Malchesky Ps

Conjugated human hemoglobin as a physiological oxygen carrier--pyridoxalated hemoglobin polyoxyethylene conjugate (PHP).

Problems associated with specific physiological properties of Hb-based blood substitutes, such as a low P50, short plasma half-life and nephrotoxicity are still major issues to be addressed. Extensive investigations aimed at overcoming these problems have resulted in the preparation of pyridoxalated-hemoglobin-polyoxyethylene conjugate (PHP). PHP was developed from human hemoglobin by two major chemical modifications; pyridoxylation for the purpose of lowering the oxygen affinity (P50 of 19.5 ± 1.2 mmHg), and coupling with polyoxyethylene (POE) to increase its molecular weight (to approximately 90 kdaltons). The circulating half-life of PHP is about 40 hours in dogs. Toxicologicai and physiological studies including renal function assessments have demonstrated that PHP does not have untoward effects on major organ functions. Its efficacy in transporting oxygen has been shown in ET and intracoronary perfusion, and in in vitro studies with sickle cells. Studies to date suggest that PHP is a promising candidate as a physiological oxygen carrier. In this paper the properties of PHP, its safety and efficacy aspects, and its potential as a clinical oxygen carrier are reviewed based on studies conducted in the Authors laboratory.

In Vivo Evaluation of a Pyridoxalated-Hemoglobin-Polyoxyethylene Conjugate

A pyridoxylated-hemoglobin-polyoxyethylene conjugate (PHP) was developed from outdated human red cell hemoglobin through chemical modifications. The PHP has a mean molecular weight of approximately 90,000 daltons, with an acceptable P50 of 22 +/- 0.7 mmHg. This report describes exchange transfusion studies (ET) to a final hematocrit of 5 +/- 2% (n = 5) with PHP in mongrel dogs. Hespan (a plasma expander) was used as a control (n = 6). All the animals with PHP tolerated the procedure well and have survived more than 8 months to date. Five out of the six dogs receiving Hespan died within a week (p = 0.004). Reduction of hematological and coagulation parameters occurred following the ET and returned to the normal range by 4 weeks post ET. Serum electrolytes and renal function parameters (urea, creatinine) remained in the normal range. A transient slight increase in the hepatic enzyme SGOT was observed. At 2 weeks post ET open biopsies of major organs showed vacuolized cells in the liver and kidneys. Normal histology was noted at 3 months. The oxygen transporting properties examined showed effective oxygen delivery to the tissues for 6 hours post ET. PHP continued to transport oxygen for up to 48 hours studied post ET. Half-life of PHP in the circulation was 36.3 +/- 3.5 hours. Urinary loss of hemoglobin measured up to 48 hours after ET was 9.4 +/- 1.6% of the injected net hemoglobin. The PHP effectively supported life at lethal levels of anemia and is a physiologically acceptable solution. It has a relatively long intravascular residence time and transports oxygen to the tissue effectively for at least 6 hours.

Does Oxygen Supply Improve Graft Viability in Liver Preservation

While the clinical results of orthotopic liver transplantation have greatly improved, the viability of liver grafts and extension of the safe time for preservation are necessary factors in need of improvement. The liver is one of the organs most sensitive to anoxia. The addition of an oxygen carrying agent to the preservation solution was evaluated. Pyridoxalated hemoglobin-polyoxyethylene conjugate (PHP) is used as an oxygen carrier. Viaspan (UW) served as a control solution. Test solution (PHP+UW) composition was composed of a 1:1 mixture of PHP and UW solutions with hemoglobin 4.0g%, hydroxyethyl starch 2.5g%, osmolality 320 mOsm/kg H2O, and colloidal osmotic pressure 33 mmHg. The oxygen carrying capacity of PHP+UW solution is about 10 times higher than UW solution at 4 degrees C. Male Lewis rats (BW: 250-300 g) were divided into five groups. After flushing the solution via the portal vein, rat livers were harvested. Two preservation methods, simple storage and perfusion (0.1 ml/min/g liver), were studied at 4 degrees C for 24 or 48 hours. OxyHb, MetHb, pO2, pH, Na, K, GOT, and GPT of perfusate, hepatic mitochondrial functions after preservation, and tissue adenine nucleotides by HPLC were measured. Light microscopy on the tissue was also performed. No significant differences were noted in perfusate biochemical parameters. Oxygen consumption during the perfusion was significantly higher in the PHP+UW than in the UW group. Hepatic mitochondrial functions and tissue ATP levels were better preserved in perfusion than in simple storage, and in PHP+UW than in UW at 48 hours. The oxygen carrying agent, PHP, can provide significantly higher levels of oxygen to liver grafts and improve graft viability.

Removal and recovery of cholesterol in thermofiltration.

Thermofiltration, a system of membrane plasmapheresis for LDL apheresis, was applied to the treatment of hypercholesterolemic patients to assess its lipid lowering potential, clinical feasibility and post-treatment lipid recovery. Plasma separated by a membrane separator was warmed above physiologic temperature, filtered with a plasma filter and returned to the patient on-line without requiring supplemental plasma product infusion. One calculated plasma volume was treated. Treatment schedules were weekly, biweekly or monthly. Patients treated by thermofiltration in this study were diagnosed as type II hypercholesterolemia. Reductions and sievings of high density lipoprotein (HDL) cholesterol and low density lipoprotein (LDL) cholesterol were evaluated. In addition, post-treatment solute recovery was assessed. The reduction ratios of HDL cholesterol and LDL cholesterol were 0.31 ± 0.08 and 0.58 ± 0.08, respectively (mean ± S.D. of 7 patients). Sieving coefficients of the plasma filter for HDL cholesterol and LDL cholesterol were 0.62 ± 0.12 and 0.03 ± 0.02, respectively (mean ± S.D. of 32 treatments). Cholesterol reduction fitted well to a single pool model. HDL cholesterol recovered significantly faster than LDL cholesterol and LDL cholesterol recovery differed among individuals. For some patients total cholesterol and LDL cholesterol levels were lowered by the biweekly treatment while for others the weekly treatment was required. Significant removal of LDL cholesterol with sparing of HDL cholesterol was achieved without the requirement for plasma products.