Contents

CHAPTER VII

Timelag and the Multiplicity Factor in Abdominal Injuries

Luther H. Wolff, M. D., W. Philip Giddings, M. D.,
Samuel B. Childs, M. D., and Clarence R. Brott, M. D.

At the beginning of World War II, as in previous wars, it was a universally accepted concept that the length of the timelag (the interval from wounding until the institution of therapy) had an important influence on the case fatality rate in abdominal wounds. On the surface, this is a perfectly reasonable point of view. Hemorrhage, peritoneal contamination, and disturbances of cardiorespiratory and gastrointestinal physiology combine to produce a state of shock following wounding. The longer these conditions are permitted to continue uncorrected, the more severe does the shock become, the more serious is the deterioration of the wounded man's status, and, presumably, the graver is the prognosis.

It was with full acceptance of this concept that the analysis was undertaken of the 2,926 abdominal injuries in this series in which data concerning the timelag were available. The average interval from wounding to operation was found to be almost 10.5 hours, the two components being, respectively, 6.5 hours for the period from injury to hospitalization and 3.9 hours for the period from hospitalization to operation. The chief obstacle to earlier hospitalization lay in the obvious difficulties in evacuating casualties from the battlefield. The delay in the hospital was more apparent than real; it was explained by the time consumed in necessary preoperative resuscitation, particularly of poor-risk patients. A further explanation, in times of stress, was the overburdening of available surgical facilities, which resulted in an inevitable prolongation of the timelag.

All through the war, every possible effort was directed toward shortening the timelag, in line with the belief that the earlier operation could be performed, the better would be the results, and vice versa. As the result of these efforts, and as the experience of military personnel increased and evacuation facilities were improved, a substantial reduction in the average timelag was achieved. In 1944, it was 11.4 hours (6.9 hours between wounding and hospitalization and 4.5 hours between hospitalization and operation). In 1945, it was reduced to 9.5 hours (6.1 hours between wounding and hospitalization and 3.4 hours between hospitalization and operation).

In view of these facts, it was therefore disconcerting, when this analysis was conducted after the war, to find that the figures furnished little support for the concept that the length of the timelag had an important influence on the case fatality rates. When they were calculated in 2-hour periods (fig. 20), no 

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FIGURE 20.-Influence of timelag (wounding to operation) in 2,863 recorded abdominal injuries. Sixty-three cases in which the timelag was greater than 36 hours are not included, because the number would have been too small in each category over 36 hours to be of significance.

consistent change in them was observed with the passage of time. Obviously it was necessary to seek an explanation for the paradox that an increase in the timelag did not greatly increase the case fatality rate, while a shortening of the interval did not greatly improve it.

When the abdominal wounds in the series were evaluated in terms of their severity, the apparent paradox was promptly resolved. An analysis from this point of view showed that wounds of the same viscus differed from casualty to casualty in respect to their extent, the degree of associated hemorrhage, the amount of peritoneal contamination, and the specific effect of the wound upon

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the individual. On the other hand, in spite of their evident importance, these considerations could not be reduced to statistical form. From these standpoints, each case was an entity in an exclusive category.

As a practical solution of the problem, therefore, these abdominal injuries were classified from the standpoint of severity in terms of the number of visceral injuries each individual casualty had sustained. When this had been done, it immediately became clear that whether or not patients who had sustained the greatest number of visceral injuries (and who, presumably, were the most severely wounded) were to live or die did indeed depend in large measure upon the time elapsed between wounding and the institution of surgical care. The most severely wounded patients, in terms of multiplicity of injuries, survived only if they were operated on promptly, and the case fatality rate increased progressively from category to category as the timelag increased (table 9). It was 100 percent in the categories in which the largest number of wounds was associated with the longest timelag. There were no survivals among the 6 casualties who suffered 6 visceral injuries each, although 5 of the 6 were operated on within 16 hours of wounding, and there were only 2 survivals among the 22 patients with 5 visceral injuries each, although 20 of the 22 were also operated on within 16 hours of wounding. It is true that in some of the categories the numbers of cases were so small as to be without statistical significance, but in general the figures corroborated the clinical impression that the least severely wounded man could tolerate a certain prolongation of the timelag, while the most severely wounded men could not. Some wounds were potentially lethal, regardless of the brevity of the timelag, while others were not necessarily lethal originally but tended to become so as the timelag increased.

The truth of the assumption that the case fatality rate increases as the timelag lengthens was generally acceptable for the individual patient, though at the extremes of time there were balancing factors which effectively precluded its demonstration. Many of the fatalities in the first hours after injury occurred in mortally wounded men, who were given priority of treatment in what proved a vain attempt to save their lives. These deaths elevated the case fatality rates for the early hours. At the other extreme of time, patients who survived after 18 to 24 hours without operation might well have lived without treatment; no one would contend that all abdominal wounds are fatal without surgery.

Examination of the multiplicity indexes (table 9) confirms these generalizations. They are, respectively, 1.64, 1.59, 1.45, 1.41, and 1.13. By these criteria, the most severely wounded patients obviously were operated on in the first 8-hour interval, and the least severely wounded were operated on after 24 hours. The figures thus afford statistical confirmation of a recognized clinical observation; namely, the case fatality rate in casualties operated on early was elevated by the inclusion in this category of a relatively large number of the most critically wounded casualties, while the rate among those coming to surgery late was kept below expected levels by the inclusion of a similar proportion of the less seriously wounded.

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TABLE 9.- Influence of combined timelag and multiplicity factor on case fatality rates in 2,926 abdominal injuries

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MULTIPLICITY FACTOR

Since the importance of the multiplicity of visceral injuries was an entirely new concept in military surgery, a new nomenclature had to be devised for it. The terms "multiplicity factor" and "multiplicity index" were accordingly introduced. Multiplicity factor was employed to designate the number of abdominal organs injured in any given patient, as determined at operation or autopsy. Multiplicity index was employed to indicate the aggregate severity of the individual cases in a given series of abdominal wounds. It was obtained by dividing the total number of organs injured in the series by the number of cases which made up the series.

In the interests of clarity, certain explanations are necessary in regard to this nomenclature. Multiplicity factor does not imply selectivity of viscera. Combinations are limited entirely to numerical incidence. Only the number of organs injured matters. Nor does the term carry any implications concerning the total number of wounds sustained in a given case, since multiple wounds of the same viscus are counted as a single wound. Thus, wounds of the cecum, transverse colon, and sigmoid colon in the same patient would be counted as a single wound of the large bowel, and wounds of the jejunum and ileum would be counted as a single wound of the small bowel.

In this analysis, wounds of the major abdominal blood vessels (as distinguished from wounds of the visceral blood supply) are not regarded as visceral injuries. It is evident, however, that the multiplicity factor is just as valid in them as it is in other abdominal injuries (p. 323), the only difference being that the case fatality rates for vascular injuries begin at a much higher level.

It should be emphasized again that the concept of the multiplicity factor was a postwar development. It was evolved only when it became evident that the timelag, upon which the major emphasis had been placed in the past, apparently did not play the role in the case fatality rate in abdominal injuries which it was formerly supposed to play. When the multiplicity factor was adopted as a yardstick in the analysis, much that had been contradictory and confusing when the timelag alone was used as a point of reference was immediately clarified. It now became clear that, when only the timelag was analyzed, dissimilar cases were being compared with each other and that the analysis of this type of trauma would be valid only when the cases were separated into comparable and exclusive categories.

When the injuries in which sufficient data for this purpose were available were categorized according to the multiplicity factor (tables 9 and 10, figs. 21 and 22), the timelag fell into the proper perspective, the case fatality rate was found to ascend in almost arithmetical progression with each additional viscus injured, and the increase was almost as constant for each special organ as it was for the entire series.

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FIGURE 21.-Influence of multiplicity factor on case fatality rates in 3,129 recorded abdominal injuries.

FIGURE 22.-Influence of multiplicity factor on case fatality rates in various combinations of abdominal wounds.

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TABLE 10.-Influence of multiplicity factor on case fatality rates in wounds of various viscera

¹There are omitted from this category 15 cases in which wounds of the stomach and one or more other viscera were complicated by wounds of the great vessels.

The multiplicity factor also proved a valuable aid in the appraisal of abdominal injuries from a number of other points of view:

1. Associated injuries.-An analysis of the 1,089 cases in which abdominal wounds were associated with extra-abdominal wounds (p. 114) revealed that moderately severe extra-abdominal injuries were often associated with abdominal wounds of high multiplicity and that the reverse was also true, severe extra-abdominal injuries usually being associated with abdominal injuries of low multiplicity. The statistics suggested that when severe extra-abdominal injuries were associated with abdominal injuries of high multiplicity, the wounded men seldom survived to reach the hospital.

2. Shock.-Virtually every one of the deaths which occurred in this series within the first 24 hours after operation was attributable to shock, which developed as the result of hemorrhage, peritoneal contamination, or tissue destruction. As might have been expected, a definite association was found to exist between the multiplicity factor and these deaths. In the 756 fatalities in the whole series, 35 percent of the deaths in univisceral wounds occurred within 24

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hours of operation, as did 36 percent of the deaths in which 2 organs were injured, 40 percent of the deaths in which 3 organs were injured, and 51 percent of the deaths in which 4 or more organs were injured.

3. Pulmonary complications.-The incidence of postoperative pulmonary complications (p. 204) rose from 6.5 percent in univisceral injuries to 13.0 percent when 5 or more viscera were injured. This observation is of clinical rather than statistical significance. The more severely wounded patients were more apt to develop stagnation of the tracheobronchial secretions and therefore presented a higher incidence of atelectasis and bronchopneumonia.

4. Variations in case fatality rates.-One of the perplexing features of this analysis before the concept of the multiplicity factor was evolved was the differences between the case fatality rates of surgeons of equal ability and experience. Another was the differences between the rates of more forward (field) hospitals and evacuation hospitals. These differences had been realized in the course of the war. They could not reasonably be explained on the basis of superior or inferior surgical performance, or merely as matters of chance. It was the general impression that less severely wounded patients were treated at evacuation hospitals, but proof of the impression was lacking until this series was analyzed on the basis of the multiplicity factor. When the severity of the wounds was taken into consideration, differences in the case fatality rates of hospitals in different echelons (table 5, p. 89) could easily be explained. A high rate was to be expected in field hospitals, because the most severely wounded patients were treated in them.

A single comparison will make this point clear. The case fatality rate for 232 casualties treated by surgeons of the 2d Auxiliary Surgical Group in evacuation hospitals was 15.1 percent, while the rate for surgeons of the same group for 2,851 casualties treated in field hospitals was 24.3 percent. Differences in the multiplicity indexes explain the differences in the case fatality rates. The index for the casualties treated in evacuation hospitals was 1.10, while for casualties treated in field hospitals it was 1.70. Likewise, differences in the multiplicity indexes explain differences in the case fatality rates of surgical teams of similar ability and experience.

Application of the multiplicity index to certain recorded series of abdominal injuries permitted comparison of them by a uniform standard of evaluation (table 11). An examination of the Welch and Tuhy¹ series, the Ogilvie (Western Desert)² series, and the material of the 2d Auxiliary Surgical Group

¹Welch, C. S.; and Tuhy, J. E.: Combined Injuries of the Thorax and Abdomen. Ann. Surg. 122: 358-374, September 1945.
²Ogilvie, W. H.: Abdominal Wounds in the Western Desert. Surg., Gynec. & Obst. 78: 225-238, March 1944.

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shows the correlation which might be expected between the Welch and Tuhy figures and those of the 2d Auxiliary Surgical Group. In the British material, on the other hand, although the multiplicity index was lower than in either of the other series, the case fatality rate was higher. The discrepancy can probably be explained by two factors: (1) That conditions of evacuation and hospitalization were frequently extremely unfavorable in the fighting in the Western Desert, and (2) that penicillin was not available when these cases were treated as it was for the patients in the other (later) series.

TABLE 11.-Influence of multiplicity factor on case fatality rates in various recorded series of abdominal injuries

¹Western Desert (second series, 244 cases; 3 deaths on the operating table are excluded from the figures).
²In this category are included all injuries of 3 or more organs.

LIMITATIONS OF THE MULTIPLICITY FACTOR

In this series of abdominal injuries, the application of the multiplicity factor clarified much that had originally been confusing and actually inexplicable. On the other hand, while it proved to be of a valuable statistical type for series analysis, it was found to have certain weaknesses and limitations, because of relative dispersion, when it was applied to individual cases. Another reason was that it was entirely possible for a wound of a single viscus to be so grave that the intra-abdominal damage was as serious as it was in another case in which three or even more organs were wounded. Thus the multiplicity factor was found to be not completely reliable in wounds of the stomach (table 10, fig. 22). In injuries of this organ, the case fatality rate for univisceral wounds was slightly higher than for gastric wounds complicated by a wound of one other viscus. The explanation is the inherent gravity of all wounds of

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the stomach, which were likely to be associated with acute precipitous chemical peritonitis (p. 231). For this reason, the case fatality rate in univisceral gastric wounds was unusually high as compared with the rates for univisceral wounds of other organs.

On the surface, it might seem that the multiplicity factor should be useful in prognosis, making it possible to predict the outcome for the individual casualty with a reasonable degree of accuracy. In general (fig. 21), the case fatality rate increased about 15 percent as each additional viscus was injured, and, generally speaking, the number of viscera injured was more significant than the particular organ involved. These generalizations, however, do not hold for the individual case, in which the multiplicity factor must be used with great caution. For one thing, in a case in which only one or two viscera are injured, an unusually prolonged timelag might make the prognosis more serious than the multiplicity factor alone would indicate. For another, the presence of serious associated extra-abdominal injuries, the development of anaerobic and other infections, unforeseen complications such as intestinal obstruction and wound dehiscence, and other considerations of the same sort might completely vitiate the multiplicity factor in the individual case.

Notwithstanding the variations and limitations of the multiplicity factor in its application to individual cases, when it was applied to this particular series-in which many variables existed-it supplied an accurate and useful yardstick for many different purposes and resolved at once the apparent paradox which had existed when the case fatality rates were calculated only in reference to the timelag.

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