Term
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Definition
-sedation and anxiolysis
-balanced anaesthesia technique
-analgesia
-counter the effects of other anaesthetic agents
-contribute to a smooth, quite recoevery after anaesthesia |
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Term
| Aim of sedation / anxiolysis in premed? |
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Definition
-to facilitate patient handling
-dec. stress to animal when anaes. induced |
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Term
| Aim of sedation when used alone |
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Definition
| make the animal quiter to allow a procedure w/o the need for GA |
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Term
| Disadvantages of sedation |
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Definition
-although often using the same drugs as for GA but at lower conc. there is much dec. monitoring / no intubation
-usually sedation alone, c.f. as premed., has a higher degree of CNS depression and so CV and resp depression |
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Term
| Ideal properties of drugs used for premed / sedation |
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Definition
NB: most do not have all of these properties, therefore use combos.
-produce reliable sedation and anxiolysis
-minimal effects of CV system
-cause minimal resp. depression
-provide analgesia
-be reversible |
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Term
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Definition
-uses combo of drugs w. different specific effects
-allows dec. dose of individual drugs, and so dec. s. effects
-maximises reliability of sedation achieved
-often take advantage of synergystic action between groups of sed. drugs |
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Term
| Name the 4 classes of drugs used for premed and sedation |
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Definition
1. Phenothiazines e.g. Acepromazine (ACP)
2. Alpha-2-agonists e.g. xylazine, medetomidine, dexmedetomidine
3. Benzodiazepines e.g. diazepam, midazolam
4. Opiod |
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Term
| Which premed is especially common in horses? why? |
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Definition
| Acepromazine - admin of ACP is associated w. DECR. risk in anaesthesia |
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Term
| What is the most commonly used premed in UK? |
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Definition
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Term
| Acepromazine (ACP) summary |
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Definition
used for premed:
-causes sedation and anxiolysis, initially dose dependent
-no analgesia
-long-lasting and non-reversible
-peripheral vasodilation and decr. |
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Term
| Descibe the level of sedation provided by ACP? |
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Definition
-generally less reliable than alpha-2-agonist sedation
-quality and reliability can be improved by combo w. opiod, which also provides analgesia (neurolepanalgesia) |
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Term
| How does dose relate to effects in ACP? |
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Definition
-Initially sedation and anxiolysis are dose dependent
i.e. as dose incr., sedation incr.
-w. larger doses the degree of sedation is unchanged but s. effects and duration of action incr. |
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Term
| How can sedation w. ACP be maximised? |
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Definition
-quality and reliability can be improved by combo w. opiod
-maximise sedation be leaving undisturbed for 30-40mins after admin
-quite handling is essential - can wake up if roused or excited |
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Term
| Describe other pharmacological effects of ACP, not related to its role as premed? |
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Definition
-peripheral vasodil and dec. BP due to alpha-1 antagonism
-anti-arrhythmic properties
-minimal resp effects
-dec. body T due to resetting thermoreg. mechanisms and incr. heat loss due to peripheral vasodil
-no effect on seizure thresold |
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Term
| In which animals should ACP be avoided? |
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Definition
-animals w. marked CV dz or if in shock (peripheral vasodil and decr BP)
-giant dog breeds, esp boxers, are thought to be "more sensitive" to ACP effects so take more care - probably because relatively OD as drug calculated according to bodywt not metabolic size (larger animals have smaller met. size) |
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Term
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Definition
used for premed;
-potent sedative and analgesic drugs
-also muscle relaxation
-temperature conservation
-reversible
-limited CV margin of safety
-currently selected over ACP in CV stable animals |
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Term
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Definition
-xylazine
-medetomidine
-dexmedetomidine - most selective currently available and most popular |
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Term
| Descibe the level of sedation provided by alpha-2-agonists |
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Definition
| more profound than ACP, esp if ACP alone |
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Term
| How does dose relate to effect in alpha-2-agonists? |
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Definition
| Initially sedation is dose dependent, but then plateus (as for ACP) and incr. in dose prolong the duration of action rather than incr. sedation |
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Term
| Effect of alpha-2-agonists and opiods or BZDs? |
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Definition
-synergistic action
-combo. reaults in more profound sedation and dec. dose of alpha-2-agonist |
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Term
| Following premed w. alpha-2-agonists, what needs to be considered when administrating anaesthesia? |
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Definition
-significant drug sparing effect - need to decr. dose of other drugs or effectively OD!
-IV induction agents must be given slowly and to effect
-alpha-2-agonists have potente analgesic properties |
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Term
| Describe other pharmacological effects of ACP, not related to its role as premed? |
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Definition
-biphasic effect on BP (initial incr., then return to normal or slightly below normal)
-HR and CO decr. throughout
-minimal resp. effects
-BF to the liver and hence drug metabolism decr (not an issue in healthy animals)
-decr. heat loss due to peripheral vasoconstriction - easier to maintain temp peri-op c.f. ACP
-incr. urine production |
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Term
| In which animals should alpha-2-agonists be avoided? |
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Definition
-in animals w. ltd CV reserve, the decr in CO may result in decr. O2 delivery to central organs
-only suitable for indiv. with normal functioning CV systems
-avoided in animals w. liver dz. due to decr. BF to the liver
-avoid if very young or old |
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Term
| Reversal of alpha-2-agonist |
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Definition
Reversal w. atipamezole (alpha-2-antagonist)
-recoveries following atipamezole IM admin are generally smooth and good quality
-not given IV - rapid, excitable recovery
-must remember to supplement analgesia before antagonising! |
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Term
| Bezodiazepines (BZDs) summary |
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Definition
-given in combo w. other sedatives
-poor sedation but minimal resp and CV effects
-can be reversed w. flumazenil but expensive so not really used |
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Term
| Describe the level of sedation provided by BZDz |
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Definition
-administered alone to healthy animals there is minimal or no sedation - may even cause excitation
-can be good sedation in sick or young animals |
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Term
| Describe other pharmacological effects of BZD, not related to its role as premed? |
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Definition
-minimal CV and resp effects
-anticonvulsant effects
-care in patients w. liver dz - can result in hepatic encephalopthy |
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Term
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Definition
-used as premed in animals w. compromised CV function
-used to manage convulsions |
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Term
| What is the effect of addition of an opiod to the premed regime? |
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Definition
-improve sedation
-provide analgesia
-dec. required dose of hypnotic agent
i.e. contribute to a balanced anaestheisa
-It is rare that a premed. does not include an opiod |
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Term
| Most commonly used opiods for premed? |
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Definition
-methadone and morphine
-good analgesia - used for procedures causing moderate-severe pain
-lasts 3-4 hours |
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Term
| Examples of drug combos for premed and sedation |
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Definition
-ACP and opiod
-Dexmedetomidine and opiod
-Dexmedetomidine and BZD
-Dexmedetomidine and Ketamine
-BZD and opiod
-BZD and Ketamine |
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Term
| Dexmedetomidine and ketamine |
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Definition
-although can be used to provide sedation for short invasive procedures, it will produce a state of anaes. so cannot be called a premed
-important to wait at least 45 mins before reversing dexmedetomidine, or get unmasked excitation effects of ketamine |
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Term
| BZD and opiod premed combo |
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Definition
"CV friendly" for premed or sedation of dogs w. CV problmes
-in sicker animals, resoable sedation can be achieved
-not optimal in cats - use BZD and ket? |
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Term
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Definition
-usefule for sedating cats in which heavy sedation is required
-depending on ket dose, can induse anaesthesia ad BZD prevents excitatory effects of ket
-also CV friendly |
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Term
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Definition
An injectable anaesthetic - low doses can be used to induce "sedation" in cats and dogs for short periods
-but small distinction between sedation and anaes. dose |
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Term
| factors influencing choice of sedative / premed |
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Definition
-reason for anaes. or sedation
-duration
-procedure
-degree of pain predicted
-spp. and breed
-age
-ASA classification |
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Term
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Definition
-muscle-relaxant that is used as a part of many anesthetic protocols esp in the horse
-also mild analgesic and mild sedative properties
-relatively little resp. depression at normal doses
-used for induction before inhalation anesthesia, during inhalation anesthesia and with total intravenous anesthesia (TIVA) for short procedures |
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