Evaluation of a poly(vinyl pyrollidone)-coated biomaterial for urological use

The associated problems of bacterial biofilm formation and encrustation that may cause obstruction or blockage of urethral catheters and ureteral stents often hinders the effective use of biomaterials within the urinary tract. In this in vitro study, we have investigated the surface properties of a hydrophilic poly(vinyl pyrollidone) (PVP)-coating applied to polyurethane and determined its suitability for use as a urinary tract biomaterial by comparing its lubricity and ability to resist bacterial adherence and encrustation with that of uncoated polyurethane and silicone. The PVP-coated polyurethane was significantly more hydrophilic and more lubricious than either uncoated polyurethane or silicone. Adherence of a hydrophilic Escherichia coli isolate to PVP-coated polyurethane and uncoated polyurethane was similar but significantly less than adherence to silicone. Adherence of a hydrophobic Enterococcus faecalis isolate to PVP-coated polyurethane and silicone was similar but was significantly less than adherence to uncoated polyurethane. Struvite encrustation was similar on the PVP-coated polyurethane and silicone but significantly less than on uncoated polyurethane. Furthermore, hydroxyapatite encrustation was significantly less on the PVP-coated polyurethane than on either uncoated polyurethane or silicone. The results suggest that the PVP-coating could be useful in preventing complications caused by bacterial biofilm formation and the deposition of encrustation on biomaterials implanted in the urinary tract and, therefore, warrants further evaluation.

Ischemia triggered by red blood cell products in the subarachnoid space is inhibited by nimodipine administration or moderate volume expansion/hemodilution in rats

OBJECTIVE

It has been proposed that delayed ischemic neurological deficits are induced by red blood cell (RBC) products after subarachnoid hemorrhage. Prophylactic treatment with the Ca2+ antagonist nimodipine or prevention of systemic volume contraction reduces the occurrence of delayed ischemic neurological deficits. To gain insight into the underlying mechanism, we studied the effects of nimodipine or volume expansion on ischemic events induced by RBC products in rats.

METHODS

A cranial window was implanted in 52 rats. At the window, cerebral blood flow (measured with laser Doppler flowmetry) and the subarachnoid direct current potential were recorded; the cortical surface was superfused with artificial cerebrospinal fluid. A spreading neuronal/astroglial depolarization wave was triggered at a remote site, from which it traveled to the cranial window.

RESULTS

In 16 rats, the depolarization wave triggered an ischemic event at the cranial window when artificial cerebrospinal fluid containing the RBC product hemoglobin and elevated K+ levels was superfused. In contrast, in animals receiving intravenously administered nimodipine (n = 12) or moderate volume expansion/hemodilution with hydroxyethyl starch (6% hydroxyethyl starch 200/0.5) (n = 10), the depolarization wave triggered brief initial hypoperfusion, followed by brief hyperemia, in the cortical area exposed to the RBC products. Under physiological conditions, the depolarization wave triggered brief hyperemia (n = 14).

CONCLUSION

Spreading ischemia induced by RBC products is antagonized by measures known to be beneficial in the prophylaxis of delayed ischemic neurological deficits. Our findings suggest that a mechanism involving the cortical microcirculation might underlie the therapeutic effects of nimodipine and volume expansion.

The in vitro effects of crystalloids and colloids on coagulation

Classically haemodilution is regarded as causing coagulopathy. However, haemodilution with saline seems to cause a hypercoagulable state both in vivo and in vitro. The aim of the present study was to measure the effect of mild to severe haemodilution using thrombelastography. Blood samples were taken in 12 healthy volunteers and divided into seven aliquots. One aliquot was undiluted and acted as control. The other six were diluted with normal saline, Ringer Acetate, 4% albumin, Dextran 70, 6% and 10% hydroxyethylstarch to 10%, 20%, 40%, 50% and 60% dilution. The dilution was checked by measuring the haemoglobin concentration. Each aliquot was placed in a temperature-controlled thrombelastography channel. Increased coagulation activity, as measured by thrombelastography changes, was detected at low and medium levels of dilution with all the tested solutions. At more than 40% dilution, coagulation returned to normal while in the case of dextran and hydroxyethylstarch coagulopathy developed. For crystalloids and albumin,dilution had to exceed 50% before coagulation was impaired. If these findings can be reproduced in vivo, they may have implications for transfusion practice and prophylaxis against thrombosis.

Effects of a new modified, balanced hydroxyethyl starch preparation (Hextend) on measures of coagulation

BACKGROUND

Hydroxyethyl starch (HES) may affect blood coagulation. We studied the effects of a modified, balanced, high-molecular weight [mean molecular weight (MW) 550 kDa], high-substituted [degree of substitution (DS) 0.7] HES preparation (Hextend) on coagulation in patients undergoing major abdominal surgery.

METHODS

Patients were allocated randomly to receive Hextend) (n=21), lactated Ringer's solution (RL, n=21) or 6% HES with a low MW (130 kDa) and a low DS (0.4) (n=21). The infusion was started after induction of anaesthesia and continued until the second postoperative day to maintain central venous pressure between 8 and 12 mm Hg. Activated thrombelastography (TEG) was used to assess coagulation. Different activators were used (extrinsic and intrinsic activation of TEG) and aprotinin was added to assess hyperfibrinolytic activity (ApTEG). We measured onset of coagulation [coagulation time (CT=reaction time, r)], the kinetics of clot formation [clot formation time (CFT=coagulation time, k)] and maximum clot firmness (MCF=maximal amplitude, MA). Measurements were performed after induction of anaesthesia, at the end of surgery, 5 h after surgery and on the mornings of the first and second days after surgery.

RESULTS

Significantly more HES 130/0.4 [2590 (SD 260) ml] than Hextend) [1970 (310) ml] was given. Blood loss was greatest in the Hextend) group and did not differ between RL- and HES 130/0.4-treated patients. Baseline TEG data were similar and within the normal range. CT and CFT were greater in the Hextend) group immediately after surgery, 5 h after surgery and on the first day than in the two other groups. ApTEG MCF also changed significantly in the Hextend) patients, indicating more pronounced fibrinolysis. Volume replacement using RL caused moderate hypercoagulability, shown by a decrease in CT.

CONCLUSION

A modified, balanced high-molecular weight HES with a high degree of substitution (Hextend) adversely affected measures of coagulation in patients undergoing major abdominal surgery, whereas a preparation with a low MW and low DS affected these measures of haemostasis less. Large amounts of RL decreased the coagulation time.

[Acute hemorrhage. View on the problem]

Acute hemorrhage is a main cause of reduction of blood oxygen capacity. The main aim of correction of sequels of acute hemorrhage is to maintain effective gas exchange by restoring central circulation and microcirculation, the rate of diuresis, by normalizing water-salt exchange, to eliminate anemia, hypoproteinemia, and acute blood coagulability disorders. The values of oxygen budget with calculated oxygen delivery and consumption and those of hemoglobin and hematocrit which are of great value only after recovery of circulating blood volume are considered to be major indications for hemotransfusion. A relationship is established between the extraction and uptake of oxygen and its delivery. The concept of the critical level of oxygen delivery is considered, ways of correcting oxygen indebtedness are presented. Alternatives to the use of hemotransfusions by employing the solutions of modified hemoglobulin and perfluorocarbon-containing emulsions are under consideration. A possible algorithm of aid rendering in acute hemorrhage is given.

Prevention of adhesions with crystalloids during laparoscopic surgery in mice

STUDY OBJECTIVE

To evaluate the effect of saline and Ringer's lactate solutions in preventing adhesions during laparoscopic surgery in mice.

DESIGN

Prospective, randomized trial (Canadian Task Force classification I).

SETTING

Academic research center.

SUBJECTS

Ninety-two female Naval Medical Research Institute mice.

INTERVENTION

Adhesions were induced laparoscopically by opposing bipolar lesions in the uterine horns and pelvic sidewalls, and saline or Ringer's lactate solution was added at different times during the procedure.

MEASUREMENTS AND MAIN RESULTS

Adhesions were scored quantitatively and qualitatively for extent, type, and tenacity after 7 days under microscopic vision during laparotomy. After 45 minutes of pneumoperitoneum, neither solution reduced adhesion formation, but when added immediately after surgery they did (p = 0.002). Coagulation was not significantly different with addition of either solution immediately after coagulation. In the third experiment the presence of fluid during pneumoperitoneum decreased adhesion formation (p = 0.0001) but Ringer's lactate was more effective than saline (p = 0.0005).

CONCLUSION

Crystalloids reduced CO(2) pneumoperitoneum-enhanced adhesion formation in a laparoscopic mouse model, but Ringer's lactate solution was more effective than saline.

Changes in myofibrillar structure and function produced by N-terminal deletion of the regulatory light chain in Drosophila

The similarity of amino acid sequence and motifs of the N-terminal extensions of certain class II myosin light chains, found throughout the animal kingdom, suggest a common functional role. One possible role of the N-terminal extension is to enhance oscillatory work and power production in striated muscles that normally operate in an oscillatory mode. We conducted small-angle X-ray diffraction experiments and small-length-perturbation analysis to examine the structural and functional consequences of deleting the N-terminal extension of the myosin regulatory light chain (RLC) in Drosophila flight muscle. The in vivo lattice spacing of dorsal longitudinal muscle (DLM) of flies lacking the RLC N-terminal extension (Dmlc2delta2-46) was approximately 1 nm less than that of wild type (48.56 +/- 0.02 nm). The myofilament lattice of detergent-treated, demembranated DLM swelled, with the DmlcdeltaA2-46 lattice expanding more than wild type and requiring roughly twice the concentration of Dextran T500 to restore its lattice to in vivo spacing (9-10% vs. 4% w/v). The calcium sensitivity and maximum amplitude of net oscillatory work near the in vivo lattice spacing was significantly lower in Dmlc2delta2-46 compared to wild type (pCa50 shifted by approximately one-third of a pCa unit; amplitude reduced by approximately one-half). These changes were in contrast to the lack of effect reported in a previous study carried out in the absence of Dextran T500. The results are consistent with the N-terminal extension interacting with actin to increase the probability that crossbridges form during stretch-activated oscillatory work and power production, especially at submaximal levels of calcium activation.

Hemodilution with albumin, but not Hextend, results in hypercoagulability as assessed by Thrombelastography in rabbits: role of heparin-dependent serpins and factor VIII complex

Isovolemic hemodilution (IVHD) has been advocated as an effective method of reducing the need for transfusion but has been associated with hypercoagulability. We tested the hypothesis that IVHD enhances hemostatic function by decreasing circulating antithrombin activity in rabbits. Furthermore, it was determined whether different replacement solutions would affect hemostasis. Sedated rabbits were randomly assigned to groups that underwent IVHD (40% blood volume removed) with 5% human albumin (n = 10) or a 6% hetastarch solution (Hextend). Antithrombin and Factor VIII complex (VIII:C) activities were determined, and thrombelastography(R) was performed with or without platelet inhibition. IVHD resulted in a significant (P < 0.05) decrease in antithrombin (32%-39%) without fluid-specific differences observed. VIII:C did not change in the albumin group, whereas the hetastarch group had a significant (P < 0.05) decrease (43%) in VIII:C that was also significantly (P < 0.05) less than the albumin group. The time to clot initiation was decreased, and the rate of clot formation increased significantly via thrombelastography(R) in albumin animals. No significant change in clot kinetics was observed in hetastarch animals. In rabbits, the primary determinant of hemostasis after IVHD was the interaction of changes in antithrombin activity and VIII:C. These data serve as a rational basis to determine whether IVHD-mediated hypercoagulability encountered clinically may be attenuated or exacerbated by the choice of colloid administered.

IMPLICATIONS

Isovolemic hemodilution (IVHD) is associated with hypercoagulability. Rabbits hemodiluted with albumin, but not Hextend, became hypercoagulable secondary to a loss of antithrombin activity with simultaneous maintenance of Factor VIII complex activity (VIII:C). Hextend-treated animals had proportionate decreases in both antithrombin activity and VIII:C. IVHD-mediated hypercoagulability encountered clinically may be attenuated or exacerbated by the choice of colloid administered.

Coagulation effects of in vitro serial haemodilution with a balanced electrolyte hetastarch solution compared with a saline-based hetastarch solution and lactated Ringer's solution

The hydroxyethyl starches are a group of compounds that has been associated with impairment of coagulation when large volumes are administered. The thrombelastograph is commonly used to assess point-of-care whole blood coagulation. Little is known about the dose-response relationships of haemodilution, and it is reasonable to assume that a linear association exists. This may not be the case with altered electrolyte compositions of the fluids used for haemodilution. We have therefore conducted an in vitro study of haemodilution of human whole blood using lactated Ringer's solution and two high molecular weight hetastarches, one in a balanced salt solution, the other in a 0.9% saline solution. The thrombelastograph, commonly used for the assessment of the coagulation effects of synthetic colloids, was used as the coagulation assessment device. Serial haemodilution with hetastarch in a balanced salt solution demonstrated a biphasic response (of r-times and k-times, as well as alpha angles), with haemodilution in the 20-40% range causing enhanced coagulation, and higher degrees of dilution causing a decrease in overall coagulation performance. A similar picture was observed with lactated Ringer's solution, but only significantly so in alpha angles. Hetastarch in saline did not display this initial increased coagulability at mild to moderate dilutions. This biphasic response of lactated Ringer's solution and hetastarch in a balanced salt solution reflects the complex interaction of fluids and the coagulation system, and that these effects cannot be attributed to simple haemodilution. On the other hand, there was a linear decrease in maximum amplitude with haemodilution. Maximum amplitude was particularly affected by both starches, which is an expected finding in view of the known interaction between the hydroxyethyl starches and von Willebrand's factor.

Hypovolemia is a main factor behind disturbed perfusion and metabolism in the intestine during endotoxemia in cat

Disturbances in intestinal metabolism and perfusion during SIRS can be direct effects of toxic substances, and/or effects secondary to hypovolemia. An attempt to evaluate the significance of hypovolemia for intestinal disturbances during SIRS was made in the present study on feline by evaluating the degree to which the intestinal alterations following endotoxin infusion were restored by a clinically relevant volume infusion. The results were compared with control animals treated identically except that they were not given a volume infusion. We analyzed effects of a colloid infusion during endotoxemia on intestinal perfusion, and on the metabolites lactate, pyruvate, glucose, and glycerol in the intestinal wall, the latter by a microdialysis technique. Arterial and central venous blood pressures, and superior mesenteric artery blood flow were measured, and intestinal oxygen delivery and uptake were calculated. To evaluate to what extent a restoring effect of a colloid infusion was dependent on the type of colloid solution used, three different colloids with about the same volume expanding effects (6% albumin, 6% dextran 70 and 6% hydroxyethyl starch, n = 3 x 6) were tested randomly and blinded. Four hrs after start of endotoxin (1 mg/kg + 1 mg/kg/h), the colloid was infused at a rate of 5 mL/kg for 30 min followed by 2.5 mL/kg/h. Endotoxin caused a marked deterioration of perfusion and metabolic parameters. Most of these parameters turned towards normalization, though not fully reaching baseline values within 4 hrs after start of the colloid infusion. In the control experiments (n = 4), the endotoxin-induced deteriorations persisted or were aggravated during the corresponding time period. The results indicated that hypovolemia is an essential factor but not the only one behind alterations in metabolism and perfusion in the intestine during SIRS, and the alterations can be significantly reduced by adequate volume substitution. In this respect no differences could be seen between the three colloids tested.

The effects of hydroxyethyl starches on intracellular calcium in platelets

Hydroxyethyl starch (HES) solutions impair platelet function. To determine whether this effect is achieved through interference of HES with intracellular activation processes, in which calcium is the key second messenger, we evaluated the agonist-induced increase of the cytoplasmic calcium concentration in the presence of HES of different molecular weights. Aliquots of citrated whole blood of 12 volunteers were incubated in vitr. with saline, HES 450 (molecular weight in kilodalton), HES 130, and HES 70, resulting in 20% hemodilution. An undiluted sample served as control. The samples were stained with Fluo-3 as the calcium-sensitive fluorescent probe with subsequent flow cytometric analysis. After determination of a baseline, platelets were activated with thrombin receptor activator peptide 6. Platelet activation with thrombin receptor activator peptide 6 resulted in a fast increase in fluorescence (approximately eightfold), representing intracellular calcium mobilization. None of the tested HES solutions exerted a statistically significant effect on the cytoplasmic calcium concentration compared with samples that were incubated with saline or that remained undiluted. These results indicate that the known inhibiting effect of HES on platelets is not achieved through interference with intracellular activation processes.

IMPLICATIONS

Hydroxyethyl starch does not exert its known inhibitory effect on platelet function by interfering with intracellular activation processes.

Salmon cardiac natriuretic peptide is a volume-regulating hormone

The present study tested the hypothesis that salmon cardiac peptide (sCP), a new member of the family of natriuretic peptides, has an important role in the regulation of fluid balance and cardiovascular function. Intra-arterial administration of sCP increased urine output in salmon. It had a diuretic effect in rat as well, but the potency was lower. sCP increased the sodium excretion in proportion to the increased urine flow. Blood pressure was not affected by sCP in either species. Acute volume expansion elevated the plasma level of sCP in salmon, and an acute transfer of salmon from fresh to sea water decreased the circulating sCP level. Cardiac immunoreactive sCP or sCP mRNA levels were not affected by transfer to sea water. These results indicate that sCP has an important physiological role in defending salmon against volume overload but that it does not appear to contribute to the short-term regulation of blood pressure. sCP provides an excellent model of the general mechanisms of regulation of the A-type (atrial) natriuretic peptide system.

Effects on coagulation of intravenous crystalloid or colloid in patients undergoing peripheral vascular surgery

BACKGROUND

This study investigated whether haemodilution-enhanced coagulation can be demonstrated under regional anaesthesia, whether this occurs before surgery, and whether the fluid used influences the effect.

METHODS

Patients were randomly allocated to receive either crystalloid or colloid intravenous fluid. An epidural was administered. Samples of venous blood were taken before fluid administration, after completion of the epidural and initial fluid load, during surgery before heparin, and after 24 h. Thrombelastograph analysis was performed, and full blood count, international normalised ratio, activated partial thromboplastin time, D-dimers and thrombin-antithrombin complex were measured.

RESULTS

In the crystalloid group, enhanced coagulation compared with baseline was demonstrated after initial fluid load (mean (SD) r-time 10.1 (4.9) min; P < 0.033; k-time 3.5 (1.7) min; P < 0.01; alpha-angle 54.9 (13.9) degrees; P < 0.01) and before heparin administration (r-time 8.8 (3.9) min; P < 0.01; alpha-angle 54.9 (12.6) degrees; P < 0.02). There was no enhancement of coagulation in the colloid group. There were no changes from baseline after 24 h.

CONCLUSIONS

This study confirms that the enhanced perioperative coagulation mechanism is related to dilution, rather than surgery, and is triggered by rapid crystalloid haemodilution. Consideration should be given to the use of colloid rather than crystalloid solutions for rapid fluid loading in vasculopathic patients undergoing surgery.

The role of intravenous volume expansion in moderate pre-eclampsia

We examined the hemodynamic and hemorheological effects of intravenous volume expansion in women with pre-eclampsia. 20 untreated women with moderate pre-eclampsia were randomized to receive a 500 ml infusion over 4 h of either hydroxyethylstarch (HAES steril 10%, HES) or NaCl 0.9% solution. After completion of the infusion trial all patients received oral antihypertensive drugs, bed rest and free sodium and water intake. The hemodynamic responses were measured by impedance cardiography. Hemorheological parameters and blood pressure were measured before and after (24 h later) infusion. The HES infusion but not NaCl leads to a significant reduction of hematocrit and erythrocyte aggregation. In addition to that there was a nonsignificant increase of the cardiac index in the HES-group but no changes in the heart rate. Intravenous volume expansion in women with pre-eclampsia with a long acting colloid like hydroxyethylstarch is associated with a significant influence on the flow properties (hematocrit and erythrocyte aggregation) of blood.

Fos immunoreactivity in the diagonal band and the perinuclear zone of the supraoptic nucleus after hypertension and hypervolaemia in unanaesthetized rats

We used Fos immunocytochemistry to study the effects of hypertension and hypervolaemia on neurones in the diagonal band of Broca and the perinuclear zone of the supraoptic nucleus, two nuclei that are both involved in the baroreceptor regulation of vasopressin neurones in the supraoptic nucleus. In addition, we used sino-aortic denervation to examine the role of arterial baroreceptors in the response to these haemodynamic changes. Sham-operated and sino-aortic denervated rats were infused with phenylephrine sufficient to increase blood pressure for 2 h. Control rats were infused with the same volume of isontonic saline. Only Sham sino-aortic denervated rats showed reflex bradycardia in response to the increased blood pressure. Volume expansion was produced by infusing the rats with isotonic saline equal to 10% of their body weight for 10 min, which significantly increased central venous pressure. In the diagonal band of Broca and the perinuclear zone, the number of Fos-positive neurones was significantly increased after phenylephrine infusion. Sino-aortic denervation blocked the significant increase in both regions. After volume expansion, a significant increase in Fos staining was observed only in the perinuclear zone of the supraoptic nucleus. This increase was not blocked by sino-aortic denervation. Our results indicate that both the diagonal band of Broca and the perinuclear zone of the supraoptic nucleus are activated by stimulating arterial baroreceptors; however, the perinuclear zone of the supraoptic nucleus is stimulated during volume expansion. Furthermore, the activation of perinuclear zone of the supraoptic nucleus after volume expansion is not dependent on intact arterial baroreceptors.

Renal responses to plasma volume expansion and hyperosmolality in fasting seal pups

Renal responses were quantified in northern elephant seal (Mirounga angustirostris) pups during their postweaning fast to examine their excretory capabilities. Pups were infused with either isotonic (0.9%; n = 8; Iso) or hypertonic (16.7%; n = 7; Hyper) saline via an indwelling catheter such that each pup received 3 mmol NaCl/kg. Diuresis after the infusions was similar in magnitude between the two treatments. Osmotic clearance increased by 37% in Iso and 252% in Hyper. Free water clearance was reduced 3.4-fold in Hyper but was not significantly altered in Iso. Glomerular filtration rate increased 71% in the 24-h period after Hyper, but no net change occurred during the same time after Iso. Natriuresis increased 3.6-fold in Iso and 5.3-fold in Hyper. Iso decreased plasma arginine vasopressin (AVP) and cortisol acutely, whereas Hyper increased plasma and excreted AVP and cortisol. Iso was accompanied by the retention of water and electrolytes, whereas the Hyper load was excreted within 24 h. Natriuresis is attributed to increased filtration and is independent of an increase in atrial natriuretic peptide and decreases in ANG II and aldosterone. Fasting pups appear to have well-developed kidneys capable of both extreme conservation and excretion of Na(+).

Biodistribution, blood half-life, and receptor binding of a somatostatin-dextran conjugate

Derivatives of somatostatin (sms) are attracting increasing interest as part of the treatment of several cancer diseases expressing sms receptors (srs). Radiolabeled sms analogs can additionally be used for systemic radiotherapy and for diagnostic investigations. Glycosylated sms-14 (sms-dextran70) was characterized regarding in vitro srs binding, biodistribution, and blood half-life in mice. Rat brain cortex membranes (expressing srs 2) were used for the srs binding study. Tyr3-Octreotide was used as positive control. The binding data were analyzed by competition curve analysis. In the biodistribution study, the Bolton-Hunter reagent was used for the radioiodination of sms-dextran70. Organs and blood were collected at different time-points and the percentage of the injected dose per gram of tissue (%ID/g) was calculated. The conjugate was administered subcutaneously (sc). The sms-dextran70 showed high srs binding affinity (i.e., in the same nanomolar range as the reference ligand Tyr3-octreotide (IC50 approximately 2.5 nM). The blood half-life was approx 27 h after reaching maximum blood concentration 24 h postinjection. Because of the molecular weight of the conjugate (i.e., approx 75,000) being above the kidney threshold for dextran (i.e., 50,000), the digestion and excretion is assumed to be mainly through the hepatobiliary system. Increased uptake was seen in the adrenals, which are receptor-positive organs. Some accumulation was seen in the stomach, indicating certain deiodination of the conjugate label. The sms-dextran70 showed promising properties and its clinical relevance is currently being evaluated in clinical phase I-II studies.

Fluid resuscitation and hyperchloremic acidosis in experimental sepsis: improved short-term survival and acid-base balance with Hextend compared with saline

OBJECTIVE

To compare resuscitation with 0.9% saline with Hextend, a synthetic colloid in a balanced electrolyte solution, in terms of acid-base status and survival time in an experimental model of septic shock in the rat.

DESIGN

Randomized, open-label, controlled experiment.

SETTING

University research laboratory.

SUBJECTS

Sixty adult, male Sprague-Dawley rats.

INTERVENTION

Animals were studied for 12 hrs after intravenous infusion of Escherichia coli endotoxin (20 mg/kg). Animals were volume resuscitated to maintain a mean arterial pressure >60 mm Hg using either 0.9% saline (n = 25), Hextend (n = 25), or lactated Ringer's (n = 10).

MEASUREMENTS

Arterial blood gases and electrolytes were measured before and after resuscitation (0, 180, 360, and 540 mins after endotoxin infusion). Survival time was measured, up to 12 hrs.

RESULTS

Mean survival time among animals treated with saline or Ringer's was 45% less compared with Hextend-treated animals: 391 +/- 151 mins and 362 +/- 94 mins vs. 567 +/- 140 mins, respectively, p <.0001. Overall survival (at 12 hrs) was 0% with saline or Ringer's vs. 20% with Hextend, p =.05. After resuscitation with saline, arterial standard base excess and plasma apparent strong ion difference were both significantly lower (-19.3 +/- 5.2 vs. -12.1 +/- 5.7, p <.001, and 23.0 +/- 6.2 vs. 30.3 +/- 2.9, p <.0001, respectively) and plasma Cl(-) was significantly higher (123 +/- 7 vs. 115 +/- 3 mmol/L, p <.0001) compared with Hextend. Resuscitation with Ringer's solution resulted in a standard base excess, and Cl(-) between that of saline and Hextend (-15.4 +/- 3.1, and 117 +/- 3, respectively).

CONCLUSION

Compared with 0.9% saline, volume resuscitation with Hextend was associated with less metabolic acidosis and longer survival in this experimental animal model of septic shock.

Effect of medium tonicity and dextran on neutrophil function in vitro

BACKGROUND

Multiple investigations have demonstrated that hypertonic saline (HS) diminishes the response of polymorphonuclear leukocytes (PMNs) to stimulation. Recent meta-analysis suggests that hypertonic saline in dextran (HSD) is clinically superior to HS. No work to date has examined the effect of added dextran on this immunomodulatory property.

METHODS

Human PMNs were exposed to media of varying osmolarity (220-360 mOsm/L) and stimulated with f-met-leu-phe with or without dextran present in the medium. Cell volume, respiratory burst, PMN aggregation, and beta(2)-integrin (CD18) expression were measured.

RESULTS

Stimulation with f-met-leu-phe increased cell volume, respiratory burst, aggregation, and CD18 expression. The increases in cell volume, respiratory burst, and aggregation were significantly attenuated by exposure to hypertonic medium. The addition of dextran to the media did not change the results.

CONCLUSION

The alterations in PMN function associated with HS are not changed or attenuated by the addition of dextran, suggesting that the clinically superior HSD may have effects similar to HS in mitigating the tissue damage associated with activated PMNs.

Albumin extravasation and tissue washout of hyaluronan after plasma volume expansion with crystalloid or hypooncotic colloid solutions

BACKGROUND

Intravascular volume expansion is followed by loss of fluid from the circulation. The extravasation of albumin in this readjustment is insufficiently known.

METHODS

Twelve male volunteers participated, each in three separate sessions, in a controlled, randomised, open fashion. They received one of the following: albumin 40 g/L,(7.1 mL/kg, i.e. 500 mL per 70 kg); Ringer's acetate (21.4 mL/kg), or dextran 30 g/L (7.1 mL/kg). The fluids were infused during 30 min and the subjects were followed for 180 min. ECG, arterial oxygen saturation and non-invasive arterial pressure were recorded. Haemoglobin, haematocrit, serum albumin and osmolality, plasma colloid osmotic pressure and hyaluronan concentration were determined in venous samples.

RESULTS

The serum albumin concentration decreased (P < 0.05, anova) following Ringer's acetate or dextran, whereas serum osmolality was unchanged in all groups. The colloid osmotic pressure decreased (P < 0.05) after the Ringer solution. The blood volume increase was estimated from the decrease in haemoglobin concentration and did not differ between the three fluids. The cumulated extravasation of albumin was largest following albumin (10.4 +/- 5.4 g, mean +/- SD), less following dextran (5.6 +/- 5.0 g) and negligible in the Ringer group (0.5 +/- 10.0 g; P < 0.05 against albumin). However, the Ringer solution increased the plasma concentration of hyaluronan drastically.

CONCLUSIONS

Infusion of hypotonic colloidal solutions entails net loss of albumin from the vascular space. This is not the case after Ringer's acetate. Increased interstitial hydration from the latter fluid is followed by lymphatic wash out of hyaluronan.

Are lactated Ringer's solution and normal saline solution equal with regard to coagulation?

Crystalloids represent an attractive strategy to alleviate intravascular volume deficits. Crystalloid hemodilution was associated with hypercoagulability in in vitro and in vivo studies. The influence of different crystalloids on coagulation in the surgical patient is not well studied. In a prospective, randomized study in patients undergoing major abdominal surgery, we used either lactated Ringer's solution (RL) (n = 21) or 0.9% saline solution (SS) (n = 21) exclusively for intravascular volume replacement over 48 h to maintain central venous pressure between 8 and 12 mm Hg. Activated thrombelastography (TEG) using different activators (intrinsic TEG, extrinsic TEG, heparinase TEG, aprotinin TEG) was used to measure coagulation time, clot formation time, and maximum clot firmness. Measurements were performed after induction of anesthesia (T0), immediately after surgery (T1), 5 h after surgery (T2), and on the morning of the first (T3) and second (T4) postoperative days. RL 18,750 +/- 1890 mL and 17,990 +/- 1790 mL of SS were infused during the study period. Acidosis was seen only in the SS-treated group. Blood loss was not different between the groups. Fibrinogen and antithrombin III decreased similarly at T1 and T2 in both groups, most likely because of hemodilution. Differences in TEG data from normal baseline were seen only immediately after surgery and 5 h thereafter, indicating mild hypercoagulability in the intrinsic TEG (RL, from 147 +/- 130 s to 130 +/- 11 s; SS, from 146 +/- 12 s to 131 +/- 12 s). There were no differences in coagulation between RL- and SS-treated patients. We conclude that in major abdominal surgery intravascular volume replacement with crystalloids resulted in only moderate and abbreviated changes in coagulation. No differences in activated TEG and blood loss were seen between an RL- and an SS-based intravascular volume replacement regimen.

IMPLICATIONS

In 42 patients undergoing major abdominal surgery, either lactated Ringer's solution or 0.9% saline solution were exclusively used for volume therapy for 48 h. Activated thrombelastography revealed some mild hypercoagulability after surgery. No differences in coagulation were seen between the two intravascular volume replacement strategies.

A randomized, blinded trial comparing the hemostatic effects of pentastarch versus hetastarch

BACKGROUND

HES solutions provide a sterile, alternative colloidal fluid to albumin solutions and/or plasma in the management of patients who need plasma volume expansion. Solutions of HES are widely accepted internationally but are used only modestly in the United States, largely because of concerns over hemostasis.

STUDY DESIGN AND METHODS

A randomized, blinded, two-arm trial comparing the hemostatic effects of pentastarch versus hetastarch when infused in the clinically relevant dose of 90 g of HES dissolved in 1.5 L of saline was conducted. Multiple studies of fibrin clot formation, fibrinogen/fibrinolysis, and platelet (PLT) functions were performed before and on multiple occasions for 70 days following HES infusion.

RESULTS

Several significant abnormalities of hemostasis assay results occurred following HES infusions, with hetastarch causing significantly greater abnormalities than pentastarch. Individual clotting proteins and blood PLTs fell modestly because of plasma volume expansion and hemodilution. A fall in excess of that caused by hemodilution was demonstrated for von Willebrand factor antigen plus its associated FVIII and ristocetin cofactor activities. The partial thromboplastin time was prolonged, whereas the thrombin time was shortened. Plt function abnormalities were seen in most subjects to a modest degree. Studies of fibrinolysis were normal.

CONCLUSIONS

Solutions of hetastarch produce significant abnormalities of some hemostasis laboratory results when infused at clinically relevant doses, but it is unlikely that the modest hemostatic abnormalities produced at these doses per se would lead to clinical bleeding. Hetastarch causes greater hemostatic abnormalities than pentastarch, and because both HES solutions have comparable plasma volume-expanding effects, it is reasonable to prefer pentastarch as a plasma volume expander.

Effects of resuscitation with hydroxyethyl starch (HES) on pulmonary hemodynamics and lung lymph balance in hemorrhagic sheep; comparative study of low and high molecular HES

Synthetic starch solution, such as hydroxyethyl starch (HES), has been used clinically to restore cardiovascular volume in patients with hemorrhagic shock. Several HES solutions are available clinically, but each HES has a broad range of molecular mass fractions. We performed comparative studies of extremely low and high molecular HES to evaluate the effects of these HES solutions on lung lymph filtration during resuscitation. We prepared awake sheep with vascular monitoring and lung lymph fistulas. After baseline measurements, animals were bled from an arterial line to maintain shock. After 2 h of hemorrhagic period, the following three solutions were infused over 1 h, respectively. Experiment (Exp) 1 (n=6); low molecular HES; (molecular weight (MW) 70000, substitution fractions 0.5-0.55, Exp 2 (n=6); high molecular HES; (MW 450000, substitution fractions 0.65). Exp 3 (n=6); normal saline (NS). The quantity of solution was determined as the same volume of blood lost to induce hemorrhagic situation in each animal (Exp 1; 940+/-36 ml, Exp 2; 910+/-50 ml, Exp 3; 920+/-42 ml). Both low and high molecular HES could restore the systemic artery pressure and cardiac output, and significantly increased pulmonary microvascular pressure equally, which were significantly higher than those in normal saline. However, actual oncotic pressure gradient (plasma-lymph) rose transiently during low molecular HES infusion, while high molecular HES widened the oncotic pressure gradient even after the cessation of the infusion. Lung lymph flow during and after resuscitation with low molecular HES and NS rose significantly from the pre-shock baseline. There was no significant difference in increased lung lymph flow between low molecular HES and NS. However, lung lymph flow after high molecular HES was significantly less than that after low molecular HES. These data suggest that low molecular HES is as useful a plasma substitute as high molecular HES, but has a possibility to increase lung lymph filtration during the early phase of resuscitation.

Crystalloid strong ion difference determines metabolic acid-base change during in vitro hemodilution

OBJECTIVES

To determine the relationship between the strong ion difference (SID) of a diluting crystalloid and its metabolic acid-base effects on in vitro blood dilution.

DESIGN

Prospective in vitro study.

SETTING

University research laboratory.

SUBJECTS

Normal human blood.

INTERVENTIONS

Three solutions were prepared, each with [Na] 140 mmol/L. [Cl-] for solutions 1, 2, and 3 was 120, 110, and 100 mmol/L, respectively, the other anion being HCO3-. SID values were thus 20, 30, and 40 mEq/L, respectively. Serial dilutions of well-oxygenated fresh venous blood were performed anaerobically by using each of solutions 1-3 as well as 0.9% saline (SID = 0 mEq/L) and Hartmann's solution (SID = -4 mEq/L).

MEASUREMENTS AND MAIN RESULTS

Blood gas and electrolyte analyses were performed before and after each dilution. Apart from dilutions with solution 3 (crystalloid SID 40 mEq/L) during which plasma SID did not change, plasma SID decreased during hemodilution. In contrast, base excess increased during hemodilution with solutions 3 and 2 (crystalloid SID 40 mEq/L and 30 mEq/L, respectively) and decreased only with the remaining three solutions. The relationships between hemoglobin concentrations and both plasma SID and whole blood base excess throughout dilution were linear, with slopes proportional to the SID of the diluent in each case. Linear regression revealed that the SID of crystalloid producing a zero base excess/hemoglobin concentration slope during blood dilution (i.e., no change in metabolic acid-base status) is 23.7 mEq/L.

CONCLUSIONS

On in vitro hemodilution, there is a simple linear relationship between diluent crystalloid SID and the rate and direction of change of plasma SID and whole blood base excess. Direct extrapolation to in vivo situations such as acute normovolemic hemodilution and large volume correction of extracellular fluid deficits requires experimental confirmation.

Resuscitation with Hextend decreases endogenous circulating heparin activity and accelerates clot initiation after hemorrhage in the rabbit

Hemorrhagic shock can result in a hypercoagulable state and has been associated with both hemorrhagic and thrombotic complications in the perioperative period. The author hypothesized that hemorrhage and resuscitation could result in a hypercoagulable state via changes in the heparin-antithrombin III anticoagulant mechanism in rabbits. Rabbits sedated with ketamine underwent sham operation (n = 8) or hemorrhage (25 mL/kg blood shed) for 60 min, followed by resuscitation with an equal volume of 5% human albumin (n = 8) or Hextend (n = 8). Coagulation analysis with the Thrombelastograph analyzer and determination of endogenous heparin and antithrombin III activity were performed on arterial blood samples obtained before hemorrhage and 30 min after resuscitation. The reaction time significantly decreased by 34% after hemorrhage and resuscitation with Hextend, whereas no other significant changes in Thrombelastograph variables were noted. Antithrombin III activity was significantly less in the Albumin (83% +/- 8% of control, mean +/- SD) and Hextend (88% +/- 8%) Resuscitated groups compared with the Sham-Operated animals. Of interest, only the Hextend-Resuscitated animals demonstrated a significant decrease in heparin activity (53.4 +/- 13.6 mU/mL before hemorrhage, 42.3 +/- 5.6 mU/mL after resuscitation). A Hextend)-mediated decrease of both heparin and antithrombin III activity may explain the acceleration of clot initiation compared with albumin administration after hemorrhage in the rabbit.

IMPLICATIONS

Hemorrhage may result in a hypercoagulable state after resuscitation. Decreases in both endogenous heparin and antithrombin III activity after hemorrhage and Hextend resuscitation in rabbits resulted in a significantly decreased time to clot coagulation analysis initiation without a significant change in the rate of clot formation or final clot strength.

Isolation of high quality RNA from bilberry (Vaccinium myrtillus L.) fruit

A simple and efficient method is described for isolating high quality RNA from bilberry fruit. The procedure is based on the use of hexadecyltrimethyl ammonium bromide (CTAB), polyvinylpyrrolidone (PVP), and beta-mercaptoethanol in an extraction buffer in order to eliminate the polysaccharides and prevent the oxidation of phenolic compounds. This method is a modification of the one described for pine trees, and yields high-quality RNA suitable for cDNA based methodologies. This method is applicable for a variety of plant tissues.

Influence of plasma proteins on erythrocyte aggregation in three mammalian species

The aggregation capacity of human erythrocytes lies between that of the non-aggregating bovine erythrocytes and the remarkably aggregating equine ones. As the ability to aggregate is attributed to cell factors and the composition of the plasma proteins, the role that plasma proteins play in the aggregation process in these three species was studied. Washed erythrocytes were suspended in phosphate-buffered saline (PBS; pH 7.4, 300 mOsm/L) plus polyvinylpyrrolidone (PVP) in a suitable concentration to obtain an average intensity of aggregation (control media). The superimposed effect of replacing 80% of the medium by either autologous plasma, serum or albumin solution was studied. The plasma proteins appeared to enhance aggregation by human and equine erythrocytes, but impaired this process in bovine erythrocytes. Some evidence was obtained supporting the existence of serum factors capable of reducing aggregation of erythrocytes in cattle and it was concluded that the non-aggregating behaviour of bovine erythrocytes may be due to the cells interacting particularly with the macromolecules in the serum.

Acidosis or inorganic phosphate enhances the length dependence of tension in rat skinned cardiac muscle

1. We investigated the effect of acidosis on the sarcomere length (SL) dependence of tension generation, in comparison with the effect of inorganic phosphate (P(i)), in rat skinned ventricular trabeculae. The shift of the mid-point of the pCa-tension relationship associated with an increase in SL from 1.9 to 2.3 microm (DeltapCa(50)) was studied. 2. Decreasing pH from 7.0 to 6.2 lowered maximal and submaximal Ca(2+)-activated tension and increased DeltapCa(50) in a pH-dependent manner (from 0.21 +/- 0.01 to 0.30 +/- 0.01 pCa units). The addition of P(i) (20 mM) decreased maximal tension and enhanced the SL dependence, both to a similar degree as observed when decreasing pH to 6.2 (DeltapCa(50) increased from 0.20 +/- 0.01 to 0.29 +/- 0.01 pCa units). 3. Further experiments were performed using 6 % (w/v) Dextran T-500 (molecular weight approximately 500 000) to osmotically reduce interfilament lattice spacing (SL, 1.9 microm). Compared with that at pH 7.0, in the absence of P(i) the increase in the Ca(2+) sensitivity of tension induced by osmotic compression was enhanced at pH 6.2 (0.18 +/- 0.01 vs. 0.25 +/- 0.01 pCa units) or in the presence of 20 mM P(i) (0.17 +/- 0.01 vs. 0.24 +/- 0.01 pCa units). 4. H(+), as well as P(i), has been reported to decrease the number of strongly binding cross-bridges, which reduces the co-operative activation of the thin filament and increases the pool of detached cross-bridges available for interaction with actin. It is therefore considered that during acidosis, the degree of increase in the number of force-generating cross-bridges upon reduction of interfilament lattice spacing is enhanced, resulting in greater SL dependence of tension generation. 5. Our results suggest that the Frank-Starling mechanism may be enhanced when tension development is suppressed due to increased H(+) and/or P(i) under conditions of myocardial ischaemia or hypoxia.

[Volume expansion during septic shock]

At its very early phase, septic shock is characterized by severe hypovolemia related to abundant fluid losses, increased venous compliance and maldistribution of extracellular fluid (interstitial edema, splanchnic pooling). It results in a drop in venous return and cardiac output. Volume expansion, with crystalloids or colloids produces a hyperdynamic state with high cardiac output and low peripheral resistances. The quantity of liquid administered rather than its composition is the main determinant. Clinical examination and hemodynamic monitoring (Swan-Ganz catheter) appear to provide the most useful criteria to assess the limits of liquid administration. Better understanding in the mechanisms of circulatory dysfunction due to the inflammation cascades might soon lead to a new approach in fluid therapy.

Qualitative evaluation of the blood-brain barrier after the use of hypertonic saline solution in young rats

The blood-brain barrier (BBB) controls the biochemical environment of the brain with variable permeability when comparing adults to children. Based on the knowledge that there is a greater vulnerability in the BBB of young subjects submitted to biochemical variations in the blood and in the brain, an experimental model was designed to study small volume resuscitation. Young Wistar rats were submitted to hemorrhage and resuscitated with 7.5% NaCl solution before undergoing a qualitative evaluation of their BBB. Thirty male rats were anesthetized and divided into four groups: Group 1 - submitted to hemorrhagic shock restored with hypertonic saline solution (HSS); Group 2 - submitted to hemorrhagic shock without volume restoration; Group 3 - receiving only HSS, and Group 4 - control. The data analyzed were: mean arterial blood pressure, base excess, sodium, chloride, urea, blood osmolarity and blood glucose levels. After infusing a 2% Evans blue solution, qualitative analysis of the BBB was carried out. Group 1 presented final mean blood pressure levels equivalent to groups 3 and 4. Group 2 had a significant difference in the final base excess when compared to the other groups. In groups 1 and 3, mean sodium and chloride, as well as serum osmolarity, were more elevated than groups 2 and 4. Macroscopic examination of the brain did not reveal any changes in color, which could be attributed to the opening of the BBB. It was concluded that the 7.5% NaCl solution in this experimental model did not promote qualitative changes in the BBB.

High viscosity plasma expanders: Volume restitution fluids for lowering the transfusion trigger

Hemorheological studies lead to the axiom that high plasma viscosity is detrimental and that it is beneficial to lower blood viscosity, a precept embodied in the practice of hemodilution, where improved perfusion is attributed to the lowering of blood viscosity. Hemodilution is limited by the transfusion trigger, hemoglobin content of blood of about 7-8 g/dl, which indicates when further volume replacements must restore oxygen carrying capacity with red blood cells (RBC). However, oxygen consumption and delivery are not compromised upon passing this landmark. The reduced blood viscosity does not transmit adequate pressure to the capillaries, causing functional capillary density (FCD) to decrease, jeopardizing organ function through the inadequate extraction of products of metabolism from the tissue by the capillaries. Studies in hemorrhagic shock show that survival is primarily determined by the maintenance of FCD and secondarily by tissue oxygenation. FCD is maintained as hematocrit is reduced beyond the transfusion trigger by increasing plasma viscosity, which transmits systemic pressure to the capillaries and induces vasodilatation through the increased shear stress dependent release of vasodilators. Consequently the transfusion trigger is also a "viscosity trigger" indicating when blood and plasma viscosity are too low. In this condition increasing plasma viscosity is beneficial and extends the transfusion trigger reducing the use of blood transfusions.

Systemic and splanchnic hemodynamics following hemorrhage and volume restitution with Haemaccel in portal hypertensive rats: the effect of propranolol

BACKGROUND AND AIMS

Recently, we found in a portal hypertensive rat model that hemorrhage and volume restitution with Haemaccel, a low viscosity plasma expander, induced an increase in cardiac output and portal venous inflow. The present study was conducted to evaluate whether pretreatment with propranolol will attenuate these hyperdynamic changes.

METHODS

Portal hypertension was induced by portal vein constriction. Treatment was initiated 14--21 days later. Propranolol (30 mg/kg per day) or water were administered for 7 days via a gastric gavage. Under ketamine anesthesia, 18 h after the last given dose, blood was withdrawn at a constant rate of 0.3 mL/min for 15 min followed by a 15-min stabilization. Haemaccel was infused at the same rate and volume used for withdrawal. Hemodynamic measurements were performed after volume restitution in both groups by using radioactive microspheres.

RESULTS

Eight rats were studied in each group. In the propranolol-treated animals, portal venous inflow was decreased (2.4 +/- 0.8 vs 3.8 +/- 0.7 mL/min per 100 g bodyweight; P < 0.01), while splanchnic arteriolar and porto-collateral resistance were increased (52.8 +/- 21.0 vs 32.8 +/- 13.0 and 6.0 +/- 1.4 vs 4.1 +/- 0.7 mmHg x min x 100 g bodyweight/mL; P < 0.05, respectively). Cardiac output, mean arterial pressure, heart rate, total peripheral resistance and portal pressure were not significantly different between the two groups.

CONCLUSION

In this model, pretreatment with propranolol prevented the increase in portal venous inflow, which occurs following hemorrhage and volume restitution with Haemaccel. Although caution should be taken in extrapolating data from animal models to humans, our results suggest that volume replacement during a portal hypertensive-related bleeding episode may be safer in a patient treated with non-selective beta-adrenoreceptor antagonists.

Fetal oxygen content is restored after maternal hemorrhage and fluid replacement with polymerized bovine hemoglobin, but not with hetastarch, in pregnant sheep

We investigated the ability of hemoglobin-based oxygen carrying solutions (HBOCs) to alleviate fetal hypoxemia from maternal hemorrhage. Fifteen pregnant ewes (132-day gestational age) were hemorrhaged 20 mL/kg over 1 h; they were randomized to receive 20 mL/kg IV of HBOC, hetastarch (HTS), or autologous blood (BLD) (n = 5 each) over 30 min and were monitored for 2 h. Hemorrhage significantly (P < or = 0.05) decreased maternal mean blood pressure (from 98 to 48 mm Hg, median), arterial oxygen content (from 12.2 to 11.1 mL/dL), and fetal arterial oxygen content (from 8.1 to 3.9 mL/dL). Fluid replacement restored maternal blood pressure in all groups, although maternal oxygen content immediately returned to baseline only after BLD or HBOC. Maternal oxygen saturation decreased after HBOC (from 98% to 88%). Fetal oxygen content rapidly returned to baseline with either BLD (7.1 mL/dL) or HBOC (8.0 mL/dL) but was never restored with HTS (4.7 mL/dL), and, 60 min after fluid replacement, it was higher with HBOC (8.3 mL/dL) than with HTS (4.7 mL/dL). Fetal plasma-free hemoglobin did not change after HBOC. In conclusion, maternal fluid replacement with HBOC or BLD effectively restored fetal oxygenation, primarily by restoring maternal oxygen content, whereas HTS did not.

IMPLICATIONS

Hemoglobin solutions eliminate many limitations of blood transfusions. Our results show that fluid replacement with either blood or a hemoglobin solution, compared with hetastarch, restored fetal oxygenation in pregnant ewes after hemorrhage. If applicable to women, these results suggest a potential for the use of hemoglobin solutions in obstetrics.

The Effects of Hydroxyethyl Starches of Varying Molecular Weights on Platelet Function

We evaluated the effect of various hydroxyethyl starch (HES) solutions on platelet function. Blood was obtained before and after the IV infusion (10 mL/kg) of saline (n = 10), HES 70/0.5--0.55 (molecular weight in kD/degree of substitution; n = 10), HES 130/0.38--0.45 (n = 10), HES 200/0.6--0.66 (n = 10), or HES 450/0.7--0.8 (n = 10) in otherwise healthy patients scheduled for elective surgery. Collagen and epinephrine were used as agonists for assessment of platelet function analyzer closure times. Flow cytometry was used to assess agonist-induced expression of activated glycoprotein IIb/IIIa complex and P-selectin. Infusion of HES 450/0.7--0.8, HES 200/0.6--0.66, and HES 70/0.5--0.55 prolonged closure times and reduced glycoprotein IIb/IIIa expression, whereas saline and HES 130/0.38--0.45 had no significant effect on platelet variables. P selectin expression was not affected by any solution tested. In vitro experiments demonstrated a less inhibiting effect of HES 130/0.38--0.45 on closure times when compared with other HES solutions. This study shows that HES 450/0.7--0.8, HES 200/0.6--0.66, and HES 70/0.5--0.55 inhibit platelet function by reducing the availability of the functional receptor for fibrinogen on the platelet surface. Our data indicate that fluid resuscitation with HES 130/0.38--0.45 may reduce the risk of bleeding associated with synthetic colloids of higher molecular weight and degree of substitution.

Hemostatic Changes in Patients Receiving Hydroxyethyl Starch: The Influence of ABO Blood Group

Hydroxyethyl starches (HES) interfere with coagulation because of their molecular structure and the amount infused during surgery. Coagulation defects include platelet dysfunction and a decrease of the VIII/von Willebrand factor complex (VIII/vWF). We examined the effects of 6% HES 200/0.6 on hemostasis by using an in vitro platelet function analyzer, the usual coagulation tests, the VIII/vWF complex assessment, and TEG analysis in patients undergoing abdominal surgery. The influence of the blood group was investigated. HES infusion induced primary hemostasis alterations, assessed by a prolonged platelet function analyzer closure time in the presence of epinephrine and adenosine diphosphate, which was not correlated with the platelet count. The decrease in VIII/vWF complex was proportional to the volume of infused HES (20 and 30 mL/kg) and was more pronounced in patients of the O blood group. The preoperative hypercoagulability status assessed by TEG analysis was reversed 24 h after HES infusion. In conclusion, 6% HES 200/0.6 induced immediate hemostasis alterations. Patients of the O blood group were likely to develop a von Willebrand-like syndrome after HES infusion. We conclude that intraoperative use of 6% HES 200/0.6 should be restricted in patients of the O blood group undergoing surgical procedures with high risk for bleeding.

Influence of a new hydroxyethylstarch preparation (HES 130/0.4) on coagulation in cardiac surgical patients

OBJECTIVE

To compare volume therapy with HES 130/0.4, a new hydroxyethylstarch (HES) solution with a gelatin-based fluid replacement strategy.

DESIGN

Prospective, randomized, safety study.

SETTING

Urban, university-affiliated hospital (single institution).

PARTICIPANTS

Forty-two patients undergoing elective cardiac surgery.

INTERVENTIONS

Patients were prospectively randomized into 2 groups: In group 1 (n = 21), gelatin was given perioperatively for volume support until the 1st postoperative day to keep the central venous pressure (CVP) between 10 and 14 mmHg; in group 2 (n = 21) HES 130/0.4 was administered using the same protocol as in group 1.

MEASUREMENTS AND MAIN RESULTS

Standard coagulation variables and modified thromboelastography (TEG) were used. Using different activators for extrinsic and intrinsic activation and heparin inactivation by heparinase, the onset of coagulation (coagulation time), kinetics of clot formation (clot formation time), and maximum clot firmness were measured. Measurements were performed after induction of anesthesia (T0), at the end of surgery (T1), 4 hours after surgery (T2), and on the morning of the 1st postoperative day (T3). A total of 3310 +/- 810 mL of gelatin and 3070 +/- 570 mL of HES 130/0.4 were used in the 2 groups during the study period. The 2 groups did not differ with regard to postoperative bleeding or in use of packed red blood cells or fresh frozen plasma. Standard coagulation variables were similar between the 2 groups. All TEG variables were within the normal range at baseline. Coagulation time and clot formation time data were significantly elevated after surgery and in the intensive care unit, without showing specific differences between the 2 volume replacement groups. Intrinsic TEG and heparinase TEG clot formation times remained significantly higher until the end of the study period. No differences were seen between HES-treated and gelatin-treated patients.

CONCLUSIONS

Volume replacement with the new HES preparation was as safe as gelatin-based volume replacement with regard to coagulation in cardiac surgical patients. HES 130/0.4 is an alternative plasma substitute to treat volume deficits.

Effects of different plasma substitutes on blood coagulation: a comparative review

OBJECTIVE

To compare the effects of different colloid plasma substitutes on blood coagulation and postoperative blood loss.

DATA SOURCES

Relevant studies were obtained from the medical literature.

STUDY SELECTION

Articles were selected that provided data on the effects of colloids on hemostasis and postoperative blood loss in humans. Studies comparing different colloids were looked for using MEDLINE and by searching through the references of studies as they were collected.

DATA SYNTHESIS

Articles were reviewed and relevant data were extracted and partly presented in comparative tables.

CONCLUSIONS

Dextran, gelatin, and hydroxyethyl starch (HES) all can induce a specific decrease of von Willebrand factor and factor VIII:c. Blood coagulation is most impaired by dextran and high molecular weight HES, both associated with increased postoperative blood loss. The effects of HES on blood coagulation have been shown to depend on its molecular weight and rate of elimination. Detrimental effects have been shown for high molecular weight HES. Medium molecular weight (MMW)-HES with a high degree of substitution (HES 200/0.62) and MMW-HES with high C2/C6 hydroxyethylation ratio (HES 200/0.5/13) are slowly degradable and have been shown to impair blood coagulation after repeated administration. Rapidly degradable HES 200/0.5/6 and gelatin-based plasma expanders appear not to impair hemostasis. However, based on the reviewed literature, all artificial colloids could potentially induce increased bleeding tendency after infusion of very large volumes and especially when given to patients with even mild forms of von Willebrand disease. In those circumstances, crystalloid solutions or alternatives such as plasma or albumin, although associated with other serious complications, could be considered.

[Use of an artificial carrier of oxygen on the base of modified hemoglobin in patients with gastroduodenal hemorrhage]

Infusions of Helenpole used in 23 patients allowed for a short time to stabilize hemodynamics and to considerably improve the gas-transporting function of blood. The best curative effect in patients with hemorrhagic shock was obtained by means of intravenous jet infusions of the medicine, after stabilization of the hemodynamic indices with the help of an intravenous dropper (80-90 drops/min). The dose of the 1% solution of the medicine was 25-30 ml/kg of the patient's body weight.

The effect of priming techniques of ultrafiltrators on blood rheology: an in vitro evaluation

The increased interest of using ultrafiltration during cardiopulmonary bypass ICPB) has mandated a re-evaluation of the hematological effects of this blood conservation process. 'Rinse-free' ultrafiltrators can be primed using either crystalloid or blood prior to use. It is unknown whether one priming technique results in superior results in ultrafiltration quality. An in vitro circuit was designed to evaluate the Sorin/COBE HC1400 (n=6), the Lifestream HC70 (n=6), and the Terumo/Sarns HC11 (n=6). All test conditions were conducted at a blood flow rate of 250 ml/min and a transmembrane pressure of 250 mmHg. Samples were drawn and analyzed at four distinct time points for hematocrit, total protein, plasma free hemoglobin, interleukin-6 (IL-6), interleukin-8 (IL-8), and tumor necrosis factor-alpha (TNFalpha). The HC11 had significantly greater percent increases in hematocrit under the blood priming protocol (29.2+/-7.9) than either the HC1400 (11.0+/-7.8, p<0.03) or the HC70 (11.9+/-7.8, p<0.04). When crystalloid priming was compared to blood priming, the HC1400 and HC70 produced significant percent increases in hematocrit and total protein levels. The HC1400 devices produced significantly less plasma free hemoglobin when primed with crystalloid rather than blood (43.6+/-38.3 vs 21.3+/-5.6, p<0.01). There were no significant differences between devices or priming techniques for IL-6, IL-8 or TNFalpha levels. In conclusion, the efficiency of the ultrafiltrators was elevated when primed with crystalloid before use. Cytokine levels were relatively unchanged with priming techniques, while plasma free hemoglobin levels were reduced with those devices previously primed with crystalloid.

Renal proximal tubule function is preserved in Cftr(tm2cam) deltaF508 cystic fibrosis mice

1. Changes in proximal tubule function have been reported in cystic fibrosis patients. The aim of this study was to investigate proximal tubule function in the Cftr(tm2cam)deltaF508 cystic fibrosis (CF) mouse model. A range of techniques were used including renal clearance studies, in situ microperfusion, RT-PCR and whole-cell patch clamping. 2. Renal Na(+) clearance was similar in wild-type (1.4 +/- 0.3 microl min(-1), number of animals, N = 12) and CF mice (1.6 +/- 0.4 microl min(-1), N = 7) under control conditions. Acute extracellular volume expansion resulted in significant natriuresis in wild-type (7.0 +/- 0.8 microl min(-1), N = 8) and CF mice (9.3 +/- 1.4 microl min(-1), N = 9); no difference between genotypes was observed. 3. In situ microperfusion revealed that fluid absorptive rate (Jv) was similar under control conditions between wild-type (2.2 +/- 0.4 nl mm(-1) min(-1), n = 10) and CF mice (1.9 +/- 0.3 nl mm(-1) min(-1), n = 11). Addition of a forskolin-dibutyryl cAMP (db-cAMP) cocktail to the perfusate caused no significant change in Jv in either wild-type (2.6 +/- 0.7 nl mm(-1) min(-1), n = 10) or Cftr(tm2cam)deltaF508 mice (2.0 +/- 0.5 nl mm(-1) min(-1), n = 10). 4. CFTR expression was confirmed in samples of outer cortex using RT-PCR. However, no evidence for functional CFTR was obtained when outer cortical cells were stimulated with protein kinase A or forskolin-db-cAMP using whole-cell patch clamping. 5. In conclusion, no functional deficit in proximal tubule function was found in Cftr(tm2cam)deltaF508 mice. This may be a consequence of a lack of whole-cell cAMP-dependent Cl(-) conductance in mouse proximal tubule cells.

Changes in circulating blood volume after infusion of hydroxyethyl starch 6% in critically ill patients

BACKGROUND

The cardiovascular response to a volume challenge with hydroxyethyl starch (HES) (200/0.5) 6% depends on the relation between the volume of HES 6% infused and the expansion of the blood volume in critically ill patients. However, only relatively limited data exist on the plasma expanding effect of infusion of HES 6% in critically ill patients. The purpose of the study was to evaluate the variation in the expansion of the circulating blood volume (CBV) in critically ill patients after infusion of 500 ml of colloid (HES (200/0.5) 6%) using the carbon monoxide method.

METHODS

In 20 consecutive patients admitted to the ICU requiring mechanical ventilation and volume expansion, 500 ml of HES (200/0.5) 6% was infused. The CBV was measured immediately before the infusion, 10 min after completing the infusion and then hourly for 8 h.

RESULTS

The median volume expansion immediately after infusion was 470 ml (range 270 ml to 840 ml). The corresponding values after 4 h and 8 h were 265 ml (range -30 ml to 460 ml) and 120 ml (range -210 ml to 360 ml), respectively. The increase in CBV was only statistically significant for 4 h. The coefficient of variation of the method for estimation of CBV was 3.6%.

CONCLUSIONS

The large interindividual variation of the volume expansion after infusion of HES 6% in critically ill patients illustrates one of the difficulties in optimizing colloid therapy and interpretating the changes in hemodynamic variables after a colloid challenge.

Acute plasma volume expansion in the untrained alters the hormonal response to prolonged moderate-intensity exercise

To investigate the role of an increase in plasma volume (PV), characteristically observed with short-term endurance training, on the endocrine response to prolonged moderate intensity exercise, eight untrained males (VO2 peak = 3.52 +/- 0.12 l x min(-1)) performed 90 min of cycle ergometry at approximately 60% VO2peak both before (CON) and following (PVX) PV expansion. Acute PV expansion, which was accomplished using a solution of Dextran (6%) or Pentispan (10%) (6.7 ml kg(-1)), resulted in a calculated 15.8+/-2.2% increase (p<0.05) in PV. The prolonged exercise resulted in increases (p<0.05) in plasma vasopressin (AVP), plasma rennin activity (PRA), aldosterone (ALD), atrial naturetic peptide (alpha-ANP), and the catecholamines norepinephrine (NE) and epinephrine (EPI). PVX blunted the increases (p<0.05) in AVP, PRA, ALD, NE and EPI, during the exercise itself. The concentration of alpha-ANP was also lower (p<0.05) during exercise following PVX, an effect that could be attributed to the lower resting levels. No differences in osmolality was observed between conditions. These results demonstrate that PVX alters the fluid regulatory hormonal response in untrained subjects to moderate intensity dynamic exercise in a manner similar to that observed following short-term training induced alterations in PV. The specific mechanisms responsible for these alterations remain unclear, but appear to be related directly to the increase in PV.

Increased cGMP phosphodiesterase activity mediates renal resistance to ANP in rats with bile duct ligation

BACKGROUND

Liver disease resulting from common bile duct ligation (CBDL) causes abnormal sodium metabolism that is manifested by resistance to the natriuretic action of atrial natriuretic peptide (ANP). This resistance is corrected both in vitro and in vivo by zaprinast, a selective inhibitor of a guanosine cyclic-3'-5'-monophosphate (cGMP)-specific phosphodiesterase (PDE5). Several other PDEs with affinity for cGMP are expressed in kidney and could also be involved in this response.

METHODS

We measured cGMP hydrolysis in inner medullary collecting duct (IMCD) cell homogenates from kidneys of sham-operated and CBDL rats and quantitated the amount of PDE5 protein by Western blotting and immunoprecipitation studies. We also characterized ANP responsiveness in vivo of kidneys of anesthetized sham and CBDL rats by measuring sodium excretion before and after volume expansion (VE).

RESULTS

Kinetic analysis of PDE5 activity in homogenates of IMCD cells isolated from kidneys of sham-operated rats indicated a Vmax of 85.3 +/- 1.7 versus 157 +/- 2.9 pmol/mg/min from CBDL rats (P < 0.01), without a difference in Km. Enzyme activity was inhibited competitively by 1,3-dimethyl-6-(2-propoxy-5-methanesulfonylamidophenyl)pyrazol[3,4d]-pyrimidin-4-(5H)-one (DMPPO), a potent and specific inhibitor of PDE5, with an apparent Ki of 4.5 +/- 0.7 and 4.9 +/- 0.7 nmol/L and an IC50 of 6.1 +/- 0.8 and 8.7 +/- 0.7 nmol/L in sham and CBDL rats, respectively (P = NS). DMPPO exhibited very poor inhibitory activity against the calcium-calmodulin-dependent PDE1 in IMCD homogenates from sham rats (Ki 1.3 +/- 0.1 micromol/L and IC50 1.9 +/- 0.2 micromol/L). Western analysis using an antiserum made against bovine lung PDE5 revealed a twofold increase in PDE5 protein in cytosolic extracts from IMCD of CBDL rat kidneys compared with sham-operated controls, and immunoprecipitation studies indicated that the increase in PDE5 protein accounted for the observed increase in cGMP hydrolysis. DMPPO (10 nmol/L) normalized the blunted ANP-dependent cGMP accumulation by IMCD cells from CBDL rats in vitro. Intrarenal infusion of DMPPO (0.5 nmol/min) in CBDL rats corrected both the impaired natriuretic response to VE and the blunted VE-related increase in urinary cGMP excretion from the infused, but not the contralateral kidney.

CONCLUSION

These results demonstrate that renal resistance to ANP in CBDL rats is accompanied by heightened activity of PDE5, which is due largely to an increase in PDE5 protein. Other PDEs could contribute only a minor part to the enhanced cGMP hydrolysis observed in kidneys of CBDL rats. This PDE5-dependent ANP resistance may represent an important contributor to the sodium retention of liver disease.

The influence of intravascular volume therapy with a new hydroxyethyl starch preparation (6% HES 130/0.4) on coagulation in patients undergoing major abdominal surgery

A new hydroxyethyl starch (HES) preparation with a mean molecular weight of 130,000 daltons and a degree of substitution of 0.4 shows favorable pharmacokinetic properties. We conducted a study of the influence of the new HES specification on coagulation and compared it with another colloidal intravascular volume replacement regimen using gelatin. According to a prospective, random sequence, 42 patients undergoing major abdominal surgery received either HES 130/0.4 (n = 21) or gelatin (n = 21) until the first postoperative day (POD) to keep central venous pressure between 10 and 14 mm Hg. From arterial blood samples, standard coagulation variables were measured, and modified thrombelastogram (TEG) measurements using different activators were performed. A total of 2830 +/- 350 mL of gelatin and 2430 +/- 310 mL of HES 130/0.4 were administered until the morning of the first POD. The use of allogeneic blood/blood products and standard coagulation variables did not differ significantly between the two groups. After induction of anesthesia, all TEG data for both groups were within normal range. Coagulation time and maximum clot firmness did not change significantly in any TEG measurements during the study period. The kinetics of clot formation (clot formation time) significantly increased immediately after surgery, but without showing significant group differences. On the morning of the first POD, the clot formation time returned to almost normal levels, except for aprotinin-activated TEG(R). We conclude that administration of moderate doses of the new HES 130/0.4 preparation in patients undergoing major abdominal surgery results in similar coagulation alterations as those after using an established gelatin-based volume-replacement regimen.

IMPLICATIONS

We compared the effects of infusion of a new hydroxyethyl starch preparation (6% hydroxyethyl starch; mean molecular weight 130,000 daltons; degree of substitution 0.4) on coagulation with a gelatin-based intravascular volume replacement regimen in patients undergoing major abdominal surgery. After moderate doses of hydroxyethyl starch (2430 +/- 310 mL until the morning of the first postoperative day), coagulation monitoring, including modified thrombelastography, did not show impaired hemostasis.

[Effect of serum and osmotically active substances on metabolism in 262 tissue cultures of pig's corneas--improved preservation of donor tissue for keratoplasty]

BACKGROUND

The storage time of corneal organ cultures in limited in the closed system mainly used in European eye banks. In addition, swelling during storage reduces the quality of the donor material for keratoplasty. Therefore, dextrane was added in concentrations of 2.5%, 5%, 7.5% and 10% to the culture medium, and the energy producing metabolism was investigated.

MATERIALS AND METHODS

The experiments were carried out with 262 pig corneas. MEM with some supplements was used at 31 degrees C. No serum was added, because glucose consumption, lactate production and ATP levels proved to be the same or better than with serum supplement. After 6 and 12 days, the corneas from organ cultures were extracted with perchloric acid. The levels of glucose and lactate in the stroma and of ATP and ADP in the epithelium were analysed with enzymatic-optical tests.

RESULTS

Dextrane inhibited glycolysis and the production of ATP in corneal organ cultures during twelve days. With 7.5% and 10% dextrane in the medium, lactate levels in the cornea decreased from 6.09 to 4.5 and 4.6 microM/g H2O instead of increasing. At the same time, glucose increased paradoxical from 1.3 to 3.4 and 2.2 microM/g H2O, respectively. With 5% dextrane, glycolysis operated sufficiently producing an increase of lactate levels from 6.0 to 8.8 microM/g H2O and consuming glucose from levels of 1.27 down to 0.57 microM/g H2O. After 12 days with 7.5% and 10.0% dextrane, ATP levels were reduced, from 4.54 to 0.98 and 0.49 microM/g dry weight, and ATP/ADP ratios from 1.9 to 1.1 and 0.7 respectively. With 2.5% dextrane, the ATP was diminished from 4.5 to 2.2 microM/g dry weight. When 5% dextrane were added to the culture medium, the hydration was at optimum by 4.1, and ATP levels were reduced only from 4.5 to 2.6 microM/g dry weight. Moreover, the ATP/ADP ratios were at 2.1 as good as without dextrane.

CONCLUSIONS

From the results it was concluded, that serum free medium may be used, and that permanent dewelling proved to be beneficial for the energy producing metabolism of the cornea in organ culture. Such conditions may improve morphological and metabolic quality of donor material. From previous publications, it was recommended, to use instead of toxic dextran the well tolerated HES (hydroxyethyl starch) and to apply a storage temperature of 21 degrees C, which slowed down glucose consumption without impairing the energy producing metabolism.

Volume expansion potentiates cardiac sympathetic afferent reflex in dogs

Our previous study (27) showed that the cardiac sympathetic afferent reflex (CSAR) was enhanced in dogs with congestive heart failure. The aim of this study was to test whether blood volume expansion, which is one characteristic of congestive heart failure, potentiates the CSAR in normal dogs. Ten dogs were studied with sino-aortic denervation and bilateral cervical vagotomy. Arterial pressure, left ventricular pressure, left ventricular epicardial diameter, heart rate, and renal sympathetic nerve activity were measured. Coronary blood flow was also measured and, depending on the experimental procedure, controlled. Blood volume expansion was carried out by infusion of isosmotic dextran into a femoral vein at 40 ml/kg at a rate of 50 ml/min. CSAR was elicited by application of bradykinin (5 and 50 microg) and capsaicin (10 and 100 microg) to the epicardial surface of the left ventricle. Volume expansion increased arterial pressure, left ventricular pressure, left ventricular diameter, and coronary blood flow. Volume expansion without controlled coronary blood flow only enhanced the RSNA response to the high dose (50 microg) of epicardial bradykinin (17. 3 +/- 1.9 vs. 10.6 +/- 4.8%, P < 0.05). However, volume expansion significantly enhanced the RSNA responses to all doses of bradykinin and capsaicin when coronary blood flow was held at the prevolume expansion level. The RSNA responses to bradykinin (16. 9 +/- 4.1 vs. 5.0 +/- 1.3% for 5 microg, P < 0.05, and 28.9 +/- 3.7 vs. 10.6 +/- 4.8% for 50 microg, P < 0.05) and capsaicin (29.8 +/- 6.0 vs. 9.3 +/- 3.1% for 10 microg, P < 0.05, and 34.2 +/- 2.7 vs. 15.1 +/- 2.7% for 100 microg, P < 0.05) were significantly augmented. These results indicate that acute volume expansion potentiated the CSAR. These data suggest that enhancement of the CSAR in congestive heart failure may be mediated by the concomitant cardiac dilation, which accompanies this disease state.