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define a “routine surgery”. who has had a pet through surgery? who has monitored a surgery? what are the technician’s roles during surgery? don’t prove - improve. Anesthetic Depth. Measured by Stages I-IV

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define a “routine surgery”


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    1. define a “routine surgery”

    2. who has had a pet through surgery? • who has monitored a surgery? • what are the technician’s roles during surgery? • don’t prove - improve

    3. Anesthetic Depth • Measured by Stages I-IV • closely monitor the immediate vitals and the developing trend you have recorded, use your teaching and experience to expect what is likely to happen and PREVENT a situation

    4. monitor surgical stimulus • monitor reflexes THROUGHOUT • ensure strong steady, expected HR • ensure rhythmic respiration, PPV prn • ensure average BP • monitor body temp • every animal is different • use your eyes and hands over any machine ever created

    5. Stages of Anesthesia • Stage I • immediately following administration of a drug • voluntary movement • will be disoriented, may U/BM • panting • slight increase HR • decreasing sensitivity to pain • eyes centrally located, normal pupil size and LR • normal muscle tone, normal reflexes • by end of this stage pt is recumbent

    6. Stage II - excitement/involuntary stage • involuntary struggle, vocalize, paddle, chew, yawn • beginning loss of consciousness • irregular respiration (apnea to pant) • likely increased HR • further decreased pain sensitivity • possible nystagmus, possible dilation, present PLR • good muscle tone • exaggerated reflexes

    7. Stage III - Planes I-IV • Pl I - light anesthesia - intubate • RR 12-20, pattern regulating • HR >90, strong pulse • eyes central or rotated ventromedially, possible nystagmus, pupils constricted, yes PLR • good muscle tone • poor/absent swallow reflex • lick, palpebral reflex present • no surgery, yes intubate

    8. Stage III Pl II - Surgical Anesthesia • moderate depth • RR 8-16, more shallow • decreased HR and BP • possible surgical response (increased HR RR) • eyes rotate ventromedially, pupils dilate, sluggish PLR • muscle relaxation • no pedal or palpebral reflex

    9. Stage III Pl III • deep anesthesia • significant cardiopulmonary depression • RR less than 8, may need PPV (Bag) - low tidal volume • HR 60-90 • low BP, weak pulse • CRT 1.5-2 • no surgical response • eyes central, moderate pupil dilation, sluggish/no PLR • flaccid muscle and jaw tone

    10. Stage III Pl IV - anesthetic overdose • very deep • jerky/rocky respiration, abdominal breathing • HR <60 • prolonged CRT • pupils widely dilated, no PLR • dry eyes • DANGER

    11. Stage IV - Dying • no respiration • HR <40 (unexpectedly) • no CRT, no Pulse • cyanotic • resuscitate if possible

    12. WHEN IN DOUBT STOP ANESTHESIA • turn off gas or stop/reverse injectables

    13. Anesthetic Induction • induce anesthesia - bring the animal to the desired plane of unconsciousness. • may also simply need to maintain anesthesia - keep the patent at the desired plane of unconsciousness • no anesthetic agent accomplishes every (and only) effect needed - multimodal pain management and balanced anesthesia

    14. Inhalant v Injectable • Inhalant • adjust depth • eliminated via lungs (primarily) • on oxygen, easy PPV • requires vaporizer setup • slow induction • waste gases • Injectables • no control over depth (once given) • eliminated via liver/kidneys • on room air, must intubate to PPV • only need syringe and drug • slow recovery • possible to inject in wrong area

    15. Injectable Induction • Most common Injectable Induction agent • - Ketamine/Valium Combo • - Propofol • ALWAYS label syringes when drawn up unless giving immediately. • ANESTHESIA IS GIVEN TO EFFECT (titrate)

    16. Ideal injectable • rapid onset induction and recovery • nontoxic • minimal adverse affects to cardiopulmonary system • rapidly and safely metabolized • offers adequate analgesia • offers appropriate muscle relaxation • available, affordable

    17. typically induction agents are given IV • IM doses are usually available, this dose will usually be 3x the calculated IV dose (ketamine, tiletamine, dexmedetomidine) • how will this affect anesthesia? (speed of induction, speed of recovery, control?) • CRI induction agents • oral ketamine

    18. uptake - speed with which the agent is absorbed into the body and begins taking effect • IV drugs do this quickest • IM SQ agents - must be redistributed before affecting CNS • redistribution - the path a drug takes in the body • IV drug is given, travels to the vessel rich brain (takes effect) then travels to muscle and fat, liver for metabolism, excreted by kidney (under perfect circumstance) • as drug is redistributed from brain, pt begins recovering • cumulative drug effect - drug has not left the the redistribution areas before more drug needs to be carried away from the brain - sighthounds

    19. Injectable Induction Agents • Barbiturates • Cyclohexamines - dissociatives • Neuroleptanalgesics • Propofol

    20. Pharmacodynamics • Ionization - polar (ionized) or non-polar (nonionized) forms - only non polarized compounds can pass through cell membranes at the brain. when pH is normal (7.4) this happens easily and as expected. • if acidotic - compounds can diffuse in brain and exaggerate response (may require less dry to anesthetize)

    21. Protein Binding - compounds are either freely circulating in plasma or bound to proteins. only unbound compounds can enter brain, proteins inhibit • if hypoproteinemic (TP > 3g/dL) - much more drug is available to enter brain, can easily be fatal

    22. brain is highly lipid • Lipid Solubility - tendency of a compound to dissolve in fats/oils. aka partition coefficient • highly lipid soluble compounds cross into brain easily and are quickly redistributed

    23. Redistribution • vessel rich group - brain (CNS) heart liver kidney endocrine system • VRG - 10% body mass, 75% blood flow • muscle - 50% mass, 20% bldflw • fat - 20% mass, 5% bldflw • compounds go to the brain first, high/low concentration carries compounds away from brain to rest of VRG, onto liver for metabolism and kidney for excretion

    24. as compound is redistributed away from the brain the pt recovers • low lipid soluble compounds diffuse way from the VRG and store in muscle and fat longer - this affects the high/low concentration and drugs are not carried away from the brain as quickly (especially if having to redose) - cumulative affect • ultrashort acting barbiturates - thiopental, methohexital

    25. Barbiturates • used for anesthesia but more for anticonvulsants and euthanasia • losing popularity to newer generation anesthetics • all controlled • stimulates GABA - inhibitory transmitter to depress CNS/cause loss of consciousness

    26. Barbiturate Classification • classified on chemical structure, duration of action • Ultra-Short Acting • Short Acting • Intermediate Acting • Long Acting

    27. alternate names • thiobarbiturates - ultra-shorts like thiopental sodium, methohexital • oxybarbiturates - phenobarbital, pentobarbital, thiomyalal • pentobarbital - B-Euthanasia D (the pink stuff)

    28. Ultra-short acting barbiturates • used for general anesthesia • rapidly absorbed and redistributed (ultra-short acting) • onset 30-60 sec • duration 5-20 min • recovery depends on pt (sighthounds)

    29. possible decreased in CO, BP, RR (possible severe), bradycardia, arrhythmia (including PC and bigeminy) coughing, laryngospasm, salivation, tidal, VT • why is decreased tidal volume dangerous? • no significant analgesia • poor muscle relaxation • must be IV - perivascular sloughing (esp thiopental) • thiopental can stimulate PNS - can cause sensitivity to epinephrine - if given can cause arrhythmia (VPC, bigeminy, tachy/bradycardia, AV block - caution using in stressed or cadiac pt

    30. Short Acting Barbiturates (imedazole derivatives) • etomidate • guaifenesin

    31. etomidate - sedative/hypnotic for small animal anesthesia • not controlled • minimal change to cardiopulmonary function • decreases intracranial/intraoccular pressure • excellent for pt with shock or heart dz • wider therapeutic range than thiopental and even propofol • good muscle relaxation • not common due to price and adverse effects

    32. no analgesia • V, muscle movement, excitement during induction/recovery, sneezing, suppresses adrenocortical function (use premeds) • possible phlebitis on injection though must be given IV • rapid injection or repeat doses can cause hemolysis • inj via IV line can help

    33. Guaifenesin GG (glycerol guaiacolate) • as an injectable - sedative and muscle relaxer • used mostly in large animal (combined with other agents for induction/recovery) • also used (far more in companion animal medicine) as an expectorant (Cough Tabs) • minimal changes to cardio/resp/gi systems • irritating to tissues perivascularly • hemolysis in LA

    34. Intermediate Acting Barbiturate - pentobarbital • Pentobarbital sodium • used in lab animal medicine IP for euth, concentrated for SA euth

    35. Long Acting Barbiturate • Phenobarbital - used mostly as anticonvulsant, can be used in sedation • chloramphenicol can increase effect of phenobarbital • barbiturates cross the placenta (decreased respiration for fetus on delivery) • barbiturates enhance neuromuscular block effect of muscle relaxer • chronic use of barbiturates (phenbarb) increase hepatic activity (can increase resistance and shortening of opioid and other meds metabolized by liver

    36. Cyclohexamines(Dissociatives) • most common - ketamine • dissociatives disrupt nerve transmission (inhibit some, stimulate others). n-methyl d-aspartate (NMDA) inhibited to prevent wind-up • wind-up - exaggerated response to low intensity pain stimulus (worsened post-op pain) • onset - IV 90 sec, IM 2-4 min, PO 5-10 min • dogs IV PO, cats IM PO • duration 30-60 min • recovery 2-6 hr

    37. great for immobilizing for brief procedures (local blocks, BCM) • catalepsy - not surgical, awake but no response to surroundings - premed premed premed • often combined with opioids and tranquilizers (ie telazol) • VTI - KAG w/ buprenorphine (can cause hyperthermia post-op) • telazol - tiletamine/zolazepem(diazepam) - lasts 14 days in fridge - can cause hypothermia • see also ket/val • oral ketamine - 100 mg/kg (ie fractious cat)

    38. open eyes, central dilated pupils,possible nystagmus, intact reflexes • increased HR and BP w/o decrease CO • arrhythmia • hypersalivation, V, vocalization, jerking movements/tremors, prolonged recovery • increase intraoccular and CSF pressures • superficial analgesia (no visceral analgesia) • respiratory depression/apneustic breathing (long pause, inhale, short pause, exhale) • metabolized by liver, excreted by kidneys • IM burns - no necrosis expected (like thiopental) • can cause amnesia • DO NOT USE with seizures • possible behavior changes for hrs/days afterward

    39. responsible for tachycardia, vasoconstriction, increased BP • apneustic breathing pattern • increased salivation • increased CSF and intraoccular pressure • muscle rigidity • can cause urinary obstruction

    40. Ket/Val • ketamine/diazepam • one of the most popular agents • combined at equal volumes - 1.2mL Ket/1.2ml Val (for example) • onset 30-90 sec • duration 5-10 min • recovery 30-60 • minimal cardiac depression • good muscle relaxation • smooth recovery • some analgesia • controlled

    41. Tiletamine • reconstituted - 4 days room temp, 14 days refrigerated • used in variety of species IM SQ IV • IM only in dogs/cats • poor visceral analgesia • pt maintains palpebral, corneal, laryngeal, pedal reflexes • increased salivation • long/hard recovery, tremors, seizure, hyperthermia • hypersensitive post-op

    42. Propofol • ultra-short acting non-barbiturate • phenolic compound unlike all other anesthetics • used once to induce, repeatedly prn for maintenance, or CRI • onset 30-60 sec • duration 2-10 min • recover in ~10, standing in 15-30 mins • appetite stimulant in low doses

    43. lists 30 min recovery in cat - many practices do not use this drug in feline medicine - toxicity • NOT controlled • rapid redistribution, not cumulative (still prolonged recovery in sighthounds) • the slower you give it the less you need to use (can be given too slow)

    44. wide safety agent- mild sedation to general anesthesia • decreases intracranial and intraoccular pressure • provides muscle relaxation • antiemetic and anticonvulsant • can be used with valium

    45. no significant analgesia • highly protein bound • severe respiratory distress/ acute apnea especially if given quickly • bradycardia and decreased contractile strength • if too slow - excitation, tremors, paddling, nystagmus • ONLY milky white agent to EVER be given IV (too date) • must be given IV

    46. decreases blood pressure (worse if given rapidly) - do not use in hypotensive pt • possible seizure like activity/reaction - rare • expires quickly - 6 hrs at room temp - contain soy oil and egg lecithin • Propofol 28 - benzyl alcohol • mix all drugs well before use • can keep expired propofol for use during euthanasia • cost is often an issue in practice

    47. Morphine • opioid • onset 15-60 sec • duration 3-6 hr • recovery 2-4 hr • controlled • typical V w/i 15-20 min • popular as CRI • epidural

    48. metabolized by liver, excreted by kidneys • post analgesia can be reversed • possible dysphoria - a feeling of uneasiness and anxiety • decreased GI motility, vasodilation, hypotension (possible hypertension) significant resp depression, pupil constriction

    49. Fentanyl • opioid • very popular analgesic • can be used with valium/midazolam for induction • onset 1-2 min • duration 20-30 min (inj) • profound sedation

    50. bradycardia, sensitive to sound • controlled • reuptake from storage sites, metabolized by liver, excreted by kidneys • also used in CRI • available as transdermal patch (last 3-5 days) (clip fur, wipe with water (no alcohol), apply directly to skin, hold to melt adhesive, wrap lightly, label label label)