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Biomedical subjects

D Mettler

Publications and source records attributed to D Mettler.

36 records · Page 2Linked to original sources
PubMed1994

Effects of halothane and isoflurane anaesthesia on microcirculatory blood flow in musculocutaneous flaps.

Hypoperfusion and necrosis in musculocutaneous flaps used for reconstruction of tissue defects is still a significant clinical problem. Although the causes of hypoperfusion are frequently surgical in nature, little is known about the effects of anaesthetic management on blood flow in flaps or the outcome of flap surgery. We compared in minipigs the effects of halothane and isoflurane anaesthesia in equipotent doses on microcirculatory blood flow (MBF) in the skin and muscle part of musculocutaneous flaps and also in intact (control) skin and muscle. Measurements were made during stable normovolaemic conditions and during mild to moderate hypovolaemia (withdrawal of 5%, 10% and 15% of total blood volume). Multi-channel laser Doppler flowmetry (LDF) was used to measure MBF and electromagnetic flowmetry (EMF) for total flap blood flow. During normovolaemic conditions there was no significant difference between the two groups in central haemodynamic or respiratory data. After 15% blood loss, however, there was a significant decrease in mean arterial pressure and cardiac output in the halothane group while there was no significant change in the isoflurane group (P < 0.05). MBF in control skin, control muscle and flap muscle remained approximately 10-15% higher in the isoflurane than in the halothane group throughout the study. In the isoflurane group, MBF in flap skin was unchanged during normovolaemia and there was less than 10% decrease during hypovolaemia. In the halothane group hypovolaemia caused a significant decrease in MBF in flap skin: 27% decrease after 5% blood loss, 45% decrease after 10% blood loss and 49% decrease after 15% blood loss compared with 5%, 20% and 21%, respectively, in intact skin.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Experimental assessment of thrombogenicity in vascular prostheses before and during prostaglandin E1 treatment.

The effect of prostaglandin E1 (PGE1; Prostavasin), a powerful platelet blocking agent, was assessed on various new synthetic or biological prostheses in a 6-min in vivo extra corporal arterio-venous (AV) shunt. In eight anaesthetised and heparinised minipigs (weight 25.1 +/- 1.9 kg) the following materials were tested before and during PGE1 infusion (alprostadil-alpha-CD; 40 micrograms/50 ml NaCl/50 min or 0.8 microgram/min): PTFE, (Gore-tex, TW, 4 mm ID); Xenograft, Biologic (Solcograft, 5 mm ID), (non-porous) and Dacron (Atrium, 4 mm ID); polyurethane 1 (Braun-Melsungen, 4 mm ID); polyurethane 2 (S. Gogolewski, 4 mm ID), (porous). Technetium-labelled platelet deposition and blood flow were measured; morphology was assessed by scanning electron microscopy (SEM) and histology. Compared to control levels, PGE1 infusion had a significant systemic effect on mean arterial pressure required by the protocol (MAP 82.6 vs. 66.6 mm Hg; p < 0.001) and flow (173.6 vs. 134.8 mm/min; p < 0.001). Standardised platelet counts per area showed a marked overall decrease from 197 to 130 counts/min/mm2; NS). The morphological assessment by SEM showed a slight increase of surface cellular deposition (score: 6.7 vs. 8.3), the histology score being unchanged (3.9 vs. 3.7). Looking at deposition of platelets for each prosthesis, the porous materials showed a net improvement after PGE1 treatment as compared to non-porous materials. We conclude that PGE1 may be of benefit by reducing platelet deposition in synthetic porous vascular prostheses in the early phase.

Alprostadil↗
PubMed1991

90Y-resin particles--animal experiments on pigs with regard to the introduction of superselective embolization therapy.

Resin particles (diameter 45-75 microns) were labelled with 90Y, suspended in a glucose/dextran solution and infused into the kidneys of 3-month-old pigs (tumour model). Both kidneys of each animal were embolized with particles, but only one with active (90Y loaded) particles and the other, for comparison, with inactive particles. The organ measurements showed less than 1% of injected activity in bone, bone marrow, liver and lung compared to greater than 99% retention by the kidneys. Only minimal shunted activity was found in blood (less than 0.27%) and urine (less than 0.07%). There was a clear shrinkage of the 90Y-treated kidneys with a reduction in weight of up to 50%. Histologically, the ischaemic lesions (infarcts and atrophy) were clearly more pronounced and extensive in the 90Y-embolized kidneys than in the non-radioactive embolized kidneys. Furthermore, severe arterial wall changes and fibrotic necrosis due to radiation damage were observed in the 90Y-treated kidneys. It is concluded that with intra-arterially applied particles a dose of about 100 Gy is sufficient to completely destroy tissue-specific structures. Complications due to acute necrosis or inflammatory reactions were not observed, and there were no shunt related alterations seen in the liver or lungs. The 90Y-loaded resin particles are considered suitable for a super selective intra-arterial radioembolization.

Anesthesia↗
PubMed1991

2,3-butanediol in experimental myocardial ischaemia in pigs.

To investigate the role of 2,3-butanediol in myocardial ischaemia we analysed this compound in pig's myocardium and blood. Ischaemia was induced by ligation of a coronary artery. In the first study we found significantly higher levels of 2,3-butanediol in the homogenate of ischaemic myocardium than in non-ischaemic myocardium. The lactate concentration was also significantly elevated. In the second study, where ischaemia was similarly induced, and where reperfusion was achieved by re-opening the ligated coronary artery after 20 min, 2,3-butanediol in peripheral blood was found to increase significantly. In the pigs in which the coronary artery was not re-opened, the 2,3-butanediol level in peripheral blood was unchanged. We conclude that in pigs' anaerobic myocardia accumulation of 2,3-butanediol occurs; if the myocardium is reperfused this metabolite also appears in the blood.

Animals↗
PubMed1990

[Evaluation of recent vascular prostheses in the arteriovenous shunt].

Prosthetic vascular replacement materials are still suboptimal especially for distal peripheral and coronary bypass grafts due to the small caliber and high occlusion rates. Therefore new vascular grafts have been assessed with respect to blood compatibility, thrombogenicity and host pretreatment. In 12 heparinized minipigs (25 kg), a total of 120 small caliber grafts (i.d. 3.0 mm) were perfused (6 min) in a femoro-femoral arteriovenous shunt (AVS). Materials included: Dacron (Atrium), PTFE (Gore), Polyurethanes (PU), Auto- and Xenografts. Animals were treated preoperatively with fishoil (3 g EPA/QD x 3 weeks = group I), perioperatively with prostaglandins (PGE1 = group II) or with fishoil and graft incubation in plasma proteins (= group III) and compared to controls without pretreatment (= group 0). We measured flow, deposition of marked thrombocytes (HMPAO-Tc* per area and per weight). - Blood flow was similar in AVS for all groups and materials (168 +/- 86 ml/min, p = NS). There was no significant correlation in deposition of marked thrombocytes and host pretreatments (group 0: controls = 7356 counts/area, group I: fishoil = 6807. group II: PGE1 = 7864). However graft incubation in plasma proteins significantly lowered deposition of marked thrombocytes (1766 in group III vs. 7356 in group 0: p less than 0.05). And significant differences of thrombocyte counts where found between the different materials: Autografts less than PTFE less than Xenografts less than Small Pore PU less than Dacron less than Large Pore PU.--AVS is a useful tool to determine early thrombogenicity in prosthetic vascular replacement materials and to assess the effect of different host pretreatments.

Animals↗
PubMed1989

Conversion of induced ventricular tachycardia by single and serial chest thumps: a study in domestic pigs 1 week after experimental myocardial infarction.

A single chest thump (CT) is widely accepted in the emergency treatment of ventricular asystole, whereas there exists controversy about this method for the interruption of ventricular tachycardia (VT). Hitherto, delivering serial chest thumps (SCTs) has been described only once for the treatment of VT. A systematic analysis for interruption of VT by CT or SCTs (or both) is lacking. We have therefore investigated this subject in five domestic pigs after experimental myocardial infarction. Manual conversion was attempted in 20 induced VTs. Six VTs were converted by CT, seven VTs were converted by the first SCTs, and six VTs were converted by the last of multiple (two to seven) SCTs. The overall success was 95%. There were no serious complications. The rate of successful SCTs exceeded the rate of VT by 10% to 126%. The technique of SCTs, the mechanisms of manual conversion, and the controversial opinions regarding the value of precordial thumping in asystole, VT, and ventricular fibrillation are discussed. SCTs should be practiced only very cautiously in patients until further experience is available.

Animals↗
PubMed1989

[The humanitarian stunning of fowl for slaughter with microwaves (2450 MHz)].

Chickens can be killed in less than one second by exposing their heads to microwave irradiation with a frequency of 2450 MHz. Positioning the head exactly is necessary. The only way to avoid this handling is the exposure of the whole body. But because of a particular high rate of absorption the wings are heated so that the meat is not edible any more. Before slaughtering the chickens are hung up headlong. This causes increased cardiac and respiratory frequencies while the blood pressure is not altered yet. This handling is a considerable stress. Animal-prevention arguments suggest to prefer anaesthesia before hanging the chickens in the conveyor belt.

Abattoirs↗
PubMed1987

Extracorporeal isolated pig liver perfusion: influence of various blood primes on liver function.

Extracorporeal isolated pig liver perfusion was performed in three groups of five piglets each to assess the influence of different blood primes on liver function. All prime volumes were hemodiluted to a hematocrit of 0.3-0.35 and adjusted to a pH of 7.35-7.45 with sodium bicarbonate at a temperature of 38 degrees C. Fresh slaughterhouse blood was collected, mechanically filtered and used in Group A, whereas analogously collected blood was biologically filtered by passage through the organism of the piglet in Group B. In Group C, the priming blood consisted of autologous blood gained during hepatectomy by a special technique. A high potassium concentration (10.4 +/- 0.94 mmol/l) in Group A and impurities of the slaughterhouse blood in both Groups A and B led to rapid edema formation and an increase in vascular resistance of the perfused liver, and a prolonged perfusion was not achieved. In the third group, however, liver perfusion over a period of 5 h without any deterioration of liver function was possible. Beside liver function tests, oxygen consumption, the macroscopic aspect and bile flow of the liver seemed to be the most reliable parameters in assessing the function of the isolated perfused pig liver. Our technique to gain autologous blood can be recommended not only for extracorporeal liver perfusion but also for any other extracorporeal isolated organ perfusion.

Animals↗
PubMed1987

Experimental pancreaticosplenic composite transplantation in the pig. Operative technique and assessment of graft function.

A large animal model for substitutive pancreaticosplenic composite transplantation with urinary drainage to the bladder has been developed in the pig. Transplantations were performed in 7 nontissue-typed donor-recipient combinations without immunosuppressive medication. Six recipients showed perfect graft function at least until the 5th postoperative day. Blood glucose, intravenous glucose tolerance tests and urine amylase concentrations proved to be sensitive markers of graft function. Scintigraphic follow-up examination with 99mTc tin colloid could only record perfusion of the splenic transplantation. With this model the role of the spleen in pancreaticosplenic composite transplantations can be studied in forthcoming experiments.

Amylases↗
PubMed1986

Orthotopic liver transplantation in pigs without cold perfusion of the donor liver. Evaluation by quantitative liver function tests.

Orthotopic liver transplantation (OLT) was performed in 12 pigs and liver function assessed before and after transplantation. In 6 pigs OLT was carried out without cold perfusion of the donor liver, whereas in the other 6 animals the donor organ was perfused in situ. 5/6 animals without perfusion and 4/6 with cold perfusion survived for more than 10 days. Significantly better liver function was revealed by the aminopyrine breath test (ABT) and the indocyanine green (ICG) disappearance in the group with the cold perfusion of the liver, whereas no differences in routine liver function tests were seen between the two groups. Although OLT without cold perfusion of the donor liver is feasible and prolonged survival of animals is possible, the function of these organs is markedly reduced compared to the cold perfused organs. This method can, therefore, not be recommended. ABT and ICG disappearance are sensitive tests for the evaluation of the liver function in the post-transplant period.

Aminopyrine↗
PubMed1986

CT appearance of impaired lymphatic drainage in liver transplants.

Early postoperative CT scans of three patients who had undergone liver transplantation show hypodense areas surrounding the portal venous system and to a lesser extent the intrahepatic inferior vena cava. These changes were considered to represent dilated lymphatic vessels caused by impaired lymphatic drainage of the transplant after total interruption of the lymphatic vessels at surgery. This hypothesis was tested in three piglets after complete surgical interruption of the lymphatic vessels of the liver. Results of histologic examinations and an additional long-term follow-up CT study in one patient suggest that hypodense periportal and pericaval areas are a reversible CT finding in liver transplants caused by lymph stasis.

Adult↗
PubMed1985

Surgical repair of the kidney after blunt lesions of intermediate degree using a Vicryl mesh: an experimental study.

Twelve experimentally induced blunt renal lesions in pigs were treated either with an alloplastic renal capsule made of semi-elastic Vicryl mesh or with homologous pig fibrin adhesive or with through-and-through chromic catgut sutures as controls. The Vicryl mesh capsule was made by the Ethnor Company (Paris, France) to our specifications. The postoperative isotope nephrograms, which were repeated until the Vicryl had been fully resorbed, showed good renal function in every case. However, when compared to the controls, the kidneys which had been repaired with Vicryl mesh contained considerably less scar tissue at the site of parenchymal rupture and showed neither perirenal fibrosis nor atrophy of the parenchyma in the vicinity of the capsule. Our preliminary results seem to confirm that simple and rapid surgical treatment of moderately severe blunt renal lesions is possible using the alloplastic Vicryl mesh capsule. The method may also be suitable for reconstruction of the parenchyma following multiple nephrotomies, such as for removal of staghorn calculus, and experimental investigations are under way to clarify this point.

Animals↗
PubMedDate not supplied

Circulatory and anatomic differences among experimental gastric tubes as esophageal replacement.

In this experimental study we measured microcirculatory and anatomic differences among a newly developed technique of gastroplasty--fundus rotation gastroplasty (FRG)--and conventional (CG) and reversed (RG) gastric tubes as substitutes for the thoracic and cervical esophagus. After transhiatal esophageal resection, 36 large white pigs were randomly assigned to have an FRG, CG, or RG. Tube length, gastric volume, and compliance as well as blood flow in the tube and the remaining gastric reservoir (by laser Doppler flowmetry) were measured. The FRG tubes were 35.9 +/- 3.1 cm long, RG 38.7 +/- 3.3 cm, and CG 27.3 +/- 2.1 cm (p < 0.05). Gastric compliance was 20.8 ml in the FRG and 3.2 ml and 2.9 ml in the CG and RG, respectively (p < 0.001). Blood flow was significantly higher in FRG tubes than in RG tubes or CG tubes, resulting in a lower anastomotic failure rate (2/12 FRG, 6/12 CG, 7/12 RG). Hence a rotation flap of the gastric fundus (FRG) yields a long, well perfused tube by maintaining the blood supply of the gastric lesser curvature. FRG appears to be a good alternative to CG or RG as a substitute for the thoracic and cervical esophagus.

Anastomosis, Surgical↗
PubMedDate not supplied

Organ-preserving resection of the gastroesophageal junction and substitution with a gastric corpus rotation tube: an experimental study.

Premalignant lesions of the gastroesophageal junction are treated conservatively or by antireflux surgical procedures. We describe a novel technique that replaces the distal esophagus after resection of the gastroesophageal junction. After resection of the gastroesophageal junction, 16 pigs were divided into two groups. In group 1 (n = 9) the gastroesophageal junction was replaced with a 3 cm wide horizontal gastric corpus tube, pedicled at the lesser curvature. In group 2 (n = 7) the tube was pedicled at the greater curvature. Tube length, volume, and compliance of the gastric remnant and blood flow in the tube (by laser Doppler flowmetry given in perfusion units [PU]) were measured before and after tube formation and 2 weeks postoperatively. Group 1 tubes were 9.5 +/- 1. 5 cm long and group 2 tubes were 8.2 +/- 0.7 cm long. Tube formation decreased volume and compliance of the gastric remnant. After tube formation, blood flow at the tip of the tube decreased from 254 PU to 64 +/- 22 PU (group 1) and 87 +/- 36 PU (group 2). Volume, compliance, and blood flow returned to baseline values 2 weeks postoperatively. No anastomotic leakage was found on postmortem examination. Horizontal gastric corpus tubes might offer an alternative to replace the distal esophagus and proximal stomach after resection of premalignant lesions of the gastroesophageal junction.

Animals↗
PubMedDate not supplied

Marked interspecies differences between humans and pigs in cyclosporine and prednisolone disposition.

Pigs have been used extensively in various transplantation protocols. Immunosuppressive therapy is usually performed by steroids and cyclosporine A (CyA). For rational dosage of these xenobiotics, their pharmacokinetics should be characterized. Therefore, we investigated the kinetics of prednisolone, an immunobiologically active steroid, after oral and iv administration, and of CyA, after oral and iv dosing, in seven pigs and compared these results with those obtained in 20 renal transplant patients. The mean area under the blood concentration versus time curve of CyA (HPLC measurements) was lower in pigs than in humans after oral (67 +/- 31 micrograms/ml x min vs. 296 +/- 101 micrograms/ml x min) and after iv (358 +/- 71 micrograms/ml x min vs. 858 +/- 292 micrograms/ml x min) doses of CyA. Compared to humans, pigs had lower concentrations of total prednisolone--assessed by HPLC--after oral prednisone (7.1 +/- 4.3 micrograms/ml x min vs. 297.9 +/- 75.6 micrograms/ml x min) and after iv prednisolone (26.8 +/- 9.5 micrograms/ml x min vs. 373.3 +/- 77.7 micrograms/ml x min). The plasma concentrations of both agents, lower in pigs than in humans, were attributable to an increased volume of distribution, an increased clearance, and more of a diminished systemic availability in pigs than in humans. Thus, to obtain the same target concentrations of CyA and prednisolone in both species, pigs require about 2 to 4 times higher iv or oral doses of CyA and 10 to 30 times higher iv or oral doses of steroids.

Administration, Oral↗
PubMedDate not supplied

Laparoscopic liver resection in the Large White pig--a comparison between waterjet dissector and ultrasound dissector.

Resection of 16 liver lobes was successfully undertaken laparoscopically in anaesthetised Large White pigs. These animals proved to be suitable for the instruments used in human laparoscopic procedures. It was planned to undertake a comparison between the waterjet and ultrasound dissectors, but this proved impossible because of the development of a thick intraabdominal mist during dissection with the waterjet dissector. The ultrasound dissector was effective in dissecting the intraparenchymal hepatic structures, especially the portal vein and the hepatic vein. These blood vessels were safely secured with endoclips, while bleeding points on the resection surface were coagulated with an argon beam coagulator. The liver specimens removed were approximately 75 g in weight. All ultrasound-dissected animals survived for 10 days. Post-mortem evaluation showed two cases of wound infection, one case of subphrenic abscess and two cases of biloma. Our results emphasise the potential of laparoscopic resection techniques for formal or at least peripheral liver resections in humans.

Animals↗