The serum albumin level is the best index of nutritional status as it relates to outcome.Patients whose serum albumin level is below 3,5 g/dl have consistently higher morbidity rates( increased rate of infection, length of hospital stay, time on a ventilator, time in the ICU, cost, and most significantly, mortality).
As the albumin drops from 3,5 to 3,0 g/dl, there is a 15% increase in morbidity and mortality.For patients whose serum albumin concentration is less than 2,0 g/dl, morbidity and/or mortality approach 100%.
Malnutrition can be manifested as either kwashiorkor or marasmus.
In fact, hypoproteinemic patients may appear otherwise wellnourished.They are suffering from the hypoalbuminemic type of malnutrition known as the adult kwashiorkor-like syndrome.
These conditions can occur in the clinical setting.For example, overfeeding a patient nonprotein calories can produce obesity while suppressing visceral proteins.
Another clinical variables that suppresses visceral protein synthesis is inflammation.Tumor necrosis factor (TNF), interleukin (IL-1), interleukin 6 (IL-6) are inflammatory mediators that directly depress albumin synthesis.Albumin depression is detrimental for host survival since albumin is important in a number of processes, such as maintenance of oncotic pressure, drug transport, and tolerance of enteral feedings.IL-1 and IL-6 decrease the synthesis of mRNA for albumin.Thus, albumin depression probably occurs because of increased vascular permeability and decreased synthesis.
Albumin is the major component of total protein.
Total protein produces colloid osmotic pressure.When nutritional status deteriorates to a point that circulating proteins can no longer sustain a colloid pressure capable of holding fluid in the circulation, hypo-oncotic edema will develop and can be clinically significant.Corporal edema is associated with the development of pressure ulcers.
Hypoproteinemia is associated with intestinal edema, that negatively affects the luminal absorption and results in diarrhea.
Finally, if profound hypoproteinemia is pillared with an elevated wedge pressure, interstitial fluid flow can overwhelm lymphatic clearance and result in pulmonary edema.This condition can be misinterpreted as adult respiratory distress syndrome (ARDS).
Physiology of Edema
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With an understanding of the principles governing fluid/space dynamics, there should be no controversy regarding the use of colloid or crystalloid during resuscitation or nutritional support.
The principles are that a particle in solution that cannot cross a semipermeable membrane will draw water to itself, thus creating a gradient.
The magnitude of this gradient is effected by the number of particles in solution, not the size of the particles.
Therefore, since protein molecules in the circulation do not easily cross the semipermeable membrane of the cell, each of those molecules contributes equally to the oncotic gradient across the end-capillary membrane.
Albumin, globulin and fibrinogen compose total protein.
Albumin makes up approximately 60% of circulating proteins.
There are overlapping factors (based on Starling’s equation® Jv= Kf[(Pc-Pif)-s(pc-pif)]-Qlymph) that can result in clinically significant edema.They include elevated hydrostatic pressure, low COP, and altered membrane pore size and lymphatic flow.
If profound hypoproteinemia is allowed to develop and colloid pressure falls below hydrostatic pressure, infused fluid will no longer be effectively hold in the circulation.
Albumin should never be administered to simply raise serum albumin levels.It should be clear that albumin is added to raise the total protein concentration.The goal of adding colloid is to restore adequate colloid pressures and prevent or recover clinically significant interstitial edema.The data based found today in the literature don’t give any conclusion about the use of crystalloid vs. colloid in the critical care patient (in intravascular expansion, hemodynamic stabilization, pulmonary insufficiency, in patients undergoing open heart surgery, with thermal injury or with cirrhosis); concluding only that the use of albumin is indicated in patients with low PCWP (pulmonary capillary wedge pressure) and the importance in correlated the COP (colloid osmotic pressure)/PCWP gradient and the correct use of crystalloid vs. colloid.
Kaminsky V.M., Blumeyer J.T. and Jr; in Albumin Supplementation:Starling’s Law as a Guide to Therapy and Literature Review, pages 143-157 Nutritional in Critical Care
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