TIVA (Total Intravenous Anesthesia & Analgesia) – Flashcards
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Inhalational anesthesia
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Anesthesia is maintained using an inhalational agent -Equipment demanding -No accumulation -Easier to monitor and control anesthetic depth -Safe airways, 100% O2 mechanical ventilation
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TIVA
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Anesthesia maintained using *only IV agents* -Easier technique (no anesthesia machine) -Drugs may cumulate -More difficult to monitor and control anesthetic depth -Still need oxygen support and intubation
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Ideal agent for TIVA
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-Short acting -Stable and short context sensitive half-life -Does not have an active metabolite -Has a wide therapeutic window -Provides smooth recovery
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Components of TIVA
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-*CRI of an anesthetic & analgesic* -Analgesics can be used without anesthetics to deliver pain relief -Adjuvants can be used to aid in muscle relaxation -Anesthetics = *propofol, alfaxalone, ketamine* -Analgesics = *opioids, lidocaine, ketamine, alpha-2 agonists* -Adjuvants = *benzodiazepines, guaifenesin*
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PIVA (Partial Intravenous Anesthesia)
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Anesthesia maintained using both IV and inhalation agents
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Context-sensitive half-life
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-The elimination half-life changes with the duration of infusion -i.e. Propofol and Midazolam are relatively stable and are ideal for TIVA, but Fentanyl and Thiopental have unstable context half-lives, indicating accumulation
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General Anesthesia
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-Unconsciousness (hypnosis) -Immobility (lack of movement in response to noxious stimuli) -Anti-nociception = analgesia -Muscle relaxation
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Drug administration strategies for anesthesia induction
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*Classical* = give half of the calculate dose slowly IV, then top it up with small boluses to effect *Bolus dosing* = give only small boluses up to effect as needed (help avoid severe CV effects) ==> *managing the patient between the minimum effect and toxic effect* *CRI* = onset of effect may be prolonged (no guarantee when steady state is reached
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Analgesic infusions
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-As part of TIVA or PIVA, can be used to reduce doses of anesthetics and provide anti-nociception -Can be used alone to deliver analgesia for non-anesthetized animals (i.e. post-OP or in the ICU)
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Ideal IV drug administration for induction
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1) Give bolus/*loading dose* of anesthetic to initially anesthetize the patient 2) Begin a CRI to maintain the patient *Combines both induction techniques for fast onset and stable blood levels to be achieved*
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Propofol-Fentanyl TIVA
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*Most common TIVA for small animals* -Give loading doses before -Start CRI higher, reduce the rate later -Propofol CRI = 6-24mg/kg/hr -Fentanyl CRI = 0.018 - 0.042mg/kg/hr
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Alfaxalone TIVA
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-Does not seem to accumulate -Dysphoria during recovery should be treated with sedatives -*May be combined with opioid analgesics, i.e. fentanyl CRI* -Dogs = 4-7 mg/kg/hr CRI -Cats = 5-8mg/kg/hr CRI
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Etomidate TIVA = NOPE/NEVER DONE!!!
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*Quick metabolism, no accumulation, but has side effects* -*Inhibition of cortisol secretion -Accumulation of *propylene glycol*
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Ketamine-based TIVA
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Triple drip = anesthetic mixture for *horses* -Guaifenesin -Xylazine -Ketamine
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Opioid CRI
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**Mostly small animals** -Fentanyl = short onset and duration of effect = good opioid (may accumulate after long infusions, but rarely a clinical problem) -Morphine = longer duration of effect and slower onset; common choice in the USA
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Lidocaine
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-Used to relieve abdominal pain in *colic horses* -Abdominal and neuropathic pain in *dogs* -*Narrow therapeutic window* -*Contraindicated in cats due to potential cardiotoxic effects* -Loading dose = 1 - 1.5mg/kg IV -CRI = 1.2-3mg/kg/hr
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Ketamine CRI
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-*Analgesic infusion* -Commonly combined with *opioids* to increase efficacy -CRI up to 3mg/kg/hr during *colic horse surgery*
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MLK Infusion
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-*Highly effective analgesic infusion containing morphine, lidocaine, and ketamine* -Protect from light and use up in 4 days -*Do not stop abruptly; reduce ratio* -*No lidocaine in cats* -*Can be combined with dexmedetomidine if more sedation is needed* (can become dysphoric, esp. cats) -1-2mL/kg/hr IV
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MLK for horses
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-Lidocaine ==> *ketamine infusions are effective* in reducing MAC and suitable for colic horses -Opioids ==> may be good analgesics, but *do not reduce the MAC in horses*
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Dexmedetomidine CRI for SA
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-*Sedative (very strong), analgesic, and anti-epileptic properties* -Can be *combined* with other analgesics -Sometimes used in the ICU
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Dexmedetomidine CRI for Horses
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-Reduces the MAC by 20 - 30% -*Can be substituted with other alpha-2 agonists, i.e. xylazine, detomidine -*Not suitable for risk patients, i.e. colic horses, because of the adverse CV effects*
