
What IV technique is preferred for maintenance of general anesthesia?
CRI
What is triple drip GKX used for maintenance of general anesthesia?
Xylazine as pred med 15 minutes before
Guaifenesin: 1 L of 5%
Ketamine: 1 mg/ml
Xylazine: 0.5 mg/ml
What is the dose of the induction agent for maintenance of general anesthesia?
1 ml/kg IV
What is the dose for maintenance of general anesthesia?
2.2 ml/kg/hr IV
How long is recovery after 1 hour of anesthesia?
20-25 minutes
What are techniques for inhalation anesthesia?
Imapairment of ventilation and oxygenation
Inhalation anesthetics undergo minimal metabolism
Steady plane of anesthesia
Positive pressure ventilation
After premeds, induction, and intubation:
High O2 flow for 15 minutes and then 5 L/min for maintenance
Start IV fluids
Monitoring
What causes hypoventilation in horses?
Increased PaCO2 (>40 mmHg) due to reduced minute ventilation
What causes hypoxemia in horses?
Decreased PaO2 (<60 mmHg), probably due to V/Q mismatch
What is the treatment for hypoventilation?
Mechanical ventilation
What is the treatment for hypoxemia?
100% O2 + adequate BP +/- beta agonists (albuterol)
What are treatments of hypotension?
Reduce concentration of inhalation anesthetic
Correct dehydration/hypovolemia preoperatively with IV fluids or blood
Inotropes and vasopressors (appropriate fluid volume before):
Ephiderine (12-25 mg)
Dobutamine (1-5 μg/kg/min)
Dopamine (1-10 μg/kg/min)
Calcium gluconate (0.1-0.3 mEq/kg)
What can develop from anesthesia after the horse is standing or immediately?
Myopathy/neuropathy
What causes myopathy/neuropathy after anesthesia?
Poor perfusion of muslces
What is the treatment/prevention for myopathy/neuropathy?
Maintain MAP >70 mmHg
Appropriate padding
Adequate positioning on surgery table
