What's fishy about protamine? Clinical use, adverse reactions, and potential alternatives.

Protamine, a highly basic protein isolated from salmon sperm, is the only clinically available agent to reverse the anticoagulation of unfractionated heparin. Following intravenous administration, protamine binds to heparin in a nonspecific electrostatic interaction to reverse its anticoagulant effects. In clinical use, protamine is routinely administered to reverse high-dose heparin anticoagulation in cardiovascular procedures, including cardiac surgery with cardiopulmonary bypass. Despite the lack of supportive evidence regarding protamine's effectiveness to reverse low-molecular-weight heparin, it is recommended in guidelines with low-quality evidence. Different dosing strategies have been reported for reversing heparin in cardiac surgical patients based on empiric dosing, pharmacokinetics, or point-of-care measurements of heparin levels. Protamine administration is associated with a spectrum of adverse reactions that range from vasodilation to life-threatening cardiopulmonary dysfunction and shock. The life-threatening responses appear to be hypersensitivity reactions due to immunoglobulin E and/or immunoglobulin G antibodies. However, protamine and heparin-protamine complexes can activate complement inflammatory pathways and inhibit other coagulation factors. Although alternative agents for reversing heparin are not currently available for clinical use, additional research continues evaluating novel therapeutic approaches.

Protamine-Induced Coronary Graft Thrombosis: A Review.

Perioperative myocardial infarction is a serious complication affecting a significant portion of patients undergoing coronary artery bypass graft surgery. This may arise due to coronary graft thrombosis, a rare but potentially fatal phenomenon associated with both congenital and acquired risk factors. Multiple case reports implicate the role of protamine in the development of such thromboses. The role of protamine in facilitating the regulation of hemostasis by reversing the anticoagulant effects of heparin in patients undergoing cardiopulmonary bypass is well-recognized. However, discussion of its potential contribution to coronary graft thrombosis and mechanisms by which this may occur is lacking. Furthermore, its narrow therapeutic index and side effect profile are such that its appropriateness as a universal reversal agent to heparin requires reconsideration. This article reviews the current body of evidence regarding the use of protamine in cardiac surgery and the limited case reports pertaining to its potential role in the pathophysiology of coronary graft thrombosis.

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.

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.

Protamine Induced Anaphylactic Shock after Peripheral Vascular Surgery.

Anaphylactic reactions to protamine are quite rare and almost exclusively reported during cardiac surgery. In this report, we illustrate a rare case of protamine reaction after peripheral vascular surgery a couple of months after cardiac surgery and how the patient survived this critical complication.

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.

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.

Protamine use in transcarotid artery revascularization is associated with lower risk of bleeding complications without higher risk of thromboembolic events.

OBJECTIVE: Recent studies have found that transcarotid artery revascularization (TCAR) is associated with lower risk of stroke or death compared with transfemoral carotid artery stenting but higher risk of bleeding complications, presumably associated with the need for an incision. Heparin anticoagulation is universally used during TCAR, so protamine use may reduce bleeding complications. However, the safety and effectiveness of protamine use in TCAR are unknown. We therefore evaluated the impact of protamine use on perioperative outcomes after TCAR in the Vascular Quality Initiative TCAR Surveillance Project. METHODS: We performed a retrospective review of patients undergoing TCAR in the Vascular Quality Initiative TCAR Surveillance Project from September 2016 to April 2019. We assessed in-hospital outcomes using propensity score-matched cohorts of patients who did and did not receive protamine. The primary efficacy end point was access site bleeding complications, and the primary safety end point was in-hospital stroke or death. Secondary end points included the individual end points of stroke, death, transient ischemic attack, myocardial infarction, congestive heart failure exacerbation, and hemodynamic instability. RESULTS: Of the 5144 patients undergoing TCAR, all patients received heparin and 4072 (79%) patients received protamine. We identified 944 matched pairs of patients who did and did not receive protamine. Protamine use was associated with a significantly lower risk of bleeding complications (2.8% vs 8.3%; relative risk [RR], 0.33; 95% confidence interval [CI], 0.21-0.52; P < .001), including bleeding that resulted in interventional treatment (1.0% vs 3.6%; RR, 0.26; 95% CI, 0.13-0.54; P < .001) and in blood transfusion (1.2% vs 3.9%; RR, 0.30; 95% CI, 0.15-0.58; P <.001). There were no statistically significant differences in in-hospital stroke or death for patients who received protamine and those who did not (1.6% vs 2.2%; RR, 0.71; 95% CI, 0.37-1.39; P = .32); however, there was a trend toward lower risk of stroke for patients who received protamine (1.1% vs 2.0%; RR, 0.53; 95% CI, 0.24-1.13; P = .09). There were also no statistically significant differences in the rates of transient ischemic attack (0.4% vs 1.1%; RR, 0.40; 95% CI, 0.13-1.28; P = .11), myocardial infarction (0.4% vs 0.8%; RR, 0.50; 95% CI, 0.15-1.66; P = .25), heart failure exacerbation (0.4% vs 0.3%; RR, 1.33; 95% CI, 0.30-5.96; P = .71), or postoperative hypotensive hemodynamic instability (16% vs 15%; RR, 1.06; 95% CI, 0.83-1.35; P = .50) with protamine use. CONCLUSIONS: Protamine can be safely used in TCAR to reduce the risk of perioperative bleeding complications without increasing the risk of thrombotic events.

Heparin reversal with protamine sulfate is not required in atrial fibrillation ablation with suture hemostasis.

BACKGROUND: The utility of protamine sulfate for heparin reversal in catheter-based atrial fibrillation (AF) ablation is unclear when using the suture closure technique for vascular hemostasis. OBJECTIVE: This study sought to address if protamine sulfate use for heparin reversal reduces vascular access complications in AF catheter ablation when suture techniques are used for postprocedural vascular hemostasis. METHODS: This is a retrospective multicenter observational study of 294 consecutive patients who underwent catheter ablation for AF with subsequent vascular access hemostasis by means of a figure-of-eight suture or stopcock technique. A total of 156 patients received protamine for heparin reversal before sheath removal while 138 patients did not receive protamine. The two groups were compared for procedural activated clotting time (ACT), access site complications, and duration of hospital stay. RESULTS: Baseline demographic characteristics were comparable in both groups. Despite higher ACT before venous sheath removal in patients not receiving protamine (288.0 ± 44.3 vs 153.9 ± 32.0 seconds; P < .001), there was no significant difference in groin complications, postoperative thromboembolic events, or duration of hospital stay between the two groups. Suture failure requiring manual compression was rarely observed in this cohort (0.34%). CONCLUSION: With modern vascular access and sheath management techniques, for patients undergoing catheter ablation for AF, simple suture closure techniques can obviate the need for protamine administration to safely achieve hemostasis after removal of vascular sheaths.

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.

Thrombolysis Following Heparin Reversal With Protamine Sulfate in Acute Ischemic Stroke: Case Series and Literature Review.

INTRODUCTION: Administering intravenous IV tissue plasminogen activator (tPA) is the recommended standard of care in acute ischemic stroke (AIS), although it is not recommended to administer intravenous thrombolysis with tPA following heparin reversal with protamine sulfate in patients with AIS. METHODS: We describe a case series of three patients and the most comprehensive literature review published to date in this specific subset of AIS patients undergoing thrombolysis following heparin reversal with protamine sulfate. The literature review was based on a scoping review methodology performed on four databases; PubMed, CINAHL, Web of Science, and Cochrane Library. All sources were searched from the inauguration of the database until February 2019. A total of six articles involving eight patients were identified. RESULTS: The primary safety outcome of no symptomatic intracranial hemorrhage (sICH) was met in all eleven patients, although only seven cases had a good functional outcome at 3 months. CONCLUSIONS: In appropriately selected AIS patients, coagulopathy correction appears to be safe from an sICH standpoint and may be beneficial. However, given the potential for bias with observational databases, case reports and case series, extreme caution is warranted in applying these results to routine clinical practice.

Cardiac arrest following protamine administration: a case series.

AIMS: Protamine sulfate is commonly used to reverse the action of heparin after catheter ablation procedures. Serious protamine-related adverse effect is rare, but its recognition and appropriate management by electrophysiologists and intensivists is important. Direct ventricular fibrillation (VF) soon after a slow infusion of protamine has not been clearly described. METHODS AND RESULTS: We examined the records of all patients who suffered apparent adverse events after protamine administration in our electrophysiology lab from 2013 to 2018. We describe a series of three patients, all of whom suffered a precipitous fall in arterial pressure followed by VF within minutes after administration of protamine following ablation for atrial fibrillation. The same supplier of protamine was used in all three cases, but they were from different batches. Serum tryptase levels were measured in all cases, immediately post-cardiac arrest and at 2- and 6-h post-event. Immunoglobulin levels were not measured. Two patients recovered after aggressive supportive therapy; the third died despite similar support. CONCLUSION: We have encountered three cases of profound hypotension followed by VF soon after administration of protamine. Although protamine is safe in a large majority of patients, these adverse events have led our centre to exercise greater selectivity and caution in its use.

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.

Extracorporeal immunoadsorption in heparin- and protamine-induced thrombocytopaenia prior to cardiac surgery.

Exposure to heparin and protamine during cardiac surgery on cardiopulmonary bypass (CPB) may trigger heparin-induced thrombocytopaenia and/or protamine-induced thrombocytopaenia. Further surgery on CPB with heparin and protamine in the presence of these antibodies implies increased thromboembolic risk. We present the successful application of extracorporeal immunoadsorption to deplete antibodies causing heparin-induced and protamine-induced thrombocytopaenia preoperatively.

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.