NMS. Surgery

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Part I ♦ Foundations 2. Water maintenance a. Adult patients: (70 kg × 0.5 mL/kg/hr × 24 hr) + (750 mL/24 hr) = 1,590 mL/24 hr. b. Pediatric patients: 4 mL/kg/hr for the first 10 kg of body weight, 2 mL/kg/hr for the second 10 kg of body weight, and 1 mL/kg/hr for each additional kilogram of body weight. B. Evaluating maintenance rates: 1. Monitor urine output: If urine output is low (i.e., <0.5 mL/kg/hr), then more water may be required. 2. Monitor heart rate: Tachycardia can be a sign of low intravascular volume. C. Adjusting fluid rates and types for individual patients: First, calculate the patient’s maintenance rate, and then adjust the amount up or down based on the need for resuscitation and the replacement of gastrointestinal (GI) losses. Adjust the type of fluid based on the type of losses (Table 1-2). 1. Injury, illness, and surgery: These may result in fluid losses due to blood loss, third spacing, insensible losses from diarrhea, fever, etc. It may be necessary to provide more than calculated maintenance fluid to replace losses. 2. Hypervolemia and diuresis: Patients who require diuresis are often overloaded with fluid. In these instances, intravenous (IV) fluids should be limited. II. Sodium: 150–200 mEq/day of sodium is typically consumed; most is excreted in the urine. A. If the body needs to conserve sodium, then it can reduce renal excretion to less than 1 mEq/day. B. Daily homeostasis is easily maintained with 1–2 mEq/kg/day. III. Potassium: The normal daily intake of potassium is ~40–120 mEq/day. 10%–15% is excreted in the urine, and 0.5–1 mEq/kg/day is appropriate to maintain homeostasis.

Table 1-2: Electrolyte Composition of Gastrointestinal Secretions

HCO 3 − (mEq/L)

Volume/ day Na + (mEq/L) K + (mEq/L) Cl − (mEq/L)

Organ

Stomach 1–5 L

20–150

10–20 10–20

120–140

Nil

Duodenum 0.1–2 L 100–120

110

10–20 30–50 30–50

Ileum 1–3 L

80–140

5–10

60–90

Colon

0.1–2 L 100–120

10–30

90

Gallbladder 0.5–1 L 140 Pancreas 0.5–1 L 140

5 5

100

25

30 (higher when not stimulated)

115 (lower when not stimulated)