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Biomedical subjects

W Brendel

Publications and source records attributed to W Brendel.

At least 37 records · Page 2Linked to original sources
PubMed1989

Myocardial contractility, blood flow, and oxygen consumption in healthy dogs during anesthesia with isoflurane or enflurane.

Left ventricular contractility (Vmax), myocardial blood flow (MBF), and oxygen consumption (O2C) were determined together with systemic hemodynamic parameters in a total of 21 mongrel dogs. Baseline recordings were obtained under basal anesthetic conditions with a narcotic (piritramid, IV). In the control group (n = 7), recordings were obtained during a three-hour observation period with infusion of piritramid. In experimental groups measurements were repeated with equi-anesthetic concentrations of isoflurane (0.7 and 1.4 vol%; n = 8) and enflurane (1.1 and 2.2 vol%; n = 6). Dose-dependent reductions of arterial pressure, cardiac output (CO) and peripheral vascular resistance were observed with isoflurane and enflurane. CO at the higher anesthetic level was depressed significantly more with enflurane. This difference was obviously due to a more severe depression of myocardial contractility with enflurane; Vmax was decreased by 18% and 26% with enflurane, but only by 10% and 17% with isoflurane (P less than 0.01). MBF and the fraction of CO received by the heart were increased above their baseline values with both concentrations of isoflurane. In contrast, the fraction of CO remained constant with enflurane while MBF decreased. O2C was reduced due to decreases of afterload and left ventricular contractility. The reduction was greater with enflurane than with isoflurane. All parameters remained unchanged in the control group. The results of this study indicate that the most striking difference in the actions of isoflurane and enflurane on cardiac parameters is on myocardial vascular resistance; MBF is increased with isoflurane, but is decreased with enflurane although myocardial perfusion pressure is reduced by almost identical amounts.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1989

[Photodynamic laser tumor therapy with a hematoporphyrin derivative in spinocellular carcinoma of the external ear].

Haematoporphyrine-derivative (hpd) selectively photosensitises malignant tumours following intravenous application. 48 hours after injection of hpd an integral laser-light application of the tumour and the surrounding normal tissue was performed. We report on the successful administration of this photodynamic therapy in a patient with a spinocellular carcinoma of the auricle. 16 days after therapy the tumour showed a complete response without damage of the also irradiated surrounding normal tissue. Apart from a temporary sensitivity to light no side effects of the therapy were seen.

Carcinoma, Squamous Cell↗
PubMed1989

[Gd-DTPA-supported magnetic resonance tomographic perfusion follow-up of shockwave-treated tumors].

The signal characteristics of 14 shockwave-treated and 14 solid control tumors were studied before and after injection of Gd-DTPA in an animal model. T1-weighted images of shockwave-treated tumors documented no significant signal intensity increase after contrast media injection in comparison with the untreated control tumors. The reduction of perfusion in shockwave-treated tumors can be documented in vivo by the signal intensity changes of the tumors after contrast media injection.

Animals↗
PubMed1989

Myocardial surface PO2--an indicator of myocardial tissue oxygenation?

The validity of myocardial surface tissue PO2 (PtO2) as a reliable indicator of transmural myocardial tissue oxygenation was studied in six anaesthetised, open chest pigs. Epicardial surface PtO2 was correlated with other variables of myocardial tissue oxygenation such as regional blood flow, coronary venous PO2, O2 saturation, PCO2 and regional myocardial lactate extraction. The study design was based on an experimental model in which the effects of a pacing induced tachycardia on tissue oxygenation of ischaemic and normally supplied myocardium were measured. Two platinum multiwire surface electrodes were placed on the epicardium, on the areas supplied by the left anterior descending coronary artery (LAD) and the left circumflex coronary artery (CX). The LAD was constricted to reduce mean surface PtO2 in the LAD area to about 50% of its baseline value. This did not affect surface PtO2 in the CX area. The reduction of surface PtO2 in the LAD area was associated with decreases in coronary venous PO2 and O2 saturation and with increases in coronary venous lactate and PCO2. Subendocardial regional blood flow and the subendocardial to subepicardial flow ratio were significantly lower than in the CX area. Increasing the heart rate by pacing (+45 beats.min-1) led to an increased degree of ischaemia as shown by fall in surface PtO2 in the LAD area to values around zero kPa, by marked increase in coronary venous lactate and PCO2, by reduction in total (-10%) and subendocardial (-40%) LAD flow and by deterioration of the subendocardial to subepicardial flow ratio. The increased degree of ischaemia was not accompanied by an increase in O2 extraction. The marked decrease in surface PtO2 occurred in spite of a slight increase in the subepicardial regional blood flow (+10%); thus the increase in O2 delivery was not sufficient to meet the increase in O2 demand. Total flow was increased by 27% in the CX area without changes in the subendocardial to subepicardial flow ratio and in the surface PtO2 values. When pacing was stopped, surface values of PtO2 in the LAD area returned to prepacing values, as did lactate extraction and coronary venous PCO2. Clear and close relationships with surface PtO2 were found for regional lactate extraction, coronary venous PCO2 and the normalised subendocardial RBF. Poor or no correlations were found for the normalised subepicardial regional blood flow, the coronary venous O2 saturation and the absolute values of subendocardial and subepicardial regional blood flow.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1989

Regional blood flow and tissue oxygen pressures of the collateral-dependent myocardium during isoflurane anesthesia in dogs.

The authors investigated the effects of isoflurane on blood flow and tissue oxygen pressures of a collateral-dependent myocardium. Seventeen dogs divided into two groups were studied 3-4 weeks after implantation of ameroid coronary artery constrictors to completely occlude the proximal part of the left anterior descending artery. Experiments were performed during anesthesia with an opiate that was infused intravenously throughout the experiments. In Group 1 (n = 9), measurements were obtained during control and during isoflurane- (1.6-2.2 vol%) induced hypotension (mean arterial pressure, 60 mmHg). In Group 2 (n = 8), the identical protocol was applied, but norepinephrine was infused to maintain normotension. Dipyridamole effects were studied in five animals of Group 2 after a second control period at least 1 h after discontinuation of isoflurane. Isoflurane-induced hypotension caused reductions of blood flow and surface tissue oxygen pressures in the collateral flow-dependent area. Vasodilation in the normal left ventricular areas was demonstrated by an unchanged blood flow despite a reduced oxygen consumption and by a significantly increased coronary sinus hemoglobin oxygen saturation. When arterial pressure was maintained at its control level by norepinephrine, tissue oxygen pressures remained constant and collateral as well as normal area flow increased significantly during isoflurane. Coronary vascular resistance was lower during administration of isoflurane and norepinephrine compared with that during isoflurane induced hypotension, suggesting a significant contribution of tissue oxygen demand in regulation of coronary vascular resistance. At comparable levels of arterial pressure and left ventricular oxygen consumption, normal zone blood flow was significantly higher during dipyridamole than during isoflurane and norepinephrine. Thus, isoflurane-induced hypotension decreased blood flow and tissue oxygen pressures of collateral flow-dependent myocardial areas. However, neither isoflurane nor dipyridamole caused such alterations when arterial pressure was normal.

Anesthesia, Intravenous↗
PubMed1989

Release of arachidonic acid metabolites during acute pancreatitis in pigs.

The pancreatic release of arachidonic acid metabolites was studied in a porcine model of acute pancreatitis. In situ isolation of the pancreatic gland enabled selective collection of pancreatic venous blood, pancreatic lymph, and ascites fluid. Three experimental groups were studied: 1) control (n = 9); 2) hemorrhagic pancreatitis induced by injection of 5% bile salt (sodium taurocholate) into the pancreatic duct (n = 10); and 3) edematous pancreatitis induced by injection of free fatty acid (FFA) into the pancreatic artery (n = 10). Determinations of cyclooxygenase metabolites were performed by radioimmunoassay; lipoxygenase metabolites (LTC4, LTD4) were measured by radioimmunoassay after purification by high-performance liquid chromatography. Prostaglandin (PG)F1 alpha, thromboxane B2, and PGF2 alpha concentrations were almost doubled in the lymph of the FFA group during pancreatitis, as were PGF1 alpha levels in pancreatic venous blood. However, concentrations of cyclooxygenase metabolites remained unchanged in the control group and in the bile salt group. Concentrations of LTC4 and LTD4 in lymph and ascites fluid of both pancreatitis groups increased from about 50 pg/ml to a mean level of 600 pg/ml at 6 h. Leukotriene concentrations in the control group were consistently below 50 pg/ml. The results of this study indicate that above all LTC4 and LTD4 are released from the organ and that these arachidonic acid metabolites may be also involved in the events following acute pancreatitis contributing to the systemic effects of the disease.

Acute Disease↗
PubMed1989

Thromboxane mediation of pulmonary hemodynamic responses after neutralization of heparin by protamine in pigs.

Protamine neutralization of heparin is often associated with severe hemodynamic side-effects, including pulmonary hypertension and systemic hypotension. Because prostanoids may be involved, the authors studied the role of arachidonic acid metabolites, especially thromboxane A2, in this process. During anesthesia with enflurane and fentanyl, four groups of pigs were studied: Group 1 (n = 10) received heparin (250 IU/kg), followed by protamine (100 mg) after 15 minutes to neutralize the heparin. The same protocol was used in group 2 (n = 11), except that the thromboxane A2 receptor antagonist BM 13.177 (10 mg/kg) was infused 5 minutes before the protamine. The protocol for group 1 was also used for group 3 (n = 7) except that these animals were pretreated with indomethacin (10 mg/kg). Animals in group 4 (n = 10) were given protamine only (100 mg). Pulmonary artery pressure and pulmonary vascular resistance increased significantly in group 1 after protamine neutralization of heparin. This was accompanied by significant increases in plasma concentrations of the cyclooxygenase products thromboxane B2, 6-keto-prostaglandin F1 alpha, and prostaglandin F2 alpha. Cyclooxygenase products increased to comparable degrees in group 2, but without hemodynamic effects. Leukocyte counts decreased comparably in both groups. Hemodynamic reactions, as well as changes in plasma prostanoid levels were absent in group 3, and group 4, but leukocyte counts were less affected in animals that received protamine alone. The results indicate that the hemodynamic side-effects of protamine are mediated by prostanoids and that thromboxane A2 release is the pivotal step, because side effects were effectively prevented by pretreatment with a thromboxane receptor antagonist.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Left ventricular oxygen tensions in dogs during coronary vasodilation by enflurane, isoflurane and dipyridamole.

The purpose of this study was to investigate the effects of the anesthetics enflurane and isoflurane and of the coronary vasodilator dipyridamole on myocardial oxygen balance and myocardial tissue oxygen tensions. The studies were performed in 24 open-chest dogs during basal anesthesia with a narcotic. Myocardial blood flow (MBF) was measured using radioactive microspheres, myocardial surface tissue PO2 by means of a platinum multiwire surface electrode. One control group and three experimental groups were studied: enflurane (1.1 vol%), isoflurane (0.7 vol%, both end-tidal concentrations), and dipyridamole (0.4 mg/kg). Mean arterial pressure significantly decreased to an average of 70 mm Hg in all three experimental groups. Although MBF was unchanged during enflurane (-18%) and isoflurane (+20%), it increased during dipyridamole (+304% p less than 0.05 vs baseline and control, enflurane, and isoflurane groups). Myocardial oxygen consumption decreased significantly during enflurane and isoflurane but remained unchanged during dipyridamole. Thus, the ratio between myocardial oxygen delivery and consumption increased 6% with enflurane (p less than 0.05 vs baseline), 47% with isoflurane (p less than 0.05 vs baseline and control group) and 280% with dipyridamole (p less than 0.05 vs baseline and control, enflurane, and isoflurane groups). Coronary venous PO2 remained unchanged during enflurane but increased significantly during isoflurane and dipyridamole. Left ventricular surface tissue PO2 was unchanged in enflurane and isoflurane animals and decreased slightly, yet significantly, during dipyridamole. All variables remained unchanged in the control group. Thus, isoflurane and dipyridamole interfered with MBF autoregulation and increased myocardial oxygen delivery out of proportion to myocardial demands.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Shock-wave lithotripsy of gallbladder stones. The first 175 patients.

To substantiate the early results of extracorporeal shock-wave fragmentation of gallstones, we used this nonsurgical procedure to treat 175 patients with radiolucent gallbladder calculi. Chenodeoxycholic acid and ursodeoxycholic acid were administered as adjuvant litholytic therapy. The gallstones disintegrated in all patients except one and completely disappeared in 30 percent of all patients within 2 months after lithotripsy, in 48 percent at 2 to 4 months, in 63 percent at 4 to 8 months, in 78 percent at 8 to 12 months, and in 91 percent at 12 to 18 months. In patients with solitary stones up to 20 mm in diameter, the corresponding values were 45, 69, 78, 86, and 95 percent, respectively. Shock-wave therapy had no adverse effects except cutaneous petechiae (14 percent) and transient gross hematuria (3 percent). One third of the patients had one or more episodes of biliary colic before all the fragments disappeared. Two patients had mild pancreatitis, which necessitated endoscopic sphincterotomy in one. The patient with insufficient stone fragmentation underwent elective cholecystectomy; no additional operations were necessary. Extracorporeal shock-wave lithotripsy combined with medical therapy for stone dissolution is a safe and effective treatment in selected patients with radiolucent gallbladder calculi.

Adolescent↗
PubMed1988

Biliary stones: treatment by shock-wave lithotripsy.

Extracorporeal shock-wave lithotripsy has been introduced as a novel nonsurgical therapy for gallstone disease. To substantiate the initial results, more than 400 patients with biliary calculi have been treated. In selected patients with gallbladder stones, complete clearance of all stone fragments can be expected within 1 year in about 80%. In patients with bile-duct stones not amenable to endoscopic measures, sufficient stone fragmentation by extracorporeal shock waves was achieved in about 80%. Extracorporeal shock-wave lithotripsy is a safe and efficient therapy for selected patients with gallbladder calculi. For patients with bile-duct stones not amenable to endoscopic measures it offers a nonsurgical alternative.

Chenodeoxycholic Acid↗
PubMed1988

Biological effects of shock waves: kidney haemorrhage by shock waves in dogs--administration rate dependence.

The effect of shock waves on normal canine kidneys was examined in two groups of dogs whose right kidneys were exposed to 3000 shock waves generated with 20 kV and 40 nF in a Dornier HM II lithotripter. The groups differed only in the rate of shock wave administration which was 100 and 1 per second, respectively. Autopsy was performed 24 to 30 h later. Macroscopically and histologically, significantly more haemorrhages occurred in the kidney parenchyma if shock waves were administered at a rate of 100 waves per second. Haemorrhages were diffuse, the outer medulla was most heavily affected. The results show that kidney damage is dependent on the rate of shock wave administration. They argue against a direct shock wave effect and favor cavitation as the mechanism of shock wave damage although thermal effects cannot be excluded.

Animals↗
PubMed1988

Biological effects of shock waves: kidney damage by shock waves in dogs--dose dependence.

The effect of shock waves on normal canine kidneys was examined in three groups of dogs whose right kidneys were exposed to 500, 1500, or 3000 shock waves. Autopsy was performed 24-30 h later. The kidneys were enlarged with haemorrhages in the outer and inner renal capsule and intraparenchymally. Macroscopically intraparenchymal haemorrhages were restricted to the high pressure field of the shock wave and consisted of haematomas up to 18 mm diameter (most frequently 6 mm or less) and diffuse haemorrhages. Histologically, haemorrhages were shown to originate from interlobular and arcuate veins. Venous thrombosis, tubular dilatation, and diffuse interstitial haemorrhage occurred in the same area. The number of haematomas was larger, and diffuse haemorrhages were more extended after the application of 1500 and 3000 than after 500 shock waves. No difference was seen between 1500 and 3000 shock waves.

Animals↗
PubMed1988

Splanchnic oxygen consumption and hepatic surface oxygen tensions during isoflurane anesthesia.

Blood flow to and oxygen consumption of the splanchnic organs were determined together with hepatic surface oxygen tensions in 18 mongrel dogs anesthetized with the long-acting narcotic piritramid. Twelve animals also received 0.7 Vol% and 1.4 Vol% isoflurane; six time-related controls received piritramid only. Surgical preparation consisted of a left thoracotomy for inserting a catheter into the left atrium for microsphere injections and for gaining access to the hepatic surface through an incision in the diaphragm. Parameters in the animals receiving isoflurane were recorded at three stages: stage 1--piritramid anesthesia after surgical preparation; stage 2-60 min after addition of 0.7 Vol% (end-expiratory) isoflurane; stage 3-60 min after addition of 1.4 Vol% (end-expiratory) isoflurane. Hepatic surface oxygen tension was determined at each stage using an eight-channel oxygen sensitive electrode. Mean arterial pressure and cardiac output decreased during both stages with isoflurane; hepatic arterial inflow remained constant. Portal blood flow and, hence, total hepatic inflow decreased significantly. An unchanged splanchnic O2 consumption induced lower hepatic venous pO2 values: 40 +/- 1 mmHg at control, 35 +/- 2 mmHg, and 31 +/- 2 mmHg (mean +/- SEM; both P less than 0.05) during isoflurane. A concomitant decrease of hepatic surface pO2 values indicated an altered tissue oxygenation. The percentage of hepatic surface pO2 values in the lowest pO2 range (0-5 mmHg) increased significantly from 8.4 to 20.3% during 1.4 Vol% isoflurane; the percentage of values of 0 mmHg increased from 2.4 to 9.8% during 1.4 Vol.%. No changes of these parameters were detected in the control animals during the 3-h observation period.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

A retrospective analysis of 3 year's experience of an interdisciplinary approach to gallstone disease including shock-waves.

1206 patients with gallstone disease were treated between January 1985 and December 1987, using an interdisciplinary concept that included surgery, endoscopic sphincterotomy, and extracorporeal shock-wave lithotripsy (ESWL). Twenty-five per cent of the patients who were admitted for gallbladder stones were treated by ESWL, whereas 75% underwent surgery. Mortality of elective treatment for gallbladder stones amounted to 0.25% (0.4% in surgery, 0% in ESWL). Postoperative complication rate was low (4.2% in surgery, 7.0% in ESWL). After ESWL treatment, 80% of the patients were free of stones after a follow-up period of 1 year. Recurrence rate in these patients amounted up to 10%; in seven of 70 patients, mean follow-up period was 6 months after complete disappearance of stones. Twenty-seven per cent of all patients who were admitted for bile duct stones underwent surgery, whereas in the other 73%, calculi were removed via endoscopy. ESWL treatment was used additionally, if necessary. Fragments were left behind in three of 75 patients (4.0%) after surgical treatment, and in 7 of 200 patients (3.5%) after endoscopic and ESWL treatment, respectively. In the latter group, three patients (1.5%) required an additional operation. There were no deaths in either of the groups. The use of ESWL for treatment of gallbladder stones needs to be evaluated in long-term follow-up studies. Thus far, surgery remains the dominating method. Endoscopic procedures, eventually combined with ESWL, represent the preferred treatment for patients with bile duct stones.

Aged↗
PubMed1988

Application of a fibrinogen-thrombin-collagen-based hemostyptic agent in experimental injuries of liver and spleen.

FTCH is a recently developed material which consists of a collagen fleece containing fibrinogen, thrombin, and aprotinin integrated into its surface. FTCH is highly effective in sealing of tissues and in establishing hemostasis. We evaluated FTCH in experimentally produced liver (n = 6) and splenic (n = 12) injuries in 18 adult mongrel dogs. The stability of the parenchymal seal of the splenic injuries was tested by splenic tissue pressure elevation after temporary ligation of the splenic vein. No breakthrough bleeding occurred up to a parenchymal pressure of 16.3 +/- 5 mm Hg. Complete hemostasis was easily achieved in all animals before closure. When the dogs were re-explored postoperatively at intervals of either 14 or 30 days, there was no gross evidence of recurrent bleeding. Histologic examinations demonstrated a partially regenerated capsule covering an unspecific fibrovascular granulation tissue and progressive resorption of FTCH without significant inflammatory response. We conclude the following: FTCH provides adequate hemostatic control of experimental liver and splenic injuries. FTCH has excellent tissue compatibility and can be applied easily and safely to hemorrhaging parenchymal wounds. It will not replace adequate surgical techniques, but could be useful as a quickly available and easily applicable hemostatic means in diffuse or acute bleeding of liver and spleen.

Animals↗