6 Fluids and Electrolytes, part 2

Question 1

Hypokalemia most commonly occurs secondary to

Answer 1

profuse vomiting and/or diarrhea

Question 2

IV replacement of potassium

Answer 2

If IV therapy is necessary, potassium 0.2 to 0.3 mEq/kg/h is generally adequate

In extremely urgent situations, such as hypokalemia-induced respiratory insufficiency or cardiac manifestations, potassium 0.5 mEq/kg/hour can be adminsitered (maximum 20 mEq/dose), with continuous ECG monitoring

If potassium chloride infusion conentration exceeds 60 mEqs/L, the infusion will need to run through a central line, because potassium is a vein irritant

Question 3

Potassium levels in DKA

Answer 3

In diabeteic ketoacidosis profound hypokalemia can result from osmotic diuresis, although in the face of the hydrogen-potassium shift that accompanies acidemia, serum levels may be normal or falsely elevated

In DKA, potassium repletion should begin early in the course of therapy, because diuresis-induced depletion can result in profound hypokalemia as acidosis is corrected and serum potassium shifts into cells.

Question 4

Most common manifestation of hyperkalemia

Answer 4

Cardiac conduction delay is the most common manifestation of hyperkalemia and is potentially life threatening

• Peaked T waves are the first manifestation
• followed by prolonged PR interval
• and then widening of the QRS complex, an ominous finding that can precede the
• characteristic “sine wave” pattern, leading to
• ventricular dysrhythmias and asystole

Question 5

Dosing of 10% calcium gluconate

Answer 5

100 mg/kg (1mL/kg/dose) IV at a rate not to exceed 100 mg/min
10% means 100mg/mL

maximum of 3 grams per dose
may be repeated in 5 mins if necessary

Question 6

remarks on calcium chloride

Answer 6

max 1 gram per dose
must be given via central line or IO due to vein sclerosis
may be repeated in 5 mins if necessary

Question 7

sodium bicarbonate in hyperkalemia

Answer 7

if acidotic (pH <7.3), 1-2 mEq/kg IV
typical adult dose 50-100 mEq
may be repeated every 5-10 mins as needed

In patients with hyperkalemia secondary to metabolic acidosis, normalization of serum pH usually restores serum potassium to normal levels.

Question 8

Definition of hypocalcemia

Answer 8

< 8 mg/dL
<2 mmol/L
ionized Ca <4.4 mg/dL
ionized Ca <1.1 mmol/L

Question 9

Another common cause of hypocalcemia is

Answer 9

hyperventilation:
the decreased partial pressure of carbon dioxide results in an acute respiratory alkalosis that rapidly decreases levels of ionized calcium

Question 10

The most characteristic ECG abnormality in hypocalcemia is

Answer 10

a prolonged QT interval.

Question 11

If a neonate is seen with hypocalcemia, a ____________ should be done to look for a thymic shadow in infants and young children.

Answer 11

chest radiograph

Question 12

Treatment of hypocalcemia

Answer 12

calcium gluconate 10% in a dose fo 100 mg/kg at a rate not to exceed 100mg/min, with continuous ECG monitoring.

Question 13

definition of hypercalcemia

Answer 13

> 11 mg/dL

Question 14

Probably the most common cause of hypercalcemia in children is

Answer 14

malignancy involving the lymphoreticular system.

Question 15

hypercalcemia can cause

Answer 15

constipation

Question 16

Treatment of hypercalcemia

Answer 16

Treatment depends on the cause.

Acutely, patients with functioning kidneys can be treated with aggressive IV hydration (e.g., twice maintenance), with or without furosemide, 1 to 2 mg/kg IV, to a maximum of 40 mg. Then, treat the underlying cause.

Question 17

Clinical manifestations of hypomagnesemia

Answer 17

Clinical manifestations are similar to those seen with hypocalcemia:
* muscle spasms, weakness, or even atrophy may occur
* CNS symptoms include ataxia, abnormal movements, nystagmus, and seizures
* cardiac changes include prolonged pR and QT intervals and may predispose to arrhythmias such as torsades de pointes

Question 18

treatment of hypomagnesemia

Answer 18

In symptomatic patietns (e.g., those with seizures, arrhytmias), give IV magnesium sulfate, 25 to 50 mg/kg administered as a 10% solution over 30 minutes, and repeat every 4 to 6 horus as needed

Question 19

most common cause of hypermagnesemia

Answer 19

The most common cause is ingestion of exogenous magnesium, typically found in antacids and laxatives.
* Patients with renal dysfunction are at increased risk

Question 20

clinical manifestations of hypermagnesemia

Answer 20

Clinical manifestations include hypotension, loss of deep tendon reflexes, and respiratory failure

Cardiac manifestsions include widening of the QRS, PR, and QT intervals

Question 21

treatment of hypermagnesemia

Answer 21

Treatment is removal of exogenous sources and hydration accompanied by diuresis.

Severe symptoms may be mitigated with IV calcium, 0.5 mL/kg delivered as calcium gluconate.
* dialysis is effective in patients with renal failure