BACKGROUND: Arterial shunting is a well-described method to control hemorrhage and rapidly reestablish flow, but optimal shunt dwell times remain controversial. We hypothesized that prolonged shunt dwell times of more than 6 hours are related to adverse outcomes after major arterial injury.
METHODS: A review (2005–2013) of all patients with arterial shunts placed after traumatic injury at our urban Level I trauma center was undertaken. Patients who died prior to shunt removal (n = 7) were excluded. Shunt complications were defined as dislodgement, thrombosis, and distal ischemia. Patients were compared on the basis of shunt complications with respect to clinical parameters.
RESULTS: The 42 patients who underwent arterial shunting after major vascular injury were primarily young (median, 26 years; interquartile range [IQR], 22–31 years) males (97.6%), severely injured (Injury Severity Score, 17.5 [IQR, 14–29]; shunted vessel Abbreviated Injury Scale score, 4 [IQR, 3–4]) by gunshot (85.7%) requiring neck/torso (33.3%) or upper-extremity (19.1%) or lower-extremity (47.6%) shunts. Thirty-five patients survived until shunt removal, and 5 (14.3%) of 35 developed shunt complications. Demographics and clinical characteristics were compared between those with shunt dwell times of less than 6 hours (n = 19) and more than 6 hours (n = 16). While patients appeared to have a greater injury burden overall in the group with dwell times of more than 6 hours, there were no statistical differences between groups with respect to age, gender, initial systolic blood pressure or hemodynamics during the shunt dwell period, use of vasopressors, Abbreviated Injury Scale score of the shunted vessel, Injury Severity Score, or outcomes including limb amputation or mortality. No patients (0/19) with shunt dwell times of less than 6 hours developed complications, whereas 5 (31.3%) of 16 patients with dwell times of more than 6 hours developed shunt complications (p = 0.05).
CONCLUSIONS: In this civilian series, 14% of patients with arterial shunts developed shunt complications. Our data suggest that limiting shunt dwell times to less than 6 hours when clinically feasible may decrease adverse outcomes.
LEVEL OF EVIDENCE: Therapeutic/care management study, level IV.
From the Division of Traumatology, Surgical Critical Care and Emergency Surgery, Department of Surgery, Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA.
Submitted: May 20, 2016, Revised: October 7, 2016, Accepted: October 14, 2016, Published online: December 28, 2016.
This work was presented as a podium presentation at the 17th European Congress of Trauma & Emergency Surgery, April 26, 2016, in Vienna, Austria.
Address for reprints: Mark J. Seamon, MD, Division of Traumatology, Surgical Critical Care and Emergency Surgery, Department of Surgery, Hospital of the University of Pennsylvania, 51 N 39th St, Medical Office Bldg, 1st Floor Suite 120, Philadelphia, PA 19104; email: firstname.lastname@example.org.
The tenets of damage control surgery are well described and call for an abbreviated initial procedure focused entirely on the rapid hemorrhage and contamination control. In those at risk of coagulopathy, acidosis, and hypothermia, formal injury repair and closure are then undertaken only after a period of resuscitation.1 Temporary vascular shunting mimics these same damage control management principles. Vascular shunt placement quickly controls hemorrhage from exsanguinating vascular injuries and restores distal perfusion to limit the ischemic insult but is less technically demanding and more rapid than definitive vessel repair.2–7
The first detailed description of temporary vascular shunting was reported by Eger et al.4 in 1971. During the Israeli military conflict, 36 patients had a shunt with polyethylene tubing fashioned with a heparin-infusing three-way adapter. Despite a mean ischemic time of 10 hours, only 8% required amputations, which the authors hypothesized was due to the early and routine use of temporary arterial shunts in this population. Shunt technology has changed little over the past 45 years, although systemic anticoagulation is not routinely utilized today. Early civilian reports describing the role of temporary vascular shunts consisted primarily of case reports and small case series8–11 until the military conflicts in Iraq and Afghanistan. Following this military experience,3,5,12,13 larger civilian series2,6,7,14–17 with more refined analyses ensued. Many of these series describe extended shunt dwell times of several days without adverse consequences. To our knowledge, the longest reported shunt dwell time to date is 10 days—without either systemic anticoagulation or complication.18
Still, stating that one “can” leave a shunt in place for an extended dwell time differs from stating that one “should” leave a shunt in place for an extended dwell time. To this end, we sought to determine if shunt dwell time was associated with shunt complications. We hypothesized that prolonged shunt dwell times of more than 6 hours are related to adverse outcomes after major arterial injury.
After institutional review board approval was obtained from the University of Pennsylvania (Philadelphia, Pennsylvania), a review of all patients at our urban Level I trauma center during the study period from January 2005 through December 2013 was undertaken. All adult patients who underwent arterial shunting (n = 42) after traumatic injury were included in the study analysis. Patients were excluded from study analysis if younger than 15 years or if shunted injuries were located distal to the brachial or popliteal arteries. Data analyzed included demographics, injury mechanism and location, presenting physiology, severity of vascular injury, associated injuries, need for amputation, and mortality. A portion of the data set in the current analysis and study was utilized in a prior published report.15
The primary study end point was the development of shunt complications defined as documented shunt dislodgement, thrombosis, or distal ischemia during the shunt dwell period. For study purposes, ischemia was defined as distal tissue injury caused by prolonged poor perfusion and was diagnosed by clinical examination (such as loss of pulses, sensation, or motor function in extremity). There were no documented technical errors in shunt placement, evidence of downstream injury, or mangled extremities in these patients.
The shunt dwell period was defined as the elapsed time period beginning with shunt insertion and ending with shunt removal during definitive arterial repair. To limit selection bias and effectively analyze shunt complications, the seven patients who died prior to shunt removal were excluded from the remainder of the analysis. Initial major vascular injuries (aorta and iliac) were the likely attributable cause of mortality in five of these seven excluded cases (death, shunt dwell times <6 hours). Two other excluded cases (death, shunt dwell times 6–48 hours) were likely attributable to concomitant injuries (cranial gunshot wound [GSW] and massive sacral plexus venous bleeding). No death was directly attributable to either shunt placement itself or a resulting shunt complication prior to removal. Patients who survived the shunt dwell period (n = 35) were then compared on the basis of shunt dwell time and shunt complications with respect to measured clinical parameters. Six hours was chosen a priori as the primary comparison cutoff point because of its clinical utility as a threshold for warm ischemic time after vascular injury.
Data were abstracted from the medical record utilizing a standardized data collection tool. Continuous data were expressed as medians with interquartile ranges and categorical or ordinal data were expressed as proportions (%). The Wilcoxon-Mann-Whitney U-test was used to compare distributions of continuous variables, and either Pearson χ2 or Fisher exact test was used to compare proportions of categorical variables. Statistical analysis was performed using SPSS version 23 (IBM Inc, Chicago, Illinois). All statistical tests were 2-tailed, and statistical significance was considered when p ≤ 0.05.
Forty-two patients had arterial shunts placed during the study period (Table 1). These patients were primarily young (median, 26 years; interquartile range [IQR], 22–31 years) males (97.6%) who were victims of penetrating injury (85.7%). Arterial injuries requiring shunts were severe (Abbreviated Injury Scale score [AIS], 4 [IQR, 3–4]), although vessel location varied. Associated fractures (33.3%) and major nerve (31%) and venous injuries (54.8%) were common. “Damage control surgery” was documented as the most common indication for shunt placement (64.3%), followed by combined vascular and orthopedic procedures (23.8%). Shunt types placed included Argyle (72.5%), thoracostomy tube (17.5%), Sundt (7.5%), and Javid (2.5%) shunts. Most shunts were retained in place for less than 12 hours (71.4%), and only two (4.8%) had dwell times exceeding 48 hours. Local heparin shunt infusions were not utilized, whereas systemic anticoagulation was seldom used (7.1%) during the dwell period. Hemodynamics were frequently compromised prior to or during arterial shunt dwell periods—69% were hypotensive (systolic blood pressure [SBP], <90 mm Hg), 66.7% required vasopressor support, and 19% sustained a cardiopulmonary arrest. Ultimately, 9 (21.4%) of 42 patients requiring arterial shunt placement died during their hospitalization.
Thirty-five patients (83.3%) survived the shunt dwell period and comprise the primary study sample. Demographics and clinical characteristics were compared between those with shunt dwell times of less than 6 hours (n = 19) and more than 6 hours (n = 16). While patients appeared to have a greater injury burden overall in the group with dwell times of more than 6 hours (Table 2), there were no statistical differences between groups with respect to age, gender, initial SBP or hemodynamics during the shunt dwell period, use of vasopressors, AIS of the shunted vessel, Injury Severity Score (ISS), or outcomes including limb amputation or mortality.
Five (14.3%) of the 35 shunt survivors, though, had shunt complications (2 documented shunt thrombosis, three documented distal ischemia during shunt dwell period; Table 3). When patients who developed shunt complications were compared with those who did not, there was no difference with respect to age, injury mechanism, initial SBP, associated injuries, hemodynamics during the shunt dwell period, systemic anticoagulation, AIS of shunted vessel, or ISS (Table 4). Shunts were commonly placed for damage control indications both in patients who developed complications (100%) and those who did not (46.7%; p = 0.05). While all five patients (100%) who developed shunt complications had dwell times exceeding 6 hours, only 11 (36.7%) of 30 of those who did not develop shunt complications had dwell times of more than 6 hours (p = 0.014). Stated another way, no patients (0%) with dwell times of less than 6 hours developed shunt complications, whereas 31.2% (5/16) of those with dwell times of more than 6 hours developed complications (Fig. 1).
The impact of shunt complications on patient outcomes was also assessed. Of five patients who developed shunt complications, two patients (40%) required amputations, and one patient (20%) died. Alternatively, only 2 (6.7%) of 30 patients (p = 0.08) required amputations, and 1 (3.3%) of 30 patients (p = 0.27) in those who did not develop shunt complications died during their hospitalization.
Temporary vascular shunts offer a rapid and effective means of controlling hemorrhage and restoring distal perfusion after major vascular injuries.2–7 Several clinical variables including hypotension, soft tissue and venous injuries, and shunt size, along with technical aspects of placement, are believed to play a role in the development of shunt complications.19 The most important finding of the present study is that shunt complications, defined as shunt dislodgement, shunt thrombosis, and distal ischemia, were related to shunt dwell times. While patients with shunt dwell times of less than 6 hours experienced no shunt-related complications, 31% of those with dwell times of more than 6 hours developed the aforementioned complications.
Shunt dwell time is an important and potentially modifiable clinical variable. Prior data utilizing porcine injury models have confirmed this risk factor.20–23 Aldridge et al.20 resected portions of bilateral iliac arteries of five swine and then placed heparin-bonded shunts. Limb perfusion was assessed at 24 hours with clinical examination and angiography to find that all limbs were well perfused and patent on angiography without distal emboli. Dawson et al.21 studied 16 swine to determine the effects of prolonged shunting on limb perfusion and metabolism after reproducible extremity injury. Swine had their iliac arteries divided, bled to 40% hemorrhage, artery clamped for 60 minutes, and then resuscitated with a temporary vascular shunt placed after 1 hour. Thirteen of 16 shunts remained patent and provided approximately 50% of blood flow to the distal extremity. Ding et al.22 randomized 24 pigs to 3-, 6-, 9-, or 12-hour shunt dwell times after superior mesenteric artery transection, severe hemorrhage, and then resuscitation. Dwell time was directly related to severity of endothelial injury, a clear initiator of platelet aggregation and thrombotic occlusion. The authors concluded that keeping shunt dwell times under 6 hours resulted in reversible rather than permanent endothelial injury with 100% patency rates in their porcine model and recommended that “attempts should be made to keep indwelling times to <6 hours.” Our results, with no shunt complications in the group with dwell times of less than 6 hours, mimic results from these porcine studies.
Shunt dwell times have been documented in several military and civilian case series. In 1982, Johansen et al.8 reported the results of 10 vascular shunts with dwell times ranging from 2 to 6 hours. Later in 1986, Khalil and Livingston9 reported five patients with complex lower-extremity injuries with extensive soft tissue loss, fractures, or other life-threatening injuries managed with temporary vascular shunts. Shunt dwell times ranged from 2 to 8 hours. Oliver et al.16 recently (2013) retrospectively reviewed their experience with temporary vascular shunts to find that 4 of 20 shunts with dwell times of more than 24 hours thrombosed, whereas none of 6 shunts with dwell times of less than 24 hours thrombosed. Inaba et al.,15 in the only civilian, multicenter shunt study to date, analyzed 213 temporary vascular shunts, of which 61% had dwell times of less 6 hours. Overall, 5.6% thrombosed, but there were no independent predictors of shunt thrombosis on univariate or multivariate analysis. Our study, though, focused entirely on factors associated with shunt complications and determined that shunt dwell time was related to shunt complications. While we recognize that hemodynamics, need for further resuscitation, and associated injuries may prevent shunt removal and definitive repair within the 6-hour window in some patients, our results suggest that this 6-hour dwell time threshold is an important objective when clinically feasible.
Location and size of shunted vessel may also play a role in the development of shunt complications. After the Iraq conflict, Rasmussen et al.13 reported on the use of 30 temporary vascular shunts in the management of wartime vascular injury. Shunt dwell times were relatively short (2 hours) and managed without systemic anticoagulation, and patency was related to the caliber of the shunted extremity vessel. Conversely, Subramanian et al.17 reported 67 patients with 101 temporary vascular shunts placed. Thrombosis rates again varied by injury location—4% of extremity shunts thrombosed, whereas 33% (2/6) of truncal shunts thrombosed despite similar dwell times. Although the present report did not include injuries distal to the brachial or popliteal arteries, similar findings were obtained. Three of six patients with torso shunts developed shunt complications, whereas only 2 of 27 with extremity shunts developed complications in the present report.
We acknowledge our study limitations. This study describes the retrospective experience of a single trauma center in urban America. As such, the majority of our study sample was composed of young patients with penetrating trauma, and caution must be exercised before results are extrapolated to other injured populations. Operative decision making such as shunt indication or size of shunt was subject to the discretion of the operating surgeon and was often not documented in the medical record. Lastly, the exact shunt placement and removal times were seldom documented. Thus, to analyze dwell times, we utilized easy-to-categorize elapsed times (e.g., 0–6 hours, 6–12 hours, etc.), with 6 hours chosen as the primary comparison cutoff point because of its clinical utility as a threshold for warm ischemic time after vascular injury.
We recognize that many patients are not clinically ready for formal repair within 6 hours of temporary shunt placement. Our intention was not to state that all patients with arterial shunts should have dwell times of less than 6 hours, but instead that there are risks and consequences associated with prolonged shunt dwell times. These risks must be weighed against the risks associated with formal repair before the patient is clinically optimized on a case-by-case basis. Our study goal is intended to discourage any clinically unnecessary delays in formal repair that often occur in practice.
In summary, 14% of patients with arterial shunts developed shunt-related complications, all occurring in patients with dwell times of more than 6 hours. We conclude that shunt dwell time is directly related to shunt-related complications. Our data suggest that limiting shunt dwell times to less than 6 hours when clinically feasible may decrease adverse outcomes in patients requiring arterial shunting.
S.M. performed literature search, data collection, data analysis, data interpretation, critical revision. B.P.S., J.W.C., P.M.R., and C.W.S. performed data analysis, data interpretation, and critical revision. M.J.S. performed literature search, study design, data analysis, data interpretation, manuscript writing, and critical revision.
The authors declare no conflicts of interest.
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