NMS. Surgery

2

Part I ♦ Foundations

If You Hear/See

Think

Partial thromboplastin time Reflects intrinsic pathway Spontaneous bleeding

Platelet dysfunction or thrombocytopenia

Nutritional supplements Use the gut first Increased work of breathing Intubate early Shock

Inadequate oxygen delivery relative to demand

Septic shock

Norepinephrine

Nitroprusside

Cyanide toxicity

FLUID AND ELECTROLYTES Normal Body Composition I. Body water: Water accounts for 50%–70% of total body weight (Fig. 1-1) and is higher in young people, thin people, and men. A. Two-thirds rule: Total body water comprises about two thirds of body weight. B. Plasma volume: ~5% of body weight is plasma volume (e.g., 3.5 L of plasma for a 70 kg male). Plasma is ~60% of the blood volume if the hematocrit is 40% (e.g., 5.8 L of blood for a 70 kg male). II. Electrolyte composition: Electrolyte concentrations differ between intracellular and extracellular compartments due to ion pumps, principally Na + /K + ATPase (Table 1-1). Osmotic pressure changes between compartments causes water to redistribute. A. Intracellular compartment: The principle osmotic cation is potassium. The concentration of osmotic and oncotic (protein) particles is higher than the extracellular compartment, thus allowing water to flow into the cell creating turgidity. B. Extracellular compartment: The principle osmotic cation is sodium. Interstitial and plasma composition is nearly equal. Water and Electrolyte Maintenance I. Water: Required amount depends on the person’s weight, age, gender, and health. A. Water calculation methods 1. Amount of body water excreted a. Most water lost from the body is through urine production. Generally, 0.5 mL/kg/hr is the minimum needed to excrete the daily solute load. b. The next highest daily water loss is from insensible losses (i.e., sweat, respiration, stool). This is estimated at 600–900 mL/24 hr.