To the Editor: We regret that we may have given the impression that we

endorse the use of verapamil in digitalis toxicity. We only wished to point out that the role of calcium channel block- ers in digitalis toxicity is not yet certain. Although ver- apamil has not been tested clinically, it may have efficacy in certain of digitalis-induced tachyarrhythmias. Specifically, digitalis-induced after potentials in Purkinje fibers, which are felt to be the mechanism for the generation of ventricu- lar ectopic beats, are markedly depressed by slow channel blockers. 1,2

Although there are reports of success with verapamil in digitalis toxicity, 3'4 we would agree with Dr Johnson that until more information is available, calcium channel block- ers be withheld from digitalis-toxic patients.

Jeffrey Sharff, MD Marc J. Bayer, MD Division of Emergency Medicine Oregon Health Sciences University Portland

1. Lazzara R, Scherlag B: Treatment of arrhythmias by blocking slow current, editorial. Arm Intern Med 93:19-21, 1980. 2. Rosen MR, Witt AL, Hoffman BF: Cardiac antiarrhythmic and toxic effects of digitalis. Am Heart J 89:319-399, 1975. 3. Storstein O, Landmark KH: Verapamil in treatment of atrial tachycardia with block. Acta Med Scand 198:483-488, 1975. 4. Bremner WF: Massive digoxin overdose. Br Heart 1 39:688-692, 1977.

Electrical Injuries To the Editor."

This letter is in reference to the article entitled "Electri- cal Injuries: Pathophysiology and Emergency Management," by Kobernick (11:633-638, November 1982). He states that the energy expended on a tissue by an electrical current is J = IRT (J = energy expended or work done on the tissue in joules; R = resistance of the tissue in ohms; and T = time duration that the electricity is applied in seconds). Actually J = IaRT is the correct form of this equation. However, a more instructive approach would be to use the form of Joule's law J = V2T/R where V is the electrical potential applied to the patient in volts. This is better because it uses only independent variables - - the voltage applied (a proper- ty of the source}, the time interval that the voltage is ap- plied, and the resistance of the tissue. The current, I, is not an independent variable because it depends on the resis- tance and the voltage (I = V/R).

The resistance of the tissue is certainly a property of the type of tissue, as discussed in the article, but it would also vary somewhat with the voltage in a manner to be de- termined empirically for the individual tissues because tis- sue is not always a good conductor and therefore doesn't

follow Ohm's law. (Ohm's law States that the resistance is independent of voltage for good conductors.} The resistance would also be expected to change as electrical damage is done and the cellular and chemical composition changes.

Gary A. Simpson, MD Texarkana, Arkansas

To the Editor: Dr Simpson's comments emphasize an important point:

that different body tissues are unpredictable conductors, and that electric current does not always course through the body via the route of least resistance. Even when the path of the current through the body is known, prediction of the tissues damaged is, at best, only a guess.

Marc Kobernick, MD, Assistant Professor Section of Emergency Medicine University of Arizona Health Sciences Center TUcson

Emergency C-Section To the Editor:

The following is an account of an emergency C-section performed in the emergency department. It represents a unique triage situation in which the mother was unsalvage- able and the fetus was questionably salvageable. As it turned out, the fetus survived and is developing normally, but the decision to remove it was one that should have tak- en place even if the fetal heart sounds were absent.

A 32-year-old woman was transported to the emergency depar tment by ambulance . She was approximate ly 32 weeks pregnant and was a victim of a self-inflicted (.38 cali- ber) gunshot wound to the right temple. On arrival (6:20

12:6 June 1983

AM) there was bleeding from the wound site and gray mat- ter was protruding. Respirations were agonal, and the pa- tient was assisted by a bag valve and an endotracheal tube. The blood pressure was 80/0 m m Hg and the pulse rate was 42 beats/min (BPM). The skin was cyanotic, and the pupils were fixed and dilated. There was no elicited or sponta- neous movement. The patient demonstrated no other signs of trauma. Using a doppler, fetal heart tones (FHT) were as- sessed at 75 BPM, with an irregular rhythm. The on-call obstetrician and pediatrician were called.

Despite a fluid challenge with a crystalloid, the patient's

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blood pressure was unobtainable and the Pulse rate was still 40 BPM. The FHT, which were being monitored contin- uously, had fallen to 50 irregular BPM. Because of the pend- ing demise of the patient and the evidence of fetal distress, the decision was made to perform a C-section in the emer- gency department (6:25 AM). Using a No. 10 scalpel blade and handle, a midline incision was made from the umbil- icus to the symphysis pubis. Once through the abdominal wall, the scalpel was also used to incise the uterine wall. After entry into the uterus was made, the incision was ex- tended cephalad and caudad, using the long and index finger to tent-up the thin uterine wall.

The fetus was quickly removed 7 minutes after the pa- tient arrived, the mouth and nose were suctioned with a bulb syringe, and the cord was clamped {6:27 AM). From this moment the attention was directed to the infant girl. The child was markedly cyanotic and had no spontaneous respirations or movement. The infant was quickly taken to another bed, suetioned, and intubated with a No. 3 endotra- cheal tube. The breath sounds were heard bilaterally but there was evidence of marked moist rales.

The pulse rate was 160 BPM and regular. Rectal tempera-

ture was 34 C and the child demonstrated some respiratory effort. The APGAR was 3 at the end of one minute (6:28 AM). Warm blankets and lights were used to maintain body heat, and a piece of stockinette was used as a cap to prevent heat loss from the head.

The obstetrician arrived and preparations were made for insertion of an umbilical line (6:29 AM).

The pediatrician arrived and blood gases and a dextrose stick determination were done from the umbilical cord of the infant (6:35 AM), The glucose was in the normal range and the blood gases on 100% 02 revealed a pH of 7.25, a PO2 of 257, and a PCOz of 19. An umbilical artery catheter was inserted and one-half the calculated bicarbonate dose was given over half an hour. The child was transferred to the intensive care nurse13~ , where she was treated for respiratory distress syndrome secondary to hyaline membrane disease.

At one and one-half months post partum, the baby girl was doing well, was gaining weight, and was soon to be discharged to her father's care. Ed Carlson, MD Doctors Medical Center of Modesto Modesto, California

Unsuspec ted Tension P n e u m o t h o r a x As a Hidden Cause of Unsuccessfu l Resusc i ta t ion

To the Editor: Tension pneumothorax is a medical emergency that, if

left untreated, is life threatening. The classical physical findings of diminished or absent breath sounds, tracheal de- viation, jugular venous distension, and hyperresonance may be subtle or absent. The following case illustrates this point.

A 33-year-old woman was brought by ambulance with a 10-day history of fever, cough, and right-sided chest pain. The patient also had a long history of paranoid schizophre- nia and had been refusing to eat or drink for at least several days.

Physical examination revealed a cachectic, pale, un- responsive patien_t who appeared to be markedly de- hydrated. Vital signs revealed a temperature of 40.56 C; pulse, 147/min; respirations, 34/min; and unobtainable blood pressure.

A central venous line was placed without difficulty in the right subclavian vein. Blood was drawn for laboratory eval- uation, and Narean ~ 0.4 mg and 50% dextrose 50 cc was given without change in the patient's status. Before further evaluation or treatment, the patient experienced cardiac ar- rest. She was noted to be in electromechanical dissociation. She was immediately intubated, with good breath sounds noted bilaterally, and external cardiac compressions were started. Bicarbonate, epinephrine, atropine, calcium, and continuous infusion of isoproterenol was started.

Because the patient appeared to be pale, the possibility of occult hemorrhage was evaluated by rectal examination and bilateral flank taps of the peritoneal cavity, both of which were negative.

Ten minutes into the arrest, jugular venous distension

was noted; because of the patient's lack of response to con- ventional resuscitative efforts, the possibility of pericardial tamponade and tension pneumothorax was entertained.

Perieardiocentesis was performed x 2 with 5 cc of blood aspirated. No improvement in the patient 's status was noted after the pericardiocentesis. The patient was ex- amined carefully for the presence of pneumothorax. Breath sounds were equal bilaterally; no intercostal bulging, tracheal shift, or increased resonance to percussion of the chest was noted. On the basis of the repeated physical ex- amination, the diagnosis of pneumothorax was excluded.

Electrolytes drawn prior to the respiratory arrest revealed the following: sodium, 177; chloride, 130; potassium, 5.2; HCO3, 20; BUN, 160; creatinine, 5.9; amylase, 600; and blood sugar, 265. After 45 minutes all resuscitative efforts were unsuccessful and the patient was pronounced dead. A post mortem chest film revealed a right tension pneumo- thorax and changes in the right lower lobe consistent with pneumonia.

Although the physical examination is of utmost impor- tance in evaluating and treating any patient, it has limita- tions, particularly in the case of pneumothorax. While this was a seriously ill patient, her unsuccessful resuscitation may well have been due to the presence of an undiagnosed tension pneumothorax. This possibility was considered, but ruled out on the basis of physical examination by several physicians. This error may be avoided during CPR if needle aspiration of the chest is performed when resuscitation is failing, and by obtaining a chest x-ray film during CPR on all patients. This could be accomplished by always perform- ing CPR on a table that accommodates x-ray cassettes, or

120/411 Annals of Emergency Medicine 12:6 June 1983