Increase In Colloid Osmotic Pressure Research Articles

Perioperative trends in plasma colloid osmotic pressure in horses undergoing surgery.

To compare perioperative trends in plasma colloid osmotic pressure (COP) between horses undergoing orthopedic and colic surgery. Prospective clinical study September 2009-January 2011. Veterinary university teaching hospital. Thirty-three healthy, client-owned horses presenting for orthopedic surgery (non-GI) and 85 client-owned horses presenting for emergency exploratory celiotomy (GI, gastrointestinal). None. Data relating to the horse's parameters on presentation, surgical lesion, post-operative management and survival were extracted from computerized clinical records. Heparinized blood samples were taken on presentation (PreOp, pre-operative), on recovery from anesthesia (T0), at 12 (T12) and 24 (T24) hours post recovery. COP was measured within 4 hours of collection. There was no significant difference in PreOp or T0 COP between groups. Both groups had a significant decrease in COP during anesthesia. When compared to their respective pre-operative values, horses in the non-GI group had significantly increased COP at T12, whereas those in the GI group had significantly reduced COP. This trend was continued at T24. Horses in the GI group placed on intravenous crystalloid isotonic fluids post-operatively had a significantly lower COP at T12 and T24. Horses in the GI group that did not survive had significantly lower post-operative COP values at T24. Horses undergoing exploratory celiotomy had significantly lower COP post-operatively than those horses undergoing orthopedic surgery. This difference was more marked in those horses receiving isotonic crystalloid intravenous fluid therapy post-operatively and in those that did not survive to discharge. In the non-GI group an increase in COP post-operatively was common.

The use of canine‐specific albumin in dogs with septic peritonitis

To assess changes in serum albumin concentration (ALB), colloid osmotic pressure (COP), and Doppler blood pressure (DBP) following transfusion of 5% lyophilized canine-specific albumin (CSA) in hypoalbuminemic dogs following surgical source control for septic peritonitis. Prospective randomized clinical trial November 2009 - November 2010. University teaching hospital. Fourteen client-owned dogs with hypoalbuminemia (<27 g/L [2.7 g/dL]) following surgical source control for septic peritonitis. Dogs were randomized to clinician-directed therapy (CDT) and CSA groups. Dogs enrolled in the CSA group received 800 mg/kg of CSA within 24 hours following surgical intervention. At enrollment, ALB, COP, and DBP were not different between groups. ALB, COP, and DBP were significantly increased in the CSA group 2 hours following completion of the transfusion compared with the CDT group (P = 0.0234, 0.0078, 0.0156, respectively). In comparison to the CDT group, there was a significant change in ALB in the CSA group 24 hours after transfusion (P = 0.0039), but no difference in COP (P = 0.3914) or DBP (P = 0.5145). ALB was significantly higher in the CSA group at 24 hours compared with the CDT group (P = 0.0367) At the time of death or discharge, there was no difference between groups regarding ALB, COP, or DBP, but an association between ALB and survival was identified (P = 0.0273). One dog experienced tachypnea during transfusion of CSA; this dog died of unknown respiratory causes 120 hours after transfusion. The administration of CSA in dogs with septic peritonitis results in an increase in ALB, COP, and DBP 2 hours after administration. An increase in ALB persisted at 24 hours compared with a CDT group. Administration of this product was not associated with owner-reported delayed adverse events in this population of dogs.

Effect of intravenous administration of lactated Ringer's solution or hetastarch for the treatment of isoflurane-induced hypotension in dogs

To determine the effect of IV administration of crystalloid (lactated Ringer's solution [LRS]) or colloid (hetastarch) fluid on isoflurane-induced hypotension in dogs. 6 healthy Beagles. On 3 occasions, each dog was anesthetized with propofol and isoflurane and instrumented with a thermodilution catheter (pulmonary artery). Following baseline assessments of hemodynamic variables, end-tidal isoflurane concentration was increased to achieve systolic arterial blood pressure (SABP) of 80 mm Hg. At that time (0 minutes), 1 of 3 IV treatments (no fluid, LRS [80 mL/kg/h], or hetastarch [80 mL/kg/h]) was initiated. Fluid administration continued until SABP was within 10% of baseline or to a maximum volume of 80 mL/kg (LRS) or 40 mL/kg (hetastarch). Hemodynamic variables were measured at intervals (0 through 120 minutes and additionally at 150 and 180 minutes in LRS- or hetastarch-treated dogs). Several clinicopathologic variables including total protein concentration, PCV, colloid osmotic pressure, and viscosity of blood were assessed at baseline and intervals thereafter (0 through 120 minutes). Administration of 80 mL of LRS/kg did not increase SABP in any dog, whereas administration of <or= 40 mL of hetastarch/kg increased SABP in 4 of 6 dogs. Fluid administration increased cardiac index and decreased systemic vascular resistance. Compared with hetastarch treatment, administration of LRS decreased blood viscosity. Treatment with LRS decreased PCV and total protein concentration, whereas treatment with hetastarch increased colloid osmotic pressure. Results indicated that IV administration of hetastarch rather than LRS is recommended for the treatment of isoflurane-induced hypotension in dogs.

Tissue hyperosmolality and brain edema in cerebral contusion

Severe cerebral contusion is often associated with nonhemorrhagic mass effect that progresses rapidly within 12 to 48 hours posttrauma. The mechanisms underlying such a rapid progression of mass effect cannot be fully explained by classic concepts of vasogenic and cytotoxic brain edema. Data from previous clinical trials, including diffusion-weighted magnetic resonance imaging studies, have indicated that cells in the central (core) area of the contusion undergo shrinkage, disintegration, and homogenization, whereas cellular swelling is located predominately in the peripheral (rim) area during this period. The authors hypothesized that high osmolality within the contused brain tissue generates an osmotic potential across the central and peripheral areas or causes blood to accumulate a large amount of water. To elucidate the role of tissue osmolality in contusion edema, they investigated changes in tissue osmolality, specific gravity, and ion concentration in contused brain in both experimental and clinical settings. Their results demonstrated that cerebral contusion induced a rapid increase in tissue osmolality from a baseline level of 311.4 +/- 11.3 to 402.8 +/- 15.1 mOsm at 12 hours posttrauma (p < 0.0001). Specific gravity in tissue significantly decreased from 1.0425 +/- 0.0026 to 1.0308 +/- 0.0028 (p < 0.01), reflecting water accumulation in contused tissue. The total ionic concentration [Na+] + [K+] + [Cl-] did not change significantly at any time point. Inorganic ions do not primarily contribute to this elevation in osmolality, suggesting that the increase in colloid osmotic pressure through the metabolic production of osmoles or the release of idiogenic osmoles can be a main cause of contusion edema.

RAPID RESTORATION OF MICROCIRCULATORY BLOOD FLOW WITH HYPERVISCOUS AND HYPERONCOTIC SOLUTIONS LOWERS THE TRANSFUSION TRIGGER IN RESUSCITATION FROM HEMORRHAGIC SHOCK

Resuscitation from hemorrhagic shock relies on fluid retransfusion. However, the optimal properties of the fluid have not been established. The aim of the present study was to test the influence of the concentration of hydroxyethyl starch (HES) solution on plasma viscosity and colloid osmotic pressure (COP), systemic and microcirculatory recovery, and oxygen delivery and consumption after resuscitation, which were assessed in the hamster chamber window preparation by intravital microscopy. Awake hamsters were subjected to 50% hemorrhage and were resuscitated with 25% of the estimated blood volume with 5%, 10%, or 20% HES solution. The increase in concentration led to an increase in COP (from 20 to 70 and 194 mmHg) and viscosity (from 1.7 to 3.8 and 14.4 cP). Cardiac index and microcirculatory and metabolic recovery were improved with HES 10% and 20% when compared with 5% HES. Oxygen delivery and consumption in the dorsal skinfold chamber was more than doubled with HES 10% and 20% when compared with HES 5%. This was attributed to the beneficial effect of restored or increased plasma COP and plasma viscosity as obtained with HES 10% and 20%, leading to improved microcirculatory blood flow values early in the resuscitation period. The increase in COP led to an increase in blood volume as shown by a reduction in hematocrit. Mean arterial pressure was significantly improved in animals receiving 10% and 20% solutions. In conclusion, the present results show that the increase in the concentration of HES, leading to hyperoncotic and hyperviscous solutions, is beneficial for resuscitation from hemorrhagic shock because normalization of COP and viscosity led to a rapid recovery of microcirculatory parameters.

Cardiac response is greater for colloid than saline fluid loading after cardiac or vascular surgery

To study the effects on volume expansion and myocardial function of colloids or crystalloids in the treatment of hypovolaemic hypotension after cardiac and major vascular surgery. A single-centre, single-blinded, randomized clinical trial at the intensive care unit of a university hospital. Patients (n=67) were subjected to a 90-min filling pressure-guided fluid challenge with saline 0.9% or the colloids gelatin 4%, hydroxyethyl starch 6% or albumin 5%. Biochemical variables and haemodynamics (transpulmonary thermodilution) were measured. An amount of 1800 (1300-1800) ml of saline or 1600 (750-1800) ml of colloid solution (P< 0.005) was infused. Colloid osmotic pressure (COP) decreased in the saline group and increased in the colloid groups (P< 0.001). Plasma volume increased by 3.0% (-18 to 24) in the saline versus 19% (-11 to 50) in the colloid groups (P< 0.001). Cardiac index increased by median 13% (ns) in the saline group and by 22% in the colloid groups (P<0.005). The rise in left ventricular stroke work index was greater in the colloid than in the saline groups. The different colloids were equally effective. The rise in cardiac index related to the rise in plasma volume and global end-diastolic volume, confirming plasma volume and preload augmentation by the fluid loading. After cardiac or major vascular surgery, the pressure- and time-guided fluid response is dependent on the type of fluid used. Colloid fluid loading leads to a greater increase in preload-recruitable cardiac and left ventricular stroke work indices than that with saline, because of greater plasma volume expansion following an increase in plasma COP.

Spiral artery associated restricted growth (SPAARG): a computer model of pathophysiology resulting from low intervillous pressure having fetal programming implications

Failure of adequate trophoblastic conversion of maternal spiral arteries is associated with intrauterine growth restriction (IUGR). In addition to poor oxygen delivery, raised spiral artery resistance reduces placental intervillous pressure. An iterative type computer model was formed by linking an existing model of the fetus and a new nine cotyledon placental model. Simulation of compression cuffing of the spiral arteries to progressively restrict uteroplacental flow was performed, while observing various fetal and placental variables. Water moved to the fetus in the cotyledonary core villi, and to the mother in the outer villous layers. While the fetus could match villous capillary pressure to changes in intervillous pressure, net transplacental water movement was minimal, but when spiral artery resistance was increased sufficiently to cause mean intervillous pressure to fall below that which the fetus could match, a net flow to the mother appeared. That continued until the resulting fetal blood hemoconcentration produced a sufficient increase in colloid osmotic pressure to restrict further loss. All cells within the fetal-placental unit are then required to operate in an abnormal ionic environment, which may significantly affect systems such as the renin–angiotensin set-point, with implications for post-natal homeostasis such as control of adult blood pressure. Furthermore, in vivo, cells of the feto-placental unit respond to the increased intravascular osmotic pressure by production of intracellular osmolytes in order to match intracellular and vascular/interstitial osmotic pressures. This may explain the observed effects on postnatal water balance in growth restricted infants and could also provide a possible mechanism for the association of the systemic maternal complications associated with impaired placentation and reduced intervillus flow.

Effect of concentration and hyaluronidase on restriction of hetastarch flux through lung interstitial segments

The transport properties of lung interstitium were studied by measuring the flow of hetastarch solution (2 and 6%) through 1-cm perivascular interstitial segments of rabbit lungs. Hetastarch (10 4–10 7 Da) solution has a colloid osmotic pressure similar to that of albumin solution. Driving pressure was 5 cm H 2O and mean interstitial pressure was 0 cm H 2O. The flows of 2 and 6% hetastarch solutions were measured before ( Q 1) and after ( Q 2) the addition of 0.02% hyaluronidase. Hetastarch molecular distributions in effluent samples were measured by high-performance size-exclusion chromatography (HPSEC) to determine sieving ratio ( C out/ C in, downstream-to-upstream concentration ratio). Hyaluronidase significantly ( P < 0.0004) increased flow sixfold, but the increase in flow ( Q 2/ Q 1) was reduced through the interstitium around smaller vessels. A similar behavior was observed with the flow of albumin solution without and with hyaluronidase. C out/ C in decreased monotonically with molecular weight, was greater with 6% than with 2% (low colloid osmotic pressure) hetastarch, and increased with hyaluronidase. Modeling the transport through uniform pores, equivalent pore radius was 10 and 15 nm with 2 and 6% hetastarch, respectively, and doubled with hyaluronidase. In conclusion, interstitial pores expand in response to an increase in colloid osmotic pressure both before and after tissue degradation by hyaluronidase.

Endotoxin increases both protein and fluid microvascular permeability in cat skeletal muscle.

To evaluate effects of lipopolysaccharide (endotoxin) on protein and fluid permeability in a whole organ skeletal muscle preparation. Controlled, prospective laboratory study. University research laboratory. Eleven adult male cats. The study was performed on the autoperfused and denervated calf muscles of the cat hindlimb placed in a fluid-filled plethysmograph. The endotoxin-induced change in the osmotic reflection coefficient for albumin was used as a measure of alteration in protein permeability of the microvascular wall, and the simultaneous change in capillary filtration coefficient was used as a measure of alteration in fluid permeability. Endotoxin as a bolus infusion (1 mg/kg iv) was given to six cats, and another five cats given only the vehicle (NaCl) were used as control. Arterial blood flow, arterial and venous blood pressures, total vascular resistance, and tissue volume changes were measured continuously. The ratio between the osmotic reflection coefficients for albumin on two occasions (before and about 1.5 hr after endotoxin infusion) was calculated from the Starling fluid equilibrium equation. This was performed by measurement of the maximum absorption rate from an isovolumetric state by an intravenous bolus infusion of 20% human albumin (0.6 g/kg) and the capillary filtration coefficient. Albumin concentrations were measured before and after the albumin infusion to correct for effects of difference in plasma volume on the induced increase in colloid osmotic pressure. We found that the osmotic reflection coefficient for albumin was reduced by 30% (p <.05), and the capillary filtration coefficient was increased by 31% (p <.05) by endotoxin. No changes were seen in the vehicle experiments. Endotoxin causes a significant increase in both protein and fluid microvascular wall permeability. These effects may explain the marked leakage of plasma to the interstitium that is often seen in critically ill patients with sepsis and systemic inflammatory response syndrome.

Pulmonary and Extrapulmonary Effects of Increased Colloid Osmotic Pressure During Endotoxemia in Rats

We tested the hypothesis that an increase in the blood colloid osmotic pressure (COP) that is maintained during early-stage endotoxemia may decrease fluid flux across capillaries and may reduce pulmonary and multiple-organ edema. Prospective study. Research laboratory in a hospital. Male albino Sprague-Dawley rats. Rats were anesthetized with pentobarbital, underwent tracheotomies, were cannulated in the femoral vein and artery, and were randomly assigned to the following four groups comprising 11 rats each: group I, controls (saline solution treatment); group II, albumin treatment (three doses of 1 g/kg 25% human albumin every 2 h); group III, endotoxin treatment with a single IV dose of 4 mg/kg endotoxin; and group IV, endotoxin and albumin-treatment (4 mg/kg endotoxin plus albumin treatment). Experiments lasted for 6 h while fluid intake was equally maintained in all groups. COP and other variables were measured every 2 h. To determine the water content of an organ, after the rat was killed, the lung, heart, kidney, intestine, and liver were removed. Albumin treatment alone (group II) generated significant increases in COP (maximum, 58% from the baseline measurement) but did not change the water content of the organ, compared with saline solution-treated controls. Endotoxin-treated rats (group III) developed significant reductions in COP, with significant increases in pulmonary, renal, and heart water content compared with controls. Albumin treatment in endotoxemic rats (group IV) significantly increased the COP without improving the endotoxemia-induced organ edema. Pulmonary edema, however, was increased further, compared with endotoxemia alone. COP elevation by albumin administration during the early stage of endotoxemia does not ameliorate pulmonary or multiple-organ edema and may aggravate pulmonary edema.

Correlation Between Increased Colloid Osmotic Pressure and the Resolution of Refractory Ascites After Transjugular Intrahepatic Portosystemic Shunt

This study compared the changes in serum albumin, globulin, and colloid osmotic pressure (COP) before and after transjugular intrahepatic portosystemic shunt (TIPS) or large volume paracentesis (LVP) in patients with ascites. Of 23 patients with refractory ascites, 17 had TIPS and 6 had LVP with infusion of albumin. Colloid osmotic pressure measurements were calculated, using the formula previously proposed by Hoefs: COP = A (1.058G + 0.163A + 3.11) where A = serum albumin and G = serum globulin. After 1 month, ascites resolved in 9 of the 17 patients who had TIPS and in none of the 6 who had LVP. Colloid osmotic pressure increased significantly in patients whose ascites resolved after TIPS. Colloid osmotic pressure did not change in the patients whose ascites did not resolve after TIPS, and COP decreased significantly in the LVP group. A statistically significant difference was found in the pre-TIPS COP measurements between those patients who had resolution of ascites and those who did not. A pre-TIPS COP of < or =20 mm Hg predicted resolution of ascites with an 88% sensitivity and a 78% specificity. Serum COP increased significantly in patients with resolution of ascites but remained unchanged in patients with persistent ascites after TIPS. Serum COP decreased after LVP. A statistically significant difference in the pre-TIPS COP was found between patients whose ascites resolved and patients having persistent ascites.

Correlation Between Increased Colloid Osmotic Pressure and the Resolution of Refractory Ascites After Transjugular Intrahepatic Portosystemic Shunt

Correlation Between Increased Colloid Osmotic Pressure and the Resolution of Refractory Ascites After Transjugular Intrahepatic Portosystemic Shunt

Increasing the Colloid Osmotic Pressure of Cardiopulmonary Bypass Prime and Normothermic Blood Cardioplegia Minimizes Myocardial Oedema and Prevents Cardiac Dysfunction

Our recent work demonstrated that normothermic continuous antegrade blood cardioplegia results in cardiac dysfunction related to myocardial oedema. This oedema was partially due to increased myocardial microvascular fluid filtration induced by crystalloid hemodilution. We hypothesized that increasing the colloid osmotic pressure of blood cardioplegia would stop fluid filtration into the cardiac interstitium, thus preventing myocardial oedema and cardiac dysfunction. Methods: We determined myocardial water content in six dogs by microgravimetry and myocardial lymph flow from the major prenodal cardiac lymphatic. Preload recruitable stroke work was derived from sonomicrometry and micromanometry. The dogs were subjected to normothermic cardiopulmonary bypass primed with 6% hetastarch and 1 h of normothermic continuous antegrade blood cardioplegia (4:1 blood:6% hetastarch colloid osmotic pressure 21 ± 2 mmHg) delivered at 50 mmHg perfusion pressure. Results: We found that despite increased colloid osmotic pressure, a small but significant increase in myocardial water content still occurred during blood cardioplegia. As myocardial Jymph flow virtually ceased during cardioplegia, myocardial microvascular filtration must have been present. However, increased myocardial lymph flow following cardioplegia resulted in complete oedema resolution associated with normal left ventricular performance post-cardiopulmonary bypass. Conclusions: Our data show that the plegic myocardium is prone to oedema formation because of both relatively enhanced fluid filtration and lymph flow cessation. We conclude that increasing the colloid osmotic pressure of normothermic blood cardioplegia minimizes myocardial oedema, thus preventing post-cardiopulmonary bypass cardiac dysfunction.

Increasing the colloid osmotic pressure of cardiopulmonary bypass prime and normothermic blood cardioplegia minimizes myocardial oedema and prevents cardiac dysfunction

Our recent work demonstrated that normothermic continuous antegrade blood cardioplegia results in cardiac dysfunction related to myocardial oedema. This oedema was partially due to increased myocardial microvascular fluid filtration induced by crystalloid hemodilution. We hypothesized that increasing the colloid osmotic pressure of blood cardioplegia would stop fluid filtration into the cardiac interstitium, thus preventing myocardial oedema and cardiac dysfunction. Methods: We determined myocardial water content in six dogs by microgravimetry and myocardial lymph flow from the major prenodal cardiac lymphatic. Preload recruitable stroke work was derived from sonomicrometry and micromanometry. The dogs were subjected to normothermic cardiopulmonary bypass primed with 6% hetastarch and 1 h of normothermic continuous antegrade blood cardioplegia (4:1 blood:6% hetastarch colloid osmotic pressure 21±2 mmHg) delivered at 50 mmHg perfusion pressure. Results: We found that despite increased colloid osmotic pressure, a small but significant increase in myocardial water content still occurred during blood cardioplegia. As myocardial lymph flow virtually ceased during cardioplegia, myocardial microvascular filtration must have been present. However, increased myocardial lymph flow following cardioplegia resulted in complete oedema resolution associated with normal left ventricular performance post-cardiopulmonary bypass. Conclusions: Our data show that the plegic myocardium is prone to oedema formation because of both relatively enhanced fluid filtration and lymph flow cessation. We conclude that increasing the colloid osmotic pressure of normothermic blood cardioplegia minimizes myocardial oedema, thus preventing post-cardiopulmonary bypass cardiac dysfunction.

Increased colloid osmotic pressure correlates with resolution of refractory ascites after transjugular intrahepatic portosystemic shunt (TIPS): C Hills, LS Miller, H Ter, T Schiano, S Bellary, M Black, G Cohen, D Ball. Depts. of Gastroenterology and Diagnostic Imaging, Temple University School of Medicine

Increased colloid osmotic pressure correlates with resolution of refractory ascites after transjugular intrahepatic portosystemic shunt (TIPS): C Hills, LS Miller, H Ter, T Schiano, S Bellary, M Black, G Cohen, D Ball. Depts. of Gastroenterology and Diagnostic Imaging, Temple University School of Medicine

Resolution of refractory ascites correlates with increased colloid osmotic pressure rather than decreased portal venous pressure after transjugular intraheptic portasystemic shunt (TIPSS): [formula omitted], C. Hills, H. Ter, T. Schiano, S. Bellary, M. Black, G. Cohen, D. Ball. Temple University Hospital, Philadelphia, PA

Resolution of refractory ascites correlates with increased colloid osmotic pressure rather than decreased portal venous pressure after transjugular intraheptic portasystemic shunt (TIPSS): [formula omitted], C. Hills, H. Ter, T. Schiano, S. Bellary, M. Black, G. Cohen, D. Ball. Temple University Hospital, Philadelphia, PA

各種成長因子によるＡＦＰ遺伝子発現の調節機構

Alpha-fetoprotein (AFP) and albumin gene expression are specific for hepatocytes. Since liver contains not only hepatocytes but also sinusoidal lining cells such endothelial cell, Kupffer cell, Ito cell and pit cell, the liver specific gene expression may be regulated by paracrine, autocrine and endocrine mechanism. In the present study, we analyzed the factors involved in the regulation of AFP and albumin gene expression using cultured human hepatoma cell lines. Epidermal growth factor and phorbol ester synergistically suppressed the AFP enhancer activity, resulting in the down-regulation of both AFP and albumin gene expression. Hepatocyte growth factor and transforming growth factor β1 suppressed the AFP gene expression through the inhibition of its promoter activity. Δ12-Prostaglandin J2, an active form of prostaglandin D2, repressed both AFP and albumin promoter activity. AFP and albumin mRNA levels were reversibly suppressed by the increased colloid osmotic pressure. Butyric acid, a natural fermentation product of colonic bacterial flora, inhibited the proliferation of HuH-7 human hepatoma cells in conjunction with the reciprocal regulation of AFP and albumin gene expression. These results indicate that AFP gene expression as well as albumin gene expression is physiologically regulated by varing factors in a paracrine fashion or an endocrine fashion through the arterial and the portal blood flow.

Regulation of corticotropin-releasing hormone release from human placental syncytiotrophoblasts by sodium nitroprusside

Failure of adequate trophoblastic conversion of maternal spiral arteries is associated with intrauterine growth restriction (IUGR). In addition to poor oxygen delivery, raised spiral artery resistance reduces placental intervillous pressure. An iterative type computer model was formed by linking an existing model of the fetus and a new nine cotyledon placental model. Simulation of compression cuffing of the spiral arteries to progressively restrict uteroplacental flow was performed, while observing various fetal and placental variables. Water moved to the fetus in the cotyledonary core villi, and to the mother in the outer villous layers. While the fetus could match villous capillary pressure to changes in intervillous pressure, net transplacental water movement was minimal, but when spiral artery resistance was increased sufficiently to cause mean intervillous pressure to fall below that which the fetus could match, a net flow to the mother appeared. That continued until the resulting fetal blood hemoconcentration produced a sufficient increase in colloid osmotic pressure to restrict further loss. All cells within the fetal-placental unit are then required to operate in an abnormal ionic environment, which may significantly affect systems such as the renin–angiotensin set-point, with implications for post-natal homeostasis such as control of adult blood pressure. Furthermore, in vivo, cells of the feto-placental unit respond to the increased intravascular osmotic pressure by production of intracellular osmolytes in order to match intracellular and vascular/interstitial osmotic pressures. This may explain the observed effects on postnatal water balance in growth restricted infants and could also provide a possible mechanism for the association of the systemic maternal complications associated with impaired placentation and reduced intervillus flow.

Alternative method of ultrafiltration after cardiopulmonary bypass

A revised circuit design for modified ultrafiltration is presented rendering the technique more convenient for use after cardiopulmonary bypass when blood cardioplegia is used. The procedure employs a hollow-fiber ultrafiltration device attached to the cardioplegia circuit. A bubble trap, heat exchanger, and a pressure monitor are incorporated as safety features. The technique has been used in 80 patients (30 pediatric and 50 adult) and has been associated with relevant increases in colloid osmotic pressure and hematocrit.

Hormonal changes in patients with severe chronic congestive heart failure treated by ultrafiltration.

Plasma atrial natriuretic peptide (ANP), antidiuretic hormone (ADH), plasma renin activity (PRA), and circulatory haemodynamics were studied in five patients with chronic congestive heart failure undergoing ultrafiltration on two consecutive days. The patients were in the New York Heart Association class IV, and were considered candidates for heart transplantation. A mean of 3.3 +/- 0.5 litres of fluid was removed during each ultrafiltration. Plasma ANP concentration remained unchanged during ultrafiltration: 369 +/- 151 pg/ml at start and 316 +/- 116 pg/ml at the end, while plasma ADH concentration and PRA increased from 5.1 +/- 2.1 to 7.5 +/- 3.4 pg/ml (P less than 0.02), and 5.9 +/- 3.0 to 7.7 +/- 3.2 ng/ml (P less than 0.03) respectively (n = 10). After treatment, plasma ADH and PRA declined to baseline values within 1 h. Pulmonary artery, pulmonary capillary wedge, and right atrial pressures decreased significantly, while blood pressure and heart rate remained constant during ultrafiltration. A volume of 3.3 +/- 0.5 litres of fluid was removed, and caused an increase in colloid osmotic pressure from 22.0 +/- 3.0 to 33.7 +/- 3.9 mmHg (P less than 0.02). It was unexpected that plasma ANP concentration did not decline. Due to long-standing severe heart failure the atrial wall may have lost some of its elastic properties, resulting in less ability to adapt to reduced filling pressures. Accordingly, atrial wall stretch remained unchanged, explaining the constant ANP levels. Ultrafiltration treatment caused an increased responsiveness to diuretic therapy, and four patients survived long enough to receive heart transplants.