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132 Cards in this Set
- Front
- Back
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CNS effects of dissociative anesthetics |
seizures, increased cerebral blood flow/intracranial pressure, emergence delirium/hallucinations |
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CV effects of dissociative anesthetics |
indirect: increase catecholamines --> tachycardia (predominate unless depleted) direct: myocardial depressant |
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resp effects of dissociative anesthetics |
bronchodilation, maintenance of pharyngeal/laryngeal reflexes |
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MOA of etomidate |
enhances the affinity of inhibitory NT GABA at the GABA-A receptor |
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how is etomidate metabolized? |
hydrolyzed by hepatic microsomal enzymes and plasma esterases |
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main clinical use of etomidate |
used in patients w/ cardiac disease, or in patients that require stable CV function due to other concurrent diseases |
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effects of propylene glycol in etomidate |
hemolysis |
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endocrine effects of etomidate |
adrenocortical suppression |
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neurosteroid induction agent |
alfaxalone |
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MOA of alfaxalone |
enhances GABA-mediated neurodepression (...think propofol, etomidate, barbiturates) |
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How is alfaxalone metabolized/excreted? |
metabolized by hepatic glucuronidases - metabolized more slowly in cats |
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important side effects of alfaxalone |
dose-dependent cardioresp depression |
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MOA of barbiturates |
decreases rate of dissociation of GABA from GABA-A receptor directly opens Cl- channel --> hyperpolarization |
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CNS effects of barbiturates |
vasoconstriction, decreased cerebral blood flow --> decrease intracranial pressure decreased cerebral metabolic oxygen requirement |
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CV effects of barbiturates |
minimal decreases in BP w/ healthy patients; profound hypotension in hypovolemic pts myocardial depression, arrhythmias |
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resp effects of barbiturates
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resp depression |
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effects of administering barbiturates outside the vein |
sloughing of the tissue, pain |
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pros and cons of inhalant inductions |
pros: aggressive animals that can't be handled, pets w/ severe liver disease, used in some wildlife/exotics cons: can't get rapid control of airway, stressful for animal, creates excitement phase w/o premed --> lose control of airway --> vomit/regurg |
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opioid inductions common in which patients... |
critically ill, highly unstable |
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TIVA |
- total intravenous anesthesia - method of inducing and maintaining general anesthesia exclusively by IV administered drugs |
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advantages of TIVA |
- better recovery profile - portable delivery system (i.e. syringe pump) - less operating room pollution (no waste gases) |
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disadvantages of TIVA |
- cost prohibitive - availability of suitable drugs and delivery systems - can't reliably monitor plasma concentration of drugs like ET inhalant agent monitoring |
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uses of TIVA |
- GA - day surgery - supplement to locoregional anesthetic - sedation for diagnostic/therapeutic procedures |
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disadvantages of repeat bolus TIVA |
peaks and troughs in drug concentration - can see toxic effects or under-dosing |
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disadvantages of CRI TIVA |
delay to peak effect need loading dose decrease in concentration at transition from loading dose to maintenance (due to drug redistribution) |
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target controlled infusion |
aims to achieve predicted target blood concentration based on population pharmacokinetic studies actual concentrations achieved may be greater/less than selected target, but provides closest approximation of blood concentration of drug for a patient |
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propofol in TIVA |
- rapidly metabolized w/ minimal accumulation - smooth recovery and less CV depression than isoflurane - has been co-infused w/: fentanyl, morphine, remifentanil, dexmed, ketamine... - can see abnormal motor activity in dogs, Heinz body anemia in cats |
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fentanyl CRI |
single injection can be used for short-duration analgesia during anesthesia |
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nicotinic synapses |
pre-synaptic cell: motor neuron post-synaptic cell: muscle cell ACh synthesized/released by nerve cell binds to nicotinic receptors on muscle cell. conformation change allows Na+ ions into muscle cell --> membrane depolarization --> muscle contraction ACh in cleft is hydrolyzed by AChE. Na+ channel closes. |
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MOA of non-depolarizing neuromuscular blockers |
competitive antagonists bind to nicotinic ACh receptors and prevent ACh from interacting w/ the receptor |
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reversal of nondepolarizing NM blockers |
are not hydrolyzed by AChE - redistribute, metabolized and excreted can be reversed by increasing the amount of ACh at the synapse... giving an AChE inhibitor ACETYLCHOLINE CAN HAVE FATAL EFFECTS ON HEART; give w/ atropine/glycopyrrolate to prevent bradycardia |
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edrophonium, neostigmine |
AChE inhibitors, reverse non-depolarizing neuromuscular blockers |
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depolarizing neuromuscular blockers |
nicotinic receptor agonists bind to receptor and generate AP, produce contraction but do not release from the receptor; cell cannot repolarize, produces paralysis |
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reversal of depolarizing neuromuscular blocks |
broken down in plasma by pseudocholinesterase enzymes no pharmocologic reversal agents |
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indications for using neuromuscular blockers |
- improvement of surgical field - prevent coughing during intubation/OLV - reducing fractures - intraocular sx - C-section (don't cross the placenta) - reduce the volume of inhalants needed - rapid sequence induction |
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cons of neuromuscular blockers |
- paralysis - patient can't breathe (have to breathe for them) - can't move in response to pain - no hypnotic or analgesic properties (in people, awareness under anesthesia reported more w/ NMBAs) |
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what is residual paralysis? |
presence of undetected weakness after anesthesia residual weakness increases risks of aspiration, airway obstruction, hypoxia risks of residual paralysis increased by residual effects of anesthetic agents, hypothermia monitor with ENS - paralyzed nerves don't respond to stimulation |
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succinylcholine |
depolarizing NMBA |
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benzylisoquinolones |
non-depolarizing NMBAs i.e. atracurium, cisatracurium, etc. can release histamine --> tachycardia, hypotension, bronchospasm extra-hepatic metabolism |
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steroidal NMBAs |
non-depolarizing NMBAs i.e. vecuronium, rocuronium vagolytic - inhibits vagus n. hepatic metabolism, renal excretion |
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Hoffman elimination |
spontaneous nonenzymatic chemical breakdown that occurs at physiological pH and temperature, independent of renal and hepatic metabolism occurs w/ atracurium |
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important functions of CV system |
deliver oxygen from lungs to tissues remove CO2 from tissues and deliver to lung transfer heat deliver hormones, nutrients remove metabolic waste |
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causes of hypothermia under anesthesia |
decreased muscle activity vasodilation of peripheral vasculature depression of thermoregulatory centers in CNS (usu. cold in OR, heat lost from open body cavities, etc.) |
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basal metabolic oxygen requirement |
~10mL/kg/min |
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mixed venous oxygen |
measure of the global balance between supply and demand of oxygen decreases when: oxygen demand increases OR oxygen supply decreases mixed venous oxygen content under normal circumstances = ~15mL/dL |
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arterial oxygen content |
under normal circumstances ~20mL/dL |
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oxygen delivery eqn |
oxygen delivery = cardiac output x oxygen content of arterial blood |
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cardiac output eqn |
cardiac output = stroke volume x heart rate cardiac output = pressure drop/vascular resistance |
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oxygen content eqn
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oxygen content = oxygen on hemoglobin + oxygen in simple solution |
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CV concerns in pediatric and geriatric patients |
more susceptible to CV depression |
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thermoreg. concerns in pediatric and geriatric patients |
hypothermia |
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anesthetic concerns - sighthounds |
altered pharmacokinetics of barbiturates - less fat for drugs to redistribute to leads to prolonged recoveries |
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anesthetic concerns - brachycephalic breeds |
- difficult to visualize rima glottidis
- hypoplastic trachea limits size of endotracheal tube that can be passed
- airway anatomy increases risk of airway obstruction on extubation |
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anesthetic concerns - toy breeds, pediatrics |
hypoglycemia |
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anesthetic concerns - boxers |
bradycardia and hypotension following acepromazine (tx: fluid bolus, atropine) |
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anesthetic concerns - large/giant breeds |
assume subclinical dilated cardiomyopathy - can result in arrhythmias under anesthesia |
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fasting time in adults? in pediatrics/toy breeds? |
adults: usu. fast after midnight, but 6-8 hrs depending on previous meal peds/toy: 1-2 hrs ONLY (monitor BG) |
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why do you need venous access during anesthetic procedures? |
- fluid therapy - ER venous access |
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preoxygenation |
administration of oxygen prior to induction/intubation increases functional residual capacity in case of apnea/hypoxia during induction |
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brachycephalic upper airway syndrome |
stenotic nares elongated soft palate everted laryngeal saccules redundant pharyngeal tissue hypoplastic trachea |
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assessing depth of anesthesia |
too light: globe is central, jaw tone is tight, palpebral reflex present adequate: rotated globe too deep: globe is central, jaw tone is slack, palpebral reflex absent |
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monitoring equipment |
LOOK AT YOUR PATIENT!! stethoscope pulse ox capnograph blood pressure electrocardiography temperature glucometer (peds) |
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complications of equine anesthesia |
- behavior - size - thoraco-abdominal anatomy |
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normal resp rate of horse |
~14 breaths per min |
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normal tidal volume of horse |
10-15 ml/kg |
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dead space of horse |
vd/vt ~60% |
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implications of large dead space volume |
rapid shallow breathing is ineffective ventilator settings should be at low breaths per minute w/ large tidal volumes |
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resp problems w/ horses under anesthesia |
- can generate enough inspiratory pressure to cause pulmonary edema or collapse airways - lungs collapse from position, lack of muscle tone --> atelectesis - increased V/Q mismatch than in SA - need to breathe for horses under anesthesia - IPPV helps w/ oxygenation/delivery of inhalants |
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normal HR in horse |
30-45 beats per minute |
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normal aterial BP in horse |
130/90, MAP 100 |
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CV considerations in horses under anesthesia |
- I-II degree heart blocks are common/non-pathologic - atrial fib is most common arrhythmia - maintain MAP >70 to perfuse muscle, avoid rhabdomyolysis |
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GIT considerations in horses under anesthesia |
- auscult GIT before sedation - fasting >12 hrs decreases fermentation while anesthetized, decreases abdominal distention |
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fasting period in a horse |
>12 hours |
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commonly used sedatives for horses |
xylazine detomidine romifidine dexmed (less severe CV effects than in cats/dogs) |
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agent used to co-induce w/ ketamine
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benzodiazepines (poor sedatives alone, provide muscle relaxation) |
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use of opioids in horses |
often combined to augment sedation mu agonists - better analgesia, concerned w/ ileus (usu small doses don't cause colic) mixed agonists - less analgesia, less pronounced side effects |
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induction agents in horses |
can use inhalants in neonates ketamine/benzo combo in adults |
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concerns w/ inhalants in horses |
hypotension more common/severe than in cats/dogs - use other drug to decrease MAC (ketamine, lidocaine, detomidine) |
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"triple drip" |
guaifenesin, ketamine, xylazine adequate for short procedures common for field procedures |
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complications w/ recovery in horses |
- horses become excited/scared - ataxic - fractures, airway obstruction |
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nerve block for celiotomy in a ruminant |
inverted L or paravertebral |
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nerve block for claw amputation in ruminant |
intravenous regional |
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nerve block for dehorning in ruminant |
zygomaticotemporal |
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nerve block for obstetrical procedures in ruminants |
caudal epidural blocks |
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sedation in ruminants |
xylazine in cattle (@ much lower doses than horses) sheep and goats VERY sensitive. sheep prone to pulmonary edema. normal alpha-2 side effects (bradycardia, hyper- and hypotension, hyperglycemia, thermoregulation inhibition) reverse w/ yohimbine |
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sedation in small ruminants |
benzodiazepines +/- other anesthetic drugs |
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fasting period in adult ruminants |
18-24 hrs off feed. 6-8 hrs off water (shorter in sm ruminants) |
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fasting period in neonatal ruminants |
miss one milk feeding |
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induction of anesthesia in ruminants
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agents: thiopental, ketamine, propofol, guiafenesin keep head elevated to reduce aspiration until tube is inserted/cuff is inflated |
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access to jugular vein in camelids |
- in middle of neck: skin is thick and transverse vertebral processes, muscles overlie the vein - can usually access cranially, but must avoid carotid a. |
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sedation in pigs |
alpha-2 + opiate + ketamine usu most effective; volume of injectate should be minimal IM injections in neck (avoid meat spots) they will bite you |
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catheterization in pigs |
can place catheter in ear vein once sedated |
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complications w/ intubation in pigs |
long, narrow buccal cavity tortuous oro-pharyngo-laryngo-tracheal pathway small larynx can rupture trachea causing pneumomediastinum and pneumothorax |
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malignant hyperthermia |
heritable disease in swine, causing complications under anesthesia caused by uncoupling of metabolic pathways dx: increasing body temp, muscle rigidity tx: stop anesthesia, whole body cooling, dantrolene |
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what do you do immediately after inserting the endotracheal tube? |
provide oxygen |
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to ensure the patient has not arrested after intubation palpate the... |
pulse, apex beat |
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why do you auscult both sides of the chest after induction/intubation? |
to make sure both lungs are being adequately ventilated, and that the endotracheal tube has not been inserted too far into a bronchus |
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when is it appropriate to extubate a normal cat/dog? a brachycephalic cat/dog?
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when the pt has coughed/swallowed several times in a short period when the pt is actively rejecting the tube - gagging, coughing strongly |
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what do you look for or do immediately after extubation? |
check resp rate/effort check pulse ox on room oxygen TPR, assess for pain |
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if a pt is having a rough recovery, what do you do? |
assess pain vs delirium pain - try an opioid bolus delirium - can re-sedate the patient (ace, dexmed) |
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effects of increased abdominal pressure on anesthesia |
- decreases venous return - reduces FRC - increases risk of hypoxia |
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physiologic changes during pregnancy affecting anesthesia |
- increased abdominal pressure - progesterone decreases esophageal tone - dilutional anemia - risk of hemorrhage (increased blood supply to the uterus) - progesterone decreases MAC - decreased vascular resistance |
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anesthetic factors that affect intracranial pressure |
vomiting/coughing increased central venous pressure hypercapnia hypoxemia inhalant anesthetics ketamine severe hypertension |
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Cushing's reflex |
cerebral perfusion pressure = MAP - ICP as ICP increases, blood pressure must increase to perfuse the brain. vasoconstriction increases BP, but produces reflex bradycardia |
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anesthetic concerns in diabetic pts |
hyperglycemia iatrogenic hypoglycemia slow gastric emptying time cardiac autonomic neuropathy possible renal disease DKA |
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problems associated with acidosis |
increased incidence of arrhythmias decreased cardiac function decreased effect of catecholamines increased risk of morbidity/mortality |
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fasting small mammals |
- unnecessary in sm mammals that don't vomit - can be detrimental to the GIT in some species - i.e. rabbits, g. pigs - can lead to dehydration, hypoglycemia - should be done cautiously in pregnant animals - can be difficult in animals that hide food in cheek pouches, or practice coprophagy |
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methods of ferret restraint |
scruffing, wrapping in a towel, tiny ferret muzzles |
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methods of rabbit restraint |
scruffing, wrapping in a towel always restrain/support pelvic limbs and prevent rabbits from kicking back legs and fracturing vertebral column |
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methods of rodent restraint |
scruffing, cup them in your hand, tapered plastic film tubes (pastry bags), purpose designed devices avoid picking them up by their tails |
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sites for blood collection in ferrets |
jugular, cephalic v., lateral saphenous v., cranial vena cava |
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sites for blood collection in mice/rats |
retroorbital venous plexus, superficial temporal v., tail vein |
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atropinases |
circulate in rabbit plasma, cause atropine to have unpredictable effects on heart rate |
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breathing system used in sm mammal anesthesia |
most need non-rebreathing systems (larger rabbits may be big enough for a pediatric rebreathing circuit) |
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features of rabbit upper airway that make intubation difficult
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epiglottis is dorsal to soft palate, must be retracted ventrally butterfly shaped epiglottis mouth doesn't open wide larynx is caudal and ventral to angle of the mandible |
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methods of rabbit intubation |
blind - listen for airflow, use capnograph visualize w/ laryngoscope, otoscope, endoscope retrograde nasotracheal |
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palatal ostium |
connection between oropharynx and pharynx in chinchillas and g. pigs. is highly vascular and prone to trauma/hemorrhage during intubation |
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ways to intubate rats/mice
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w/ otoscope and guide wire w/ fiberoptic endoscope |
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V-gel |
supraglottic device manufactured for rabbits |
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sustained-release opioid used in sm mammals |
buprenorphine |
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porphyrin staining |
can be a sign of pain/stress in rats pigment produced by Harderian gland in the orbit can be seen around eyes, nose and front paws |
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signs of pain in sm mammals |
changes in activity level, hunching, decreased e/d, decreased urination/defecation, reduced grooming, changes in temperament, vocalizations, tachycardia, tachypnea |
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challenges of anesthetizing zoo/wildlife |
often no hx/pre-anesthetic exam/diagnostics limited knowledge of pharmacology, physiology less than ideal environmental conditions stressful, dangerous inductions challenging to provide appropriate supportive care, monitoring |
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human safety risks assoc. w/ zoo/wildlife capture/immobilization |
animal can physically injure humans transmission of zoonotic diseases drugs environmental conditions capture techniques |
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ways to prevent human injuries |
have a plan! communicate! understand the species familiarize w/ the environment handle drugs carefully, w/ a buddy have antagonists readily available wear PPE know where the ER facilities are only use firearms/drug delivery systems if trained |
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factors to account for when selecting free-ranging wild animal immobilization environment |
temperature light conditions terrain non-target animals equipment needed capture technique |
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qualities of an ideal immobilization agent |
small volume needed acts quickly reversible produces hypnosis versatile stable high margin of safety for animal safe for human handler |
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dangerous high and low body temps |
high: 41C (105.8F) low: 35C (95F) |
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prevention of hyperthermia in immobilized wildlife |
avoid capture during hot ambient temps provide shade do not pursue animals for more than 2-5 mins limit stress limit physical restraint |
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treatment of hyperthermia in immobilized wildlife |
active cooling with fluids, antagonize anesthetic agents, oxygen supplementation |
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treatment of rumen tympany/bloat in immobilized wild ruminants |
position in sternal recumbency w/ neck extended elevate cranial end of body pass orogastric tube trocarize pharmacologic antagonism |
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capture myopathy |
most common in ungulates due to massive discharge of the sympathetic nervous system four recognized forms similar to exertional rhabdomyolysis in humans |
