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Intro to Pharm
Muscle relaxants, anesthetics
| Question | Answer |
|---|---|
| Spasticity | exaggerated muscle stretch reflex or rapid lengthening of the muscle invoking a strong contraction in stretched muscle; supraspinal inhibition or control is lost because of a lesion in the spinal cord or brain; not a disease but part of pathologies such a |
| Spasm | increased tension seen in skeletal muscles after injuries and inflammation; tension is involuntary, so patient is unable to relax; different from spasticity: involves input from pain receptors in damaged tissues which excite motor neurons to muscle buildi |
| Muscle spasm treating drugs | baclofen, diazepam (centrally acting agents) |
| Centrally acting muscle relaxants: muscle spasm | mechanism of action unknown, treatment always contains sedation, all drugs equipotent |
| Adverse effects of centrally acting muscle relaxants | CNS depression, hepatic toxicity, physical dependence, all can be administered orally |
| Baclofen-muscle spasms | derivative of GABA, inhibits motor neuron activity in the spinal cord, uses: paraplegia/quadriplegia, MS (not as much generalized weakness as dantrolene); less effective for stroke/cerebral palsy |
| adverse effects of baclofen: muscle spasms | drowsiness, confusion & hallucinations, fatigue/nausea/dizziness/muscle weakness/headache |
| diazepam: muscle spasms | increases GABA inhibition; use: cord lesions or cerebral palsy/acute low back strains |
| adverse effects of diazepam: muscle spasms | sedation, tolerance, physical dependence |
| other central relaxants: muscle spasms | use: adjuncts to other measures, incorporated into tablets with an analgesic, not effective for treatment of spasticity |
| Muscle spasticity treatment | centrally acting agents: diazepam/baclofen; direct acting agent: dantrolene |
| Centrally acting agents: muscle spasticity | Baclofen/diazepam treat spasticity, intrathecal baclofen |
| intrathecal baclofen | administered to severe, intractable spasticity; need smaller doses/less side effects, catheter attached to a pump; decrease in rigidity/increase in muscle function; possibility of tolerance; need better pumps |
| Direct acting relaxants: muscle spasticity | dantrolene |
| Dantrolene | direct acting muscle relaxant: muscle spasticity; suppress release of calcium from sarcoplasmic reticulum resulting in the muscle losing ability to contract; minimal effects on smooth and cardiac muscles; overall function is reduced rather than improved; |
| Uses for dantrolene | advanced MS; cerebral palsy; spinal cord injury |
| Side effects of dantrolene | generalized muscle weakness |
| Other muscle relaxants | Botulinum toxin (binds to presynaptic ACh receptors and prevents release of ACh; only temporary relief for spasms); Transdermal clonidine (antihypertensive agent; binds to CNS receptors-alpha2 & stimulates; unknown why works on spasticity; patch delivery) |
| treatment of muscle spasm | drugs & therapy; relaxants often combined with analgesics: sedatives; no drug best |
| treatment of muscle spasticity | drugs: increase motor function/decrease pain; side effects: sedation, muscle weakness, liver toxicity; reducing spasticity may effect person who relies on increased muscle tone for daily function; Baclofen: lesions on spinal cord; Diazepam: spinal and sup |
| Spasticity and Spasm concerns in rehab pts | encounter often; complement thermal, electrotherapeutic, manual techniques; allows more ROM & stretching activities; sedation is problem; decrease in muscle tone/muscle weakness in antispasticity drugs (facilitate substitution of normal motor control for |
| General anesthetics | produce unconsiousness & lack of responsiveness to all painful stimuli; two groups-inhalational & intravenous; analgesia: loss of sensibility to pain; anesthesia-loss of pain and all other senses |
| properties of an ideal anesthetic | loss of consciousness & sensation; amnesia; muscle relaxation; inhibition of reflexes; low side effects; rapid onset, adjustable & rapid recovery |
| Balanced anesthesia | combination of drugs to compensate for lack of ideal drug; ensure induction is smooth & rapid and analgesia & muscle relaxation are adequate; use short-acting barbituates for induction; use neuromuscular blocking agents for muscle relaxation; use opioids/ |
| Stage I of anesthesia | analgesia |
| stage II of anesthesia | excitement: agitated/restless |
| stage III of anesthesia | surgical anesthesia: deep respiration (want as rapidly as possible and maintain for duration of procedure) |
| stage IV of anesthesia | medullary paralysis: all spontaneous respiration lost |
| inhalation anesthetics: Minimum Alveolar Concentration (MAC) | minimum concentration of drug that will produce immobility in 50% patients exposed to painful stimuli; low MAC indicates high anesthetic potency; most anesthetics low MAC so only need low doses; only nitrous oxide has very high MAC-surgical anesthesia can |
| inhalation anesthetics pharmacokinetics | anesthetic concentration depends on uptake from lungs & distribution |
| mechanism of action-inhalation anesthetic | inhibit neuronal activity in CNS; exact mechanism unknown but 2 theories: general perturbation & specific receptor |
| general perturbation theory | general effect on membrane structure & function by dissolving lipid bilayer |
| specific receptor theory | membrane proteins rather than lipid bilayer are targeted |
| inhalation anesthetics: side effects | respiratory & cardiac depression; sensitization of the heart to catecholamines (halothane specifically, develop dysrhythmias); malignant hyperthermia (genetic predisposition, muscle rigidity & elevated temp, inhalational anesthetic w/succinylcholine--trea |
| inhalational anesthetics: drug interactions | Analgesics, CNS depressants, CNS stimulants |
| Adjuncts to inhalation anesthesia | preanesthetic medications (reduction of anxiety-BDZ/Barb; production of perioperative amnesia; relief of pre & post op pain-opioids; anticholinergic drugs given to decrease risk of bradycardia); neuromuscular blocking agents-induce relaxation; postanesth |
| Classification of inhalational anesthetics | volatile liquids-Halothane, Isoflurane; gases-nitrous oxide |
| Halothane | highly potent, smooth and rapid induction, weak analgesic, low degree of muscle relaxation |
| Side effects of halothane | hypotension, respiration depression, dysrhythmias, malignant hyperthermia, hepatoxicity (liver toxicity only in adults, therefore widely used in children) |
| Isoflurane | most widely used inhalation anesthetic, high potency, induction is rapid & smooth & pts emerge rapidly; more effective than halothane as muscle relaxer |
| side effects of isoflurane | hypotension, respiratory depression (does not cause myocardial depression or sensitize heart to catecholamines |
| Enflurane | similar to halothane, wide spread use, may result in seizures |
| Desflurane | identical to isoflurane, used for maintenance of anesthesia in adults and children and induction of anesthesia in adults |
| Sevoflurane | relatively new similar to desflurane, pleasant odor-mask induction in children |
| Nitrous oxide | low potency but high analgesic properties, impossible to produce surgical anesthesia, complement analgesic properties of primary anesthetic, reduces dose of primary anesthetic used, no serious adverse effects, does not precipitate malignant hyperthermia |
| intravenous anesthetics | used alone or to supplement inhalation agents-permit dose of inhalation agent to be reduced, produce effects that cannot be achieved with inhalation agent alone |
| Short acting barbituate (thiopental) | induction of anesthesia, weak analgesic/muscle relaxer; side effects: cardio/resp depression |
| Benzodiazepines | produce unconsciousness & amnesia, normally use short acting barbs; diazepam-little muscle relax, no analgesia; midazolam-produces conscious sedation (endoscopic procedures)-dangerous cardio/resp effects |
| Propofol | induction and maintenance of anesthesia; high risk of bacterial infection (mixture of egg lecithin) |
| Ketamine | causes dissociate anesthesia; unpleasant psychological reactions may occur (hallucinations, disturbing dreams) but in children; used for children undergoing minor surgery and diagnostic procedures, changing of burn dressings; not in patients with history |
| Inhalation anesthetics: concern for rehab pts | pt. may be woozy, nauseous, muscle weakness, bronchial secretions which may produce respiratory infections-implement respiratory hygiene |
| local anesthetics | do not reduce consciousness but blunt sensation to limited area, suppress pain by blocking impulse conduction along axons (specifically block sodium channels), localized suppression |
| two classes of local anesthetics | esters (procaine/novocain); amides (lidocaine/xylocaine) |
| local anesthetics: esters | procaine/novocain: low incidence of allergic reactions; metabolized by plasma esterases |
| local anesthetics: amides | lidocaine/xylocaine: very low incidence of allergic reactions; metabolized by hepatic enzymes |
| nonselective modifiers of neuronal function (so deliver to spectific area) | block small nonmyelinated neurons more rapidly than large myelinated; lose perception of pain first, followed by in order perception of cold-->warmth-->touch-->deep pressure; drugs can block sensory and motor neurons |
| onset determined by molecular size/lipid solubility/tissue pH | small size, high lipid solubility, low ionization cross rapidly; termination depends on above plus regional blood flow to carry away anesthetic; frequently used with vasoconstrictor (epi) to decrease local blood flow & delay systemic absorption (prolongs |
| Adverse effects of local anesthetics | CNS excitation followed by depression, bradycardia/heart block/cardiac arrest/hypotension; allergic reactions-more likely with ester type; depress uterine contractions prolonging labor |
| procaine (novocain) | ester-type; give by injection; given with epi to delay absorption; systemic toxicity is rare because rapidly converted to nontoxic products; use has declined |
| Lidocaine (xylocain) | amide-type; widely used (topical/injection); more rapid/more intense/more prolonged anesthetic than procaine; combine with epi; CNS/cardio toxicity can result; used to treat dysrhythmias |
| Cocaine | ester-type; excellent local anesthetic; topical administration for ear/nose/throat; causes intense vasoconstriction: do not give with EPI; CNS stimulant-psychological dependence; stimulates the heart and causes vasoconstriction; may result in hypertension |
| topical administration of local anesthetics | relieve pain/itching/soreness, mucous membranes of nose/mouth/bronchi/urethra, hemorrhoids; possible systemic toxicity |
| injection administration of local anesthetics | may result in severe systemic reactions; IV line in place to treat toxicity; monitor patient for cardio/respiratory function |
| concerns for local anesthetics with rehab pts | produce long term improvements in motor function; ionto/phonophoresis; may receive CNS blockade through injection into spinal cord and thus have decreased sensation to thermal/electrical stimulation |
Created by:
mpost51
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