Two-thumb vs. two-finger chest compression in an infant model of prolonged cardiopulmonary resuscitation.

OBJECTIVE: Previous experiments in the authors' swine lab have shown that cardiopulmonary resuscitation (CPR) using two-thumb chest compression with a thoracic squeeze (TT) produces higher blood and perfusion pressures when compared with the American Heart Association (AHA)-recommended two-finger (TF) technique. Previous studies were of short duration (1-2 minutes). The hypothesis was that TT would be superior to TF during prolonged CPR in an infant model. METHODS: This was a prospective, randomized crossover experiment in a laboratory setting. Twenty-one AHA-certified rescuers performed basic CPR for two 10-minute periods, one with TT and the other with TF. Trials were separated by 2-14 days, and the order was randomly assigned. The experimental circuit consisted of a modified manikin with a fixed-volume arterial system attached to a neonatal monitor via an arterial pressure transducer. The arterial circuit was composed of a 50-mL bag of normal saline solution (air removed) attached to the manikin chest plate and connected to the transducer with a 20-gauge intravenous catheter and tubing. Rescuers were blinded to the arterial pressure tracing. Systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial pressure (MAP) were recorded in mm Hg, and pulse pressures (PPs) were calculated. Data were analyzed with two-way repeated-measures analysis of variance. Sphericity assumed modeling, with Greenhouse-Geisser and Huynh-Feldt adjustments, was applied. RESULTS: Marginal means for TT SBP (68.9), DBP (17.6), MAP (35.3), and PP (51.4) were higher than for TF SBP (44.8), DBP (12.5), MAP (23.3), and PP (32.2). All four pressures were significantly different between the two techniques (p< or =0.001). CONCLUSION: In this infant CPR model, TT chest compression produced higher MAP, SBP, DBP, and PP when compared with TF chest compression during a clinically relevant duration of prolonged CPR.

The psychometric and cardiac effects of pseudoephedrine in the hyperbaric environment.

STUDY OBJECTIVES: To examine the psychometric and cardiac effects of pseudoephedrine at 1 and 3 atmospheres (atm) of pressure (0 and 66 feet of sea water, respectively), and to make recommendations about the agent's safety in the diving environment. DESIGN: Double-blind, placebo-controlled, crossover study. SETTING: Monoplace hyperbaric chamber of a university hospital. SUBJECTS: Thirty active divers (mean age 38 yrs). INTERVENTION: A bank of seven tests was used to assess cognitive function during four different simulated dive combinations: placebo-1 atm, placebo3 atm, pseudoephedrine-1 atm, and pseudoephedrine-3 atm. MEASUREMENTS AND MAIN RESULTS: Heart rate and cardiac rhythm were recorded during all dives. Repeated-measures analysis of variance was used to analyze the effects of pseudoephedrine, depth, and drug-depth interaction. No significant, independent effects of pseudoephedrine were seen on any of the seven psychometric test scores (p>0.05), although the drug tended to increase anxiety scores (p=0.092). Depth resulted in a significant increase in anxiety scores (p=0.021) and a significant decrease in verbal fluency test scores (p=0.041); it had no significant effects on the other five psychometric tests (p>0.05). Pseudoephedrine caused a significant increase (p=0.036) in mean heart rate, and depth caused a significant decrease (p=0.013). Neither pseudoephedrine nor depth affected cardiac rhythm. CONCLUSION: Pseudoephedrine does not cause significant alterations in psychometric performance at 3 atm of pressure that might increase the risk of diving. Depth causes significant adverse effects on anxiety levels and semantic memory at 3 atm. Pseudoephedrine and depth have significant but opposite effects on heart rate; although, these effects are unlikely to be clinically significant during diving. It is unlikely that pseudoephedrine adds significant risk to the diver.

The psychometric and cardiac effects of dimenhydrinate in the hyperbaric environment.

STUDY OBJECTIVES: To examine the psychometric and cardiac effects of dimenhydrinate at 1 and 3 atmospheres (atm) of pressure (0 and 66 feet of sea water, respectively), and to make recommendations about the drug's safety in the diving environment. DESIGN: Double-blind, placebo-controlled, crossover study SETTING: Monoplace hyperbaric chamber of a university hospital. SUBJECTS: Thirty active divers (mean age 38 yrs). INTERVENTIONS: A bank of seven tests was used to assess cognitive function during four different dive combinations: placebo-1 atm, placebo-3 atm, dimenhydrinate-1 atm, and dimenhydrinate-3 atm. MEASUREMENTS AND MAIN RESULTS: Heart rate and cardiac rhythm were recorded during all dives. Repeated-measures multivariate analysis of variance was used to analyze the effects of dimenhydrinate, depth, and drug-depth interaction. Dimenhydrinate resulted in a significant decrease in scores of mental flexibility (trail-making, part B, p<0.05) but had no effect on scores in the six other psychometric tests (p>0.05). It had no effect on mean heart rate (p>0.05), although frequent unifocal ventricular ectopic beats occurred in two subjects after ingestion of the drug. Depth resulted in a significant decrease in verbal memory test scores (p=0.001) and mean heart rate (p<0.001). CONCLUSION: Dimenhydrinate adversely affects mental flexibility. This effect, when added to the adverse effect of depth on memory, may contribute to the dangers of diving.

Current outpatient management of asthma shows poor compliance with International Consensus Guidelines.

STUDY OBJECTIVE: This study aimed to establish whether the outpatient management of patients presenting with an asthma exacerbation to the emergency department (ED) was in compliance with the 1992 guidelines of the "International Consensus Report on the Diagnosis and Management of Asthma." DESIGN: Prospective, observational study using a researcher-administered questionnaire. SETTING: University tertiary referral ED. PATIENTS: Convenience sample of asthmatics (aged 18 to 54 years) presenting for asthma treatment between July 1, 1997, and June 30, 1998. RESULTS: Eighty-five asthmatic patients were enrolled. Of these, 34 patients (40%) smoked, 53 patients (62%) were undertreated with medication when compared to the consensus guidelines, and 74 patients (87%) had no written "plan of action." During an asthma attack, 9 patients (11%) did not use a bronchodilator as first-line action and 76 patients (89%) did not commence or increase the use of an inhaled steroid. Forty-nine patients (58%) did not know that bronchospasm occurred in asthma, and 53 patients (62%) did not know that bronchial swelling occurred. Twenty-six patients (31%) thought short-acting bronchodilator drugs were asthma preventers. Sixty-two patients (73%) could not adequately define peak expiratory flow (PF), 41 patients (48%) did not own a PF meter, and only 8 patients (9%) determined their PF daily. Fifty-three patients (62%) were reviewed by a physician once a year or less, and 18 patients (21%) noted family and friends as their only source of asthma education. CONCLUSIONS: The outpatient management of most asthma patients presenting to the ED did not comply with the consensus guidelines, and asthma knowledge was poor.

Assessing prognosis and selecting an initial site of care for adults with community-acquired pneumonia.

Over the last 20 years, more than 15 medical practice guidelines and clinical prediction rules have emerged to assist physicians in assessing the prognosis of adult patients with community-acquired pneumonia (CAP) and selecting an appropriately matched initial site of care. Most of these guidelines and rules suffer from major methodological flaws. One, the Pneumonia Patient Outcomes Research Team (PORT) clinical prediction rule, has satisfied rigorous methodological standards for the derivation and validation of high-quality prediction rules. This rule was incorporated into the Infectious Disease Society of America medical practice guideline for the management of adults with CAP. Strengths of the rule include its derivation and validation in over 50,000 inpatients and outpatients; stratification of all immunocompetent adult patients into one of five risk strata for short-term mortality and other unambiguous adverse medical outcomes; initial site of care recommendations for all patients, particularly those at low risk; and reliance on predictor variables readily available to clinicians at the time of initial patient presentation. A recent small-scale intervention trial demonstrates that the pneumonia PORT rule can reduce admissions for adult patients with CAP without compromising patient outcomes.

Comparison of bag-valve-mask, manually triggered ventilator, and automated ventilator devices used while ventilating a nonintubated mannikin model.

OBJECTIVE: To determine whether there were differences in tidal volume (Vt), minute volume (MV), average mask leak per breath (ML), gastric insufflation (GI), and peak airway pressure (PAP) when ventilating a nonintubated mannikin with a bag-valve-mask (BV), manually triggered ventilator (MTV), and automated ventilator (AV). The authors' hypothesis was that there would be no differences among the devices for any of these variables. METHODS: This was a prospective in-vitro experimental model. A convenience sample of 19 emergency medical technicians (EMTs) ventilated a nonintubated mannikin-mechanical test lung model with the BV, MTV (flow rate 40 L/min; pressure relief 55 cm H2O), and AV (800 mL/breath; rate 12). Each subject, blinded to volume and pressure gauges, used each device for 2 minutes at both normal (0.1 cm H2O) and poor (0.04 cm H2O) compliances. Vt, MV, GI, and PAP were measured directly and ML was calculated. A survey was issued to the EMTs who participated in the study. Data were analyzed with repeated-measures ANOVA and the Bonferroni-Dunn multiple comparison test with alpha set at 0.05. RESULTS: At the normal compliance, PAP was higher for the BV than the MTV (p = 0.0001) and AV (p < 0.0001). MV was also greater with the BV than with the AV (p = 0.001). PAP was also higher at the poor compliance with the BV than with the MTV and AV (p = 0.008 and 0.013, respectively). The BV had a higher GI at this compliance (p < 0.0001) and a higher ML than the AV (p = 0.002). CONCLUSION: All three devices delivered similar volumes when used by EMTs, but the BV was associated with higher PAP, ML, and GI.

Use of automated external defibrillators by police officers for treatment of out-of-hospital cardiac arrest.

OBJECTIVE: To determine the feasibility of police officers providing defibrillation with automated external defibrillators (AEDs) and to assess the effectiveness of this strategy in reducing time to defibrillation of victims of out-of-hospital sudden cardiac arrest. METHODS: This was a prospective, interventional cohort study with historical controls conducted in 7 suburban communities in which police usually arrived at the scene of medical emergencies before EMS personnel. All adult patients who suffered cardiac arrest before EMS arrival and on whom EMS personnel attempted resuscitation were enrolled. Police officers who were trained to use and equipped with AEDs during the intervention phase were dispatched simultaneously with EMS to medical emergencies. Police were instructed to use the AED immediately on determination of pulselessness. Outcome measures were the difference between control and intervention phases in interval from the time the call was received at dispatch to the time of first defibrillation and in rate of survival to hospital discharge for patients initially in ventricular fibrillation. RESULTS: EMS personnel attempted 183 resuscitations in the control phase and 283 during the intervention; of these, 80 (44%) and 127 (45%), respectively, involved patients with initial ventricular fibrillation rhythms. Mean time to defibrillation decreased from 11.8+/-4.7 minutes in the control phase to 8.7+/-3.7 minutes in the intervention phase (P<.0001). Survival to hospital discharge of patients in ventricular fibrillation did not differ between phases (6% control versus 14% intervention, P=.1). When police arrived before EMS personnel, shock administered by police compared with shock administered by EMS was associated with improved survival (26% [12/46] versus 3% [1/29], P=.01). Logistic regression analysis revealed AED use was an independent predictor of survival to hospital discharge. CONCLUSION: In 7 suburban communities, police use of AEDs decreased time to defibrillation and was an independent predictor of survival to hospital discharge.

Comparison of automated and manual ventilation in a prehospital pediatric model.

OBJECTIVE: Portable transport ventilators (TV) and demand valves (DV) may be effective and easy-to-use alternatives to bag-valve (BV) for prehospital ventilation of adults. The purpose of the study was to determine whether such devices maintain arterial blood gases and airway pressures similar to those for BV in a pediatric swine model. METHOD: This study was a prospective, randomized, crossover design using immature swine (9.6 +/- 0.9 kg) to model ventilation in small children. Anesthetized, intubated, paralyzed, and cannulated animals were ventilated initially on standard mechanical hospital ventilation (HV). They were then assigned in random order to 10-minute intervals of ventilation using BV, TV, low-frequency jet ventilation (JV), and DV. Data were analyzed using repeated-measures ANOVA and Tukey multiple comparisons (alpha = 0.05). RESULTS: The PaO2 exceeded 90 mm Hg for all animal/ventilation combinations. Blood PaCO2 was lower for BV and DV than it was for TV, JV, or HV. In contrast, blood pH was higher for BV and DV than it was for TV, JV, or HV. Peak airway pressure was higher for BV than it was for HV, TV, or JV; it was lower for JV than it was for HV, TV, or BV. CONCLUSION: This animal model suggests that automated TV and JV may provide more effective ventilation of children than do manual BV or DV devices. Although promising, these findings require application in children under prehospital emergent conditions.

Effectiveness of 50% nitrous oxide/50% oxygen during laceration repair in children.

OBJECTIVE: To determine the effect of an inhaled 50% nitrous oxide/50% oxygen mixture on measures of observed anxiety in children during laceration repair. METHODS: A prospective, randomized, placebo-controlled, double-blind comparison of an inhaled 50% nitrous oxide/50% oxygen mixture (treatment group) with 100% oxygen (control group) during repair of lacerations was performed. The study population was a convenience sample of children aged 2-7 years in an urban pediatric ED. The primary outcome variable was the change in scores before and during laceration repair with a 10-point modified Children's Hospital of Eastern Ontario Pain Scale (CHEOPS) assessment. The secondary outcome variable was a 4-point anxiety scale measured before and during the procedure. RESULTS: Thirty patients were entered into the study. Seventeen children inhaled the 50% nitrous oxide/oxygen mixture and 13 inhaled 100% oxygen during laceration repair. There was no statistically significant difference in initial CHEOPS and anxiety scores between the 2 groups (p = 0.687 and 0.809, respectively). The median CHEOPS scores in the treatment group decreased by 5 points, while those of the control patients increased by 3 (p < 0.001). The median anxiety scores in the treatment population decreased by 1 point, with an increase of 1 for the control patients (p < 0.001). CONCLUSION: Administration of a 50% nitrous oxide/50% oxygen mixture to children during their laceration repair resulted in a significant decrease in measures of anxiety when compared with inhalation of 100% oxygen.

Law enforcement agencies and out-of-hospital emergency care.

STUDY OBJECTIVE: We sought to assess the involvement of law enforcement agencies in out-of-hospital emergency medical care and their attitudes toward expanded roles in emergency medical services (EMS) systems. METHODS: We mailed a 20-question survey to 800 police chiefs and sheriffs randomly selected from a list of all law enforcement agencies in the United States. The questions focused on the characteristics of each law enforcement agency, its current level of involvement in providing out-of-hospital emergency medical care, and the characteristics of its associated community and local EMS system. The survey concluded with four statements to assess officer attitudes toward an expanded role in EMS-related activities. We used the chi 2 or Fisher exact test to analyze differences in proportions. The alpha-error rate was set at .05. RESULTS: Seventeen surveys were returned as undeliverable. Of the remaining 783 surveys, we received 602 responses (77%). Five hundred forty-nine (70.1%) of the respondents were the primary law enforcement agencies in their communities; they make up the final sample. The median number of officers per agency was 12 (range, 1 to 2,623), and the median population served was 6,936 (range, 150 to 1,500,000). Responses indicated that 442 (80.7%) agencies responded to one or more specific types of medical emergencies and 263 (50.3%) provided some level of patient care. Law enforcement officers frequently arrived at the scene of medical emergencies before EMS personnel (81.5%), with a roll-time interval of less than 8 minutes (87.2%). Only 14 agencies (2.6%) used automatic external defibrillators. Fifty-three percent agreed with the statement that EMS-related activities would interfere with their law enforcement duties. However, more than 60% of respondents agreed that law enforcement agencies should be involved in providing emergency medical services for life-threatening emergencies, that their officers would be willing to undertake extra medical training and that EMS-related activities would improve their public images. CONCLUSION: Many law enforcement agencies are involved to some extent in providing out-of-hospital emergency medical care, and most of the agencies we surveyed would support additional medical training and new or expanded roles for themselves in EMS systems.

A prediction rule to identify low-risk patients with community-acquired pneumonia.

BACKGROUND: There is considerable variability in rates of hospitalization of patients with community-acquired pneumonia, in part because of physicians' uncertainty in assessing the severity of illness at presentation. METHODS: From our analysis of data on 14,199 adult inpatients with community-acquired pneumonia, we derived a prediction rule that stratifies patients into five classes with respect to the risk of death within 30 days. The rule was validated with 1991 data on 38,039 inpatients and with data on 2287 inpatients and outpatients in the Pneumonia Patient Outcomes Research Team (PORT) cohort study. The prediction rule assigns points based on age and the presence of coexisting disease, abnormal physical findings (such as a respiratory rate of > or = 30 or a temperature of > or = 40 degrees C), and abnormal laboratory findings (such as a pH <7.35, a blood urea nitrogen concentration > or = 30 mg per deciliter [11 mmol per liter] or a sodium concentration <130 mmol per liter) at presentation. RESULTS: There were no significant differences in mortality in each of the five risk classes among the three cohorts. Mortality ranged from 0.1 to 0.4 percent for class I patients (P=0.22), from 0.6 to 0.7 percent for class II (P=0.67), and from 0.9 to 2.8 percent for class III (P=0.12). Among the 1575 patients in the three lowest risk classes in the Pneumonia PORT cohort, there were only seven deaths, of which only four were pneumonia-related. The risk class was significantly associated with the risk of subsequent hospitalization among those treated as outpatients and with the use of intensive care and the number of days in the hospital among inpatients. CONCLUSIONS: The prediction rule we describe accurately identifies the patients with community-acquired pneumonia who are at low risk for death and other adverse outcomes. This prediction rule may help physicians make more rational decisions about hospitalization for patients with pneumonia.

Field termination of unsuccessful out-of-hospital cardiac arrest resuscitation: acceptance by family members.

STUDY OBJECTIVE: To determine whether family members accept field termination of unsuccessful out-of-hospital cardiac arrest resuscitation. METHODS: We carried out a prospective cohort study, using a structured interview, in an urban, municipal, advanced life support emergency medical services (EMS) system. The interview subjects were family members present at the scene in a consecutive series of unsuccessful out-of-hospital resuscitation attempts. RESULTS: During the 4-month study period, 140 out-of-hospital cardiac arrests occurred. Follow-up with a family member was performed in 42 of the 53 cardiac arrests that met the inclusion criteria (79%). When resuscitation was terminated in the field (n = 25), 24 family members (96%) reported satisfaction with the decision. When resuscitation was terminated in the emergency department (n = 17), 14 family members (82%) reported satisfaction with the decision to transport the victim to the hospital. However, responses indicated that 13 of the family members (76%) might have accepted termination of resuscitation in the home. In all cases, relatives reported satisfaction with the paramedics' care and with the manner in which they were informed of the victims' deaths. CONCLUSION: Family members accept termination of unsuccessful out-of-hospital cardiac arrest resuscitation in the field.

Functional outcome of patients with unstable pelvic ring fractures stabilized with open reduction and internal fixation.

An unstable pelvic ring fracture represents a severe injury and is associated with high morbidity and mortality. Little data are available assessing the long-term functional limitations, including disability, in a patient with an unstable pelvic ring fracture. The purpose of this study was to describe the impairment and functional outcome (disability) for patients with unstable pelvic ring fractures managed with open reduction and internal fixation (ORIF). Disability was measured at a minimum of 1 year postinjury using the Sickness Impact Profile (SIP), a measure of the health-related quality of life as perceived by the patient. Of the 230 consecutive patients with a pelvic ring fracture, 54 had unstable fractures requiring ORIF; 48 patients were available at a 1 year follow-up. The follow-up roentgenograms confirmed an osseous union and an anatomic alignment of the pelvis. Thirty-seven (77%) of the patients had mild disability (total SIP < 10); 11 (23%) of the patients had moderate disability (SIP > 10) at 1 year. Of the patients who were employed preinjury, 76% were employed 1 year postinjury; 62% had returned to full time work and 14% had returned with job modification. Of the 7 patients who had been in school, 6 had returned full time and 1 student returned part time. Mean SIP scores for subcategories were: physical health = 6.8 +/- 9.4, psychosocial health = 7.4 +/- 12.7, work = 17.6 +/- 25.5, home management = 8.3 +/- 13.0, ambulation = 10.7 +/- 13.7, and mobility = 5.3 +/- 13.0. Despite the magnitude of the bony injuries, the majority of patients with unstable pelvic ring fractures managed with ORIF had mild disability 1 year postinjury; the majority of the patients had returned to work.

Effect of out-of-hospital defibrillation by basic life support providers on cardiac arrest mortality: a metaanalysis.

STUDY OBJECTIVE: Although some studies demonstrate otherwise, we hypothesized that metaanalysis would demonstrate a reduction in the relative risk of mortality when basic life support (BLS) providers can defibrillate out-of-hospital cardiac arrest patients. DESIGN: Metaanalysis of studies meeting the following criteria: single-tier or two-tier emergency medical service (EMS) system, survival to hospital discharge for patients in ventricular fibrillation, and manual and/or automatic external defibrillators. The alpha error rate was .05. RESULTS: Seven trials qualified for metaanalysis. Across all trials, the risk of mortality for BLS care with defibrillation versus that without was .915 (P = .0003). Separate subset analyses of single-tier and two-tier EMS systems demonstrated similar results. CONCLUSION: BLS defibrillation can reduce the relative risk of death for out-of-hospital cardiac arrest victims in ventricular fibrillation. Weaknesses in individual study designs and regional clustering limit the strength of this metaanalysis and conclusion.

Recovery from severe cyclic antidepressant overdose with hypertonic saline/dextran in a swine model.

OBJECTIVE: To determine the effect of a hypertonic saline and dextran (HSD) solution on blood pressure and QS duration during severe cyclic antidepressant (CA) toxicity in swine. METHODS: Ten domestic swine weighing 20-24 kg were anesthetized and placed on mechanical ventilation. Nortriptyline solution was infused intravenously to achieve hypotension (systolic blood pressure equal to 50% of baseline) and a QRS duration of 120 msec. After reaching toxicity, the animals received in a randomized fashion either 10 mL/kg of a 7.5% saline/6% dextran solution or an equal volume of 0.9% saline as a rapid intravenous bolus. The animals were observed for one hour or until they died. Blood pressure and ECG were recorded continuously. Arterial pH was maintained in the physiologic range by controlled ventilation. RESULTS: Mean systolic blood pressure 10 minutes after treatment was 45 +/- 8 torr in the normal- saline group compared with 115 +/- 12 torr in the HSD group (p < 0.05). Mean QRS duration 10 minutes after treatment was 180 +/- 8 msec in the normal-saline group; it was 88 +/- 13 msec in the HSD group (p < 0.05). All normal-saline--group animals died within 20 minutes, and four of the five animals in the HSD group survived to 60 minutes (p < 0.05). The mean peak sodium concentration was 157 mmol/dL (mEq/dL) in the HSD group, and this was transient. CONCLUSION: In this swine model of severe CA toxicity, a solution of 7.5% saline/6% dextran significantly reversed hypotension and QRS prolongation. HSD also improved survival to 60 minutes.

Are race, age, gender, and insurance status determinants in interhospital helicopter transport time and frequency?

OBJECTIVE: To examine the effects of age, race, gender, and insurance status on utilization and times-to-transport (TTT) for interhospital air medical transfers from rural hospitals to tertiary care centers. DESIGN: A retrospective review of interhospital transport records. The TTT was examined as a function of age, gender, race, and insurance status using the Student's t-test for unpaired samples. The Exact Binomial Test (alpha error at 0.05) was used to compare the observed versus expected transport rates for non-whites. SETTING/PARTITIPANTS: A total of 268 patient transfers from hospitals within a two-county region in central Pennsylvania to tertiary care centers was analyzed. All records with sufficient demographic, TTT, or insurance data were included. Absence of data was the only exclusion. RESULTS: The TTT (mean +/-SD) was longer (2666 +/-3940 minutes (min.) versus 619 +/-909 min., respectively) for adult than pediatric patients (p less than .01), and (2588 +/-4041 min. versus 640 +/-1301 min., respectively) for insured versus uninsured patients (p less than .01). The observed proportion of non-whites transported was less than expected (.41% versus 2.1%) based on the proportion of non-whites in the region (p less than .05). CONCLUSION: The TTT was longer for adults than for children and for the insured than the uninsured. Non-whites were transported less frequently than predicted.

A prospective evaluation of radiologic criteria for head injury patients in a community emergency department.

Several management strategies for radiographic evaluation of head-injury patients have been developed, most are based on retrospective analysis. The study attempted to prospectively evaluate the previously published Masters' criteria defining low-, medium-, and high-yield patients. A community hospital emergency department with a low prevalence of serious head injury was studied, and 1,000 consecutive patients 2 years of age presenting with historical or physical evidence of blunt head trauma were asked to participate; 967 consented. The patients were categorized by staff emergency physicians as low-, moderate-, and high-yield for intracranial injury on the basis of their initial history and physical examination. These categories guided imaging decisions in accordance with the guidelines of Masters. The patients were evaluated 6 weeks later by multiple questionnaire and/or telephone calls to determine whether or not undiagnosed head injuries had been missed. The 967 patients initially evaluated were classified according to their risk of intracranial injury as follows: 886 at low risk, 78 at moderate risk and 3 at high risk. Complete follow-up data were available for 895 of these patients (93%). Of the 895, 71 patients (7.9%) did report receiving follow-up medical care for their head injury; none had evidence of missed intracranial injury requiring intervention. Therefore, it can be inferred with a 95% confidence interval that 0.4% or less of patients who were diagnosed as not having intracranial injuries requiring intervention may actually have such injuries. The application of Masters' management strategy in low-risk populations permits clinicians to safely reduce the number of radiographs ordered for patients with head injury.