Pre-anesthesia Drugs & Analgesia – Flashcards
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Anesthetic agent
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any drug used to induce a loss of sensation with or without unconsciousness (lidocaine)
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Adjunct
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a drug that is not a true anesthetic but used to produce other desired effects such as sedation, muscle relaxation, analgesia, reversal, neuromuscular blockade or parasympathetic blockade
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Preanesthetic medications
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drugs given before general anesthesia
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reversal agents
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less or abolish the effects of other anesthestics
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induction agents
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used to induce general anesthesia (ketamine, valium)
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maintenance agents
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used to maintain general anesthesia (propophol)
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pharmacokinetics
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the effect the body has on drugs
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pharmacodynamics
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the effects a drug has on a body
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agonist
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binds to and stimulates tissue receptors in the central nervous system
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antagonist
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bind to byt do not stimulate receptors (block action of agonist), reversal agent
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analgesia
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loss of sensitivity to pain (must be provided before, during and after anesthetic event)
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DEA drug enforcement agency
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regulates purchasing, handling and disposal of controlled substances requires detailed records: logbook & periodic inventory
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storage of controlled substances
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double-locked cabinet or safe
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premedication
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a single or combo of drugs given prior to general anesthesia
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considerations for premedication dose
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specific patient history physical diagnosis tests risk factors: age, respiratory, druge reactions, diabetes, liver disease
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when is premedication administered
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15-20 min prior to induction IM or SQ (also IV or oral)
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3 groups of premeds
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1. Antichoinergics (parasympatholytics) 2. Sedatives/tranquilizers 3. Analgesics (opioids, pain mgmt)
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purpose of premeds
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relaxes patient, muscles pain meds at optimum time (before surgical trauma) minimize adverse effects of concurrently administered drugs smoother anesthetic induction & recovery minimize induction agent amount & maintenance anesthesia amount (balanced anesthetic, less is best) easier to work with patient, place IV
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contraindications of premeds
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weak/debilitated animal sick or unresponsive pregnancy of animal (drugs cross placenta) exacerbation of existing illnes/condition (atropine in hyperthyroid cat or acepromazine in epileptic dog) short procedure, outpatient surgery
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sympathetic nervous system
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epinephrine & norepinephrine: fight/flight response increased heart rate dilated pupils dilated bronchi decreased gut motility relaxation of urethral sphincter
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mydriasis
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dilation of the pupil
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parasympathetic nervous system
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acetycholine decreased heart rate constricted pupils bronchi constriction increased gut motility (vomit/diarrhea) constriction of urethral sphincter
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Anticholinergics (parasympatholytics)
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block passage of impulses through the parasympathetic nerves block acetycholine reduce bradycardia reduce salivation reduce GI activity dilate pupils
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special reason for using anticholinergic
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blocks stimulation of vagus nerve caused by handling of viscera & eyes, therefore blocking any depressed heart/breath rate caused by handling of eyes/viscera
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contraindications of anticholinergics
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cardiac arrhythmia sinus tachycardia constipation glaucoma thick mucus secretions (cat- blocks airway) endoscopic (GI) procedures where GI function needs to be seen
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Atropine sulfate
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natural, plant derived quick onset (5 min, peaks in 15-20, lasts 60-90) decrease saliva increases heart rate fast elimination from body give SQ, IM or IV
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Glycopyrrolate
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synthetic, expensive reduces saliva more than atropine prevents decreased heart rate (but does not increase) give SQ, IM or IV (IM quick onset, peak 30-45, lasts 2-3hrs) does not cross placenta
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tranquilizers
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reduce anxiety but not necessarily awareness/wakefulness no analgesic properties calms patient
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sedatives
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reduce stress, fear & anxiety reduces mental activity causes sleepiness no analgesic properties
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phenothiazines (acepromazine)
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give IM or SQ (onset in 15 mn, last 4-8 hrs) calms reduces alertness sedates CNS antiemetic antiarrhythmic antihistamine blocks epinephrine (decreases BP) NO ANALGESIA mfr dosing too heavy
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contraindications of phenothiazines
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when allergy testing (antihistamine effect) eplileptics (lowers seizure threshold) liver disease (metabolizes in liver) debilitated, geriatric or neonatal patients
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benzodiazepines (diazepam, zolazepam, telazol, midozolam)
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reversal agent: flumazenil antianxiety/calming but not drowsy NO ANALGESIA anticonvulsant muscle relaxant minimal adverse effects on cardio/resp systems enhances sedation & analgesia of other agents
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contraindications of benzodiazepines
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liver disease may cause dysphoria & excitement in young animals
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dysphoria
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abnormal depression and discontent
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diazepam (valium)
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used with ketamime to induce anesthesia give slowly IV only non water soluable (mix w/ ketmine only) light sensitive soluable in plastic crosses placenta oral admin causes hepatic failure in cats appetite stimulant
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midozolam
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water soluable less iritating as IM or SQ crosses placenta light sensitive
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zolazepam
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available as Telazol only
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Alpha-2-agonists
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non-controlled drugs potent sedatives (onset 5-30 min, lasts 1-2 hrs) reliable effect, reversible ANALGESIA nullifies fight/flight used as premed, or induction drug for minor procedure causes: bradycardia, arrhythmia, hypertension then hypotension, respiratory depression, vasoconstriction (cyanotic MM), vomiting, GI unmotility, hyperglycemia (lower insulin)
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contraindications of alpha-2-agonists
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geriatric or debilitatied animals heart, respiratory, liver or kidney disease pregnancy hypotensive or dehydrated animal GDV predisposition hyperglycemia
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xylazine
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large or small animals (different concentrations) IM or IV ANALGESIA lasts 20 min can combo with other agents
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dexmedetomidine (dexdomitor)
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most common more potent, less side effects than xylazine sedative ANALGESIA IM only cats (absorbed too fast) IV cat or dog dose by body surface area can combine with butorphanol, ketamine keep patient in quiet area 15-20 min after injection
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yohimbine
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reversal of xylazine
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atipamezole
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reversal of dexmedetomidine
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analgesia
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absense of awareness of pain but not loss of consciousness
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analgesic
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pain med that can be used as premed, induction agent, intra- and post-operatively
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effect of untreated pain in animals
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increased fear & anxiety decreased cardiovascular function decreased appetite slower wound healing greater risk of infection
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signs of pain
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agitation/restlessness vocalization quiet/depressed/inactive frowning, squinting, ears back aggressive, resist handling clingy difficulty sleeping lack of appetite stiff body, reluctance to move cats: hunched position staring into space lick/stare/bite area of pain (hot spot) mydriasis increased heart rate/ reath rate, BP
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opioids
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controlled drugs (narcotic) derived from poppies ANALGESIA sedative can be agonist or antagonist or both combo with traquilizer and/or anticholinergic during pre anesthesia
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3 opioid receptors
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mu (µ), kappa (x), delta (δ)
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opioid effects
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most effective analgesic CNS depression in dogs excitability in cats bradycardia panting in dogs myosis in dogs mydriasis in cats increased reaction to sound salivates hypotension respiratory depression vomit/diarrhea then constipation
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contraindications of opioids
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patient on behavior meds kidney, respiratory, liver disease foreign body in GI severe dehydration
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opioid antagonists
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naloxone hydrochloride IV or IM butorphanol to reverse pure agonists (ie fentanyl)
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use opioids for
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moderate to severe pain (morphine, hydromorphone, oxymorphone, fentanyl)
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morphine
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pure mu agonist give IM, SQ, IV (slow), intraarticular, epidural injection may cause low BP if given too fast may cause GI stimulation, salivation, defecation, vomit, excitement (cats), dpressed cardio or resp, panting lasts 2-4 hrs injected, 4-12 hrs PO
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acepromezine with morphine
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acepromezine given 15-20 min before morphine reduces vomiting
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oxymorphone
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pure mu agonist greater analgesic & sedative than morphine less side effects than morphine longer duration of analgesia than morphine IV, IM, SQ, epidural lasts 3-4 hrs expensive less vomiting or hypotension
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hydromorphone
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less potent than oxymorphone, similar duration IV, IM, SQ no excitement in cats no release of histamine
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fentanyl
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most potent rapid onset (2 min) short duration (30 min after IV) admin by drip, skin patch, IM, SQ, epidural admin by transdermal (6-24 hr onset, lasts 48 hr) heat, skin abrasion causes faster absorbtion
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butorphanol (Torbugesic)
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mild to moderate pain kappa agonist, partial mu agonist can be reversal for other opioids DO NOT USE WITH FENTANYL (reverses) IV, IM, SQ (epidural is toxic) lasts 1-4 hrs PO may last 6-12 hrs preanesthetic
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buprenorphine (Buprenex)
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minimal sedative effect mild to moderate pain partial mu agonist IV, IM or lingual (cats buccally due to cat mucosa pH) slow onset (30-45 min) expensive
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NSAIDS
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mild to moderate pain inhibit COX-1 & COX-2 enzymes somatic & visceral pain 30-60 min peak effect anti-inflammatory antipyretic (fever reducer)
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NSAID side effects
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GI ulcers renal toxicity prolonged bleeding/impaired platelets liver damage CATS: hepatotoxicosis in 4 hrs of ingestion
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types of NSAIDS
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carprofen meloxicam ketoprofen deracoxib rimidil (check liver profile every 6 mo) acetylsalic acid (aspirin) (DOG only) acetominophen (DOG only)
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use of local anesthetic
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CCL repair
