Flashcards in Med Exam Prep from Prodigy Deck (206)
what is the chemical composition of propofol?
Propofol is a 2,6-diisopropyl phenol prepared in an emulsion of 10% soybean oil, 2.25% glycerol, and 1.2% purified egg lecithin.
How does propofol affect respiratory function?
Dose-dependent respiratory depression occurs, with decreases in tidal volume more prominent than decreases in the respiratory rate. Apnea often occurs following initial induction doses.
What accounts for the rapid reawakening of patients following sedative and anesthetic doses of propofol?
Rapid redistribution from the central compartment to the peripheral compartment
When should an open vial or prepared syringe of propofol be discarded? Why?
Opened vials and syringes should be thrown away if they are not used within 12 hours or within 6 hours if the drug was transferred from the original vial. The chemical composition of propofol makes it favorable to bacterial contamination.
Describe how propofol affects CMRO2, ICP, cerebral blood flow, and CPP.
CMRO2, ICP, cerebral blood flow, and CPP are all decreased following administration of propofol.
This is a result of a decrease in MAP and cerebral vasoconstriction.
Describe how the pain on injection of propofol can be attenuated.
Concominant mixture or pretreatment with lidocaine or pretreatment with an opioid is useful in minimizing the pain on injection seen with propofol.
Does age affect propofol's kinetics?
Yes. Elderly patients require less of the drug, while children require higher doses due to their increased volume of distribution.
How does total body clearance of propofol exceed hepatic blood flow?
Extrahepatic mechanisms exist in addition to metabolism by the liver.
Describe the cardiovascular effects of propofol.
Direct myocardial depression occurs, hypotension, decreased CO and SVR, and peripheral vasodilation. Peripheral vasodilation and direct myocardial depression are concentration and dose-dependent. There is arterial vasodilation and venodilation caused by reduction in sympathetic activiity and by a direct effect on vascular smooth muscle.
What is the maintenance infusion dose for propofol?
100-200 mcg/kg/min (or more like 300mcg/kg/min??)
What is the standard induction dose of propofol in a healthy adult?
1 to 2.5 mg/kg
Does propofol trigger malignant hyperthermia?
No. Propofol is safe to use on patients susceptible to MH
In what patients would there be an exaggerated cardiac depressive response to propofol?
Standard induction doses of propofol are associated with significant cardiac depression, however patients greater than 50, ASA 3-4, MAP <70, and concomitant administration of large doses of fentanyl will see an increased myocardial depression greater than normal.
On what receptors does propofol exert its effects?
GABA is the primary inhibitory neurotransmitter of the CNS. Although propofol has been linked to other receptors such as alpha and NMDA receptors, it primarily functions by enhancing GABA inhibitory pathways.
Pretreatment with what drug is recommended in use with ketamine to reduce adverse effects?
Benzodiazepines such as midazolam and diazepam reduce the incidence of sensory and perceptual illusions, nightmares, and postoperative disorientation associated with the use of ketamine. Midazolam appears to be more effective than diazepam in this respect.
Ketamine causes what type of state upon its administration? What are its effects?
A dissociative state. Patient's feel separated from the environment, catatonic, have amnesia, analgesia, with or without a loss of consciousness.
How does ketamine affect BP, CO, HR, and CVP?
They are all increased. Ketamine is the only IV induction agent that is a circulatory stimulant. This is caused by stimulation to the central sympathetic nervous system, and by the inhibition of the reuptake of norepinephrine at sympathetic nerve terminals.
What is the primary route of metabolism for ketamine?
Ketamine is metabolized by microsomal cytochrome P450 enzmes
Does ketamine cross the placental border?
Yes. Ketamine is very lipid soluble and quickly crosses from the placenta to the fetus. Induction doses of 0.5-1 mg/kg, however, does not compromise neonatal status at delivery. Uterine blood flow is maintained as well as uterine tone. Induction doses of 2-2.5 mg/kg result in a depressed neonate upon delivery.
Describe the CNS effects of ketamine.
The patient is in a dissociated state, is cataleptic, often with the eyes being open. Horizontal nystagmus is present. The pupils are reactive to light. There is an increase in salivary gland secretions, lacrimation and eye blinking remain, there is an increase in skeletal muscle tone, and airway reflexes are intact. This cataleptic state is the result of electrophysiologic inhibition of thalamocortical pathways and by the stimulation of the limbic system.
Following a single induction dose of ketamine, what is the duration of anesthesia?
Ketamine-induced anesthesia lasts about 15 minutes.
On what receptor does ketamine exert its effects?
The NMDA receptor.
How does ketamine affect CBF, CMRO2, and ICP.
They are all increased.
How does ketamine affect myocardial oxygen consumption and cardiac work?
They are both increased. Since there is an increase in cardiac work and myocardial oxygen consumption, there is a negative balance between myocardial oxygen supply and demand. Due to this, ketamine should be avoided in patients with severe coronary artery disease
Should ketamine be used in adult patients with poor right ventricular reserve?
No. Ketamine is contraindicated in patients with poor right ventricular reserve due to the increase in pulmonary artery pressure. This increase is not as prominent in the pediatric patient.
Why would ketamine be the IV induction agent of choice in the patient with active bronchospasm?
Ketamine decreases pulmonary resistance and increases pulmonary compliance.
Are airway reflexes intact following ketamine administration?
Yes. Protective airway reflexes are preserved. Muscle tone of the jaw and tongue are maintained as well. Swallowing, gagging, and coughing occur in response to stimulation of the airway.
How does ketamine affect salivary gland, bronchial, and tracheal secretions?
They are all increased. Treatment with an antisialagogue is used to attenuate these effects.
Does ketamine cause respiratory depression?
Yes. This respiratory depression is minimal, however in clinically relevant doses. The decrease in tidal volume is more significant over the decrease in the respiratory rate.