**9. Resuscitation goals**

When approaching a patient in shock, management requires attaining physiological normalcy and hemodynamic stability. In the clinical setting, the progress of treatment is measured by achieving certain goals. These clinical goals help ascertain improvement in global perfusion and oxygenation. Factors measured are included in **Table 5** and are used clinically to determine a patient's response to the management of shock. While these conditions are useful in measuring response, the use of only one or two as an indicator for improvement will lead to shortcomings and mislead a physician regarding the actual response to management.

One goal used to assess treatment is normalcy in heart rate and perfusion pressure representing adequate perfusion and venous return/cardiac output. Perfusion pressure is determined by subtracting the central venous pressure (CVP) by the mean arterial pressure (MAP); MAP-CVP. These parameters can be used to measure hemodynamic stability and are also used to assess response to fluid therapy. With administration of a fluid bolus, heart rate should ideally decrease and MAP-CVP should increase. Another measurement that can be used to assess response to fluid therapy and inotrope therapy response is the shock index (HR/SBP). Calculated by dividing


**Table 5.** *Resuscitative goals and normal values.*

heart rate (HR) by systolic blood pressure (SPB), the shock index should ideally decrease as fluid therapy is directed at improving stroke volume, thereby decreasing HR, and inotrope therapy improves vascular tone and SBP.

As mentioned earlier, during shock states compensatory mechanisms redirect blood to vital organs such as the brain, heart and kidneys. Consequently, as shock progresses from compensated to uncompensated phase, these organs will begin to show signs of dysfunction. Mental status of a patient is therefore a parameter which should be assessed to determine improvement in a patient's condition. While improvement is a good sign, not all patients will have altered mental status and, when present, is often a late manifestation of shock. Relying on altered mental status as an indicator of shock and its improvement as good response to therapy is not a reliable approach and should be taken with caution and in combination with other factors. The kidney is another organ which can be used to assess response to therapy. A normal urine output of >1 mL/kg/h represents adequate renal perfusion and perfusion pressure. However, urine output only represents the improvement in renal perfusion and does not provide a picture of global perfusion status.

Systemic vascular tone and cardiac output can both be determined by assessing peripheral temperatures, capillary refill and distal pulse qualities. Normal capillary refill is <2 seconds and coupled with normal peripheral temperature and distal pulses correlates with adequate perfusion to the peripheries. However, these parameters do not provide indication of oxygenation. Cases such as anemia or hemodilution may have normal peripheral temperature, pulses and capillary refill but oxygen delivery is still impaired.

As shock is defined as impaired systemic oxygen delivery, lactate levels are a good indicator of global oxygenation. Lactate trends should be observed rather than single serum lactate measurements as a single measurement does not indicate the progression of disease. Increases of lactate levels of ≥70 mmol/L/h. is associated with worsening oxygen delivery and outcomes.

Superior vena cava oxygen saturation (SVCO2) of ≥70% is a good therapeutic endpoint in the management of shock. As mentioned earlier in the chapter, when there is good oxygen delivery, SVCO2 should be maintained above 70% representing no increase in oxygen extraction during the compensatory phase of shock. Measuring SVCO2 can be done via central venous catheters with venous oximetry or, more recently, with the use of near-infrared spectroscopy, a less invasive method. One can also calculate the difference in arterial and venous oxygen content (AVDO2) to assess the degree of oxygen extraction during this phase of shock. Normal values show a difference of ≤5 mL O2/100 mL of blood and increases in AVDO2 indicate increases in oxygen extraction.
