Risk stratification for arrhythmic death in an emergency department cohort: a new method of nonlinear PD2i analysis of the ECG

Heart rate variability (HRV) reflects both cardiac autonomic function and risk of sudden arrhythmic death (AD). Indices of HRV based on linear stochastic models are independent risk factors for AD in postmyocardial infarction (MI) cohorts. Indices based on nonlinear deterministic models have a higher sensitivity and specificity for predicting AD in retrospective data. A new nonlinear deterministic model, the automated Point Correlation Dimension (PD2i), was prospectively evaluated for prediction of AD. Patients were enrolled (N = 918) in 6 emergency departments (EDs) upon presentation with chest pain and being determined to be at risk of acute MI (AMI) >7%. Brief digital ECGs (>1000 heartbeats, approximately 15 min) were recorded and automated PD2i results obtained. Out-of-hospital AD was determined by modified Hinkle-Thaler criteria. All-cause mortality at 1 year was 6.2%, with 3.5% being ADs. Of the AD fatalities, 34% were without previous history of MI or diagnosis of AMI. The PD2i prediction of AD had sensitivity = 96%, specificity = 85%, negative predictive value = 99%, and relative risk >24.2 (p ≤ 0.001). HRV analysis by the time-dependent nonlinear PD2i algorithm can accurately predict risk of AD in an ED cohort and may have both life-saving and resource-saving implications for individual risk assessment.

Improving handoffs in the emergency department

Patient handoffs at shift change are a ubiquitous and potentially hazardous process in emergency care. As crowding and lengthy evaluations become the standard for an increasing proportion of emergency departments (EDs), the number of patients handed off will likely increase. It is critical now more than ever before to ensure that handoffs supply valid and useful shared understandings between providers at transitions of care. The purpose of this article is to provide the most up-to-date evidence and collective thinking about the process and safety of handoffs between physicians in the ED. It offers perspectives from other disciplines, provides a conceptual framework for handoffs, and categorizes models of existing practices. Legal and risk management issues are also addressed. A proposal for the development of handoff quality measures is outlined. Practical strategies are suggested to improve ED handoffs. Finally, a research agenda is proposed to provide a roadmap to future work that may increase knowledge in this area.

Comparison of linear-stochastic and nonlinear-deterministic algorithms in the analysis of 15-minute clinical ECGs to predict risk of arrhythmic death

Objective:

Comparative algorithmic evaluation of heartbeat series in low-to-high risk cardiac patients for the prospective prediction of risk of arrhythmic death (AD).

Background:

Heartbeat variation reflects cardiac autonomic function and risk of AD. Indices based on linear stochastic models are independent risk factors for AD in post-myocardial infarction (post-MI) cohorts. Indices based on nonlinear deterministic models have superior predictability in retrospective data.

Methods:

Patients were enrolled (N = 397) in three emergency departments upon presenting with chest pain and were determined to be at low-to-high risk of acute MI (>7%). Brief ECGs were recorded (15 min) and R-R intervals assessed by three nonlinear algorithms (PD2i, DFA, and ApEn) and four conventional linear-stochastic measures (SDNN, MNN, 1/f-Slope, LF/HF). Out-of-hospital AD was determined by modified Hinkle–Thaler criteria.

Results:

All-cause mortality at one-year follow-up was 10.3%, with 7.7% adjudicated to be AD. The sensitivity and relative risk for predicting AD was highest at all time-points for the nonlinear PD2i algorithm (p ≤0.001). The sensitivity at 30 days was 100%, specificity 58%, and relative risk >100 (p ≤0.001); sensitivity at 360 days was 95%, specificity 58%, and relative risk >11.4 (p ≤0.001).

Conclusions:

Heartbeat analysis by the time-dependent nonlinear PD2i algorithm is comparatively the superior test.

The relative utility of cardiac troponin I, creatine kinase-MBmass, and myosin light chain-1 in the long-term risk stratification of patients with chest pain

BACKGROUND

Sensitive and specific cardiac markers convey important short-term prognostic information about patients with an acute coronary syndrome. There are, however, few data assessing their value as long-term predictors.

HYPOTHESIS

The aim of the current study was to assess the relative value of three such markers and clinical characteristics in determining the long-term prognosis of patients with chest pain.

METHODS

Cardiac troponin I (cTnI), myosin light chain-(MLC-1), and creatine kinase-MBmass levels were obtained on admission (0 h) and at 4, 8, 16, and 24 h in 208 patients with chest pain. Eligible subjects were determined, at the time of hospital admission, to be at >7% risk of acute myocardial infarction (MI), but without new ST-segment elevation on their presenting electrocardiogram. Follow-up was performed a median of 28 (range 1-46) months later. The primary study endpoint was death or nonfatal MI, subsequent to the index admission.

RESULTS

Cardiac TnI levels > or = 0.2 ng/ml (odds ratio [OR] 1.93, 95% confidence interval [CI] 1.09-3.40) and MLC-1 levels > or = 1 ng/ml (OR 3.24, 95% CI 1.83-5.73) were both significant predictors of death or MI during long-term follow-up; MLC-1 was, however, the only independent biochemical predictor (OR 2.11,95% CI 1.14-3.93).

CONCLUSIONS

Both cTnl and MLC-1 predict the long-term outcome of patients with chest pain, but, in this cohort, MLC-1 proved to be a better predictor of mortality and nonfatal acute MI.

Adenosine A1 antagonism attenuates beta-adrenergic-resistant sudden hypoxic cardiac insufficiency

OBJECTIVES

In states such as hypoxia, shock, and cardiac arrest, compromised systemic oxygenation or perfusion appears to induce cardiac insufficiency that can be resistant to beta-adrenergic drugs. Elevated levels of adenosine may mediate such beta-adrenergic-resistant cardiac insufficiency via the adenosine A(1) receptor (A(1)AdoR). The objective of this study was to test the hypothesis that selective A(1)AdoR antagonism attenuates hypoxic cardiac insufficiency more efficaciously than beta(1)-adrenergic agonism or nonselective adenosine antagonism.

METHODS

Rats were paralyzed and ventilated to a pCO(2) level of 35-40 mm Hg. Ten minutes before hypoxia (inspired o(2) concentration = 5%), rats were treated intravenously with one of the following: 0.1 mg/kg BG-9719 (n = 9), 10 mg/kg NPC-205 (n = 10; BG-9719 and NPC-205 are selective A(1)AdoR antagonists, with durations of action of 30-60 minutes and 60-90 minutes, respectively), 10 mg/kg aminophylline (n = 12), 5 microg/kg/min dobutamine (n = 11), or control solutions. These drug doses maximized survival duration in dose-response studies.

RESULTS

Before hypoxia, cardiac work was increased more by aminophylline and dobutamine than by BG-9719. Mean (+/-SEM) duration of survival (in minutes) after hypoxia increased from <13 (control solutions) to 13.8 (+/-1.4) (dobutamine), 20.0 (+/-1.6) (aminophylline), 31.7 (+/-4.6) (BG-9719), and 40.5 (+/-7.5) (NPC-205) (p < 0.0001). Heart rate and dP/dt decreased rapidly after hypoxia, but decreases were attenuated with BG-9719 and NPC-205 compared with dobutamine (p < 0.05) and tended toward attenuation with aminophylline.

CONCLUSIONS

BG-9719 and NPC-205 improved survival duration, heart rate, and left ventricular contractility during hypoxia more efficaciously than dobutamine and possibly aminophylline. Selective A(1)AdoR antagonists warrant further study as alternatives to beta-adrenergic agonists in hypoxia, shock, and cardiac arrest, in which compromised systemic perfusion or oxygenation impairs cardiac output.

Adenosine A1 antagonism attenuates atropine-resistant hypoxic bradycardia in rats

OBJECTIVES

To test the following hypotheses: Hypoxia induces bradycardia and hemodynamic compromise that are resistant to atropine but responsive to selective antagonism of the adenosine A1 receptor (A1AdoR). The mechanism for such attenuation is independent of the vagus nerve.

METHODS

Ten minutes after sham or actual bilateral cervical vagotomy, paralyzed ventilated rats were made hypoxic (5% fractional inspired oxygen, continued until death). Five minutes after beginning hypoxia, intravenous treatment with BG-9719, a selective A1AdoR antagonist (0.1 mg/kg); atropine (0.1 mg/kg); BG-9719 vehicle; or saline was initiated. These drug doses were based on pilot studies. Of the eight treatment groups (eight possible combinations of vagotomy status and drug/vehicle treatment), n = 8 in all except nonvagotomized, vehicle-treated rats (where n = 7).

RESULTS

Heart rate and left ventricular contractility decreased rapidly with hypoxia. Atropine had minimal effects in prolonging survival (from mean +/- SEM of 15.5 +/- 2.1 minutes to 20.2 +/- 2.5 minutes, p = 0.94) and attenuating posthypoxic decreases in heart rate (p = 0.89) and contractility (p = 0.83) compared with saline. BG-9719 prolonged survival, however, from 14.4 +/- 1.9 minutes (with vehicle treatment) to 37.2 +/- 6.8 minutes (p < 0.001). Survival, heart rate, and contractility were preserved with BG-9719 compared with atropine and vehicle (p < 0.05, all comparisons). Vagotomy prevented the effects of BG-9719 on survival prolongation (p = 0.003), heart rate (p = 0.01), and contractility (p < 0.001) but did not affect those outcomes in saline-treated rats.

CONCLUSIONS

Survival, heart rate, and contractility were better preserved with BG-9719 than atropine. A1AdoR selective antagonism, possibly because of its multiple mechanisms for attenuating hypoxic cardiac insufficiency, resulted in better hemodynamic and clinical outcomes. That attenuation seems to have a component of vagal mediation.

Biochemical and clinical predictors of long-term outcome in patients with nonspecific chest pain and nondiagnostic electrocardiograms

BACKGROUND

There are few data assessing the relative value of clinical factors and sensitive cardiac markers in determining the long-term prognosis of patients with chest pain. Likewise, little information exists about the long-term outcome of patients with chest pain who have negative markers of myocardial cell necrosis. This study addresses these issues in a cohort of patients with nonspecific chest pain and nondiagnostic electrocardiograms (ECGs).

METHODS

Eligible subjects (n = 501) had experienced >15 minutes chest pain at rest during the previous 24 hours, but were found to be at low-risk for acute myocardial infarction (AMI) by means of a well-validated clinical algorithm. Cardiac troponin I, creatine kinase MB(mass), myoglobin, and myosin light chain-1 were collected at presentation and 3, 6, and 12 hours later. Patients were observed for a median of 31 months. The composite end point was death or AMI subsequent to the index admission.

RESULTS

Cardiac troponin I was the best single biochemical predictor of outcome (risk ratio 2.34, 95% CI 1.31-4.17, P =.004), but was of less independent prognostic value than age and an abnormal presenting ECG. It was also inferior to a combination strategy, using all 4 markers tested (risk ratio 2.37, 95% CI 1.44-3.91, P <.001). Fifty of 428 patients (12%) with a cardiac troponin I level < or =0.2 ng/mL and 25 of 287 patients (9%) without elevation of any marker tested sustained an adverse event during follow-up.

CONCLUSIONS

Cardiac troponin I is the most useful single biochemical predictor of long-term outcome, but the best determinants are age, an abnormal presenting ECG, and an "any marker positive" strategy. Patients without elevated cardiac markers have an adverse event rate of approximately 10% in the subsequent 31 months.

Post hoc mortality analysis of the efficacy trial of diaspirin cross-linked hemoglobin in the treatment of severe traumatic hemorrhagic shock

BACKGROUND

The efficacy trial of diaspirin cross-linked hemoglobin (DCLHb) in traumatic hemorrhagic shock demonstrated an unexpected mortality imbalance, prompting a three-step review to better understand the cause of this finding.

METHODS

Patients were enrolled in this DCLHb hemorrhagic shock study using 28-day mortality as the primary endpoint. Mortality data were primarily analyzed using the TRISS method and a nonblinded clinical review, followed by an independent Pennsylvania Trauma Outcome Study (PTOS)-derived probability of survival analyses. Finally, a trauma expert conducted a blinded clinical review of cases incorrectly predicted by these PTOS analyses.

RESULTS

More of the DCLHb patients predicted to survive using TRISS actually died than in the control subgroup (24% vs. 3%, p < 0.002). Nonblinded clinical review noted that 72% of the patients who died had prior traumatic arrest, a presenting Glasgow Coma Scale score of 3, or a base deficit > 15 mEq/L. DCLHb patients predicted to survive using PTOS also more often died than did control patients (30% vs. 8%, p < 0.04). Blinded clinical review determined that 94% of the deaths were clinically justified. Both the TRISS and the PTOS models gave an adjusted mortality relative risk of 2.3, similar to the unadjusted risk data.

CONCLUSION

Mortality analysis in this shock study involved both clinical case reviews and mortality prediction models. Despite the observation that nearly all of the deaths were clinically justified, the TRISS and PTOS models demonstrated excess unpredicted deaths in the DCLHb subgroup. A combined process, using both mortality prediction models and clinical case reviews, is useful in trauma studies that use a mortality endpoint.

Elevated soluble P-selectin levels are associated with an increased risk of early adverse events in patients with presumed myocardial ischemia

BACKGROUND

Cell adhesion molecules (CAMs) play a pivotal role in the interactions between leukocytes, platelets, and vascular endothelium. Soluble CAMs (sCAMs) are shed from cell surfaces and reflect cellular activation. Elevated levels of sCAMs have been reported in the acute coronary syndromes. We hypothesized, therefore, that sCAMs might prove of prognostic value in patients with acute chest pain presumed to be the result of myocardial ischemia.

METHODS

One hundred twenty-six consecutive patients with chest pain, thought clinically to represent myocardial ischemia, were studied prospectively. Soluble intercellular adhesion molecule-1 (sICAM-1), vascular cell adhesion molecule-1 (sVCAM-1), E-selectin (sE-selectin) and P-selectin (sP-selectin) levels were assayed at presentation, as were cardiac troponin I (cTnI) and creatine kinase-MB(mass) (CK-MB(mass)). The primary study end point was the occurrence of a serious cardiac event (SCE) during the index admission or the subsequent 3 months.

RESULTS

sP-selectin and cTnI levels were significantly higher among patients who had an early SCE (P =.006 and P <.001, respectively). Both remained independently predictive (P <.001) in a multivariate regression equation. The other independent predictor was a history of vascular disease (P <.05). No other markers were significant predictors of early outcome.

CONCLUSION

Elevated sP-selectin levels, but not those of other sCAMs, are predictors of early adverse events in patients with chest pain presumed caused by myocardial ischemia. Their utility in predicting the outcome of individual patients is, however, limited.

Adenosine A1 receptor antagonist prolongs survival in the hypoxic rat

The hypothesis that adenosine A1 receptor (A1AdoR) selective antagonism limits cardiac depression and prolongs survival during acute global hypoxia was tested in a postinsult treatment model using KW-3902 ([8-(noradamantan-3-yl)-1,3-dipropylxanthine]), an A1AdoR selective antagonist. Rats were anesthetized, paralyzed, then ventilated with 8% O2 (hypoxia). In protocol I, 5 min after hypoxia, rats were treated with saline, drug vehicle, or KW-3902 (0.1 mg/kg i.v.). In protocol II, KW-3902 treatment occurred 2.5, 5, or 7.5 min after hypoxia. In protocol I, after hypoxia, left ventricular contractility, heart rate, and systemic mean arterial blood pressure decreased rapidly in saline-and vehicle-treated groups. In contrast, KW-3902 significantly attenuated the decline in these variables. Survival time (the time from the commencement of hypoxia until death) was more prolonged with KW-3902 (109.5 +/- 9.1 min) than with saline (37.6 +/- 5.0 min) or vehicle (35.0 +/- 4.2 min) (p < 0.001). In protocol II, survival time increased from 29.2 +/- 5.5 min in the 7.5-min treatment group to 109.5 +/- 9.5 min (5-min group) and 245.9 +/- 26.1 min (2.5-min group; p < 0.001). KW-3902 prolongs survival in this model, presumably by antagonizing A1AdoR-mediated inhibition of cardiac function. Also, treatment efficacy is highly time dependent.

Soluble intercellular adhesion molecule-1 as a predictor of early adverse events in patients with chest pain compatible with myocardial ischemia

STUDY OBJECTIVE

Inflammation plays an important role in acute coronary syndromes, and some evidence indicates that patients with a more pronounced vascular inflammatory response have a poorer outcome. Soluble intercellular adhesion molecule-1 (sICAM-1) is a specific marker for vascular endothelial cell activation. The aim of this study was to investigate the prognostic value of plasma sICAM-1 levels in patients with acute chest pain compatible with myocardial ischemia.

METHODS

This prospective study was conducted at 2 urban university medical centers. The study cohort consisted of 119 consecutive patients with chest pain in whom myocardial ischemia was suspected clinically at presentation. Patients with conditions that affect sICAM-1 levels were ineligible. Cardiac troponin I (cTnI), C-reactive protein, and sICAM-1 levels were assayed at presentation to the emergency department. The primary end point was the occurrence of a serious cardiac event (death, nonfatal acute myocardial infarction, coronary revascularization) in the hospital.

RESULTS

Although sICAM-1 levels tended to be higher in patients with a serious cardiac event, there was no significant association. In contrast, a cTnI level greater than 0.2 ng/mL was a powerful predictor of an in-hospital serious cardiac event (odds ratio 16.3, 95% confidence interval [CI] 4.7 to 55.9; P <.0001). Soluble ICAM-1 levels of more than 260 ng/mL at presentation had a sensitivity for predicting a serious cardiac event of 63% (95% CI 46% to 81%) but a specificity of only 47% (95% CI 38% to 57%).

CONCLUSION

In a heterogeneous population of patients with chest pain compatible with myocardial ischemia, elevated sICAM-1 levels are poor predictors of an individual patient suffering a serious cardiac event in the hospital.

Prediction of hyperkalemia in dogs from electrocardiographic parameters using an artificial neural network

OBJECTIVE

To predict severe hyperkalemia from single electrocardiogram (ECG) tracings.

METHODS

Ten conditioned dogs each underwent this protocol three times: Under isoflurane anesthesia, 2 mEq/kg/hr of potassium chloride was given intravenously until P-waves were absent from the ECG and ventricular rates decreased > or =20% in < or =5 minutes. Serum potassium levels (K(+)) were measured at regular intervals with concurrent digital storage of lead II of the surface ECG. A three-layer artificial neural network with four hidden nodes was trained to predict K(+) from 15 separate elements of corresponding ECG data. Data were divided into a training set and a test set. Sensitivity, specificity, and diagnostic accuracy for recognizing hyperkalemia were calculated for the test set based on a prospectively defined K(+) = 7.5.

RESULTS

The model produced data for 189 events; 139 were placed in the training set and 50 in the test set. The test set had 37 potassium levels at or above 7.5 mmol/L. The neural network had a sensitivity of 89% (95% CI = 75% to 97%) and a specificity of 77% (95% CI = 46% to 95%) in recognizing these. The positive likelihood ratio was 3.87. Overall accuracy of this model was 86% (95% CI = 73% to 94%). Mean (+/-SD) difference between predicted and actual K(+) values was 0.4 +/- 2.0 (95% CI = -0.2 to 1.0).

CONCLUSIONS

An artificial neural network can accurately diagnose experimental hyperkalemia using ECG parameters. Further work could potentially demonstrate its usefulness in bedside diagnosis of human subjects.

What is gross hematuria? Correlation of subjective and objective assessment

BACKGROUND

Gross hematuria is a screening test used to help determine the need for radiographic evaluation in patients with blunt trauma. This subjective assessment has not been compared with objective measures, nor has interrater reliability been described.

METHODS

We performed a prospective, randomized, controlled study to determine the ability of clinicians to assess gross hematuria. Clinicians were asked to assess samples containing various concentrations of blood diluted in urine for the presence of gross hematuria.

RESULTS

Gross hematuria was recognized by more than 95% of clinicians only when samples contained more than 3,500 red blood cells per high-power field. Clinicians' interpretations were independent of profession, specialty, and level of training (p > 0.08).

CONCLUSION

Clinicians demonstrate poor sensitivity and interrater reliability identifying gross hematuria by inspection. Clinical studies correlating degrees of hematuria to the need for genitourinary diagnostic evaluation should report both subjective and objective measures to identify a threshold value predictive of renal injury.

Coronary artery disease in patients with chest pain who have low-risk clinical characteristics and negative cardiac troponin I

Patients who have low-risk clinical features and negative cardiac troponin levels may be suitable for early discharge after a brief period of observation in the emergency department (ED). Little is known about the prevalence and severity of coronary artery disease in such patients, although this has implications for follow-up. Subjects included 570 patients who were at < or =7% risk of acute myocardial infarction (AMI), remained clinically stable (defined as the absence of new ischemic changes on their electrocardiograph, signs or symptoms of heart failure, the development of a cardiac arrhythmia or hypotension requiring either inotropes or volume repletion) and had cardiac troponin I (cTnI) levels <0.2 microgl(-1) during the initial 12 hours of hospitalization. Clinical features were documented and those undergoing stress tests and/or coronary angiograms had these graded by 2 independent observers. Overall, 190 (33.3%) of this population, who might be considered suitable for early discharge, had objective evidence of coronary artery disease. Patients with chest pain who are at low risk of AMI, remain clinically stable and have negative cTnI over the initial 12 hours of observation are a heterogeneous population, some of who have threatening coronary disease. This does not preclude early discharge from the ED but emphasizes the need for careful assessment and follow-up.

Intravenous magnesium is ineffective in adult asthma, a randomized trial

Intravenous magnesium sulphate (MgSO4) has been tried in the emergency department treatment of asthma since the mid-1980s, but published reports vary as to its efficacy. The literature suggests that it may be effective in the more severely ill asthmatic. We evaluated i.v. MgSO4 in adult asthmatics having a moderate to severe exacerbation. The study was performed in a convenience sample of adult asthmatics between the ages of 18 and 55 presenting to the emergency department with a peak expiratory flow (PEF) of < 100 l/min or < 25% of predicted flow. Patients received either 2.0 grams of MgSO4 or placebo in a randomized, double-blind fashion. All patients received inhaled bronchodilators and i.v. steroids. Outcome variables were: improvement in PEF, subjective respiratory distress as measured by the Borg dyspnoea scale (BDS) and hospital admission. The first visits of 42 patients presenting with acute asthma exacerbations were evaluated, 18 receiving MgSO4 and 24 receiving placebo. The t = 60 peak flow in the MgSO4 group was 174 l/min versus 212 l/min in placebo, p = 0.04. Controlling for age, heart rate, initial PEF and initial BDS in ordinal logistic regression, the t = 60 Borg scale of subjective dyspnoea had an odds ratio of 1.54 in favour of more dyspnoea in MgSO4 (95% C.I., 0.36-6.67; p = 0.56). Five of 18 patients (28%) receiving MgSO4 were admitted compared with 5 of 24 (21%) receiving placebo (p = 0.72). In moderately severe adult asthmatics, 2.0 grams of MgSO4 i.v. resulted in less improvement in peak expiratory flow compared with placebo. MgSO4 did not appear to decrease subjective dyspnoea or the hospital admission rate. This evidence does not support the use of MgSO4 in the treatment of acute asthma.

Effect of ethnicity on denial of authorization for emergency department care by managed care gatekeepers

OBJECTIVE

After a pilot study suggested that African American patients enrolled in managed care organizations (MCOs) were more likely than whites to be denied authorization for emergency department (ED) care through gatekeeping, the authors sought to determine the association between ethnicity and denial of authorization in a second, larger study at another hospital.

METHODS

A retrospective cohort design was used, with adjustment for triage score, age, gender, day and time of arrival at the ED, and type of MCO.

RESULTS

African Americans were more likely to be denied authorization for ED visits by the gatekeepers representing their MCOs even after adjusting for confounders, with an odds ratio of 1.52 (95% CI = 1.18 to 1.94).

CONCLUSIONS

African Americans were more likely than whites to be denied authorization for ED visits. The observational study design raises the possibility that incomplete control of confounding contributed to or accounted for the association between ethnicity and gatekeeping decisions. Nevertheless, the questions that these findings raise about equity of gatekeeping indicate a need for additional research in this area.

The effect of lower-extremity position on cerebrospinal fluid pressures

OBJECTIVE

To determine the effects of lower-extremity positioning on cerebrospinal fluid opening pressure (CSFp). The authors believed that during lumbar puncture (LP), CSFp does not meaningfully decrease when the lower extremities are extended from flexion, as is often suggested.

METHODS

In a convenience sample of adult patients who clinically required LP in an urban emergency department, three sequential CSFp measurements were obtained in either sequence A (knee, hip, and neck flexion [90 degrees ], then extension, then flexion) or sequence B (extension, flexion, then extension) prior to CSF withdrawal. The neck was flexed at 30 degrees when the lower extremities were flexed, while the thoracolumbar spine was kept in the neutral position for all measurements.

RESULTS

Nineteen patients were studied in each sequence. Although variable, overall within-patient changes between positions were not clinically meaningful. Mean and 95% confidence intervals (95% CIs) for the decrease in CSFp from position 1 to position 3 (same position) were 0.2 cm H(2)O (1.7%) and 0.9 to -0.6 cm H(2)O (6% to -2.7%), respectively. Changing from flexion to extension decreased pressure measurements by a mean of 0.9 cm H(2)O (2.5%) [95% CI = 2.1 to -0.1 cm H(2)O (7.6% to -2.4%)]. Changing from extension to flexion increased CSFp by a mean of 1.1 cm H(2)O (6.1%) [95% CI = 0.2 to 2.0 cm H(2)O (1.3% to 11.5%)], a statistically but not clinically meaningful change.

CONCLUSIONS

Changing lower-extremity position did not meaningfully change mean CSFp. These data do not support the common suggestion that extending the lower extremities during LP meaningfully decreases CSF opening pressures.

Follow-up program for emergency department patients with gonorrhea or chlamydia

OBJECTIVES

To study the performance of a centralized regional follow-up program organized by a municipal department of health (DH) for female patients presenting to the emergency department (ED) with Neisseria gonorrhoeae and/or Chlamydia trachomatis, who are not diagnosed or treated at the time of presentation.

METHODS

This was a retrospective observational study of female patients seen in the ED with positive cervical specimens, and their subsequent treatment and follow-up by the DH. Medical records were reviewed to determine the female patients seen in the ED who had positive specimens for N. gonorrhoeae or C. trachomatis. The DH followed up those not treated in the ED. Analysis of how long it took for these patients to be treated and the proportion lost to follow-up was performed.

RESULTS

Of 2,121 specimens, 342 were positive for N. gonorrhoeae or C. trachomatis. Of the 342, 154 (45%) were recognized and appropriately treated in the ED. One hundred fifty-nine of the 342 (46.5%) patients were discharged from the ED without treatment but were contacted by the DH and appropriate treatment was provided. The DH could not locate 23 (6.7%) patients, and four (1.2%) refused treatment. One died before treatment. Only 21 of the 159 were treated within nine days. Median time to treatment was 36 days.

CONCLUSIONS

Centralized laboratory analysis and follow-up by the DH for N. gonorrhoeae and C. trachomatis identified many female patients undiagnosed and untreated in the ED. The DH follow-up program provided appropriate treatment to most female patients.

Nonlinear dynamics of heart rate variability during experimental hemorrhage in ketamine-anesthetized rats

Indexes of heart rate variability (HRV) based on linear stochastic models are independent risk factors for arrhythmic death (AD). An index based on a nonlinear deterministic model, a reduction in the point correlation dimension (PD2i), has been shown in both animal and human studies to have a higher sensitivity and specificity for predicting AD. Dimensional reduction subsequent to transient ischemia was examined previously in a simple model system, the intrinsic nervous system of the isolated rabbit heart. The present study presents a new model system in which the higher cerebral centers are blocked chemically (ketamine inhibition of N-methyl-D-aspartate receptors) and the system is perturbed over a longer 15-min interval by continuous hemorrhage. The hypothesis tested was that dimensional reduction would again be evoked, but in association with a more complex relationship between the system variables. The hypothesis was supported, and we interpret the greater response complexity to result from the larger autonomic superstructure attached to the heart. The complexities observed in the nonlinear heartbeat dynamics constitute a new genre of autonomic response, one clearly distinct from a hardwired reflex or a cerebrally determined defensive reaction.

Hypertonic saline treatment of severe hyperkalemia in nonnephrectomized dogs

OBJECTIVES

To determine whether a hypertonic saline bolus improves cardiac conduction or plasma potassium levels more than normal saline infusion within 15 minutes of treatment for severe hyperkalemia. Previously with this model, 8.4% sodium chloride (NaCl) and 8.4% sodium bicarbonate (NaHCO(3)) lowered plasma potassium equally effectively.

METHODS

This was a crossover study using ten conditioned dogs (14-20 kg) that received, in random order, each of three intravenous (IV) treatments in separate experiments at least one week apart: 1) 2 mmol/kg of 8.4% NaCl over 5 minutes (bolus); 2) 2 mmol/kg of 0.9% NaCl over one hour (infusion); or 3) no treatment (control). Using isoflurane anesthesia and ventilation (pCO(2) = 35-40 torr), 2 mmol/kg/hr of IV potassium chloride (KCl) was infused until conduction delays (both absent p-waves and >/=20% decrease in ventricular rate in </=5 minutes) were sustained for 15 minutes. The KCl was then decreased to 1 mmol/kg/hr (maintenance) for 2 hours and 45 minutes. Treatment (0 minutes) began after 45 minutes of maintenance KCl.

RESULTS

From 0 to 15 minutes, mean heart rate increased 29.6 (95% CI = 12.2 to 46; p < 0.005) beats/min more with bolus than infusion and 23.4 (95% CI = 2.6 to 43.5; p < 0.03) beats/min more with bolus than control. No clinically or statistically significant difference was seen in heart rate changes from 0 to 30 minutes. Decreases in potassium from 0 to 15 minutes were similar with bolus, infusion, and control.

CONCLUSIONS

In this model, 8.4% NaCl bolus reversed cardiac conduction abnormalities within the first 15 minutes after treatment, more rapidly than did the 0.9% NaCl infusion or control. This reversal occurred despite similar reductions in potassium levels.

Antagonism of the cardiodepressant effects of adenosine during acute hypoxia

OBJECTIVE

To determine whether pharmacologic antagonism of adenosine A1-receptor-mediated cardiovascular changes can improve cardiac function and prolong survival during systemic hypoxia.

METHODS

Rats were anesthetized with ketamine, instrumented [including left ventricular (LV) pressure transducing catheters], paralyzed with vecuronium, then ventilated to pCO2 = 35-40 torr. After 10 minutes of equilibration (baseline), treatment commenced with saline (n = 7), NPC-205, an adenosine A1 receptor selective antagonist, at doses of 1 mg/kg (n = 10) or 10 mg/kg (n = 10), or drug vehicle (n = 9). Ten minutes later, inspired oxygen was reduced to 5%.

RESULTS

Survival duration (min) post-hypoxia increased in a dose-dependent fashion from 10.4 +/- 1.4 (mean +/- SEM) with vehicle control to 23.0 +/- 4.7 and 41.1 +/- 5.7 with 1 and 10 mg/kg NPC-205, respectively (p < 0.000). Five minutes post-hypoxia, dose-dependent increases were also seen in the percentage of pre-hypoxic values of LV contractility [25.9 +/- 8.1 (vehicle), 39.5 +/- 9.6 (1 mg/kg NPC-205), and 56.5 +/- 8.7 (10 mg/kg NPC-205), p = 0.01], heart rate [60.6 +/- 8.3 (vehicle), 74.7 +/- 8.2 (1 mg/kg NPC-205), and 90.4 +/- 24.1 (10 mg/kg NPC-205), p = 0.02], and blood pressure [16.1 +/- 4.8 (vehicle), 28.8 +/- 8.6 (1 mg/kg NPC-205), and 51.7 +/- 8.2 (10 mg/kg NPC-205), p = 0.004].

CONCLUSIONS

The adenosine A1 selective antagonist prolonged survival in this model. This prolongation was attributed to inhibition of adenosine A1 receptor-mediated decline in cardiac inotropy and chronotropy. Adenosine A1 receptor-selective antagonists show promise as adjunctive therapy for hypoxia-induced cardiac insufficiency by prolonging the treatment window until more definitive resuscitation measures are taken.

Prevalence of cocaine use and its impact on asthma exacerbation in an urban population

OBJECTIVES

To assess the prevalence of cocaine use, and its impact on severity of presentation, among adults presenting to the emergency department (ED) with asthma. A secondary aim was to assess the use of various asthma treatment modalities, with reference to the 1997 National Asthma Education and Prevention Program (NAEPP) guidelines.

METHODS

All adults aged 18 to 55 years who presented to the ED of this institution with an asthma attack, were approached about participating in the study, which required giving informed consent, answering a facilitated questionnaire, and giving a urine sample for drug screening.

RESULTS

Patients were enrolled during a 7-month period. A total of 163 patients were approached to enter the study; 116 patients consented to participate in the study, with 103 submitting complete urine samples. Thirty-seven patients refused to participate, and 10 were excluded. Sixty-eight percent of the patients were women, with a mean age of 33 years. African-Americans made up 89% of the total group. Thirty-five percent were cigarette smokers. Urine cocaine tests were positive in 13 of 103 (13%); 6 of 103 (5.8%) were positive for opiates. In the cocaine-positive group, 5 of 13 patients (38%) were admitted to the hospital, including two patients requiring intubation and mechanical ventilation. Of the total group, 23 of 103 patients (22%) were admitted, and 5 of those 23 admitted patients (22%) were cocaine-positive. Length of stay was significantly longer (5 vs 2.5 days, p < 0.05) in the cocaine-positive admitted patients. Forty-six percent of all patients reported using inhaled corticosteroids (ICS), with 39% of admitted patients using them. Thirty-two percent of all patients had obtained three or more refills of their beta(2)-agonist inhaler in the previous month.

CONCLUSIONS

The prevalence of cocaine use may be much higher than the 13% shown in this study, because of patients' refusal to participate in the study. Second, the severity of exacerbation appears to be worse in the cocaine-positive group. Finally, the majority of patients presenting did not use ICS in accordance with the NAEPP guidelines.

Utility of cardiac troponin I, creatine kinase-MB(mass), myosin light chain 1, and myoglobin in the early in-hospital triage of "high risk" patients with chest pain

OBJECTIVE

To evaluate the use of cardiac troponin I (cTnI), creatine kinase-MB(mass) (CK-MB(mass)), myosin light chain 1 (MLC 1), and myoglobin in identifying "high risk" patients with chest pain who will experience serious cardiac events (SCEs) in hospital.

DESIGN

Prospective study.

SETTING

University affiliated medical centre in Philadelphia, USA.

PATIENTS

208 patients with chest pain, at > 7% risk of acute myocardial infarction (MI), but without new ST segment elevation on their presenting ECG.

INTERVENTIONS

cTnI, CK-MB(mass), MLC 1, and myoglobin concentrations were obtained on admission (0 hour) and at 4, 8, 16, and 24 hours.

MAIN OUTCOME MEASURES

The sensitivity, specificity, positive and negative predictive value, and pre- and post-test probabilities of patients suffering an SCE in hospital were determined. SCEs included cardiac death, acute MI, cardiac arrest, life threatening cardiac arrhythmia, cardiogenic shock, and urgent coronary revascularisation.

RESULTS

Admission concentrations of all markers were poor predictors of SCEs in hospital but improved substantially at subsequent timepoints. cTnI and CK-MB(mass) were consistently the most useful prognostic indicators. If both were negative at 0, 4, and 8 hours, then 99% (95% confidence interval 96% to 100%) of patients remained free from SCEs. The only SCEs not thus predicted were revascularisation procedures and associated complications. Additional tests after 8 hours, or the inclusion of additional markers, did not improve predictive accuracy further.

CONCLUSIONS

Patients with high risk clinical features on admission who have negative cTnI and CK-MB(mass) concentrations at 0, 4, and 8 hours later have a favourable in-hospital prognosis and could be considered for early triage out of coronary care units.

Use of tube condensation as an indicator of endotracheal tube placement

STUDY OBJECTIVE

To determine whether condensation on the inner surface of the endotracheal tube (vapor trail) is a reliable indicator of intratracheal placement.

METHODS

Twenty-seven separate experiments were conducted on 10 conditioned, mongrel dogs weighing 15 to 20 kg each. After induction of anesthesia, an endotracheal tube was placed in the trachea under direct visualization. A second, identical endotracheal tube was then placed in the esophagus. An attending emergency physician, blinded to tube placement, then used a bag-valve apparatus to manually ventilate each endotracheal tube in turn. Five ventilations were performed on each tube, and the presence or absence of condensation on the inner surface of the tube was recorded. A second physician, blinded both to tube placement and to the actions of the first assessor, then repeated the ventilation and assessment of both tubes.

RESULTS

Vapor trail was observed in 27 (100%) of 27 endotracheal tubes correctly placed in the trachea (95% confidence interval [CI], 90% to 100%) and in 23 (83%) of 27 tubes placed in the esophagus (95% CI, 66% to 96%). Physicians concurred in all cases. Absence of vapor trail was 15% sensitive (95% CI, 4% to 34%) for indicating incorrect (esophageal) tube placement.

CONCLUSION

In this model, condensation on the inner surface of the endotracheal tube was common after placement within the esophagus. If these results are confirmed in human studies, the presence of a vapor trial should not be used as a clinical indicator of correct endotracheal tube placement.

A study of the workforce in emergency medicine

STUDY OBJECTIVE

Emergency medicine has progressed significantly since its initial recognition as a medical specialty. Relatively little factual information is known, however, regarding who or how many physicians practice emergency medicine. The purpose of this study is to determine the total number of physicians practicing clinical emergency medicine during a specified period, to describe certain characteristics of those individuals, and to estimate the total number of full-time equivalents (FTEs), as well as the total number of individuals needed to staff those FTEs.

METHODS

Data were gathered from a survey of a random sample of 2,062 hospitals drawn from a population of 5,220 hospitals reported by the American Hospital Association as having, or potentially having, an emergency department. The survey instrument addressed items such as descriptive data on the institution, enumeration of physicians in the ED, as well as the total number working during the period June 1, 1997, through June 14, 1997. Demographic data on the individuals were also collected.

RESULTS

A total of 942 hospitals responded (a 45.7% return rate). These hospitals reported a total of 5,872 physicians were working during the specified period, or an average of 7.48 persons scheduled per institution. The physicians were scheduled for a total of 297,062 hours. The average standard for FTE was 40 clinical hours per week. This equates to 3,713 FTEs or 4.96 FTEs per institution. The ratio of persons to FTEs was 1.51:1. With regard to demographics, 83% of the physicians were men and 81% were white. Their average age was 42 years. As to professional credentials, 58% were emergency medicine-residency trained and 53% were board certified in emergency medicine; 46% were certified by the American Board of Emergency Medicine.

CONCLUSION

Given that there are 4,945 hospitals with EDs and given that the data indicate there are 4.96 FTEs per ED, the total number of FTEs is projected to be 24,548 (standard error = 437). Given further that the data indicate a physician/FTE ratio of 1.51:1, we conclude that there are 36,990 persons (standard error = 683) needed to staff those FTEs. When adjusted for persons working at more than one ED, that number is reduced to 32,026.

Use of ultrasound to determine need for laparotomy in trauma patients

STUDY OBJECTIVE

To determine whether abdominal ultrasound can be used routinely as the primary screening test to identify the need for laparotomy in trauma patients.

METHODS

Ultrasound was used at a Level II trauma center as a primary screening test for evaluation of intraabdominal injury. We reviewed the charts of all patients from trauma codes presenting between January 1, 1991, and December 31, 1993, to determine the results of abdominal ultrasound evaluation and to learn whether laparotomy was required.

RESULTS

A total of 2,013 trauma patients presented during the study interval. Ultrasound was performed in 1,631 patients as the primary screening test for abdominal injury (mean time after arrival, 22.9 minutes), abdominal computed tomography (CT) was performed as the primary screen on 8 (mean time, 68.6 minutes), and 93 patients underwent both ultrasound and CT of the abdomen. Of 86 patients requiring laparotomy who were screened by ultrasound, 80 had positive diagnostic findings, for a sensitivity of 93.0%. Of the 1,545 ultrasound-screened patients who did not require laparotomy, 1,390 had negative findings, for a specificity of 90.0%. None of the patients with negative ultrasound results died or sustained identifiable mortality as a consequence of their negative scans.

CONCLUSION

Ultrasound is a sensitive and specific test with which to evaluate trauma patients for abdominal injury requiring surgery. Routine abdominal ultrasound can be performed at the bedside in the emergency department as a timely, noninvasive diagnostic test. This use of a screening abdominal ultrasound examination can improve clinical decision-making for the use of emergency laparotomy. Ultrasound may be a better alternative to CT or diagnostic peritoneal lavage for the initial screening evaluation of abdominal trauma.

Alkalinization is ineffective for severe hyperkalemia in nonnephrectomized dogs. Hyperkalemia Research Group

OBJECTIVE

To determine whether alkalinization with sodium bicarbonate (NaHCO3) in near-lethal hyperkalemia either lowers potassium (K) rapidly or shortens duration of cardiac conduction disturbances.

METHODS

A controlled canine laboratory investigation of 3 treatments for severe hyperkalemia. Conditioned dogs (n = 8; 17-30 kg) received, in random order, 2 mmol/kg of each of 3 treatments (matched in sodium and water) in separate experiments > or = 1 week apart: 1.05% NaHCO3 over 60 minutes (infusion therapy); 8.4% NaHCO3 over 5 minutes, then 14 mL/kg sterile water over 55 minutes (bolus therapy); 8.4% NaCl over 5 minutes, then 14 mL/kg sterile water over 55 minutes (saline therapy). Prior to administering one of the above therapies, the animals were anesthetized with 0.5-2.5% isoflurane and ventilated to maintain a normal PCO2. After 30 minutes of equilibration, 2 mmol/kg/hr (loading dose) of a 2-mmol/mL KCl solution was given until idioventricular or relative junctional bradycardic dysrhythmias were sustained for 15 minutes. Then KCl was decreased to 1 mmol/kg/hr (maintenance dose) for 2 hours and 45 minutes. Treatment was begun after 45 minutes of maintenance KCl infusion.

RESULTS

The pretreatment K level (all studies) was 9.06 +/- 0.82 mmol/L (mean +/- SD). Although the mean K level decreased more after saline therapy than after bolus therapy at every time, differences were neither statistically significant nor clinically important during the first 30 minutes. The means of the differences in decreases (saline minus bolus) were small, 0.26 (95% CI, -0.48 to 1.00) at 15 minutes, 0.16 (95% CI, -0.67 to 0.98) at 30 minutes. Dysrhythmia duration was shorter with bolus therapy than for saline therapy in only 1 of 5 dogs (p = 0.38).

CONCLUSIONS

Hypertonic saline bolus lowered plasma K as effectively as NaHCO3 bolus in this animal model within the first 30 minutes. Clinically meaningful decreases due to alkalinization alone within 30 minutes are unlikely.

The mangled extremity. Compartment syndrome and amputations

Injuries that amputate, crush, or otherwise mangle an extremity are devastating. The possibilities of medical and psychologic disability, multiple operations, and protracted rehabilitation loom before these patients. Fortunately, expert care given by the emergency department physician maximizes the opportunity for success should the limb be replanted or revascularized. The first priority for the emergency department staff is the efficient and aggressive resuscitation of the patient. Only after this has been carried out and other life-threatening injuries addressed can attention be directed toward the injured limb. It is in the patient's best interest if the emergency department staff assumes that a mangled extremity will be replanted or revascularized. Advances in microsurgical technique and equipment have enabled surgeons to achieve salvage rates greater than 90%. Continued improvements in technique, equipment, rehabilitation, and patient selection will enable more patients to benefit from limb salvage procedures.

Steroids for the treatment of corrosive esophageal injury: a statistical analysis of past studies

Caustic esophageal injury causes substantial morbidity and mortality. However, the use of corticosteroids to treat this problem has been evaluated in a limited number of studies because adequate sample size is difficult to obtain. We analyzed 361 subjects with corrosive esophageal injury derived from 10 retrospective and three prospective publications. We divided cases into those treated with corticosteroids and antibiotics (T) and those that received neither modality (NT) based on inclusion and exclusion criteria. Forty-one percent of NT cases developed esophageal stricture and 19% of T cases developed this complication (P less than .01). There were no reported strictures among 72 first-degree esophageal burns (combined T and NT cases). The T group contained 54 strictures among 228 patients (24%) with either second- or third-degree burns. The NT group of 25 patients with the same burn severity suffered 13 strictures (52%) (P less than .01). Reports of death and gastrointestinal hemorrhage did not increase among steroid-treated patients. We do not recommend corticosteroid therapy for first-degree esophageal injuries. However, this therapy may be useful in preventing strictures among patients with second- or third-degree corrosive esophageal burns.

Prehospital transcutaneous cardiac pacing for symptomatic bradycardia

We studied patients with symptomatic bradycardia to determine the importance of presenting hemodynamic status and prehospital transcutaneous cardiac pacing (TCP) upon patient survival. Of 51 patients with witnessed cardiovascular decompensation and initial bradycardia, 27 (53%) received TCP. There were no significant differences between the paced patients and those without TCP for mean times from collapse until cardiopulmonary resuscitation, paramedic arrival and a paceable rhythm, or from paramedic arrival until a paceable rhythm. Overall, emergency department arrival with a palpable pulse (26% in paced vs 13% in nonpaced group; P = 0.20) and survival to hospital discharge (15% in paced vs 0% nonpaced group; P = 0.07) tended to be better for the paced group. No patient without a palpable pulse on paramedic arrival survived to leave the hospital. Of patients with a palpable pulse upon paramedic arrival, survival to hospital discharge was greater for the paced group (80% in paced vs 0% in nonpaced group; P = 0.024). TCP appears to be most beneficial in those patients with bradycardia who have a palpable pulse when first seen.

Aerobic bacteria cultured from the mouth of the American opossum (Didelphis virginiana) with reference to bacteria associated with bite infections

The American opossum inflicts bite injuries both when hunted for food and when accidentally provoked when handled in captivity. This study involved aerobically culturing organisms from the mouths of seven wild opossums (Didelphis virginiana). Isolates included streptococci, coagulase-positive and -negative staphylococci, Aeromonas spp., Citrobacter freundii, Eikenella corrodens, and Escherichia coli.

Threshold, enzymatic, and pathologic changes associated with prolonged transcutaneous pacing in a chronic heart block model

Previous studies have shown that 30 minutes of transcutaneous cardiac pacing (TCP) can induce mild, clinically insignificant myocardial damage. Longer use of TCP may cause more severe cardiac damage which might result in an increase in the capture threshold for subsequent transvenous cardiac pacing (TVP). To assess this possibility, we examined changes induced by TCP in a canine chronic heart block model. Heart block was induced in conditioned dogs (n = 8) by His bundle ablation. Seven to 10 days after induction of heart block, six animals were paced. Cardiac enzymes were drawn before pacing and at 4, 24, 48, and 72 hours after pacing. Although there was a significant rise in CK at 4 and 24 hours (P less than 0.05), there was no detectable rise in the MB fraction in any of the paced animals. There was no elevation of LDH after pacing, although three animals did develop an LDH1/LDH2 isoenzyme flip indicative of myocardial damage. Animals were sacrificed 72 hours after pacing and their hearts were examined for gross and microscopic changes. The hearts of the paced animals revealed subendocardial, subepicardial, and perivascular areas of basophilic degeneration involving less than 1% of the myocardium in four of six animals. No evidence of such damage was seen in two heart-blocked control animals not undergoing pacing. TVP and TCP capture thresholds assessed before and after a 60-minute TCP pacing period showed no significant change. Hence, use of TCP for a 60-minute period prior to TVP appears to be a safe emergency pacing technique.

Prehospital trial of emergency transcutaneous cardiac pacing

A prospective alternate-day controlled trial of prehospital transcutaneous cardiac pacing (PACE) of hemodynamically significant bradycardia and asystole was undertaken. All patients had a Glasgow coma scale score of 12 or less. Patients in the control group (n = 101) received standard advanced cardiac life support (ACLS) care. Patients in the pacing group (n = 101) were to receive PACE in addition to standard ACLS treatment; 89 patients were actually paced. The two groups were comparable in terms of age, sex, presenting rhythm, and mean times to cardiopulmonary resuscitation (CPR) and ACLS. For the 144 patients in whom the time of arrest could be estimated, the mean times to CPR and ACLS were 5.3 +/- 4.0 and 10.9 +/- 7.1 min, respectively. For the 65 paced patients in whom the time of arrest could be estimated, the mean time from arrest to pacing was 21.8 +/- 8.8 min (range 2 to 43). Multivariate analysis of outcome variables (presentation to emergency department with a pulse, admission to the hospital, and discharge from the hospital) revealed that an initial rhythm of ventricular tachycardia or fibrillation and a short time to ACLS were correlated with a favorable outcome (p less than .05; logistic regression analysis). A short time to PACE was associated with admission to the hospital (p = .20; logistic regression analysis). The use of a stand-alone transcutaneous pacing device in the prehospital arrest setting was associated with generally long times until pacing and did not appreciably improve outcome. Use of PACE in patients demonstrating prehospital bradycardia without neurologic impairment remains to be evaluated.

Transcutaneous and transvenous cardiac pacing for early bradyasystolic cardiac arrest

Emergency transcutaneous cardiac pacing was studied prospectively in 19 patients presenting to the emergency department with a bradyasystolic cardiopulmonary arrest of 20 minutes duration or less. Pacing was initiated when conventional advanced cardiac life support (including atropine administration) and a fluid challenge failed to restore a pulse. Seventeen patients also had placement of transvenous pacemaker electrodes for cardiac pacing. Transcutaneous cardiac pacing rapidly established a blood pressure in the two patients who for clinical reasons did not receive a transvenous pacemaker. Five patients were transcutaneously paced within five minutes of cardiac arrest (Group 1) and the remaining 14 were paced between five and 20 minutes following cardiac arrest (Group 2). Two of the Group 1 patients were admitted and subsequently recovered full neurological and prearrest cardiac function. Fewer Group 2 patients developed a blood pressure (P = .04), and there were no patients with full neurologic recovery in this group (P = .06). Similar results were found for transvenous cardiac pacing; there was a greater incidence of a palpable pulse and measurable blood pressure (P = .05 for both) in the Group 1 patients than in the Group 2 patients. No difference in clinical outcome was noted between the two pacing techniques. These results support the concept that cardiac pacing must be initiated early if the outcome of bradyasystolic cardiac arrest is to be altered.

Radiologic assessment of transvenous pacemaker placement during CPR

During an 18-month period we prospectively studied 36 emergency department patients who had a transvenous pacing catheter placed without fluoroscopic or ECG guidance during closed-chest massage. Transvenous pacing was instituted at a mean elapsed time of 35 minutes (range, ten to 80 minute) after the onset of cardiac arrest, including prehospital and ED care times. Catheter tip position was assessed using postresuscitation or postmortem chest radiographs. Pacing catheters were fixed in the position of electrical capture prior to radiographs; when capture was never achieved, the catheter was fixed at 35 cm from the point of insertion. Position of the catheter tip on radiographs was as follows: right ventricle, ten of 36 patients; right atrium, 18 of 36; and other location, eight of 36. Ectopic catheter tip positions included inferior vena cava (four), pulmonary artery (one), hepatic vein (two), and internal jugular vein (one). Catheter tip position within the right ventricle correlated with a significantly higher incidence of electrical capture when compared with other catheter tip locations (P less than .004). There was a significantly higher incidence of successful placement into the right ventricle when an internal jugular, rather than a subclavian venous, access route was used (P less than .004). Only one of 36 patients was resuscitated successfully; none lived to be discharged from the hospital. Misplacement of the catheter tip may contribute to the poor success rate of transvenous pacing during CPR. The internal jugular vein may be the access site of choice when transvenous pacing is attempted during chest compressions.(ABSTRACT TRUNCATED AT 250 WORDS)

Hemodynamics of transcutaneous cardiac pacing

Transcutaneous cardiac pacing has recently been rediscovered as a rapid means of initiating emergency cardiac pacing. Potential myocardial injury from extended transcutaneous pacing could adversely affect cardiac hemodynamics during pacing. This canine study compares the hemodynamics of transcutaneous and transvenous cardiac pacing in animals with induced chronic heart block. One to two weeks following chemical ablation of the His bundle, hemodynamic measurements were made during 60 minutes of transcutaneous and 5-minute periods of conventional right ventricular endocardial pacing. Cardiac index and output were found to increase significantly (P less than 0.005), and systemic vascular resistance was found to decrease significantly (P less than 0.005) from baseline values with both pacing techniques. A hemodynamic difference between pacing techniques was evident only for mean arterial blood pressure; pressure measurements during transvenous pacing were slightly greater than those during transcutaneous cardiac pacing. The hemodynamic measurements were found to be stable during a 60-minute period of transcutaneous cardiac pacing. This study demonstrates that transcutaneous cardiac pacing is as effective hemodynamically as conventional transvenous pacing in animals with induced chronic heart block.

A hemodynamic model for anaphylactic shock

The treatment of cardiovascular collapse and anaphylactic shock is largely empiric. A simple animal model was developed to evaluate the hemodynamic alterations in anaphylaxis. Eight adult New Zealand white rabbits of both sexes were studied. All animals weighed 3.8 kg to 5.3 kg. Sensitization was accomplished with a 2-mL subcutaneous dose of horse serum followed in two days with a 2-mL intravenous (IV) dose. At least 14 days elapsed after the IV dose before a 1-mL challenge dose of horse serum was given. On the day of the challenge dose, a femoral arterial catheter, arterial temperature probe, and right atrial catheter were placed under methoxyflurane anesthesia. The temperature probe was positioned in the aortic arch. The methoxyflurane was discontinued and the only sedation given during the shock phase was IV diazepam (0.1 mg/kg to 0.5 mg/kg). At least 30 minutes after methoxyflurane was discontinued, the challenge dose of horse serum was given through the right atrial catheter. Before and during the shock phase cardiac rhythm, arterial pressure, and intravascular temperature were monitored continuously. Cardiac outputs (CO) were performed by a thermodilution technique using 0.8 mL room temperature saline injectate through the right atrial catheter. Temperature deflection of the aortic probe was recorded and cardiac output was calculated. After giving the challenge dose, CO was measured at three, five, ten, 15, 25, 35, 45, and 60 minutes. All eight animals showed a significant (P less than .0005) fall in CO, cardiac index, and blood pressure within three minutes. The fall in cardiac index was 50% or more in all animals. Two animals died as a result of shock.(ABSTRACT TRUNCATED AT 250 WORDS)

Emergency department use of transcutaneous pacing for cardiac arrests

Transcutaneous cardiac pacing is a rapid technique for pacing the heart using skin electrodes to pass repetitive electrical impulses through the thorax. This paper reports the results of transcutaneous pacing in a series of 52 emergency department patients. Patients were selected for pacing if they were unconscious and in asystole (30 patients) or unconscious with a pulseless or hemodynamically ineffective bradycardia (22 patients). In all cases, transcutaneous pacing was attempted after initial resuscitative drug therapy failed. Of the 26 patients with successful ECG capture, 14 were initially in asystole, 11 were initially in a pulseless bradycardia, and one had a hemodynamically ineffective bradycardia. Of the eight patients developing a pulse, four developed a measurable BP. The four patients who developed a measurable BP were young (ages 22 to 39 yr) and only one had an underlying cardiac etiology for his cardiac arrest. No patient survived to be discharged from the hospital. Twenty-five of the 52 patients also had a transvenous pacemaker inserted, with successful electrical capture in five of the patients. Only one of the transvenously paced asystolic patients subsequently developed a BP. There were no patients successfully paced transvenously who were not successfully paced transcutaneously.

Pathological aspects of transcutaneous cardiac pacing

Although electrical energy has the potential to produce myocardial injury, the risk of tissue damage from transcutaneous cardiac pacing is largely unknown. This study reports the anatomical findings of a canine transcutaneous stimulation study. Ten dogs had 100-mA, 20-msec (pulse duration), transcutaneous impulses delivered across the thorax for 30 minutes at a rate of 80 stimuli per minute. Seventy-two hours later the animals were sacrificed, and the heart, lungs, and tissues of the chest wall were examined for pathological changes. Gross and microscopic lesions consistent with electrically induced myocardial damage were found in all hearts examined. These lesions included myocardial pallor and focal myofibril coagulation necrosis in the right ventricular outflow tract and perivascular microinfarcts in the posterior left ventricular myocardium. These lesions were not extensive; less than 5% of the right ventricular free wall and less than 1% of the left ventricular posterior wall were involved. Lesions of this extent would not be expected to cause clinically detectable changes in cardiovascular status. Short-term use of transcutaneous pacing appears to be safe. Determination of the potential for clinically significant injury with long-term use requires further study.