Effects of hydroxyethyl starch, gelatin and dextran on endothelium-derived relaxation in porcine coronary arteries.

BACKGROUND: In a pilot study we could show that hydroxyethyl starch (HES) induced a significant reduction of endothelium-dependent relaxation (EDR) and the endothelium-derived hyperpolarizing factor (EDHF). In this follow-up study we investigated whether this effect of HES was dose-dependent and whether it could be replicated with other colloids like dextran (DX) and gelatin (GL). METHODS: Rings of fresh porcine coronary arteries were consecutively tested with or without HES, DX or GL (5, 10, or 20 mg/ml). Indomethacin was added in all measurements to eliminate prostacyclin effects. Prostaglandin F2α was used for contraction and bradykinin (BK, 10⁻¹° to 10⁻5 M) for inducing EDR. After blocking nitric oxide (NO) by N-nitro-L-arginine (L-NNA), the experiments were repeated to assess the EDHF-mediated relaxation response to BK. RESULTS: HES induced a reduction in EDR for the BK concentrations of 10⁻8 and 10⁻7 M (n = 10; p < 0.05). After NO blockage with L-NNA, the relaxation response was reduced especially for the BK concentrations of 10⁻6 and 10⁻5 M (p < 0.05). GL showed a reduction in EDR with or without NO blockage with L-NNA especially for the BK concentrations of 10⁻6 and 10⁻5 M (n = 14; p < 0.05). DX induced a significant reduction in EDR for the BK concentrations of 10⁻7 and 10⁻6 M (n = 12; p < 0.05). After NO blockage with L-NNA, the relaxation response was reduced especially for the BK concentrations of 10⁻6 and 10⁻5 M (p < 0.05). CONCLUSION: For clinically relevant concentrations of HES, DX and GL a significant reduction in both NO-induced and NO-/prostacyclin-independent EDR can be found in epicardial coronary arteries of the pig.

Hydroxyethyl starch inhibits endothelium-derived relaxation in porcine coronary arteries.

OBJECTIVE: Hydroxyethyl starch (HES) solutions are widely used for fluid resuscitation. We studied the effects of HES on endothelium-dependent relaxation (EDR), especially on the endothelium-derived hyperpolarizing factor (EDHF). METHODS: Four-millimeter-long rings of fresh porcine coronary arteries from the local slaughterhouse were consecutively tested with or without HES (6 mg/ml). Indomethacin (10 micromol/l) was added in all measurements to eliminate prostacyclin effects. Prostaglandin F2alpha (10 micromol/l) was used for contraction and bradykinin (10(-10) to 10(-5) mol/l) for inducing EDR, which was calculated in percentage of the precontraction. After blocking all nitric oxide formation by N-nitro-L-arginine (300 micromol/l), the experiments were repeated to assess the EDHF-mediated relaxation response to bradykinin. RESULTS: HES 6 mg/ml induced a significant (p < 0.01) reduction in EDR (n = 8). After incubation with HES and nitric oxide blockage with N-nitro-L-arginine, the relaxation response was reduced especially for the bradykinin concentrations of 10(-6) mol/l (p < 0.05) and 10(-5) mol/l (p < 0.01). CONCLUSION: For the clinically relevant concentration of 6 mg/ml HES, a significant reduction in EDR and the EDHF can be found in epicardial coronary arteries of the pig.

Total recovery of heart grafts of non-heart-beating donors after 3 hours of hypothermic coronary oxygen persufflation preservation in an orthotopic pig transplantation model.

BACKGROUND: The coronary oxygen persufflation (COP) technique has been previously shown to allow prolonged heart preservation of 14 hr with optimal recovery in a pig model of orthotopic transplantation. This technique may be applicable to hearts grafted from non-heart-beating donors (NHBD). METHODS: Experiments were performed on pigs to test the effectiveness of oxygenated preservation, using COP for preservation of NHBD hearts. After 16 min of in situ normothermic ischemia, the hearts were flushed with histidine-tryptophan-ketoglutarate (HTK) solution or modified HTK solution (mBHTK) including 30 mmol/L 2,3-butanedione monoxime, 40 mg/L hyaluronidase,15 micromol/L adenosine, and 50 micromol/L calcium. Hearts were stored in the flush solutions for 3.3 hr or additionally persufflated with gaseous oxygen through the coronary arteries (COP) and transplanted orthotopically. RESULTS: Simple storage in HTK did not allow recovery of these hearts, whereas mBHTK storage resulted in improved function with 1.1 L/min cardiac output. The cardiac output reached 2.8 L/min (68% of normal values) with a left ventricular developed pressure of 101 mm Hg only after mBHTK+COP. Then the hearts were able to guarantee the circulation of the recipient for the test period after weaning from the heart-lung machine. CONCLUSIONS: Even in an NHBD with more than 15 min of in situ ischemia, the use of COP in combination with mBHTK solution for 3.3-hr storage of the heart allows excellent recovery of transplanted hearts and normal weaning from the heart-lung machine. This indicates that COP combined with mBHTK may be an optimal preservation technique for use with NHBD hearts.

pH-stabilization of predegraded PDLLA by an admixture of water-soluble sodiumhydrogenphosphate--results of an in vitro- and in vivo-study.

Aim of the study was to examine if the addition of buffering sodiumhydrogenphosphate to poly(D,L)lactide(PDLLA) would stabilize the pH-value in the in vivo environment of implanted material and whether this improves its biocompatibility. The material was predegraded just to the point of viscous disintegration to test the PDLLA in the moment of its most aggressive effect on the surrounding tissue. Racemic amorphous PDLLA was injection-molded with or without the admixture of 1 mol NaP per 100 mol lactate, the degradation product of PDLLA (=1 mol%) to form 20mm x 3 mm x 2mm rods. Predegradation was performed by storing the rods at 55 degrees C for 14 days, just to the point of beginning dissolution. Predegraded PDLLA or PDLLA + NaP samples were used for in vitro incubation tests, as well as for the in vivo study, where the rods were implanted into the spinal muscles of 30 male Wistar rats. Repeatedly, measurements of the pH-value were made in the incubation solutions in vitro. The surrounding tissue of the implanted samples as well as the normal contralateral muscle tissue was checked for its pH-value in a group of 3 rats, respectively, anaesthesized at various time intervals after implantation. After these measurements the implants and their surrounding tissues were excised for histological examination. In Ringer's solution pH-values dropped immediately within the first week of incubation of both predegraded materials reaching -4 pH units after 4 weeks in the PDLLA containing medium, after 6 weeks in the PDLLA + NaP containing medium. Soerensen buffer slowed the pH decrease with significant differences between the material groups up to the 28th week. In vivo, the pH of the surrounding tissue was influenced by the implanted PDLLA material up to the 4th week, while the admixture of NaP resulted in a significant pH stabilization. A higher quantity of macrophages and giant cells were seen between the 2nd and 6th week after the implantation in the environment of pure PDLLA compared with PDLLA + NaP. Complete resorption of predegraded pure PDLLA or PDLLA + NaP from the extracellular space was reached 28 weeks postimplantation in vivo. Thus, sodiumhydrogenphosphate improves the biocompatibility of degrading PDLLA at the point of viscous disintegration by stabilizing the pH-value in the environment of the implants for several weeks and reducing adverse tissue reactions.