Optimal protamine dosing after cardiopulmonary bypass: The PRODOSE adaptive randomised controlled trial.

BACKGROUND: The dose of protamine required following cardiopulmonary bypass (CPB) is often determined by the dose of heparin required pre-CPB, expressed as a fixed ratio. Dosing based on mathematical models of heparin clearance is postulated to improve protamine dosing precision and coagulation. We hypothesised that protamine dosing based on a 2-compartment model would improve thromboelastography (TEG) parameters and reduce the dose of protamine administered, relative to a fixed ratio. METHODS AND FINDINGS: We undertook a 2-stage, adaptive randomised controlled trial, allocating 228 participants to receive protamine dosed according to a mathematical model of heparin clearance or a fixed ratio of 1 mg of protamine for every 100 IU of heparin required to establish anticoagulation pre-CPB. A planned, blinded interim analysis was undertaken after the recruitment of 50% of the study cohort. Following this, the randomisation ratio was adapted from 1:1 to 1:1.33 to increase recruitment to the superior arm while maintaining study power. At the conclusion of trial recruitment, we had randomised 121 patients to the intervention arm and 107 patients to the control arm. The primary endpoint was kaolin TEG r-time measured 3 minutes after protamine administration at the end of CPB. Secondary endpoints included ratio of kaolin TEG r-time pre-CPB to the same metric following protamine administration, requirement for allogeneic red cell transfusion, intercostal catheter drainage at 4 hours postoperatively, and the requirement for reoperation due to bleeding. The trial was listed on a clinical trial registry (ClinicalTrials.gov Identifier: NCT03532594). Participants were recruited between April 2018 and August 2019. Those in the intervention/model group had a shorter mean kaolin r-time (6.58 [SD 2.50] vs. 8.08 [SD 3.98] minutes; p = 0.0016) post-CPB. The post-protamine thromboelastogram of the model group was closer to pre-CPB parameters (median pre-CPB to post-protamine kaolin r-time ratio 0.96 [IQR 0.78-1.14] vs. 0.75 [IQR 0.57-0.99]; p < 0.001). We found no evidence of a difference in median mediastinal/pleural drainage at 4 hours postoperatively (140 [IQR 75-245] vs. 135 [IQR 94-222] mL; p = 0.85) or requirement (as a binary outcome) for packed red blood cell transfusion at 24 hours postoperatively (19 [15.8%] vs. 14 [13.1%] p = 0.69). Those in the model group had a lower median protamine dose (180 [IQR 160-210] vs. 280 [IQR 250-300] mg; p < 0.001). Important limitations of this study include an unblinded design and lack of generalisability to certain populations deliberately excluded from the study (specifically children, patients with a total body weight >120 kg, and patients requiring therapeutic hypothermia to <28°C). CONCLUSIONS: Using a mathematical model to guide protamine dosing in patients following CPB improved TEG r-time and reduced the dose administered relative to a fixed ratio. No differences were detected in postoperative mediastinal/pleural drainage or red blood cell transfusion requirement in our cohort of low-risk patients. TRIAL REGISTRATION: ClinicalTrials.gov Unique identifier NCT03532594.

Large cardiac wall hematoma with rapid growth: a case report of a potentially catastrophic complication during cardiac surgery.

BACKGROUND: Rapid growth of cardiac wall hematoma is a rare but potentially fatal complication of cardiac surgery. However, its pathophysiology and optimal management remain undefined. CASE PRESENTATION: Here we present a rare case of a large cardiac wall hematoma in the right ventricle during a thoracic aortic and valvular surgery. The hematoma expanded rapidly with epicardial rupture during cardiopulmonary bypass. We could establish non-surgical hemostasis and prevent further expansion of hematoma by early weaning of the cardiopulmonary bypass, followed by the administration of protamine and manual compression by hemostatic agent application. His postoperative recovery was uneventful and upon computed tomography analysis, the hematoma was observed to have absorbed completely at 1 week postoperatively. The patient is doing well 1 year after the surgery without evidence of recurrent cardiac wall hematoma on follow-up computed tomography. CONCLUSIONS: Cardiovascular surgeons should bear in mind this potentially catastrophic complication during cardiac surgery. Because of the vulnerability of the cardiac wall at the area of the hematoma, we believe that a hemostatic approach without sutures may be effective for this lethal complication.

Andexanet Alfa, the Possible Alternative to Protamine for Reversal of Unfractionated Heparin.

The recent shortage of protamine prompted an investigation of alternatives for reversal of unfractionated heparin. Heparin is an anticoagulant utilized in the hospital setting. Available options for anticoagulation include direct oral anticoagulants, vitamin K antagonists, thrombin inhibitors, low-molecular-weight heparins, and heparin. Protamine is the approved reversal agent for heparin with few alternatives under investigation. Although andexanet was designed as an antidote for apixaban and rivaroxaban, in vitro studies show that in a dose-dependent technique, andexanet had near full reversal of heparin, reversed anti-factor Xa activity, and neutralized anticoagulant effects of activated partial thromboplastin time and thrombin time induced by heparin.

Safety and Efficacy of Protamine Administration for Prevention of Bleeding Complications in Patients Undergoing TAVR.

OBJECTIVES: The aim of this study was to evaluate whether protamine administration for heparin reversal after transcatheter aortic valve replacement (TAVR) reduces bleeding complications and affects patient outcomes. BACKGROUND: Occurrence of major bleeding complications in patients undergoing TAVR is associated with increased morbidity and mortality. METHODS: This study included 873 patients undergoing TAVR, of whom 677 received protamine for heparin reversal. Standard access management included the use of pre-closure devices, manual compression, and percutaneous transluminal angioplasty or implantation of a covered stent graft, if necessary. The study complied with Good Clinical Practice guidelines and was approved by the local ethics committee. Written informed consent was obtained from all patients. RESULTS: The primary endpoint, a composite of 30-day all-cause mortality and life-threatening and major bleeding, occurred less frequently in the protamine administration group (3.2%) compared with the control group (8.7%) (p = 0.003). This was driven mainly by lower rates of life-threatening and major bleeding in the protamine group (0.1% vs. 2.6% [p < 0.001] and 1.0% vs. 4.1% [p = 0.008], respectively). Furthermore, protamine administration resulted in a significantly shorter hospital stay (11.1 ± 5.8 days vs. 12.7 ± 7.8 days; p = 0.05). In the overall cohort, stroke was observed in 1.9% and myocardial infarction in 0.2% of patients, with no significant difference between the groups (p > 0.05). Multivariate analysis revealed that only protamine administration (odds ratio: 0.24; 95% confidence interval: 0.10 to 0.58; p = 0.001) and acute kidney injury (odds ratio: 5.82; 95% confidence interval: 2.02 to 16.77; p = 0.001) were independently associated with the primary endpoint. CONCLUSIONS: Protamine administration resulted in significantly lower rates of life-threatening and major bleeding complications compared with patients without heparin reversal. Occurrence of stroke and myocardial infarction was not increased by protamine administration.

Verification of a thrombus induction method at the target point inside the blood pump using a fibrinogen coating for a thrombus detection study.

Although the magnetically levitated centrifugal blood pump (mag-lev pump) is considered superior to other pumps in antithrombogenicity, thrombotic complications are still reported. Research into thrombus detection inside a mag-lev pump is very important for solving this problem. Our research group has already proposed a method to detect a thrombus inside a mag-lev pump in real time without an additional sensor, which is named the impeller vibration method. To efficiently advance our research with reproducibility, a preconditioning method to induce thrombus inside the pump was thought to be necessary. Therefore, this study aimed to develop a preconditioning method that induces thrombus formation. To verify this method, in vitro experiments for thrombus detection were performed. A mag-lev pump developed at Tokyo Institute of Technology was used. A fibrinogen solution was coated on the inner surfaces of the bottom housing to induce thrombus formation at the target point inside the pump. The thrombus is detected by utilizing the phenomenon that the phase difference between the impeller displacement and input current to the magnetic bearing increases when a thrombus is formed inside a pump. Five hundred mL of porcine blood anticoagulated with heparin sodium was circulated in the mock circuit, and protamine sulfate was administered. Flow rate (1 L/min), impeller vibrational frequency (70 Hz), and vibrational amplitude (30 µm) were set to constant. The experiment was terminated when the phase difference increased by over 2° from the minimum value. The experiments were performed in fibrinogen-coated (group F, n = 5) and non-coated pumps (group N, n = 5). In group F, thrombus formation was observed at the fibrinogen-coated point of the housing. In contrast, a relatively small thrombus was observed in varying locations such as the housing or the impeller in group N. Thrombus formation time (the time from when the phase difference takes the minimum value to when the experiment is terminated) was different between the two groups. The mean time was significantly shorter in group F (44 ± 29 minutes) than in group N (143 ± 38 minutes; p = 0.0019). Therefore, a preconditioning method that induced thrombus formation at the target point inside a blood pump was successfully developed.

Protamine sulfate use during tibial bypass does not appear to increase thrombotic events or affect short-term graft patency.

OBJECTIVES: While the use of protamine sulfate as a heparin reversal agent has been extensively reviewed in patients undergoing carotid endarterectomy and coronary artery bypass grafting, there is a lack of literature on protamine's effects on lower extremity bypasses. The purpose of this study was to determine the risk of protamine sulfate dosing after tibial bypass on thrombotic or bleeding events, including early bypass failure. METHODS: We performed a retrospective review of our institutional database for patients undergoing primary distal peripheral bypass from January 2009 through December 2015 (contralateral bypass was considered to be a new primary bypass). Primary endpoints include composite thrombotic events (myocardial infarction, stroke, amputation at 30 days and patency less than 30 days) and composite bleeding events (bleeding or transfusion). RESULTS: A total of 152 tibial or peroneal bypasses in 136 patients with critical limb ischemia were identified. Of these, 78 (57.4%) patients received protamine sulfate intraoperatively and 58 (42.6%) did not. There were no differences in composite thrombotic or hemorrhagic outcomes. Protamine use had no effect on the rates of perioperative MI (9.0% versus 3.5%, p = 0.20), stroke (1.3% versus 1.7%, p = 0.83), or perioperative mortality (5.1% versus 3.5%, p = 0.64). There was no significant difference in composite post-operative bleeding events (20.7% versus 14.1%, p = 0.31) or composite thrombotic events (17.2% versus 18.0%, p = 0.91). Patients who received protamine undergoing bypass with non-autogenous conduit had significantly higher-recorded median operative blood loss (250 mL versus 150 mL, p = 0.0097) and median procedure lengths (265 min versus 201 min, p = 0.0229). No difference in 30-day amputation-free survival was noted (91.0% versus 91.4%, p = 0.94). Follow-up Kaplan-Meier estimation did not demonstrate a difference in 30-day patency (91.7% versus 88.5%, p = 0.52). CONCLUSIONS: Heparin reversal with protamine sulfate after tibial or peroneal bypass grafting is not associated with higher cardiovascular morbidity, bypass thrombosis, amputation, or mortality. Additionally, there was no statistically significant difference in post-operative bleeding or thrombosis complications for patients who did not receive protamine, although the findings are suggestive of a potential difference in a more adequately powered study. Our results suggest that protamine sulfate is safe for intraoperative use without increased risk of thrombotic complications or early tibial bypass graft failure.

The Inhibitory Effect of Protamine on Platelets is Attenuated by Heparin without Inducing Thrombocytopenia in Rodents.

Protamine sulfate (PS) is a polycationic protein drug obtained from the sperm of fish, and is used to reverse the anticoagulant effect of unfractionated heparin (UFH). However, the interactions between PS, UFH, and platelets are still not clear. We measured the platelet numbers and collagen-induced aggregation, P-selectin, platelet factor 4, ß-thromboglobulin, prostacyclin metabolite, D-dimers, activated partial thromboplastin time, prothrombin time, anti-factor Xa, fibrinogen, thrombus weight and megakaryocytopoiesis in blood collected from mice and rats in different time points.. All of the groups were treated intravenously with vehicle, UFH, PS, or UFH with PS. We found a short-term antiplatelet activity of PS in mice and rats, and long-term platelet-independent antithrombotic activity in rats with electrically-induced thrombosis. The antiplatelet and antithrombotic potential of PS may contribute to bleeding risk in PS-overdosed patients. The inhibitory effect of PS on the platelets was attenuated by UFH without inducing thrombocytopenia. Treatment with UFH and PS did not affect the formation, number, or activation of platelets, or the thrombosis development in rodents.

Activated platelet aggregation is transiently impaired also by a reduced dose of protamine.

Objectives: Protamine reduces platelet aggregation after cardiopulmonary bypass (CPB). We studied the inhibitory effect of a reduced protamine dose, the duration of impaired platelet function and the possible correlation to postoperative bleeding. Design: Platelet function was assessed by impedance aggregometry in 30 patients undergoing cardiac surgery with CPB at baseline, before protamine administration, after 70% and 100% of the calculated protamine dose, after 20 minutes and at arrival to the intensive care unit. Adenosine diphosphate (ADP), thrombin receptor activating peptide-6 (TRAP), arachidonic acid (AA) and collagen (COL) were used as activators. Blood loss was measured during operation and three hours after surgery. Results are presented as median (25th-75th percentile). Results: Platelet aggregation decreased markedly after the initial dose of protamine (70%) with all activators; ADP 89 (71-110) to 54 (35-78), TRAP 143 (116-167) to 109 (77-136), both p < .01; AA 25 (16-49) to 17 (12-24) and COL 92 (47-103) to 60 (38-81) U, both p < .05. No further decrease was seen after 100% protamine. The effect was transient and after twenty minutes platelet aggregation had started to recover; ADP 76 (54-106), TRAP 138 (95-158), AA 20 (10-35), COL 70 (51-93) U. Blood loss during operation correlated to aggregometry measured at baseline and after protaminization. Conclusions: Protamine after CPB induces a marked decrease in platelet aggregation already at a protamine-heparin ratio of 0.7:1. The impairment seems to be transient and recovery had started after 20 minutes.

Is 300 Seconds ACT Safe and Efficient during MiECC Procedures?

INTRODUCTION: The recommended minimum activated clotting time (ACT) level for cardiopulmonary bypass (CPB) of 480 seconds originated from investigations with bubble oxygenators and uncoated extracorporeal circulation (ECC) systems. Modern minimal invasive ECC (MiECC) systems are completely closed circuits containing a membrane oxygenator and a tip-to-tip surface coating. We hypothesized that surface coating and the "closed-loop" design allow the MiECC to safely run with lower ACT levels and that an ACT level of 300 seconds can be safely applied without thromboembolic complications. The aim of this study was to investigate the potential risks during application of reduced heparin levels in patients undergoing coronary surgery. METHODS: In this study, 68 patients undergoing coronary artery bypass grafting with MiECC were randomized to either the study group with an ACT target of 300 seconds or the control group with an ACT of 450 seconds. All other factors of MiECC remained unchanged. RESULTS: The study group received significantly less heparin and protamine (heparin [international units] median [min-max], Red_AC: 32,800 [23,000-51,500] vs. Full_AC: 50,000 [35,000-65,000] p < 0.001; protamine [international units], Red_AC: 18,000 [10,000-35,000] vs. Full_AC: 30,000 [20,000-45,000] p < 0.001). The ACT in the study group was significantly lower at the start of MiECC (mean ± standard deviation: study group 400 ± 112 vs. control group 633 ± 177; p < 0.0001). Before termination of CPB the ACT levels were: study group 344 ± 60 versus control group 506 ± 80. In both groups, the values of the endogenous thrombin potential (ETP) decreased simultaneously. None of the study participants experienced thromboembolic complications. CONCLUSION: Since no evidence of increased thrombin formation (ETP) was found from a laboratory standpoint, we concluded that the use of MiECC with a reduced anticoagulation strategy seems possible. This alternative anticoagulation strategy leads to significant reduction in dosages of both heparin and protamine. We can confidently move forward with investigating this anticoagulation concept. However, to establish clinical safety of ACT below 300 seconds, we need larger clinical studies.

Calculation Algorithm Reduces Protamine Doses Without Increasing Blood Loss or the Transfusion Rate in Cardiac Surgery: Results of a Randomized Controlled Trial.

OBJECTIVES: The aim of the study was to investigate whether the HeProCalc algorithm affects heparin and protamine dosage, postoperative blood loss, and transfusion rate. DESIGN: Randomized controlled trial. SETTING: University hospital. PARTICIPANTS: The study comprised 210 cardiac surgery patients undergoing cardiac surgery with cardiopulmonary bypass. Twenty patients were excluded because of re-exploration for localized surgical bleeding (n = 9), violation of protocol (n = 2), aprotinin use (n = 3 and nadir body temperature <32°C (n = 6). INTERVENTIONS: Study participants were randomly assigned to either traditional heparin and protamine dosage based on body weight only (control group) or dosage based on the HeProCalc algorithm (intervention group). MEASUREMENTS AND MAIN RESULTS: The initial median heparin dose was 32,500 IU (interquartile range [IQR] 30,000-35,000) in the intervention group compared with 35,000 IU (IQR 30,000-37,500) (p = 0.025) in the control group. The total heparin dose in the intervention group was 40,000 IU (IQR 32,500-47,500) compared with 42,500 IU (IQR 35,000-50,000) in the control group (p = 0.685). The total protamine dose was 210 mg (IQR 190-240) in the intervention group compared with 350 mg (IQR 300-380) (p < 0.001) in the control group. The ratio of total protamine to initial dose of heparin in the intervention group was 0.62 compared with 1.0 (p < 0.001). The amount of chest tube bleeding after 12 postoperative hours was 320 mL (IQR 250-460) in the intervention group compared with 350 mL (IQR 250-450) (p = 0.754) in the control group. Neither the transfusion rate nor postoperative blood loss differed significantly between the 2 groups. CONCLUSION: Use of the HeProCalc algorithm reduced protamine dosage and the protamine/heparin ratio after cardiopulmonary bypass compared with conventional dosage based on weight without significant effect on postoperative blood loss or the transfusion rate.

Low-dose compared to manufacturer-recommended dose four-factor prothrombin complex concentrate for acute warfarin reversal.

BACKGROUND: Four-factor PCC is the recommended standard of care for acute warfarin reversal but optimal dosing is unknown. We aim to show that a low-dose strategy is often adequate and may reduce the risk of thromboembolic events when compared to manufacturer-recommended dosing. METHODS: A weight-based dosing strategy of 15-25 units/kg was established as the institutional standard of care in May 2015. This retrospective, before-and-after cohort analysis included patients receiving 4F-PCC according to a manufacturer-recommended (n = 122) or a low-dose (n = 83) strategy. The primary efficacy outcome was a combination of INR reversal on first check and hemostatic efficacy at 24 h. RESULTS: Demographics, indications for warfarin, and presenting INR values were similar between the two groups. Patients in the manufacturer-recommended dose group received significantly more 4F-PCC than the low dose group (2110 units vs. 1530 units). More patients in the manufacturer-recommended dose group achieved the primary endpoint (75.4% vs. 61.4%), with more patients achieving the target INR on recheck in the manufacturer-recommended dose group (95.9% vs. 84.3%) and no difference in hemostatic efficacy between groups (79.5% vs. 74.7%). There was no difference in thromboembolic events at 72 h (4.1% vs. 1.2%) or at 30 days (8.2% vs. 4.8%). Significantly more patients in the manufacturer-recommended dose group died or were transferred to hospice care during hospitalization (21.3% vs. 9.6%). CONCLUSION: Utilization of a low-dose 4F-PCC strategy resulted in fewer patients achieving target INR reversal, but no difference in hemostatic efficacy, thromboembolic events, or survival.

First Reported Use of Team Cognitive Workload for Root Cause Analysis in Cardiac Surgery.

Cognitive workload data of members of the cardiac surgery team can be measured intraoperatively and stored for later analysis. We present a case of a near-miss (medication error) that underwent root cause analysis using workload data. Heart rate variability data, representing workload levels, were collected from the attending surgeon, attending anesthesiologist, and lead perfusionist using wireless heart rate monitors. An episode of cognitive overload of the anesthesiologist due to a distractor was associated with the preventable error. Additional studies are needed to better understand the role of psychophysiological data in enhancing surgical patient safety.

Sobredosis accidental de enoxaparina en un recién nacido / Enoxaparin overdose in a newborn

La enoxaparina es una heparina de bajo peso molecular utilizada en el período neonatal. Requiere menor monitoreo que la heparina estándar o no fraccionada, si bien es escaso el conocimiento actual acerca de su dosis y de los niveles terapéuticos en los neonatos. Además, existe una información muy limitada respecto del manejo de su sobredosificación en este grupo de edad. Se presenta el primer caso publicado en castellano de un neonato que recibió una dosis de enoxaparina diez veces superior a la terapéutica de forma accidental y en el que se administró una dosis aislada de protamina para revertir su efecto.

Enoxaparin is a low molecular weight heparin used in the neonatal period. It requires less monitoring than standard or unfractionated heparin, although current knowledge about its dose and therapeutic levels in neonates is scarce. In addition, there is very limited information about the management of overdose in this age group. We present the first case published in Spanish of a neonate who accidentally received a dose of enoxaparin ten times higher than the therapeutic one and an isolated dose of protamine to reverse its effect.

[Enoxaparin overdose in a newborn]. / Sobredosis accidental de enoxaparina en un recién nacido.

Enoxaparin is a low molecular weight heparin used in the neonatal period. It requires less monitoring than standard or unfractionated heparin, although current knowledge about its dose and therapeutic levels in neonates is scarce. In addition, there is very limited information about the management of overdose in this age group. We present the first case published in Spanish of a neonate who accidentally received a dose of enoxaparin ten times higher than the therapeutic one and an isolated dose of protamine to reverse its effect.

La enoxaparina es una heparina de bajo peso molecular utilizada en el período neonatal. Requiere menor monitoreo que la heparina estándar o no fraccionada, si bien es escaso el conocimiento actual acerca de su dosis y de los niveles terapéuticos en los neonatos. Además, existe una información muy limitada respecto del manejo de su sobredosificación en este grupo de edad. Se presenta el primer caso publicado en castellano de un neonato que recibió una dosis de enoxaparina diez veces superior a la terapéutica de forma accidental y en el que se administró una dosis aislada de protamina para revertir su efecto.

Heparin-protamine balance after neonatal cardiopulmonary bypass surgery.

Essentials Heparin-protamine balance (HPB) modulates bleeding after neonatal cardiopulmonary bypass (CPB). HPB was examined in 44 neonates undergoing CPB. Post-operative bleeding occurred in 36% and heparin rebound in 73%. Thrombin-initiated fibrin clot kinetic assay and partial thromboplastin time best assessed HPB. SUMMARY: Background Neonates undergoing cardiopulmonary bypass (CPB) are at risk of excessive bleeding. Blood is anticoagulated with heparin during CPB. Heparin activity is reversed with protamine at the end of CPB. Paradoxically, protamine also inhibits blood coagulation when it is dosed in excess of heparin. Objectives To evaluate heparin-protamine balance in neonates undergoing CPB by using research and clinical assays, and to determine its association with postoperative bleeding. Patients/Methods Neonates undergoing CPB in the first 30 days of life were studied. Blood samples were obtained during and after surgery. Heparin-protamine balance was assessed with calibrated automated thrombography, thrombin-initiated fibrin clot kinetic assay (TFCK), activated partial thromboplastin time (APTT), anti-FXa activity, and thromboelastometry. Excessive postoperative bleeding was determined by measurement of chest tube output or the development of cardiac tamponade. Results and Conclusions Of 44 neonates enrolled, 16 (36%) had excessive postoperative bleeding. The TFCK value was increased. By heparin in neonatal blood samples, but was only minimally altered by excess protamine. Therefore, it reliably measured heparin in samples containing a wide range of heparin and protamine concentrations. The APTT most closely correlated with TFCK results, whereas anti-FXa and thromboelastometry assays were less correlative. The TFCK and APTT assay also consistently detected postoperative heparin rebound, providing an important continued role for these long-established coagulation tests in the management of postoperative bleeding in neonates requiring cardiac surgical repair. None of the coagulation tests predicted the neonates who experienced postoperative bleeding, reflecting the multifactorial causes of bleeding in this population.

Use of epoprostenol to treat severe pulmonary vasoconstriction induced by protamine in cardiac surgery.

Since there were a few articles to report the treatment of severe pulmonary vasoconstriction induced by protamine in cardiac surgery, we described the use of epoprostenol to reverse this condition.A total of 5 cases of severe pulmonary vasoconstriction induced by protamine in cardiac surgery were reviewed. The demographic, clinical data and treatment process were obtained. All the patients were followed up.Severe pulmonary vasoconstriction was occurred 4 to 10 minutes after protamine infusion. The primary sign was sudden hypotension, the pulmonary artery pressure was increased gradually, the arterial oxygen partial pressure was decreased in all the patients. Epoprostenol was infused via pulmonary artery catheter at dosage of 20 to 40 ng/kg·min in all the patients, 2 patients were underwent re-cardiac pulmonary bypass assistance. The hemodynamic instability status lasted 40 to 65 minutes respectively. All the patients were recovered uneventfully.All physicians should alert to the incidence of severe pulmonary vasoconstriction induced by protamine in cardiac surgery. Use epoprostenol through pulmonary artery catheter could treat pulmonary artery vasoconstriction effectively and safely.