After restoring blood pressure, therapy is directed at maintaining perfusing pressures and optimizing tissue O 2 availability. This requires a number of steps, including determining which component of the O2 delivery equation should be improved to pay off any O2 debt and match delivery with ongoing needs, and initiating a management (diagnostic and treatment) plan which adequately manages the primary cause of the hypotension.
Immediately post-shock, most patients have an elevated O2 requirement because of the need to repay the O2 debt that developed previously. Subsequently, traumatic and septic shock patients usually demonstrate ongoing elevations in tissue O 2 requirement since the metabolic rate is elevated by the healing processes in trauma and the generalized inflammation typical of sepsis. These patients may then need a systemic O 2 delivery above the normal range (> 600 ml/min/m2). Increasing O2 delivery is accomplished by keeping PaO2 above 70 mmHg (9.3 kPa), transfusing packed red cells to correct anemia, and increasing cardiac output with fluid therapy, inotropes, and/or dilators. A right heart catheter may now be necessary to guide management. Left ventricular filling is optimized by additional fluids. If the pulmonary artery wedge pressure is above 15 to 18 mmHg, O2 delivery is increased using vasodilators and inotropes. An increase in SvO2 and a decrease in arterial lactate can be used to determine the efficacy of therapy.
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