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What are the characteristics of propofol infusion syndrome?
- metabolic acidosis
- renal insufficiency
- death secondary to cardiovascular collapse
- increased risk in children with long term sedation.
How does propofol work?
Propofol works by increasing GABA-mediated inhibitory tone in the CNS. Propofol decreases the rate of dissociation of GABA from its receptor, thereby increasing the duration of the GABA activated opening of the chloride channel with resulting hyperpolarization of cell membranes.
What is GABA?
gamma -aminobutyric acid
- GABA reduces the activity of the neurons to which it binds.
- It is classified as an inhibitory neurotransmitter.
- Estimated that 40% of the synapses in the human brain work with GABA and therefore have GABA receptors.
- Propofol supports the growth of bacteria. Sterile technique must be observed. Sepsis an death have been linked to contaminated propofol preparations.
- Must be administered within 6 hours of opening vial.
What are the CV effects of propofol?
- decreased ABP
- decreased SVR
- decreased preload
- decreased contractility
- impairs baroreceptor reflex to hypotension
What are the effects of propofol on the respiratory system?
- profound depressant causing apnea following induction dose
- subanesthetic doses used in conscious sedation, inhibits hypoxic ventilatory drive and depresses the normal response to hypercarbia
- depresses upper airway reflexes
- releases histamine, but induction with propofol is accompanied by a lower incidence of wheezing in asthmatic and nonasthmatic patients compared with barbiturates and etomidate
What are the cerebral effects of propofol?
- decreases cerebral blood flow and decreases ICP
- in patients with increased ICP may cause critical reduction in CPP (<50 mmHg). Normal ICP < 20.
- decreases intraocular pressure
What is the induction dose of propofol?
General anesthesia: (healthy adults less than 55 years of age) induction, 40 mg IV every 10 seconds until induction onset (2 to 2.5 mg/kg)
What is the maintenance infusion dose of propofol?
General anesthesia: (healthy adults less than 55 years of age) maintenance, 100 to 200 mcg/kg/min IV infusion (6 to 12 mg/kg/hr); dose varies for age and surgery type
What is the maintenance bolus dose of propofol?
General anesthesia: (healthy adults less than 55 years of age) maintenance, 20 to 50 mg increments IV bolus as needed
What dose of propofol used for MAC?
Monitored anesthesia care sedation: (healthy adults less than 55 years of age) MAC initiation: 100 to 150 mcg/kg/min (6 to 9 mg/kg/hr) IV infusion or 0.5 mg/kg slow IV injection for 3 to 5 min followed immediately by maintenance infusion
Propofol MAC maintenance?
Monitored anesthesia care sedation: (healthy adults less than 55 years of age) MAC maintenance: 25 to 75 mcg/kg/min (1.5 to 4.5 mg/kg/hr) IV infusion or 10 to 20 mg incremental IV bolus doses
What is the dose of propofol for procedural sedation?
Procedural sedation: 1 mg/kg IV followed by 0.5 mg/kg every 3 to 5 minutes as needed for sedation
What is the dose of propofol for ventilated patient in ICU?
Sedation for a mechanically ventilated patient, Intensive care unit: usual maintenance rates 5 to 50 mcg/kg/min (0.3 to 3 mg/kg/hr) or higher
Action and class of ketamine?
- dissociates the thalamus from the limbic system
- closest to be being a "complete"anesthetic
What is the dose of ketamine?
- 1-2 mg/kg
- effect 45-60 sec
- duration 10-20 min
What are the effects of ketamine on CV system?
- Most hemodynamically stable
- indirectly increases sympathetic tone (dependent on the presence of sympathetic reserve)
- Ketamine is a direct myocardial depressant
- increased HR, BP, and CO
- consider increase in myocardial oxygen demands (ischemia)
What are the effects of ketamine on respiratory system?
- ventilatory drive is minimally effected (rapid bolus or combining with opioids may produce apnea)
- upper airway reflexes largely intact
- bronchodilation (racemic)?
- increased salivation - consider glycopyrrolate
What are the cerebral effects of ketamine?
- the received dogma is that ketamine increases:
- cerebral oxygen consumption
- cerebral blood flow
- and ICP
Disadvantages of ketamine?
- psychomimetic reactions upon emergence (disturbing dreams, delirium) consider benzodiazepine to attenuatecardiovascular stimulation may be undesirable
Class and action of etomidate?
- depresses the RAS and mimics the inhibitory effects of GABA
- no analgesia (does not blunt the noxious stimulation of the airway during laryngoscopy)
Hemodynamic effects of etomidate?
- most hemodynamically neutral
- does not cause vasodilation, myocardial depression, or changes in HR. BP and CO are not decreased.
what is the dose of etomidate?
- effect 15-45 sec
- duration 3-12 min
What are the disadvantages of etomidate?
- mild increase in airway resistance
- increased rate of PONV
- venous irritation
- myoclous-30-60% incidence (anticonvulsant)
What are the effects of etomidate on the respiratory system?
even induction doses do not usually result in apnea unless opioids have also been administered
what are the cerebral effects of etomidate?
- because of minimal CV effects, etomidate preserves CPP
- decreases cerebral metabolic rate, cerebral blood flow, and ICP
what are the endocrine effects of etomidate?
Mechanism of action benzodiazepines?
benzo of choice for RSI
- 0.1-0.3mg/kg IVP
- effect 30-60 sec
- duration 15-30 min
infusion 0.05- 0.4mg/kg/hr
- no analgesia
- causes moderate decrease in MAP (10-25%)
CV effects of benzodiazepines?
minimal CV depressant effects even at general anesthetic doses, except when co-administered with opioids
Respiratory effects of benzodiazepines?
careful titration to avoid overdose and apnea. Ventilation must be monitored in al patients receiving bezodiazepines