Thrombolysis medication errors: benefits of bolus thrombolytic agents

Rationale and methodology for a multicentre randomised trial of fibrinolysis for pulmonary embolism that includes quality of life outcomes

BACKGROUND

Submassive pulmonary embolism (PE) has a low mortality rate but can degrade functional capacity.

OBJECTIVE

The present study aims to provide rationale, methodology, and initial findings of a multicentre, randomised trial of fibrinolysis for PE that used a composite end-point, including quality of life measures.

METHODS

This investigator-initiated study was funded by a contract between a corporate partner and the investigator's hospital (the prime site). The investigator was the Food and Drug Administration (FDA) sponsor. The prime site subcontracted, indemnified, and trained consortia members. Consenting, normotensive patients with PE and right ventricular strain (by echocardiography or biomarkers) received low-molecular-weight heparin and random assignment to a single bolus of tenecteplase or placebo in double-blinded fashion. The outcomes were: (i) in-hospital rate of intubation, vasopressor support, and major haemorrhage, or (ii) at 90 days, death, recurrent PE, or composite that defined poor quality of life (echocardiography, 6 min walk test and surveys). The planned sample size was n = 200.

RESULTS

Eight sites enrolled 87 patients over 5 years. The ratio of patients screened for each enrolled was 7.4 to 1, equating to 11 h screening time per patient enrolled. Primary barrier to enrolment was the cost of screening. Two patients died (2.5%, 95%CI [0-8%]), one developed shock, but 18 (22%, 95%CI: [13-30%]) had a poor quality of life.

CONCLUSIONS

An investigator-initiated, FDA-regulated, multicentre trial of fibrinolysis for submassive PE was conducted, but was limited by screening costs and a low mortality rate. Quality of life measurements might represent a more important patient-centred end-point.

Excess heparin dosing among fibrinolytic-treated patients with ST-segment elevation myocardial infarction

BACKGROUND

Although the use of heparin with fibrinolytics is associated with more rapid ST-segment resolution and increased infarct-related artery patency among patients with ST-segment elevation myocardial infarction (STEMI), its associated increase in bleeding risk is well documented and might be augmented by excess heparin dosing.

METHODS

We sought to characterize the incidence and associated bleeding risk of excess heparin dosing among patients with STEMI treated with fibrinolysis who were enrolled in the Can Rapid Risk Stratification of Unstable Angina Patients Suppress Adverse Outcomes with Early Implementation of the American College of Cardiology/American Heart Association Guidelines initiative. Excess dosing was defined as a bolus more than 60 U/kg or an infusion more than 12 U/kg/h per American College of Cardiology/American Heart Association guidelines and was further stratified into major and mild excess (major defined as a bolus>70 U/kg or infusion >15 U/kg/h).

RESULTS

Among 964 fibrinolytic-treated patients with STEMI, 758 (79%) received adjunctive unfractionated heparin therapy. Of these, 368 patients (49%) received excess dosing of unfractionated heparin and 137 patients (18%) received major excess heparin dosing. Factors significantly associated with excess dosing included low body weight and female sex. Patients who received major excess dosing had higher unadjusted rates of major bleeding (19.2% vs 12.4%, P=.004) and transfusion (13.5% vs 4.7%, P=.0002) than patients without excess dosing. After adjustment, a trend persisted for the association with higher transfusion risk (odds ratio 1.39 [0.61-3.14]).

CONCLUSION

Approximately half of fibrinolytic-treated patients with STEMI in contemporary practice received an excess dose of unfractionated heparin. Careful attention to dosing is needed to limit the compounded bleeding risk when heparin is added to fibrinolytic therapy.

The role of fibrinolytics in the prehospital treatment of ST-elevation myocardial infarction (STEMI)

The efficacy of fibrinolytics in the treatment of ST-elevation myocardial infarction is directly related to the time of administration, with the first 2 h after symptom onset seen as a critical period for greatest improvement in cardiovascular parameters and mortality. The American College of Cardiology/American Heart Association recommends a medical contact to treatment time of 30 min for fibrinolysis in patients with ST-elevation myocardial infarction. In selected patients, reperfusion goals may be expedited with prehospital administration of fibrinolytics. In clinical trials, prehospital fibrinolysis markedly reduced the time from symptom onset to treatment, allowed earlier ST-segment resolution, and reduced short- and long-term mortality compared with in-hospital treatment. Prehospital fibrinolysis has become more feasible with the introduction of prehospital 12-lead electrocardiography, improved skills of emergency medical services personnel, improved communication with the Emergency Department, and the advent of bolus fibrinolysis. Rapid and accurate administration of a fibrinolytic is vital for the success of prehospital fibrinolysis.

Accelerated streptokinase in ST-elevation myocardial infarction — a romanian (ASK–ROMANIA) multicenter registry

BACKGROUND

The classical streptokinase regimen (1.5 M.U. over 60 min) may be too slow in patients with ST-elevation myocardial infarction (STEMI).

OBJECTIVE

To compare the efficacy and safety of four streptokinase regimens in STEMI patients.

METHODS

1880 consecutive patients admitted within 6 h of STEMI onset were allocated one of the following four streptokinase regimens: 1.5 M.U. over 60 min (n=517); 1.5 M.U./30 min (n=355); 1.5 M.U./20 min (n=507); 0.75 M.U./10 min, repeated or not after 50 min if no electrocardiographic criteria of reperfusion (n=501).

RESULTS

Rates of coronary reperfusion (non-invasively detected) for SK1.5/30 (72.39%), SK1.5/20 (75.34%) and SK0.75/10 (72.85%) were similar and higher than for SK1.5/60 (64.03%, p=0.019, p<0.0001, and p=0.006, respectively). In-hospital mortality was significantly lower for SK1.5/20 (7.10%) and SK0.75/10 (7.38%) and at the limit of significance for SK1.5/30 (7.60%) compared with SK1.5/60 (11.60%, p<0.0001, 0.006, and 0.053, respectively). Intracerebral haemorrhage and other major bleeding had similar incidence in the four groups.

CONCLUSIONS

Compared to the classical 1.5 M.U. over 60 min streptokinase regimen, significantly higher rates of coronary reperfusion and lower in-hospital mortality can be obtained by infusing the same dose over only 20 min, or either one or two half doses over only 10 min, without risk increase.

Reperfusion strategies in the emergency treatment of ST-segment elevation myocardial infarction

Prompt restoration of blood flow is the primary treatment goal in ST-segment elevation myocardial infarction to optimize clinical outcomes. The ED plays a critical role in rapid triage, diagnosis, and management of ST-elevation myocardial infarction, and in the decision about which of the 2 recommended reperfusion options, that is, pharmacologic and mechanical (catheter-based) strategies, to undertake. Guidelines recommend percutaneous coronary intervention (PCI) if the medical contact-to-balloon time can be kept under 90 minutes, and timely administration of fibrinolytics if greater than 90 minutes. Most US hospitals do not have PCI facilities, which means the decision becomes whether to treat with a fibrinolytic agent, transfer, or both, followed by PCI if needed. Whichever reperfusion approach is used, successful treatment depends on the ED having an integrated and efficient protocol that is followed with haste. Protocols should be regularly reviewed to accommodate changes in clinical practice arising from ongoing clinical trials.

Time to treatment and the impact of a physician on prehospital management of acute ST elevation myocardial infarction: insights from the ASSENT-3 PLUS trial

OBJECTIVES

To assess the impact of variation in prehospital care across distinct health care environments in ASSENT (assessment of the safety and efficacy of a new thrombolytic) -3 PLUS, a large (n = 1639) contemporary multicentred international trial of prehospital fibrinolysis. Specifically, the objectives were to assess predictors of time to treatment, whether components of time to treatment vary across countries, and the impact of physician presence before hospitalisation on time to treatment, adherence to protocol, and clinical events.

METHODS

Patient characteristics associated with early treatment (< or = 2 hours), comparison of international variation in time to treatment, and components of delay were assessed. Trial specific patient data were linked with site specific survey responses.

RESULTS

Younger age, slower heart rate, lower systolic blood pressure, and prior percutaneous coronary intervention were associated with early treatment. Country of origin accounted for the largest proportion of variation in time. Intercountry heterogeneity was shown in components of elapsed time to treatment. Physicians in the prehospital setting enrolled 63.8% of patients. The presence of a physician was associated with greater adherence to protocol mandated treatments and procedures but with delay in time to treatment (120 v 108 minutes, p < 0.001).

CONCLUSION

Country of enrollment accounted for the largest proportion of variation in time to treatment and intercountry heterogeneity modulated components of delay. The effectiveness and safety of prehospital fibrinolysis was not influenced by the presence of a physician. These data, acquired in diverse health care environments, provide new understanding into the components of prehospital treatment delay and the opportunities to further reduce time to fibrinolysis for patients with ST elevation myocardial infarction.

Dosing errors may impact the risk of rt-PA for stroke: the multicenter rt-PA acute stroke survey

Intravenous recombinant tissue plasminogen activator (rt-PA) is given for acute ischemic stroke using a weight-based dosing regimen, and potential medication dosing errors may impact the relative risks and benefits of this therapy. Weight is frequently estimated by the patient, the family, the nurse, or the treating physician. Discrepancies between actual and estimated weight result in an incorrect dose, but errors of this type have not been previously studied in clinical practice. We hypothesized that such errors may impact the risks and benefits of rt-PA for stroke. The Multicenter rt-PA Acute Stroke Survey included data on 1205 acute stroke patients treated in routine clinical practice with intravenous rt-PA. We calculated the actual unit dose (in mg/kg) by dividing the dose of rt-PA given by the actual weight, and correlated this with risk of intracerebral hemorrhage (ICH) and likelihood of good recovery (modified Rankin score of 0 or 1). Seven hundred and sixty-nine patients (64%) had data on both weight and rt-PA dosage. Forty-one patients (5.4%) had a symptomatic hemorrhage while 51 (6.6%) had an asymptomatic hemorrhage. There were non-significant trends towards increased risk of any ICH as the degree of overdosage increased, particularly in the highest dose quintile compared to the four lower quintiles (15.8% v 11.0%, P = .097). Adjustment for age, baseline NIHSS, and major early computed tomography (CT) changes strengthened this association (16.5% v 9.3%; P = .025). There was no association between actual dose and likelihood of good recovery (P = .57). Overdosage of rt-PA cause by an overestimation of weight resulted in a modest increase in the risk of ICH in the highest quintile, but there did not appear to be any reduction in effectiveness caused by underdosing. Every effort should be made to obtain the most accurate weight.

Review of the Current ACS Practice Guideline to Develop an Ischemic Chest Pain Protocol

This review covers the major recommendations to the 2000 American College of Cardiology/American Heart Association (ACC/AHA) Acute Coronary Syndromes (ACS) Practice Guidelines. This review describes the evidence-based medicine that rationalizes the recommended pharmacotherapy for ST elevation myocardial infarction (STEMI) and non- STEMI (NSTEMI) ACS. To ensure conformity, an Ischemic Chest Pain Protocol (ICPP) order form was developed. The ICPP is like a menu that includes orders for all the recommended therapies in an easy-to-use checklist format. The ICPP has facilitated the implementation, acceptance, and understanding of the 2002 ACC/AHA ACS practice guidelines. Hence with improved conformity, it is hoped that the improved outcomes that were intended will result. A description of the ICPP and a mechanism for implementation is provided in this article.

Thrombolytic therapy. State of the art

Thrombolytic agents have become the corner stone in the treatment of acute myocardial infarction. However, the current agents are far from perfect. New thrombolytic drugs have been designed to overcome these shortcomings. Development of these agents has focused not only on increasing plasma half-life and thus allowing single-bolus administration, but also on improving fibrin specificity and resistance to plasminogen activator inhibitor. The safety and efficacy of several of these promising thrombolytic drugs have been evaluated in large-scale trials, which are discussed in the present review. Parallel to these advances, alternatives to standard thrombolytic regimens have been developed. New trials evaluating the combination of reduced-dose fibrinolytics with different regimens of antithrombotic agents will optimize future reperfusion strategies.

Issues in the assessment of the safety and efficacy of tenecteplase (TNK-tPA)

While thrombolytic agents have demonstrated improved mortality over the use of placebo, this has come at the expense of bleeding complications such as intracranial hemorrhage (ICH). Tenecteplase (TNK-tPA) is a novel thrombolytic agent engineered to improve upon the ease of use and safety of alteplase (t-PA). Given its longer half-life, TNK-tPA can be administered as a single bolus. The dosing of TNK-tPA has been weight optimized to enhance both safety and efficacy outcomes. Weight-optimized TNK-tPA dosing requires body weight estimation, which may introduce the potential for medication error. However, data from TNK-tPA clinical trials suggest that body weight estimates can err by up to 20 kg (44 lb) without an increased risk of ICH or death. Furthermore, the results of TNK-tPA clinical trials showed that even at the highest weight-optimized dosage of 50 mg, ICH rates were among the lowest reported in clinical trials of thrombolytics for acute myocardial infarction. In elderly female patients of low body weight, the use of weight-optimized TNK-tPA lowered the risk of ICH compared with the use of t-PA, expanding the potential use of thrombolytics to this high-risk patient population. Tenecteplase has demonstrated clinical equivalence to t-PA, but with a wider therapeutic margin of safety.

Multimodality reperfusion therapy for acute myocardial infarction

With the strong and direct relation between early reperfusion in acute myocardial infarction (AMI) and improved clinical outcomes, attention has focused on new means of improving rates of reperfusion and accelerating every stage of AMI evaluation and management, from the onset of symptoms of myocardial infarction to the achievement of reperfusion. Critical pathways to streamline the evaluation and management of AMI have cut minutes and even hours off in-hospital treatment times for patients with AMI; public health initiatives focus on educational efforts to shorten time to hospital arrival. The latest advance in fibrinolytic therapy is the availability of bolus fibrinolytic agents with safety and efficacy in large phase III trials comparable to accelerated intravenous infusion regimens. Faster and simpler fibrinolytic regimens may shorten door-to-needle time, reduce medication errors, and facilitate prehospital thrombolysis. Bolus fibrinolytic agents are being evaluated for use in combination with other interventions to open occluded coronary arteries, including acute percutaneous coronary intervention, the glycoprotein IIb/IIIa platelet inhibitors, or both. The goal of this "multimodality" approach to AMI management is to minimize time to reperfusion and maximize the percentage of patients who achieve complete arterial patency and myocardial perfusion without bleeding complications.