Administration of andexanet alfa for traumatic intracranial hemorrhage in the setting of massive apixaban overdose: A case report

PURPOSE

Apixaban is a direct-acting oral anticoagulant that selectively inhibits factor Xa. Reversal strategies utilized to treat factor Xa inhibitor-associated bleeding include andexanet alfa, prothrombin complex -concentrate (PCC), and activated PCC (aPCC). The optimal treatment of traumatic intracranial hemorrhage in the setting of an apixaban overdose is unknown.

SUMMARY

This case report describes a 69-year-old female who initially presented to an emergency department at a community hospital due to a ground-level fall with traumatic intracranial hemorrhage. The patient reportedly ingested apixaban 275 mg, carvedilol 250 mg, atorvastatin 1,200 mg, and unknown amounts of amlodipine and ethanol. Anti-inhibitor coagulant complex, an aPCC, was administered approximately 3 hours after presentation. Initial thromboelastography performed approximately 4 hours after presentation showed a prolonged reaction time of 16.8 minutes. Ongoing imaging and evidence of coagulopathy prompted repeated aPCC administration to a cumulative dose of approximately 100 U/kg. The patient underwent craniotomy with hematoma evacuation. Postoperative imaging showed expansion of the existing intracranial hemorrhage and new areas of hemorrhage. Andexanet alfa was administered approximately 18 hours after presentation, followed by repeat craniotomy with evacuation of the hematoma. No further expansion of the intracranial hemorrhage was observed, and the reaction time on thromboelastography was normalized at 6.3 minutes.

CONCLUSION

This case suggests that andexanet alfa may have a role in the management of traumatic hemorrhage in the setting of an acute massive apixaban overdose. Use of andexanet alfa, PCC, and aPCC in this context requires further research.

Impact of premorbid oral anticoagulant use on survival in patients with traumatic intracranial hemorrhage

OBJECTIVE

Although oral anticoagulant use has been implicated in worse outcomes for patients with a traumatic brain injury (TBI), prior studies have mostly examined the use of vitamin K antagonists (VKAs). In an era of increasing use of direct oral anticoagulants (DOACs) in lieu of VKAs, the authors compared the survival outcomes of TBI patients on different types of premorbid anticoagulation medications with those of patients not on anticoagulation.

METHODS

The authors retrospectively reviewed the records of 1186 adult patients who presented at a level I trauma center with an intracranial hemorrhage after blunt trauma between 2016 and 2022. Patient demographics; comorbidities; and pre-, peri-, and postinjury characteristics were compared based on premorbid anticoagulation use. Multivariable Cox proportional hazards regression modeling of mortality was performed to adjust for risk factors that met a significance threshold of p < 0.1 on bivariate analysis.

RESULTS

Of 1186 patients with a traumatic intracranial hemorrhage, 49 (4.1%) were taking DOACs and 53 (4.5%) used VKAs at the time of injury. Patients using oral anticoagulants were more likely to be older (p < 0.001), to have a higher Charlson Comorbidity Index (p < 0.001), and to present with a higher Glasgow Coma Scale (GCS) score (p < 0.001) and lower Injury Severity Score (ISS; p < 0.001) than those on no anticoagulation. Patients using VKAs were more likely to undergo reversal than patients using DOACs (53% vs 31%, p < 0.001). Cox proportional hazards regression demonstrated significantly increased hazard ratios (HRs) for VKA use (HR 2.204, p = 0.003) and DOAC use (HR 1.973, p = 0.007). Increasing age (HR 1.040, p < 0.001), ISS (HR 1.017, p = 0.01), and Marshall score (HR 1.186, p < 0.001) were associated with an increased risk of death. A higher GCS score on admission was associated with a decreased risk of death (HR 0.912, p < 0.001).

CONCLUSIONS

Patients with a traumatic intracranial injury who were on oral anticoagulant therapy before injury demonstrated higher mortality rates than patients who were not on oral anticoagulation after adjusting for age, comorbid conditions, and injury presentation.

Systematic review on traumatic intracranial haemorrhage in patients on anti-thrombotic medications; haemorrhage progression, thrombosis, and anti-thrombotic recommencement

A large number of patients who sustain a traumatic intracranial haemorrhage (tICH) are taking anti-thrombotic (AT) medications at the time of injury. These are stopped acutely, but there is uncertainty about safe timing for recommencement. This review aimed to understand the rate of new/progressive haemorrhage, thrombosis, and death in tICH patients on ATs and the rate and timing of AT recommencement. A systematic review of OVID Medline and EMBASE from 2000 to 2021 including adult patients with tICH on ATs with reported outcomes was performed. A total of 59 observational studies (20,421 patients) were included. Most patients were elderly (mean age 74), suffering falls (78%), and had a mild head injury. The mean new/progressive haemorrhage rate during admission was 26%, mostly diagnosed on routine imaging performed within 72 h of injury, with only 8% clinically significant. Thrombotic events were reported in 17 studies; mean rate of 3% during admission, 4-9% at 30 days and 3-11% at 6 months. AT recommencement rate and timing were only reported in six studies and varied widely, with some studies demonstrating reduced thrombotic events and mortality with earlier AT recommencement. Current data is observational and sparse in relation to haemorrhage, thrombosis, and AT recommencement. There is some suggestion that early recommencement, within 7-14 days, may be beneficial but higher quality studies with more consistent data are urgently required.

Coagulopathy and its effect on treatment and mortality in patients with traumatic intracranial hemorrhage

BACKGROUND

The role of coagulopathy in patients with traumatic brain injury has remained elusive. In the present study, we aim to assess the prevalence of coagulopathy in patients with traumatic intracranial hemorrhage, their clinical features, and the effect of coagulopathy on treatment and mortality.

METHODS

An observational, retrospective single-center cohort of consecutive patients with traumatic intracranial hemorrhage treated at Helsinki University Hospital between 01 January and 31 December 2010. We compared clinical and radiological parameters in patients with and without coagulopathy defined as drug- or disease-induced, i.e., antiplatelet or anticoagulant medication at a therapeutic dose, thrombocytopenia (platelet count < 100 E9/L), international normalized ratio > 1.2, or thromboplastin time < 60%. Primary outcome was 30-day all-cause mortality. Logistic regression analysis allowed to assess for factors associated with coagulopathy and mortality.

RESULTS

Of our 505 patients (median age 61 years, 65.5% male), 206 (40.8%) had coagulopathy. Compared to non-coagulopathy patients, coagulopathy patients had larger hemorrhage volumes (mean 140.0 mL vs. 98.4 mL, p < 0.001) and higher 30-day mortality (18.9% vs. 9.7%, p = 0.003). In multivariable analysis, older age, lower admission Glasgow Coma Scale score, larger hemorrhage volume, and conservative treatment were independently associated with mortality. Surgical treatment was associated with lower mortality in both patients with and without coagulopathy.

CONCLUSIONS

Coagulopathy was more frequent in patients with traumatic intracranial hemorrhage presenting larger hemorrhage volumes compared to non-coagulopathy patients but was not independently associated with higher 30-day mortality. Hematoma evacuation, in turn, was associated with lower mortality irrespective of coagulopathy.

Effects of tranexamic acid on death, disability, vascular occlusive events and other morbidities in patients with acute traumatic brain injury (CRASH-3): a randomised, placebo-controlled trial

BACKGROUND

Tranexamic acid reduces surgical bleeding and decreases mortality in patients with traumatic extracranial bleeding. Intracranial bleeding is common after traumatic brain injury (TBI) and can cause brain herniation and death. We aimed to assess the effects of tranexamic acid in patients with TBI.

METHODS

This randomised, placebo-controlled trial was done in 175 hospitals in 29 countries. Adults with TBI who were within 3 h of injury, had a Glasgow Coma Scale (GCS) score of 12 or lower or any intracranial bleeding on CT scan, and no major extracranial bleeding were eligible. The time window for eligibility was originally 8 h but in 2016 the protocol was changed to limit recruitment to patients within 3 h of injury. This change was made blind to the trial data, in response to external evidence suggesting that delayed treatment is unlikely to be effective. We randomly assigned (1:1) patients to receive tranexamic acid (loading dose 1 g over 10 min then infusion of 1 g over 8 h) or matching placebo. Patients were assigned by selecting a numbered treatment pack from a box containing eight packs that were identical apart from the pack number. Patients, caregivers, and those assessing outcomes were masked to allocation. The primary outcome was head injury-related death in hospital within 28 days of injury in patients treated within 3 h of injury. We prespecified a sensitivity analysis that excluded patients with a GCS score of 3 and those with bilateral unreactive pupils at baseline. All analyses were done by intention to treat. This trial was registered with ISRCTN (ISRCTN15088122), ClinicalTrials.gov (NCT01402882), EudraCT (2011-003669-14), and the Pan African Clinical Trial Registry (PACTR20121000441277).

RESULTS

Between July 20, 2012, and Jan 31, 2019, we randomly allocated 12 737 patients with TBI to receive tranexamic acid (6406 [50·3%] or placebo [6331 [49·7%], of whom 9202 (72·2%) patients were treated within 3 h of injury. Among patients treated within 3 h of injury, the risk of head injury-related death was 18·5% in the tranexamic acid group versus 19·8% in the placebo group (855 vs 892 events; risk ratio [RR] 0·94 [95% CI 0·86-1·02]). In the prespecified sensitivity analysis that excluded patients with a GCS score of 3 or bilateral unreactive pupils at baseline, the risk of head injury-related death was 12·5% in the tranexamic acid group versus 14·0% in the placebo group (485 vs 525 events; RR 0·89 [95% CI 0·80-1·00]). The risk of head injury-related death reduced with tranexamic acid in patients with mild-to-moderate head injury (RR 0·78 [95% CI 0·64-0·95]) but not in patients with severe head injury (0·99 [95% CI 0·91-1·07]; p value for heterogeneity 0·030). Early treatment was more effective than was later treatment in patients with mild and moderate head injury (p=0·005) but time to treatment had no obvious effect in patients with severe head injury (p=0·73). The risk of vascular occlusive events was similar in the tranexamic acid and placebo groups (RR 0·98 (0·74-1·28). The risk of seizures was also similar between groups (1·09 [95% CI 0·90-1·33]).

INTERPRETATION

Our results show that tranexamic acid is safe in patients with TBI and that treatment within 3 h of injury reduces head injury-related death. Patients should be treated as soon as possible after injury.

FUNDING

National Institute for Health Research Health Technology Assessment, JP Moulton Charitable Trust, Department of Health and Social Care, Department for International Development, Global Challenges Research Fund, Medical Research Council, and Wellcome Trust (Joint Global Health Trials scheme).

TRANSLATIONS

For the Arabic, Chinese, French, Hindi, Japanese, Spanish and Urdu translations of the abstract see Supplementary Material.

Systematic Review and Meta-Analysis: Is Pre-Injury Antiplatelet Therapy Associated with Traumatic Intracranial Hemorrhage?

The objective of this systematic review and meta-analysis is to evaluate whether the pre-injury use of antiplatelet therapy (APT) is associated with increased risk of traumatic intracranial hemorrhage (tICH) on CT scan. PubMed, Medline, Embase, Cochrane Central, reference lists, and national guidelines on traumatic brain injury were used as data sources. Eligible studies were cohort studies and case-control studies that assessed the relationship between APT and tICH. Studies without control group were not included. The primary outcome of interest was tICH on CT. Two reviewers independently selected studies, assessed methodological quality, and extracted outcome data. This search resulted in 10 eligible studies with 20,247 patients with head injury that were included in the meta-analysis. The use of APT in patients with head injury was associated with significant increased risk of tICH compared with control (odds ratio [OR] 1.87, 95% confidence interval [CI]1.27-2.74). There was significant heterogeneity in the studies (I2 84%), although almost all showed an association between APT use and tICH. This association could not be established for patients receiving aspirin monotherapy. When considering only patients with mild traumatic brain injury (mTBI), the OR is 2.72 (95% CI 1.92-3.85). The results were robust to sensitivity analysis on study quality. In summary, APT in patients with head injury is associated with increased risk of tICH; this association is most relevant in patients with mTBI. Whether this association is the result of a causal relationship and whether this relationship also exists for patients receiving aspirin monotherapy cannot be established with the current review and meta-analysis.

The efficacy of factor VIIa in emergency department patients with warfarin use and traumatic intracranial hemorrhage

OBJECTIVES

The objective was to compare outcomes in emergency department (ED) patients with preinjury warfarin use and traumatic intracranial hemorrhage (tICH) who did and did not receive recombinant activated factor VIIa (rFVIIa) for international normalized ratio (INR) reversal.

METHODS

This was a retrospective before-and-after study conducted at a Level 1 trauma center, with data from 1999 to 2009. Eligible patients had preinjury warfarin use and tICH on cranial computed tomography (CT) scan. Patients before (standard cohort) and after (rFVIIa cohort) implementation of a protocol for administering 1.2 mg of rFVIIa in the ED were reviewed. Glasgow Coma Scale (GCS) score, Revised Trauma Score (RTS), Injury Severity Score (ISS), INR, and Marshall score were collected. Outcome measures included mortality, thromboembolic complications, and INR normalization.

RESULTS

Forty patients (median age=80.5 years, interquartile range [IQR]=63.5-85) were included (20 in each cohort). Age, GCS score, ISS, RTS, initial INR, and Marshall score were similar (p>0.05) between the two cohorts. Survival was identical between cohorts (13 of 20, or 65.0%, 95% confidence interval [CI]=40.8% to 84.6%). There were no differences in rate of thromboembolic complications in the standard cohort (1 of 20, 5.0%, 95% CI=0.1% to 24.9%) than the rFVIIa cohort (4 of 20, 20.0%, 95% CI=5.7% to 43.7%; p=0.34). Time to normal INR was earlier in the rFVIIa cohort (mean=4.8 hours, 95% CI=3.0 to 6.7 hours) than in the standard cohort (mean=17.5 hours, 95% CI=12.5 to 22.6; p<0.001).

CONCLUSIONS

In patients with preinjury warfarin and tICH, use of rFVIIa was associated with a decreased time to normal INR. However, no difference in mortality was identified. Use of rFVIIa in patients on warfarin and tICH requires further study to demonstrate important patient-oriented outcomes.

Clinical observation of Danhong Injection (herbal TCM product from Radix Salviae miltiorrhizae and Flos Carthami tinctorii) in the treatment of traumatic intracranial hematoma

Danhong Injection (DHI), a Chinese Materia Medica standardized product extracted from Radix Salviae Miltiorrhizae and Flos Carthami tinctorii, has the actions of promoting blood circulation and resolving stasis to promote regeneration. The clinical therapeutic effects of DHI on traumatic intracranial hematoma (TICH) were observed. Eighty patients with TICH were randomly assigned to trial group and a control group (40 patients per group), and all were administered with routine medication. Additionally, DIH was administered intravenously to patients in the trial group. Pre and post-treatment GCS was observed in the two groups, along with GOS after therapy. The intracranial hematoma absorption, hemorheological changes, and changes in coagulation indexes pre- and post-treatment were evaluated. The results indicated that GCS and GOS after therapy for the trial group were superior to those for the control group (p<0.05). There was a significant post-treatment difference in the intracranial hematoma absorption between the two groups (p<0.01). Each hemorheological index in the trial group improved significantly as compared with that of the control group (p<0.05 or p<0.01). The plasma levels of fibrinogen and D-dimer in the trial group were significantly decreased after therapy (p<0.01). These results suggest that DHI is conducive to the recovery of patients with TICH.

Cerebrospinal s100-B: a potential marker for progressive intracranial hemorrhage in patients with severe traumatic brain injury

OBJECTIVE

Traumatic brain injury (TBI) is associated with cerebrovascular dysfunction and changes of the blood-brain barrier (BBB) function. Although knowledge about the function of the BBB would be of high interest, non-invasive neurodiagnostic tools are still lacking. In this context it has been shown, that the astrocytic protein S100-B is a significant parameter for neuronal damage. However, there is only poor knowledge about the dynamics of S100-B in cerebrospinal fluid (CSF) and serum of patients with severe TBI. Therefore, the aim of this study was to analyze intrathecal and systemic concentrations of S100-B in patients with severe TBI in correlation to the development of progressive intracranial hemorrhage (PIH) as well as to the CSF/serum albumin ratio (Q subsetalb), as functional parameter of the BBB.

PATIENTS AND METHODS

In patients, suffering from severe TBI (GCS =or<8pts) and respectively healthy control patients, albumin for calculating the CSF/serum albumin ratio (Q subsetalb) as well as S100-B protein were analyzed in CSF and serum. Samples were collected immediately after placement of a ventricular catheter and 12h, 24h, 48 h and 72 h after TBI. S100-B was quantified using Elecsys S-100 superset assay (Roche superset Diagnostics; Mannheim, Germany). Volume measurements of focal mass lesions based on CT images taken during the first 72 h after TBI were obtained according to the Cavalieri's Direct Estimator method.

RESULTS

21 TBI-patients and respectively 10 healthy controls were enrolled. In patients exhibiting a mean ICP >15 mmHg (n = 15) CSF levels of S100-B were significantly increased on admission (819 +/- 78 pg/ml) compared to patients with ICP =or<15 mmHg (n = 6, 175 +/- 12 pg/ml) as well as to the control group (n = 10, 0.8 +/- 0.09 pg/ml). In the group with ICP >15 mmHg 8 patients developed PIH A positive correlation was found between CSF S100-B and ICP (r2 = 0.925, p<0.001). Furthermore a positive correlation between serum S100-B and Q subsetalb was found for each sampling point (r superset2 = 0.793, p<0.001).

CONCLUSIONS

The cerebrospinal and serum concentration of S100-B in patients with severe TBI was evaluated. Monitoring cerebrospinal S100-B might help to prospectively identify patients with PIH.

Effects of Recombinant Activated Factor VII in Traumatic Nonsurgical Intracranial Hemorrhage

OBJECTIVE

To determine whether treatment with recombinant activated factor VII (rFVIIa) will prevent progression of bleeding in nonsurgical hemorrhagic traumatic brain injury (TBI).

METHODS

Chart review from the trauma registry of a level 1 trauma center between January 1, 2002 and December 31, 2004 identified 2 patients who received rFVIIa for progressive hemorrhagic TBI. These patients were given a single dose of rFVIIa (120 mcg/kg) after a repeat head computed tomography (CT) scan showed worsening of intracranial bleeding. Pre-rFVIIa and post-rFVIIa coagulation parameters and postintervention CT scans were performed. A matched convenience sample was drawn from the institution's trauma registry reflecting similar injury patterns.

RESULTS

The 2 patients who received rFVIIa were ages 61 and 79 years; the patients in the matched convenience sample were 57 and 63 years. Both sets of patients comprised 1 man and 1 woman who had suffered blunt trauma, including hemorrhagic TBI, and were matched according to age, gender, and injury severity score (ISS). During their hospital course, repeat CT scans documented worsening of intracranial hemorrhage in both cohorts. In the rFVIIa patients, follow-up CT showed overall improvement of head injury compared with the convenience sample. The rFVIIa patients also saw an appreciable decrease in both prothrombin time (PT) and international normalized ratio (INR).

CONCLUSIONS

In hemorrhagic TBI, rFVIIa has the potential to limit or even halt the progression of bleeding that would otherwise place growing pressure on the brain. A prospective, randomized multicenter trial is planned to elucidate this hypothesis.

[Local fibrinolytic technique in surgery of traumatic inctracranial hemorrhages]

The emergence of neuroimaging techniques and new surgical technologies (neuroendocopy, navigation systems) in neurosurgery has substantially changed views of surgery for traumatic intracranial hematomas. The local fibrinolytic technique that has been applied to 40 victims aged 18 to 67 years (mean age 42.1 +/- 2 years) who had 18-to-97-cm3 hematomas is a promising direction of mini-invasive surgery for traumatic intracranial hematomas in patients in the compensated and subcompensated state. There were 32 males and 8 females. The procedure of the surgical intervention involves drainage of intracranial hematoma, followed by clot lysis and liquid blood aspiration along the drainage. A good outcome with a complete hematoma removal and clinical symptom regression was observed in 26 patients, a fair result with preservation of moderate neurological symptoms at hospital discharge was noted in 2 patients; 3 victims died. Recurrent bleedings were seen in 4 patients with epidural hematomas. A morphological study revealed the typical features of the morphogenesis of traumatic hematomas and perifocal brain tissue during local fibrinolytic therapy, which suggests that the area of damaging effect of bleeding on the adjacent brain tissue is decreased. Local fibrinolysis in surgery of traumatic intracranial hematomas may be considered to be one of the promising lines of treatment policy along with the existing traditional and current techniques and may be used as the method of choice in surgery of traumatic intracranial hematomas in patients in the compensated state. Removal of epidural hematomas through local fibrinolysis should be limited due to a high risk of recurrent hemorrhage and may be made only in a restricted contingent of patients with severe concomitant injury and concurrent somatic diseases when the risk of combined anesthesia and that of a longer operation are rather high. Moreover, of promise is that subtentorial epidural hematomas may be aspirated without trepanation of the posterior cranial fossa and the surgery may be performed under local anesthesia.

Effects of Antiplatelet Agents on Outcomes for Elderly Patients With Traumatic Intracranial Hemorrhage

BACKGROUND

Recent literature on elderly patients with traumatic intracranial hemorrhage receiving preinjury antiplatelet agents shows a mortality rate of 47%.

METHODS

In a retrospective analysis, patients older than 50 years presenting to the hospital over the past 4 years with traumatic intracranial hemorrhage and the use of aspirin, clopidogrel, or a combination were compared with a control group that had hemorrhage but no antiplatelet medications. Patient demographics, mechanism of injury, and injury scores were recorded.

RESULTS

No significant differences were found between the 90 study patients and the 89 control subjects in terms of demographics, mechanism of injury, Injury Severity Score, Glasgow Coma Score, or hospital length of stay. Patients receiving antiplatelet therapy had significantly more comorbid conditions (71% vs. 35%; p < 0.001). In this series, 21 study patients and 8 control patients died (23% vs. 8.9%; p = 0.016). Age older than 76 years and a Glasgow Coma Score lower than 12 were correlated significantly with increased mortality.

CONCLUSIONS

The use of antiplatelet agents with elderly trauma patients significantly increases the risk of mortality when head injury involves intracranial hemorrhage.

The use of recombinant activated factor VII in three patients with central nervous system hemorrhages associated with factor VII deficiency

BACKGROUND

Recombinant activated factor VII (rFVIIa) is being tested to improve hemostasis in a variety of bleeding disorders. Clinical indications and efficacy are still being evaluated for this product.

CASE REPORT

Over a 17-month period, rFVIIa was used to treat central nervous system hemorrhage in three patients who were found to have isolated FVII deficiency (21%, 40%, 27%). Patient A fell 30 feet, Patient B suffered a motor vehicle accident, and Patient C had a spinal cord hematoma. None of the patients had a history of bleeding diathesis. All three patients received rFVIIa after failing initial treatment with fresh-frozen plasma.

RESULTS

Patient A was treated with 11 doses (initial dose 95 microg/kg; subsequent doses 8-38 microg/kg) over 10 days; Patient B received 13 doses (45-60 microg/kg) over 13 days; and Patient C received 5 doses (12-24 microg/kg) over 4 days. The prothrombin time corrected from 16.2 +/- 1.8 (mean +/- SD) to 11.2 +/- 1.6 seconds after infusion of rFVIIa, but returned to pretreatment level in 14 +/- 4 hours. At the cessation of therapy, all patients showed neurologic improvement. No complications related to the infusion of rFVIIa occurred.

CONCLUSION

The use of rFVIIa may be of value both for its general effect on hemostasis, and specifically in the setting where there is a documented reduction in FVII. Doses lower than those used in patients with FVIII inhibitors appear to be effective in the setting of central nervous system hemorrhage.

Inhibition of poly(ADP-ribose) synthetase improves vascular contractile responses following trauma-hemorrhage and resuscitation

Hyporeactivity of vessels to constrictor agents is thought to contribute to cardiovascular decompensation following trauma-hemorrhage and resuscitation. In this study, we determined if inhibition of poly(ADP-ribose) synthetase (PARS) activity prevented the development of vascular hyporeactivity in rats following trauma-hemorrhage and resuscitation. Trauma consisted of a laparotomy that was closed and rats were hemorrhaged into a reservoir containing citrate to 40 mm Hg for 90 min. Resuscitation included 2/3 of the shed blood plus 2 1/3 of the shed volume as Ringer's lactate. Sham animals received the laparotomy and were time-matched. Induction of iNOS was assessed by reverse transcription-polymerase chain reaction (RT-PCR). Aortic rings isolated 6 h after the initiation of hemorrhage (4.5 h after resuscitation) showed decreased responsiveness to norepinephrine (peak developed tension 0.31+/-0.01 g/mg tissue) compared with sham rings (0.43+/-0.02 g/mg tissue), but no change in EC50 for this response (approximately 5x10(-8) M). Addition of the PARS inhibitor, 3-aminobenzamide, at the onset of resuscitation prevented the decrease in response of aortic rings. The addition of the structural analogue, 3-aminobenzoic acid, which does not inhibit PARS, did not prevent the decrease in vascular reactivity. These agents did not alter vascular responses to norepinephrine in sham animals. iNOS induction was not associated with depressed contractile function. These results indicate that decreased vascular reactivity was prevented by inhibition of PARS and that PARS activation was independent of iNOS induction following trauma-hemorrhage and resuscitation.