Weakness Flashcards
What are the 5 I’s of Geriatrics?
- Impaired homeostasis
- Incompetence
- Incontinence
- Impaired mobility, falls, weakness
- Iatrogenesis
How common are iatrogenic illnesses in older patients?
What kind is the most common?
What is the result?
- 1/3 acutely hospitallized older patients
- Adverse drug reactions
- Functional losses & increased costs
What are some factors that affect drug disposition & response in the elderly?
- Body composition
- Reduced TBW
- Reduced lean body mass/weight
- Increased body fat
- Protein binding
- Reduced serum albumin
Elderly Patients
Drugs that distribute to body fat will have a (higher/lower) volume of distribution.
Drugs that distribute to TBW will have a (higher/lower) volume of distribution.
Drugs that distribute to body fat will have a higher volume of distribution.
Drugs that distribute to TBW will have a lower volume of distribution.
What are the functions of the kidney?
- Excretion of metabolic waste products & foreign chemicals
- Regulation of water & electrolyte balances
- Regulation of body fluid osmolality & electrolyte concentrations
- Regulation of arterial pressure
- Regulation of acid-base balance
- Secretion, metabolism & excretion of hormones
- Gluconeogenesis
Estimate the interstitial fluid volume of a healthy individual with a body mass of 60 kg.
- 36 liters
- 24 liters
- 12 liters
- 9 liters
- 3 liters
9 liters
- ICF = 40% body weight
- ECF = 20% body weight
- Interstitial fluid = 3/4 ECF
- Plasma volume = 1/4 ECF
What is the equation for blood volume?
Plasma volume/(1-Hct)
An individual of normal body composition (plasma osmolarity = 280 mOsm/l) ingests 1 liter of a solution containing 200 mmole/L NaCl. After equilibrium of body fluids, & before any renal excretion has occurred, which statement will be true?
- His TBW is reduced compared to initial conditions
- His interstitial fluid osmolarity will be reduced compared to initial conditions
- His plasma volume will be reduced compared to initial conditions
- His intracellular fluid osmolarity will be increased compared to initial conditions
- His intracellular fluid volume will be increased compared to initial conditions
His intracellular fluid osmolarity will be increased compared to initial conditions
- The ingestion of a hypertonic NaCl solution will lead to an increase in TBW, an increase in ECFV & an increase in osmolarity is all fluid compartments, & a decrease in ICFV
What is the composition of the fluid in the different compartments?
water, electrolytes, non-electrolyte small molecules, protein
What is the difference btwn plasma & interstitial fluid?
- Plasma ~ interstitial fluid, except for more proteins in plasma
- Capillary wall is highly permeable to water, electrolytes, and other small molecules, but not proteins
What is the difference btwn ECF & ICF?
- ECF & ICF have substantial differences
- The cell membrane is highly permeable to water, but not to most electrolytes or proteins
- ECF: high in Na+, Cl-, HCO3-
- ICF: high in K+, PO43- & organic anions, protein
What is responsible for the distribution of Na+ & K+ btwn ECF & ICF?
What is the barrier?
-
Na+/K+ ATPase
- 3 Na+ out, 2 K+ in
- Barrier: cell membrane
- Distribution governed by osmotic forces
What is the definition of osmolarity?
- A function of the total number of particles in solution, independent of mass, charge or chemical composition
- The concentration of osmotically active particles in total solution
- Expressed in mOsm/L of water
Osmolarity
For substances that do not dissociate into smaller particles when dissolved….
For substances that dissolve into 2 particles or 3 particles…..
- For substances that do not dissociate into smaller particles when dissolved
- 1 mmole = 1 mOsm
- For substances that dissolve into 2 or 3 particles, the osmolarity will be double or triple the molarity
- 1 mmole NaCl = 2 mOsm
What is the definition of osmosis?
- The movement of water across a semi-permeable membrane due to differences in osmolarity (osmotic pressure gradient)
- A 1 mOsm/L difference in osmolarity can exert an osmotic pressure equivalent to 19.3 mmHg
What is the influence of adding isotonic, hypotonic and hypertonic NaCl solutions to the ECF on TBW, ECFV & ICFV?
What is a common pneumonic used when determining a differential diagnosis?
IPINGII
- Infection, infestation
- Physical/traumatic
- Immune
- Neoplastic
- Genetic/metabolic
- Iatrogenic
- Idiopathic
What are some changes related to aging that affect pharmacokinetics of drugs?
- Decreased body water
- Decreased lean body mass
- Increased body fat
- Decreased serum albumin
- Decreased kidney weight
- Decreased hepatic blood flow
Which of the following medications should be avoided as hyponotics in older patients?
- Diazepam
- Flurazepam
- Oxazepam
- Lorazepam
Diazepam, Flurazepam
- Phase I hepatic metabolism affected by aging
- Phase II hepatic metabolism NOT affected by aging (Oxazepam, Lorazepam)
In which drugs is there an age-related decreased in hepatic clearance?
- Alprazolam
- Barbiturates
- Carbenoxolone
- Chlordiazepoxide
- Chlormethiazole
- Clobazam
- Desmethyldiazepam
- Diazepam
- Flurazepam
- Imipramine
- Meperidine
- Nortriptyline
- Phenylbutazone
- Propranolol
- Quinidine, quinine
- Theophylline
- Tolbutamide
In which drugs is there no age-related difference found in hepatic clearance?
- Ethanol
- Isoniazid
- Lidocaine
- Lorazepam
- Nitrazepam
- Oxazepam
- Prazosin
- Salicylate
- Warfarin
Describe Phase II hepatic metabolism
- Mediated by cytoplasmic enzymes
- Addition of water soluble moieties to drugs (acetylation, glucuronidation, sulfation, glycine conjugation)
- Not commonly altered with age
How does creatinine clearance change with age?
- GFR decreases with age
- Creatinine clearance decreases with age
- Total body production decreases with age
- However, serum concentration doesn’t change very much because you don’t make as much, it no longer reflects renal function
How is creatinine clearance calculated?
Cockgroft Gault Equation for Creatine Clearance
- For women, multiply by 0.85
What are the 4 kidney processes that determine the composition of urine?
- Filtration
- Reabsorption
- Secretion
- Excretion
You obtain the following experimental data from a 70 kg male subject: UFR = 1.0 ml/min, PIN = 1.0 mg/ml, PPAH = 1.0 mg/ml, UIN = 60 mg/ml, UPAH = 650 mg/ml, Hct = 50%. What is this individual’s GFR?
- 30 ml/min
- 60 ml/min
- 120 ml/min
- 650 ml/min
- 1300 ml/min
60 ml/min
- GFR = [UFR*UIN]/PIN
- GFR = [(1 ml/min)(60 mg/ml)]/(1.0 mg/ml)
- GFR = 60 ml/min
What is the definition of mass balance for the kidney?
For the nephron?
renal arterial input = urine output + renal venous & lymphatic output
filtered + secretion = reabsorption + excretion
How is inulin filtered through the kidney?
How can this be used to estimate GFR?
- Inulin is freely filtered at the glomerulus but is not reabsorbed or secreted
- Filtration of inulin = excretion of inulin
- GFR x PIN = UF x UIN
- GFR = (UF x UIN)/PIN
What is the definition of clearance?
How is it calculated?
- The volume of plasma from which a substance has been removed & excreted into the urine per unit of time (volume/time)
- CX = (UF*UX)/PX
- Clearance of creatinine can be used to measure GFR with an endogenous compound
A normal individual receives a drug that effectively halves his glomerular filtration rate. After a period of 2 wks on this drug, this patient will have ______ plasma creatinine concentration, _______ creatinine clearance rate, and _________ creatinine excretion rate compared
