In order to guide therapy in shock, targets must be set. Classical goals have included adequate blood pressure (above 120/80 mmHg), a heart rate within certain limits (60-120 beats/min), a urine output above 0.5 ml/kg/h, a central venous pressure of 4 to 12 cmH 2O, and a cardiac index (cardiac output indexed to body surface area) of 2.8 to 3.5 ml/min/m2 (ShoemaMreLal 1988). Shoemaker and colleagues reviewed a cohort of high-risk surgical patients and found that survival is improved if the following supranormal values can be obtained: cardiac index above 4.5 ml/min/m 2, oxygen delivery above 600 ml/min/m2, and oxygen consumption above 170
ml/min/m2. (NB Both oxygen delivery and consumption are indexed to body surface area (Tuchs.chmidlet..a./ 1992; B°Yde..i.a.l 1993)) Fluids, blood, and inotropes were used to achieve these goals, and if a patient was unable to achieve them with therapy the prognosis was poor.
Other research has not supported these results. Gattinoni et.al (1995). compared three groups: supranormal cardiac index (above 4.5 ml/min/m2), normal cardiac index (2.5-3.5 ml/min/m2), and normal mixed venous saturation (Svo2 > 70 per cent). Fluids, blood, and inotropes were used to attain these goals in a heterogeneous group of critically ill shocked patients. It was found that supranormal cardiac index or Svo2 > 70 per cent conferred no benefit to morbidity or mortality in the shocked patient.
Thus, although higher than normal oxygen delivery provides the opportunity for improved oxygen consumption, it cannot ensure that tissue hypoxia will be reversed. Chapter References
Boyd, O., Grounds, R.M., and Bennett, E.D. (1993). A randomized clinical trial of the effect of deliberate perioperative increase of oxygen delivery on mortality in high-risk surgical patients. Journal of the American Medical Association, 270, 2699-707.
Gattinoni, L., et al. (1995). A trial of goal-oriented hemodynamic therapy in critically ill patients. New England Journal of Medicine, 333, 1025-32.
Lee, S., Chang, R.W.S., and Jacobs, S. (1990). Intermittent nasogastric feeding: a simple and effective method to reduce pneumonia among ventilated ICU patients. Clinical Intensive Care, 1, 100-2. Selective Decontamination of the Digestive Tract Trialists' Collaborative Group (1993). Meta-analysis of randomised controlled trials of selective decontamination of the digestive tract. British Medical
Journal, 307, 525-32.
Shoemaker, W.C., Appel, P.L., Kram, H.B., Waxman, K., and Lee T.-S. (1988). Prospective trial of supranormal values of survivors as therapeutic goals in high-risk surgical patients. Chest, 94, 1176-86.
Tuchschmidt, J., Fried, J., Astiz, M., and Rackow, E. (1992). Elevation of cardiac output and oxygen delivery improves outcome in septic shock. Chest, 102, 216-20.
Mechanis,"™ cell .injury
Ischemia and ..oxidants
Cell.. death and ..tissue. repair
The... evidence .foLcellulaLd.yssx.ia... in ..multiple,.. organ. .Mlu,,re,:..,c,a.u,s,e ..o„r.. effect?
Systemic. .oxygen. .flux
The.. splanchnic .circulation
Translocationand.. .multiple.organ.. failure
Linking.gut ..mucosal ..ischemia... to..m.uitiple.. organ ..failure
Interpretingmeasures of..splan,chnic .blood. ..flow Leukocyte..activatiiion..inn the splanchnic ..bed Multiple..physiological insults
Mechanismsof .remote..organ. injury
Leukocyte-mediated ..injury Mechanismsjor specific ..organinvolveEent ImmunoincomBetence
Conclusions Chapter.. .References
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