Colloid Oncotic Pressure Research Articles

International Trauma Anesthesia and Critical Care Society (ITACCS)

International Trauma Anesthesia and Critical Care Society (ITACCS)

Diffusion-weighted magnetic resonance imaging confirms marked neuroprotective efficacy of albumin therapy in focal cerebral ischemia.

We have recently shown high-dose human serum albumin therapy to confer marked histological protection in experimental middle cerebral artery occlusion (MCAo). We have now used diffusion-weighted magnetic resonance imaging (DWI) in conjunction with morphological methods to expand our understanding of this therapeutic approach. Physiologically controlled Sprague-Dawley rats received 2-hour MCAo by the modified intraluminal suture method. Treated rats received 25% human serum albumin solution (1% by body weight) immediately after the MCA was reopened. Vehicle-treated rats received saline. Computer-based image averaging was used to analyze DWI data obtained 24 hours after MCAo and light-microscopic histopathology obtained at 3 days. In a matched series, plasma osmolality and colloid oncotic pressure, as well as brain water content, were determined. Albumin therapy, which lowered the hematocrit on average by 37% and raised plasma colloid oncotic pressure by 56%, improved the neurological score throughout the 3-day survival period. Within the ischemic focus, the apparent diffusion coefficient (ADC) computed from DWI data declined by 40% in vehicle-treated rats but was preserved at near-normal levels (8% decline) in albumin-treated rats (P<0.001). Albumin also led to higher ADC values within unlesioned brain regions. Histology revealed large consistent cortical and subcortical infarcts in vehicle-treated rats, while albumin therapy reduced infarct volume at these sites, on average, by 84% and 33%, respectively. Total infarct volume was reduced by 66% and brain swelling was virtually eliminated by albumin treatment. Microscopically, while infarcted regions of vehicle-treated rats had the typical changes of pannecrosis, infarcted zones of albumin-treated brains showed persistence of vascular endothelium and prominent microglial activation, suggesting that albumin therapy may help to preserve the neuropil within zones of residual infarction. These findings confirm the striking neuroprotective efficacy of albumin therapy in focal cerebral ischemia and reveal that this effect is associated with DWI normalization and a mitigation of pannecrotic changes within zones of residual injury.

The need for reappraisal of the albumin molecule

Albumin is the protein in the blood with the largest concentration. It is easy to measure, purify, and give to patients. Until recently, there has been little research on its role in the critically ill. Serum concentrations decrease rapidly with illness. Although it has several functions in healthy humans (maintenance of colloid oncotic pressure, drug transport, and free radical scavenging), how these functions change with illness is unknown. Indeed, how albumin itself changes is also unknown. To add to these difficulties in understanding the role of albumin there are relatively normal humans and also rats that lack the genes to make albumin in significant amounts. As well as the expected effects of albumin there are important other effects on blood clotting and the effects of diuretics that need to be evaluated.

Increased VLDL in nephrotic patients results from a decreased catabolism while increased LDL results from increased synthesis

Increased VLDL in nephrotic patients results from a decreased catabolism while increased LDL results from increased synthesis

Application of Polygeline in Pediatric Cardiac Surgery

The purpose of this study was to determine the effect of using polygeline as part of the cardiopulmonary bypass solution in pediatric cardiac surgery. A total of 40 cases were divided into two groups, a polygeline group (H group, n=20) and a plasma group (P group, n=20). Operations were performed under routine extracorporeal circulation. The dose of polygeline or plasma used was calculated to maintain the patient's plasma colloid oncotic pressure at 10-12 mmHg. The results showed that in the polygeline group, no patient developed allergic or coagulation disorders even after large volumes of polygeline were used (45 ml/kg). At the initiation and completion of cardiopulmonary bypass (CPB), the concentrations of calcium were higher in the H group (1.38 ± 0.19, 1.21 ± 0.11) than those (0.72 ± 0.11, 0.95 ± 0.10) in the P group. There were no other statistically significant differences between the two groups. There were no organ problems in the patients included in the study. This study demonstrated that polygeline could be used as part of prime solution instead of plasma to keep an ideal plasma colloid oncotic pressure, reduce infections caused by blood product transfusions and lower the cost to the patients.

Effect of Synthetic Colloids on Refractometric Readings of Total Solids

SummaryVeterinary patients are treated with colloid solutions for plasma volume expansion and maintenance of plasma colloid oncotic pressure (COP). In practice COP is usually extrapolated from measurement of albumin, total protein, or refractometric total solids (TS) as an estimate of total protein. The objective of this study was to determine if refractometer readings accurately reflect levels of synthetic colloid in the blood. Serial dilutions of synthetic colloids Dextran 70 and hetastarch into 2.5% and 5% human serum albumin (HSA) were prepared, and COP and TS measurements were performed. Synthetic colloids were found to produce a significant increase in measured COP, without a significant change in refractometric TS readings. Measured COP correlated well with concentration of synthetic colloid. In clinical patients, treatment of decreased COP with synthetic colloids should be monitored by direct measurement of COP or by observing resolution of clinical signs of hypovolemia or edema. (Vet Emerg &amp; Crit Care, 1998; 8: 21–26)

Volumenersatzmittel -Pharmakologie und klinischer Einsatz

PHYSIOLOGY AND PATHOPHYSIOLOGY: Total body water represents 60% of body weight (BW), consisting of 40% BW intra- and 20% BW extracellular fluid. Extracellular fluid is divided into 16% BW interstitial fluid and 4% BW plasma volume (Fig. 1). The colloid oncotic pressure (COP) of the plasma proteins, which is about 25 mmHg (Fig. 2), is the main factor for the retention of intravascular volume and the prevention of interstitial edema. Within a defined range, oxygen transport capacity can be improved by normovolaemic haemodilution. Under strictly normovolaemic conditions ("controlled haemodilution"), the critical haemoglobin concentration for intensive care patients is about 10.0 g/dl, and 8-6 g/dl in patients with satisfactory compensatory mechanisms under stable clinical conditions. Larger blood volume deficits are replaced step by step with volume replacement solutions (crystalloids and synthetic colloids), packed red cells, fresh-frozen plasma, and platelets (Fig. 3). VOLUME REPLACEMENT WITH CRYSTALLOID AND COLLOID SOLUTIONS: Crystalloid solutions do not contain any macromolecules. Due to their lack of intrinsic COP, they spread rapidly over the intravascular and interstitial space. To achieve a comparable volume effect like colloid solutions, a fourfold infusion volume is necessary. Thus, crystalloids should be used in addition to colloid solutions to compensate the interstitial fluid deficit. Hyperosmotic-hyperoncotic solutions have not yet been established, and their benefit seems doubtful. Synthetic colloid solutions contain gelatin, dextran, or hydroxyethyl starch (HES) molecules. Due to their intrinsic COP, fluid is fixated in the intravascular space (Fig. 4). Solutions with high COP increase the intravascular volume due to resorption of interstitial fluid (plasma expanders). Pharmacological characterisation of synthetic colloids includes concentration [%], mean molecular weight [x1,000 Dalton] and degree and position of substitution (HES only). Main clinical features are the maximal volume effect and the duration of a 100% and a 50% volume effect (Fig. 5). For economic reasons, 5% albumin should not be used for volume replacement. The use of 20% albumin in intensive care patients is also limited and recommended only if a capillary leck is unlikely and the dose limits of synthetic colloids are reached. Gelatin is a polypeptide of bovine origin and achieves a shortlasting isovolaemic volume effect. When compared with dextran or HES, negative effects on haemostatis are less, and the renal function is not impaired. Thus, gelatin is first of all indicated in patients with limited volume demand, and secondly in situations with massive blood losses, when the dose limits of HES are reached. Dextran has no specific benefits. HES is a polysaccharide of maize or potato origin. By substitution of glucose molecules with hydroxyethyl groups, starch molecules are protected against fast amylase degradation. Metabolism depends on the degree and position of substitution and mean molecular weight. Smaller molecules are eliminated via the kidneys, but a certain amount of larger molecules is stored in the reticulo-endothelial system. HES is available in very different preparations (concentration 3-10%, mean molecular weight 70,000-450,000 Dalton, substitution 50-70%). Special indications of 10% HES 200/0.5 are rapid hypervolaemic replacement of massive blood losses and increase of COP in intensive care patients without capillary leak. Synthetic colloids as well as albumin may lead to adverse reactions, which are generally very rare. In large-scala studies, no significant differences have been found with regard to incidence and severity.

Effects of Oncotic Pressure and Hematocrit on Outcome After Hypothermic Circulatory Arrest

Background. A recent study found that a higher-perfusate hematocrit was associated with improved neurologic recovery after deep hypothermic circulatory arrest. The current study examined the relative contributions of oxygen delivery and colloid oncotic pressure to this result, as well as the efficacy of different colloidal agents and modified ultrafiltration. Methods. Twenty-six piglets were randomized into five groups (n = 5 or 6 animals per group): control group 1—blood and crystalloid prime, hematocrit of 20%; group 2—blood and hetastarch prime, hematocrit of 20%; group 3—blood and pentafraction prime, hematocrit of 20%; group 4—blood and crystalloid prime with 10 minutes of modified ultrafiltration; group 5—whole blood prime, hematocrit of 30%. All groups underwent 60 minutes of deep hypothermic circulatory arrest at 15°C. Results. Groups 2 and 3 showed less body weight gain (analysis of variance, p = 0.001; group 2 versus group 1, p = 0.0009; group 3 versus group 1, p = 0.0009) and body water content after cardiopulmonary bypass (analysis of variance, p = 0.001; group 2 versus group 1, p = 0.003; group 3 versus group 1, p = 0.013). Group 5 showed more rapid recovery of phosphocreatine and intracellular acidosis, as measured by magnetic resonance spectroscopy, during rewarming than group 1 did (phosphocreatine, p = 0.0329; intracellular acidosis, p = 0.0462). Group 3 also showed accelerated recovery of intracellular acidosis ( p = 0.0411). Cytochrome a,a3 recovery, determined by near-infrared spectroscopy, was significantly better in group 5 than in group 1 and worse in group 2 than in group 1 after rewarming. The neurologic deficit score and overall performance category score were best in group 5 (neurologic deficit score, p = 0.012; overall performance category score, p = 0.046) on the first postoperative day. Group 3 also had a better overall performance category score than group 1 did ( p = 0.0068). Only group 1 and 2 animals showed histologic damage. Conclusions. Both higher hematocrit and higher colloid oncotic pressure with pentafraction improve cerebral recovery after deep hypothermic circulatory arrest. The higher hematocrit improves cerebral oxygen delivery but does not reduce total body edema. Modified ultrafiltration after cardiopulmonary bypass is less effective than having a higher initial prime hematocrit or colloid oncotic pressure.

Society of Neurosurgical Anesthesia and Critical Care

Society of Neurosurgical Anesthesia and Critical Care

Oncotic, hemodilutional, and hemostatic effects of isotonic saline and hydroxyethyl starch solutions in clinically normal ponies

Abstract Objective To evaluate the oncotic, hemodilutional, and hemostatic effects of IV infusions of a large volume of isotonic saline solution and 2 doses of 6% hydroxyethyl starch (HES) in clinically normal ponies. Animals 12 adult ponies. Procedure Ponies were assigned to 3 treatment groups and received the following IV infusions: 80 ml of 0.9% sodium chloride/kg; 10 ml of 6% HES (in 0.9% sodium chloride)/kg; or 20 ml of 6% HES (in 0.9% sodium chloride)/kg. Blood samples were collected for determination of colloid oncotic pressure (COP), PCV, plasma total protein concentration, platelet count, von Willebrand factor antigen (vWf:Ag) activity, fibrinogen concentration, prothrombin time, activated partial thromboplastin time (APTT), and factor VIII coagulant (FVIII:C) activity. A rocket immunoelectrophoretic procedure was used for determination of vWf:Ag activity. A modification of the APTT assay was used for determination of FVIII:C activity. Cutaneous bleeding time was determined, using a template method. Results Mean COP was persistently increased over baseline values in the face of hemodilution in HES-treated ponies. Prothrombin time, APTT, and fibrinogen concentrations decreased after infusions and vWf:Ag and FVIII:C activities were decreased in dosedependent manner in HES-treated ponies. Though cutaneous bleeding time was not significantly affected in ponies of any group, a trend toward prolongation of bleeding time was evident in ponies receiving 20 ml of HES/kg. This trend appeared to be associated with marked decrement in vWf:Ag activity at this dosage. Conclusions and Clinical Relevance Infusion of HES in clinically normal ponies increases COP, and exerts dose-dependent hemodilutional effects and dose-dependent effects on specific hemostatic variables. Thus, HES may be useful for resuscitative fluid treatment of horses. (Am J Vet Res 1997;58:541–548)

Blood volume regulation

AbstractThe maintenance of adequate cardiac output and tissue perfusion is dependent on intravascular blood volume and its adequate return to the heart. Considering the numerous functions of the cardiovascular system in providing adequate flow to the peripheral microcirculation, it is not surprising that there may be conflicts of interest when stresses are placed on the system. Of particular importance are the stresses in which there are increased oxygen demands, decreased oxygen availability and concomitant requirements for temperature regulation.In the context of depleted intravascular blood volume, the splanchnic circulation provides an autologous blood bank until transcapillary refill of the circulation occurs. On the other hand centralisation of blood from the venous capacitance compartment, as seen with acute hypoxia, leads to overfilling of the heart, release of atrial natriuretic peptide and subsequent reduction of the plasma volume by transcapillary efflux.In this review the basic physiology of blood volume, red cell mass and plasma volume regulation will be presented, followed by a consideration of the pathophysiological changes occurring in the context of a variety of clinical settings. Recent insights into neurohormonal aspects of blood volume regulation, the role of the spleen, the interstitial compartment, colloid oncotic pressure, vasomotion and red cell function will be presented.

Cardiopulmonary bypass with modified fluid gelatin and heparin-coated circuits

We have assessed the efficacy of cardiopulmonary bypass (CPB) using normal colloid oncotic pressure (COP) in a randomized, controlled study of 20 patients undergoing elective coronary artery surgery using heparin-coated circuits. For CPB, we used either crystalloid priming 1650 ml (n = 10) or colloid priming 1650 ml (2.4% modified fluid gelatin, n = 10). While COP did not change during bypass in the colloid group, a decline was observed in the crystalloid group (P = 0.005). By the end of bypass, the decrease in COP compared with baseline (delta COP) was 8.5 (S.D. 1.1) mm Hg in the crystalloid group compared with 1.5 (2.1) mm Hg in the colloid group (P = 0.0001). delta COP correlated positively with fluid balance during bypass (r2 = 0.41, P = 0.002). Similar increments in complement factors C3b/c and C4b/c, tumour necrosis factor-alpha and neutrophil elastase, but not endotoxins, were found in both groups as indicators of a systemic inflammatory response. A clinical performance score composed of fluid balance, postoperative duration of intubation and the difference between rectal temperature and skin temperature was more favourable in patients treated with colloid priming (P = 0.03). Median postoperative hospital stay was 7 (range 5-16) days in the crystalloid group compared with 5 (4-8) days in the colloid group (P = 0.016). Regression analysis indicated that CPB time, fluid balance during operation and postoperative PO2/FlO2 ratio were independent factors that predicted postoperative hospital stay. From these preliminary results we conclude that in the absence of endotoxaemia, use of a normal COP during CPB with modified fluid gelatin in heparin-coated circuits resulted in an improved postoperative course an a reduction in hospital stay.

Clinical practice interpretation of oncotic pressure, serum albumin and protein determination and their ability for guiding therapeutics in cases of disturbances of capillary exchanges

The osmotic pressure of the serum proteins, the colloid osmotic pressure (COP) or oncotic pressure, is one of the four Starling forces determining fluid movements across a capillary. Theoretical and empirical formulas considering plasma protein or albumin concentration have been used. However, such calculations are only approximations, being inadequate especially when protein fractionation pattern is abnormal or when artificial colloids are used. It is preferable to measure COP directly. In healthy standing adults COP is around 25 mmHg. It is influenced by age, position, blood pressure and pH. The interpretation of the COP must take into account, on the one hand the possible variations of the other factors involved in the Starling's equilibrium and, on the other hand the structural and functional differences between systemic and pulmonary circulations. When capillary permeability is not altered, a decreased COP is associated with an increased filtration rate across the capillaries, resulting in oedema in skeletal muscle, skin, subcutaneous tissue, intestine and heart. The lung is relatively insensitive to extravascular fluid shifts caused by lowering of the COP, due to the efficacy of the pulmonary lymph drainage and the high pulmonary interstitial protein concentration. The main determinant of fluid exchange in the lung is then the hydrostatic force, reflected by the pulmonary artery wedge pressure. When capillary permeability is altered, the decreased reflectance coefficient results in a smaller effect of the COP on interstitial oedema formation. Several studies demonstrated that oedema formation in the injured tissues seems unaffected by changes in COP. During fluid resuscitation, COP measurement is useful for assessing the risks of peripheral oedema formation and additional measurements of pulmonary artery wedge pressure for assessing the risks of pulmonary oedema. Therefore COP measurement can serve as a useful guide for selection of colloids or crystalloids in critically ill patients, avoiding expensive albumin administrations.

Long-term high-colloid oncotic therapy for ischemic brain edema in gerbils.

We evaluated the effects of long-term administration of high-colloid oncotic pressure on ischemic brain edema in Mongolian gerbils. Animals that exhibited stroke after 35 minutes of unilateral forebrain ischemia were used. The gerbils were divided into albumin- (1 g/kg body wt, 25% albumin; n = 30) and saline-injected (4 mL/kg; n = 30) groups. Both agents were administered intravenously every 12 hours starting immediately after the recirculation. Plasma colloid oncotic pressure, serum sodium and potassium concentrations, and brain water, sodium, and potassium content were measured 24, 48, and 72 hours after recirculation. Plasma colloid oncotic pressure at 24, 48, and 72 hours after recirculation was significantly higher in the albumin- (26.1 +/- 2.3 mm Hg) than in the saline-treated group (18.5 +/- 1.9 mm Hg; P < .01), and brain water content of the ischemic hemisphere was significantly lower in the albumin group (79.5%, 80.2%, and 80.5%, respectively) than in the saline group (80.9%, 81.6%, and 82.1%, respectively; P < .05) at all three time points. Brain sodium content at 24 hours was significantly lower in the albumin than in the saline group (P < .05), while brain potassium content at 24 and 48 hours was significantly higher in the albumin than in the saline group (P < .05). The changes in brain water and sodium plus potassium content, which were calculated from differences between the ischemic and nonischemic hemispheres, showed a significant correlation in both groups (P < .01), but there was no significant difference between the linear regression lines for both groups. Long-term high-colloid oncotic pressure was effective in treating ischemic brain edema, probably acting by diminishing the bulk flow through the disrupted blood-brain barrier and ameliorating the vasogenic edema.

Reduction in prime volume attenuates the hyperdynamic response after cardiopulmonary bypass

A hyperdynamic response to cardiopulmonary bypass is characteristically observed in the post-operative course. To determine the effect of prime volume on the hemodynamic response, a database study was performed on patients who underwent elective coronary artery bypass grafting with an extracorporeal circuit with either a large prime volume (2,350-mL prime, n = 20) or a small prime volume (1,400-mL prime, n = 20). Measurements were carried out at fixed time points before and after cardiopulmonary bypass (until 18 hours postoperatively) and include hematocrit, colloid oncotic pressure, fluid balance, and hemodynamic profile (mean of three measurements). The lower colloid oncotic pressure in the large prime group (16.2 +/- 0.6 mm Hg versus 19.1 +/- 1.1 mm Hg, p = 0.0002) was associated with a highly positive fluid balance (5.5 +/- 0.9 L versus 2.8 +/- 0.7 L, p = 0.0001). With the on-bypass hematocrit aimed at 22% to 23%, autologous blood was predonated by 16 patients in the small prime group but by none in the large prime group. Reinfusion of autologous blood resulted in a reduction in blood bank requirements (p = 0.03). Mean arterial pressure was 83 +/- 4 mm Hg for small prime versus 76 +/- 4 mm Hg for large prime (p = 0.01). Cardiac index was 2.9 +/- 0.2 L.min-1.m-2 for small prime versus 3.8 +/- 0.3 L.min-1.m-2 for large prime (p = 0.0001). Pulmonary vascular resistance index was 281 +/- 40 dyne.s.cm5.m-2 for small prime versus 188 +/- 22 dyne.s.cm5.m-2 for large prime (p = 0.0009). Oxygen delivery was 42 +/- 5 mL.min-1.m-2 for small prime versus 51 +/- 3 mL.min-1.m-2 for large prime (p = 0.004). Vasoactive medication was not different among groups. Reduction in prime volume attenuates the hyperdynamic response after cardiopulmonary bypass. Furthermore, an important reduction in blood bank products can be obtained with small prime volumes.

Albumina. Da fisiopatologia ao uso terapêutico.

Albumin has multiple roles in homeostasis. The importance of serum albumin in colloid oncotic pressure has been overemphasized. Albumin supplementation must be supported by pathophysiology and the achievement of specific objectives.

Colloid infusion after brain injury: effect on intracranial pressure, cerebral blood flow, and oxygen delivery.

We sought to determine the effects of colloid osmotic pressure on cerebral edema formation after brain injury. We hypothesized that an increase in plasma oncotic pressure accompanying a colloid infusion would be associated with a decrease in intracranial pressure and increases in cerebral blood flow and oxygen delivery when compared with isotonic crystalloid. Prospective, laboratory study. University surgical research laboratory. Adult swine, both genders. Cryogenic brain injury with intravenous fluid infusion of either lactated Ringer's solution or 6% dextran-70 in normal saline. The effect of this intervention was monitored for 24 hrs. Mean arterial pressure, central venous pressure, intracranial pressure, hemoglobin concentration, plasma oncotic pressure, serum osmolality, cerebral blood flow, and specific gravity of cortical biopsies. Cryogenic injury significantly increased the cortical water content and the intracranial pressure and significantly decreased the cerebral blood flow and oxygen delivery (p < .05). Dextran infusion significantly increased the colloid oncotic pressure. There were no differences between the lactated Ringer's solution and dextran groups in intracranial pressure, cerebral oxygen delivery, or cortical water content after 24 hrs. Colloid infusion after a focal cryogenic injury does not increase cerebral oxygen delivery or reduce either cerebral edema formation or intracranial pressure when compared with lactated Ringer's solution. Colloid is not superior to isotonic crystalloid in the management of isolated brain injury.

Hematological alterations after acute exposure to hyperbaric oxygen in rats.

1. Acute exposure to hyperbaric oxygen (HBO) is associated with a significant increase in haematocrit which returns to the control level after 24h of recovery in room air. In this study we report changes in blood viscosity in Sprague-Dawley rats after acute exposure to HBO. 2. The rats were divided into three groups: a control group included rats not exposed to HBO (CON), a group studied immediately after acute exposure to HBO at 283.7 kPa for 6h (HBO), and a group allowed to recover for 24h in room air after HBO exposure (REC). 3. The viscosity of the whole blood, plasma and red blood cells (RBC) suspension was measured in the three groups. A significant increase in whole blood viscosity was detected in HBO and REC groups compared with CON (P < 0.05), but no changes in the viscosity of the plasma or RBC suspension were noted. 4. A significant decrease in oxygen delivery index was found in the REC group compared with the CON and HBO groups (P < 0.05). 5. In a subgroup of rats, several blood parameters known to influence blood viscosity were evaluated. A significant increase in plasma colloid oncotic pressure was noted in HBO rats compared with CON (P < 0.01). A marked increase in platelet count and fibrinogen concentration was detected in HBO and REC rats compared with CON (P < 0.05). Furthermore, a significant increase in total leukocytic count was noticed in REC group compared with CON and HBO (P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of the pressure-flow characteristics of isolated perfused rat kidneys with inhibited tubular reabsorption.

The renal hemodynamics were studied in an isolated perfused rat kidney model modified for investigations of the glomerular permeability characteristics. The tubular reabsorptive activity was inhibited by perfusion at low temperature (8 degrees C) in the presence of furosemide and nitroprusside resulting in a dramatic increase in the filtered load of fluid and solute reaching the tubules and hence in tubular pressure. The glomerular filtration rate (GFR), arterial pressure (PA) and needle pressure (intrarenal tissue pressure, PiR) were continuously recorded and the glomerular hydrostatic pressure was estimated by an arterial occlusion technique. The pre- to postglomerular resistance ratio was calculated from the pressure vs. GFR relationships for two perfusates having differing oncotic pressures (pi = 5.5 and pi = 20 mmHg), from which estimations of glomerular hydrostatic pressures (PGC) were concomitantly made. Thus, increases in delta pi could be exactly counterbalanced by equally large increases in PGC for any given GFR, the needle and Bowman's capsule pressures being dependent on GFR but not on plasma colloid oncotic pressure. The experimental interventions resulted in a pronounced elevation of PiR as compared with in vivo conditions, while the PGC values were in a normal range, resulting in reduced glomerular filtration pressures. Furthermore, the clearance of albumin varied with the oncotic pressure in agreement with the notion of heteroporosity.

Colloid Oncotic Pressure and the Clinical Use of Colloidal Solutions

SummaryThe synthetic colloids, dextran and hydroxyethyl starch, have only recently enjoyed widespread use in critically ill veterinary patients. Plasma proteins normally provide colloid oncotic pressure and, thereby, are the primary force responsible for retaining fluid within the vasculature. Abnormally low plasma protein concentrations, common in the critically ill patient, are associated with excessive fluid loss from capillaries and development of peripheral or pulmonary edema. Infusion of colloid solutions decreases the potential for and severity of edema in hypooncotic states. Dextran and hydroxyethyl starch solutions also provide other positive hemodynamic benefits and are a preferable alternative to crystalloid usage in the resuscitation of selected patients from hypotensive and hypovolemic states. Potential side effects of synthetic colloid infusion include anaphylactoid reactions, increased risk of bleeding, interference with cross matching, and acute renal failure. Knowledge of the mechanisms responsible for these adverse effects minimizes their occurrence.