Plasma Colloid Osmotic Pressure Research Articles

Mechanisms for reduced colloid osmotic pressure in preeclampsia

The determinants of plasma colloid osmotic pressure were studied in 32 patients with preeclampsia and their matched control subjects. Although plasma colloid osmotic pressure was significantly related to preeclampsia, its severity, and proteinuria, it was most highly correlated with an elevated fibronectin level, suggesting that endothelial injury, rather than proteinuria, is the major mechanism of reduced colloid osmotic pressure in preeclampsia.

Osmotic flows across the blood-joint barrier.

The effective osmotic pressure across the blood-joint barrier is a key factor controlling synovial fluid volume and joint effusions. The effect of plasma colloid osmotic pressure (COP) on trans-synovial flow was studied directly in rabbit knees expanded by intra-articular fluid infusion. The synovial microcirculation was perfused with blood of varying COP. Absorption of fluid from the joint cavity was a linear function of COP; but albumin COP was only 78% effective across the blood-joint interface. Hyperosmolar solutions of small solutes (e.g., glucose) generated transient osmotic flows across the blood-joint barrier, but far less effectively than albumin. The hydraulic permeability of synovium increased at pathological intra-articular pressures--a phenomenon of potential importance to effusion kinetics.

Low colloid osmotic pressure in very low birthweight infants receiving assisted ventilation.

Plasma colloid osmotic pressure (COP) was measured in three groups of very low birthweight infants. Babies in Group 1 (n = 8) were breathing spontaneously and had no respiratory disease. Those in Group 2 (n = 9) received assisted ventilation for hyaline membrane disease (HMD), and those in Group 3 (n = 7) received assisted ventilation for other reasons (five apnoea, two pneumonia). Both assisted ventilation groups had lower mean COP values than spontaneously breathing infants. Mean values (s.e.m.) for Groups 1, 2 and 3, respectively, were: 15.3 (0.6), 11.3 (0.4) and 11.9 mmHg (0.5) (P less than 0.001) on Day 1; and 15.2 (0.4), 12.9 (0.4) and 12.8 mmHg (0.3) (P less than 0.001) on Day 2. The increase from Day 1 to Day 2 was significant for those with HMD (P less than 0.05). Colloid osmotic pressure correlated with mean blood pressure (r = 0.51; P less than 0.001) but not with birthweight, gestation, crystalloid fluid intake or pH. The role of low COP in the pathogenesis of acute respiratory failure in infants with uncomplicated HMD is unclear, but such low COP may contribute to development of pulmonary oedema as a complication, particularly if the ductus arteriosus is still patent and the infants are given high volume intravenous fluids.

Effects of crystalloid and colloid fluids on extravascular lung water in hypoproteinemic dogs.

We compared the effect of crystalloid to colloid fluid infusion on extravascular lung water (EVLW) in hypoproteinemic dogs. Plasmapheresis was used to decrease plasma colloid osmotic pressure (COP) to less than 40% of its base-line level. Five animals were then infused with 0.9% sodium chloride (saline), five with 5% human serum albumin (albumin), and five with 6% hydroxyethyl starch (hetastarch) to increase the pulmonary arterial occlusive pressure by 10 Torr in comparison to the postplasmapheresis level for a 5-h study interval. On completion of the procedure, the lungs were harvested and EVLW measured by the blood-free gravimetric technique. Three to six times the volume of saline compared with albumin or hetastarch (P less than 0.001) was infused. In the saline animals, COP was decreased to 3.3 +/- 1.3 Torr, whereas COP was increased to 18.1 +/- 1.4 Torr in albumin animals (P less than 0.001) and 20.1 +/- 1.6 Torr in the hetastarch group (P less than 0.001). The saline-treated dogs developed gross signs of systemic edema. The EVLW was 8.1 +/- 0.9 ml/kg in saline animals compared with 5.3 +/- 2.1 ml/kg in the albumin (P less than 0.05) and 4.1 +/- 1.4 ml/kg in the hetastarch (P less than 0.01) groups. These data indicate that crystalloid fluid infusion during hypoproteinemia is associated with the development of both systemic and pulmonary edema.

Transcapillary Fluid Forces during Dehydration in Two Amphibians

Bufo marinus is more tolerant of dehydration than Rana catesbeiana. Dehydration led to increases in plasma sodium, protein, and hematocrit. The increases in plasma protein concentration were greater in both species than predicted from passive concentration during dehydration, indicating protein redistribution to the vascular space. Increases in hematocrit with dehydration were delayed in Bufo, indicating that plasma volume was maintained. The colloid osmotic pressure of plasma increased with protein concentration during dehydration, as predicted by data for mammals. Venous blood pressures did not vary with dehydration in either species. Interstitial fluid pressure became more negative with dehydration. The balance of transcapillary fluid forces predict ultrafiltration during all stages of dehydration in Rana and during dehydration below 24% in Bufo. The transcapillary forces do not predict the fluid redistribution to the plasma space, which is consequently attributed to lymphatic return. The changes in plasma protein concentration during dehydration are consistent with lymphatic return. Greater interstitial fluid volumes may be an important corollary of enhanced tolerance to dehydration.

A reply

AnaesthesiaVolume 42, Issue 5 p. 571-572 Free Access A reply K.M. Hillman, K.M. Hillman The Liverpool Hospital, Liverpool, NSW 2170. AustraliaSearch for more papers by this author K.M. Hillman, K.M. Hillman The Liverpool Hospital, Liverpool, NSW 2170. AustraliaSearch for more papers by this author First published: May 1987 https://doi.org/10.1111/j.1365-2044.1987.tb04092.xAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL No abstract is available for this article. References 1 Nielsen OM, Engell HC. The importance of plasma colloid osmotic pressure for interstitial fluid volume and fluid balance after elective abdominal vascular surgery. Annals of Surgery 1986; 203: 25– 9. Volume42, Issue5May 1987Pages 571-572 ReferencesRelatedInformation

Interaction between renal prostaglandins and angiotensin II in controlling glomerular filtration in the dog.

Although previous studies suggest that the renal vasoconstrictor effects of angiotensin II (ANG II) are normally confined to the efferent arterioles, the mechanisms that prevent ANG II from constricting preglomerular vessels are still unclear. In the present study, the role of prostaglandins (PG) in protecting preglomerular vessels from ANG II constriction was examined in dogs with normal or non-filtering kidneys in which ANG II formation was blocked with captopril and renal artery pressure was servo-controlled at 75-80 mmHg. Before PG blockade (n = 6), ANG II infusion (20 ng min-1 kg-1) decreased renal blood flow (RBF) by 54 +/- 4%, but did not change glomerular filtration rate (GFR) significantly. After PG blockade (n = 6), ANG II infusion decreased GFR by 37 +/- 7% and RBF by 56 +/- 6%, while increasing calculated preglomerular resistance much more than before PG blockade. In another group of dogs, secondary changes in renal resistances, due to tubuloglomerular feedback, were prevented by occluding the ureter during mannitol diuresis until glomerular filtration ceased. After inhibition of tubuloglomerular feedback in non-filtering kidneys (n = 7), ANG II decreased RBF by 40 +/- 3% and increased glomerular hydrostatic pressure, estimated from stop-flow ureteral pressure and plasma colloid osmotic pressure, by 8.7 +/- 1.7 mmHg. Postglomerular resistance increased by 91 +/- 12% while preglomerular resistance was unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

Transcapillary fluid dynamics during the menstrual cycle

Transcapillary fluid dynamics in the follicular and luteal phase in women without symptoms of premenstrual syndrome were studied. Interstitial colloid osmotic pressure was measured by the “wick” method and interstitial hydrostatic pressure by the “wick-in-needle” method in subcutaneous tissue on the thorax and ankle. From follicular to luteal phase, the following changes were observed: Colloid osmotic pressures were significantly reduced, both in plasma (mean 2.5 mm Hg) and in the interstitium (thorax mean 1.9 mm Hg and ankle mean 2.0 mm Hg). The interstitial hydrostatic pressures did not change. There were no significant changes in serum albumin, hemoglobin, or hematocrit. A slight, but significant, weight gain was observed (mean 0.7 kg). The reduced plasma and interstitial colloid osmotic pressures in the luteal phase may be due to water retention, but the observed reductions in colloid osmotic pressures are probably not fully explained by simple dilution. A reduction in total protein mass in the luteal phase is suggested.

The direct measurement of plasma colloid osmotic pressure is superior to colloid osmotic pressure derived from albumin or total protein.

Plasma colloid osmotic pressure (COP) has been calculated from both serum albumin concentration and plasma total protein concentration. These values have been compared to those measured directly using a membrane-transducer oncometer in a group of normal subjects, in a group of critically-ill patients with a variety of primary diagnoses and in a group of hypovolaemic patients before and after plasma volume replacement with 6% hydroxyethyl starch solution. In the normal samples, COP calculated from albumin (COPalb) underestimated the measured COP (COPm) by mean of 2.0 mmHg (p less than 0.002), with correlation coefficient r = 0.39(n/s). Similarly, the COPalb underestimated COPm by a mean of 5.7 mmHg (p less than 0.001) in the critically ill patient group; r = 0.38 (p less than 0.02). Furthermore, in the patients receiving plasma volume replacement serum albumin concentration fell by 13.1% (p less than 0.001) whilst COPm increased by 11.5% (p less than 0.002). In the normal subjects COP calculated from total protein concentration (COPtp) underestimated the COPm by 1.5 mmHg (p less than 0.02) with r = 0.65 (p less than 0.01). Conversely, in the patient samples, mean COPtp overestimated COPm by 3.5 mmHg (p less than 0.001) with r = 0.73 (p less than 0.002). We conclude that COPalb is an inadequate estimate of COPm particularly in patients where its use may have important clinical consequences. COPtp provides a reasonable estimate of COPm in normal subjects but in patients samples, where albumin: globulin ratio is low COPtp overestimates substantially in many cases. We advocate the direct measurement of COP in critically-ill patients.

Renal hemodynamic, fluid volume, and arterial pressure changes during hyperproteinemia.

The chronic effects of hyperproteinemia on renal hemodynamics, fluid volume, and arterial pressure were determined in six conscious dogs over a 32-day period. Plasma protein concentration was increased by intravenous infusion of approximately 300 ml/day of previously collected autologous plasma, and the responses to changes in sodium intake were studied. By the end of a 9-day period of hyperproteinemia and normal sodium intake, plasma protein concentration had increased 2.2 g/dl, plasma colloid osmotic pressure had increased 7-8 mmHg, mean arterial pressure had increased 12 mmHg, glomerular filtration rate (GFR) had increased 15%, estimated renal plasma flow (ERPF) had increased 51% primarily due to renal vasodilatation, and filtration fraction had decreased 23%. Also, sodium balance was negative, water balance was positive, sodium iothalamate space had increased, plasma sodium concentration had decreased, and the relationship between mean arterial pressure and urinary sodium excretion was shifted to the right along the arterial pressure axis. In conclusion, long-term increases of plasma protein concentration result in a marked increase in ERPF as well as significant increases in GFR, extracellular fluid volume, and arterial pressure.

The absence of an arterial pressure effect on filtration by perfused glomeruli of the hagfish, Eptatretus stouti (Lockington).

Single renal corpuscles of hagfish were perfused with a Ringer solution containing Ficoll 70 to simulate the colloid osmotic pressure of hagfish plasma. Simultaneous measurements were made of single glomerulus filtration rate (SGFR), perfusion pressure and the pressure in a vessel of the renal vasculature. The results confirm that SGFR is independent of pressure in the glomerular capillaries (PGC). The results also suggest that flow through glomeruli and SGFR are closely linked. Studies of the pressures in glomerular capillaries during periods when the perfusion rate was varied indicate that PGC reflects the area of the active capillaries and the rate of perfusion. Therefore, in the hagfish, PGC appears to be an effect of factors that cause glomerular filtration, not the main cause of that process.

The importance of plasma protein for blood volume and blood pressure homeostasis

To evaluate the influence of plasma protein concentration and colloid osmotic pressure (COP) on blood volume and blood pressure, we studied 40 patients with the nephrotic syndrome (plasma protein 41.1 +/- 5.3 g/liter, COP 10.9 +/- 2.2 mm Hg) and 43 patients with chronic renal failure (plasma protein 65.0 +/- 5.8 g/liter, COP 22.4 +/- 3.0 mm Hg) at overhydration, during gradual edema removal to normal hydration, and occasionally, to mild dehydration. The number of measure points was 113 in the nephrotic syndrome and 92 in renal failure. In both groups blood volume was normal at normal extracellular fluid volume (ECFV). Elevation of ECFV to 300% of normal in the nephrotic syndrome occurred with only a modest elevation of blood volume (NS). Elevation of ECFV to 200% of normal in the patients with renal failure was attended by a major elevation of blood volume (P less than 0.01). Reduction of ECFV to about 10% below normal was accompanied by parallel blood volume reduction in both groups. Blood pressure was comparable at normohydration, and increased to clearly hypertensive levels only in the renal failure group with increasing ECFV and blood volume (P less than 0.01). No major blood pressure difference was observed between normal and subnormal hydration, but hypotension was observed twice in the nephrotic group. Apparently, patients with severe hypoproteinemia due to the nephrotic syndrome are generally able to preserve their blood volume even when free of edema. However, their blood volume is not elevated in overhydration, in contrast to patients with renal failure who are normoproteinemic. This difference in regulation of extracellular fluid distribution is probably related to the hypoproteinemia, and its effect to reduce tissue-fluid protein.

A New Look at Pulmonary Edema

Fluid accumulation within the lungs is a potentially fatal complication in critically ill patients. Sepsis and increased microvascular permeability are often implicated as the cause. This article shows that edema can be prevented by lowering systemic venous pressure (to permit pulmonary lymph to drain), by lowering pulmonary arterial pressure, and by maintaining plasma colloid osmotic pressure. It points out the importance of understanding the basic physiology behind pulmonary edema and therapeutic measures.

Transcapillary colloid osmotic gradient and body fluid volumes in renal failure

The aim was to study the transcapillary fluid balance in dialysis patients during and after ultrafiltration. Plasma and subcutaneous interstitial fluid (wick technique) colloid osmotic pressure, plasma volume (I125-albumin space) and extracellular fluid volume (radiosulfate space) were measured in nine patients on maintenance hemodialysis before (pre-dialysis state) and after (dry-weight state) ultrafiltration. In the pre-dialysis state, interstitial colloid osmotic pressure was reduced compared to normal controls (12.7 +/- 3.5 versus 15.8 +/- 2.7 mmHg, mean values +/- SD) and transcapillary colloid osmotic gradient increased (15.3 +/- 3.0 versus 12.8 +/- 2.7 mmHg). Ultrafiltration resulted in a parallel decrease of plasma volume and interstitial fluid volume of 19 to 20%, and an increase in mean interstitial colloid osmotic pressure of 3.4 mmHg and in mean transcapillary colloid osmotic gradient of 1.9 mmHg. The mean ultrafiltration rate was 21.9 +/- 1.9 ml/min and the plasma refilling rate was 16.5 +/- 2.7 ml/min. It is concluded that the changes in plasma and interstitial fluid colloid osmotic pressure tend to preserve plasma volume and limit the interdialytic increase in interstitial fluid volume.

Transcapillary fluid balance in pre-eclampsia.

The fluid transport between the plasma and interstitial fluid compartment is governed by the Starling forces, i.e. the capillary pressure (Pc), interstitial fluid hydrostatic pressure (Pi) and colloid osmotic pressure in plasma (COPp) and interstitial fluid (COPi). Interstitial fluid was collected from subcutaneous tissue on the thorax and ankle by implanted wicks and Pi was measured using the 'wick-in-needle' technique. In pre-eclampsia, COPp is reduced due to hypoproteinaemia and this predisposes towards loss of fluid from the vascular compartment. An important oedema-preventing mechanism is reduction of COPi, which serves as a homeostatic buffer against increased capillary filtration. This mechanism works in moderate, but not in severe pre-eclampsia. A higher COPi was found both at the thorax (8.3 vs 7.0 mmHg) and ankle (5.9 vs 3.9 mmHg) in the group with severe pre-eclampsia compared with the group moderate pre-eclampsia, in spite of a significant reduction in COPp (15.5 vs 19.9 mmHg). These findings suggest that an increased microvascular permeability of plasma proteins to subcutaneous tissue contributes to COPp reduction in severe pre-eclampsia.

An evaluation of ultrafiltration as treatment of therapy-resistant cardiac edema.

In six patients with therapy-resistant cardiac edema, ultrafiltration on two consecutive days removed on an average 7750 ml fluid and reduced body weight by 7.3 kg. A difference between the mean ultrafiltration rate (17.4 ml/min) and the calculated plasma refilling rate (12.7 ml/min) led to a reduction in plasma volume during treatment together with an increase in plasma colloid osmotic pressure. Systemic blood pressure, heart rate and cardiac output were unchanged during ultrafiltration while systemic vascular resistance increased and pulmonary capillary wedge pressure and right atrial pressure decreased significantly. No complications were recorded during or after treatment. Ultrafiltration is a safe method of fluid removal in patients with therapy-resistant cardiac edema and can be used as preparation for cardiac catheterization or surgery.

A study on oedema mechanism in nephrotic syndrome

Colloid osmotic pressure in plasma (COPp) and interstitial fluid (COPi), plasma volume (PV) and interstitial fluid volume (IFV) were measured in 14 patients with hypoproteinaemia due to glomerulonephritis and in five healthy controls. In controls, COPp averaged 24.2 mmHg and COPi 12.0 mmHg. In patients with COPp above 12 mmHg, COPi was reduced nearly identical to the fall in COPp. The transcapillary COP gradient (COPp-COPi) was maintained, and PV and IFV were unchanged. When COPp was reduced below 12 mmHg, the transcapillary COP gradient was decreased. Both IFV increased and renal fluid retention occurred. This study demonstrates the relationship between COPp, transcapillary fluid transport, and renal fluid retention in nephrotic syndrome.

The importance of plasma colloid osmotic pressure for interstitial fluid volume and fluid balance after elective abdominal vascular surgery.

The relationships between plasma colloid osmotic pressure (COPp) and interstitial fluid volume (IFV) as well as postoperative fluid balance were investigated in a prospective study involving 53 patients undergoing elective abdominal aortic reconstruction. The patients were divided into four groups according to pre- and postoperative blood replacement and fluid therapy programs whereby a continuum of postoperative COPp-values between 33 and 16 mmHg was obtained. Measurements were done before the operation and on days 1 and 4 after surgery. After surgery, COPp below 20 mmHg led to increased IFV. On day 1, COPp was linearly correlated to the total amount of fluid retained during the day of operation. A positive fluid balance of 3 L on this day ensured unchanged extracellular fluid volume (ECV). Of the 3 L, 1.5 L was insensible water loss and 1.5 L had moved into the cells. On day 4 after surgery, COPp below 22 mmHg was associated with increased plasma volume. The authors suggest that COPp be maintained above 20 mmHg after major surgery, and positive fluid balance should not exceed 5 L during the day of operation.

食道癌症例における血液製剤使用状況及び血しょう製剤適正使用に関する考察 食道癌手術の呼吸循環動態よりの検討

From 1980 to 1984, resections of esophageal cancer were performed upon 167 out of 281 patients in our department.The volume of blood loss and blood transfusion in those patients were analyzed. The average blood loss in operation was 1021±554ml, and each case required about 5 units blood transfusion. 10 units packed cells and 10 units fresh frozen plasma were prepared in cases of radical operation for esophageal cancer. This volume was sufficient for the maximum surgical blood order schedule (MSBOS) for esophageal cancer surgery.In order to study the usage of colloid in all resectable cases in 1981 and 1982, various hemodynamic indicators were investigated using a Swan-Ganz flow directed catheter. Plasma colloid osmotic pressure (PCOP) was measured by membranosmometer, and alveolar-arterial oxygen difference (A-aDO2) calculated by the blood gas analysis was measured. The results were obtained as follows: in the early postoperative period, values of PCOP-PA (mean pulmonary pressure) decreased remarkably, and A-aDO2 increased, compared with the preoperative values of those factors. Those results indicate that pulmonary water retension may be estimated by calculating those factors and the patients who underwent radical surgery for esophageal cancer may be easily susceptible to pulmonary complications, especially, pulmonary edema.Transfusion of fresh frozen proteins (FFP) is effective in maintaining normal plasma protein level and plasma albumin level during the catabolic phase after operation, but the usage of albumin as nutritional support is not recommended from the metabolic point of view.Hyperalimentation by active and appropriate combination of enteral and parenteral nutrition is one of the most practical and important therapies for patients with hypoproteinemia throughout the course of treatment for cancer of the esophagus.

Colloid osmotic pressure changes in human whole blood and separated plasma in vitro with changes in CO 2 content and pH

1. 1. Colloid osmotic pressure (COP) and pH were measured on the true plasma of human blood from five subjects tonometered with different concentrations of carbon dioxide. Measurements were also made on their separated plasma. 2. 2. COP (mmHg) of true plasma obtained from tonometered whole blood varied in proportion to the bicarbonate concentration (mEq/1): COP = 0.056 [HCO 3 −] + 23.3 3. 3. In separated plasma, as CO 2 concentration increased, COP decreased as pH decreased: COP = 1.99 (pH) + 11.0. 4. 4. When the change in COP due to the change in pH was subtracted from the observed change of COP due to CO 2 exposure of whole blood, the difference was the change of COP due to the shift of fluid between plasma and red cells: COP adjusted for pH = 0.131 [HCO 3 −] + 21.5. The COP values of tonometered whole blood and separated plasma are taken to be equal at a pH of 7.40 (at the mixed venous point). 5. 5. The change in COP, adjusted for pH, for a given change in pCO 2 is in keeping with the amount of fluid shift calculated from the measured changes in hematocrit and plasma protein concentration. 6. 6. An error in a previous paper (Kakiuchi et al., J. appl. Physiol. 44, 474–478, 1978) had led to an overestimation of the COP change from the exposure of whole blood to CO 2 in vitro.