ABSTRACTS

lators. They were then instrumented with right and left heart catheters, a right ventricu- lar pacing electrode, and an airway flow mea- suring device. The pigs' neurologic status was assessed using a standardized scale. The animals were allowed to partially recover from anesthesia and to spontaneously venti- late before ventricular fibrillation was electri- cally induced. Four minutes later, chest com- pressions were begun with a mechanical device. At this time, animals were assigned to one of two treatment groups: the A group received positive-pressure ventilation at a 1:5 ratio to compressions, and the B group received 100% oxygen with no measurable increase in airway pressure. The B group was oxygenated by passive diffusion, the effects of the chest compressions, and the sponta- neous gasping that takes place during car- diopulmonary resuscitation (CPB). Twelve minutes into the arrest, up to two 300-J defibrillation attempts were made, followed by up to three 30-second cycles of compres- sions and an additional 300-J shock. The sur- viving animals then were ventilated and observed for 3 hours, deinstrumented, and observed for an additional 48 hours. The authors found that the two groups did not significantly differ in either resuscitation suc- cess (A group, 7 of 11 animals; B group, 8 of 11 animals) or 48-hour survival rate. Although blood gas parameters such as pH, arterial partial pressure of carbon dioxide, and arteri- al bicarbonate concentration differed signifi- cantly after 8 minutes of compressions, arte- rial partial pressure of oxygen did not. Blood gas parameters in the two groups were not different in animals that survived resuscita- tion. Peffusion measures such as mean aortic pressure, cardiac index, heart rate, and serum lactate level did not differ after successful resuscitation. The laboratory conditions in this study guaranteed a patent airway and delivery of 100% oxygen at a nonventilating pressure. The authors concluded that the combination of precordial compression and spontaneous gasping may have generated sufficient minute volume during cardiac arrest to account for the lack of difference between the groups.

[Editor's note: Although the authors believe that the data show the adequacy of gasping respirations in this setting, it remains to be seen whether the animals would have sur-

vived with a 21% fraction of inspired oxygen. The authors also reported arterial blood gas data that probably better reflect aortic envi- ronment than tissue hypoxia; the latter may be better assessed with mixed venous sam- pies. Other authors have shown that intuba- tion is not a prerequisite for successful resuscitation. A recent study in Annals of Emergency Medicine (Berg et al, The need for ventilatory support during bystander CPR. September 1995;26:342-350) uses a similar experimental design but with an initial downtime of 2 minutes, room air, manual CPR with and without ventilations for 10 minutes, and advanced cardiac life support resuscitation algorithms. The group without ventilatory support also had their endotra- cbeal tubes removed. Again, in this some- what more realistic setting, no significant difference was seen between the two groups in neurologic outcome or overall survival, and only a transitory difference was observed in arterial blood gas values during resuscitation. However, all studies to date have been animal studies with small numbers of subjects.]

William Lober, MD

Penicillin-resistant Streptococcus pneumoniae in acute otitis media: Risk factors, susceptibility patterns, and antimicrobial management Block SL, Harrison C J, Hedrick JA, et al

Pediatr Infect Dis J 14:751-759 September 1995

This study was designed to investigate the prevalence of penicillin-resistant Streptococcus pneumoniae (PBSP) in a three- county area in Kentucky. The patients evalu- ated in this study were healthy, predominant- ly white children, aged 2 months to 15 years, from a private pediatric population, who visited one of two pediatric offices between January 1992 and January 1994 and consent- ed to the study. Cultures were obtained from children using tympanocentesis (90%), spon- taneously ruptured tympanic membranes

(5%), or tympanostomy tubes that were already draining (less than 24 hours; 4%). There were approximately 10,000 visits dur- ing this 2-year period by children with the diagnosis of acute otitis media (AOM). Overall, 283 pathogens were recovered from 246 patients. PRSP accounted for 48% of all pneumococcal isolates. This group was fur- ther divided into highly PRSP and relatively PRSP organisms. ~-Lactamase production was detected in all Moraxella catarrhalis and 38% of Haemophilus influenzae organ- isms. Otitis-prone condition and increasing number of antibiotic courses before the day of culture were independently predictive risk factors for PRSP. During a 24-month period, highly PRSP and relatively PRSP organisms accounted for 8% and 9%, respectively, of 283 ear pathogens and 15% and 16%, respectively, of 157 pneumococ- cal isolates from AOM. This 31% incidence of PRSP falls between the 17% incidence reported almost a decade ago in the United States and the 42% incidence recently reported from Israel. Highly PRSP strains were more commonly found in children younger than 25 months. The authors fur- ther report that highly PBSP organisms dis- played intermediate and even high levels of resistance to ceftriaxone and cefotaxime and high minimal inhibitory concentrations to most conventional oral antimicrobials for AOM. The authors recommend against sin- gle-dose ceftriaxone because indiscrimi- nate, widespread use of a single-dose regi- men may hasten resistance. Clavulanate has demonstrated in vivo synergism with amoxicillin against PRSP in preliminary data from an animal model. The authors conclude by recommending that first-line therapy should be high-dose amoxicillin (60 to 80 mg/kg per day) for outpatient, nontoxic young children with moderate to severe AOM Cases of AOM refractory to this ther- apy may be treated with amoxicillin-clavu- lanate at the above-mentioned amoxicillin dose. If PRSP is identified, then clindamycin orally (30 mg/kg per day)for 10 to 21 days or ceftriaxone (50 mg/kg per day) for 3 to 5 days may be appropriate.

[Editor's note: It is unclear from this study what the overall prevalence of PRSP is because only approximately 2% of patients

FEBRUARY 1996 27:2 ANNALS OF EMERGENCY MEDICINE 27 7

ABSTRACTS

with AOM in their pediatric practice took part.]

Douglas McOaniel, MD

Noninvasive ventilation for acute exacerbations of chronic obstructive pulmonary disease Brochard L, Mancebo J, Wysocki M, et al

N Engl J Med 333:817-822 September 1995

This prospective European study was de- signed to investigate noninvasive pressure- support ventilation in hospitalized patients with acute exacerbation of chronic obstruc- tive pulmonary disease (COPD), in compari- son with standard therapy. It is the authors' contention that in patients with COPD, non- invasive ventilation by face mask may be used in an attempt to avoid endotracheal intubation and the complications associat- ed with mechanical ventilation. Between September 1990 and November 1991, 85 patients were randomly and prospectively recruited from a larger group of 275 patients with COPD, all of whom were admitted to five intensive care units. The same specific inclusion and exclusion crite- ria were used by all five hospitals to enroll patients in the study. Patients were includ- ed if they had acute exacerbation with res- piratory acidosis but did not require imme- diate intubation. Patients assigned to the standard treatment group received oxygen limited to a maximal flow rate of 5 L/minute by nasal cannula in order to achieve an arterial oxygenation saturation higher than 90%. Medications included subcutaneous heparin, antibiotic agents, and bronchodilators. Patients assigned to the noninvasive group received the same medications as the patients in the standard treatment group, with the addition of non- invasive ventilation to provide an arterial oxygenation saturation higher than 90%. All the participating hospitals used the same noninvasive ventilation delivery appa- ratus. The primary outcome variable was the need for endotracheal intubation and mechanical ventilation at any time during the study. Thirty-one (74%) of the 42

patients in the standard treatment group required endotracheal intubation, compared with only 11 (26%) of the 43 patients in the noninvasive group. The results were consis- tent among the five centers. There were significant improvements in encephalopa- thy score, respiratory rate, partial pressure of arterial oxygen, and pH during the first hour of treatment in the noninvasive venti- lation group, whereas the opposite was found in the standard treatment group. The hospital stay was significantly longer in the group receiving standard treatment (35 days) than in the group receiving noninva- sive ventilation (23 days). The authors con- clude that the mortality rate was signifi- cantly reduced and hospital stay was significantly shortened with the use of non- invasive ventilation. They further conclude that, in light of the rapidly reversible nature of most episodes of acute decompensation and the presence of ventilatory failure rather than hypoxemic lung failure, the results of this and previous studies suggest that patients with acute exacerbations of COPD should benefit from this approach.

Douglas McDaniel, MD

Limiting cardiac evaluation in patients with suspected myocardial contusion fildes Jd, getlej TM, Manglano R, et al

Am Surg 61:832-835 September 1995

The evaluation of patients with suspected myocardial contusion can include serial ECGs, determinations of creatine phospho- kinase (CPK) and its MB isoenzyme, contin- uous cardiac monitoring, and radiologic imaging studies. The authors of this prospective study wanted to determine what subset of blunt trauma patients con- sidered at risk for myocardial contusion could safely undergo a limited cardiac eval- uation (specifically, admission ECG and 24 hours of cardiac monitoring). The patient population consisted of 100 people who had mechanisms of injury consistent with myocardial contusion: motor vehicle crash- es at more than 30 mph, falls of more than

30 feet, pedestrians struck by motor vehi- cles traveling at more than 30 mph, and home or industrial accidents in which myocardial injury was considered likely. All patients had a baseline ECG on admission. They were then assigned to one of two groups on the basis of the following crite- ria: (1) age, (2) hemodynamic stability, (3) results of baseline ECG, (4) history of heart disease, and (5) need for surgery or neuro- logic observation. Those patients with a normal ECG, hemodynamic stability (sys- tolic blood pressure greater than 100), no history of heart disease, and no need for surgery or neurologic observation and who were younger than 55 years old were assigned to group 1 (n=74). All other patients were assigned to group 2 (n=19). Group 1 patients, in addition to the admis- sion ECG, simply received 24 hours of con- tinuous cardiac monitoring. Group 2 patients had a full cardiac evaluation, including an admission ECG, at least 24 hours of cardiac monitoring, serial ECGs, cardiac enzyme determinations, and either a multigated angiography scan (MUGA) or two-dimensional echocardiography (ECHO). Cardiac evaluation was considered to be positive for myocardial contusion if one or more of the following were present: (1) ST- segment elevations, T-wave inversions, or conduction disturbances on serial ECGs; (2) significant arrhythmias on continuous car- diac monitoring; (3) one or more CPK-MB fractions greater than 4%; (4) right ventric- ular ejection fraction less than 40%, left ventricular ejection fraction less than 50%, or a regional wall motion abnormality on ECHO or MUGA. None of the patients in group 1 patients had cardiac complications that required treatment. There were no crossovers to group 2. Follow-up was obtained in 24% of group 1, and in all cases the ECG remained normal. None of these patients had complaints referable to a cardiac injury. Group 2 patients were so categorized for the following reasons: 9 (47.4%) had abnormal baseline ECGs, including Mobitz type I AV block, ST-seg- ment elevations, T-wave inversions, postin- farction patterns, or multiple premature ventricular contractions; 7 (36.8%) had a history of heart disease; 4 (21%) underwent laparotomy; 1 (.5%) was admitted for neu-

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