Pharmacology in Special Populations Flashcards
What percentage of the elderly account for prescription medication use?
30%
What population consumes roughly 40% of all over the counter medications?
Elderly
On average, what percentage of the elderly take more than 10 medications?
19%
What two factors make the elderly more prone to adverse reactions to medications?
Less organ reserve and polypharmacy
What factor changes the volume of distribution in the elderly?
More fat and less body water content
What is the approximate rate at which the kidneys are functioning in patients older than 60?
Functioning at about 80%
What is the approximate rate at which the liver is functioning in patients older than 60?
55-60% hindering the ability to metabolize drugs
What considerations should be made when formulating an anesthetic plan for an elderly patient?
Meticulous preoperative assessment
Detailed management of intraoperative variables and disease states
Cautious titration of drug administration and dosages
What organ function and considerations should be inferred with the elderly?
HTN = cardiac issues
Hx smoking = lung issues
decreased mobility = decrease muscle mass
age = renal insufficiency
May have decrease circ time and decrease responsiveness to the BBB = be PATIENT
What is thought to be the reason for age related increases in pharmacodynamic sensitivity to anesthesia agents?
Declining neuronal function (oxidative stress or mitochondrial mutation)
What are some correlations with the elderly and use of of IV agents?
Longer half lives
30% decrease dose
Increased brain sensitivity to narcotics
Plasma drug concentration are higher after IV dose given
What is the rule of thumb with opioid in the elderly patient?
Opioid requirements are inversely related to patients age and essentially independent of body size
What type of local anesthetic block is higher in the elderly if a fixed dose and volume is used?
The sensory level of the block is higher in the elderly
What type of epidural dosing is reduced in the elderly?
Segmented dosing are reduced with aging
What can occur with neurogenic atrophy of the neuromuscular junction in the elderly?
Proliferation of extra-junctional cholinorecptors (be mindful of Succs use)
How is the effect and the duration of NMBA affected in the elderly patient?
Maximal effect is delayed and the duration of action is extended (metabolism/elimination)
How is reversal affected in the elderly patient?
Antagonism remains unchanged
What is one of the most common post op complications in the elderly patient?
Post op delirium
Why might the BIS monitor be a useful tool to used in the elderly?
Helps to gauge anesthetic level, giving fewer or lower doses will reduce postoperative delirium compared with deeper sedation
What drugs are known to induce post operative delirium in the elderly?
Anticholinergics Corticosteroids Meperidine Hypnotics The use of five or more medications increases the risk for delirium
What method of anesthesia can be delivered to patient to elderly patients in pain in order to avoid delirium?
Regional anesthesia
What is the rule of thumb for providers treating post op delirium?
Use the lowest effective dose of benzos and antipsychotics doe the shortest duration and only after behavioral interventions have failed
What factors influence drugs in an obese patient?
Difference in tissue distribution Hemodynamics Blood flow to tissue types (a lot of fat blood flow can shift from organs to adipose tissue) Plasma composition Liver and kidney function
How do we determine if a drug should be dosed on ideal body weight or total body weight?
IBW for drugs that are preferential to lean tissue
TBW for drugs with equal distribution to lean and adipose tissue
What weight should thiopental be dosed on?
IBW, prolongs the duration of action and half life
What weight should Propofol be dosed on?
TBW
What weight should Versed be dosed on?
Loading dose (TBW) Maintenance (IBW) Sedative effects correlate better to larger VD and less to elimination
What weight should dexmedetomidine be dosed on?
TBW, does not effect respirations (preferred for analgesic qualities)
What weight should Succinylcholine be dosed on?
TBW, pseudocholinesterase activity increases with weight
What weight should Roc/Vec be dosed on?
IBW, prolonged DOA with TBW
What weight should Atracurium be dosed on
TBW, organic independent elimination
What weight should Cisatracurium be dosed on?
IBW, increase DOA seen with TBW dosing
What weight should Fentanyl dosed on?
Inconclusive, TBW overestimates the dose
What weight should Sufententanil be dosed on?
Loading dose TBW
Maintenance IBW
What weight should Remifentanil be dosed on?
IBW, kinetics not effected by weight
How do you calculate ideal body weight?
Male: 105 + 6lbs for every inch > 5ft
Female: 100 + 5lbs for every inch >5ft
What is a disadvantage to administering children drugs via the rectal route?
The onset is slow and the drug effects can be unpredictable
What route of administration is not recommended in pediatrics?
IM due to pain that can last for days (low muscle mass)
What major factor may allow older children a higher dose of medications than adults?
They have a greater concentration of albumin and AAG than adults
In infants, what substance can displace drugs from proteins altering drug concentration?
Bilirubin
What type of drugs may require higher doses in neonates and infants?
Water soluble drugs
What factor in neonates and infants allows rapid uptake of anesthetics into the CNS?
They have immature BBB making it more permeable
What is an infants GFR at birth?
40mL/min
What will an infants GFR increase to at 1yr old?
100mL/min (most profound change over a short period of time)
What are the three checkpoints in the cell cycle?
Cell growth checkpoint
DNA synthesis checkpoint
Mitosis checkpoint
When does the cell growth checkpoint occur?
Toward the end of growth phase 1 (G1)
When does DNA synthesis checkpoint occur?
Occurs during the synthesis phase (S)
When does the mitosis checkpoint occur?
Occurs during the mitosis phase (M)
What is being checked in the cell growth checkpoint?
Whether the cell is big enough and has made the proper proteins for the synthesis phase
What occurs if a cell does not pass the cell growth checkpoint?
The cell goes through a resting period (G0) until it is ready to divide
What is being checked in the DNA synthesis checkpoint?
Whether the DNA has been replicated correctly, if so it continues to the mitosis phase
What being checked at the mitosis checkpoint?
Checks if mitosis is complete, if so the cell divides and the cycle repeats
What should be assumed about all patients receiving chemotherapy?
All patients will have nausea and vomiting, hair loss and altered blood counts
If a patient has a history of using chemotherapy, what should be the anesthetists main concern?
The patient’s organ functions (CV, pulmonary and hepatic)
What major toxicities are seen with cisplatin use?
Nephrotoxicities
Peripheral neuropathy
Nerve dysfunction
What major toxicities are seen with methotrexate use?
Myelosuppression with neutropenia and thrombocytopenia
What major toxicities are seen with bleomycin use?
Pulmonary fibrosis
What major toxicities are seen with doxorubicin use?
Cardiotoxicity and myelosuppression
What major toxicities are seen with cetuximab use?
Interstitial lung disease
How do volatiles, barbiturates and ketamine affect cancer cell activity?
They suppress NK cell activity and can promote cancer cell mets
How can nitrous oxide affect cancer cell activity?
It reduces purine and thus reducing DNA synthesis
Suppresses neutrophil chemotaxis
Potentially facilitates the spread of cancer
How can propofol affect cancer cell activity?
It seems to exhibit protective effects through various mechanisms, including an anti-inflammatory effect, inhibition of COX-2 and reduction of PGE-2, weak beta-adrenoreceptor binding, enhancement of anti tumor immunity and NK function preservation
How can opioids affect cancer cell activity?
May produce cellular and humoral immunosuppression, specifically morphine
How can local anesthetics affect cancer cell activity?
They have been shown to reduce metastatic burden
How is the ED50 of NMBA affected in the elderly?
They have a higher ED50 from increased density of receptors at the muscle endplate
What three factors determine the passage of the drug across the placenta?
Lipid solubility, molecular weight of the drug and the degree of drug ionization
At what molecular weight can a drug easily cross the placenta?
250-500
At what molecular weight can a drug cross the placenta with a little more difficulty?
500-1000
At what molecular weight does a drug very poorly cross the placenta?
> 1000
How do drugs that cross the placenta enter fetal circulation?
Through the umbilical vein
What is perinatal pharmacology?
Drug administration to the pregnant woman with the fetus as the intended target of the drug
Why must drug administration must be done cautiously in a neonate that is jaundiced?
Drugs can displace bilirubin from albumin causing Kernicterus (brain damage)
What is the difference between an elixir and a suspension?
An elixir solution has particles that are dissolved throughout where a suspension contains undissolved particles which could cause different dosing if not shaken properly
What is the most common reason for medication errors in the pediatric population?
Incorrect calculations and incorrect placement the decimal point
What factors cause a decrease in use of volatiles in elderly patients?
Reduced respiratory capacity and active pulmonary disease
Why is it important to assess the elderly taking antihypertensives frequently for orthostatic hypotension?
Danger of cerebral ischemia and falls
What is the most common cause of blindness in the elderly?
Age related macular degeneration
What is drug non adherence usually due to in the elderly?
Forgetfulness, especially if the patient has several drugs and different dosing intervals
