NMS. Surgery

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Part I ♦ Foundations b. Dobutamine: Primarily affects both the beta-1 and beta-2 receptors, increasing CO and vasodilatation; beneficial in cardiogenic shock, where increased CO and decreased SVR are sought. c. Norepinephrine: Strong alpha agonist that causes vasoconstriction with mild beta agonist activity that increases heart contractility; tachycardia is its major limiting effect. d. Epinephrine: Primarily, an alpha agonist with some beta agonist effect; useful for vasoconstriction and increasing CO; causes more tachycardia than norepinephrine. e. Phenylephrine: Alpha agonist that causes pure arterial constriction; not a very potent vasoconstrictor. f. Vasopressin: Acts on the V1 receptor in vascular smooth muscle. Add to norepinephrine as a second agent when needed. 2. Common vasodilators: Used for uncontrolled hypertension or excessively high SVR. In cardiogenic shock, lowering the afterload by decreasing SVR will increase CO and get the patient out of shock. a. Nitroprusside: An arterial vasodilator; can result in reflex tachycardia; cyanide is a metabolite. b. Nitroglycerin: Primarily, a venodilator and a coronary artery dilator that decreases venous preload to decrease diastolic wall tension and to allow better heart contraction if it has been overstretched. (1) Allows better diastolic blood flow to the heart itself and may increase CO. (2) Primarily used in cases of coronary ischemia. c. Labetalol: Acts a mixed alpha- and beta-blocker in IV form. d. Esmolol: Pure beta-blocker. e. Nicardipine: Potent calcium channel blocker.

Quick Cuts • If in doubt about oxygenation or increased work of breathing, intubate!

SHOCK Definition

Shock is the clinical syndrome resulting from inadequate tissue perfusion to maintain normal cellular metabolism. Essentially, it is inadequate oxygen delivery to meet oxygen demand. I. Oxygen delivery equation: DO 2 = [1.39 × Hgb (grams) × Sao 2 + (0.003 × Pao 2 )] × CO. A. Pao 2 contributes very little to oxygen delivery. B. Hgb × Sao 2 represents the blood’s oxygen-carrying capacity. C. CO is determined by HR × SV, and SV is determined by cardiac preload, contractility, and afterload.