Fluid and Electrolytes

Question 1

Hyponatremia: serum sodium <130 mEq/L

Answer 1

Causes: bladder irrigations, TURP syndrome (dilutional hyponatremia), SIADH
Symptoms: confusion, nausea and vomiting, headache, seizure, coma if <115 mEq/L

Question 2

Hypernatremia: serum sodium <145 mEq/L

Answer 2

Causes: excess salt from water losses, lack of ADH (DI)
Symptoms: thirst, dry, sticky tongue, flushed skin, hypotension, oliguria, elevated temperature, seizures, coma if extreme

Question 3

Bicarbonate (HCO3-) normal: 22-28 mEq/L
Has reciprocal relationship with Cl-
If Cl- is depleted, HCO3- increases

Answer 3

Metabolic Alkalosis:
pH > 7.45
Causes: acid loss/HCO3- gain from N/V, increased GI suction
Patient hypoventilates
Hypokalemia

Metabolic Acidosis:
pH <7.35
Causes: acid gain/HCO3- loss from renal failure, DKA
Patient hyperventilates
Hyperkalemia

Question 4

Hypokalemia: K+ <3.5 mEq/L

Answer 4

Causes: diuretics, diarrhea, N/V, digitalis, bowel prep
Symptoms: muscle weakness, flaccid paralysis
Cardiac arrhythmias: more PVCs, U wave classic, conduction blocks
Treatment: 10 mEq/h peripheral IV; 20 mEq/h via central line; never push IV potassium!

Question 5

Hyperkalemia: serum K+ > 5.0 mEq/L

Answer 5

Causes: tissue lysis, DKA, renal failure, malignant hyperthermia
Symptoms: muscle weakness, paralysis
Cardiac arrhythmias: peaked T waves, wide QRS, asystole
Treatment: insulin with glucose, bicarbonate, and calcium to push K+ back into the cells
Dialysis for renal patients

Question 6

Hypomagnesemia: <1.5 mEq/L

Answer 6

Causes: diarrhea, malabsorption, N/V, increased aldosterone
Symptoms: neuromuscular irritability and seizures
Cardiac: long PR interval, wide QRS, flat T wave, risk of Torsades

Question 7

Hypermagnesemia: >2.5 mEq/L.
Magnesium promotes acetylcholine release from neuromuscular junction. Regulates K+. Opposes Ca+

Answer 7

Causes: magnesium sulfate infusion (eclampsia), ketoacidosis, chronic renal failure
Symptoms: CNS depression, sedation, muscle weakness, and decreased reflexes
Decreased BP and HR

Question 8

Hypocalcemia: < 4.5-5.3 mEq/L
Calcium has an inverse relationship with phosphate. If phosphate increases, calcium decreases.

Answer 8

Causes: low albumin, renal failure, hypoparathyroidism
Symptoms: tingling/weakness, twitching/tetany, low BP, ECG changes, positive Trosseau, positive Christel (facial twitching)
Postoperative laryngospasm

Question 9

Renin-Angiotensin-Aldosterone System

Answer 9

Renin: released by the kidneys in response to hypoperfusion of the kidneys. Converts angiotensinogen (produced by the liver) to angiotensin I.
Angiotensin-converting enzyme (produced by the lungs) converts angiotensin I to angiotensin II.
Angiotensin II causes aldosterone to be released by the adrenal cortex leading to sodium and water retention by renal tubules.

Question 10

Blood Loss Replacement

Answer 10

Blood loss replaced 3 ml crystalloid for each 1 ml of blood loss (3:1 rule)
Blood loss replaced 1 ml colloid or blood solution for each 1 ml blood loss

Question 11

Fluid Replacement for Pediatric Patient

Answer 11

0-10 kg: 4 ml/kg/h for each kg body weight
10-20 kg: 40 ml bolus + 2 ml/kg/h for each kg >10 kg
>20 kg: 60 ml bolus + 1 ml/kg/h for each kg >20 kg