RESEARCH FORUM ABSTRACTS

19x300 vohage-time data array for each patient. Each matrix was factor analyzed to identify transformation coefficients and a minimum number of lead vectors spanning the entire 19-lead ECG and VCG data space.

Results: FA revealed 3 lead vectors accounted for 9886%-+0.57% of the variance of the voltage-time data for all 19 leads in this 27-patient data set. No statistically significant differences were noted between men (98.91%_+0.57%) and women (9872%-+0.57%) at P<.434 by analysis of variance testing. The 3 lead vectors spanning the data space were plotted to ymld 3-dimensional spatial variable curved surfaces defining the cardiac electri- cal activity for each patient.

Conclusion: A 3-lead-vector dipolar system is the major contribution to cardiac electrical activity. Both the 16-lead scalar ECG and 3-lead VCG may be derived from only 3 measured ECG leads. The information content of all 19 leads may be repre- sented by a 3-dimensional spatial ECG. This type of data processing may lead to instan- taneous acquisition of the ECG and VCG from telemetry equipment. Further studies are warranted for process validation.

3 Intraoral Sonography of Peritonsillar Abscesses: Feasibility and Sonographic Appearance

O'Brien E, Valley VT, Summers RUUniversity of Mississippi Medical Center, Jackson, MS

Study objective: To determine the feasibility of using intraoral uhrasonography (IOU) for detecting peritonsillar abscesses (PTA) in an emergency department setting. The sonographic appearance of confirmed abscesses was examined for characteristics that may aid in the differentiation between PTA and peritonsdlar cellulitis

Methods: A convenience sample of stable patients presenting to a university-based tertiary care ED with clinical evidence of PTA. Patients received topical anesthetic spray to the oropharynx and were imaged in a sitting position with a 6 5-MHz mtracavitary probe (Siemens, Sonofine Prima) covered with a sterile condom. Patients were not excluded by the presence of trismus. Emergency physicians performed all IOU studies. Verbal consent was obtained and data collected during the clinical evaluation of the patient. Subsequently, computed tomography (CT), fine-needle aspiration (FNA), and/or surgical drainage obtained confirmation of PTA.

Results: Intraoral sonograms were performed in 15 patients Nine patients had confirmed abscesses. Sl,x abscesses were confirmed by FNA alone. Two cases were demonstrated by surgical drainage after FNA with the remaining case by surgical drainage after CT. Hard copy video photographs were reviewed by a registered diagnostic medical sonographer with PTA categorized as homogeneous or cystic in appearance. In addition, the presence or absence of posterior acoustic enhancement (PAE) was determined. Six of the 9 confim~ed abscesses were described as cystic with the remaining 3 being homogenous in appearance. PAE was the most common feature noted in all confirmed abscesses (9/9)

Conclusion: Intraoral sonography of PTA is feasible to perform in an ED setting. IOU is easily accessible, noninvasive, and well-tolerated by all subjects despite trismus. PAE is an important sonographic feature of PTA being present m all confirmed PTA. In addi- tion, not all the confirmed abscesses were cystic m appearance. Further study is merited m use of this imaging modafity as it may provide clinically useful information especially in screening peritonsillar cellulitis versus PTA by the presence or absence of PAE.

O A A Prospective Study of the Accuracy and Reliability of Urine Dipsticks

groderk KB, Moscati RM, Filice M, Lereer EB, Hilander S/University at Buffalo, State University of New York, Erie County Medical Center, Buffalo, NY

Study objective: To assess the accuracy and reliability of the emergency department visual urine dipstick, an ED machine-read colorimeter device, and laboratory analysis in detecting urinary infection in comparison with urine culture.

Methods: A prospective study of ED patients who had urine testing done during a 10-month period was conducted. Excluded were those younger than 18 years, prison- ers, those currently being treated for urinary tract infection, and those who could not consent to participation. Urine samples were collected by random, clean catch, or catheterization. The samples were then analyzed by ED visual dipstick, ED use of the Bayer Clinitek 50, laboratory Clinitek 200 dipstick reading, laboratory microurinalysis, and bacteriology urine cultures. Dipstick and Cfinitek results were considered positive if any of the following were present: leukocyte esterase, nitrites, RBCs, or protein. The microurinalysis was considered positive if more than 5 WBCs were present. The urine culture was considered positive if 103 colony-forming units of any organism were pre- sent. The culture was considered contaminated if 3 or more organisms were grown from the sample. Sensitivity and specificity calculations along with negative predictive value calculations were made using the bacteriology urine culture as the gold standard.

Results: One hundred forty-two patients were enrolled in the study; of these 119 patients had complete data. Compared with the urine culture, the ED visual dipstick had a sensitivity of 91% (95% confidence interval [CI] 86% to 96%), specificity of 26% (95% CI 18% to 34%), and negative predictive value of 83% (95% CI 76% to 90%); the ED Clinitek 50 had a sensitivity of 91% (95% CI 86% to 96%), specificity of 24% (95% CI 16% to 32%), and negative predictive value of 81% (95% C1 74% to 88%); the laboratory Clinitek dipstick had a sensirivity of 79% (95% CI 72% to 86%), a specificity of 33% (95% C[ 24% to 42%), and a negative predictive value of 71% (95% CI 63% to 79%); the laboratory microurinalysis had a sensitivity of 60% (95% CI 51% to 69%), a specificity of 68% (95% CI 59% to 77%), and a negative predictive value of 72% (95% CI 64% to 80%).

Conclusion: The ED visual dipstick had the highest sensitivity and negative predic- tive values when compared with the urine culture of all 4 methods measured, making the ED visual dipstick the best screening test for urinary infection.

5 Criteria for Analyzing Flexion/Extension Radiographs of the Cervical Spine

Parker JS, Tashjian J, Knopp RK, Ganz W/Regions Hospital, St. Paul, MN

White's classic 1975 study suggested that 3.5 mm of intervertebral subluxation (SL) and/or _>I 1 degrees of angulation indicated celwical spine instability. These values were derived from cadaveric models of cervical spine instability These criteria have not been validated in a clinical setting.

Study objective: To determine the range of SL, vertebral angulation (VA), and rote> spinous distance (ISD) in flexion and extension as compared with neutral position (NP) in normal volunteers and to establish a reference standard to use in evaluation of flexion/extension views of the cervical spine.

Methods: We performed 3 view standardized NP, flexion, and extension cervical spine radiographs on healthy male volunteers ages 18 to 40 to determine ISD and SL at each level from C3-C4 to C6-C7. VA between C3 and C7 was also measured.

Results: One hundred volunteers were enrolled in the study. SL during flexion was greater than 2 mm in none of the 100 participants at each intervertebral level from C3 to C7 (95% confidence interval [CI] 0 to 3.62); SL in extension was greater than 2 mm in 1 of 100 participants at 1 level (C3-C4, 95% confidence interval [CI] 0 to 5.45) and none of 100 at each of the remaining 3 levels C4-C7 (95% CI 0 to 3.62). ISD and VA were also analyzed

Conclusion: Among the 3 variables--SL, ISD, and VA--SL appears to hold the most promise for being a useful reference standard in rhe clinical setting. Our results indicate that a finding of up to 2 mm of subluxation on fie:don-extension radiographs may be found in a normal population. Further clinical studies are needed on patients with pain or suspected cervical injury to see if a finding of >2 mm subluxation correlates with cervical spine instability. In our study, the variation in vertebral angulation and mterspinous distance in a normal population was too great to define normal criteria.

6 Can Venous Blood Gas Measurements Be Used in Place of Arterial Blood Gas Determinations in Emergency Department Patients?

Sexton JD, Ravanzo J/St Luke's Hospital, Emergency Medicine Residency of the Lehigh Valley, Bethlehem, PA

Study objective: The correlation between arterial and venous blood gas (VBG) measure- ments has not been investigated in ED patients. Our ultimate objective is to determine the utility of VBG measurements in ED patients with exacerbation of chronic obstruc- tive pulmonary disease; this preliminary study attempted to establish the correlation of arterial blood gas (ABG) and VBG values as measured in our community hospital.

Methods: We retrospectively compared ABG and VBG values obtained in unselected ICU patients who had venous and arterial samples drawn simufianeonsly. All venous blood samples were from peripheral sites as were all arterial samples. All standard ABG paranreters (Po2, pH, Pco2, and PHCO 3) were analyzed using the Pearson method.

Results: For the entire group (n=72), the correlation between venous and arterial Pco2, pH, and PHCO 3 were r2=0.96, 0.97, and 0.97, respectively (P<.05). Correlation with Po 2 was poor (r2<0.18, P>.5). Data from patients in the following subgroups were analyzed: (1) Pao2<100 (n=46); (2) Pao2<70 (n=25); (3) Pvo2<35 (n=41); (4) Pco2>35 (n=35), and (5) Pc%>50 (n=6). Correlation for all measurements was high with r2>0.95 (P<.05), with the exception of P% (r2<0.90).

Conclusion: ABG measurements of Pco2, pH, and PHCO 3 (but not Po2) can be accurately predicted from peripheral VBG studies in 1CU patients with widely varying levels of Pao a and Paco 2. Applicability of this finding to selected patients in the ED would have considerable clinical utility but requires confirmation.

S 26 ANNALS OF EMER6ENCY MEDICINE 34:4 OCTOBER 1999, PART 2