Basic1 Flashcards
Bioavalabilty
relative amount of a drug dose that reaches the systemic circulation unchanged and the rate at which this occurs
Drugs that easily pass through the lipid bilayer
small, nonpolar
Volume of distribution
Volume of tissue that the drug reaches
Vd=dose/concentration
Hepatic metabolism
Phase 1 (oxidation, reduction, hydrolysis): by p450 this occurs hydroxylation, dealkylation, deamination, desulration, epoxidation, dehalogenation Phase 2 (conjugation): conjoins hydrophobic drug molecules with polar moities to increase solubility and therefor renal clearance
Drugs with active metabolite
Morphine -> morphine 6-gluconoride (opioid)
Meperidine -> Normeperine (convulsant)
Atracuriun -> laudanosine (convulsant)
issues when pt is renally impaired
metabolism equations
Rate = Q (Cin - Cout)
Extration ratio =(Cin -Cout)/Cin
Clearance =Q X ER
Cockcroft-Gault equation (creatinine clearance)
Creatinine Clearance (ml/min) =[ (140-age) X weight] / 72 X serum creatinine
Tissue clearance
butylchilinesterase = Sux, mivacurium, 2 chroroprocaine, ester LA
nonspecific esters = remifentanil, atracurium
RBC esterases = esmolol
major plasma proteins for binding anesthetic drugs
albumin and alpha-1-acid glycoprotein
epidural opiods
must male their way out of the epidural space if they are to reach their site of action in the spinal cord’s dorsal horn
- lipid soluble drugs (fentanyl, sufentanyl) reach lower peak concentrations in the CSF compard to hydrophilic (morphine)
- lipiphylic drugs more easily transverse vascilar walls and therefor are cleared more rapidly
intrathecal opiods
- lipophilic opioids tend to move out of the aqueous CSF primarily diffusing across the meninges into epidural fat
- explains why morphine (hydrophylic) causes delayed respiratory depression (stays intrathecal and spreads up to brain)
Epidural LA
- intrathecal bioavalabilty increases with lipiphilicity (opposite of opioids)
LA Spinals
1) baricity of solution (adds glucose to make hyperbaric)
2) position of patient
3) concentration of LA
Tolerance vs dependence
Tolerance: requiring increased dosages of a drug to achieve similar effects
dependence: compulsive need of an individual to use a drug to function normally
types of tolerance
1) dispositional (metabolic): repeated use of a drug reduces the amount of drug available at site
2) reduced responsiveness (pharmacodynamic): repeated use alters nerve cell functions
3) behavioral (context-specific): reduces its effect in the environment where it is typically administered but not in other environments.
tachyphylaxis
acute decrease in response to a drug following its administration
half life
half life = 0.693/ Ke
Ke = rate constant
Clearance equation
Clearance = Vd X Ke
Renal clearance
Renal Clearance = concentration of drug in urine X volume of urine / concentration of drug in plasma
Anaphylaxis vs anaphylactoid
anaphylaxis: severe allergic reaction mediated by an aintigen antibody reaction ( type I) IgE
Anaphylactoid resembles anaphylaxis but is not IgE mediated ( does not require prior sensitization)
most common cause of anaphylaxis
NDNMB
latex allergy risks
chronic exposure to latex, neural tube defects, frequent caths
MOA of inhaled gasses
proposed:
enhance inhibitory receptors (GABA and glycine)
dampen excitatory pathways (nicotinic and glutamate)
Rate of equilibirum in gasses
rate is directly related to alveolar gas concentration
high partition coefficient= high solubility= slow rate of induction
Cardiovascular effects of inhaled anesthetics
- Map decreased by decreaseing SVR (except halothan which decreases CO and MAP with no change in SVR)
- HR increases initially
- abrupt changes in halothane can cause drastic increases in HR and BP
- sensitize the myocardium to epinephrine, depress mycardial contractility
- Sevo causes QT prolongation
- Iso has coronary vasodilating properties
Pulmonary effects of inhaled anesthetics
- Increase RR with decrease TV = same MV
- blunt ventilatory stimulation caused by hypoxemia and hypercarbia
- increases atelectasis and decrease FRC
- bronchodilation
CNS effects of inhaled anesthetics
- uncouple CBF and CMRO2. increase and decrease respectively
- nitrous oxide increased CMRO2
- depress the amplitude and increase the latency of somatosensory evoked potentials (SSEPs)
- Sevo may be associated with epileptiform activity on the EEG at high concentration
Opioids MOA
work on mu, kappa and delta
- G coupled receptors => cAMP
1) inhibition of presynaptic Ca2+ influx
2) increasing postsynaptic K+ efflux
3) activation of the descending inhibitory pain pathway via inhibition of GABAergic receptors in brain stem
Bayes theorem
how the probability that a theory is true is affected by a new piece of evidence
- used to help develop preoperative testing algorithms by helping clinicians interpret testing results in light of the patient presentation and surgical procedure
ulnar nerve neuropathy
Postoperative ulnar nerve injury is the most common form of perioperative peripheral neuropathy. It occurs more commonly in males and very thin or obese patients. Ulnar neuropathy is typically transient but can persist and cause morbidity and disability. Nerve conduction studies are beneficial in evaluating both motor and sensory deficits.
most efficient way to decrease costs of OR
math OR scheduling with full time anesthesiology staffing
Latex allergy
Health care workers, children with spina bifida and urogenital syndromes, and people with allergies to banana, avocado, kiwi, pineapple, mango, and other tropical fruits have an increased risk for development of a latex allergy. Frequent cosmetic use may be related to antibodies against aminosteroid NMBDs (pancuronium, pipercurium, rocuronium, and vecuronium), but there is no increased association with a latex allergy.
Most influences how nitric oxide works in the body
site of production:
-due to very short half life
Drug abuse
Risk factors for substance abuse include access to substances of abuse, personal history of drug abuse, family history of drug abuse, younger age, psychologic disease, and a history of preadolescent sexual abuse.
NOT HIGH EXPECTATIONS- may be protective
POPE
mechanism of POPE is the large negative pressure developed by inspiration against an occluded airway, heralding an increased preload and afterload that increases pulmonary blood volumes and venous pressures, which leads to increased hydrostatic pressure and the formation of pulmonary edema
- Two other factors involved are hypoxia and a hyperadrenergic response, both of which promote translocation of blood from the systemic to pulmonary circulation that also increases pulmonary pressures.
- Tx: PPV
ABO incompatibility labs
INcreased: bilirubin (both), urine hemoglobin, INR, PT/PTT, fibrin degradation products, BUN, LDH, creatinine
Decreased: haptoglobin, fibrin, platelet count
upregulater acetylcholine nicotinic channels
Causes of Nicotinic AChR Upregulation - Nerve Injuries o Stroke o Spinal cord injury - Burns (24 hours up to 1-2 years after burn injury) - Prolonged immobility (risk greatest after 16 days) - Prolonged exposure to neuromuscular blockers - Myopathies o Duchenne muscular dystrophy - Denervation Disorders o Multiple sclerosis o Guillain-Barré syndrome o Amyotrophic lateral sclerosis
Post MI treatment
Following a myocardial infarction lifestyle modification and control of systemic disease should occur. Medications to be initiated following a myocardial infarction should be beta-blocker, ACE-I, statin, and aspirin.
SSEP during ischemia
decreased amplitude and increased latency
etomidate
- GABA agonist
- minimal effects on cardiac function or vascular tone and does not cause histamine release
- decreases cerebral metabolic oxygen demand, cerebral blood flow, and intracranial pressure (ICP), but maintains cerebral perfusion pressure
- adrenal suppresion ; inhibits the adrenal enzyme 11-β hydroxylase, the downstream effects of which are inhibition of cortisol (and aldosterone) synthesis
methadone side effects
prolonged QT interval
- possible torsades de pointes
gas cylinder coloring
oxygen: green, carbon dioxide: gray, nitrous oxide: blue, nitrogen: black, air: yellow, helium: brown.
oxygen-hemoglobin dissociation curve
Hyperthermia, acidosis, high pCO2, and high levels of 2,3-DPG cause a shift to the right. Fetal hemoglobin shifts the curve to the left
Barbiturates
MOA: increase duration of cl- channels at GABA receptors, some NMDA action too
- small nonionized form easily passes through BBB= quick, termination is by redistribution
- cleared by liver (except phenobarbital = renal)
barbiturates CNS
- methohexital can provoke involuntary muscle contractions and elicit seizure activity
- overall decrease CMRO2,
- decrease ICP
- preserve autoregulation
- minimal effects of SSEPs and MEPs
barbiturates cardio
decrease BP and increase HR
side effects of barbiturates
thiopental= garlic or onion taste
sulfur-containing thiobarbiturates evoke mast cell histamine release
intraarterial injection results in severe vasoconstriction
Clearance of propofol
metabolized in liver, but clearance exceeds liver metabolism suggesting extra-hepatic metabolism.
propofol and CNS
causes burst supression at intubation doses
decreases ICP, CMRO2, and CBF
Etomidate (2)
- carboxylated imidazole
- targets major inhibitory ion channels in the brain; the GABAa receptor
- termination is due to redistribution for bolus
- adrenocortical supression due to 11 beta hydroxylase
Ketamine
- works as antagonists to NMDA in thalamus and limbic system
- binds mu opioid receptors and provides analgesic effects at subanesthetic doses
- raises ICP by increase in MAP and higher CPP
- depresses myocardia and smooth muscle but also increases circulation catecholamines with net increase in BP, HR, CO and myocardial O2 consumption
- increases secretions
- clearance strongly related to liver blood flow
St John wart induces which enzyme
P450 3A4 and P450 2C9 enzymes.
St. John’s wort is a drug used to help treat anxiety and depression. St. John’s wort has mild sedative properties, which can affect anesthesia. St. John’s wort should be used with caution in patients taking MAO-Is or SSRIs. Additionally, St. John’s wort has been associated with delayed arousal from anesthesia, and some argue that MAC may be decreased in patients taking a St. John’s wort.
herbals that increase risk of bleeding
Ginger, garlic, ginkgo, and vitamin E
buprenorphine
-ceiling effect at higher doses
pipeline failure
Management of pipeline failure or gas crossover:
1) Disconnect the pipeline connection at the wall.
2) Open the emergency oxygen cylinder fully.
3) Ventilate by hand with the anesthesia breathing circuit.
hormones after acute stress (surgery)
1) Sympathoadrenomedullary axis: sympathetic nervous system activity, epinephrine secretion from the adrenal medulla
2) Hypothalamic-pituitary-adrenocortical (HPA) axis: corticotropin-releasing hormone (CRH), adrenocorticotropic hormone (ACTH), cortisol
3) Counter-regulatory hormones: catecholamines, glucagon, growth hormone*, cortisol
4) Proinflammatory mediators: tumor necrosis factor–alpha (TNF-a), interleukin (IL)-1, and IL-6, IL-8, IFN-γ
5) Salt and water retention, sustain blood pressure: renin-angiotensin-aldosterone system, vasopressin#, catecholamines
* GH increases initially, followed by a decline on postoperative day 1.
# In response to surgical stress, vasopressin increases and remains elevated; in septic shock, an initial increase is followed by a decrease to extremely low concentrations
T3 is decreased