0.5 to 1.0 L/h

Name the sources and the amount of normal daily electrolyte loss:

Chloride: 150 mEq, sodium: 100 mEq, potassium: 100 mEq

Name the sources and the amount of daily secretions:

Saliva: ~1500 cc/24 h

Gastric: ~2000 cc/24 h

Small intestine: ~3000 cc/24 h

Bile: ~1000 cc/24 h

Pancreatic: ~600 cc/24 h

State the electrolyte composition of sweat:

30 to 50 mEq sodium, 5 mEq potassium, 45 to 55 mEq hydrogen

State the electrolyte composition of gastric secretions:

40 to 65 mEq sodium, 90 mEq hydrogen, 100 to 140 mEq chloride

State the electrolyte composition of biliary secretions:

135 to 155 mEq sodium, 5 mEq potassium, 80 to 110 mEq chloride, 70 to 90 mEq bicarbonate

State the electrolyte composition of pancreatic secretions:

135 to 155 mEq sodium, 5 mEq potassium, 55 to 75 mEq chloride, 70 to 90 mEq bicarbonate

State the electrolyte composition of ileostomy output:

120 to 130 mEq sodium, 10 mEq potassium, 50 to 60 mEq chloride, 50 to 70 mEq bicarbonate

State the electrolyte composition of diarrhea:

25 to 50 mEq sodium, 35 to 60 mEq potassium, 20 to 40 mEq chloride, 30 to 45 mEq bicarbonate

Define the “third space.”

Fluid accumulation in the interstitium of tissues (first 2 spaces: intravascular and intracellular)

When does third-spaced fluid tend to mobilize back into the intravascular space?

Postoperative day #3

What is the earliest sign of volume excess during the postoperative period?

Weight gain

Classic finding with overaggressive nasogastric tube suctioning or long-standing vomiting:

Hypokalemic hypochloremic metabolic alkalosis

Name the various mechanisms that loop diuretics employ to decrease pulmonary edema:

Inhibit active sodium absorption in the thick ascending loop of Henle, increase venous capacitance, stimulate vasodilatory prostaglandins leading to increased renal blood flow

2 × sodium + urea/2.8 + glucose/18

How much sodium and chloride are in normal saline?

154 mEq Na⁺ and 154 mEq Cl^–

Composition of lactated Ringer’s:

130 mEq Na⁺, 109 mEq Cl^–, 4 mEq K⁺, 28 mEq lactate, and 3 mEq calcium

How many grams of dextrose in a liter of D5W?

50 g; D5W is a 5% solution of dextrose (5 g dextrose/100 cc × 1000 cc/1 L = 50 g dextrose)

The 2 “rules” for the calculation of maintenance fluids:

100/50/20 rule and 4/2/1 rule; for both rules cc/kg for first 10 kg/cc/kg for next 10 kg/cc/kg for every kg >20 kg

Name the standard maintenance fluid used in an adult:

D5 1/2 normal saline (NS) with 20 mEq KCl

Name the standard maintenance fluid used in a pediatric patient:

D5 1/4 NS with 20 mEq KCl

Usual minimal urine output for an adult:

~30 mL/h or 0.5 mL/kg/h

How much of a 1-L NS bolus will stay intravascular in a 5-hour period?

~200 cc or 20%

ELECTROLYTES

Normal range for sodium:

135 to 145 mEq/L

Define pseudohyponatremia and list causes:

Spuriously low lab result for sodium; hyperglycemia, hyperlipidemia, hyperproteinemia

Name the 3 types of hyponatremia:

Hypovolemic, euvolemic, hypervolemic

Name surgical causes of hypovolemic hyponatremia:

Burns, diaphoresis, diuretics, hypoaldosteronism, NG suctioning, pancreatitis, vomiting

Name surgical causes of euvolemic hyponatremia:

CNS abnormalities, drugs, syndrome of inappropriate secretion of antidiuretic hormone (SIADH)

Name surgical causes of hypervolemic hyponatremia:

Congestive heart failure, cirrhosis, iatrogenic, renal failure

Signs and symptoms of hyponatremia:

Coma/confusion, ileus, lethargy, nausea/vomiting, seizure, weakness

Treatment of hypovolemic hyponatremia:

Correct the underlying cause, give IV NS

Treatment of euvolemic hyponatremia (SIADH):

Acute treatment with furosemide and normal saline; fluid restriction

Fluid restriction and diuretics

Grave consequence of correcting hyponatremia too quickly:

Myelinolysis (formerly known as central pontine myelinolysis)

Formula to calculate the sodium deficit:

(normal sodium concentration – observed sodium concentration) × total body water; Remember: total body water = 0.6 × weight (kg)

Approximately how much does the apparent serum sodium concentration fall for each 100 mg/dL rise in blood glucose level above normal?

1.6 to 3.0 mEq/L

Maximal rate of sodium correction for acute hyponatremia:

1 to 2 mEq/L/h for 3 to 4 hours until neurologic symptoms subside or until plasma Na is >120 mEq/L

Maximal rate of sodium correction for chronic hyponatremia:

0.5 to 1 mEq/L/h or no faster than 10 to 12 mEq/L in the first 24 hours and 18 mEq/L in the first 48 hours

Name surgical causes of hypernatremia:

Dehydration, diabetes insipidus, diaphoresis, diarrhea, diuresis, iatrogenic, vomiting

Signs and symptoms of hypernatremia:

Confusion, peripheral/pulmonary edema, respiratory paralysis, stupor, seizures, tremors

Treatment of hypernatremia:

Slow supplementation of 1/4 NS or 1/2 NS over days

Formula to calculate the free water deficit:

Total free water deficit = 0.6 × weight (kg) × [(Serum Na⁺/140) – 1]

What is the normal range for potassium:

3.5 to 5.0 mEq/L

Critical values for potassium:

K⁺ <2.8 mEq/L or >6.0 mEq/L

Name some surgical causes of hypokalemia:

Alkalosis, diuretics, drugs (steroids/antibiotics), diarrhea, iatrogenic, insulin, intestinal fistula, NG suctioning, vomiting

Signs and symptoms of hypokalemia:

Ileus, weakness, tetany, nausea/vomiting, paresthesia

EKG findings of hypokalemia:

Flattened T waves, U waves, ST segment depression, atrial fibrillation, premature atrial complexes/premature ventricular complexes

Acute treatment for hypokalemia:

IV KCl

Maximum amount of potassium that can be administered through a peripheral IV:

10 mEq/h

Hypokalemia

Name surgical causes of hyperkalemia:

Iatrogenic, diuretics, acidosis, trauma, hemolysis, renal failure, blood transfusion

Signs and symptoms of hyperkalemia:

Areflexia or decreased deep tendon reflexes, paresthesia, paralysis, weakness, and respiratory failure

EKG findings of hyperkalemia:

Peaked T waves, prolonged PR, wide QRS, depressed ST segment, ventricular fibrillation, bradycardia

What is the treatment for hyperkalemia?

IV calcium, sodium bicarbonate, dextrose and insulin (1 amp 50% dextrose and 10 U insulin), albuterol, kayexalate, furosemide, dialysis

Most of the calcium in the body is contained within:

Bone

Percentage of serum calcium that is nonionized and bound to plasma protein:

~50%

Percentage of serum calcium that is nonionized and bound to substances other than plasma protein in the plasma:

5%

How much does a 1-g drop in protein decrease the measured total serum calcium?

0.8 mg/dL