Nonoperative Management in Blunt Splenic Trauma: Can Shock Index Predict Failure?

Nonoperative Management in Blunt Splenic Trauma: Can Shock Index Predict Failure?ww.sciencedirect.com
j o u r n a l o f s u r g i c a l r e s e a r c h a u gu s t 2 0 2 2 ( 2 7 6 ) 3 4 0e3 4 6
Available online at w
Nonoperative Management in Blunt Splenic Trauma: Can Shock Index Predict Failure?
Lara Senekjian, MD, MS,a,* Bryce R.H. Robinson, MD, MS,b
Ashley D. Meagher, MD, MPH,c Joel A. Gross, MD,d
Ronald V. Maier, MD,b Eileen M. Bulger, MD,b Saman Arbabi, MD,b
and Joseph Cuschieri, MDe
aDivision of Trauma and Critical Care, Department of Surgery, University of California San Francisco-East Bay,
Oakland, California bDivision of Trauma and Critical Care, Department of Surgery, University of Washington, Seattle, Washington cDivision of Trauma and Critical Care, Department of Surgery, University of Indiana, Indianapolis, Indiana dDepartment of Radiology, University of Washington, Seattle, Washington eDivision of Trauma and Critical Care, Department of Surgery, University of California San Francisco, San
Francisco, California
a r t i c l e i n f o
Article history:
Keywords:
0022-4804/$ e see front matter ª 2022 The (http://creativecommons.org/licenses/by/4.0 https://doi.org/10.1016/j.jss.2022.02.035
a b s t r a c t
Introduction: Predicting failure of nonoperative management (NOM) in splenic trauma re-
mains elusive. Shock index (SI) is an indicator of physiologic burden in an injury but is not
used as a prediction tool. The purpose of this study was to determine if elevated SI would
be predictive of failure of NOM in patients with a blunt splenic injury.
Methods: Adult patients admitted to a level-1 trauma center from January 2011 to April 2017
for NOM of splenic injury were reviewed. Patients were excluded if they underwent a
procedure (angiography or surgery) prior to admission. The primary outcome was requiring
intervention after an initial trial of noninterventional management (NIM). An SI > 0.9 at
admission was considered a high risk. Univariate and multivariate analyses were used to
identify predicators of the failure of NOM. Findings were subsequently verified on a vali-
dation cohort of patients.
Results: Five hundred and eighty-five patients met inclusion criteria; 7.4% failed NIM. On an
univariate analysis, findings of pseudoaneurysm or extra-arterial contrast on computed
tomography did not differentiate successful NIM versus failure (8.1% versus 14.0%,
P ¼ 0.18). Age, the American Association for the Surgery of Trauma injury grade, and
elevated SI were included in multivariate modeling. Grade of injury (OR 3.49, P ¼ 0.001), age
(OR 1.02, P ¼ 0.009), and high SI (OR 3.49, P ¼ 0.001) were each independently significant for
NIM failure. The risk-adjusted odds of failure were significantly higher in patients with a
high risk SI (OR 2.35, P < 0.001). Validation of these findings was confirmed for high SI on a
subsequent 406 patients with a c-statistic of 0.71 (95% CI 0.62-0.80).
Conclusions: Elevated SI is an independent risk factor for failure of NIM in those with splenic
injury. SI along with age and computed tomography findings may aid in predicting the
UCSF East Bay, 1411 E 31st Street, Oakland, CA, 94602. thsystem.org (L. Senekjian). Authors. Published by Elsevier Inc. This is an open access article under the CC BY license /).
failure of NIM. Trauma providers should incorporate SI into decision-making tools for
splenic injury management.
ª 2022 The Authors. Published by Elsevier Inc. This is an open access article under the CC
BY license (http://creativecommons.org/licenses/by/4.0/).
of patients with blunt splenic trauma who are hemody-
namically normal.1,2 Close observation of these patients is
the standard of care as it limits the number of emergent
splenectomies, prevents the risk of postsplenectomy sepsis,
decreases the number of trauma laparotomies, and pre-
vents surgical complications.3 However, NOM is not
without risks. A small cohort of patients will fail NOM and
need splenectomy, putting them at risk for hypotension and
possibly worse overall outcomes.4,5
In the early 1990s, prophylactic splenic angioembolization
(SAE) was proposed as an addition to the treatment in patients
undergoing NOM. In patients who are hemodynamically
normal, adding SAE was thought to prevent the need for sple-
nectomy; however, over the past 30 y, results have been
mixed.6-10Advocatesassert theadditionofSAE thatwill prevent
splenectomies; thus, the patient would maintain splenic func-
tion and therewould be fewer laparotomies performed.11-18 The
addition of SAE is notwithout risks but not limited to access site
complications and infections.6,8,12,14,15,19 Furthermore, the
recentwork has demonstrated that the addition of prophylactic
SAE is not cost-effective.20,21
and therefore benefit from early intervention. Multiple
variables have been investigated to predict failure
including age, injury severity score (ISS), American Asso-
ciation for the Surgery of Trauma (AAST) grade of splenic
injury, specific computed tomography (CT) findings, and
trauma centerelevel designation.22-26 However, none of
these have taken into consideration the overall physiologic
effects of the splenic injury. To determine the physiologic
impact, shock index (SI) has been proposed as a possible
variable.27-29 SI, which is calculated by dividing the heart
rate by the systolic blood pressure, was initially introduced
in 1967 by Doctor Allgower as a predictor of impending
hemorrhagic shock.30 Normal SI is between 0.5 and 0.7 in
healthy adults. In the setting of trauma, SI might have a
role for recognition of hemorrhage when the patient is still
in the compensatory phase of shock. Prehospital SI of >0.9
is predictive of overall mortality and the requirement of
massive transfusion in patients with major traumatic in-
juries.27,28 An advantage of SI is the ease of measurement,
as it does not require a specialized equipment and is
noninvasive.
It is accepted that some patients will fail NOM and ulti-
mately need splenectomy. There is still limited information
about which patients will specifically fail. We hypothesize
that presenting an SI >0.9 is predictive of failure of NOM in
patients with a blunt splenic injury.
The study was approved by the Internal Review Board of
Harborview Medical Center to waive the participants’
informed consents. For analysis and development of the
prognostic model, patients were included who were admitted
to our level-1 trauma center from January 2011 to April 2017
with blunt splenic injury. We excluded those patients
admitted with penetrating mechanism, patients who were
less than 18 y old, patients who did not sustain an injury,
patients who had any surgical or interventional radiology
procedure completed prior to presentation at the admitting
hospital, or those patients who died in the emergency
department (ED). Patients meeting inclusion criteria were
then reviewed for an initial plan ofmanagement of the splenic
injury. Patients who were taken from the ED to the operating
room for immediate splenectomy or to interventional radi-
ology (IR) for angioembolization were excluded. Our study
population included only those patients who did not undergo
procedure and thus had attempted noninterventional man-
agement (NIM).
anything greater than 0.9 was considered high. All CT scan
reports were evaluated to determine the AAST grade of injury.
Patients were divided into a low-grade (I and II) and high-
grade (IIIeV) injury. Initial reports missing this information
were reviewed by a board-certified radiologist (J.G.) blinded to
the details of the patient and nature of the presentation. Of
note, as these patients were admitted between 2011 and 2017,
the previous AAST injury grading scale was used which does
not include vascular injury.31 Positive findings on CT scan
were defined as having either extra-arterial contrast or pseu-
doaneurysm. If patients underwent a splenectomy or
angioembolization during NIM, they were considered to have
failed NIM.
cessfully managed without intervention to patients who
required intervention (failed NIM). Variables included age,
gender, grade of injuries, admission vital signs SI, and CT
findings (Table 1). A ShapiroeWilk test was used to evaluate
for normal distribution of continuous variables, which were
then reported as median and interquartile range (IQR). All
dichotomous variables were analyzed with a Chi-square or
Fischer’s exact test as appropriate. Continuous variables were
analyzed with t-tests and discrete variables were analyzed
with the Mann-Whitney U-test. Any variable that was signif-
icant (P 0.1) was included in the multivariate analysis.
Variables included in our multivariate model were findings of
elevated SI, patient age, and presence of high-grade splenic
Total Successful NOM Failure of NOM P Value
Patients 585 542 41
Mean Age (IQR) 38 (31) 37 (30) 47 (29) 0.04
Male (%) 383 (65.4%) 353 (65.1%) 30 (69.8%) 0.54
High Grade Spleen Injury 196 (33.5%) 171 (31.5%) 25 (58.1%) < 0.001
Injury Severity Score 22 (17) 22 (17) 27 (21) 0.13
Systolic Blood Pressure 104 (25) 105 (24) 94 (23) 0.01
Heart Rate 98 (29) 97 (29) 104 (36) 0.29
Shock Index >0.9 340 (58.1%) 307 (56.6%) 33 (76.7%) 0.01
Base Deficit 4.2 (4.4) 4.2 (4.4) 3.9 (5.7) 0.07
Lactate 2.2 (2.5) 2.2 (2.5) 1.9 (1.9) 0.31
Extravasation or Pseudoaneurysm on CT 50 (8.5%) 44 (8.1%) 6 (14.0%) 0.18
342 j o u r n a l o f s u r g i c a l r e s e a r c h a u gu s t 2 0 2 2 ( 2 7 6 ) 3 4 0e3 4 6
injury. Systolic blood pressure was not included due to
collinearity with SI. We assessed the predictive accuracy of
the model with both calibration and discrimination.
January 2011 – April 2017 1164 patients
Attempt to manage non operatively
N = 585
813 patients
Fig. 1 e Consort diagram with exclusion criteria and study popu
interventional radiology.
Calibration was evaluated graphically by comparing the pre-
dicted failure of NIM to the actual failure of NIM. Discrimi-
nation was assessed using c-statistic/the area under the
ED to OR for splenectomy N = 179
Penetrating mechanism Death in ED
Less than 18 years old Procedure prior to presentation
Exclude = 351
N = 49
Total Successful NOM Failure of NOM P Value
Patients 585 542 43
ICU LOS in Days, Median (IQR) 2 (4) 2 (4) 5 (8) 0.002
Required Ventilaton, n (%) 259 (44.3%) 234 (43.2 %) 25 (58.1%) 0.05
Ventilator Free D* 28 (3) 28 (3) 26 (7) 0.06
Hospital LOS in Days 7 (12) 7 (11) 14 (18) 0.002
Death 32 (5.5%) 30 (5.6 %) 2 (4.7%) 1.00
ICU, intensive care unit; LOS, length of stay; NOM, nonoperative management; IQR, interquartile range. * ventilator free days in 28.
s e n e k j i a n e t a l s h o c k i n d e x a nd s p l e e n i n j u r y 343
receiver operator curve. A second population of patients
admitted from May 2017 to October 2020 was then evaluated
to validate the model by comparing the predicted failure of
NIM to the actual failure of NIM. The performance was then
assessed using calibration and discrimination analyses. Ana-
lyses were performed using STATA 13 (StataCorp, College
Station, TX).
During the study period, 1164 patients were identified; of
those, 351 were excluded due to age, mechanism, surgery
prior to transfer, or death in the ED. Of the remaining 813
patients, 179 (22.0%) underwent immediate splenectomy and
49 (6.0%) underwent immediate angioembolization. The
remaining 585 patients were evaluated for success versus
failure of NIM (Fig. 1).
Overall, 542 patients were managed with successful NIM
and 43 failed requiring intervention of the spleen (failure
rate of 7.9%). The populations had a median age of 38 y (IQR
31), 65.4% were male, and the median injury severity score
(ISS) was 22 (IQR 17) (Table 1). Evaluated laboratories of
lactate and base deficit were similar between the two
groups, 2.2 (IQR 2.5) and 4.2 (IQR 4.4), respectively. Positive
CT findings (contrast blush or pseudoaneurysm) were
similar in patients who were successfully managed without
intervention compared to those who ultimately failed (8.1%
versus 14.0%, P ¼ 0.18).
Of the patients undergoing attempted NIM, 108 (18.5%)
patients were aged 60 y or greater. In this subpopulation 61
(56.5 %), patients had an SI of 0.9 or greater which is no
different when compared to 279 patients less than 60 y old
(58.5 %) (P ¼ 0.7). Outcomes in patients who failed NIM
Table 3 e Odds of failure of nonoperative management. High grade injury includes injury grade III-V.
OR P value CI
Age 1.02 0.009 1.01-1.04
Shock Index >0.9 3.13 0.003 1.48-6.60
compared to those who were successful were similar except
for the overall need for ventilation (Table 2). Twenty-five
(58.1%) patients who failed NIM had at least one ventilator
day compared to those who were successful; 234 (43.2%) pa-
tients required ventilation for at least 1 d (P ¼ 0.05).
In a multivariate analysis, patient age, grade of injury, and
presence of SI greater than 0.9 were determined to be signifi-
cant factors to predict failure (Table 3). A high grade of injury
was most predictive of failure (odds ratio [OR] 3.88; 95% con-
fidence interval [CI] 2.00-7.51; P < 0.001). For any patient with
an SI greater than 0.9, the odds of failure increased (OR 3.13 [CI
1.48-6.60], P ¼ 0.003). The derivation model showed good
discrimination with a c-statistic of 0.73 (95% CI 0.65-0.81).
Model calibration is illustrated by graphing observed versus
predicted outcomes. The slope of line of best (R2 ¼ 0.85)
compared the ideal relationship of observed and expected
outcome (Fig. 2).
Discrimination of the validation model was similar to the
derivationmodel with a c-statistic of 0.71 (95% CI 0.62-0.80). As
expected, calibration was poorer in the validation model
(R2 ¼ 0.59) (Fig. 3).
Discussion
SI is an easily obtainable data point to suggest possible
imminent cardiovascular collapse but has not been evaluated
as a possible predictor of outcomes in blunt splenic injury.We
found that presence of an initial SI greater than 0.9 is a pre-
dictor of failure of NIM in patients with blunt splenic injury.
An elevated SI along with increasing patient age and high
AAST injury grade on CT scan findings together can help
predict which patients may fail NIM.
Previously, SI has been used in the prehospital setting and
the ED, but has a limited role in trauma. SI has never been
suggested for the prediction of failure of NIM in blunt splenic
injury. This study takes the relatively simple data point of SI
and shows that it may help predict which patients will fail.
The advantage of SI is the ease of use and familiarity by
trauma providers. The heart rate and systolic blood pressure
alone were not predictive of failure in our population.
O BS
ER VE
D FR
EQ U
EN CY
PREDICTED PROBABILITY
Fig. 2 e Calibration of model using observed frequency of failure of NOM to expected probability of failure. Blue diamonds
show outcomes in tenths of patients with similar predicted probabilities. Orange line demonstrates ideal relationship
between observed frequency and predicted probability of outcome in model with perfect calibration (Color version of figure
is available online).
344 j o u r n a l o f s u r g i c a l r e s e a r c h a u gu s t 2 0 2 2 ( 2 7 6 ) 3 4 0e3 4 6
However, SI was enforcing the appeal of SI as a marker of
severe injury during the early phase of compensatory shock.
This is a retrospective single institution analysis which
provides strengths and limitations. The use of a single center
afforded the ability to review all CT scans; thus, results were
verified by board-certified radiologists with significant expe-
rience in reviewing blunt splenic trauma. However, CT scans
may underdiagnose injury severity in trauma assessment and
more commonly in severe injuries or those with neuro
trauma.5 In 2018, the addition of vascular injury to the AAST
grading systemwasmeant to improve the diagnostic ability of
the scan.32 However, CT scan results are somewhat incon-
sistent and the phase of contrast has major implications. The
terminology of reported CT findings is confusing because
“contrast blush,” “active extravasation,” and “pseudoaneur-
ysm” are quoted as different entities but are nearly impossible
to differentiate on CT scans.33
The attending surgeon had a final say in clinical decisions
for patient care. Forty-nine patients were taken for immediate
angioembolization. Interestingly, nearly 60% of these patients
presented with a SI of greater than 0.9. The surgeon made the
decision for SAE based on the patient factors and admitting
physiology in real time. This group of patients did not have
NIM. This may have biased our results as these patients were
not given the opportunity to successfully complete NIM. Our
patient population for those who had attempted NIM was
selected by the attending surgeon of record. The reasons for
failure of NIM were not always clear and may have demon-
strated some bias which cannot be ascertained from the
patient records. These data did not include readmission re-
cords, so any patient who either failed or had a complication
after initial hospitalizationwas not captured in this study. The
heart rate and systolic blood pressure were extracted by our
in-house trauma registrars, but accuracy of these data cannot
be verified.
Some previous studies have suggested that SI may not be
as reliable in the elderly and very young patients.29,34
Although only our population did not demonstrate any sig-
nificant difference in the failure of NIM or SI in the elderly,
only 18.5% of the population were 60 y old or greater. Given
our findings, we feel that SI is a useful measurement and
should be incorporated into a clinician’s decision making.
Conclusion
SI is a relatively simple measurement that is obtained at the
beginning of trauma evaluation. By evaluating the SI with
CT scan findings and patient age providers can understand
the risk of failure of NIM in blunt splenic injury. Although SI
can assist with determining if a patient will fail NIM, the
addition of age and AAST grade can further elucidate which
patients may fail, and clinicians should use this information
early in the patient’s hospital course to assist in decision
making.
O BS
ER VE
D FR
EQ U
EN CY
PREDICTED PROBABILITY
Fig. 3 e Calibration of model in validation population using observed frequency of failure of NOM to expected probability of
failure. Blue diamonds show outcomes in tenths of patients with similar predicted probabilities. Orange line demonstrates
ideal relationship between observed frequency and predicted probability of outcome inmodel with perfect calibration (Color
version of figure is available online).
s e n e k j i a n e t a l s h o c k i n d e x a nd s p l e e n i n j u r y 345
Study Type
L.S. reviewed the literature; L.S., J.C., J.G., B.R., and A.M.
analyzed and interpreted data; L.S., J.C., and B.R. prepared the
article; All authors participated in the study design and critical
review of the article.
r e f e r e n c e s
1. Stassen NA, Bhullar I, Cheng JD, et al. Selective nonoperative management of blunt splenic injury: an Eastern Association for the Surgery of Trauma practice management guideline. J Trauma Acute Care Surg. 2012;73(5 Suppl 4):S294eS300.
2. Coccolini F, Montori G, Catena F, et al. Splenic trauma: WSES classification and guidelines for adult and pediatric patients. World J Emerg Surg. 2017;12:40.
3. Luu S, Spelman D, Woolley IJ. Post-splenectomy sepsis: preventative strategies, challenges, and solutions. Infect Drug Resist. 2019;12:2839e2851.
4. Teuben MPJ, Spijkerman R, Blokhuis TJ, et al. Safety of selective nonoperative management for blunt splenic trauma: the impact of concomitant injuries. Patient Saf Surg. 2018;12:32.
5. Buduhan G, McRitchie DI. Missed injuries in patients with multiple trauma. J Trauma. 2000;49:600e605.
6. Wahl WL, Ahrns KS, Chen S, Hemmila MR, Rowe SA, Arbabi S. Blunt splenic injury: operation versus angiographic embolization. Surgery. 2004;136:891e899.
7. Velmahos GC,…