Electrocardiographic criteria for ventricular tachycardia in wide complex left bundle branch block morphology tachycardias

positive rate of 4.0% of patients in whom HIV status was unknown prior to presentation. Age, sex, and race were important factors, but on multivariate relative-risk regression, seropositivity was independently associated with age under 45, black or "other" nonwhite race, history of homosexuality (presumably male), and history of IV drug use. Penetrating trauma also was independently associated with positivity, but overdose of IV drug and "gynecologic presentation other than vaginal bleeding" were found to be statistically significant on univariate analysis. Previous blood transfusion did not correlate statistically with positivity. The hospital location in this study is "a primary source of emergency care for indigent patients from the surrounding predominantly black community." The author's discussion centered on the high number of patients who are HIV positive in the emergency setting and bemoans the lack of appropriate precautions taken by emergency personnel. The authors call for the use of universal precautions for all patients in the emergency setting. ]Editor's note: Inner-city emergency physicians are at high risk for exposure to the H I V virus; precaution m u s t be taken.] Jim Vayda, M D

left bundle branch block, ECG

E l e c t r o c a r d i o g r a p h i c c r i t e r i a for v e n t r i c u l a r t a c h y c a r d i a in w i d e c o m p l e x left b u n d l e branch block morphology tachycardias Kindwall KE, Brown J, Josephson ME Am J Cardiol 61:1279-1283 Jun 1988

Few morphologic criteria have been established to aid in the differentiation of supraventricular tachycardia (SVT) from ventricular tachycardia (VT) when the pattern of left bundle branch block is present. In a retrospective analysis, the 12-lead ECGs of 118 patients with wide-complex tachycardia exhibiting the left bundle branch block pattern were examined. One hundred thirteen of these subjects underwent electrophysiologic evaluation that proved 91 cases to be VT and 27 to be SVT. Four criteria were identified that appeared to distinguish the underlying mechanism as VT rather than SVT: an R wave in V 1 or V2 of more than 30 ms duration; any Q wave in V6; a duration of more than 60 ms from QRS onset to S wave nadir in V 1 or V2; and any notching of the downstroke of the S wave in V 1 or V~. The results showed each of these criteria to have specificities and predictive accuracies of more than 95%, with sensitivities of 36% to 63%. When the criteria were used such that criteria 1, 2, 3, or 4 was present, the sensitivity was 100% with a specificity of 89% and predictive accuracy of 96%. The fact that a large percentage of the study population actually had VT and that, of those patients with SVT, none were taking medications that could have prolonged their conduction times could possibly have skewed the results. Bruce Spears, M D 17:12 December 1988

Annals

calcium, ionized; CPR

C a r d i a c a r r e s t and blood ionized c a l c i u m levels Urban P, Scheidegger D, Buchmann B, et al Ann Intern Med 110-113 Jul 15,1988

The value of calcium administration during cardiac arrest is controversial, and the American Heart Association does not currently recommend its routine use. In this study, blood ionized calcium levels and pH values in 12 out-ofhospital cardiac arrests were compared with those of nine patients who suffered cardiac arrest in an intensive care unit or during surgery. Ionized calcium is the biologically active form. Hypocalcemia leads to decreased ventricular performance, peripheral vasodilatation, and decreased hemodynamic response to catecholamines. In the 12 out-ofhospital arrests, all were given CPR, and only two received IV drugs and were intubated. Blood samples were taken at least ten minutes after the arrest. In this group there was significant ionized hypocalcemia (mean ionized calcium levels of .67 -+ .22 mmol/L), but normal total calcium levels. There was a positive correlation between pH and ionized calcium levels. In the nine of the in-hospital arrest group, all were given full resuscitation and blood samples were taken within the first three minutes. Ionized and total calcium levels were normal in this group. There was no significant difference in ionized calcium levels when comparing survivors with those who died. This study documents moderate to severe ionized hypocalcemia in out-of-hospital cardiac arrests. The hypocalcemia is time dependent and correlates to metabolic acidosis. Possible mechanisms for this include the binding of free calcium to lactate because this has been shown to occur in vitro. Further studies are needed to determine if out-of-hospital and prolonged cardiac arrests will benefit from calcium administration. [Editor's note: These are important data on the use of calcium. Outc o m e studies would be a logical next step.] Tim Hutchison, M D

ceftriaxone, gonorrhea

C e f t r i a x o n e for t r e a t m e n t of u n c o m p l i c a t e d gonorrhea: Routine use of a single 1 2 5 - m g dose in a s e x u a l l y t r a n s m i t t e d d i s e a s e clinic Handsfield HH, Hook EW Sexually Transmitted Diseases 14:227-230 Oct-Dec 1987

A single 250-rag dose of ceftriaxone is a treatment of choice for uncomplicated gonococcal infections, including those caused by ~-lactamase-producing strains and those with chromosomally mediated antibiotic resistance. With

of EmergencyMedicine

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