Critical care clinics
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Critical care clinics · Jul 1996
ReviewNutrition support is not beneficial and can be harmful in critically ill patients.
The introductory remark by Lucretius serves as a reminder that nutrient intake can have very different consequences in different subjects. In the patient with an acute or serious illness, metabolic derangements can transform a substance that is normally a source of energy into a source of metabolic toxins. The potential for organic nutrients to become organic toxins in the diseased host is a phenomenon that deserves more attention in the debate about the value of nutrition support in critically ill patients.
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Gastrointestinal tonometry is supposed to diagnose gut mucosal hypoxia using gastric luminal PCO2 and arterial bicarbonatemia, which are substituted in a modified Henderson-Hasselbach equation. This article reviews some of the problems inherent to the multiple assumptions underlying this technique. Tonometry is influenced by several local factors and by systemic acid-base imbalances that are unrelated to oxygenation. Tonometry is a rather crude and cumbersome method of gut capnometry, a technology that may provide valuable information regarding visceral perfusion, but not necessarily oxygenation.
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Increasing DO2 to supranormal levels, spontaneously or therapeutically, correlates with better survival in the critically ill patient, but not all patients who attain a DO2I greater than 600 mL/min/m2 survive. Conversely, there is often a 50% or greater survival rate in patients who do not reach normal DO2I values. No investigator has been able to show an incremental increase in survival with increasing DO2I; but studies have shown improved survival rates with increasing SVO2. ⋯ SVO2 should be normalized when low, again by increasing DO2. Data continue to support clinical interventions aimed at optimizing DO2. Does increasing DO2 increase the survival rates of critically ill patients? Sometimes.
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Critical care clinics · Jul 1996
ReviewHypertensive, hypervolemic, hemodilutional therapy for aneurysmal subarachnoid hemorrhage. Is it efficacious? Yes.
Vasospasm is an important contributor to death and disability after aneurysmal SAH. CBF is decreased after SAH and correlates inversely with the severity of the clinical grade. ⋯ This is attributable, perhaps, to the fact that such trials are difficult to blind. Nevertheless, there is strong evidence that HHH therapy can reverse the delayed onset of profound neurologic deficits by restoring blood flow to ischemic regions, and its prophylactic use can reduce the incidence and severity of DID.
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Critical care clinics · Jul 1996
ReviewICU scoring systems do not allow prediction of patient outcomes or comparison of ICU performance.
Recent revisions of the major ICU scoring systems have broadened their database markedly and increased their statistical accuracy. For a specific patient, however, the systems cannot be accurate enough to direct management decisions. Significant questions remain about the reliability of these systems for comparing different ICUs and different patient populations, especially in surgical and trauma patients. Current scoring systems, therefore, cannot be used reliably in either the management of the individual patient or in the making of quality comparisons between ICUs.