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A Mehrabi

Publications and source records attributed to A Mehrabi.

71 records · Page 4Linked to original sources
PubMed1997

[Computer-based training--a new method in surgical education and continuing education].

Computer-based training (CBT) programs teach the material of a specific field and at the same time offer various ways of objectively checking the knowledge gained. The interactive use of multimedia components, such as text, graphics, animation, sound, digital slide shows, videos and quizzes, facilitates the learning process. The aim of this study was the development and evaluation of a CBT program for use by surgeons teaching students. Using SuperCard, a teaching module for distal radius fracture (DRF) was developed, containing detailed clinical information. Video clips and vivid animation combine theoretical knowledge with practical experience. Fourth-year medical students (n = 103) were tested after using the module for 90 min. Other students (n = 47) served as the control group. In a 90-min lecture, DRF was discussed. In all evaluated criteria (distinctness, detailed description, presentation of materials, structure, motivation to learn, time saved while learning and memory retention), CBT gained 15-20% better scores than the lecture. Although 87% of the students stated that their experience with computers was limited or insufficient, 100% found the use of CBT systems helpful in student teaching. Most of them suggested the use of such programs as a exam preparation/self study method (90%) or as a supplement to a lecture (40%). Based on these evaluations, it is clear that CBT modules are an appropriate future teaching and learning system that will be well accepted. In conclusion, CBT programs should be integrated into medical education as a valuable supplement. With this aim, CBT systems should be developed and used at universities as an information system for the surgical residency program.

Achievement↗
PubMed1996

Continuous measurement of porcine renal cortex microcirculation with enhanced thermal diffusion technology.

Continuous monitoring of renal cortical blood flow (RCBF) in the perioperative setting of aortic or renal vascular surgery could facilitate the early detection of vascular complications, possibly resulting in a reduction of postoperative renal failure. A new prototype system for measurement of parenchymous organ perfusion based on the principle of thermal diffusion ("TD"-Thermal Diffusion Electrode, Thermal Technologies Inc., Cambridge, MA, USA) was used for RCBF measurements in the outer cortex of the porcine kidney. We validated the sensitivity of the device to detect renal blood flow impairment, comparing TD flow data with renal artery blood flow values (RABF), measured by ultrasonic flow probes. The hypothesis was tested that acute disturbances of RCBF, induced by a variable degree of renal artery stenosis, can be immediately detected and continuously monitored by TD measurements in the porcine renal cortex. Mean baseline RCBF measured by TD electrodes was 68.1 +/- 25.0 ml/100 g/min. Mean baseline RABF was 102.1 +/- 26.6 ml/min. Controlled induction of a variable degree of renal arterial occlusion by implanted vascular balloon occluders was always followed by an immediate and proportional decline of RCBF, as measured by TD. Flow data obtained with both methods were significantly correlated by linear regression (r=.82, r2=.68; P < 0.0001). Dynamic changes of RABF in the time course of renal artery partial/total occlusion and arterial flow release could be continuously followed by detection of corresponding flow changes of RCBF. We conclude that the TD system investigated in the current study allows a continuous and sensitive determination of porcine renal cortex perfusion. A clinical evaluation of the method, e.g., in the perioperative setting of aortic or renal transplantation surgery, now appears to be justified.

Animals↗
PubMed1996

Validation of endothelin (ET) immunoreactivity in human bile by HPLC. Comparison of biliary ET concentration in liver transplant recipients with values obtained during cholecystectomy.

High endothelin (ET) concentrations were recently detected in human bile after orthotopic liver transplantation (OLT). In the present study we compared biliary ET/big-ET levels measured by radioimmunoassay (RIA) in liver graft recipients (n = 37) with levels measured in non-transplant patients during cholecystectomy (n = 38) to clarify the influence of transplantation on the levels of biliary ET peptides. HPLC elution profiles of biliary ET were analyzed for characterization of ET peptide composition and validation of RIA analysis in bile extracts. Mean ET/big-ET levels in the common bile duct after OLT were significantly elevated (ET, 20.9 +/- 15; big-ET, 39.2 +/- 19 fmol/ml) compared to levels in non-transplant patients (ET, 5.7 +/- 4.9; big-ET, 12 +/- 8 fmol/ml). Highest ET/big-ET levels were measured in the gall bladder during cholecystectomy (ET, 61.7 +/- 41; big-ET, 75 +/- 28 fmol/ml). ET and big-ET levels were correlated by linear regression. HPLC analysis reveals the presence of high levels of ET/big-ET in human bile. Biliary ET mostly represents ET-1. High biliary ET levels after OLT appear to be derived from active endothelial secretion and probably reflect hepatic endothelial stress after preservation/ reperfusion. High biliary ET levels could be involved in the mediation of functional cholestatic syndromes after OLT.

Adult↗
PubMed1995

Soluble thrombomodulin--a marker of reperfusion injury after orthotopic liver transplantation.

Thrombomodulin is an endothelial cell membrane protein that is released into the blood in soluble forms (soluble thrombomodulin [sTM]) in response to endothelial cell damage. We evaluated intraoperative sTM as a marker of reperfusion injury in 29 liver transplant recipients using an ELISA. Preoperative sTM levels were significantly elevated, as compared with healthy control subjects (75 +/- 61 ng/ml vs. 17 +/- 10 ng/ml; P < 0.001) and remain unchanged at the end of the anhepatic phase (58 +/- 40 ng/ml). There is an increase to 194 +/- 182 ng/ml 3 min after reperfusion (P < 0.001). Post-reperfusion sTM levels correlate significantly with the early liver enzyme release (aspartate transaminase) (P < 0.001). Patients with pronounced reperfusion injury (postreperfusion arterial sTM > 138 ng/ml, n = 16) present significantly higher maximum aspartate transaminase levels within the first 24 postoperative hr, as compared with patients with less reperfusion injury (arterial sTM < 138 ng/ml, n = 12) (P = 0.001). Released sTM is derived from the graft, since patients with pronounced reperfusion injury present significantly higher sTM levels in the hepatic vein 3 min after reperfusion compared with the portal vein (P < 0.001) and artery (P = 0.025), respectively. In patients with higher reperfusion injury, we found significantly more adherent intrasinusoidal granulocytes in the liver biopsy taken 1 hr after reperfusion (P = 0.006), indicating an interrelation of endothelial damage and the important phenomenon of "leukocyte sticking" in reperfusion injury. Thus the postreperfusion increase of sTM as a marker of reperfusion injury correlates with the early liver enzyme release and the accumulation of intrasinusoidal granulocytes.

Adolescent↗
PubMed1995

[Induction of impaired hepatic microcirculation by in situ hilus preparation in liver explantation].

AIM: Usually, in-situ preparation of the hepatic hilar structures is performed prior to the perfusion with preservation solution. Aim of this study was to investigate mechanical effects of liver preparation on the hepatic microcirculation. METHODS: 16 pigs (German landrace) were randomized in two groups. In both groups, laparotomy was performed after intratracheal intubation. Subsequently, a thermal diffusion probe was implanted into the medial left liver lobe for quantification of microperfusion. In group A (n = 8), bile duct, hepatic artery, and portal vein were exposed and the lesser omentum transsected thereafter. Ultrasound-volume-probes were placed around the hepatic artery and portal vein. Simultaneous measurement of hepatic microperfusion and total liver blood flow was performed five minutes after the end of liver preparation. In group B (n = 8) hepatic microperfusion was quantified 45 minutes after laparotomy without further manipulations. RESULTS: By the preparation, liver perfusion was significantly reduced in group A from 78 +/- 13 ml/100g/min to 61 +/- 16 ml/100g/min. After preparation a total liver blood flow of 137 +/- 46 ml/100g/min was recorded indicating a shunt fraction of 51 +/- 21%. In contrast, hepatic microperfusion in group B remained at baseline during the whole observation period (79 +/- 3 ml/100g/min vs. 78 +/- 5 ml/100g/min). CONCLUSION: In-situ liver preparation induces a relevant disturbance of hepatic microcirculation. Preservation perfusion shortly after surgical manipulation could become ineffective because of an increase in shunt flow. If the regeneration period is too short, e.g. lack of heart explantation, the quality of the liver graft could be limited.

Animals↗
PubMed1994

Intraoperative evaluation of big-endothelin plasma levels during liver transplantation in different vascular compartments.

Endothelin-1 (ET) is derived from its precursor big-ET, secreted by endothelial cells of multiple origin. The role of ET peptides in the physiological responses after orthotopic liver transplantation (OLT) was investigated. Venous big-ET plasma levels were analysed by RIA in 28 patients before and after OLT. Samples for analysis were taken intraoperatively from 12 patients from the caval, portal and hepatic veins and the radial artery at multiple time points. Highest caval levels were found during the anhepatic period and 60 min after reperfusion, followed by a drop and subsequent increase postoperatively. Highest levels in the hepatic and portal veins were detected during explanation and reperfusion. A different pattern was found in the radial artery. Values during rejection and infection were elevated compared with preoperative and postoperative levels. The heterogeneity of the kinetics points to different sites of ET generation, including liver and splanchnic circulation. It suggests a predominant paracrine secretion mode of ET peptides with various stimuli involved. Big-ET levels could reflect endothelial cell damage, as big-ET is generated intracellularly and biological activity is rather weak.

Adult↗
PubMedDate not supplied

A review of various techniques of orthotopic liver transplantation in the rat.

Orthotopic liver transplantation (OLT) in rat is a demanding procedure, which has become a popular model to investigate various problems. Our aim was to review and analyze the various techniques of experimental OLT in the rat. A review of the literature revealed 30 techniques or technical modifications. Each modification represented a change or a simplification of the reconstruction method of five anatomical structures, which are cornerstones of a successful OLT: the suprahepatic inferior vena cava (SHVC), portal vein (PV), infrahepatic inferior vena cava (IHVC), hepatic artery (HA), and bile duct (BD). SHVC is anastomosed via microsuture or cuff. The PV anastomosis is performed by microsuture, cuff, or a microsuture-temporary splint technique. IHVC is reconstructed by a microsuture, cuff, or microsuture-temporary splint technique. Arterialization has been accomplished via microsuture (aortic segment, celiac segment, or aortic patch), cuff, splint, sleeve, or telescopic method. Nonarterialization of the graft has also been described. Methods for BD reconstruction include pull-through, telescopic, splint, and T-tube. Although a high level of microsurgical skill is the basic requirement in the microsuture technique which provides the most physiological situation and concomitantly reduces thrombosis, it increases anhepatic time compared to the cuff procedure. The learning curve of microsuture techniques is flat; beginners need much practice to become expert. The most physiologic techniques for anastomoses are preferred for long-term survival studies, while the faster techniques are options for short-term survival studies. Each research group must choose techniques according to study defined aims.

Animals↗