Exam 2: Ruminant Sedation and Anesthesia

what is important about ruminant saliva

• continuous secretion

• low surface tension compared to water promotes formation of foam

• source of upper airway obstruction under anethesia

what is relevant about the rumen

• fermentation even under anesthesia

• 30L of gas production in cattle

• capacity 115-150L in large , 15-18L in small

• bloating increases intra-abdominal pressure

how is regurgitation relevant to anesthesia

• rumen full of liquid that does not empty completely

• active or passive regurg

• risk of apsiration → reflex airway closure, bronchosplasm, destruction of type II pneumocytes and pulmonary capillary lining cells, pulmonary edema and hemorrhage

what are important notes about the ruminant respiratory system

• small tidal volume with high respiratory rate

• flatter and verticle diaphragm

• during recumbency abdominal viscera pushhes against diaphragm → decreases functional residual capacity, decreases lung ompliance, tidal volume, minute ventilation, increased V/Q mismatching, hypoxemia

what are important notes about ruminant CVS

• compression of vena cava during recumbency

• decreased venus return and decreased CO and BP

• most affected in dorsal recumbency

what are important considerations to make with large sized ruminants

• recumbency and positioning

• neuromyopathy, 10cm thick high density foam pad

• dorsal = balanced squarely with gluteal areas bearing equal weight, limbs flexed and relaxed

• lateral = automotive inner tube placed under elbow of dependent dorelimb and pulled anteriorly, front and hindlimbs elevated and paralelle to table, head and neck extended, protect eye

how long should ruminants be fasted

• adult large 24-48 hrs

• small 12-24hrs

• may not prevent regurg or bloating

• withhold water 12-24

what are your options for IV catheterization in ruminants

• jugular vein (14g adult cattle, 16-18g small)

• auricular vein in adult cattle 16-18g

• can hand restrain small ruminants, head gates and chutes large

how are ruminants intubated

• always recommended

• deep plane of anesthesia during intubation

• hand guided ± stylet guided

• difficult airway due to narrow and long oral cavity, thick tongue

how should small ruminants be intubated

• always recommended

• deep plane of anesthesia during intibation

• difficult airway

• long blade laryngoscope and stylet

how is acepromazine used in ruminants

• blockage of dopaminergic receptor in basal ganglia

• mild tranquilization/calming

• not commonly used

• 4-8 hrs duration

• no antagnost

• vasodilator

• may increase risk of regurge

• penile prolapse in bulls

• 0.01-0.05 mg/kg IV/Im

how are a2 agonists used in ruminants

• central and peripheral adrenoceptors

• sedation, analgesia, muscle relaxation

• dose depndent effect - standing sedation to recumbency and immobilization

how is xylazine described for ruminants

• more sensitive

• cattle and small ruminants 0.05-0.2mg/kg IV/IM

• brahman- use with caution 0.01

• sheep- activation of PIM = pulmonary edema and hypoxemia

• final trimester of pregnancy = premature parturition

how are A-2 antagonists used in ruminants

• shorten time to standing

• treatment of severe induced bradycardia

• minimize effects of overdose

• awareness of pain, vasodilation and excitement

• tolazoline 0.5-.5mg/kg IV

• atipamezole 0.04-0.2mg/kg IM/IV

how are benzodiazepines described in ruminants

• midazolam and diazepam

• GABAa receptor antagonist

• reliable sedatve and muscle relaxant

• co-induction with ketamine

• minimal CV side effects

• Midazolam = 0.1-0.5 IV, 0.2-1 IM

• diazepam = 0.1-0.5 IV

• antagonist s flumazenil

how is butorphanol described in ruminants

• opioid k-agonist u-antagonist

• not reliable sedatation on its own

• combine with other sedatives

• 0.02-0.1 IV

how is induction described

• sedation not always necessary

• ketamine, Guaifenesin, Telazol, propofol, alfazalone

how is ketamine described in ruminants

• NMDA receptor antagonist

• stimulates limbic system may cause dysphoria, hallucinations, excitement, tonic-clonic muscle activity

• stimulate CVS and may cause tachycardia, increaased cardiac output and BP

• most reflexes remain present but uncoordinated

• 2-5mg/kg IV

what drugs are used with ketamine for induction

• midazolam/diazepam = 10-15 minutes

• guaifenesin - induction or maintenance

• xylazine = 30 min

how is guaifenesin described for ruminants

• centrally acting muscle relaxant- internucial neurons in spinal cord and polysynaptic nerve endings

• 5% solution

• used with ketamine or ket +xylazine = triple dip 0.5-1

how is Tiletamine/zolazepam (telazol) described in rumnants

• similar to ket/midaz

• 45-60min duration

• 2-4mg/kg IV

• lyophilized powder

• minimal cardiovascular depression

• smooth recovery

• analgesia

how is anesthesia maintained in ruminants

• injectables (triple drip in cattle, propofol in small)

• iso or sevo

how is monitoring done in large ruminants

• palpebral reflex = surgical plane of anesthesia = sluggish or just absent, deep = absent

• corneal reflex = surgical= present, deep = absent

• postionon of eye= surgical = ventromedial, deep = central

how are small ruminants monitored

• reflexes are same as large

• position of eyeball not reliable as it does not change

how should vitals be monitored

• hr, ECG, BP invasive

• resp rate, ETCO2, SpO2

• temperature

what cardiovascular support should be provided

• hypotension is major cardiovascular complication and is implicated in postanesthetic myopathy-neuropathy

• treatment = adjust anensthetic depth, fluids, calcium borogluconate, ephendrine, dobutamine

how are ruminants recovered

• no sedation required

• external recumbency with elevated head

• keep ET tube in place and cuff inflated until laryngeal reflex is normalized

• extubate when swallowing and chewing

• reversals if needed