Fluids and Pressors

Question 1

In someone with septic shock, __ is the preferred fluid.

Answer 1

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.

Question 2

Isotonic saline, given in high enough quantities, is associated with. . .

Answer 2

. . . a non-anion gap, hyperchloremic metabolic acidosis

Question 3

Two uses for hypertonic fluids

Answer 3

• 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.

Question 4

Two indications for stress-dose steroids

Answer 4

1. Hypotesion that remains unresponsive to adequate fluid resuscitation and vasopressor therapy
2. Concern for underlying relative or absolute adrenal insufficiency

Question 5

Vasopressors should be administered. . .

Answer 5

. . . into large veins

Usually involving a central venous line.

Question 6

Most commonly used vasopressors and indications

Answer 6

Question 7

Vasopressors are used to raise ___.

Positive inotropes are used to raise ___.

Answer 7

Vasopressors are used to raise MAP.

Positive inotropes are used to raise cardiac output, cardiac index, stroke volue, and SvO₂.

Question 8

Who gets dobutamine?

Answer 8

Patients with refractory CHF or refractory hypotension

Question 9

Dobutamine vs dopamine

Answer 9

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.

Question 10

Low-dose dopamine

Answer 10

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.

Question 11

High-dose dopamine

Answer 11

High-dose dopamine sensitizes alpha-adrenergic receptors to cause vasoconstriction

Generally greater than 20 micrograms/kg/hour

Question 12

Dopamine over-all

Answer 12

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.

Question 13

Dopamine-resistant septic shock

Answer 13

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.

Question 14

Dosing of norepinephrine

Answer 14

Maintenance dose of 2-4 micrograms/minute

May require much higher doses in patients with septic shock.

Question 15

Norepinephrine for shock

Answer 15

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.

Question 16

Epinephrine as a vasopressor

Answer 16

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)

Question 17

Phenylephrine as a vasopressor

Answer 17

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.

Question 18

Vasopressin as a vasopressor

Answer 18

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.

Question 19

Midodrine as a vasopressor

Answer 19

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.

Question 20

Levosimendan as a vasopressor

Answer 20

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.

Question 21

Fast acting antihypertensives

Answer 21

Note: Hydralazine is a last-line agent. Too many complications.

Question 22

Rate vs rhythm control in the ICU

Answer 22

Question 23

Rate vs rhythm control and development of persistent afib

Answer 23

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.

Question 24

Rate control agents for atrial fibrillation

Answer 24

Question 25

Contents of normal saline

Answer 25

154 mEq Na

154 mEq Cl

Dissolved air and plastic, resulting in acidic pH

Question 26

Contents of lactated ringers

Answer 26

130 mEq Na

110 mEq Ca

4-5 mEq K

2 mEq Ca

28 mEq lactate

Question 27

What happens to lactate in lactated ringers?

Answer 27

It goes to the liver to be converted to glucose

Question 28

Typical labs in sepsis

Answer 28

Elevated lactate

Low bicarbonate

Elevated potassium (due to acidic pH)

Question 29

Effects of LR and NS on potassium

Answer 29

LR: Brings potassium down by 1) dilution and 2) increase in pH

NS: Brings potassium up by increasing the pH

Question 30

Why does NS cause a metabolic acidosis?

Answer 30

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.

Question 31

What is the best resuscitation fluid for septic shock?

Answer 31

Lactated ringers

It buffers the acidosis and reduces potassium.

Question 32

When and how do you use D5W?

Answer 32

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

Question 33

Best resuscitation fluid vs best maintenance fluid

Answer 33

Best resuscitation: Lactated ringers

Best maintenance: D5 NS with 20 mEq K

Question 34

D5W + Bicarb

Answer 34

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.

Question 35

Fluid challenge in children

Answer 35

10 mL/kg over 10 minutes if stable hemodynamics

20 mL/kg over 10 minutes if unstable hemodynamics

Question 36

Fluid challenge in adults

Answer 36

500 mL over 20 minutes if stable hemodynamics

1000 mL over 20 minutes if unstable hemodynamics

Question 37

Rate of potassium administration

Answer 37

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

Question 38

Holiday-Segar Equation for maintenance fluid

Answer 38

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

Question 39

Maintenance fluid for neonates (full term)

Answer 39

• 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

Question 40

Maintenance fluids in adults

Answer 40

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

Question 41

The maintenance fluid requirement is higher per kilogram in. . .

Answer 41

. . . children than adults