CORRESPONDENCE Opinions expressed in the Correspondence Section are those of the authors, and not necessarily of the Journal editors, ACEP, or UA/EM.

ABEM Examination Part II To the Editor:

More on the boards - - Being one of the authors of the %utrage" letters

recently published in these pages as a result of the written exam, and having recently taken the orals, I feel compelled to again address myself to your reader- ship on this subject.

As previously stated, I feel that the "negative psychological impact" of the large number of ex- perimental questions appearing on the written exami- nation was underestimated.

The oral exam, however, is quite a different ex- perience. I am happy to be able to say that, in my opinion, the format and content of the orals is excel- lent. It was obvious that much time and effort was ex- pended in constructing this examination and in train- ing examiners. The end product is something of which we may all be proud. The content is 100% clinical emergency medicine. The five individual and two mul- tiple patient encounters comprise eleven cases which covered a wide spectrum of typical obvious baited traps. The format and the training of examiners com- bine to produce about as realistic an experience of pa- tient care as could be hoped for outside the real thing. Unlike the written examination, I heard only one can- didate gripe about the examination (a specific exam- iner) and I experienced no apparent prejudice or com- munication problems with examiners myself. Indeed, I spoke with many candidates who, like myself, actually enjoyed taking the examination.

In closing, I would like to congratulate the t~oard and all those involved with the construction and administration of the oral exam for a .fine piece of work. It would seem that with a little resuscitation of the written examination we will have a vehicle for cer- tification which is relevant, comprehensive, and fair.

Philip Jacobs, MD Malibu, California

Mixed Venous Blood Gases To the Editor:

Mixed venous blood gas determinations, as dis- cussed in the article by Kazarian and Del Guercio (9:179-182, 1980), may be of limited value to emer- gency physicians treating trauma patients in shock.

The authors report tha t S'~O2 was a helpful parameter to monitor during the resuscitative, opera- tive, and immediate postoperative period. One must realize that the oxygen saturation of mixed venous blood declines in trauma patients because of reduced

cardiac output with increased tissue extraction of 02. Excluding tension pneumothorax, pericardial tampo- nade, or spinal injury, hypotension in trauma cases is most likely due to hypovolemia. Therefore, in this situation, S:¢O2 becomes a fair measurement of blood lOSS.

We are informed tha t the magni tude of the trauma in the survivors and nonsurvivors was similar. However, it must be concluded from the authors' data (by initial arterial pH and S v O 2 that the nonsurvivors had either lost more blood or had hemorrhaged for a longer duration. One wonders if initial pulse and blood pressure would have been just as valuable in rapidly determining the extent of hemorrhage.

The authors used both CVP lines and Swan-Ganz catheters for blood samples. The use of CVP blood may not be valid in such patients. The correlation between central venous 02 saturation and S~O2 is poor when shock is present. 1 This means that a potentially lengthy insertion of a pulmonary artery catheter, or reposi- tioning the CVP to the right heart, may be necessary. The emphasis in the emergency treatment of hypo- volemic shock from penetrating wounds should be rapid pulmonary and circulatory resuscitation and then surgery. Any time lost in superfluous tests or positioning or repositioning various catheters could conceivably delay definitive treatment. In addition, S~O2 may be no better than watching urine output in monitoring the patient's response to fluid therapy, and certainly is more expensive.

The authors state that S~Oe determinations were Valuable predictors of survival. A valuable test is one that will affect your diagnosis or modify your thera- peutic approach. To be able to predict which patients will or will not survive is not appropriate in such crit- ically injured individuals. The graph showing that the nonsurvivors had lower SvO2 values which never re- turned to normal seems to be stating the obvious. This was undoubtedly because they lost too much blood, hypotension persisted despite therapy, and they died. To ascertain tha t a patient may have entered an irreversible stage of shock can be of little use. In other words, in critical trauma patients a predictor of sur- vival may be reliable but it is seldom valuable.

Bruce Lipton, MD Emergency Department

Kaiser-Permanente Medical Center Bellflower, California

1. Scheinman MD, Brown MA, Rapaport E: Critical assess- ment of the use of central venous oxygen saturation as a mir- ror of mixed venous oxygen in severely ill cardiac patients. Circulation 40"165-172, 1969.

To the Editor: The article by Kazarian and Del Guercio should

be criticized on several statistical grounds. First, the authors present no data to demonstrate that the two patients groups compared, ie, survivors and nonsurvi-

82/597 Ann Emerg Med 9:11 (November) 1980