Anticoagulation with dabigatran does not increase secondary intracerebral haemorrhage after thrombolysis in experimental cerebral ischaemia.

Dabigatran etexilate (DE) has recently been introduced for stroke prevention in atrial fibrillation, but management of acute ischaemic stroke during therapy with DE is a challenge. Thrombolysis is contraindicated because of a presumed increased risk of intracerebral haemorrhagic complications. We studied in different ischaemia models whether DE increases secondary haemorrhage after thrombolysis. C57BL/6 mice were anticoagulated with high-dose DE or warfarin. After 2 hour (h) or 3 h transient filament MCAO, rt-PA was injected. At 24 h after MCAO, secondary haemorrhage was quantified using a macroscopic haemorrhage score and haemoglobin spectrophotometry. Post-ischaemic blood-brain-barrier (BBB) damage was assessed using Evans blue. To increase the validity of findings, the duration of anticoagulation was prolonged in mice (5 x DE over 2 days), and the effect of DE after thrombolysis was also examined in thromboembolic MCAO in rats.Pretreatment with warfarin resulted in significantly more secondary haemorrhage (mean haemorrhage score 2.6 ± 0.2) compared to non-anticoagulated animals (1.7 ± 0.3) and DE (9 mg/kg, 1.6 ± 0.3) in 2 h ischaemia. Also after a 3 h period of ischaemia, haemorrhage was more severe in animals anticoagulated with warfarin compared to 9 mg/kg DE and non-anticoagulated control. Prolonged or enteral dabigatran pretreatment led to identical results. Also, thrombolysis after thromboembolic MCAO in rats did not induce more severe bleeding in DE-treated animals. Mice pretreated with warfarin had higher BBB permeability and increased activation of matrix-metalloproteinase 9. In conclusion, DE does not increase the risk of secondary haemorrhage after thrombolysis in various rodent models of ischaemia and reperfusion. The implications of this finding for stroke patients have to be determined in the clinical setting.

Hemostatic therapy in experimental intracerebral hemorrhage associated with rivaroxaban.

BACKGROUND AND PURPOSE: Rivaroxaban has recently been approved for stroke prevention in atrial fibrillation. However, lack of an effective antidote represents a major concern in the event of intracerebral hemorrhage (ICH). The aims of the present study were to establish a murine model of ICH associated with rivaroxaban, and to examine the effectiveness of different hemostatic factors in preventing excess hematoma expansion. METHODS: In C57BL/6 mice receiving 10 or 30 mg/kg rivaroxaban by gastric gavage, plasma concentration, prothrombin time, and coagulation factor activities were measured repeatedly. Thirty minutes after inducing ICH by intrastriatal collagenase-injection, mice received an intravenous injection of either saline, prothrombin complex concentrate (100 U/kg), murine fresh frozen plasma (200 µL), or recombinant human Factor VIIa (1 mg/kg). ICH volume was quantified on brain cryosections and using hemoglobin spectrophotometry 24 hours later. RESULTS: Rivaroxaban in 30 mg/kg dose substantially increased the hematoma volume in ICH induced by 0.060 U collagenase. Prothrombin complex concentrate, fresh frozen plasma, or Factor VIIa prevented excess hematoma expansion caused by anticoagulation. Prevention of hematoma expansion by prothrombin complex concentrate was dose-dependent. None of the 3 agents completely corrected the prolonged prothrombin time, although they restored the activities of deficient FII and X. CONCLUSIONS: Prothrombin complex concentrate, Factor VIIa, and fresh frozen plasma prevent excess intracerebral hematoma expansion in a murine ICH model associated with rivaroxaban. The efficacy and safety of this reversal strategy must be further evaluated in clinical studies.

Green tea extract ameliorates reperfusion injury to rat livers after warm ischemia in a dose-dependent manner.

SCOPE: Polyphenolic constituents of green tea (Camellia sinensis) have been shown to be potent scavengers of reactive oxygen species (ROS). Thus, this study was designed to assess its effects after liver ischemia-reperfusion. METHODS AND RESULTS: Fasted Sprague-Dawley rats were gavaged with different concentrations of green tea extract (GTE) 2 h before 90 min of warm ischemia of the left lateral liver lobe (30% of liver). Controls were given the same volume of Ringer's solution. A preparation of pentobarbital sodium (intraperitoneal) and ketamine (intramuscular) was used for anesthesia. After reperfusion, transaminases, liver histology, hepatic microcirculation, and both phagocytosis of latex bead particles as well as the expression of tumor necrosis alpha (TNF-α) to index cellular activation were investigated. Furthermore, the expression of superoxide dismutase (Mn-SOD) was assessed. After 90 min of warm ischemia aminotransferase (AST), alanine aminotransferase (ALT), and lactate dehydrogenase (LDH) increased dramatically to 1946 ± 272/3244 ± 757 U/L, 1680 ± 134/2080 ± 379 U/L, and 7857 ± 1851/2036 ± 1193 U/L at 2/6 h, respectively. GTE (200 mg/kgbody weight) significantly prevented this increase in a dose-dependent manner by 21-51% at 2 h and 29-34% at 6 h, respectively. Histology confirmed the protective effects while both TNF-α expression and phagocytosis of latex beads by Kupffer cells (KCs) were significantly reduced. GTE intake significantly increased the expression of manganese superoxide dismutase. In vivo microscopy revealed improved acinar and sinusoidal perfusion after GTE. CONCLUSION: Preconditioning with a single oral dose of GTE ameliorates ischemia-reperfusion injury in liver. Decreased cellular activation and improved microcirculation are the proposed mechanisms.

The use of high-dose melatonin in liver resection is safe: first clinical experience.

Experimental data suggest that melatonin decreases inflammatory changes after major liver resection, thus positively influencing the postoperative course. To assess the safety of a preoperative single dose of melatonin in patients undergoing major liver resection, a randomized controlled double-blind pilot clinical trial with two parallel study arms was designed at the Department of General and Transplantation Surgery, Ruprecht-Karls-University, Heidelberg. A total of 307 patients, who were referred for liver surgery, were screened. One hundred and thirteen patients, for whom a major liver resection (≥3 segments) was scheduled, were eligible. Sixty-three eligible patients refused to participate, and therefore, 50 patients were randomized. A preoperative single dose of melatonin (50 mg/kg BW) dissolved in 250 mL of milk was administered through the gastric tube after the intubation for general anesthesia. Controls were given the same amount of microcrystalline cellulose. Primary endpoint was safety. Secondary endpoints were postoperative complications. Melatonin was effectively absorbed with serum concentrations of 1142.8 ± 7.2 ng/mL (mean ± S.E.M.) versus 0.3 ± 7.8 ng/mL in controls (P < 0.0001). Melatonin treatment resulted in lower postoperative transaminases over the study period (P = 0.6). There was no serious adverse event in patients after melatonin treatment. A total of three infectious complications occurred in either group. A total of eight noninfectious complications occurred in five control patients, whereas three noninfectious complications occurred in three patients receiving preoperative melatonin (P = 0.3). There was a trend toward shorter ICU stay and total hospital stay after melatonin treatment. Therefore, a single preoperative enteral dose of melatonin is effectively absorbed and is safe and well tolerated in patients undergoing major liver surgery.