Rhabdomyolysis induced by epsilon-aminocaproic acid

Antifibrinolytic Therapy and Perioperative Considerations

Fibrinolysis is a physiologic component of hemostasis that functions to limit clot formation. However, after trauma or surgery, excessive fibrinolysis may contribute to coagulopathy, bleeding, and inflammatory responses. Antifibrinolytic agents are increasingly used to reduce bleeding, allogeneic blood administration, and adverse clinical outcomes. Tranexamic acid is the agent most extensively studied and used in most countries. This review will explore the role of fibrinolysis as a pathologic mechanism, review the different pharmacologic agents used to inhibit fibrinolysis, and focus on the role of tranexamic acid as a therapeutic agent to reduce bleeding in patients after surgery and trauma.

Adjuncts to Blood Component Therapies for the Treatment of Bleeding in the Intensive Care Unit

Patients who are critically ill following surgical or traumatic injury often present with coagulopathy as a component of the complex multisystem dysfunction that clinicians must rapidly diagnose and treat in the intensive care environment. Failure to recognize coagulopathy while volume resuscitation with crystalloid or colloid takes place, or an unbalanced transfusion strategy focused on packed red blood cell transfusion can all significantly worsen coagulopathy, leading to increased transfusion requirements and poor outcomes. Even an optimized transfusion strategy directed at correcting coagulopathy and maintaining clotting factor levels carries the risk of a number of transfusion reactions including transfusion-related acute lung injury, transfusion-related circulatory overload, anaphylaxis, and septic shock. A number of adjunctive strategies can be used either to augment a balanced transfusion approach or as alternatives to blood component therapy. Coupled with an appropriate and timely laboratory testing, this approach can quickly diagnose a patient's specific coagulopathy and work to correct it as quickly as possible, minimizing the requirement of blood transfusion and the pathophysiologic effects of excessive bleeding and fibrinolysis. We will review the literature supporting this approach and provide insight into how these approaches can be best used to care for bleeding patients in the intensive care unit. Finally, the increasing use of several novel oral anticoagulants, novel antiplatelet drugs, and low-molecular weight heparin to clinical practice has complicated the care of the coagulopathic patient when these drugs are involved. Many clinicians familiar with heparin and warfarin reversal are not familiar with the optimal way to reverse the action of these new drugs. Patients treated with these drugs for a wide variety of conditions including atrial fibrillation, stroke, coronary artery stent, deep venous thrombosis, and pulmonary embolism will present for emergency surgery and will require management of pharmacologically induced postoperative coagulopathy. We will discuss optimized strategies for reversal of these agents and strategies that are currently under development.

Comparison of ε-Aminocaproic Acid and Tranexamic Acid in Reducing Postoperative Transfusions in Total Hip Arthroplasty

BACKGROUND

Use of antifibrinolytic agents in total hip arthroplasty (THA) is well supported; however, most studies used tranexamic acid (TXA), whereas few used ε-aminocaproic acid (EACA), a similar antifibrinolytic. This study compares the efficacy and cost per surgery of intraoperative infusion of EACA and TXA in reducing postoperative blood transfusion rates in THA.

METHODS

Retrospective chart review of 1799 primary unilateral THA cases from April 2012 through December 2014 at 5 hospitals within our health care network.

RESULTS

In our cohort, 711 received EACA, 445 received TXA, and 643 (control group) received no antifibrinolytic. Both antifibrinolytic groups had significantly fewer patients receiving red blood cell (RBC) transfusions when compared with control group (EACA 6.8% [P < .0001], TXA 9.7% [P < .0001] vs control group 24.7%). Average number of RBC units per patient were similar for EACA and TXA (0.11 units/patient and 0.15 units/patient, respectively), and both were significantly lower than the control group (0.48 units/patient, P < .0001). No significant difference was noted in mean RBC units per patient and percentage of patients transfused between EACA and TXA groups (P = .144, P = .074). Logistic regression showed no difference between EACA and TXA when adjusting for age, gender, higher severity of illness levels, admission hemoglobin, performing surgeon, and hospital. Medication acquisition cost for EACA averaged $2.70 per surgery compared with TXA at $39.58 per surgery.

CONCLUSION

Intraoperative antifibrinolytic use significantly decreases need for postoperative blood transfusions. At our institution, EACA is comparable to TXA in THA for reducing transfusion rates while at a lower cost per surgery.

Antifibrinolytic therapy to reduce haemoptysis from any cause

BACKGROUND

Haemoptysis is a common pathology around the world, occurring with more frequency in low-income countries. It has different etiologies, many of which have infectious characteristics. Antifibrinolytic agents are commonly used to manage bleeding from different sources, but their usefulness in pulmonology is unclear.

OBJECTIVES

To evaluate the effectiveness and safety of antifibrinolytic agents in reducing the volume and duration of haemoptysis in adult and paediatric patients.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) and the Database of Abstracts of Reviews of Effects (DARE) in The Cochrane Library, EMBASE and LILACS for publications that describe randomized controlled trials (RCTs) of antifibrinolytic therapy in patients presenting with haemoptysis. We also performed an independent search in MEDLINE for relevant trials not yet included in CENTRAL or DARE. Searches are up to date to the 19th September 2016. We conducted electronic and manual searches of relevant national and international journals. We reviewed the reference lists of included studies to locate relevant randomized controlled trials (RCTs). An additional search was carried out to find unpublished RCTs.

SELECTION CRITERIA

We included RCTs designed to evaluate the effectiveness and safety of antifibrinolytic agents in reducing haemoptysis in adult and paediatric patients of both genders presenting with haemoptysis of any etiology and severity. The intervention of interest was the administration of antifibrinolytic agents compared with placebo or no treatment.

DATA COLLECTION AND ANALYSIS

All reviewers independently assessed methodological quality and extracted data tables pre-designed for this review.

MAIN RESULTS

The electronic literature search identified 1 original study that met the eligibility criteria. One unpublished study was also identified through manual searches. Therefore two randomized controlled trials met the inclusion criteria: Tscheikuna 2002 (via electronic searches) and Ruiz 1994 (via manual searches). Tscheikuna 2002, a double-blind RCT performed in Thailand, evaluated the effectiveness of tranexamic acid (TXA, an antifibrinolytic agent) administered orally in 46 hospital in- and outpatients with haemoptysis of various etiologies. Ruiz 1994, a double-blind RCT performed in Peru, evaluated the effectiveness of intravenous TXA in 24 hospitalised patients presenting with haemoptysis secondary to tuberculosis.Pooled together, results demonstrated a significant reduction in bleeding time between patients receiving TXA and patients receiving placebo with a weighted mean difference (WMD) of -19.47 (95% CI -26.90 to -12.03 hours), but with high heterogeneity (I² = 52%). TXA did not affect remission of haemoptysis evaluated at seven days after the start of treatment. Adverse effects caused by the drug's mechanism of action were not reported. There was no significant difference in the incidence of mild side effects between active and placebo groups (OR 3.13, 95% CI 0.80 to 12.24).

AUTHORS' CONCLUSIONS

There is insufficient evidence to judge whether antifibrinolytics should be used to treat haemoptysis from any cause, though limited evidence suggests they may reduce the duration of bleeding.

Antifibrinolytic therapy to reduce haemoptysis from any cause

BACKGROUND

Haemoptysis is a common pathology around the world, occurring with more frequency in low-income countries. It has different etiologies, many of which have infectious characteristics. Antifibrinolytic agents are commonly used to manage bleeding from different sources, but their usefulness in pulmonology is unclear.

OBJECTIVES

To evaluate the effectiveness and safety of antifibrinolytic agents in reducing the volume and duration of haemoptysis in adult and paediatric patients.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) and the Database of Abstracts of Reviews of Effects (DARE) in The Cochrane Library, EMBASE and LILACS for publications that describe randomized controlled trials (RCTs) of antifibrinolytic therapy in patients presenting with haemoptysis. We also performed an independent search in MEDLINE for relevant trials not yet included in CENTRAL or DARE.We conducted electronic and manual searches of relevant national and international journals.We reviewed the reference lists of included studies to locate relevant randomized controlled trials (RCTs). An additional search was carried out to find unpublished RCTs.

SELECTION CRITERIA

We included RCTs designed to evaluate the effectiveness and safety of antifibrinolytic agents in reducing haemoptysis in adult and paediatric patients of both genders presenting with haemoptysis of any etiology and severity. The intervention of interest was the administration of antifibrinolytic agents compared with placebo or no treatment.

DATA COLLECTION AND ANALYSIS

All reviewers independently assessed methodological quality and extracted data tables pre-designed for this review.

MAIN RESULTS

We found two randomized controlled trials which met the inclusion criteria: Tscheikuna 2002 (via electronic searches) and Ruiz 1994 (via manual searches). We did not exclude any of the relevant studies we found.Tscheikuna 2002, a double-blind RCT performed in Thailand, evaluated the effectiveness of tranexamic acid (TXA, an antifibrinolytic agent) administered orally in 46 hospital in- and outpatients with haemoptysis of various etiologies. Ruiz 1994, a double-blind RCT performed in Peru, evaluated the effectiveness of intravenous TXA in 24 hospitalised patients presenting with haemoptysis secondary to tuberculosis.Pooled together, results demonstrated a significant reduction in bleeding time between patients receiving TXA and patients receiving placebo with a weighted mean difference (WMD) of -19.47 (95% CI -26.90 to -12.03 hours), but with high heterogeneity (I² = 52%). TXA did not affect remission of haemoptysis evaluated at seven days after the start of treatment. Adverse effects caused by the drug's mechanism of action were not reported. There was no significant difference in the incidence of mild side effects between active and placebo groups (OR 3.13, 95% CI 0.80 to 12.24).

AUTHORS' CONCLUSIONS

There is insufficient evidence to judge whether antifibrinolytics should be used to treat haemoptysis from any cause, though limited evidence suggests they may reduce the duration of bleeding.

A substrate pharmacophore for the human organic cation/carnitine transporter identifies compounds associated with rhabdomyolysis

The human organic cation/carnitine transporter (hOCTN2) is a high affinity cation/carnitine transporter expressed widely in human tissues and is physiologically important for the homeostasis of L-carnitine. The objective of this study was to elucidate the substrate requirements of this transporter via computational modeling based on published in vitro data. Nine published substrates of hOCTN2 were used to create a common feature pharmacophore that was validated by mapping other known OCTN2 substrates. The pharmacophore was used to search a drug database and retrieved molecules that were then used as search queries in PubMed for instances of a side effect (rhabdomyolysis) associated with interference with L-carnitine transport. The substrate pharmacophore was composed of two hydrogen bond acceptors, a positive ionizable feature and ten excluded volumes. The substrate pharmacophore also mapped 6 out of 7 known substrate molecules used as a test set. After searching a database of ~800 known drugs, thirty drugs were predicted to map to the substrate pharmacophore with L-carnitine shape restriction. At least 16 of these molecules had case reports documenting an association with rhabdomyolysis and represent a set for prioritizing for future testing as OCTN2 substrates or inhibitors. This computational OCTN2 substrate pharmacophore derived from published data partially overlaps a previous OCTN2 inhibitor pharmacophore and is also able to select compounds that demonstrate rhabdomyolysis, further confirming the possible linkage between this side effect and hOCTN2.

Diagnosis and management of hereditary angioedema: an emergency medicine perspective

BACKGROUND

Hereditary angioedema (HAE) is a rare and often debilitating condition associated with substantial morbidity and mortality in the absence of appropriate intervention. An underlying deficiency in functional C1-inhibitor (C1-INH) protein induces a vulnerability to unchecked activation of the complement, contact, and coagulation/fibrinolytic systems. The clinical consequence is a pattern of recurring attacks of non-pitting, non-pruritic edema, the urgency of which varies by the affected site. Laryngeal edema can escalate rapidly to asphyxiation, and severe cases of abdominal swelling can lead to hypovolemic shock.

OBJECTIVES

This report reviews the emergency diagnosis and treatment of hereditary angioedema and the impact of recently introduced treatments on treatment in the United States.

DISCUSSION

Until recently, emergency physicians in the United States were hindered by the lack of rapidly effective treatment options for HAE attacks. In this article, general clinical and laboratory diagnostic procedures are reviewed against the backdrop of two case studies: one patient presenting with a known history of HAE and one with previously undiagnosed HAE. In many countries outside the United States, plasma-derived C1-INH concentrate has for decades been the first-line treatment for acute attacks. The end of 2009 ushered in a new era in the pharmacologic management of HAE attacks in the United States with the approval of two new treatment options for acute treatment: a plasma-derived C1-INH concentrate and a kallikrein inhibitor.

CONCLUSION

With access to targeted and effective treatments, emergency physicians are now better equipped for successful and rapid intervention in urgent HAE cases.

Conestat alfa for the treatment of angioedema attacks

Recently, multiple C1 inhibitor (C1-INH) replacement products have been approved for the treatment of hereditary angioedema (HAE). This review summarizes HAE and its current treatment modalities and focuses on findings from bench to bedside trials of a new C1-INH replacement, conestat alfa. Conestat alfa is unique among the other C1-INH replacement products because it is produced from transgenic rabbits rather than derived from human plasma donors, which can potentially allow an unlimited source of drug without any concern of infectious transmission. The clinical trial data generated to date indicate that conestat alfa is safe and effective for the treatment of acute HAE attacks.

Interstitial plasmin activity with epsilon aminocaproic acid: temporal and regional heterogeneity

BACKGROUND

Epsilon aminocaproic acid (EACA) is used in cardiac surgery to modulate plasmin activity (PLact). The present study developed a fluorogenic-microdialysis system to measure in vivo region specific temporal changes in PLact after EACA administration.

METHODS

Pigs (25 to 35 kg) received EACA (75 mg/kg, n = 7) or saline in which microdialysis probes were placed in the liver, myocardium, kidney, and quadricep muscle. The microdialysate contained a plasmin-specific fluorogenic peptide and fluorescence emission, which directly reflected PLact, determined at baseline, 30, 60, 90, and 120 minutes after EACA/vehicle infusion.

RESULTS

Epsilon aminocaproic acid caused significant decreases in liver and quadricep PLact at 60, 90, 120 minutes, and at 30, 60, and 120 minutes, respectively (p < 0.05). In contrast, EACA induced significant biphasic changes in heart and kidney PLact profiles with initial increases followed by decreases at 90 and 120 minutes (p < 0.05). The peak EACA interstitial concentrations for all compartments occurred at 30 minutes after infusion, and were fivefold higher in the renal compartment and fourfold higher in the myocardium, when compared with the liver or muscle (p < 0.05).

CONCLUSIONS

Using a large animal model and in vivo microdialysis measurements of plasmin activity, the unique findings from this study were twofold. First, EACA induced temporally distinct plasmin activity profiles within the plasma and interstitial compartments. Second, EACA caused region-specific changes in plasmin activity profiles. These temporal and regional heterogeneic effects of EACA may have important therapeutic considerations when managing fibrinolysis in the perioperative period.

Temporally and regionally disparate differences in plasmin activity by tranexamic acid

BACKGROUND

A major complication associated with cardiac surgery is excessive and prolonged bleeding in the perioperative period. Improving coagulation by inhibiting fibrinolysis, primarily through inhibition of plasmin activity (PLact) with antifibrinolytics such as tranexamic acid (TXA), has been a pharmacological mainstay in cardiac surgical patients. Despite its almost ubiquitous use, the temporal and regional modulation of PLact profiles by TXA remains unexplored. Accordingly, we developed a fluorogenic-microdialysis system to measure in vivo dynamic changes in PLact after TXA administration in a large animal model.

METHODS

Pigs (25-35 kg) were randomly assigned to receive TXA (30 mg/kg, diluted into 50 mL normal saline; n = 9) or vehicle (50 mL normal saline; n = 7). Microdialysis probes were placed in the liver, myocardium, kidney, and quadriceps muscle compartments. The microdialysate infusion contained a validated plasmin-specific fluorogenic peptide. The fluorescence emission (standard fluorogenic units [SFU]) of the interstitial fluid collected from the microdialysis probes, which directly reflects PLact, was determined at steady-state baseline and 30, 60, 90, and 120 min after TXA/vehicle infusion. Plasma PLact was determined at the same time points using the same fluorogenic substrate approach.

RESULTS

TXA reduced plasma PLact at 30 min after infusion by >110 SFU compared with vehicle values (P < 0.05). Specifically, there was a decrease in liver PLact at 90 and 120 min after TXA infusion of >150 SFU (P < 0.05) and 175 SFU (P < 0.05), respectively. The decrease in liver PLact occurred 60 min after the maximal decrease in plasma PLact. In contrast, kidney, heart, and quadriceps PLact transiently increased followed by an overall decrease at 120 min.

CONCLUSIONS

Using a large animal model and in vivo microdialysis measurements of PLact, the unique findings from this study were 2-fold. First, TXA induced temporally distinct PLact profiles within the plasma and selected interstitial compartments. Second, TXA caused region-specific changes in PLact profiles. These temporal and regional differences in the effects of TXA may have important therapeutic considerations when managing fibrinolysis in the perioperative period.

Current and emerging management options for hereditary angioedema in the US

Hereditary angioedema (HAE) is a rare disorder characterized by recurrent attacks of swelling that may involve multiple anatomical locations. In the majority of patients, it is caused by a functional or quantitative defect in the C1 inhibitor (C1-INH), which is an important regulator of the complement, fibrinolytic, kallikrein-kinin and coagulation systems. Standard treatments used for other types of angioedema are ineffective for HAE. Traditional therapies for HAE, including fresh frozen plasma, epsilon-aminocaproic acid and danazol, may be well tolerated and effective in some patients; however, there are limitations both in their safety and efficacy. Several novel therapies have completed phase III trials in the US, including: (i) plasma-derived C1-INH replacement therapies (Berinert P and Cinryze); (ii) a recombinant C1-INH replacement therapy (conestat alfa; Rhucin); (iii) a kallikrein inhibitor (ecallantide [DX-88]); and (iv) a bradykinin-2-receptor antagonist (icatibant). Both Berinert P and Cinryze are reported to have excellent efficacy and safety data from phase III trials. Currently, only Cinryze has been approved for prophylactic use in the US. US FDA approval for other novel agents to treat HAE and for the use of Cinryze in the treatment of acute attacks is pending.

A benefit-risk review of systemic haemostatic agents: part 1: in major surgery

Systemic haemostatic agents play an important role in the management of blood loss during major surgery where significant blood loss is likely and their use has increased in recent times as a consequence of demand for blood products outstripping supply and the risks associated with transfusions. Their main application is as prophylaxis to reduce bleeding in major surgery, including cardiac and orthopaedic surgery and orthotopic liver transplantation. Aprotinin has been the predominant agent used in this setting; of the other antifibrinolytic agents that have been studied, tranexamic acid is the most effective and epsilon-aminocaproic acid may also have a role. Eptacog alfa (recombinant factor VIIa) has also shown promise. Tranexamic acid, epsilon-aminocaproic acid and eptacog alfa are generally well tolerated; however, when considering the methods to reduce or prevent blood loss intra- and postoperatively, the benefits of these agents need to be weighed against the risk of adverse events. Recently, concerns have been raised about the safety of aprotinin after an association between increased renal dysfunction and mortality was shown in retrospective observational studies and an increase in all-cause mortality with aprotinin relative to tranexamic acid or epsilon-aminocaproic acid was seen after a pre-planned periodic analysis of the large BART (Blood conservation using Antifibrinolytics in a Randomized Trial) study. The latter finding resulted in the trial being halted, and aprotinin has subsequently been withdrawn from the market pending detailed analysis of efficacy and safety results from the study. Part 1 of this benefit-risk review examines the efficacy and adverse effect profiles of systemic haemostatic agents commonly used in surgery, and provides individual benefit-risk profiles that may assist clinicians in selecting appropriate pharmacological therapy in this setting.

Epsilon aminocaproic acid reduces transfusion requirements in patients with thrombocytopenic hemorrhage

BACKGROUND

Epsilon aminocaproic acid (EACA) is an antifibrinolytic drug that has been used to control hemorrhage by stabilizing the thrombus. It has been used in thrombocytopenic patients largely on an empiric basis.

METHODS

Concerns regarding side effects have limited the use of this drug. The authors reviewed their experience with EACA at the Cleveland Clinic Foundation from 1997 to 2003.

RESULTS

Of 77 patients with thrombocytopenic hemorrhage, 51 (66%) patients achieved a complete response and 13 (17%) patients achieved a partial response, resulting in a decrease in platelet and red blood cell transfusions. Adverse effects were manageable in this set of patients with severe underlying disease.

CONCLUSIONS

Based on this experience, EACA may be a valuable adjunctive therapy in the treatment of patients with thrombocytopenic hemorrhage.

Antifibrinolytics in orthotopic liver transplantation: current status and controversies

This article reviews the current status and controversies of the 3 commonly used antifibrinolytics-epsilon-aminocaproic acid, tranexamic acid and aprotinin-during liver transplantation. There is no general consensus on how, when or which antifibrinolytics should be used in liver transplantation. Although these drugs appear to reduce blood loss and decrease transfusion requirements during liver transplantation, their use is not supported uniformly in clinical trials. Aprotinin has been studied more extensively in clinical trials and appear to offer more advantages compared to two other antifibrinolytics. Because of the diverse population of liver transplant recipients and the potential adverse effects of antifibrinolytics, especially life-threatening thromboembolism, careful patient selection and close monitoring is prudent. Further studies addressing the risks and benefits of antifibrinolytics in the setting of liver transplantation are warranted.

Perioperative systemic haemostatic agents

Skilful surgery combined with blood-saving methods and careful management of blood coagulation will all help reduce unnecessary blood loss and transfusion requirements. Excessive surgical bleeding causes hypovolaemia, haemodynamic instability, anaemia and reduced oxygen delivery to tissues, with a subsequent increase in postoperative morbidity and mortality. The role of anaesthetists in managing surgical blood loss has increased greatly in the last decade. Position of the patient during surgery and the provision of a hypotensive anaesthetic regimen were once considered the most important contributions of the anaesthetist to decreasing blood loss. Now, several pharmacological haemostatic agents are being used by anaesthetists as blood-saving agents. After a brief discussion of the physiology of haemostasis, this article will review the evidence for the role of such agents in reducing perioperative blood loss and transfusion requirements.

The fibrinolytic system attenuates vascular tone: effects of tissue plasminogen activator (tPA) and aminocaproic acid on renal microcirculation

1. The renal medulla is a major source of plasminogen activators (PA), recently shown to induce vasodilation in vitro. Treatment with PA inhibitors has been associated with renal dysfunction, suggesting compromised renal microvasculature. We investigated the impact of the PA inhibitor epsilon amino-caproic acid (EACA) upon vascular tone in vitro, and studied the effect of both tPA and EACA upon intrarenal hemodynamics in vivo. 2. In vitro experiments were carried out in isolated aortic rings and with cultured vascular smooth muscle cells. Studies of renal microcirculation and morphology were conducted in anesthetized Sprague-Dawley rats. 3. In isolated aortic rings, EACA (but not the other inhibitors of the fibrinolytic system PAI-1 or alpha-2 antiplasmin) reduced the half-maximal effective concentration of phenylephrine (PE) required to induce contraction (from 32 nm in control solution to 2 and 0.1 nm at EACA concentrations of 1 and 10 microm, respectively). Using reteplase (retavase) in the same model, we also provide evidence that the vasoactivity of tPA is in part kringle-dependent. In cultured vascular smooth muscle cells, Ca(2+) internalization following PE was enhanced by EACA, and retarded by tPA. 4. In anesthetized rats, EACA (150 mg x kg(-1)) did not affect systemic blood pressure, total renal or cortical blood flow. However, the outer medullary blood flow declined 12+/-2% below the baseline (P<0.03). By contrast, tPA (2 mg x kg(-1)), transiently increased outer medullary blood flow by 8+/-5% (P<0.02). Fibrin microthrombi were not found within the renal microvasculature in EACA-treated animals. 5. In conclusion, both fibrinolytic and antifibrinolytic agents modulate medullary renal blood flow with reciprocal effects of vasodilation (PA) and vasoconstriction (EACA). In vitro studies suggest that these hemodynamic responses are related to direct modulation of the vascular tone.

Iatrogenic and toxic myopathies

There has been increasing awareness of the adverse effects of therapeutic agents and exogenous toxins on the structure and function of muscle. The resulting clinical syndrome varies from one characterized by muscle pain to profound myalgia, paralysis, and myoglobinuria. Because toxic myopathies are potentially reversible, their prompt recognition may reduce their damaging effects or prevent a fatal outcome. Interest in the toxic myopathies, however, derives not only from their clinical importance but also from the fact that they serve as useful experimental models in muscle research. Morphological and biochemical studies have increased our understanding of the basic cellular mechanisms of myotoxicity. Toxins may produce, for instance, necrotizing, lysosomal-related, inflammatory, anti-microtubular, mitochondrial, hypokalemia-related, or protein synthesis-related muscle damage.

Transfusion-sparing hemostatic agents

A variety of agents are available to improve hemostasis and reduce blood loss in multiple clinical settings. These agents are most commonly used to reduce bleeding when an underlying hemostatic defect is present. Some new agents offer the potential to decrease blood loss even in the absence of an obvious underlying hemostatic defect. The authors discuss the use of a variety of products to reduce bleeding and minimize transfusion of blood products in the setting of clotting factor deficiency or inhibition, platelet deficiency and/or dysfunction, increased fibrinolysis, therapeutic anticoagulation, and coagulopathies caused by dilution and consumption in the setting of trauma and surgery. The authors primarily focus on the available pharmaceuticals.

Safety and efficacy of methods for reducing perioperative allogeneic transfusion: a critical review of the literature

A number of pharmacologic and nonpharmacologic technologies are in current use to minimize perioperative homologous blood use. Clinical trials, many of them randomized controlled trials, have been done evaluating these approaches and have demonstrated their efficacy. However, data on safety has relied mostly on case reports, uncontrolled studies, and, for the pharmacologic agents, extrapolation from the nonsurgical setting. In this review I analyze the data from the randomized trials and the lower-level evidence studies to provide the best estimates in safety with these alternatives. In general, these alternatives are safe with proper dosing and monitoring of effects. With aprotinin, the primary concern is anaphylaxis, and this predominantly with re-exposure. With aprotinin and with the anti-fibrinolytics, increased venous thromboembolic risk has not been a consistent finding. Tranexamic acid use intraoperatively is advantageous, but postoperative use appears to have no advantage and may be associated with renal dysfunction. DDAVP is low-risk, provided it is not overused, which can induce hyponatremia. Autologous predonation probably has similar risks as homologous blood with respect to transfusion errors and bacterial infection. As with most medical interventions, we must be vigilant to prevent human error.

Myoglobinuria

Myoglobinuria refers to an abnormal pathologic state in which an excessive amount of myoglobin is found in the urine, imparting a cola-like hue, usually in association with myonecrosis and a clinical picture of weakness, myalgias, and edema. Myoglobinuria is produced by multiple causes: any condition that accelerates the use or interferes with the availability of oxygen or energy substrates to muscle cells can result in myoglobinuria, as can events that produce direct muscle injury, either mechanical or chemical. Acute renal failure is the most serious complication, which can be prevented by prompt, aggressive treatment. In patients surviving acute attacks, recovery of muscle and renal function is usually complete.