Fluids and Pressors Flashcards
In someone with septic shock, __ is the preferred fluid.
In someone with septic shock, a mixture of albumin and normal saline is the preferred fluid.
You need some colloid to keep fluids within the intravascular space.
Isotonic saline, given in high enough quantities, is associated with. . .
. . . a non-anion gap, hyperchloremic metabolic acidosis
Two uses for hypertonic fluids
- Expanding the IVC in patients with hypovolemic shock as a means of low-volume, high-impact resuscitation.
- Pulling water out of the intracellular space to reduce ICP in the neurologic critical care setting.
Two indications for stress-dose steroids
- Hypotesion that remains unresponsive to adequate fluid resuscitation and vasopressor therapy
- Concern for underlying relative or absolute adrenal insufficiency
Vasopressors should be administered. . .
. . . into large veins
Usually involving a central venous line.
Most commonly used vasopressors and indications
Vasopressors are used to raise ___.
Positive inotropes are used to raise ___.
Vasopressors are used to raise MAP.
Positive inotropes are used to raise cardiac output, cardiac index, stroke volue, and SvO2.
Who gets dobutamine?
Patients with refractory CHF or refractory hypotension
Dobutamine vs dopamine
Dobutamine has less of an effect on HR than dopamine
But, dobutamine is more effective in sphlanchnic resuscitation, increasing pH, and improving mucosal perfusion compared to dopamine.
Low-dose dopamine
Low-dose dopamine in amounts < 10 microgram/kg/min has primarily beta adrenergic agonist effects.
It is converted to norepinephrine in the myocardium and activates adrenergic receptors.
High-dose dopamine
High-dose dopamine sensitizes alpha-adrenergic receptors to cause vasoconstriction
Generally greater than 20 micrograms/kg/hour
Dopamine over-all
Overall, dopamine is a mixed inotrope and vasoconstrictor (with preferential inotropic effects at low doses)
At all doses, it is a potent chronotropic agent. This makes it likely to cause tachycardia, and makes it more arrhythmogenic than norepinephrine.
Dopamine-resistant septic shock
Septic shock in which administration of high-dose dopamine at 20 micrograms/kg/min fails to raise MAP above 70 mmHg.
These patients have a mortality rate of 78%, compared to 16% in the dopamine-sensitive septic shock group.
Dosing of norepinephrine
Maintenance dose of 2-4 micrograms/minute
May require much higher doses in patients with septic shock.
Norepinephrine for shock
Generally the 1st line vasopressor, particularly for septic shock.
Has both alpha and beta vasoconstricting effects that raise the MAP and has little to no effect on the heart rate.
Less metabolically active than epinephrine, which raises blood glucose and lactate levels.
Epinephrine as a vasopressor
Has potent beta1, beta2, and alpha1 activity. Superior inotrope when compared to norepinephrine.
There are several drawbacks to use of epinephrine as a vasopressor:
- Increase in myocardial oxygen demand
- Inrease in serum glucose and lactate
- Drop in serum potassium (intracellular shift)
- Reduces splanchnic bloodflow (redirecting bloodflow to skeletal muscle)
Phenylephrine as a vasopressor
An almost pure alpha-1 agonist
Commonly used in anesthesia to regulate hypotension induced by anesthetic agents. Its general efficacy in raising blood pressure is less than that of epinephrine or norepinephrine.
Since it has no beta activity, it does not intrinsically increase heart rate – and may reduce heart rate due to reflex bradycardia from elevated blood pressure.
Generally ineffective as a treatment in sepsis.
Vasopressin as a vasopressor
Generally reserved for when fluids, peripheral pressors, and positive inotropes fail to improve blood pressure.
It is especially useful in septic patients with hypotension that has become refractory to catecholamines.
Midodrine as a vasopressor
A peripheral selective alpha-1 adrenergic agonist
Indicated in the treatment of orthostatic hypotension and hypotension associated with liver failure/hepatorenal syndrome (along with 5% albumin resuscitation) and kidney failure.
Midodrine is both an arterial and venous vasopressor.
Levosimendan as a vasopressor
Acts by increasing cardiac troponin’s sensitivity to calcium – increasing the heart’s contractility without forcing a rise in intracellular calcium.
Has a unique combination of effects: Positive inotropy with decreased preload and decreased afterload.
Fast acting antihypertensives
Note: Hydralazine is a last-line agent. Too many complications.
Rate vs rhythm control in the ICU
Rate vs rhythm control and development of persistent afib
When used in the acute setting for new onset atrial fibrillation:
6% of pts with rate control have atrial fibrillation at 2 months
2% of pts with rhythm control have atrial fibrillation at 2 months.
Rhythm control interrupts the formation of atrial fibrillation circuits that cause chronic atrial fibrillation.
Rate control agents for atrial fibrillation
Contents of normal saline
154 mEq Na
154 mEq Cl
Dissolved air and plastic, resulting in acidic pH
Contents of lactated ringers
130 mEq Na
110 mEq Ca
4-5 mEq K
2 mEq Ca
28 mEq lactate
What happens to lactate in lactated ringers?
It goes to the liver to be converted to glucose
Typical labs in sepsis
Elevated lactate
Low bicarbonate
Elevated potassium (due to acidic pH)
Effects of LR and NS on potassium
LR: Brings potassium down by 1) dilution and 2) increase in pH
NS: Brings potassium up by increasing the pH
Why does NS cause a metabolic acidosis?
The answer depends on the fact that physiologic pH buffering does not exactly follow the Henderson-Hasselbalch equation, since the conjugate acid (CO2) is determined by the respiratory system.
When you add NS, you basically dilute HCO3 and CO2. But, the CO2 is rapidly replenished by the respiratory system while the HCO3 is not.
The result is filling of the volume that you added with CO2 while diluting the existing HCO3.
What is the best resuscitation fluid for septic shock?
Lactated ringers
It buffers the acidosis and reduces potassium.
When and how do you use D5W?
Basically only when there is hypernatremia
Should always be used with the free water deficit
Just use a clinical calculator, no need to memorize the formula
Best resuscitation fluid vs best maintenance fluid
Best resuscitation: Lactated ringers
Best maintenance: D5 NS with 20 mEq K
D5W + Bicarb
Dextrose, water, and 150 mM sodium bicarbonate
Because it is sodium bicarbonate, this is not a sodium-neutral fluid
Useful in patients with metabolic acidosis refractory to initial therapy. If you are giving someone this fluid, you should also be strongly considering dialysis for acidosis.
Fluid challenge in children
10 mL/kg over 10 minutes if stable hemodynamics
20 mL/kg over 10 minutes if unstable hemodynamics
Fluid challenge in adults
500 mL over 20 minutes if stable hemodynamics
1000 mL over 20 minutes if unstable hemodynamics
Rate of potassium administration
If potassium is administered too quickly, it may cause cardiac arrhythmia
Safe rates are:
< 10 mEq/hr via peripheral line
< 40 mEq/hr via central line
Holiday-Segar Equation for maintenance fluid
For children ages 1 month to 18 years, aka the 4-2-1 rule
4 mL/kg/hr for first 10 kg
2 mL/kg/hr for second 10 kg
1 mL/kg/hr for every kg thereafter
Maintenance fluid for neonates (full term)
- Birth - Day 1 50 mL/kg/day
- Day 2 60 mL/kg/day
- Day 3 70 mL/kg/day
- Day 4 80 mL/kg/day
- Day 5-28 120 mL/kg/day
Maintenance fluids in adults
1-2 mL/kg/hour
1 for older patients or patients with CV/renal risk factors
2 for young healthy patients
Here kg should really be ideal body weight – so don’t give someone who is very obese 300 mL/hour
The maintenance fluid requirement is higher per kilogram in. . .
. . . children than adults
