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64 Cards in this Set
- Front
- Back
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Hypothermia effects
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Significant MAC reduction
Bradycardia unresponsive to anticholinergics Spontaneous ventricular fibrillation (<92F) Hypoventilation and slowed elimination of volatile anesthetics slowed metabolism of drugs & prolonged recovery Increased metabolic demand Increased incidence of post-op infection |
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Essential components of general anesthesia
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Produce irreversible unconsciousness
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Managing a barbiturate overdose
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Support ventilation
Monitor cardiopulmonary function IV fluid therapy IV bicarbonate can speed recovery by favoring elimination (for prolonged overdose) Doxapram can be dangerous! (deleterious stress) |
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Narcotic antagonist
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naloxone
Duration of action shorter than some opioids; may result in renarcotization |
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Doxapram
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Respiratory stimulant that may reverse effects of depressants
Not to replace positive pressure ventilation Not for barbiturates |
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Nitrous oxide
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Delivery with too little oxygen is dangerous
Not prevented by fail-safe mechanisms in modern machines. |
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Improper cuff inflation
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Obstruction
Tracheal injury Aspiration pneumonitis |
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Causes of hypoventilation
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Anesthetic overdose
Secondary to: -Inadequate perfusion of CNS respiratory centers -Electrolyte imbalances -Muscle relaxant drugs -Thoracic injury |
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Causes of hyperventilation
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Inadequate anesthetic depth
Carbon dioxide accumulation (exhausted absorber, improper gas connection) |
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Which drugs may cause panting
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Narcotics
Also hyperthermia |
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Causes of pallor
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Compensatory response to light OR deep anesthesia
Reduced cardiac output due to anesthetic depression Increased sympathetic tone due to pain |
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Causes of cyanosis
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Rarely occurs
-Must have adequate levels of hemoglobin in non-oxygenated state Need to administer oxygen! |
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Causes of vagal bradycardia
How to treat? |
Difficult intubations
Deep abdominal surgical procedures Intraocular surgeries Surgeries of the neck or thorax Atropine or glyco may prevent, but not much after vagal effects become evident |
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Causes of non-vagal bradycardia
How to treat? |
Excessive anesthetic depth
Hypoxia Hypothermia Atropine and find possible causes |
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Management of hypotension
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Reduction of anesthetics!
Fluid administration |
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causes of hypotension
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Decreased cardiac output
Increased capacitance of vasculature (vasodilation) Inadequate blood volume Vasodilation from anesthetic drugs -Acepromazine -Volatiles Most anesthetics are also cardiac depressants |
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Tachycardia-definition
Direct effects |
HR above 180/min in dogs and 200/min in cats
Decreased efficiency and increased workload |
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Two types of tachycardia
Which is more serious? |
Supra-ventricular
Ventricular-more serious |
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Causes of supra-ventricular tachycardia
Consequences? Treatment? |
Fear, pain, inadequate depth, pre-anesthetic excitement, Compensatory for hypotension
Decreased coronary artery bloodflow and increased myocardial workload Fluid therapy and adjustment of anesthetic plane |
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Causes of ventricular tachycardia
Treatment? |
Irritated, diseased, or hypoxic myocardium
Dogs-IV lidocaine bolus-1,2,3cc's Cats-Propanolol is drug of coice; also lidocaine |
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Causes of delayed recovery
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Hypothermia
Inadequate fluid support Reduced metabolism or clearance of drugs Debilitation-stress of anesthesia or surgical trauma Hypoxic episode |
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Relative overdose
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Too much for that patient at that time
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Absolute overdose
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Miscalculation, etc.
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Problems with anticholinergic overdose
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Tachycardia-big problem in patients with heart disease
Increased myocardial workload and oxygen requirement Atropine prolongs barbiturate anesthesia Fatal cardiac dysrhythmias |
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Which drug is contraindicated in aggressive patients?
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Acepromazine
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Flumazenil reverses which drug?
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Benzodiazepines (diazepam)
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Naloxone or butorphanol?
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Both opioid antagonists; Butorphanol usually a better choice
-Preserves analgesia at kappa receptors -Naloxone risks renarcotization -Naloxone can cause pain or stress |
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Results of perivascular barbiturate injection
Therapy? |
Swelling at injection site
Pain at injection site Failure to induce anesthesia Necrosis and sloughing of skin Infiltrate generously with lidocaine (no epinephrine) and saline Hot pack/hydrotherapy +/- steroids, DMSO |
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Prevention of regurgitation or regurgitation/aspiration
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Tracheal intubation
check pH, lavage and suction, carafate suspension Metacloprimide Famotidine |
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Risk factors for regurgitation or regurgitation/aspiration
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Long duration
Pressure/position High dose opioids |
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All anesthetics are...
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Respiratory depressants
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Definition of bradycardia
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Dogs <65bpm
Cats <80bpm Horses <35bpm |
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Things to avoid for thermal support
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Electric heating pads
Hot water bottles Water filled gloves |
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Use to prevent hypothermia
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Hot dogs-dispersed heat heating blankets
Circulating warm water blankets Forced warm air heating blankets -More effective than warm water blankets -Can also be used to cool hyperthermic patients |
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Reasons for hypothermia (very common)
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Preparation of surgical site
Contact with cool surfaces Breathing of dry anesthetic gases Evaporation from airways and surgical field |
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Consequences of hypothermia
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Above 92F: Increased oxygen and energy requirements during recovery
Below 92F: Delayed recovery, reduced tissue perfusion, increased morbidity and mortality |
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Cardiac massage rate during CPCR
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90-120/minute
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Breathing rate during CPCR
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8-12 breaths per minute
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When is thoracotomy warranted?
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Almost never
-Impossible to maintain chest compressions -Possible laceration of lung tissue or myocardium -Poor results, traumatic |
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What may make you think CPCR is working?
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Pulse wave (pulsoximeter)
Hemoglobin saturation (pulsoximeter) Generation of CO2 (capnometer)- very good sign |
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What drugs may be helpful in CPCR?
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MgSO4 (100mg/kg over 5-10 min)
Atropine for ventricular or complete asystole |
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Indications for standing restraint in horses
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Standing surgery
-Ovariectomy, sinuses, Laceration repair Diagnostics -Radiography, Endoscopy |
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Characteristics of an ideal agent for standing sedation
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Small Volume
Water Soluble Non-irritant to tissues No Pain on injection Rapid Onset of Action Non-toxic Absence of Adverse Side Effects Compatible with other agents |
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Responses of a neurolept drug
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Inhibition of motor activity
Antagonism of apomorphine-induced vomiting Antagonism of amphetamine-induced arousal |
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Classes of neurolept drugs
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Butyrophenones (Azaperone)
Phenothiazines (Acepromazine) |
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Ketamine given alone produces what?
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Cataleptic state
-Loss of orthostatic reflexes -Appears paralyzed by motor and sensory failure |
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Drugs that cause problems perivascularly
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Thiopental
Guaifenesin Maybe xylazine (recurrent laryngeal nerve) Any drug at high concentration |
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Which drugs can't be used IM for standing sedation?
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Xylazine
Romifidine (Too high volume to be given IM) |
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Use of anticholinergics in standing sedation
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Rarely indicated
Usually following alpha-2 administration Prefer glycopyrrolate; Atropine can cause ileus |
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Things to consider in foals
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Try not to separate mare and foal
Very young foals can be sedated in lateral recumbency Can give same drugs as adults, but may need higher dose (30-50%) -In sick neonates, don't give alpha-2's Avoid drugs with prolonged effects; prone to hypothermia and hypoglycemia Older, undisciplined foals can be a problem |
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Local anesthetics in horses
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Only used to provide posterior epidural anesthesia (perineal sx, etc.)
Give 6-10mL Or CRI |
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Anesthesia in pregnant mares; alpha-2's? opioids?
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Should try to avoid if possible
Alpha-2 should be avoided in last trimester as they can affect uterine contraction. Opioids should not be given periparturient b/c of respiratory depressant effect on foals. If given, foal may be given naloxone. |
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Define windup and how to prevent it
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Once a painful stimulus starts, the dorsal horn of the spinal becomes hyperexcitable --> hyperalgesia
Prevent initial impulse from reaching the cord by using spinal block or local nerve block. Aminister NSAIDs (phenylbutazone, flunixin) preoperatively and post-op for a few days |
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Site of epidural injection in the horse
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Between the first and second coccygeal space
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Consequence of injecting too much lidocaine epidural
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May move forward and block L4-6, which are femoral nerve roots. Will cause horse to be weak or recumbent
Keep horse from moving and support hindquarters |
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What animals require larger doses of alpha-2's
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Fractious horses
Ponies Mules Donkeys |
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What are the shortest and longest acting alpha-2s
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Shortest- Xylazine
Longest duration-Romifidine |
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Compare diazepam and midazolam
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Midazolam has greater sedative effects, is water soluble, and has a shorter duration of action compared to diazepam.
Midazolam used for shorter surgeries |
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Compare duration of action of commonly used benzodiazepines
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Shortest to longest:
Midazolam < Diazepam < Zolazepam |
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Compare inhalational and injectable anesthetics in horses
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Injectables have wider therapeutic index and generally result in better recovery
With inhalational, may want to sedate horse once during recovery |
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How would you prevent radial nerve damage in a laterally recumbent horse?
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Pull the bottom leg forward
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How would you prevent facial nerve damage in an anesthetized horse?
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Halter buckles
Remove halter Proper padding under head |
