Pharmacology in ICU

Question 1

what do you need to consider before administering medications to ICU patients?

Answer 1

• patient’s:
  
  • V_d
  • total protein
  • hepatic and kidney function
• drug’s:
  
  • therapeutic index
  • solubility
  • protein binding
  • tissue permeability

Question 2

how does hypovolemic shock affect V_d?

Answer 2

• reduces V_d
• decreased peripheral perfusion, increased central perfusion

Question 3

how does distributive shock affect V_d?

Answer 3

• increases V_d
• septic shock most common
• aggressive fluid therapy-> edematous -> increased vascular permeability and V_d

Question 4

calculation for modifying dose based on V_d

Answer 4

loading dose = standard loading dose x (patient’s V_d/normal V_d)

Question 5

how is the solubility of a drug affected in hypovolemic vs. distributive shock?

Answer 5

• hypovolemic shock (decreased V_d)
  
  • liposoluble drug: no change in C_max (goes everywhere)
  • hydrosoluble drug: increased of C_max (stays in blood)
• distributive shock (increased V_d)
  
  • liposoluble drug: no change in C_max
  • hydrosoluble durg: drop in C_max

Question 6

effects of protein binding

Answer 6

• decreases total effective free drug available in plasma
• drugs are usually highly protein bound

Question 7

ICU patients and protein binding

Answer 7

• patients in ICU are frequently hypoproteinemic with low albumin
  
  • low oncotic P due to decreased protein and increased vascular fluid loss (decreased V_d)
  • allows for higher amount of free drug (OD)
• must pay close attention to albumin and total protein levels (reduce drugs accordingly)

Question 8

how does a drug’s therapeutic index need to be considered in ICU?

Answer 8

• high therapeutic index: safe at a wider range
  
  • usually is not a problem
• low therapeutic index, be careful!
  
  • aminoglycosides, barbiurates, abx, digoxin

Question 9

effects of patient’s status on metabolism/elimination of drugs?

Answer 9

• liver failure (metabolism) and/or kidney disease (elimination), reduce dose and increase frequency
• anesthetized patients have reduced hepatic BF and decreased metabolism
• patient’s have increased risk of organ failure, prone to low clearance

Question 10

calculations for dose based on liver/kidney function

Answer 10

maintenance dose = standard dose x (patient’s CrCl/normal CrCl)

or

maintenance dosing interval = standard dosing interval x (normal CrCl/patient’s CrCl)

Cr = Creatinine Cl = clearance