Chapter 3: Advanced Anesthesia for Small Animals 1 CE Hour
Expiration Date : January 20, 2025
PRE-OPERATIVE DRUGS
Learning objectives After completing this course, the learner will be able to: Discuss the use of many of the common pre-anesthetic drugs. What is preanesthetic medication? Preanesthetic medication is the term used to indicate the drugs that are given prior to the induction of general anesthesia. What are the uses of preanesthetic medication? ● To relieve patient’s anxiety and apprehension, fear, and resistance to anesthesia: These medications will help make the animal less stressed and easier for the anesthesiologist to handle. ● Contribute to peri-operative analgesia. Commonly used preanesthetic drugs ATROPINE Mechanism of action This drug blocks the muscarinic cholinergic receptors resulting in blocking parasympathetic nervous system effects. Clinical uses ● Increase heart rate: used to counteract bradycardia from other anesthetic drugs. ● Decrease gut motility. ● Decreases salivation and prevents excessive salivation and airway secretions. ● Dilates pupils. ● Relaxes bronchi. Atropine does cross the blood-brain barrier and, with high dosages, can cause CNS symptoms such as excitement and twitching. ACEPROMAZINE Mechanism of action Dopamine antagonist at dopamine receptor DA2 in the CNS and Alpha 1 adrenergic receptor antagonist. Acepromazine has a dose-dependent duration and can be very prolonged, usually last 4 to 6 hours. This drug is metabolized by the liver. Effects ● Causes variable sedation. If it does not cause wanted effects at a lower dosage, higher dosages will not be effective. This is not a reliable drug for aggressive animals. ● Combining with opioids will create a synergistic response. Decrease the dosage of anesthetic needed. ● Anti-emetic. ● Causes peripheral vasodilation and hypotension. Clinical uses ● This is a very predictable and usually exceptionally reliable. ● Calming effect – at a low dosage will decrease fear. Used to treat dogs for fireworks and thunderstorm phobia. ● Typical used as a pre-anesthetic medication in combination with opioids.
Explain the effects that the drug will cause the patient. Predict any side effects that you may see when using a certain drug.
● To counteract unwanted side effects of certain anesthesia drugs. ● To help smooth induction and recovery from general anesthesia. ● To reduce the dosage of general anesthetic needed for induction.
Cardiopulmonary effects ● Hypotension. ● Variable heart rate effects. ● Decreases PCV and platelet count. ● No effect on heart contractility or output. ● Increases cardiac arrhythmogenic. ● No significant effect on respiration. ● Other important factors.
Acepromazine will cause a drop in body temperature. An overdosage of this drug can cause extrapyramidal signs such as tremors. The long duration of the drug provides a much smoother anesthetic recovery. Contraindications Acepromazine should not be used in patients with: ● Shock. ● Splenic tumors. ● Thrombocytopenic or anemic animals. ● Impaired liver function. BENZODIAZEPINE The two main drugs used from this class in small animals are Diazepam and Midazolam. Mechanism of action All Benzodiazepines act at specific sites on the GABA receptors. GABA is the major inhibitory neurotransmitter in the brain. CNS effects Benzodiazepines have anti-anxiety and tranquilizing effects. This class of drug can also be used as anti-convulsant and cause reliable muscle relaxation. In dogs and cats, they are not as effective as tranquilizers alone. Cardiovascular and respiratory effects ● Minimal cardiovascular depression. ● No change in heart rate, cardiac output, or arterial blood pressure. ● Mild dose-related respiratory depression. ● These are considered a safe drug and commonly used in many anesthetic protocols for critical patients.
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Book Code: VFL1524
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