Platelet functions and haemostasis parameters in pigs: absence of side effects of a procedure of general anaesthesia

Effective, safe and efficient porcine model of Forrest Ib bleeding gastric and colonic ulcers

BACKGROUND

Developing effective gastrointestinal (GI) bleeding animal models is necessary to advance endoscopic hemostasis methods and train endoscopists on their use. Our aim, therefore, was to develop an effective and safe porcine GI bleeding model in the stomach and colon of large and small-sized oozing-type ulcers.

METHODS

Gastric and colonic bleeding ulcers were created using either a hybrid endoscopic submucosal dissection (ESD) technique or a cap-assisted endoscopic mucosal resection (EMR-C) technique in 14 pigs. Prior to ulcer creation, animals were treated with either oral apixaban or intravenous (IV) unfractionated heparin anticoagulation in combination with clopidogrel and aspirin. The primary outcome was the technical success of inducing oozing-type Forrest Ib bleeding ulcers. Secondary outcomes included ulcer diameter, number, creation time and the number of complications associated with each technique.

RESULTS

Using hybrid ESD and IV heparin anticoagulation, bleeding was observed in 21/23 (91.3%) gastric ulcers and 6/7 (85.7%) colonic ulcers created. The mean diameter and ulcer creation time were 2.3 ± 0.3 cm and 5.3 ± 0.5 min, respectively, for gastric ulcers and 2.2 ± 0.4 cm and 4.06 ± 0.6 min, respectively, for colonic ulcers. Using EMR-C and IV heparin anticoagulation, bleeding was observed in 14/15 (93.3%) gastric ulcers and 6/6 (100%) colonic ulcers created. The mean diameter and ulcer creation time were 0.8 ± 0.2 cm and 2.1 ± 0.5 min, respectively, for gastric ulcers and 0.7 ± 0.2 cm and 1.7 ± 0.3 min, respectively, for colonic ulcers. None of the ulcers created in animals anticoagulated with apixaban developed bleeding. None of the 14 pigs developed any complications.

CONCLUSION

We have demonstrated the effectiveness and safety of a porcine GI bleeding model utilizing IV heparin anticoagulation and either hybrid ESD or EMR-C techniques to create oozing-type bleeding ulcers in the stomach and colon with customizable size.

Platelets Do Not Alter Flow-Mediated Dilation or Arterial Conduction in vivo

The aim of this study was to investigate whether platelets contribute to shear stress and vascular conductance in the iliac vascular bed in vivo. Flow-mediated dilation of pig iliac was induced by downstream injection of acetylcholine (50 μg), and separately, conductance (ΔF/ΔP) was calculated. This was carried out before and after removal of 1 L of arterial blood in 240 mL increments, and each 240 mL was spun in a centrifuge (1,500 rcf for 7 min); platelet-rich plasma was replaced with equal volume of heparinised saline and reinjected. The circulating platelet count fell from 369 × 109/L (n = 5) to 165 × 109/L (p = 0.01; n = 4; Student's unpaired t). An increase in flow led to an increase in the iliac diameter by 0.49 ± 0.03 mm (mean ± SEM) before platelet reduction and 0.55 ± 0.05 mm after (p = 0.36, Student's paired t, n = 5); the change in arterial conductance was also not significantly affected by platelet reduction, control: 1.44 ± 0.34 mL/min/mm Hg, after platelet reduction: 1.39 ± 0.04 mm (p = 0.55, Student's paired t, n = 4). Therefore, platelets do not contribute to shear stress or conductance in vivo.

Reference Intervals for and the Effects of Sample Handling and Sex on Rotational Thromboelastometry in Healthy Adult Pigs

Accurate assessment of coagulation in porcine studies is essential. We sought to establish normal values for porcine rotational thromboelastometry (ROTEM) according to the American Society for Veterinary Clinical Pathology guidelines and to assess the effects of various preanalytical parameters on those measurements. Healthy Yorkshire-cross pigs (n = 81; 46 males and 35 females) were anesthetized. By using a 18-gauge needle attached to a vacuum phlebotomy tube, blood was acquired from the cranial vena cava. Tubes were filled in the following order: evacuation clot tube, EDTA tube, heparin tube, and 2 citrate tubes. The citrate tubes were randomly assigned to 30 min with or without constant agitation on a rocker. The following parameters were reported according to the manufacturer's recommendations: clotting time, clot formation time, α, (tangent to the clot formation curve when the clot firmness is 20 mm), clot firmness after 10 and 20 min, maximal clot firmness, maximum lysis, and lysis indexes at 30 and 45 min. Reference intervals were reported as mean ± 2 SD (parametric distribution) or 2.5th and 97.5th percentile of the population's results (nonparametric distribution). The effects of sex, sampling order, and agitation on ROTEM results were analyzed through linear regression. Neither sex nor sample agitation influenced any of the ROTEM parameters. Combined reference intervals were established for each ROTEM parameter by pooling data from the nonagitated tubes for both male and female pigs. This study is the first to establish ROTEM reference intervals from a large number of male and female adult Yorkshire-cross pigs and to provide a detailed description of preanalytical sample processing.

A refined experimental model of fusiform aneurysms in a rabbit carotid artery

OBJECTIVE

Reliable animal models are an important aspect of translational research, especially for relatively uncommon clinical entities such as fusiform aneurysms. While several animal models exist, very few are tailored to cerebral fusiform aneurysms, which have unique attributes compared to abdominal fusiform aneurysms. The authors aimed to build from previous models to create a cerebral fusiform aneurysm model that is simple to use and reliable.

METHODS

Twelve female New Zealand White rabbits were assigned to 3 groups: group E, elastase only; group C, CaCl2 only; group EC, elastase + CaCl2. All rabbits underwent surgical exposure of the right common carotid artery (CCA) and 20 minutes of peri-carotid incubation with their respective chemicals. Angiography was performed 6 weeks later for arterial dilation measurements, with 50% increase in diameter being defined as fusiform aneurysm formation. The arterial segments, along with the contralateral CCAs, were harvested and assessed histologically for wall component measurements and elastin semiquantification. A separate rabbit underwent aneurysm creation per the group EC protocol and was treated with an endovascular flow-diversion device.

RESULTS

All of the group EC rabbits developed fusiform aneurysms (mean dilation of 88%), while none of the group E or group C rabbits developed aneurysms (p = 0.001). Histological analysis revealed increased internal elastic lamina fragmentation in the group EC aneurysms, which also had less tunica intima hyperplasia. All aneurysms exhibited thinning of the tunica media and reduction in elastin content. The use of an endovascular flow-diverting stent was successful, with complete parent vessel remodeling, as expected, 4 weeks after deployment.

CONCLUSIONS

The peri-arterial application of combined elastase and CaCl2 to the CCA appears sufficient to reliably produce fusiform aneurysms after 6 weeks. Exposure to elastase or CaCl2 individually appears insufficient, despite the observed histological changes to the arterial wall. The proposed fusiform aneurysm model is able to accommodate endovascular devices, simulating the tortuous pathway experienced in using such devices in human cerebral aneurysms and thus is a satisfactory model to use in translational research.

Evaluation of a Chitosan Hemostat in a Porcine Laparoscopic Partial Nephrectomy Model: A Pilot Study

Background and Objective: The ideal hemostatic agent for laparoscopic partial nephrectomy (LPN) would provide complete hemostasis and sealing of the collecting system at a low cost. Chitosan (CS) is an established topical hemostatic agent, but standard sterilization techniques affect its functional and biologic properties, thereby preventing parenteral uses. This study sought to characterize the safety and efficacy of an implanted CS hemostat sterilized with either a standard technique, electron beam (e-beam) irradiation, or a novel technique, nonthermal nitrogen plasma, in a porcine LPN model. Methods: Laparoscopic partial nephrectomies were performed on six farm pigs and hemostasis achieved using only a CS hemostatic agent (Clo-Sur P.A.D.) that was e-beam (n = 3) or plasma sterilized (PS) (n = 3). Number of pads needed to achieve hemostasis, estimated blood loss, operative time, mass of kidney resection, and warm ischemia time were measured. Animals were monitored for 14 weeks and at harvest, retrograde ureteropyelography and histologic analysis were performed. Results: Complete hemostasis and collection system sealing were achieved in both groups. There was a trend toward less pads required for hemostasis (p = 0.056) and reduced blood loss (p = 0.096) with PS pads, although this did not achieve statistical significance. No complications were observed for 14 weeks and gross examination showed the implanted CS was encapsulated in a fibrous capsule. Histologic analysis revealed a healed nephrectomy site with residual CS and associated chronic inflammation, reactive fibrosis, and foreign body giant cell formation. Importantly, the adjacent renal tissue was intact and viable with no residual parenchymal inflammation or cytologic damage. Conclusion: CS pads alone provided safe and effective hemostasis in a porcine LPN model. PS may enhance hemostatic efficacy and resorption compared with e-beam.

A novel experimental thrombotic myocardial infarction and primary angioplasty model in swine

AIMS

We sought to develop a reproducible animal model for acute myocardial infarction (AMI) in adult atherosclerosis-prone pigs.

METHODS AND RESULTS

A coil was placed in the right coronary artery or the left anterior descending artery in 26 downsized spontaneously hypercholesterolaemic pigs and left untreated until thrombotic occlusion. Then, we crossed the thrombotic occlusion with a guidewire, followed by predilatation, thrombus visualisation with optical coherence tomography (OCT) imaging and, finally, deployment of a stent and repeated OCT. After revascularisation, we calculated the index of microcirculatory resistance (IMR). After a feasibility phase (six animals), acute thrombotic occlusion was achieved in all 20 pigs. Eighteen animals were successfully revascularised and survived until sacrifice. Thrombus formation was confirmed by OCT, measurement of thrombin-antithrombin complexes and pathology examination. Myocardial necrosis was confirmed by troponin T elevation, myocardial staining and pathology examination. Distal thrombotic embolisation and microvascular obstruction were supported by increased IMR and pathology examination.

CONCLUSIONS

A porcine model of thrombotic occlusion AMI in miniaturised adult spontaneously atherosclerosis-prone pigs is feasible by percutaneous intracoronary placement of a coil. The reperfusion by angioplasty completed this model which mirrors human pathological conditions with myocardial infarction, necrosis and distal embolisation.

Efficacy of a three-day training course in endoscopic submucosal dissection using a live porcine model: a prospective evaluation

Background

Endoscopic submucosal dissection is currently regarded as the method of choice for the resection of superficial tumours. The objective of our study was to evaluate prospectively the efficiency of an endoscopic submucosal dissection training course using live anaesthetised pigs.

Methods

Fourteen novice endoscopists participated in three gastric endoscopic submucosal dissection training courses on anaesthetised pigs. Each trainee resected five 'fake' antral lesions. Resected specimen sizes, endoscopic submucosal dissection speeds and the complication rate were evaluated prospectively.

Results

Among the 70 procedures performed, 58 could be analysed. There was a strong increase in endoscopic submucosal dissection speed (from 9.7 mm²/minute to 30.4 mm²/minute) during the sessions, marked between the first two endoscopic submucosal dissections compared with the fourth and fifth. There was a significant relation between the surface area of the resected lesion and procedure speed (P < 0.0001). The complication rate was 8.6%.

Conclusion

There is a clear benefit from endoscopic submucosal dissection training courses on animal models. Improved endoscopist capability is evident from the third endoscopic submucosal dissection. These data validate the indispensable nature of dedicated training courses and echo the European Society of Gastrointestinal Endoscopy proposition for multistep learning, beginning on animal models.

Long Term Outcome after Application of the Angio-Seal Vascular Closure Device in Minipigs

Minipigs are frequently used in (neuro-)interventional research. Longitudinal experiments may require repeated vessel access via the femoral artery. Anticoagulation and incompliance of the animals necessitates the use of a vascular closure device (VCD). The effects of the Angio-Seal VCD in minipigs were longitudinally assessed. Minipig (42±8.4 kg body weight) femoral arteries were sealed using the 8F (n = 6) or 6F (n = 7) Angio-Seal VCD. The pre-interventional femoral artery diameter was 5.1±0.4 mm (4.3–5.8 mm). Sealed puncture sites were analysed angiographically as well as by computed tomography angiography (CTA) for a mean period of 14.1±8.0 weeks (1–22 weeks). All animals were constantly treated with acetylsalicylic acid (ASS) (450 mg/d (n = 7) or 100 mg/d (n = 1)) and clopidogrel (75 mg/d (n = 8)). Non-instrumented (n = 2) and arteries sealed using the VCD (n = 2) were examined histologically. No postoperative hemorrhagic complications were observed. Three arteries were occluded after VCD placement (1 animal diagnosed after 4 weeks (8F), 2 animals after 1 week (6F)) and remained so until the end of the experiments after 22, 12 and 4 weeks, respectively. In one artery a 50% stenosis 8 weeks after application of a 6F Angio-Seal was detected. In 69.2% (n = 9) the VCD was applied without complications. Histopathological analysis of the sealed arterial segments showed subtotal obliteration of the vessel lumen, formation of collagenous tissue and partial damage of the internal elastic lamina. The Angio-Seal VCD prevents relevant hemorrhagic complications in minipigs treated with dual platelet inhibition, but is associated with increased vessel occlusion rates.

Topical hemostatic powder promotes reepithelialization and reduces scar formation after extensive esophageal mucosal resection

The development of techniques for endoscopic resection has provided new strategies for radical conservative treatment of superficial esophageal neoplasms, even those that are circumferential, such as Barrett's neoplasia. However, it is necessary to prevent the formation of scar tissue that can be responsible for esophageal strictures following circumferential resection. Preliminary data have suggested the possible efficacy of a hemostatic powder in the promotion of wound healing. The study aims to assess the effectiveness of Hemospray (Cook Medical) in a swine model of post-endoscopic esophageal stricture. Our prospective controlled study included 21 pigs. A 6-cm circumferential submucosal dissection of the esophagus (CESD) was performed in each pig. Group 1 (n = 11) only underwent CESD and Group 2 (n = 10) had repeated Hemospray applications after CESD. Clinical, endoscopic, and radiological monitoring were performed, blood levels of four inflammatory or pro-fibrotic cytokines were assessed, and histological analysis was performed. Median esophageal diameter was greater in the group treated with Hemospray (2 mm [1-3] vs. 3 mm [2-4], P = 0.01), and the rate of symptomatic esophageal stricture was 100% and 60% in Groups 1 and 2, respectively (P = 0.09). The thicknesses of esophageal fibrosis and inflammatory cell infiltrate were significantly lower in Group 2 than in Group 1 (P = 0.002 and 0.0003, respectively). The length of the neoepithelium was greater in Group 2 than in Group 1 (P = 0.0004). Transforming growth factor-β levels were significantly lower in Group 2 than in Group 1 (P = 0.01). The application of Hemospray after esophageal CESD reduces scar tissue formation and promotes reepithelialization, and therefore is a promising therapeutic approach in the prevention of post-endoscopic esophageal stricture.

Age-related changes of platelet and plasma coagulation parameters in young pigs

The literature on hemostatic processes in swine is sparse and often fragmentary; hence, we conducted our study to characterize age-related changes in selected parameters of primary and secondary hemostasis in 50 growing pigs between day 2 and week 24 of age. We measured platelet count (PLT), mean platelet volume, platelet-to-large cell ratio, prothrombin time, activated partial thromboplastin time (aPTT), thrombin time (TT), and fibrinogen concentration. Among primary hemostasis parameters, PLT underwent the largest fluctuation with the animals’ age, ranging from 340 to 730 × 109/L. However, statistical significance was only detected for 4-week-old piglets compared to 18-week-old animals. Of the secondary hemostasis parameters measured, TT and aPTT were the most changeable. Activated partial thromboplastin time displayed a characteristic biphasic course, being relatively short before week 5 of age (17.8–19.9 s) and then becoming much longer (28.7–52.5 s). The aPTTs measured in animals 6 weeks of age and older were statistically different ( p < 0.01) from those in younger piglets. The 2 main components of hemostasis, platelet hemostasis and plasma coagulation, did not develop at the same time. It took much longer for secondary hemostasis to stabilize, whereas platelet parameters were stable early in life.

Myocardial infarction and functional outcome assessment in pigs

Introduction of newly discovered cardiovascular therapeutics into first-in-man trials depends on a strictly regulated ethical and legal roadmap. One important prerequisite is a good understanding of all safety and efficacy aspects obtained in a large animal model that validly reflect the human scenario of myocardial infarction (MI). Pigs are widely used in this regard since their cardiac size, hemodynamics, and coronary anatomy are close to that of humans. Here, we present an effective protocol for using the porcine MI model using a closed-chest coronary balloon occlusion of the left anterior descending artery (LAD), followed by reperfusion. This approach is based on 90 min of myocardial ischemia, inducing large left ventricle infarction of the anterior, septal and inferoseptal walls. Furthermore, we present protocols for various measures of outcome that provide a wide range of information on the heart, such as cardiac systolic and diastolic function, hemodynamics, coronary flow velocity, microvascular resistance, and infarct size. This protocol can be easily tailored to meet study specific requirements for the validation of novel cardioregenerative biologics at different stages (i.e. directly after the acute ischemic insult, in the subacute setting or even in the chronic MI once scar formation has been completed). This model therefore provides a useful translational tool to study MI, subsequent adverse remodeling, and the potential of novel cardioregenerative agents.

Treatment with OPN-305, a humanized anti-Toll-Like receptor-2 antibody, reduces myocardial ischemia/reperfusion injury in pigs

BACKGROUND

Toll-like receptor (TLR)-2 is an important mediator of innate immunity and ischemia/reperfusion-induced cardiac injury. We have previously shown that TLR2 inhibition reduces infarct size and improves cardiac function in mice. However, the therapeutic efficacy of a clinical grade humanized anti-TLR2 antibody, OPN-305, in a large-animal model remained to be addressed.

METHODS AND RESULTS

Pigs (n=38) underwent 75 minutes ischemia followed by 24 hours of reperfusion. Saline or OPN-305 (12.5, 6.25, or 1.56 mg/kg) was infused intravenously 15 minutes before reperfusion. Cardiac function and geometry were assessed by echocardiography. Infarct size was calculated as the percentage of the area at risk and by serum Troponin-I levels. Flow cytometry analysis revealed specific binding of OPN-305 to porcine TLR2. In vivo, OPN-305 exhibited a secondary half-life of 8±2 days. Intravenous administration of OPN-305 before reperfusion significantly reduced infarct size (45% reduction, P=0.041) in a dose-dependent manner. In addition, pigs treated with OPN-305 exhibited a significant preservation of systolic performance in a dose-dependent fashion, whereas saline treatment completely diminished the contractile performance of the ischemic/reperfused myocardium.

CONCLUSIONS

OPN-305 significantly reduces infarct size and preserves cardiac function in pigs after ischemia/reperfusion injury. Hence, OPN-305 is a promising adjunctive therapeutic for patients with acute myocardial infarction.

Lack of inhibitory effect of acetylsalicylic acid and meloxicam on whole blood platelet aggregation in cats

OBJECTIVE

To determine the effects of acetylsalicylic acid (ASA) and meloxicam on feline platelet aggregation and associated platelet thromboxane production and serotonin release.

DESIGN

Prospective interventional study.

SETTING

University research facility.

ANIMALS

Eight healthy male castrated domestic short hair cats from a research colony.

INTERVENTIONS

Oral medications were administered to 8 cats for 14 days in a randomized, placebo-controlled, crossover design. Treatment groups included: aspirin (ASA) (5 mg/kg q 48 h), meloxicam (0.05 mg/kg q 24 h), and placebo (0.5 mL of water q 24 h). Thromboxane assays (TXB(2) ) and whole blood (impedance) aggregometry (WBA) were performed on samples collected before drug administration, and on days 7, 15, and 17, using adenosine diphosphate (ADP; 10 μM) and collagen (5 μg/mL) as agonists for WBA. Serotonin release was assayed on postaggregation plasma. Oral mucosal bleeding time (OMBT) and complete blood cell counts were measured on days 0 and 15.

MEASUREMENTS AND MAIN RESULTS

Neither medication affected WBA at any time point. OMBT decreased in the ASA group relative to baseline. No differences were detected in WBA and OMBT baseline between any groups. No difference was detected in serotonin secretion at any time point. TXB(2) was significantly decreased in the ASA group at all times after initiation of treatment but no change was noted in the meloxicam or placebo groups.

CONCLUSIONS

At the doses studied, neither meloxicam nor ASA had an inhibitory effect on WBA or OMBT in cats. Thromboxane concentrations were significantly decreased with ASA treatment.

Initial resuscitation with plasma and other blood components reduced bleeding compared to hetastarch in anesthetized swine with uncontrolled splenic hemorrhage

BACKGROUND

Damage control resuscitation recommends use of more plasma and less crystalloid as initial resuscitation in treating hemorrhage. The purpose of this study was to evaluate resuscitation with either blood components or conventional fluids on coagulation and blood loss.

STUDY DESIGN AND METHODS

Isofluorane-anesthetized, instrumented pigs (eight per group) underwent controlled hemorrhage of 24 mL/kg, 20-minute shock period, splenic injury with 15-minute initial bleeding, and hypotensive fluid resuscitation. Lactated Ringer's (LR) was infused at 45 mL/kg while hetastarch (high-molecular-weight hydroxyethyl starch 6%, Hextend, Hospira, Inc., Lake Forest, IL) and blood component (fresh-frozen plasma [FFP], 1:1 FFP:[red blood cells] RBCs, 1:4 FFP : RBCs, and fresh whole blood [FWB]) were infused at 15 mL/kg. Postresuscitation blood loss (PRBL), hemodynamics, coagulation, hematocrit, and oxygen metabolism were measured postinjury for 5 hours.

RESULTS

Resuscitation with any blood component reduced PRBL of 52% to 70% compared to Hextend, with FFP resulting in the lowest PRBL. PRBL with LR (11.5 ± 3.0 mL/kg) was not significantly different from Hextend (17.9 ± 2.5 mL/kg) or blood components (range, 5.5 ± 1.5 to 8.6 ± 2.6 mL/kg). The volume expansion effect of LR was transient. All fluids produced similar changes in hemodynamics, oxygen delivery, and demand despite the oxygen-carrying capacity of RBC-containing fluids. Compared with other fluids, Hextend produced greater hemodilution and reduced coagulation measures, which could be caused by an indirect dilutional effect or a direct hypocoagulable effect.

CONCLUSIONS

These data suggest that blood products as initial resuscitation fluids reduced PRBL from a noncompressible injury compared to Hextend, preserved coagulation, and provided sustained volume expansion. There were no differences on PRBL among RBCs-to-FFP, FWB, or FFP in this nonmassive transfusion model.

A study of platelets in the armadillochaetophractus villosus(xenarthra, dasypodidae)

Nothing is known about haemostasis in Xenarthra, a widely distributed Order of American mammalians. Chaetophractus villosus, a member of the Dasypodidae family of this group, which is easily adapted to captivity, is of growing interest for biomedical research. In this work, we studied platelet number, MPV, ultrastructure of the platelets by SEM and TEM, and aggregation responses to ADP and ristocetin in this species. Blood samples were obtained by cardiac puncture in 20 anaesthetised animals. Platelet count and MPV were evaluated at the beginning and at the end of a 3-year experimental period, to detect possible variations related to time of captivity. SEM and TEM were done by routine methods adapted to the material, and aggregation response to ADP and ristocetin were evaluated by the Born method. The parameters studied did not show any sex-related differences, nor did the platelet count change during captivity. Nevertheless, MPV decreased during this period. Platelets were ultrastructurally similar to those of other mammals and human beings and responded to proven agonists. Data provided in this study will contribute to the understanding of the haemostatic process in this species.

Use of concentrated human albumin with argon-beam coagulation in laparoscopic partial nephrectomy

PURPOSE

Laparoscopic partial nephrectomy (LPN) remains a technically challenging procedure mainly because of the lack of reliable methods of hemostasis. We evaluated the feasibility of using concentrated human albumin with argon-beam coagulation to control hemorrhaging and urinary leakage during LPN.

MATERIALS AND METHODS

Six domestic swine underwent heparinization, then lower-pole LPN after renal-hilar vascular control had been obtained. The animals received argon-beam coagulation either alone (control) or with 38% albumin. Three days later, an identical procedure was performed on the contralateral kidney. Retrograde pyelography was employed to assess for urine leakage. The animals were then euthanized, and both kidneys were harvested for histologic examination.

RESULTS

The mean operative and warm-ischemia times were similar in the two groups and were 27 and 15 minutes, respectively, using albumin with argon-beam coagulation and 25 and 16 minutes with argon coagulation alone. The albumin group required shorter coagulation times (187 v 312 seconds; P = 0.04), which resulted in less thermal injury. By retrograde pyelography, two kidneys (33%) in the albumin group and all six in the control group had urine leakage.

CONCLUSIONS

Adding concentrated albumin to argon-beam coagulation substantially increases the reliability and durability of parenchymal repair after LPN. The time needed to achieve stable hemostasis and closure of the collecting system was reduced compared with standard argon-beam coagulation.

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

BACKGROUND

Thoracoscopy has been shown to reduce the inflammatory and immunologic response to surgical stress, as compared with corresponding open procedures in humans. The influence on the hemostatic system, however, has not been thoroughly evaluated. The current study aimed to compare the perioperative and immediate postoperative changes in cellular, hemostatic, and inflammatory parameters after a partial pericardectomy performed by either thoracoscopy or thoracotomy.

METHODS

For this study, 16 pigs were randomly assigned to have a partial pericardectomy performed thoracoscopically or by thoracotomy. Blood was collected intraoperatively, then 10 min, 3 h, and 6 h after surgery. Whole ethylenediaminetetraacetic acid (EDTA)-stabilized blood and plasma were examined for cellular, hemostatic, and inflammatory parameters, respectively, and thromboelastography (TEG) was performed on citrated whole blood.

RESULTS

No significant difference in any of the parameters measured was found between the two groups except for the TEG parameter R-time, which was significantly shorter in the thoracoscopic group 3 h postoperatively. In both groups, a significant postoperative state of hypercoagulability and increase in inflammatory parameters was found. Additionally, pig blood showed a high degree of hypercoagulability in preoperative measurements, as compared with other species.

CONCLUSIONS

Partial pericardectomy performed by thoracotomy or thoracoscopy in pigs produces a surgical stress response of equal magnitude, as measured by cellular, hemostatic, and inflammatory changes.

Normal values for thrombelastography (ROTEM) and selected coagulation parameters in porcine blood

The pig is a suitable animal model for researching blood coagulation and fibrinolysis. The present study therefore aimed to investigate in porcine blood the applicability of commercially available tests of coagulation and thrombelastography (ROTEM) and above all to determine normal values for coagulation parameters (e.g. prothrombin time (PT), activated partial thromboplastin time (aPTT), thrombin-antithrombin complexes (TAT), fibrinogen, antithrombin III (AT III), D-dimers, protein C). Except for the FibTEM and aPTT tests, all commercially available coagulation tests used were fully applicable for porcine blood. Normal values and reference intervals for porcine blood are given. As compared to the human reference intervals for the coagulation parameters investigated, porcine blood was found to be hypercoagulable.

Activation of fibrinolytic pathways is associated with duration of supraceliac aortic cross-clamping

PURPOSE

The cause of the coagulopathy seen with supraceliac aortic cross-clamping (SC AXC) is unclear. SC AXC for 30 minutes results in both clotting factor consumption and activation of fibrinolytic pathways. This study was undertaken to define the hemostatic alterations that occur with longer intervals of SC AXC.

METHODS

Seven pigs underwent SC AXC for 60 minutes. Five pigs that underwent infrarenal aortic cross-clamping (IR AXC) for 60 minutes and 11 pigs that underwent SC AXC for 30 minutes served as controls. No heparin was used. Blood samples were drawn at baseline, 5 minutes before release of the aortic clamp, and 5, 30, and 60 minutes after unclamping. Prothrombin time, partial thromboplastin time, platelet count, and fibrinogen concentration were measured as basic tests of hemostatic function. Thrombin-antithrombin complexes were used to detect the presence of intravascular thrombosis. Fibrinolytic pathway activation was assessed with levels of tissue plasminogen activator antigen and tissue plasminogen activator activity, plasminogen activator inhibitor-1 activity, and alpha2-antiplasmin activity. Statistical analysis was performed with the Student t test and repeated measures of analysis of variance.

RESULTS

Prothrombin time, partial thromboplastin time, and platelet count did not differ between groups at any time. Fibrinogen concentration decreased 5 minutes (P =.005) and 30 minutes (P =.006) after unclamping in both SC AXC groups, but did not change in the IR AXC group. Thrombin-antithrombin complexes increased in both SC AXC groups, but were not significantly greater than in the IR AXC group. SC AXC for both 30 and 60 minutes produced a significant increase in tissue plasminogen activator antigen during clamping and 5 minutes after clamping. This increase persisted for 30 and 60 minutes after clamp release in the 60-minute SC AXC group. Tissue plasminogen activator activity, however, increased only in the 60-min SC AXC group during clamping (P =.02), and 5 minutes (P =.05) and 30 minutes (P =.06) after unclamping, compared with both control groups.

CONCLUSIONS

Thirty and 60 minutes of SC AXC results in similar degrees of intravascular thrombosis and fibrinogen depletion. Although SC AXC for both 30 and 60 minutes leads to activation of fibrinolytic pathways, only 60 minutes of SC AXC actually induces a fibrinolytic state. Fibrinolysis appears to be an important component of the coagulopathy associated with SC AXC, and is related to the duration of aortic clamping.

CLINICAL RELEVANCE

The coagulopathy frequently associated with thoracoabdominal aortic aneurysm repair is thought to revolt visceral ischemia-reperfusion. The nature of this coagulopathy is controversial. The current study demonstrates that the major hemostatic alteration associated with supraceliac aortic cross-clamping is activation of fibrinolytic pathways. The magnitude of this fibrinolytic response is directly related to the duration of supraceliac aortic occlusion. Future efforts to treat this coagulopathy may well include judicious use of autofibrinolytic agents.

Activity of a synthetic hexadecasaccharide (SanOrg123781A) in a pig model of arterial thrombosis

The activity of SanOrg123781A, a new synthetic antithrombotic drug inhibiting both factor Xa and thrombin through antithrombin (AT), was compared to that of unfractionated heparin (UFH) and of the synthetic pentasaccharide (fondaparinux, SP) in an ex vivo arterial thrombosis model in the pig. Six groups of four pigs were administered intravenously with SanOrg123781A (1, 3, 10 and 30 nmol kg(-1)), UFH (30 nmol kg(-1)) or SP (30 nmol kg(-1)). In this arterial model in which platelet thrombus was formed on a thrombogenic surface under a constant high shear rate, UFH and SP had moderate antithrombotic effects while SanOrg123781A exhibited a strong, dose-dependent inhibitory activity on platelet adhesion and platelet thrombus formation. In contrast to UFH, SanOrg123781A did not modify the activated partial thromboplastin time (aPTT) even at 30 nmol kg(-1), but strongly inhibited thrombin generation. At the same dose, despite a lower antithrombotic activity than SanOrg123781A, UFH significantly affected all the coagulation parameters. Taken together, these results show that SanOrg123781A, due to its potent and selective antifactor Xa and antifactor IIa activities is a promising new antithrombotic agent even in arterial setting.

Clopidogrel-induced qualitative changes in thrombus formation correlate with stent patency in injured pig cervical arteries

Thienopyridines (ticlopidine or clopidogrel) alone or in combination with aspirin are now the reference antiplatelet therapy after stent implantation. To better understand the high efficacy and low risk of bleeding with these agents, we tested clopidogrel alone or with aspirin in an acute ex vivo flow chamber model and in a subacute in vivo arterial thrombosis model. Clopidogrel induced a dose-dependent increase in bleeding time (BT), inhibited ADP-induced platelet aggregation and in the flow chamber reduced thrombus size, and changed thrombus structure to broad-based structure composed of nondegranulated loosely attached platelets contrasting with the tight clumps of degranulated platelets seen without clopidogrel. The in vivo model involved angioplasty and stenting at the site of a preinduced arterial lesion and thrombosis in pig carotid arteries. Clopidogrel alone or with aspirin (but not aspirin alone) decreased the number of stented vessels occluded for more than 24 h and conversely reduced the number of occluding thrombus. At 96 h after stenting, 100% and 90% of the arteries were patent with clopidogrel/aspirin and clopidogrel alone, respectively (vs. 67% and 44% with aspirin and saline, respectively). Clopidogrel destabilizes thrombus without complete abolishment of platelet reactivity.

Activation of blood coagulation in pigs following lower limb gunshot trauma

A standardized, quantifiable gunshot trauma to one hind leg of fourteen anaesthetized and sedated pigs was used to investigate the extent to which an isolated gunshot trauma causes activation of blood coagulation. The traumatized pigs were mechanically ventilated in intensive care for 48 h before they were euthanized. Blood samples were drawn at baseline (t = 0), 24, 27 and 48 h after trauma to examine the late effects on haemostasis. The median energy absorption in the pigs was 27.57 (22.6-31.7) J/kg. This gunshot injury caused increased creatine kinase and body temperature and led to a combined metabolic and respiratory alkalosis; the pigs remained circulatory stable. Within the haemostatic system the trauma caused increased activated partial thromboplastin time at 48 h (P < 0.05), prothrombin time at 24 and 27 h (P < 0.05), fibrinogen and soluble fibrin concentration at 48 h (P < 0.05), and 24 h (P < 0.05), respectively. The platelet count, protein C activity, tissue factor concentration and trombin-antithrombin concentration decreased throughout the experiment (P < 0.05); the changes of antithrombin activity did not reach statistical significance. In conclusion, this study in pigs demonstrates that a standardized gunshot trauma to a hind leg activates blood coagulation without signs of organ failure or disseminated intravascular coagulation within 48 h.

Functional metabolic characteristics of intact pig livers during prolonged extracorporeal perfusion: potential for a unique biological liver-assist device

BACKGROUND

The clinical development of liver-support devices based on perfusion of either pig hepatocytes cartridges or whole pig livers has been hampered by the ability to use sufficient liver cell mass to provide adequate metabolic support, limited perfusion times, and the potential for patient exposure to pig zoonotic diseases.

METHODS

We designed an original system in which an isolated intact pig liver was perfused extracorporeally under physiological conditions in a closed loop circuit with allogeneic pig blood and constant monitoring of major physiological and functional parameters. The perfusion circuit further included an interface membrane to provide for separation of patient and liver perfusion circulation.

RESULTS

Prolonged (6-21 hr) liver perfusion did not produce significant liver damage as reflected by modest rises in the levels of the serum transaminases, stability of main biochemical parameters (including potassium), and the maintenance of normal cellular morphology. Optimal liver function was documented as measured by lactate consumption, control of glycemia, and the results of clotting studies and functional assays. The perfused liver cleared 82% and 79% of peak bilirubin and ammonia concentrations with clearing kinetics identical throughout perfusion. Indocyanine green clearance was identical to that observed in the living donor before explant surgery.

CONCLUSIONS

In conclusion, the extracorporeal pig liver perfusion apparatus described here allows optimal pig liver function for prolonged periods of time. The microporous membrane to provide separation of donor organ and recipient and the high level of functional activity suggest that this form of liver metabolic support may have important clinical applications.

Analysis of Coagulation Changes Associated with Supraceliac Aortic Crossclamping Using Thromboelastography

INTRODUCTION

The etiology of the coagulation changes seen with supraceliac (SC) aortic crossclamping (AXC) remains controversial; both primary fibrinolysis and clotting factor consumption have been implicated. The cause of these changes was investigated with thromboelastography (TEG), a test that measures the viscoelastic properties of thrombus to dynamically assess coagulation and fibrinolysis.

METHODS

Eight pigs underwent SC AXC for 30 min; 5 pigs undergoing 30 min of infrarenal (IR) aortic clamping served as controls. Blood was drawn before AXC, before unclamping, and 5 and 60 min after unclamping. Thromboelastography and standard coagulation tests [prothrombin time (PT), partial thromboplastin time (PTT), fibrinogen, and platelet count] were performed. Measured TEG parameters included fibrinolytic index (a measure of fibrinolysis), r value (a reflection of intrinsic coagulation cascade activity), and the alpha angle and K values (measures of the speed of solid clot formation). Repeated measures ANOVA and t test were used for statistical analysis.

RESULTS

There was no difference in the fibrinolytic index at any time point between the two groups. Increased activity of the intrinsic coagulation cascade during SC clamping was reflected by a lower R value just before unclamping (12.6 +/- 3.0 vs 20.0 +/- 3.0, P = 0.048) compared to IR AXC. Decreased speed of solid clot formation was noted 5 min after unclamping in the SC group but not the IR group [as defined by an increased K value (ANOVA, P = 0.010) and a decreased alpha angle value (ANOVA, P = 0.005)]. Fibrinogen levels were lower in the SC than in the IR group 5 (P = 0.013) and 60 min after unclamping (P = 0.02), but PT, PTT, and platelets did not differ between the groups at any time points.

CONCLUSIONS

Thirty minutes of SC AXC does not result in fibrinolysis. There is increased clotting activity during SC clamping followed by decreased speed of clot formation and decreased fibrinogen levels after unclamping. These changes are consistent with clotting factor consumption.

Coagulation assessment in healthy pigs undergoing single xenon anaesthesia and combinations with isoflurane and sevoflurane

BACKGROUND

With the introduction of new anaesthetics into clinical practice possible side effects of these novel anaesthetics have to be evaluated. This study was performed to clarify whether xenon or combinations of xenon with isoflurane or sevoflurane modify blood coagulation.

METHODS

The study was performed in 20 healthy pigs which first underwent xenon anaesthesia (65 Vol%) and were then randomly assigned to combinations of xenon and isoflurane or sevoflurane at varying concentrations. During anaesthesia the following parameters were controlled: aPTT, PT, fibrinogen concentrations and thrombelastographic measurements.

RESULTS

Xenon monoanaesthesia did not alter significantly any coagulation parameter. When isoflurane was introduced the aPTT showed a significant increase while fibrinogen concentration decreased. The introduction of sevoflurane led also to a decrease in fibrinogen concentration, while the aPTT was unchanged. These decreases in fibrinogen concentration were not accompanied by reduced maximal clot strength or elevated fibrinolysis evaluated by thrombelastography. Although the above-described changes were statistically significant, none of the parameters throughout the experiment exceeded the limits of normal values.

CONCLUSION

In our study, xenon monoanaesthesia and combinations of xenon with isoflurane and sevoflurane did not lead to pathologic alterations in the measured coagulation parameters.

A high-fat meal does not activate blood coagulation factor VII in minipigs

It is a matter of debate whether postprandial activation of blood coagulation factor VII (FVII) is associated with an increased risk of thrombosis. To clarify this question, an animal model in which consequences of dietary FVII activation can be studied in a more detailed way would be an important tool. We studied postprandial FVII activation in seven non-fasting Göttingen minipigs. Intralipid (4 g/kg) was administered through a gastric tube in two fractions at 9.00 a.m. (one-third of total dose) and 10.30 a.m. (two-thirds of total dose). Blood samples were drawn 0.5 h before (baseline) and 2, 3, 3.5, 4, 5, and 6 h after the first fat load. Triglycerides, activated FVII (FVIIa), FVII coagulant activity (FVIIc), FVII amidolytic activity (FVIIam) and prothrombin fragment I + 2 (F1 + 2) were analysed in plasma samples. Median plasma triglycerides were significantly raised from 0.67 mmol/l (baseline) to 2.56 mmol/l 5 h postprandially (P < 0.001). There were no significant changes in FVIIa (9.6 U/l at baseline), FVIIam (142% at baseline) and F1 + 2 (0.13 nmol/l at baseline). FVIIc decreased from 141% at baseline to 114% 6 h postprandially (P < 0.001). As a high-fat meal does not seem to activate blood coagulation FVII in minipigs, the pig is apparently not a relevant model for the study of dietary FVII activation and thrombin generation.

The calcium inhibitor SR33805 reduces intimal formation following injury of the porcine carotid artery

We studied the effect of SR33805, a calcium channel blocker, in vitro on the proliferation of vascular smooth muscle cells (SMC) stimulated by foetal calf serum, basic fibroblast growth factor and platelet derived growth factor, and in vivo with regard to SMC migration and proliferation which occurred following injury of the porcine carotid artery. The intimal lesion was induced by a silasten collar surgically positioned around the carotid artery and by a stenosis reducing blood flow by 50% for 30 days. Animals received SR33805 (5 mg/kg/day) 8 days before the induction of the lesion and up to 30 days after. In vitro, SR33805 inhibited in a dose-dependent manner growth factor-induced proliferation of SMC (0.20<IC(50)<0.46 microM). In vivo, SR33805 reduced the intima/media ratio of the cross sectional surface area (decrease of 60%, P<0.05) without affecting neointimal SMC density. The medial SMC density was 40% lower in treated than in control animals (upstream, P<0.05 and downstream to the stenosis, P<0.01). Thus, it appears that SR33805 significantly reduced intimal hyperplasia, which occurred after perivascular manipulation of the artery, an effect consistent with its in vitro proliferation inhibitory activity, suggesting that long-term treatment with SR33805 may reduce or delay SMC proliferation.

Fibrinolytic response to retinal detachment surgery under general or local anesthesia

PURPOSE

To evaluate perioperative changes in fibrinolysis in patients undergoing retinal detachment surgery under general or local anesthesia.

PATIENTS

Prospective study of 81 patients (43 male, 38 female), aged from 15 to 82 (mean 50.7 SD = 17.8) years, undergoing retinal detachment surgery (encirclement with scleral buckling) under general anesthesia (group A), and 14 patients (6 male, 8 female) aged from 15 to 78 (mean 52.9, SD =19.8) years, operated under local anesthesia (group B). Excluded were patients with venous or arterial disease or other factors that could change the parameters investigated.

METHODS

Blood was sampled from a cubital vein one day before surgery, immediately after induction of anesthesia but before surgery, immediately after completion of the operation but before the termination of anesthesia and after the operation (on days 1 and 4). In patients' citrated plasma, tissue plasminogen activator antigen (t-PA-Ag), plasminogen activator inhibitor type 1 antigen (PAI-1 Ag) and activity (PAI-1), fibrin-fibrinogen degradation products (FDP) and euglobulin lysis time (ELT) were measured. RESULTS. The pattern of changes in perioperative fibrinolytic activity was similar in both groups. Intraoperative levels of FDP were significantly higher and ELT shorter than preoperatively. In both groups t-PA Ag concentration was significantly increased on the first postoperative day. There were no changes in PAI-1 in both groups. Postoperatively, the FDP concentration was reduced and ELT prolonged.

CONCLUSIONS

Retinal detachment surgery induces intraoperative activation of fibrinolysis in the systemic circulation regardless of the type of anesthesia.

Alterations in antithrombin III activity and other blood coagulation parameters after retinal detachment surgery

PURPOSE

To evaluate perioperative changes in blood coagulation in patients undergoing retinal detachment surgery.

MATERIALS

Prospective study of 56 patients, aged from 19 to 82 (mean +/- S.D. 53 +/- 16.8) years, undergoing retinal detachment surgery (encirclement with scleral buckling) under general anesthesia. Excluded were patients with venous or arterial disease and any other factors that could affect the parameters under consideration.

METHODS

Blood was sampled from the cubital vein one day before surgery, immediately after induction of anesthesia but before surgery, immediately after completion of the operation but before the termination of anesthesia and on days 1 and 4 after the operation. We measured antithrombin III activity (AT III), platelet count, fibrinogen concentration, activated partial thromboplastin time (aPTT) and prothrombin time (PT).

RESULTS

Intraoperative AT III activity and platelet count were significantly lower, aPTT was shortened and PT prolonged, although all values remained within the normal range. These results indicate moderate activation of coagulation during retinal detachment surgery. On the first postoperative day coagulation activity was reduced, with increases in AT III activity, fibrinogen concentration and platelet count and prolongation of aPTT.

CONCLUSIONS

During retinal detachment surgery there is moderate activation of coagulation in the systemic circulation.

Administration of autologous fetal membranes: Effects on the coagulation in pregnant mini-pigs

OBJECTIVE: A hallmark of the so-called amniotic fluid embolism is the induction of coagulation defects. Entry of meconium-free autologous amniotic fluid into the circulation, however, is innocuous. Little is known about the true causative agent or agents. The purpose of this study was to assess the effects of homogenized autologous fetal membranes (FM) on the coagulation system in the mini-pig model. DESIGN: Laboratory study. SETTING: University institute animal laboratory. SUBJECTS: Six near-term pregnant, Göttingen-bred mini-pigs. INTERVENTIONS: After induction of general anesthesia, FM were col-lected from all animals by cesarean section. Animals received 2 g FM (shredded and suspended in lactated Ringer's solution) via an ear vein. MEASUREMENTS: Blood samples were taken from a central vein before administration (baseline), immediately after administration, every 10 mins until 90 mins after administration, and every 20 mins until 150 mins after administration. The following parameters were measured: platelets, partial thromboplastin time, prothrombin time index, fibrinogen, factors II, V, VII, VIII, IX, X, XI, antithrombin III, and protein C. The values relative to baseline in the FM group were compared with a historical control group by rank order test. A p <.05 was considered significant. MAIN RESULTS: In the FM group (compared with the control group), platelets were lower; partial thromboplastin time was prolonged; fibrinogen was lower; prothrombin time index was lower (ie, prothrombin time was prolonged); protein C and antithrombin III were lower; and activity levels of factors V and VII were lower. The levels of factors II, VIII, IX, X, and XI showed a trend toward lower activity in the FM group, but the differences were not statistically significant. CONCLUSIONS: FM can activate coagulation in mini-pigs. The laboratory parameter changes seen are typical for disseminated intravascular coagulation. However, the full clinical picture of amniotic fluid embolism and disseminated intravascular coagulation could not be elicited despite the high dose of FM used.

Animal models for studies on cold-induced platelet activation in human beings

When human platelets are chilled below about 20 degrees C, they spontaneously activate, a phenomenon that limits their storage lifetime. We have previously shown that this activation in chilled human platelets is associated with passage through a lipid phase transition. Because animal models are necessary for Investigating methods for cold storage of platelets, it is essential to determine whether such phase transitions and chilling-induced activation are found in these models. In this study we examined platelets from some commonly used animal models-pigs, rhesus monkeys, mice, dogs, and rabbits. Using Fourier transform infrared spectroscopy (FTIR), we detected the thermotropic membrane phase transition in Intact platelets and assessed the morphologic response of the platelets to chilling. Statistical analysis of both FTIR and shape change show that of the animal models tested, pig platelets are most similar to human platelets. These studies suggest that pigs and pig platelets are the models of choice for the study of cold-induced platelet activation in human beings.

In vivo regulation of von willebrand factor synthesis: von Willebrand factor production in endothelial cells after lung transplantation between normal pigs and von Willebrand factor-deficient pigs

To evaluate the regulation of plasma von Willebrand factor (vWF) and its in situ production by endothelial cells (ECs), 12 swine leukocyte antigen (SLA)-compatible left lung transplantations were performed. Normal lungs were transplanted into 10 pigs homozygous for von Willebrand disease and into 2 normal pigs. Additionally, 1 normal pig underwent pneumonectomy, and 1 SLA-incompatible lung transplantation between normal pigs was performed. None of the transplanted animals received immunosuppressive therapy. Plasma vWF level was evaluated by ELISA and multimeric pattern. EC vWF content was assessed by immunohistochemistry. Global hemostasis was assessed by standardized ear bleeding time. Six of 12 SLA-compatible lung transplantations and the incompatible transplantation were successful and were used for the study. The functions and the viability of ECs, reflected by their ability to produce vWF and normal multimeric plasma vWF pattern, were preserved in SLA-compatible and -incompatible lung transplantations. vWF production was preserved in ECs that initially synthesized it. EC constitutive and storage pathways are modulated differently according to transplantation compatibility and severity of rejection. In SLA-compatible lung transplantations without histological evidence of rejection, the production of vWF was preserved, whereas constitutive vWF secretion appeared to be altered in cases with minor histological signs of rejection. In pigs with von Willebrand disease that were transplanted with normal lungs without sign of rejection, plasma vWF was significantly increased in an amount expected from the estimated production of a normal lung. In the transplanted normal lung, there was no vWF overexpression by the ECs and no recruitment of ECs that initially did not express vWF. In SLA-incompatible transplantation, ECs were morphologically normal with increased and blurred vWF labeling, whereas plasma vWF levels remained normal, reflecting that EC activation is associated with an increased vWF production with probable diversion to storage pathway. This model depicts the changes of EC regulation of vWF secretion in pig lung transplants. However, this model cannot be directly extrapolated to human organ transplantation because animals did not receive any immunosuppressive therapy, which may be toxic to ECs.

Meconium and amniotic fluid embolism: effects on coagulation in pregnant mini-pigs

OBJECTIVE

A hallmark of amniotic fluid embolism is the induction of coagulation defects. Little is known about the nature of these defects or the causative agent or agents. The purpose of this study was to assess the effects of meconium containing (native) meconium-amniotic-fluid infusion (MAFI) and meconium-free (centrifuged) amniotic-fluid infusion (AFI) on the coagulation system in the mini-pig model.

DESIGN

Laboratory study.

SETTING

University institute animal laboratory.

SUBJECTS

Near-term pregnant Göttingen bred mini-pigs in three groups (control, MAFI, AFI) of six animals each.

INTERVENTIONS

After induction of anesthesia, amniotic fluid was collected by cesarean section in all animals. Depending on the group, animals received either Ringer's solution (control), native amniotic fluid (MAFI), or centrifuged amniotic fluid (AFI) via an ear vein.

MEASUREMENTS AND MAIN RESULTS

Blood samples were taken from a central vein before infusion (baseline), immediately after infusion, every 10 mins until 90 mins after infusion, and finally, every 20 mins until 150 mins after infusion. The following parameters were measured: Platelets, partial thromboplastin time, prothrombin time, fibrinogen, factors V, VII, VIII, antithrombin III, and protein C. The values relative to baseline in the MAFI and AFI groups were compared with control by rank order test. A p<.05 was considered statistically significant. Compared with the control group, platelets were lower in the MAFI group (p<.005), PTT was prolonged in both the MAFI and AFI groups (p<.005), fibrinogen was lower in both the MAFI and AFI groups (p<.05), prothrombin index was lower (i.e., prothrombin time was prolonged) in the MAFI group (p<.05), and protein C was lower in the MAFI group (p<.005).

CONCLUSIONS

Both MAFI and, to a much lesser extent, AFI cause an activation of coagulation in mini-pigs. The changes induced by meconium-free AFI are probably not sufficient to explain the high mortality of the condition.

Animal experimental implantation of an atrial septal defect occluder system

OBJECTIVE

To establish the implantation technique for the atrial septal defect occluder system (ASDOS) device in an experimental animal model and to determine long term mechanical stability of the device and its in vivo properties in terms of biocompatibility and tissue reaction.

MATERIALS AND METHODS

An atrial septal defect was created and the device implanted in 17 pigs (mean weight 30 kg). The implantation technique was refined and modified because of initial technical and anatomical complications during nine acute pilot studies. The technique proved to be feasible in eight subsequent survival studies. Four pigs were electively killed three months after implantation (group 1). The remaining four pigs were killed six months after implantation (group 2).

RESULTS

Necropsy showed all devices were embedded in soft tissue three months after implantation. Microscopic examination of atrial septal tissue showed an acute granulomatous inflammatory reaction in group 1 and fibrosis in group 2. The intensity of the inflammatory reaction around the device was clearly milder in group 2, indicating a decline in the inflammatory response with time. Clinical and biochemical investigations indicated acceptable biocompatibility of the device.

CONCLUSION

The implantation technique for the ASDOS device in a chronic pig model has been established. Biocompatibility of the device was acceptable.