Cellular, hemostatic, and inflammatory parameters of the surgical stress response in pigs undergoing partial pericardectomy via open thoracotomy or thoracoscopy

Staphylococcus epidermidis sepsis induces hypercoagulability in preterm pigs

Gram positive bacteria are a cause of sepsis in human preterm infants, and associates with high mortality and hemostatic dysfunction. It is unknown whether bovine colostrum may protect against sepsis and prevent hemostatic dysfunction. The current study was part of an overall sepsis study investigating Staphylococcus epidermidis (SE) induced sepsis in premature pigs including investigation of the effect of feeding bovine colostrum. The specific hypothesis of this study was that the hemostatic response would be hypercoagulable in septic pigs compared to non-infected controls, and that feeding bovine colostrum would increase the hypercoagulant response. Thromboelastography, activated partial thromboplastin time, prothrombin time and fibrinogen concentration were characterized in SE infected pigs, SE infected pigs fed bovine colostrum, and uninfected controls. All pigs were followed for 24 h. In addition, the same parameters were evaluated in a group of premature pigs and a group of full born pigs all followed for 11 days. SE septic premature pigs were characterized by increased clot strength and decreased fibrinolysis, significantly low platelet count and high fibrinogen concentration. Feeding bovine colostrum did not affect the hemostatic response. Compared to full born pigs, preterm newborn pigs demonstrated reduced clot strength, prolonged prothrombin time and low fibrinogen concentration. In all pigs, the fibrinogen concentration increased 11 days post-partum. To conclude, SE induced sepsis in premature pigs resulted in hypercoagulability. Bovine colostrum did not mitigate the hemostatic response. A hypocoagulable hemostatic response was present in healthy preterm pigs compared to full born pigs, similar to previous reports in infants.

Hemodynamic and Hematologic Effects of Histotripsy of Free-Flowing Blood: Implications for Ultrasound-Mediated Thrombolysis

PURPOSE

To investigate the extent and consequences of histotripsy-induced hemolysis in vivo.

MATERIALS AND METHODS

Porcine femoral venous blood was treated with histotripsy in 11 animals with systemic heparinization and 11 without heparin. Serum and hemodynamic measurements were obtained at 0, 2, 5, 10, 15, and 30 minutes and 48-72 hours after the procedure. Fisher exact test was used to determine differences in mortality between heparinized and nonheparinized groups. A linear mixed effects model was used to test for differences in blood analytes and hemodynamic variables over time.

RESULTS

Of 11 animals in the nonheparinized group, 5 died during or immediately after histotripsy (45% nonheparin mortality vs 0% heparin mortality, P = .035). Serum hematocrit, free hemoglobin, lactate dehydrogenase (LDH), and right ventricular systolic pressure changed significantly (P < .001) over the treatment time. Serum hematocrit decreased slightly (from 32.5% ± 3.6% to 29.4% ± 4.2%), whereas increases were seen in free hemoglobin (from 6.2 mg/dL ± 4.6 to 348 mg/dL ± 100), LDH (from 365 U/L ± 67.8 ± to 722 U/L ± 84.7), and right ventricular systolic pressure (from 23.2 mm Hg ± 7.2 to 39.7 mm Hg ± 12.3). After 48-72 hours, hematocrit remained slightly decreased (P = .005), whereas LDH and free hemoglobin remained slightly increased compared with baseline (both P < .001).

CONCLUSIONS

Intravascular histotripsy applied to free-flowing venous blood is safe with systemic heparinization, causing only transient hemodynamic and metabolic disturbances, supporting its use as a future noninvasive thrombolytic therapy modality.

Disseminated intravascular coagulation in a novel porcine model of severe Staphylococcus aureus sepsis fulfills human clinical criteria

Sepsis is a common and often fatal complication in human patients in intensive care units. Relevant and well characterized animal models of sepsis may provide valuable information on pathophysiological mechanisms and be a mean of testing new therapeutic strategies. Large animal models of Staphylococcus aureus sepsis are rare, even though S. aureus increasingly affects human patients. Sepsis changes the haemostatic balance and leads to endothelial cell (EC) activation, coagulopathy and, in severe cases, disseminated intravascular coagulation (DIC). The aim of this study was to characterize the haemostatic and vascular alterations in a novel porcine model of severe S. aureus sepsis, investigating whether the changes fulfill the human clinical criteria for DIC. Five pigs were inoculated intravenously with S. aureus and two control animals were sham-inoculated. Blood samples were collected for thromboelastography (TEG) and assessment of plasma-based haemostatic parameters. Tissue was collected for histopathology and reverse transcriptase quantitative real-time polymerase chain reaction for measurement of mRNA encoding EC markers. All infected animals developed DIC; including procoagulant activation represented by hypercoagulable TEG profiles and prolonged clotting time. Histologically, numerous pulmonary thrombi were present in one pig. Inhibitor consumption was represented by decreasing antithrombin levels in infected pigs. Hyaline globules were found in three infected pigs, confirming fibrinolytic activation. EC activation was identified by expression of von Willebrand factor in small vessels together with elevated mRNA encoding activated EC markers. Severe haemostatic and vascular changes fulfilling the human criteria for DIC were therefore seen in all infected pigs. A tendency towards uncompensated DIC was seen in two animals.

Evaluation of inflammatory and hemostatic surgical stress responses in male cats after castration under general anesthesia with or without local anesthesia

OBJECTIVE

To characterize acute inflammatory and hemostatic surgical stress responses following castration in cats and to evaluate whether the addition of local anesthesia to the anesthetic protocol attenuates these responses.

ANIMALS

39 male cats.

PROCEDURES

Cats undergoing castration were randomly assigned to 2 groups: both groups underwent surgery with general anesthesia, and 1 group additionally received a local anesthetic (lidocaine [2.0 mg/kg in total, divided intratesticularly and SC]) prior to incision. Blood samples were collected after anesthetic induction (baseline) and 1, 5, and 24 hours later. Thromboelastography and coagulation variables (activated partial thromboplastin time [aPTT] and prothrombin time [PT]) were analyzed; fibrinolysis was assessed with plasma D-dimer concentrations. The acute-phase response was evaluated via measurement of plasma fibrinogen and serum amyloid A (last time point, 28 hours) concentrations. Hematologic variables were analyzed at baseline and 1, 5, and 24 hours later.

RESULTS

Evidence of hemostatic and inflammatory activation after surgery was detected in both groups. Maximum amplitude and G (global clot strength) were significantly increased at 24 hours, and significant, but not clinically relevant, decreases were detected in aPTT at 5 and 24 hours and in PT at 24 hours, compared with baseline values. Serum amyloid A concentrations were significantly higher at 24 and 28 hours than at baseline, and plasma fibrinogen concentration was significantly increased at 24 hours; WBC and RBC counts and Hct were significantly increased at multiple time points. No differences between groups were detected for any variables.

CONCLUSIONS AND CLINICAL RELEVANCE

Castration appeared to induce hypercoagulability and an acute-phase inflammatory response in cats. Local anesthesia with lidocaine did not attenuate this response.

Impact of retransfusion of blood processed in cell-saver on coagulation versus cardiopulmonary bypass: a prospective observational study using thromboelastography

AIMS

To compare an impact of retransfusion of blood processed in cell-saver (CS) with that of cardiopulmonary bypass (CPB) on blood coagulation in patients undergoing cardiac surgery.

METHODS

Prospective observational study using thromboelastography (TEG).

RESULTS

TEG samples from 170 patients were analyzed. Cardiopulmonary bypass was used in 100 patients while 70 patients were operated off-pump. In 20 off-pump patients collected blood was processed by cell-saver and returned. In all patients clot formation after heparin neutralization by protamine was unimpaired. However, there was a significant increase in fibrinolysis defined by the TEG parameter Lysis time 30 min after the maximum amplitude of the clot was reached (Ly30) in groups with CPB or CS but this increase still did not exceed the threshold for clinical fibrinolysis (Ly30 > 7.5%). In the group without CPB there was no significant impact on coagulation.

CONCLUSION

Surgery that avoids CPB and/or CS is the gentlest method for inducing blood coagulation.

Noninvasive treatment of deep venous thrombosis using pulsed ultrasound cavitation therapy (histotripsy) in a porcine model

PURPOSE

This study evaluated histotripsy as a noninvasive, image-guided method of thrombolysis in a porcine model of deep vein thrombosis. Histotripsy therapy uses short, high-intensity, focused ultrasound pulses to cause mechanical breakdown of targeted soft tissue by acoustic cavitation, which is guided by real-time ultrasound imaging. This is an in vivo feasibility study of histotripsy thrombolysis.

METHODS AND MATERIALS

Acute thrombi were formed in the femoral vein of juvenile pigs weighing 30-40 kg by balloon occlusion with two catheters and thrombin infusion. A 10-cm-diameter 1-MHz focused transducer was used for therapy. An 8-MHz ultrasound imager was used to align the clot with the therapy focus. Therapy consisted of five cycle pulses delivered at a rate of 1 kHz and peak negative pressure between 14 and 19 MPa. The focus was scanned along the long axis of the vessel to treat the entire visible clot during ultrasound exposure. The targeted region identified by a hyperechoic cavitation bubble cloud was visualized via ultrasound during treatment.

RESULTS

Thrombus breakdown was apparent as a decrease in echogenicity within the vessel in 10 of 12 cases and in 7 cases improved flow through the vein as measured by color Doppler. Vessel histology found denudation of vascular endothelium and small pockets of hemorrhage in the vessel adventitia and underlying muscle and fatty tissue, but perforation of the vessel wall was never observed.

CONCLUSIONS

The results indicate histotripsy has potential for development as a noninvasive treatment for deep vein thrombosis.

Intraoperative blood salvage and retransfusion from citrate treated wounds is safe and feasible

OBJECTIVES

Allogenic blood transfusions are associated with increased morbidity and mortality in surgical patients. The study objective was to investigate the feasibility and safety of intraoperative autotransfusion of unwashed shed whole blood using a novel method.

DESIGN

Twenty pigs were randomised to autotransfusion or crystalloid volume replacement. In two separate surgical wounds, the surfaces and 400 ml of shed blood were treated in situ with citrate, delivered with an equipment transforming suction to positive pressure. Central haemodynamics were monitored with a pulmonary artery catheter. Effects on oxygen-carrying capacity, formed blood elements, haemolysis, inflammation, metabolism, and coagulation were evaluated with biochemical analyses.

RESULTS

No clinically relevant adverse effects on haemodynamics were encountered, apart from a decrease in cardiac output and mixed venous saturation similar to that in control animals. Haemoglobin level was better preserved in the autotransfused group (97 vs. 86 g/L, p=0.0007). There were no major differences in biochemical variables and no macroscopic clot formation precluding autotransfusion.

CONCLUSIONS

The technique was safe and feasible for intraoperative blood salvage and autotransfusion. Haemodynamics and biochemical variables were similar to controls. The technique warrants further studies in humans, as it may contribute towards a reduction of allogenic blood transfusions.