Experimental model of portal hypertension and esophagogastric varices in minipigs: pressure and endoscopic pilot study

Introduction: Portal hypertension still represents an important health problem worldwide. In the search for knowledge regarding this syndrome, experimental studies with animal models have proven to be useful to point the direction to be taken in future randomized clinical trials. Purpose: To validate the experimental model of portal hypertension and esophagogastric varices in a medium-sized animal. Methods: This study included five minipigs br1. Midline laparotomy with dissection of the portal vein and production of a calibrated stenosis of this vein was performed. Measurement of pressure in the portal venous and digestive endoscopic were performed before and five weeks after the production of a stenosis. Results: All animals were 8 months old, average weight of 17 ± 2.5 kg. The mean pressure of the portal vein immediately before the partial ligation of the portal vein was 8.9 + 1.6 mm Hg, with 26.6 + 5.4 mm Hg in the second measurement five weeks later (p < 0.05). No gastroesophageal varices or hypertensive portal gastropathy were seen at endoscopy procedures in our sample at any time in the study. Conclusion: Portal vein ligation in minipigs has been validated in the production of portal hypertension, but not in the formation of esophageal varices.

Using multidimensional scaling in model choice for congenital oesophageal atresia: similarity analysis of human autopsy organ weights with those from a comparative assessment of Aachen Minipig and Pietrain piglets.

Swine models had been popular in paediatric oesophageal surgery in the past. Although being largely replaced by rodent models, swine experienced a revival with the establishment of minipig models. However, none of them has ever been investigated for similarity to humans. We conducted a pilot study to determine whether three-week old Pietrain piglets and three-month old Aachen Minipigs are suitable for experimental paediatric oesophageal atresia surgery. We tested the operation's feasibility, performed a necropsy, weighed organs, measured organ length and calculated relative weights and lengths, and measured laboratory parameters. We used multidimensional scaling to assess the similarity of the swine breeds with previously published human data. Pietrain piglets had a higher a priori bodyweight than Aachen Minipigs (Δ = 1.31 kg, 95% confidence interval (CI): 0.37-2.23, p = 0.015), while snout-to-tail length was similar. Pietrain piglets had higher absolute and relative oesophageal lengths (Δ = 5.43 cm, 95% CI: 2.2-8.6; p = 0.0062, q1* = 0.0083 and Δ = 11.4%, 95% CI: 5.1-17.6; p = 0.0025, q3* = 0.0053). Likewise, absolute and relative small intestinal lengths were higher in Pietrains, but all other parameters did not differ, with the exception of minor differences in laboratory parameters. Multidimensional scaling revealed three-week old Pietrain piglets to be similar to two-month old humans based on their thoracoabdominal organ weights. This result indicates three-week old Pietrain piglets are a suitable model of paediatric oesophageal atresia surgery, because clinically many procedures are performed at around eight weeks age. Three-month old Aachen Minipigs were more dissimilar to eight-week old humans than three-week old Pietrain piglets.

Laparoscopic left hepatectomy in swine: a safe and feasible technique.

A purely laparoscopic four-port approach was created for left hepatectomy in pigs. A polyethylene loop was placed on the left two hepatic lobes for traction and lift. Next, penetrating ligation of the lobes using of a double row of silk sutures was performed to control bleeding. A direct hepatic transection was completed using a monopolar hook electrode without meticulous dissection of the left hepatic vein. The raw surface of the liver was coagulated and sealed with fibrin glue. Lobes were retrieved through an enlarged portal. Laparoscopic hepatic lobectomy was completed in all pigs without the use of specialized instruments and with a mean operative time of 179 ± 9 min. No significant perioperative complications were observed. The average weight of each resected lobe was 180 ± 51 g. Complete blood count as well as serum organics and enzyme levels normalized after about 2 weeks. During necropsy, adhesion of the hepatic raw surface to the gastric wall and omentum were observed. No other abnormalities were identified. This minimally invasive left hepatectomy technique in swine could serve as a useful model for investigating liver diseases and regeneration, and offer preclinical information to improve hepatobiliary surgical procedures.

Best practices for performing experimental surgery in swine.

The authors have extensive experience in surgery, anesthesia, and perioperative care in both miniature and domestic swine in the research setting. This manuscript describes the techniques that have been developed over the last four decades while developing porcine surgical models and their use in translational research. Swine are conditioned and socialized during a seven-day period prior to entering into a survival surgical protocol. Housing is designed to be nonstressful and accommodate the needs of the species. Induction of anesthesia is generally performed in the animal's pen. Injectable agents are administered sc in the neck using a butterfly catheter technique. The anesthetic protocol is designed to consider the physiologic effects of the agents and their potential effects on the research being performed. Complete aseptic technique is performed and includes final application of adhesive iodine impregnated drapes over the surgical site. Preemptive analgesia is performed using parenteral analgesics, local anesthetics, and/or epidural analgesics. Animals are monitored intensively intraoperatively and during the postoperative period with frequent recordings of physiologic parameters. Observation during the postoperative period is continuous until the animal fully recovers the righting reflex. Observations of the animals in the postoperative period are performed at least daily until surgical incisions are healed. In protocols which create defects or impede physiologic function daily monitoring may have to be performed in conjunction with specific therapies or tests throughout the duration of the protocol.

Laryngeal transplantation in minipigs: early immunological outcomes.

Despite recent tissue-engineering advances, there is no effective way of replacing all the functions of the larynx in those requiring laryngectomy. A recent clinical transplant was a success. Using quantitative immunofluorescence targeted at immunologically relevant molecules, we have studied the early (48 h and 1 week) immunological responses within larynxes transplantated between seven pairs of National Institutes of Health (NIH) minipigs fully homozygous at the major histocompatibility complex (MHC) locus. There were only small changes in expression of some molecules (relative to interindividual variation) and these were clearest in samples from the subglottic region, where the areas of co-expression of CD25(+) CD45RC(-) CD8(-) and of CD163(+) CD172(+) MHC-II(-) increased at 1 week after transplant. In one case, infiltration by recipient T cells was analysed by T cell receptor (TCR) Vß spectratype analysis; this suggested that changes in the T cell repertoire occur in the donor subglottis mucosal tissues from day 0 to day 7, but that the donor and recipient mucosal Vß repertoires remain distinct. The observed lack of strong immunological responses to the trauma of surgery and ischaemia provides encouraging evidence to support clinical trials of laryngeal transplantation, and a basis on which to interpret future studies involving mismatches.

Perioperative socialization, care and monitoring of National Institutes of Health miniature swine undergoing ocular surgery and sampling of peripheral blood.

Swine are a frequent species of choice for testing new surgical procedures and for transplantation studies. However, information concerning best practice to prepare pigs for surgery and postoperative treatment and monitoring is limited, despite a perception that preoperative socialization is beneficial. Therefore we examined the effect of preoperative visits by project personnel on compliance of 26 National Institutes of Health (NIH) minipigs subject to corneal transplantation. We briefly describe sedation and anaesthesia protocols developed for surgery and multiple postoperative interventions in order to facilitate interpretation of data relating to pig compliance. Preoperative visit variables and measures of preoperative socialization were correlated with postoperative outcome. Principal component analysis (PCA) of postoperative outcome variables identified a factor accounting for 53.5% of the variance that was significantly associated with two factors derived from PCA of preoperative factors (accounting, respectively, for 54.7% and 26.0% of the variance; P = 0.019 for the overall model, P = 0.041 and 0.040 for factors 1 and 2, respectively), such that more time spent with pigs before surgery and higher socialization scores were associated with less postoperative stress and difficulty of eye medication. Moreover, two of the preoperative visit variables, time spent with only one person in the pen and time spent with two or more people in the pen, contributed predominantly to PCA factors 1 and 2, respectively, indicating that they were fulfilling two qualitatively different requirements for socialization. We conclude that NIH minipigs are fully compliant with anaesthetic and postoperative experimental procedures provided they are well-socialized to project personnel before surgery.

Basic surgical techniques in the Göttingen minipig: intubation, bladder catheterization, femoral vessel catheterization, and transcardial perfusion.

The emergence of the Göttingen minipig in research of topics such as neuroscience, toxicology, diabetes, obesity, and experimental surgery reflects the close resemblance of these animals to human anatomy and physiology (1-6).The size of the Göttingen minipig permits the use of surgical equipment and advanced imaging modalities similar to those used in humans (6-8). The aim of this instructional video is to increase the awareness on the value of minipigs in biomedical research, by demonstrating how to perform tracheal intubation, transurethral bladder catheterization, femoral artery and vein catheterization, as well as transcardial perfusion. Endotracheal Intubation should be performed whenever a minipig undergoes general anesthesia, because it maintains a patent airway, permits assisted ventilation and protects the airways from aspirates. Transurethral bladder catheterization can provide useful information about about hydration state as well as renal and cardiovascular function during long surgical procedures. Furthermore, urinary catheterization can prevent contamination of delicate medico-technical equipment and painful bladder extension which may harm the animal and unnecessarily influence the experiment due to increased vagal tone and altered physiological parameters. Arterial and venous catheterization is useful for obtaining repeated blood samples and monitoring various physiological parameters. Catheterization of femoral vessels is preferable to catheterization of the neck vessels for ease of access, when performing experiments involving frame-based stereotaxic neurosurgery and brain imaging. When performing vessel catheterization in survival studies, strict aseptic technique must be employed to avoid infections(6). Transcardial perfusion is the most effective fixation method, and yields preeminent results when preparing minipig organs for histology and histochemistry(2,9). For more information about anesthesia, surgery and experimental techniques in swine in general we refer to Swindle 2007. Supplementary information about premedication and induction of anesthesia, assisted ventilation, analgesia, pre- and postoperative care of Göttingen minipigs are available via the internet at http://www.minipigs.com(10). For extensive information about porcine anatomy we refer to Nickel et al. Vol. 1-5(11).

A surgical device for minimally invasive implantation of experimental deep brain stimulation leads in large research animals.

BACKGROUND: Deep brain stimulation (DBS) in experimental animals has promoted new indications and refined existing treatments. Implantation of downscaled clinical DBS leads directly compatible with commercially available implantable pulse generators can however be challenging. Accordingly, we have developed a lead implantation device (LID) and technique for minimally invasive implantation of experimental multicontact DBS leads in large research animals. MATERIALS AND METHODS: The LID carries a small-diameter biocompatible polyimide guide tube which is first used for inserting the stimulating end of the lead and then implanted subcutaneously with the rest of the lead. The functionality of the device was tested by implanting 2 different designs of experimental DBS leads in 12 Göttingen minipigs for up to 12 weeks. The brains were histologically analyzed in order to assess implantation accuracy and local tissue reaction. RESULTS AND CONCLUSIONS: The LID was easy to handle and capable of accurate stereotaxic implantation of downscaled experimental DBS leads in the predetermined target brain structures with minimal surrounding tissue reaction. The device may benefit future large animal DBS research as it allows for precise implantation of DBS leads and may have implications for further refinement of clinical DBS leads.

Immediate intramyocardial bone marrow-derived mononuclear cells implantation in minipig myocardium after permanent coronary artery ligation: magnetic resonance imaging with histopathologic and immunochemical correlation.

OBJECTIVES: : To investigate the effects of immediate intramyocardial implantation of autologous bone marrow-derived mononuclear cells (BMDMNCs) in minipig myocardium after coronary artery ligation with magnetic resonance imaging (MRI), histopathologic, and immunochemical studies. MATERIALS AND METHODS: : Of the 12 minipigs subjected to permanent left anterior descending coronary artery ligation, 6 were immediately treated with intramyocardial BMDMNCs (3 × 10 cells) implantation in the infarct area, whereas the other 6 were treated with intramyocardial injection of an equal amount of saline served as controls. Cardiovascular MRIs, including cine, first-pass, and late gadolinium enhancement (LGE) sequences, were performed on postoperative days 3 and 90. Postmortem infarct size and the degree of fibrosis on histopathologic examination were compared between 2 groups. The degree of BMDMNC differentiation was assessed with flow cytometry, whereas engraftment of BMDMNCs and vascular density was evaluated with confocal immunofluorescence microscopy and immunohistochemical staining, respectively. RESULTS: : There were no significant differences in cardiac function, first-pass dynamics, and LGE between the BMDMNC-treated group and the control group on day 3. On day 90, the BMDMNC-treated group had significantly higher left ventricular (LV) mass/body-weight ratio, lower end-diastolic or end-systolic LV volume/body-weight ratios, higher ejection fraction, better contractility, greater upslope and peak enhancement of the infarct areas, smaller hypoperfused area on first-pass study, and smaller enhanced area and infarct transmurality on LGE MRI than the control group. Flow cytometry revealed high cellular positivity of mesenchymal stem cell surface markers (CD90 and CD271) of the in vitro expanded cells on day 21 after cell culture. In the infarct and peri-infarct areas of the BMDMNC-treated group, there was limited myogenic-like cell differentiation, some engrafted undifferentiated cells, but prominent CD31-positive endothelial cells. On the other hand, a significantly higher number of α-smooth muscle actin-positive small vessel (≤ 25 µm) was noted in the BMDMNC-treated group compared with that in the controls. CONCLUSIONS: : After myocardial infarction in a swine model, immediate intramyocardial BMDMNCs implantation may promote neovascularization with resultant improvement in LV function, perfusion, and myocardial viability as demonstrated on cardiovascular MRI.

Vascular access port implantation and serial blood sampling in a Gottingen minipig (Sus scrofa domestica) model of acute radiation injury.

Threats of nuclear and other radiologic exposures have been increasing, but no countermeasure for acute radiation syndrome has been approved by regulatory authorities. Because of their similarity to humans in regard to physiology and anatomy, we are characterizing Gottingen minipigs as a model to aid the development of radiation countermeasures. Irradiated minipigs exhibit immunosuppression, severe thrombocytopenia, vascular leakage, and acute inflammation. These complications render serial acquisition of blood samples problematic. Vascular access ports (VAP) facilitate serial sampling, but their use often is complicated by infections and fibrin deposition. We demonstrate here the successful use of VAP for multiple blood samplings in irradiated minipigs. Device design and limited postoperative prophylactic antimicrobial therapy before irradiation were key to obtaining serial sampling, reducing swelling, and eliminating infection and skin necrosis at the implantation site. Modifications of previous protocols included the use of polydioxanone sutures instead of silk; eliminating chronic port access; single-use, sterile, antireflux prefilled syringes for flushing; strict aseptic weekly maintenance of the device, and acclimating animals to reduce stress. VAP remained functional in 19 of 20 irradiated animals for as long as 3 mo. The remaining VAP failed due to a small leak in the catheter, leading to clot formation. VAP-related sepsis occurred in 2 minipigs. Blood sampling did not cause detectable stress in nonanesthetized sham-irradiated animals, according to leukograms and clinical signs.

Development of a model of sacrocaudal spinal cord injury in cloned Yucatan minipigs for cellular transplantation research.

Research into transplantation strategies to treat spinal cord injury (SCI) is frequently performed in rodents, but translation of results to clinical patients can be poor and a large mammalian model of severe SCI is needed. The pig has been considered an optimal model species in which to perform preclinical testing, and the Yucatan minipig can be cloned successfully utilizing somatic cell nuclear transfer (SCNT). However, induction of paralysis in pigs poses significant welfare and nursing challenges. The present study was conducted to determine whether Yucatan SCNT clones could be used to develop an SCI animal model for cellular transplantation research. First, we demonstrated that transection of the sacrocaudal spinal cord in Yucatan SCNT clones produces profound, quantifiable neurological deficits restricted to the tail. We then established that neurospheres could be isolated from brain tissue of green fluorescence protein (GFP) transfected SCNT clones. Finally, we confirmed survival of transplanted GFP-expressing neural stem cells in the SCI lesion and their differentiation into glial and neuronal lineages for up to 4 weeks without immunosuppression. We conclude that this model of sacrocaudal SCI in Yucatan SCNT clones represents a powerful research tool to investigate the effect of cellular transplantation on axonal regeneration and functional recovery.

Parameters for successful pig islet isolation as determined using 68 specific-pathogen-free miniature pigs.

BACKGROUND: Islet cell transplantation is a novel therapeutic modality for the cure of diabetes. Pig islet cells are an attractive substitute for human islet cells; however, they are known to be particularly difficult to isolate because of a weak islet capsule and a tendency to be fragmented during enzymatic digestion. Therefore, parameters favoring successful pig islet isolation were investigated using specific-pathogen-free (SPF) miniature pigs. METHODS: Sixty-eight SPF miniature pigs were used for islet isolation. Birth weight, body weight, age, sex, pregnancy history, and the fasting blood glucose levels of each pig were determined. Each pig's general condition was assessed with regard to feeding status and physical activity. Pancreas procurement was performed by one surgical team. Anesthesia duration, operation duration, procedure quality, and perfusate type were recorded. After pancreatectomy, a biopsy was performed for islet density analysis. Decapsulation, cannulation duration, degree of distension, and cold ischemic time were assessed. During islet isolation, pancreas weight, digestion time, and digested tissue proportion were recorded. Isolation results were evaluated by total islet equivalents (IEQ), islet equivalents per gram of pancreas (IEQ/g), isolation index, islet recovery rate, purity, and visual grade. To identify the predictors of higher islet isolation yield, we performed binary logistic regression analysis with significant (P < 0.05) variables from the univariate analysis. RESULTS: The pigs were categorized into high (n = 34) and low yield (n = 34) groups according to the median IEQ/g or total IEQ values. Body weight and age were significantly different between the two groups. Being male or a positive history of pregnancy in females was factors favoring successful islet isolation. General condition assessments failed to estimate islet isolation results. Long anesthesia duration, which might have caused ischemic injury to the pancreas, negatively affected islet isolation results. Decapsulation, cannulation duration, and subsequent pancreas distension were significantly important in successful islet isolation. Inter-lot variability of Liberase was not observed because of screening processes performed before purchase. Isolation index and islet recovery rate correlated well with islet yields. CONCLUSIONS: Multivariate analysis using total IEQ and IEQ/g as outcome variables indicated that age older than 2, being male and moderate distension by Liberase injection are major determinants influencing successful islet isolation.

Ossification of the frontal sinus in juvenile minipigs following water jet application.

BACKGROUND: Obliteration of the frontal sinus is a generally accepted management for patients with severe craniofacial trauma in whom the sinus cannot be repaired or adequately drained. Effective obliteration requires complete removal of mucosa, sufficient filling of the sinus cavity as well as effective occlusion of the nasofrontal duct. The use of various filling materials for sinus obliteration has been described and include autologous fat, bone, muscle and lyophilized cartilage. MATERIAL AND METHODS: In order to appreciate the advantages of the water-jet scalpel an animal study in 10 juvenile (4 months old) and 10 adult (18 months) minipigs was performed. In 5 juvenile and 5 adult animals the frontal sinus mucosa was removed using the water jet, while in the others bone curettes were used. No occlusion of the frontonasal duct was carried out and no filling material was implanted. All animals were followed-up for 40 days. After sacrifice, radiological, histological and computerized histomorphometrical examinations were carried out. RESULTS: Removal of the mucosa from the sinus was simplified when using the water jet. Previous studies have shown that the selected tissue structures were less traumatized when compared with conventional surgical techniques. In young animals (only) and exclusively following the use of a water-jet scalpel osseous occlusion of the frontal sinus was found at follow-up. Histomorphometric findings revealed a significant increase of bone formation in the frontal sinus area of these animals. CONCLUSION: Based on these experimental results in a small series of juvenile minipigs the water-jet technique is a faster and less traumatic technique (less blood loss) for osteoplastic surgery of the frontal sinus. Further long-term studies are needed to evaluate the possibilities for applying this technique in post-traumatic craniofacial surgery in man.

Evaluation of minipigs as an animal model for alveolar distraction.

OBJECTIVE: Alveolar distraction osteogenesis is a relatively novel tissue regeneration technique that remains, in some respects, at an experimental stage. The selection of an experimental animal biomodel is not clearly defined, with reports in the reviewed literature on dogs, sheep, and monkeys. The present objective was to compare 2 experimental biomodels (dog and minipig) using an alveolar distraction protocol with a novel prototype distractor. STUDY DESIGN: Three beagle dogs and 3 Göttingen minipigs were evaluated, placing the distractor at the right hemimandible alveolar ridge after previous extraction of premolars. The radiological examination was carried out immediately after the distraction and at 2 weeks of consolidation. RESULTS: Satisfactory clinical and radiological results were obtained in 2 of 3 beagle dogs after the previous unilateral extraction of mandibular and maxillary premolars. During the consolidation, a height gain of approximately 5 mm was observed, with the appearance of radiodense bone trabeculae in the distraction chamber. The distraction failed in all of the minipigs. CONCLUSION: The minipig was not an appropriate biomodel for the study of alveolar distraction because the investigators were not able to maintain the seal of the distraction chamber or the stability of the distractor.

Mortality rates of interventional and surgical procedures performed in domestic juvenile farm pigs and Yucatan mini-pigs.

Perioperative and postoperative care are critical factors in cardiac catheterization and cardiothoracic surgical procedures. A retrospective analysis of mortality data in cardiovascular catheter and surgical studies performed in domestic juvenile swine (DJS) and Yucatan mini-swine (YMS) was conducted. A total of 529 animals in 35 studies were included in the analysis, which included six study categories: coronary stenting (Stent) and percutaneous transluminal coronary angioplasty (PTCA) alone; Stent and PTCA in combination with ionizing radiation (Stent/Rad, PTCA/Rad); myocardial ischemia (ISCH); and three non-ISCH surgical procedures grouped under "other surgeries" (Other Surg). Casualties were defined as animals that died spontaneously before the assigned termination date. The highest mortality rate occurred in the ISCH group (29.7% +/- 2.2%). Mortality of the Stent/Rad animals (26.1% +/- 6.3%) was significantly higher than those in the Stent and PTCA groups (12.1% +/- 3.1% and 7.9% +/- 3.2%; P< 0.05 for both). Similarly, mortality in the ISCH group was significantly higher than that in the Stent, PTCA, or Other Surg animals (29.7% +/- 2.2% versus 12.1% +/- 3.1%, 7.9% +/- 3.2%, and 3.0% +/- 3.0%, respectively; P< 0.05 for all comparisons). We did not observe differences between YMS and DJS. Most casualties in the ISCH group took place during weeks 1 (28.0% +/- 8.4%) and 4 (29.3% +/- 6.2%) after placement of the coronary ameroid constrictor. The majority of animals in the Stent/Rad and PTCA/Rad groups died within 1 week after the procedure (67.7% +/- 12.8% and 79.3% +/- 12.5%, respectively). We conclude that radiation therapy used in combination with stenting increases the mortality rate of this catheter-based procedure. Animals subjected to ISCH or a transcatheter procedure in combination with ionizing radiation should be monitored closely during the perioperative period to prevent unacceptably high mortality rates.

[Defecation properties after coloanal reconstruction in the pig model]. / Defäkationsverhalten nach koloanaler Rekonstruktion im Schweinemodell.

UNLABELLED: Defecation properties after coloanal reconstruction in the pig model. OBJECTIVE: Functional aspects after low anterior resection are of major interest. While patients with straight coloanal anastomoses may suffer from disabling stool frequency and incontinence, evacuation difficulties can be a problem in coloanal pouch anastomoses. The aim of the study was to investigate functional results by establishing a standardized defecation protocol after low anterior resection of the rectum in the pig model. METHOD: 24 adult Göttinger mini pigs were studied. They were randomly assigned to three groups: 8 animals served as control animals (group 1), the remaining 16 underwent low anterior resection with small colon-J-pouch (4-5 cm) reconstruction (n = 8) and large pouch design of 8-9 cm length (n = 8). The animals were investigated after 12 weeks postoperatively. Defecation properties we studied using a Ceruletide-induced defecography (0.3 microgram kgKG) with a 100 ml barium sulfate bolus, placed just above the anastomosis. RESULTS: Evacuation was significantly impaired in the large pouch (45 min.). However, the small pouches evacuated completely after 14 min. which was comparable to the unoperated controls (17.3 min.). CONCLUSION: Ceruletide-induced defecation reveals reproducible results in pigs. Evacualtion properties are highly depending upon the coloanal reconstruction. A small colon-J-pouch design reveals nearly physiologic results 3 months after surgery.

Anaesthesia and basic experimental surgery of minipigs. A practical exercise.

Minipigs tolerate anaesthesia very well. The only disadvantages are the difficulties in performing venous puncture and endotracheal intubation. To overcome these the animals should be well sedated prior to induction by intravenous injection, and deeply anaesthetized prior to the introduction of the endotracheal tube. Anaesthetic regimen and several basic experimental surgical techniques will be practised.

Fetal surgical protocols in Yucatan miniature swine.

Thirty-nine Yucatan miniature swine were used in three fetal surgical experimental protocols. They involved antiarrhythmic administration, pacemaker implantation, and in-utero diagnosis of ventricular septal defect by intraoperative echocardiography. Because of problems encountered with surgical protocols in the initial stages, modifications were made to prevent fetal hypothermia and intraoperative mortality. These modifications included environmental temperature support, staple surgical techniques to reduce operative time, and development of fetal catheters designed to facilitate cannulation of small vessels. Postoperative care protocols were intensive and included antibiotics, analgesics, and supportive care designed to reduce discomfort and prevent abortion and sepsis. Thirty-seven of 39 sows survived the surgical procedures; experiments were performed on 117 fetuses. Twenty-two fetuses died either intraoperatively or postoperatively because of complications related to the experimental protocols. Modification of surgical and postsurgical protocols for these projects demonstrates the feasibility of using miniature swine as a model for fetal surgery, when their use was appropriate for anatomic and physiologic reasons.

A technique for extracorporeal circulation in the Goettingen minipig allowing recovery and long-term follow-up.

The objective of our study was to establish an animal model with extracorporeal circulation (ECC) for investigations on the long-term tolerability of different pericardial substitutes using the Goettingen minipig. A combination of halothane (0.4-0.6% vaporizer setting) in oxygen and nitrous oxide (FiO2 0.33), with the opioid piritramide (75 micrograms/kg/h i.v.) was used for anaesthesia. A muscle relaxant was not administered. Due to the size of the animals (mean body weight 37.6 kg) the operative procedure was the same as in humans. Specific changes preceding or following initiation of cardiopulmonary bypass (CPB), such as inactivation of the coagulation system (400 IU heparin/kg i.v.), haemodilution, and hypothermia (32 degrees C), did not result in any complication. We did not induce cardiac arrest during CPB in order to facilitate haemodynamic stability after weaning from CPB. In three animals a temporary increase in blood pressure occurred after protamine (2.5-3.0 mg/kg i.v.) was given to reverse the heparinization. Within 60 minutes after the end of surgery all animals could be extubated when spontaneous breathing and cough reflex were present. The postoperative follow-up period of nine months was uneventful apart from one animal which developed a superficial wound in the thoracic scar area. We conclude that our technique for ECC is a safe method allowing recovery and long-term follow-up after cardiac surgery in a porcine animal model.

Tracheoesophageal anastomosis, continent gastrostomy and oesophagostomy--a new experimental model in minipiglets.

Tracheoesophageal fistulae endanger newborn children by aspiration pneumonia. An animal model of this dangerous malformation was thought to be impossible until now. By tracheoesophageal anastomosis, occlusion of the oesophagogastral junction, proximal cervical oesophagostomy and continent gastrostomy in 25 minipiglets a reliable model of tracheoesophageal fistula has been developed. After establishing the model in a pilot study the mortality following the establishment of this procedure was 5.6% and the minipiglets survived in excellent condition for 2-10 week periods under complete alimentary restriction and gastrostomy feeding. Therefore the method seems to be suitable for long-term investigations on major oesophagotracheal surgery.