Week 5 Lectures Flashcards
Describe clinical features of high body temperature, including infectious/non-infectious etiology and common patterns
Remittent fever- elevated T and diurnal fluctuation ex) sepsis, TB
Intermittent fever- episodes of fever separated by days of normal temp ex) malaria
Relapsing fever- fevers every 5-7 days ex) Borreliosis and Colorado Tick fever
Episodic fever- few days then remission for 2 weeks ex) familial periodic fevers
Pel-Ebstein fever- cyclical pattern ex) Hodgkin Lymphoma
Continuous fever- stays elevated for days ex) Typhoid
Etiology- fever can be infectious or non infectious; autoimmune (acute rhematic fever) or endocrine (thyroid storm, pheochromocytoma)
Why is high body temperature deleterious for cell membranes and enzyme activity?
enzyme activity is dependent on Temp and pH, hight temperature can denature the enzyme
What is the role of TRPVR1 and CMR1 in neural control of body temperature?
TRPVR1- heat receptor 30-46 C
CMR1- cold and menthol receptor 10-24 C
What is the blood-brain barrier (BBB)?
endothelial tight junctions, blood vessels that vascularize the CNS
How do circumventricular organs help bypass the BBB for core temperature sensing and cytokine access to the hypothalamic thermostat?
permit hormones to leave the brain w/o disrupting BBB. anything in the blood can touch the neurons in OVLT for thermoregulation. binds somatostatin, angiotensin II, and atrial natriuretics
What are the thermoregulation effector organs and their regulators? (hint: glomus bodies, sweat glands, shivering thermogenesis in muscle and non-shivering thermogenesis in liver and, brown adipose tissue, thyroid hormones)
Efferents:
Skin arterioles and sweat glands: constrict and dilate vessels
Liver: heat generation (non shivering)
Brown fat: heat generating, uncouplers (nonshivering)
Muscles: shivering
T3 increases expression of Na+K+ATPase and UCP
What is role of ATP generation and ATP hydrolysis via Na+K+-ATPase and SERCA in thermogenesis?
Malignant hyperthermia: when there’s ryanodine receptor mutation + Halothane + Succinylcholine –> release of Ca2+ from SR, Inc SR Ca2+ ATPase (SERCA) –> Inc ATP hydrolysis, some E lost as heat, malignant hypothermia
Does fever play a protective role in infection/inflammation?
yes, it will kill invading germs before immune response
What are endogenous pyrogens?
molecules that can induce fever
interleukin 1-a (IL-1a)
interleukin 6 (IL-6)
tumor necrosis factor- alpha (TNF-a)
interferon- gamma (INF-y)
What are endogenous antipyretics?
molecules that prevent fever
glucocoritcoids
a-MSH
AVP (ADH)
melatonin
IL-10
What are endogenous antipyretics?
molecules that prevent fever
glucocorticoids
a-MSH
AVP (ADH)
melatonin
IL-10
How does signaling by cytokines cAMP in OVLT-Astrocyte-PON neurons control set point temperature?
endogenous pyrogens bind to OVLT endothelial receptors –> hypothalamic endothelial COX 2 ACTIVATION –> Inc PGE2 –> PGE2 binding to EP3 receptor (PTGER3) on Astrocytes –> Dec cAMP and (-) of warmth sensitive neurons –> Inc in Temp –> fever
How does the signaling by cytokines, PGE2 control the set point temperature?
Macrophages, lymphocytes, and endothelial cells produce pyrogenic cytokines (IL-1,IL-6, TNF-a), pyrogens induve synthesis of PGE2, Inc PGE2 in periphery leads to myaligas and athraligias
Inc PGE2 in hypothalamus –> fever
How does the difference between fever as raised set point and hyperthermia as heat overload relate to their treatment?
because fever is raised set point, it can be treated with NSAIDs, but because hyperthermia involves overwhelming the cooling system and does NOT involve increasing set point, it can only be treated by cooling
Why NSAIDs cannot be used to treat hyperthermia?
NSAIDs work by inhibiting COX2 (leads to inc set point), but hyperthermia DOES NOT involve Inc in set point, so only cooling works
What is the best non-specific treatment of hyperthermia? (hint: cooling)
cooling blankets, apply ice packs to groin, axilla and neck, spray patient with alcohol and water and cool with fans
idiopathic pulmonary arterial hypertension (PAH_ PGI2 analogs
EPOPROSTENOL, TREPROSTINIL, ILOPROST
child with congenital cyanotic heart disease being prepared for surgery: PGE1 analog to maintain temporary patency of ductus arteriosus
ALPROSTADIL
child with PDA, COX1/2 inhibitor to close DA
INDOMETHACIN
aspirin-induced GI ulcers: methyl PGE1
MISOPROSTOL
ripen cervix during labor: PGE2 analog intravaginal gel
DINOPROSTONE
Postpartum hemorrhage: methyl PGE1 contracts uterus
MISOPROSTOL
Glaucoma: PGF2a analog
LATANOPROST
second trimester abortion/postpartum hemorrhage: PGE2a analog
CARBOPROST
post-MORPHINE postoperative pain
KETOROLAC/ ACETAMINOPHEN IV
osteoarthritis: COX 2 blocker
CELECOXIB
fever: COX 1/2 blocker
IBUPROFEN
Migraine: COX 1/2 blocker
NAPROXEN
Myocardial infarction: COX 1/2 blocker (anti-aggregant effect)
ASPIRIN
NOT used to treat asthma as it’s a COX 1/2 blocker and WORSENS bronchoconstriction
ASPIRIN
peak age 6-8 year, aspirin use –> triad of fatty liver degeneration, INC ALT and AST, encephalopathy
pathogenesis- hepatocyte mitochondrial dysfunction –> INC NH3 –> encephalopathy
clinical features (1-5 types) 5- fixed dilated pupils –> death (case fatality rate: 25%-50%)
diagnostic- 3 fold inc in ALT/AST and in serum NH3
pathology: no inflammation in liver or brain
Reye Syndrome
heat-related exposure (prolonged vs exertional), core temperature > 40 C (104 F), CNS Symptoms (headache, N/V, weakness, confusion, dizziness, delirium, convulsions), skin hot, hyperventilation, multiorgan failure
Heat Stroke
prolonged exposure (heat waves, older adults and infants/toddlers), exertional exposure (job, leisure, etc; younger and healthier), predisposing chronic disease, medications, poor nutrition or obesity
Heat Stroke
Heat dissipating mechansism; hypothalmic thermoreceptors (preoptic nucleus) –> 1) vasodilation –> convection loss, conduction loss (ineffective when enviroment temp > skin temp) and radtiation loss (blocked w/ high ambient temps) 2) sweating –> evaporation loss (blocked with high humidity) Heat Generation (ambient temp, humidity, activity level) higher than heat disapasstion (impaired mechanism) IL-1 and IL-2 –> multiorgan failure in severe hyperthermia
Heat Stroke
prolonged heat exposure- classical (heat waves, high humidity, etc), exertional (sports, labor, military), nausea, vomiting, and thirst; painful muscle craps (myalgias), headache, confusion, convulsions and collapse, organ failure (renal, liver, musculoskeletal, cardiovascular)
Heat stroke
core body temp > 40 C (104F), tachycardia, tachypnea, hypotension, agitation, emotional instability, delirium, not alert or oriented, camatose, dry mucous membranes, muscoskeletal (rhabdomyolsis- muscle edema and pain on palation)
Heat stroke
clinical diagnosis, core temp > 40C (104F), CNS dysfunction, exposure to heat
ABCs (intubation if needed, intravaneous normal saline), core body temp measurement, foley cather for urine output, manage organ dysfunction, avoid antipyretics (Tylenol); cooling (goal is core temp 39C), ice bath, avoid shivering
Heat stroke
acute ingestion, chronic ingestion, tinnitus, vertigo, nausea, vomiting, diarrhea, hyperventilation, respiratory alkalosis, anion gap metabolic acidosis, severe ingestion –> organ disease
acute ingestion- (young, psychiatric history, previous overdose, ingestion history or pill bottles); chronic intoxication (elderly, salicylate’s parts of therapeutic medications, inadverent excessive intake, cared for multiple physicains
Aspirin Toxicity
salicylate- directly stimulates medulla, uncomples oxidative phosphorylation, compenatory increase in catabolism (inc O2 consumption, inc heat production, glucose and glycogen depletion, inc CO2), accumulation of organic acids (lactic acid), worsening neurotoxicity as pH dec and crosses into brain tissue
Aspirin toxicity
acute ingestion (vomiting, tinnitus, vertigo, lethargy, seizure, coma, CNS/CV collapse), chronic ingestion (elderly adults, prescription meds with ASA, confusion)
acute ingestion- hyperpnea, hyperthermia, decreased alertness; chronic ingestion- signs of dehydration, decreased alertness and orientation; both can lead to crackles on lung exam (edema)
aspirin toxicity
arterial blood gas- respiratory alkalosis, metabolic acidosis; salicylate level- monitor levels due to delayed absorption; anion gap w/ metabolic acidosis
ABCs, IV sodium bicarbonate, activated charcoal, urinary alkalinization, hemodialysis
Aspirin toxicity
suicide or accidental ingestion, common in children, more severe in adults, early: asymptomatic/mild GI upset followed by liver damage 1-2 days, late: severe hepatic dysfunction and necrosis, elevated APAP level
Acetaminophen (APAP) Toxicity
most common cause of acute liver failure, numerous containing medications, Phase 1 (<24h) absorption and metabolism, phase II (24-72 h) liver abnormalities and dysfn, phase III (72-96h) peak liver dysfn, phase IV (4d-2 weeks) recovery, ESLD, or death
Acetaminophen (APAP) Toxicity
APAP metabolized safely by glucuronidation and sulfation, ~10% metabolized by CYP-450 –> NAPQI; glutathione assists in conversion to non-toxic metaboline BUT glutathione depleted allows –> toxic metabolites; hepatocyte death w/ centrilobular necrosis
Acetaminophen (APAP) Toxicity
suicide attempts, Phase 1- asymtomatic, or nausea and vomiting; Phase II- abdominal pain, jaundice; Phase III- worsening pain and jaundice, bleeding and bruising, encephalopathy; Phase IV- worsening symptoms, improving symptoms
sceral icterus and jaundice, hepatomegaly RUQ tenderness, bleeding and ecchymosis, hypotension and hyperpnea
Acetaminophen (APAP) Toxicity
Serum APAP level- timing of ingestion, ideally 4 hours later; liver assessment; BUN, creatine, glucose, electrolytes for anion gap
activated charcoal, N-acetylcysteine (NAC) inc glutathione, binds NAPQI, enhances coagulation; treat anyway if: evidence hepatocytoxicity, detectable level with unkown time, can’t check APAP level
Acetaminophen (APAP) Toxicity
intermittent flushing, pruritis (itching), abdominal pain, upper GI tract disease (gastritis, PUD), lower GI tract disease (diarrhea), tachycardia and hypotension (leads to cardiovascular collapse)
slight male predominance, occur at any age, rare, cutaneous form (children), systemic form (adults)
Mastocytosis
aspartate to valine substitution of KIT, KIT encodes a stem cell factor receptor, somatic gain of function mutation that is ligand independent, clonal mast cell proliferation, mast cells distrubuted in GI tract
Mastocytosis
cardiovascular (weak, fatigue, palpitation), lung (wheezing), gastrointestinal- upper (dyspepsia, cramps, PUD, gastritis,) lower- (diarrhea, pain, cramps); skin (flushing, itching, rash)
cardiovascular- hypotension, tachycardia; lung- wheexing, GI- abdominal tenderness, hepatomegaly and portal hypertension; skin- red-brown macular or papular rash
Mastocytosis
Tryptase level, KIT mutation testing, cutaneous biopsy, bone marrow biopsy
H1 and H2 antihistamine, mast cell stabalizer (cromolyn), leukotriene or prostoglandin inhibitors (montelukastat or ASA), epinephrine pen, specific tyrosine/multikinase inhibitors or other cytoreductive therapy
Mastocytosis
younger age at onset, episodic subcutaneous and submucosal non-pruritic edema (angioedema), episodic self limited recurrent abdominal pain, no hives or urticaria, may have triggers and mistaken for anaphylaxis
autosomal dominant, rare, first attack typically <15 years old
Hereditary Angioedema
deficiency of C1 inhibitor, bradykinin builds up and is the biological mediator of edema, no mast cell activation
Hereditary Angioedema
complaints of swelling of parts of body no itching, hoarsness, abdominal pain, prodromal symptoms of rash, tingling, fatigue, accused of “drug seeking”
presence of angioedema, asymmetric swelling, stridor, drooling if severe airway involvement, abdominal pain to palpation
Hereditary Angioedema
Check C4 level, without C1 inhibitor, complement of cascade is activated and consumed, C1 inhibitor function
not histamine mediated so epinephrine and steroid have no effect, ABC’s and supportive care, C1 inhibitor, blocade of bradkinin receptor or disruption of kallikrein pathway
Hereditary Angioedema
What are endogenous pyrogens?
molecules that can induce fever
interleukin 1-a (IL-1a)
interleukin 6 (IL-6)
tumor necrosis factor- alpha (TNF-a)
interferon- gamma (INF-y)
What are endogenous antipyretics?
molecules that prevent fever
glucocorticoids
a-MSH
AVP (ADH)
melatonin
IL-10
What are the routes of elimination of drugs?
EXCRETION (primarily renal, hepatic, lungs, sweat glands, mammary glands, placenta)
METABOLISM (hepatic)
What is the first-order kinetics of elimination? Which drugs follow this kinetics?
amount of drug eliminated is proportional to the amount of drug present in the body (natural decay process)
most drugs follow first order kinetics
What is drug clearance?
volume of plasma cleared of a drug in unit time,
determines dose per unit time required to maintains a Cp
Can you calculate elimination rate constant (k) from volume of distribution (Vd), administered I.V. dose (D), and clearance (CL)?
k= CL/ Vd
Cp= D/ Vd
What’s the formula for renal clearance of a drug? What values do you need to do this? (hint: Cp, Curine, urine output)
CL (mL/min) = urine flow (mL/min) X drug conc. in urine (mg/ML) / Cp (mg/mL)
What’s the formula for half-life of drugs with first order kinetics of elimination?
t1/2= 0.7 X Vd / CL
What is zero-order kinetics of elimination? List some drugs that follow this kinetics.
decline in Cp (elimination) is constant with time
PHENYTOIN, ETHANOL, ASPIRIN (PEA)