Antithrombin III during cardiac surgery: effect on response of activated clotting time to heparin and relationship to markers of hemostatic activation

This study was designed to determine if, and to what extent, antithrombin III (AT) levels affect the response of the activated clotting time (ACT) to heparin in concentrations used during cardiac surgery, and to characterize the relationship between AT levels and markers of activation of coagulation during cardiopulmonary bypass (CPB). After informed consent, blood specimens obtained from eight normal volunteers (Phase I) were used to measure the response of the kaolin and celite ACT to heparin after in vitro addition of AT (200 U/dL) and after dilution with AT-deficient plasma to yield AT concentrations of 20, 40, 60, 80, and 100 U/dL. In Phase II, blood specimens collected before the administration of heparin and prior to discontinuation of CPB, were used to measure the response of the kaolin ACT to heparin (preheparin only), AT concentration, and a battery of coagulation assays in 31 patients undergoing repeat or combined cardiac surgical procedures. In Phase I, strong linear relationships were observed between kaolin (slope = 1.04 AT - 2, r2 = 0.78) and celite (slope = 1.36 AT + 6, r2 = 0.77) ACT slopes and AT concentrations below 100 U/dL. In the pre-CPB period of Phase II, only factors V (partial r = -0.49) and VIII (partial r = -0.63) were independently associated with heparin-derived slope using multivariate analysis; an inverse relationship was observed between AT and fibrinopeptide A levels (r = -0.41) at the end of CPB. Our findings indicate that the responsiveness of whole blood (ACT) to heparin at the high concentrations used with CPB is progressively reduced when the AT concentration decreases below 80 U/dL. Because AT is variably, and sometimes extensively, reduced in many patients before and during CPB, AT supplementation in these patients might be useful in reducing excessive thrombin-mediated consumption of labile hemostatic blood components, excessive microvascular bleeding, and transfusion of blood products. IMPLICATIONS: Heparin, a drug with anticoagulant properties, is routinely given to patients undergoing cardiac surgery to prevent clot formation within the cardiopulmonary bypass circuit. However, when levels are reduced, heparin is not as effective. Findings within this study indicate that administration of antithrombin III may help to preserve the hemostatic system during cardiopulmonary bypass.     

Extracorporeal heparin adsorption following cardiopulmonary bypass with a heparin removal device--an alternative to protamine

OBJECTIVES: To evaluate the therapeutic efficacy and applicability of a heparin removal device (HRD) based on plasma separation and poly-L-lysine (PLL) affinity adsorption as an alternative to protamine in reversing systemic heparinization following cardiopulmonary bypass (CPB). DESIGN: A prospective study. SETTING: University research laboratory. SUBJECTS: Adult female swine (n=7). INTERVENTIONS: Female Yorkshire swine (n=7, 67.3+/-3.5 [SEM] kg) were subjected to 60 mins of right atrium-to-aortic, hypothermic (28 degrees C) CPB. After weaning from CPB, the right atrium was recannulated with a two-stage, dual-lumen cannula which was connected to an HRD via extracorporeal circulation. Blood flow was drained at 1431.2+/-25.4 mL/min from the inferior vena cava, through the plasma separation chamber of the HRD (where heparin was bound to PLL), and reinfused into the right atrium. The HRD run time was determined by a previously established mathematical model of first-order exponential depletion. MEASUREMENTS AND MAIN RESULTS: Heart rate, mean arterial pressure, pulmonary arterial pressure, central venous pressure, kaolin and celite activated clotting time (ACT), activated partial thromboplastin time (APTT), heparin concentration, and plasma free hemoglobin were obtained before, during, and after the use of the HRD. Pre-CPB ACT was 167+/-89 secs (kaolin) and 99+/-7 secs (celite), and APTT was 34+/-5 secs. The HRD run time averaged 27.4 +/-1.5 mins targeted to remove 90% total body heparin. Use of the HRD was not associated with any adverse hemodynamic reactions or increases in plasma free hemoglobin. The heparin concentration immediately following CPB was 4.85+/-0.24 units/mL, with ACT >1000 secs and APTT >150 secs in all animals. During heparin removal, total body heparin content followed first-order exponential depletion kinetics. At the end of the HRD run, heparin concentration decreased to 0.51+/-0.09 units/mL, with kaolin ACT returning to 177+/-22 secs, celite ACT returning to 179+/-17 secs, and APTT returning to 27+/-3 secs (p > .05 vs. pre-CPB baseline for all variables). CONCLUSIONS: The HRD is capable of reversal of anticoagulation following CPB without significant blood cell damage or changes in hemodynamics. The HRD, therefore, can serve as an alternative to achieve heparin clearance in clinical situations where use of protamine may be contraindicated.     

Cystic fibrosis transmembrane conductance regulator mediates the cyclic adenosine monophosphate-induced fluid secretion but not the inhibition of resorption in mouse gallbladder epithelium

The haemostatic system and the use of heparin during cardiopulmonary bypass (CPB) have been studied extensively in adults but not in children. Results from adult trials cannot be extrapolated to children because of age-dependent physiologic differences in haemostasis. We studied 22 consecutive paediatric patients who underwent CPB at The Hospital for Sick Children, Toronto. Fibrinogen, factors II, V, VII, VIII, IX, XII, prekallikrein, protein C, protein S, antithrombin (AT), heparin cofactor II, alpha 2-macroglobulin, plasminogen, alpha 2-antiplasmin, tissue plasminogen activator (tPA), plasminogen activator inhibitor, thrombin-AT complexes (TAT), D-dimer, heparin (by both anti-factor Xa assay and protamine titration) and activated clotting time (ACT) were assayed perioperatively. The timing of the sampling was: pre heparin, post heparin, after initiation of CPB, during hypothermia, post hypothermia, post protamine reversal and 24 h post CPB. Plasma concentrations of all haemostatic proteins decreased by an average of 56% immediately following the initiation of CPB due to haemodilution. During CPB, the majority of procoagulants, inhibitors and some components of the fibrinolytic system (plasminogen, alpha 2 AP) remained stable. However, plasma concentrations of TAT and D-dimers increased during CPB showing that significant activation of the coagulation and fibrinolytic systems occurred. Mechanisms responsible for the activation of haemostasis are likely complex. However, low plasma concentrations of heparin (< 2.0 units/ml in 45% of patients) during CPB were likely a major contributing etiology. ACT values showed a poor correlation (r = 0.38) with heparin concentrations likely due to concurrent haemodilution of haemostatic factors, activation of haemostatic system, hypothermia and activation of platelets. In conclusion, CPB in paediatric patients causes global decreases of components of the coagulation and fibrinolytic systems, primarily by haemodilution and secondarily by consumption.     

A comparison of thromboelastography with heparinase or protamine sulfate added in vitro during heparinized cardiopulmonary bypass

Thromboelastography (TEG) has been used after cardiopulmonary bypass (CPB) to diagnose excessive postoperative hemorrhage. Conventional TEG during CPB is not possible due to the sensitivity of the TEG to even small amounts of heparin, which produces a nondiagnostic tracing. The purpose of this study was to compare heparin neutralization using heparinase or protamine in TEG blood samples obtained during CPB. TEG testing was performed on 48 patients before, during and after CPB. Tissue plasminogen activator activity and antigen were measured on a subset of 32 patients. We found: 1) heparinase neutralized at least 10 IU/ml heparin while 1.6 ug/ml protamine neutralized up to 7 IU/ml heparin, 2) in samples with complete heparin neutralization by both methods, there was no significant difference in the R values, 3) while there was good correlation for other TEG parameters between heparinase and protamine treated samples, heparinase treatment produced shorter K values and higher angle, MA and A60, 4) while fibrinolysis was detected using both methods, heparinase treatment suppressed fibrinolysis in the TEG in both samples from patients and after in vitro addition of tissue plasminogen activator, 5) TEG was not a sensitive indicator of t-PA activity, detecting only 21% of samples with increased t-PA activity during bypass, and 5) heparinase was at least 100 times more expensive than protamine. We conclude that while both heparinase and protamine can be used to neutralize heparin in TEG samples obtained during CPB, protamine neutralization is more sensitive to fibrinolysis and less expensive, but the protamine dose must be carefully selected to match the heparin level used at individual institutions.     

Management of postoperative heparin rebound following cardiopulmonary bypass

Postoperative heparin rebound was investigated in 50 adult patients undergoing cardiopulmonary bypass with the use of the Hepcon heparin analyzer. Prior to bypass each patient received 2 mg/kg of heparin. During bypass, the activated clotting time (ACT) was utilized to assess the need for additional heparin to maintain the value between 300 and 400 seconds. The average amount of heparin given was 160 mg. Once cardiopulmonary bypass was terminated the Hepcon unit was employed to determine the actual amount of active circulating heparin and to calculate the dose of protamine sulfate. The average amount of protamine administered intraoperatively was 200 mg. The overall mean ratio of protamine-to-heparin was 1.25 : 1. Once hemostasis was achieved, no circulating heparin was measured with the Hepcon unit, and the ACT value had returned to its baseline, the incisions were closed and the patients were transferred to the intensive care unit. One hour later a blood sample was obtained and analyzed by the Hepcon unit for any heparin rebound. We found that 26 patients (52%) had circulating heparin and required an additional dose of protamine, averaging 70 mg. Drainage from the thoracotomy tubes averaged 400 cc in the first 24 hours, and a mean of 2 units of packed cells was infused. Three patients (6%) did not require any blood transfusions. The use of the Hepcon unit has produced a safe and expedient method of analyzing and neutralizing active circulating heparin in patients following cardiopulmonary bypass. It is a useful adjunct in blood conservation because it reduces excessive postoperative blood loss associated with heparin rebound.     

The effects of heparinase 1 and protamine on platelet reactivity

BACKGROUND: Protamine is currently the most widely used drug for the reversal of heparin anticoagulation. Heparinase 1 (heparinase) is being evaluated as a possible alternative to protamine for the reversal of heparin anticoagulation. The authors evaluated the effects of equivalent doses of heparinase and protamine on platelet reactivity by measuring agonist-induced P-selectin expression. METHODS: After Institutional Review Board (IRB) approval, informed consent was obtained from 12 healthy volunteers and 8 patients undergoing surgery requiring cardiopulmonary bypass (CPB). Twenty-four ml of blood was obtained from each volunteer; 10 ml of blood was obtained from each patient before the CPB, and another 10 ml was obtained after CPB. Heparin was neutralized using heparinase or protamine. Platelet reactivity was assessed by measuring the expression of P-selectin after stimulation of platelets with increasing concentrations of a thrombin receptor agonist peptide (TRAP). Data were analyzed using analysis of variance. P < 0.05 was considered significant. RESULTS: For the healthy volunteers, the activated coagulation times (ACTs) of the heparinized samples returned to baseline values with heparinase (12.5 U/ml) or protamine (32.5 microg/ml). For the 8 patients, the ACTs returned to baseline with heparinase (20 U/ml) or protamine (50 microg/ml). The authors found no difference in the expression of P-selectin in samples neutralized with heparinase, but samples neutralized with protamine showed a significant decrease in the expression of P-selectin when compared with heparinized samples. CONCLUSIONS: At dosages that reverse the anticoagulant effects of heparin, heparinase has minimal effects on platelets, whereas platelet reactivity was markedly inhibited by protamine.     

The significance of heparin concentration measurement during cardiopulmonary bypass--effect of heparin-coated circuit during normothermic bypass

Recently, use of heparin-coated circuits during normothermic cardiopulmonary bypass has become a trend in cardiovascular surgery. In light of this, heparin administration protocols during bypass should be reevaluated. In twenty patients who underwent cardiac surgery using a heparin-coated circuit under normothermia, heparin concentration was measured with Hepcon/HMS. Before initiating bypass, 300 IU/kg of heparin was administered with additional heparin to maintain activated clotting time (ACT) at more than 400 seconds. The heparin dose response (HDR) was measured before heparin administration. HDR is a heparin concentration calculated to correspond to an ACT of 480 seconds. As an index of heparin control during bypass, average heparin concentration/HDR (HC/HDR) was calculated. HC/HDR was correlated with Fibrinogen degradation products E (R = -0.52). D dimer (R = -0.45). Thrombin antithrombin complex (R = -0.54). Antithrombin III (R = 0.50) and platelet number (R = 0.44), but not with 24-hour postoperative blood loss. In conclusion, even when using a heparin-coated circuit plasma coagulation activity was not sufficiently suppressed by use of a conventional ACT monitoring protocol during normothermic bypass. Therefore, the maintenance of HC/HDR at a higher level may be indicated.     

r-Hirudin inhibits platelet-dependent thrombosis during cardiopulmonary bypass in baboons

BACKGROUND: Systemic anticoagulation is required during cardiopulmonary bypass (CPB) to inhibit the activation of platelets, the coagulation system and ultimately thrombus formation. Unfractionated heparin is most commonly used, but it is neither entirely safe nor completely effective. The use of protamine sulphate to reverse the anticoagulant effect further complicates the use of heparin. The clinical need for a heparin substitute is therefore obvious. We evaluated the efficacy of r-Hirudin, a potent and specific inhibitor of thrombin, as anticoagulant in a baboon model of cardiopulmonary bypass. METHODS: Ten baboons, divided into two groups of five each, were used. The one group received 0.7 mg/kg r-Hirudin as a bolus before CPB was started, followed by a constant infusion of 1.4 mg/kg/hr for the 90 min of CPB. The other group received a bolus of 2.5 mg/kg heparin before the start of CPB, followed by maintenance dosages to maintain the activated clotting time (ACT) >400 sec. RESULTS: Adequate anticoagulation was obtained with both anticoagulants. Haemodilution due to priming the extracorporeal system with Ringer's lactate and appropriately anticoagulated donor blood, was equivalent in both groups. During CPB with heparin, but not with hirudin, there was a significant increase in the number of circulating platelet aggregates, thrombin-antithrombin (TAT) complexes and 111In-labelled platelet accumulation in the oxygenator. After the initial decrease in platelet count due to haemodilution, it further decreased significantly during CPB with heparin but remained relatively constant when r-Hirudin was used. CONCLUSIONS: Our results strongly suggest that r-Hirudin is superior to heparin especially with respect to its inhibitory effect on platelet dependent thrombogenesis caused by the biomembranes of the oxygenator.     

A comparison between arterial- and venous-sampled activated clotting time measurements

In order to compare activated clotting time (ACT) sampled from an arterial (heparin-flushed) line with the control, a venous (heparin-free) line, arterial and venous ACT values were assessed before and after cardiopulmonary bypass in 150 patients while undergoing open-heart surgery. ACT was measured by Hemochron 801 automatic analyzer. Baseline arterial ACT was significantly higher than baseline venous ACT (14%; p < 0.001, using one-way analysis of variance and Bonferroni multiple comparisons test). The differences between the values of arterial and venous ACT after protamine reversal, between arterial ACT at baseline and after protamine reversal, and between venous ACT at baseline and after protamine reversal were not statistically significant. We conclude that arterial-sampled ACT measurement is suitable and reliable for monitoring heparin reversal by protamine after cardiopulmonary bypass.     

Release of proinflammatory cytokines during pediatric cardiopulmonary bypass: heparin-bonded versus nonbonded oxygenators

BACKGROUND: Heparin bonding of the cardiopulmonary bypass (CPB) circuit may be associated with a reduced inflammatory response and improved clinical outcome. The relative contribution of a heparin-bonded oxygenator (ie, >80% of circuit surface area) to these effects was assessed in a group of pediatric patients. METHODS: Twenty-one pediatric patients undergoing CPB operations were assigned randomly to receive either a heparin-bonded oxygenator (group H, n = 11) or a nonbonded oxygenator (group C, n = 10) in otherwise nonbonded circuits. The two groups were similar in pathology, age, weight, CPB time, and cross-clamp time. Plasma levels of the cytokines tumor necrosis factor-alpha, interleukin-6, and interleukin-8, as well as terminal complement complex, neutrophils, and elastase, were analyzed before, during, and after CPB. RESULTS: Significant levels of tumor necrosis factor-alpha were not detected in either group. Plasma levels of all other markers increased during and after CPB compared with baseline. Plasma levels of interleukin-6 peaked in both groups 2 hours after the administration of protamine but remained significantly higher in group C 24 hours after operation. Plasma concentrations of interleukin-8 peaked at similar levels in both groups 30 minutes after protamine administration and returned to baseline thereafter. Levels of terminal complement complex and elastase peaked in both groups 30 minutes after protamine administration. Plasma levels of terminal complement complex were significantly higher at the end of CPB and after protamine administration in group C. Elastase levels were significantly higher 2 and 24 hours after CPB in group C. The ventilation time of patients in group H was significantly lower than that of patients in group C: 10 (range, 3 to 24) versus 22 (range, 7 to 24) hours, respectively (p < 0.01). CONCLUSIONS: The present study confirms the proinflammatory nature of pediatric operations and demonstrates a lessened systemic inflammatory response with the use of heparin-bonded oxygenators. This is achieved without bonding of the entire circuit, which could have significant cost-benefit implications by negating the need for custom-built heparin-bonded circuitry.     

Influence of soft tissue on density and relative contrast between gutta-percha and dentin images. An in vitro study

Factor XII initiates the intrinsic coagulation cascade and may affect the fibrinolytic system. Routine coagulation tests used during cardiopulmonary bypass (CPB) are abnormal in factor-XII-deficient patients and are useless for monitoring anticoagulation in these patients. A factor-XII-deficient patient requiring CPB is described. The baseline celite activated clotting time (ACT) was greater than 1400 seconds and the thrombin time was 12.4 seconds (control, 11.9 seconds). Two units of plasma were given resulting in an ACT of 173 seconds. Following 300 units/kg of heparin and during CPB, the ACT ranged from 670-596 seconds with the thrombin time greater than 200 seconds. Plasma provides exogenous factor XII allowing an endpoint on the ACT test and may protect against possible postoperative hypofibrinolytic complications. A commercially available modified thrombin time may also be useful and provide an endpoint during high-dose heparinization.     

Cardiopulmonary bypass-induced changes in plasma concentrations of propofol and in auditory evoked potentials

Unbound, rather than total, plasma concentrations may be related to the anaesthetic action of propofol. Therefore, we measured plasma concentrations of propofol and recorded Nb wave latencies of auditory evoked potentials (AEP) during continuous infusion of propofol in 15 patients undergoing coronary artery bypass grafting (CABG) surgery. After induction of anaesthesia with fentanyl, propofol was infused continuously at a rate of 10 mg kg-1 h-1 for 20 min, and then the rate was reduced to 3 mg kg-1 h-1. Administration of heparin before cardiopulmonary bypass (CPB) did not affect total or unbound propofol concentration. Initiation of CPB decreased mean total propofol concentration from 2.6 to 1.7 micrograms ml-1 (P < 0.01). Simultaneously, mean unbound propofol concentration remained at 0.06 micrograms ml-1 because of a slight increase in the mean free fraction of plasma propofol (from 2.3 to 3.5%; P > 0.05). During hypothermic CPB, mean total propofol concentration increased to concentrations measured before bypass (to 2.1 micrograms ml-1; P > 0.05 vs value before CPB) and the mean unbound propofol concentration was at its highest (0.07 microgram ml-1; P < 0.05 vs value before heparin). After CPB and administration of protamine, the mean total propofol concentration remained lowered (1.7 micrograms ml-1; P < 0.05 vs value before heparin) and the mean unbound propofol concentration returned to the level measured before heparin (P < 0.001 vs value during hypothermia). The latency of the Nb wave from recordings of AEP increased after induction of anaesthesia, reached its maximum during hypothermia and was prolonged during the subsequent phases of the study. The latency of the Nb wave did not correlate with total or unbound propofol concentration. We conclude that the changes in total and unbound concentrations of plasma propofol were not parallel in patients undergoing CABG. During CPB or at any other time during the CABG procedure, the unbound propofol concentration did not decrease and Nb wave latency was prolonged compared with baseline values measured after induction of anaesthesia before the start of CPB.     

Heparin coating reduces blood cell adhesion to arterial filters during coronary bypass: a clinical study

Deleterious effects of cardiopulmonary bypass (CPB) are partly sequelae of blood-foreign surface reactions. Coating the inner surfaces of CPB sets with heparin has been shown to decrease activation of humoral cascade systems. The aim of this study was to investigate whether the heparin-coated CPB sets influence adhesion of blood cells to surfaces of arterial filters during CPB. Thirty-one patients undergoing coronary artery bypass grafting were studied. In the control group (C) standard CPB sets and standard doses of heparin (300 IU/kg) were employed; in the HC (heparin-coated) group, heparin-coated CPB sets and reduced heparin doses (range, 150 to 225 IU/kg) were used. Two additional groups were also studied; group FC (coated filter), with standard CPB sets and heparin-coated arterial filters (heparin dose, 300 IU/kg), and group OC (uncoated filter), with heparin-coated CPB sets and standard arterial filters (heparin dose, 300 IU/kg). The inner surfaces of the arterial filters were examined after CPB with scanning electron microscopy. Scanning electron microscopy demonstrated almost clean surfaces in heparin-coated filters even when other parts of the circuit were uncoated. Using an arbitrary adhesion score, significant differences between the groups were noted in the adhesion grade; it was lowest in group HC (2.2 +/- 0.27 [mean +/- standard error of the mean]) versus group C (5.4 +/- 0.53; p < 0.001). In group FC it was marginally higher than in group HC but almost significantly lower than in group OC (2.6 +/- 0.68 versus 5.4 +/- 0.81; p = 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Yeast artificial chromosome cloning and chromosomal localization of the abundant odontogenic keratocyst protein elafin

Heparin has been shown to decrease total vascular resistance while protamine stimulates endothelium-dependent vasodilation. This study was undertaken to determine whether heparin and/or protamine could enhance endothelium-derived relaxing factor (EDRF), as determined by nitric oxide (NO) production. Porcine carotid artery endothelial cells (PAECs) were seeded on multiwell plates, grown to confluence, and exposed to heparin (1-20 U/ml) or protamine (50-200 microg/ml) for 24 hours. With the addition of the NO synthase inhibitor, N(G)-monomethyl-L-arginine (NMMA), to heparin and/or protamine, the medium samples were collected in one hour. In a parallel clinical study, plasma samples were collected from patients undergoing cardiopulmonary bypass (CPB). The NO production was measured as reflected by the formation of nitrite (NO2-) and nitrate (NO3-), the stable end-metabolites of NO. NO production by PAECs was significantly increased by heparin > or = 5 U/ml or protamine > or = 50 microg/ml in a concentration-dependent manner. The increase of NO production was prevented by the addition of NMMA. In CPB patients, plasma NO2-/NO3- concentration was significantly increased after heparin administration compared to the preoperative value, at which time the mean plasma heparin level was 4.9+/-0.5 U/ml. Following slow protamine infusion, there was no significant difference in plasma NO2-/NO3- concentration compared to preoperative value. In conclusion NO production increases following exposure of PAECs to heparin and/or protamine. In patients, NO concentration significantly increased after heparin administration by IV bolus, but not with a slow infusion of protamine after CPB.     

Induction of monocyte tissue factor procoagulant activity during coronary artery bypass surgery is reduced with heparin-coated extracorporeal circuit

The possible activation of monocytes to express tissue factor procoagulant activity (TF-PCA) during CPB (cardiopulmonary bypass) was investigated. 22 patients undergoing myocardial revascularization were randomly assigned to two groups. In group C, heparin-coated circuits (Duraflo II) and reduced systemic heparinization (ACT > 250s) were used. In group NC, non-coated circuits and standard heparin administration (ACT > 480s) were used. Adherent monocytes retrieved from the oxygenators immediately after bypass arrest showed a 2-3-fold increase in TF-PCA when compared to circulating cells pre-CPB (P < 0.01). When cell PCA was expressed as percent change from pre-CPB (baseline) values, circulating monocytes in group NC at CPB-arrest showed a 2-fold increase in PCA compared to group C (P < 0.05). Moreover, the percent increase in PCA of oxygenator-retrieved monocytes was 7-fold in group NC and 2-fold in group C (P < 0.008 and P < 0.004, respectively). Thus, heparin-coating of the extracorporeal circuit reduced induction of adherent cell TF-PCA by 70% (P < 0.05). Thus, monocyte TF-PCA may cause activation of the extrinsic coagulation pathway during CPB surgery. It is apparent that heparin-coating enhanced biocompatibility of extracorporeal circuits. Reduced systemic heparinization in group C proved to be safe. However, further reduction of heparin administration may not be advisable, since monocytes were still activated in the coated oxygenator.     

Evaluation of a new point-of-care test that measures PAF-mediated acceleration of coagulation in cardiac surgical patients

BACKGROUND: This study was designed to evaluate a new point-of-care test (HemoSTATUS) that assesses acceleration of kaolin-activated clotting time (ACT) by platelet activating factor (PAF) in patients undergoing cardiac surgery. Our specific objectives were to determine whether HemoSTATUS-derived measurements correlate with postoperative blood loss and identify patients at risk for excessive blood loss and to characterize the effect of desmopressin acetate (DDAVP) and/or platelet transfusion on these measurements. METHODS: Demographic, operative, blood loss and hematologic data were recorded in 150 patients. Two Hepcon instruments were used to analyze ACT values in the absence (channels 1 and 2: Ch1 and Ch2) and in the presence of increasing doses of PAF (1.25, 6.25, 12.5, and 150 nM) in channels 3-6 (Ch3-Ch6). Clot ratio (CR) values were calculated with the following formula for each respective PAF concentration: clot ratio = 1-(ACT/control ACT). These values also were expressed as percent of maximal (%M = clot ratio/0.51 x 100) using the mean CRCh6 (0.51) obtained in a reference population. RESULTS: When compared with baseline clot ratios before anesthetic induction, a marked reduction in clot ratios was observed in both Ch5 and Ch6 after protamine administration, despite average platelet counts greater than 100 K/microliter. There was a high degree of correlation between clot ratio values and postoperative blood loss (cumulative chest tube drainage in the first 4 postoperative hours) with higher concentrations of PAF: CRCh6 (r = -0.80), %M of CRCh6 (r = -0.82), CRCh5 (r = -0.70), and %M of CRCh5 (r = -0.85). A significant (P < 0.01) improvement in clot ratios was observed with time after arrival in the intensive care unit in both Ch5 and Ch6, particularly in patients receiving DDAVP and/or platelets. CONCLUSIONS: Activated clotting time-based clot ratio values correlate significantly with postoperative blood loss and detect recovery of PAF-accelerated coagulation after administration of DDAVP or platelet therapy. The HemoSTATUS assay may be useful in the identification of patients at risk for excessive blood loss and who could benefit from administration of DDAVP and/or platelet transfusion.     

Aprotinin prolongs activated and nonactivated whole blood clotting time and potentiates the effect of heparin in vitro

This study was designed to evaluate the effect of aprotinin on activated versus nonactivated whole blood clotting time using two different on-site methods and to quantify these anticoagulant properties when compared to heparin in a controlled, in vitro environment. Blood specimens were obtained prior to heparin administration from 56 patients undergoing cardiac surgery. Specimens obtained from the first consecutive 20 patients were mixed with either normal saline (NS) or aprotinin (400 kallikrein inhibiting units (KIU)/mL), inserted into Hemochron tubes containing either NS or heparin (0.3 or 0.6 U/mL) and then used to measure celite-activated (celite ACT) and nonactivated whole blood clotting time (WBCT1) using four Hemochron instruments. Accordingly, specimens obtained from the second consecutive 20 patients were mixed with either NS or aprotinin, inserted into Automated Clot Timer cartridges containing either NS or heparin (0.06, 0.13, or 0.25 U/mL) and then used to measure kaolin-activated (kaolin ACT) or nonactivated whole blood clotting times (WBCT2) using four Automated Clot Timer instruments. Specimens obtained from the last 16 patients were mixed with either incrementally larger doses of aprotinin (0, 100, 200, 300, or 400 KIU/mL) or heparin (0, 0.12, 0.24, 0.36, 0.48, or 0.72 U/mL) and were then used for measurement of whole blood clotting time (WBCT2) using six Automated Clot Timer instruments. Aprotinin significantly prolonged activated or nonactivated whole blood clotting time and potentiated the prolongation of whole blood clotting time by heparin. The linear relationship between whole blood clotting time and either heparin concentration (WBCT2 = H x 357 + 280, mean adjusted r2 = 0.88) or aprotinin concentration (WBCT2 = A x 0.97 + 300, mean adjusted r2 = 0.94) was variable among patients. On average, 200 KIU/mL of aprotinin prolonged WBCT2 to the same extent as 0.69 +/- 0.28 U/mL of heparin using linear regression models within each patient. Aprotinin significantly prolongs activated or nonactivated whole blood clotting time measurements in a dose-dependent manner. Since prolongation of whole blood clotting time by heparin is potentiated by aprotinin in vitro, aprotinin's anticoagulant properties may in part account for the prolonged celite activated clotting time values observed in the presence of aprotinin.     

Inflammatory response to cardiopulmonary bypass using two different types of heparin-coated extracorporeal circuits

Previous reports have highlighted the disparity in biocompatibility of two differently engineered heparin coatings during the cardiopulmonary bypass (CPB) procedure. The aim of this prospective study was to evaluate the impact of the difference in haemocompatibility provided by either the Duraflo II equipment or the Carmeda equipment in the terminal inflammatory response observed after coronary artery surgery. Thirty patients were randomly allocated to two groups to be operated on using either Duraflo II equipment (group I) or Carmeda equipment (group 2) for extracorporeal circulation (ECC). Initial inflammatory response was assessed by terminal complement complex activation (SC5b-9). The late inflammatory response observed in the postoperative period was assessed by measuring cytokine production (tumour factor necrosis (TNF alpha), interleukin IL-6, interleukin IL-8) and circulating concentrations of adhesion molecules (ELAM-1, ICAM-1). The release of SC5b-9 after CPB and after protamine administration was lower in group 2 than in group 1 (p = 0.0002 and p = 0.006, respectively). A significant production of cytokines was detected in both groups with peak values observed within the time range of 4-6 h after the start of CPB.     

Influences of cardiopulmonary bypass and fentanyl anesthesia on hepatic circulation and oxygen metabolism in beagles

Decreases in hepatic blood flow (HBF) have been reported in patients and in animal experiments during cardiopulmonary bypass (CPB). We examined changes in HBF and hepatic oxygen metabolism during CPB in 16 beagles anesthetized with fentanyl. Hepatic arterial blood flow (HABF) and portal venous blood flow (PVBF) were measured by using an electromagnetic flowmeter before and during normothermic and hypothermic CPB with 10 microg x kg(-1) x h(-1) (F-10 group; n = 8) or 50 microg x kg(-1) x h(-1) (F-50 group; n = 8) of fentanyl anesthesia. CPB was conducted with membrane oxygenation and a nonpulsatile pump flow of 2.4 L x m(-2) x min(-1). Hepatic oxygen delivery (HDO2) and consumption (HVO2) were calculated from HBF and oxygen content in arterial, portal venous, and hepatic venous blood. HABF did not change during normothermic CPB in the F-10 group, but it decreased significantly during hypothermic CPB in both groups, especially the F-50 group. During CPB, PVBF and total HBF decreased significantly in both groups-more so with the larger dose of fentanyl--whereas HDO2 decreased significantly because the arterial and portal venous blood oxygen levels decreased. The HVO2 was stable in the F-10 group but was significantly depressed during CPB in the F-50 group. Our results indicate that during hypothermic nonpulsatile CPB larger doses of fentanyl are associated with reduced HBF and impaired HDO2 and HVO2. Implications: Hepatic dysfunction after cardiopulmonary bypass (CPB) has been frequently reported and could be partly attributed to hepatic circulatory disturbance during CPB. We found that, in beagles, large doses of fentanyl were associated with greater decreases in hepatic blood flow and hepatic oxygen metabolism during hypothermic CPB than smaller doses of fentanyl.     

Surface plasmon resonance sensor for heparin measurements in blood plasma

Surface plasmon resonance (SPR) was used as an affinity biosensor to determine absolute heparin concentrations in human blood plasma samples. Protamine and polyethylene imine (PEI) were evaluated as heparin affinity surfaces. Heparin adsorption onto protamine in blood plasma was specific with a lowest detection limit of 0.2 U/ml and a linear window of 0.2-2 U/ml. Although heparin adsorption onto PEI in buffer solution had indicated superior sensitivity to that on protamine, in blood plasma it was not specific for heparin and adsorbed plasma species to a steady-state equilibrium. By reducing the incubation time and diluting the plasma samples with buffer to 50%, the non-specific adsorption of plasma could be controlled and a PEI pre-treated with blood plasma could be used successfully for heparin determination. Heparin adsorption in 50% plasma was linear between 0.05 and 1 U/ml so that heparin plasma levels of 0.1-2 U/ml could be determined within a relative error of 11% and an accuracy of 0.05 U/ml.