Albumin, HES 120 and dextran 70 as adjuvants to red blood cell concentrates: a study on colloid osmotic pressure changes in vitro

Colloid osmotic pressure of contemporary and novel transfusion products

Background and Objectives

Colloid osmotic pressure (COP) is a principal determinant of intravascular fluid homeostasis and a pillar of fluid therapy and transfusion. Transfusion‐associated circulatory overload (TACO) is a leading complication of transfusion, and COP could be responsible for recruiting additional fluid. Study objective was to measure COP of blood products as well as investigate the effects of product concentration and storage lesion on COP.

Materials and Methods

Three units of each product were sampled longitudinally. COP was measured directly as well as the determinants thereof albumin and total protein. Conventional blood products, that is red blood cell (RBC), fresh‐frozen plasma (FFP) and platelet concentrates (PLTs), were compared with their concentrated counterparts: volume‐reduced RBCs, hyperconcentrated PLTs, and fully and partially reconstituted lyophilized plasma (prLP). Fresh and maximally stored products were measured to determine changes in protein and COP. We calculated potential volume load (PVL) to estimate volume recruited using albumin's water binding per product.

Results

Colloid osmotic pressure varies widely between conventional products (RBCs, 1·9; PLTs, 7·5; and FFP, 20·1 mmHg); however, all are hypooncotic compared with human plasma COP (25·4 mmHg). Storage lesion did not increase COP. Concentrating RBCs and PLTs did not increase COP; only prLP showed a supraphysiological COP of 47·3 mm Hg. The PVL of concentrated products was lower than conventional products.

Conclusion

Colloid osmotic pressure of conventional products was low. Therefore, third‐space fluid recruitment is an unlikely mechanism in TACO. Concentrated products had a lower calculated fluid load and may prevent TACO. Finally, storage did not significantly increase oncotic pressure of blood products.

Acute kidney injury in postoperative shock: is hyperoncotic albumin administration an unrecognized resuscitation risk factor?

BACKGROUND

The use of hyperoncotic albumin (HA) for shock resuscitation is controversial given concerns about its cost, effectiveness, and potential for nephrotoxicity. We evaluated the association between early exposure to hyperoncotic albumin (within the first 48 h of onset of shock) and acute organ dysfunction in post-surgical patients with shock.

METHODS

This retrospective, cohort study included 11,512 perioperative patients with shock from 2009 to 2012. Shock was defined as requirement for vasopressors to maintain adequate mean arterial pressure and/or elevated lactate (> 2.2 mmol/L). Subsets of 3600 were selected after propensity score and exact matching on demographics, comorbidities, and treatment variables (> 30). There was a preponderance of cardiac surgery patients. Proportional odds logistic regression, multivariable logistic regression or Cox proportional hazard regression models measured association between hyperoncotic albumin and acute kidney injury (AKI), hepatic injury, ICU days, and mortality.

RESULTS

Hyperoncotic albumin-exposed patients showed greater risk of acute kidney injury compared to controls (OR 1.10, 95% CI 1.04, 1.17. P = 0.002), after adjusting for imbalanced co-variables. Within matched patients, 20.3%, 2.9%, and 4.4% of HA patients experienced KDIGO stages 1-3 AKI, versus 19.6%, 2.5%, and 3.0% of controls. There was no difference in hepatic injury (OR 1.16; 98.3% CI 0.85, 1.58); ICU days, (HR 1.05; 98.3% CI 1.00, 1.11); or mortality, (OR 0.88; 98.3% CI 0.64, 1.20).

CONCLUSIONS

Early exposure to hyperoncotic albumin in postoperative shock appeared to be associated with acute kidney injury. There did not appear to be any association with hepatic injury, mortality, or ICU days. The clinical and economic implications of this finding warrant further investigation.

Hyperoncotic colloids and acute kidney injury: a meta-analysis of randomized trials

Introduction

It has been hypothesized that hyperoncotic colloids might contribute to acute kidney injury (AKI). However, the validity of this hypothesis remains unclear.

Methods

A meta-analysis was conducted of randomized controlled trials evaluating AKI after infusion of hyperoncotic albumin and hydroxyethyl starch (HES) solutions. Mortality was a secondary endpoint. Eligible trials were sought by multiple methods, and the pooled odds ratios (OR) for AKI and death and 95% confidence intervals (CI) were computed under a random effects model.

Results

Eleven randomized trials with a total of 1220 patients were included: 7 evaluating hyperoncotic albumin and 4 hyperoncotic HES. Clinical indications were ascites, surgery, sepsis and spontaneous bacterial peritonitis. Hyperoncotic albumin decreased the odds of AKI by 76% (OR, 0.24; CI, 0.12-0.48; P < 0.0001), while hyperoncotic HES increased those odds by 92% (OR, 1.92; CI, 1.31-2.81; P = 0.0008). Parallel effects on mortality were observed, with hyperoncotic albumin reducing the odds of death by 48% (OR, 0.52; CI, 0.28-0.95; P = 0.035) and hyperoncotic HES raising those odds by 41% (OR, 1.41; CI, 1.01-1.96; P = 0.043).

Conclusions

This meta-analysis does not support the hypothesis that hyperoncotic colloid solutions per se injure the kidney. Renal effects appear instead to be colloid-specific, with albumin displaying renoprotection and HES showing nephrotoxicity.

Influence of intravascular molecular weight of hydroxyethyl starch on platelets

Complications concerning the blood coagulation have been observed repeatedly after administration of highly substituted, high molecular weight hydroxyethyl starch (HES), but it has not been examined as to how intravascular molecular weight and degree of substitution of HES influence platelet number and volume after repeated administration. Thirty patients with cerebrovascular diseases were treated for 10 days with hemodilution. 500 to 1500 ml of HES 200/0.62(n=10), HES 200/0.5(n=10) or HES 40/0.5(n=10) were infused daily. During the first days, the number of platelets was not lowered beyond the dilution effect, but at the end of the therapy the number of platelets had increased in all 3 groups beyond the initial value. Platelet volume was lowered significantly in the 3 groups. HES 200/0.62 caused the largest drop in platelet volume (-10%, p<0.01). A possible explanation could be that HES macromolecules are attached to platelets or are phagocytized by them. The larger platelets are then broken down and, to compensate the loss, more thrombocytes are released. A correlation between the molecular weight of HES and the breakdown rate of the platelets can be suspected, because HES 200/0.62 has the highest intravascular mean molecular weight(121 kD) and the largest effect on platelet volume.

Replacement of major surgical blood loss by hypo-oncotic or conventional plasma substitutes

The purpose of the study was to examine the effects of hypooncotic 4% hydroxyethyl starch 120/0.7, 3% dextran 70, 5% albumin and hyperoncotic 6% hydroxyethyl starch 120/0.7 on the perioperative colloid osmotic pressure (COP), albumin and protein concentrations and fluid balance. The plasma substitutes were used with red cell concentrates to replace blood loss with equal volume in sixty major abdominal or urological surgeries. A special effort was made to keep replacements and losses at even volumes constantly and to avoid fluctuation of blood volume. The blood specimen were obtained before induction, after each 20% blood loss, at the end of the recovery room phase and on the three following postoperative mornings. There were significant differences in the peroperative and immediate postoperative COPs. However, these differences had vanished by the first postoperative morning. COP was preserved above 16 mmHg in all groups throughout the study. The identical peroperative albumin and protein concentrations of the synthetic colloid groups suggests that their volume effect was the same, regardless of the varying COP. During the observation period there were no significant differences among the groups concerning the diuresis and the fluid balances. We conclude, that the hypooncotic 4% HES 120 and 3% dextran 70 solutions provide the same clinical effect as 6% HES 120 solution. Consequently less colloid is needed, which allows the use of greater volumes of the dilute colloid solutions in replacement therapy.

Colloid osmotic pressure of plasma replacement fluids

Colloid osmotic pressure (COP) of some of the most frequently used plasma replacement fluids was measured with a colloid osmometer. COP of 4% human albumin solutions was only half that of normal human serum (13.6 +/- 0.6 vs. 27.5 +/- 2.7 mmHg (1.8 +/- 0.1 vs. 3.7 +/- 0.4 kPa)) (mean +/- s.d.), whereas COP of 20% human albumin solutions was eight times higher (196.0 +/- 12.3 mmHg (26.1 +/- 1.6 kPa)). Enhancing the protein concentration from 4% to 20% in the human albumin solutions increased COP 14-fold, reflecting the exponential relationship between protein concentration and COP of a solution. Fresh donor plasma furnished by the hospital blood-bank had a COP about 30% below normal human serum (18.1 +/- 1.3 mmHg (2.4 +/- 0.2 kPa)), due to dilution during preparation. Dextran 70 (6%) had a COP more than twice, and Ringer-Dextran 60 (3%) about 75% of that of normal human serum. Dextran 40 (10%) and gelatin (3.5%, Haemaccel) leaked markedly through the membrane of the colloid osmometer, making acceptable measurements impossible. Seven different hydroxyethyl starch (HES) solutions were measured, and the COP varied between half and 3 times that of normal human serum, depending on molecular weight and concentration of the HES.