Biomedical subjects

K Messmer

Publications and source records attributed to K Messmer.

At least 199 records · Page 11Linked to original sources

PubMed1996

Time discrete, near infrared photoplethysmography (NIRP) for non-invasive investigation of the volume pulse in man.

UNLABELLED: In pulse oximetry the principles of photoplethysmography are used for determination of heart rate and in some devices to also display the volume pulse. It has been suggested, that a more detailed analysis of the signal may allow quantitative analysis of peripheral hemodynamic events. We describe a new computer assisted time discrete analysis of the volume pulse, studying its reliability and the method s fundamental assumption of a linear relationship between changes in amplitude and changes in time sequences of the volume pulse. METHOD: In a finger clip two diodes emit near infrared (840 nm, NIR) and red light (640nm, RED) into the finger tip, where it is remitted mainly by the erythrocytes. 70 sec of recorded signal is filtered and the resulting volume pulse analysed off-line using a computer. On each volume pulse the time of the first (Tmax), the second maximum (time of dicrote, Td) and the duration of the volume pulse (Tp) are measured and the mean values displayed. In addition, the fundamental arterial oscillation Tag = Td - Tmax and all the above values in relation to Tp are calculated. Using NIRP, 54 healthy young volunteers (19 female, mean age 27.0 +/- 3.4 years) were studied and the individual mean values calculated from 960 measurements. The reliability during 10 repetitive measurements was investigated in 26 of the 54 volunteers. In 12 subjects 5 repetitive measurements were obtained from each finger and compared with each other. In 11 subjects the linear relationship between amplitude and time sequence was tested on > 30 000 single volume pulses. The finger clip photoelectrode was levelled with the right atrium in all measurements, skin close to the clip and room temperature were recorded. RESULTS: From the mean individual values the following time discrete values were calculated for the NIR signal (n = 41): Tp = 882.3 +/- 142.6 ms, Tmax = 214.8 +/- 28.3 ms, Td = 452.7 +/- 32.4 ms, Tdec = 667.4 +/- 133.6 ms, Tag = 237.9 +/- 36.3 ms, Tmax/Tdec = 0.34 +/- 0. 07, Td/Tdec = 0.7 +/- 0.11. For each parameter the individual standard deviation during 10 repetitive measurements (26 subjects) ranged between 2.2 and 6.1%. The time sequences found were not significantly different between the individual fingers. A linear relationship between changes in time sequence and changes in amplitude was found in all tested subjects (mean r = 0.96). CONCLUSION: These results show, that the values obtained with time discrete NIRP are highly reproducible and show an individual SD of less than 6.5% under steady state conditions. The linear relationship between time sequence and amplitude found in the present study has to be confirmed in further studies on patients with pathologies of the macro- and microcirculation.

Adult↗

PubMed1996

Assessment of splanchnic tissue oxygenation by gastric tonometry in patients undergoing laparoscopic and open cholecystectomy.

This experimental study compared the effects of laparoscopic (n = 31) and open (n = 32) cholecystectomy on gastric intramucosal pH (pHi). For this purpose, pHi was measured tonometrically before induction of anaesthesia, at 30-min intervals during surgery, and 1, 2 and 4 h after operation in otherwise healthy patients undergoing elective cholecystectomy. Additionally, perioperative arterial pH (pHa), arterial carbon dioxide tension (PaCO2), intramucosal carbon dioxide tension, arterial bicarbonate concentration, end-tidal carbon dioxide pressure (PECO2), levels of serum lactate, lactate dehydrogenase (LDH) and gamma-glutamyl transferase (GGT), haematocrit and arterial blood pressure were recorded. In the two groups no significantly different changes occurred in pHi, pHa, serum lactate concentration or haematocrit at any of the observation times. PECO2 and PaCO2 were significantly raised during the laparoscopic procedure, whereas levels of LDH and GGT and arterial blood pressure rose during and after open cholecystectomy. In spite of the increased intra-abdominal pressure and the peritoneal carbon dioxide absorption related to the creation of a pneumoperitoneum, no decrease in pHi was detectable during laparoscopic cholecystectomy.

Adult↗

PubMed1996

Exogenous bradykinin enhances ischemia/reperfusion injury of pancreas in rats.

We have investigated the effect of bradykinin on microvascular perfusion failure and enzyme release after ischemia/reperfusion of the pancreas in rats. Using intravital fluorescence microscopy in 21 anesthetized Sprague-Dawley rats, quantitative analysis of the microcirculation, including functional capillary density (FCD) and leukocyte-endothelium interaction, was performed in an ischemia/reperfusion model of the pancreas. Bradykinin was dissolved in phosphate buffer and given as a bolus injection (injection group, 10 microgram/kg body wt i.a.; n = 7) or continuously infused (infusion group, 125 microgram/kg body wt/hr i.a.; n = 7) 15 min before the end of 2 hr of ischemia. Two further groups underwent sham operation (control group, n = 7) or an ischemia of 2 hr (ischemia group, n = 7) without bradykinin administration. Continuous infusion of bradykinin resulted in a significant enhancement of capillary perfusion failure after ischemia during reperfusion. In the bradykinin infusion group less than 25% of the capillaries were perfused (FCD 98 +/- 9 cm -1) after 2 hr of reperfusion, whereas in the ischemia group without bradykinin, 50% of capillaries were perfused (FCD 192 +/- 11 cm -1). Both of these values are significantly different from the baseline value of the control group (408 +/- 9 cm -1). The rise in pancreas amylase concentration was significantly more pronounced in the infusion group (basal: 1812 +/- 114 U/1; 2 hr of reperfusion 3375 +/- 268 U/1) when compared to the ischemia group (basal: 2386 +/- 283 U/1; 2 hr of reperfusion 3486 +/- 268 U/1). These findings suggest that bradykinin has an additive role in aggravation of pancreatic microcirculatory failure after ischemia/reperfusion of the pancreas.

Amino Acid Sequence↗

PubMed1996

Determinants of pancreatic microcirculation in acute pancreatitis in rats.

The aim of the study was to evaluate the effects of arterial hypotension, high-volume crystalloid resuscitation, and isovolemic hemodilution on pancreatic microvascular perfusion during acute pancreatitis. Using intravital microscopy, pancreatic functional capillary density was analyzed in rats 1 and 2 hr after onset of acute pancreatitis. Pancreatic microvascular perfusion in acute pancreatitis was characterized by a (-62%) significant reduction of functional capillary density predominantly in perinecrotic but also in nonnecrotic tissue (-43%). Pancreatic microvascular perfusion failure was aggravated by arterial hypotension but attenuated by treatment with high-volume crystalloid resuscitation. Isovolemic hemodilution was found superior to high-volume crystalloid resuscitation in maintaining pancreatic functional capillary density and therefore has the best potential in preserving tissue integrity and thereby limiting progression of disease. This study underlines the importance of early fluid resuscitation/hemodilution in patients presenting with acute pancreatitis.

Acute Disease↗

PubMed1996

Impact of enalapril on microvascular perfusion and leukocyte adherence in a model of rat liver transplantation assessed by in vivo microscopy.

ACE inhibitors have been proven to be effective in the reduction of ischemia/reperfusion damage after myocardial ischemia. In an attempt to investigate this effect in a model of syngeneic liver transplantation in the rat, we compared a control group with an ACE inhibitor treatment group, in which enalapril was given i.v. before and during reperfusion. By means of in vivo microscopy, sinusoidal perfusion rate, permanent leukocyte sticking in sinusoids and postsinusoidal venules, and leukocyte rolling in postsinusoidal venules were assessed. Liver function was evaluated by measuring bile output. The sinusoidal perfusion rate was significantly improved by enalapril treatment. Leukocyte sticking in both sinusoids and postsinusoidal venules was found to be remarkably reduced in enalapril-treated animals; the fraction of rolling leukocytes remained unchanged. Bile output was increased in enalapril-treated animals. These results demonstrated, in a model of rat liver transplantation, that ACE inhibition by enalapril is effective in reducing hepatic ischemia/reperfusion damage as assessed by the leukocyte-endothelium interaction using in vivo microscopy and postreperfusion bile production.

Angiotensin-Converting Enzyme Inhibitors↗

PubMed1996

Intravital studies on beneficial effects of warm Ringer's lactate rinse in liver transplantation.

This quantitative in vivo fluorescence microscopy study investigated the impact of warm versus cold Ringer's lactate (RL) graft rinse on various microvascular manifestations of ischemia-reperfusion injury after liver transplantation in the rat. Syngeneic orthotopic liver transplantation, including arterial revascularization, was performed in male Lewis rats following 24 h of cold storage in University of Wisconsin (UW) solution. In one group (n = 8) liver grafts were rinsed with 4 degrees C (cold) RL, whereas in the other group (n = 8) grafts were rinsed with 37 degrees C (warm) RL immediately prior to revascularization. Hepatic microvascular perfusion, leukocyteendothelium interaction, and Kupffer cell activation were quantified 30-90 min after graft reperfusion by direct visualization with intravital fluorescence microscopy. Moreover, biliary excretory graft function was analyzed by determination of bile flow and bile salt excretion during the first 90 min after reperfusion. Compared to grafts rinsed with cold RL, acinar and sinusoidal perfusion were found to be significantly increased after rinsing the grafts with warm RL. The amount of nonperfused acini declined from 18.1% +/- 4.0% to 7.4% +/- 1.6% (P < 0.05), and the total percentage of perfused sinusoids increased from 80.1 +/- 1.4 to 88.4 +/- 1.2 (P < 0.001) after cold and warm rinse, respectively. After rinsing the graft with warm RL, WBC adherence in sinusoids and especially in postsinusoidal venules decreased significantly by 28% (P < 0.001) and 33% (P < 0.001), respectively. Kupffer cell activation was markedly reduced after rinsing with RL at 37 degrees C, as indicated by a decelerated adherence of latex particles injected 80 min after reperfusion. Excretory graft function was dramatically increased following warm RL rinse during the 90-min observation period. Bile flow was enhanced from 1.04 +/- 0.5 to 3.9 +/- 0.8 ml/100 g liver per 90 min (P < 0.01), with a parallel rise in bile salt excretion from 24.3 +/- 5.8 to 128.0 +/- 19.8 mmol/ 100 g liver per 90 min (P < 0.05) when compared to cold RL. These data strongly suggest that rinsing liver grafts with warm RL prior to reperfusion represents a simple and inexpensive way to reduce the incidence of primary graft failure secondary to ischemia and reperfusion injury in liver transplantation.

Animals↗

PubMed1996

Eight hours' inhalation of prostacyclin (PGI2) in healthy lambs: effects on tracheal, bronchial, and alveolar morphology.

OBJECTIVE: To study potential toxic effects of long-term (8 h) inhaled prostacyclin (PGI2) on respiratory tract tissues. DESIGN: In a prospective, randomized order, either PGI2 (n =7) or normal saline (n = 7) was aerosolized during a time period of 8 h in healthy lambs. SETTING: Institute for Surgical Research of the Ludwig-Maximilians University of Munich. ANIMALS: 14 health, anesthetized, ventilated lambs. INTERVENTIONS: All animals were endotracheally intubated followed by tracheotomy. PGI2 solution or normal saline was administered with a jet nebulizer (delivery rate 4-10 ml/h; mass median diameter of aerosol particles 3.1 microns). MEASUREMENTS AND RESULTS: Histomorphological changes after 8-h inhalation of PGI2 solution were compared to those after 8-h inhalation of normal saline. Tracheal and bronchoalveolar tissues were examined by light and electron microscopy in order to assess tissue damage induced by inhaled PGI2. Pathological changes were ranked by a blinded observer following a graduation system ranging from "absence of pathological changes" to "maximal pathological changes". Abnormalities were restricted to the trachea (focal flattening of the epithelium, loss of cilia, slight inflammatory cell infiltration) and alveolar tissue (focal alveolar septal thickening with slight inflammatory cell infiltration), but no statistically significant differences between the PGI2 and control groups were encountered. CONCLUSION: Our findings indicate the absence of PGI2 aerosol-related respiratory tissue damage after 8-h inhalation of PGI2.

Aerosols↗

PubMed1996

Inhalation of prostacyclin (PGI2) for 8 hours does not produce signs of acute pulmonary toxicity in healthy lambs.

OBJECTIVE: To study the potential side effects and toxicity of inhaling prostacyclin (PGI2) aerosol for 8 h. DESIGN: In a prospective, randomized study 14 healthy lambs received either PGI2 (n = 7) or 0.9% NaCl (n = 7) as an aerosol for 8 h. SETTING: Institute for Surgical Research of the Ludwig-Maximilians-University of Munich. INTERVENTIONS: All animals were studied under general anesthesia in a prone position. They were first intubated endotracheally and later tracheotomized. PGI2 solution (median dose 28 ng/kg per min) or 0.9% NaCl was administered with a jet nebulizer (delivery rate 4-10 ml/h; mass median diameter of aerosol particles 3.1 microns). Bronchoalveolar lavage was performed before and after the inhalation period to collect epithelial lining fluid of alveoli. MEASUREMENTS AND RESULTS: Hemodynamic and respiratory parameters, systemic resorption (plasma levels of 6-keto-prostaglandin-F 1 alpha), in vitro bleeding time, collagen-induced platelet aggregation and global biochemical and cellular composition of the epithelial lining fluid were examined in order to assess the side effects and signs of acute pulmonary toxicity induced by inhaled PGI2. No statistically significant differences were found between the PGI2 and the control groups for any of the parameters examined. CONCLUSION: Inhalation of PGI2 (28 ng/kg per min) over a period of 8 h in healthy lambs does not produce major side effects or acute pulmonary toxicity.

Acute Disease↗

PubMed1996

Hypovolemic shock and cardiac contractility: assessment by end-systolic pressure-volume relations.

The end-systolic pressure-volume relation (ESPVR) is accepted as a load-independent measure of cardiac contractility. Potential curvilinearity of the ESPVR, dependency on coronary perfusion pressure (CPP) and sensitivity to the type of loading intervention might limit its use in hemorrhagic shock. This study compared ESPVRs obtained by caval and aortic occlusion under physiological loading conditions at baseline with those obtained during hemorrhagic shock (mean arterial pressure 45 mmHg). The left ventricular (LV) pressure (tip manometer) and volume (conductance catheter) were measured in ten anesthetized pigs. ESPVRs were fitted to linear and quadratic models. Within end-systolic pressure (Pes) ranges obtained under baseline conditions, ESPVR displayed only minimal curvilinearity (second-order coefficient a < 0.007) and could be accurately described by a linear model. However, nonlinearity of ESPVRs obtained over wider load ranges is suggested by negative volume axis intercepts of the linear model. Steeper ESPVR with aortic than with caval occlusion (2.28 +/- 0.22 vs 3.41 +/- 0.51 mmHg/ml, ns) could not be proven owing to the large interindividual variance of ESPVR slopes with both loading interventions. During shock the Pes range obtained by caval occlusion decreased to very low levels (from 49 +/- 2 to 34 +/- 1 mmHg), ESPVR did not adequately fit either of the two models (mean R < 0.66), and critical reduction of CPP induced negative ESPVR slope in four of ten experiments. In contrast, aortic occlusion at shock resulted in linear ESPVR (R = 0.927 +/- 0.029), Pes ranges (92 +/- 3 to 58 +/- 4 mmHg) comparable to the ones obtained by caval occlusion at control (113 +/- 5 to 73 +/- 6 mmHg), and steeper ESPVR than at control (3.41 +/- 0.51 to 7.38 +/- 1.0 mmHg/ml, P < 0.05). Interpretation of the increased ESPVR slope obtained with aortic occlusion as due to increased contractility in shock is, however, complicated by different Pes ranges. It is concluded that within Pes ranges obtained with caval or aortic occlusion in situ the ESPVR can be adequately fitted to a linear model. For assessment of the inotropic response to shock the ESPVR is of limited value because (1) caval occlusion is not suitable to generate ESPVR during shock, and (2) Pes ranges obtained with identical loading interventions differ greatly between baseline and shock and, therefore, apparent ESPVR changes are influenced by the potential nonlinearity of the ESPVR. Combining caval occlusion at baseline with aortic occlusion at shock would result in comparable Pes ranges. Interpretation of results is, however, complicated by diverging effects of the different loading interventions on the shape and slope of the ESPVR.

Animals↗

PubMed1996

[Prehospital fluid resuscitation].

Trauma and associated major blood losses in Germany represent the leading cause of mortality in patients up to 45 years of age. The endpoints of prehospital fluid resuscitation in traumatic-hemorrhagic shock are the restitution of intravascular volume und cardiac preload, in order to increase cardiac output and thus provide adequate oxygen delivery to the tissues. The key therapeutic factor to prevent the development of multiple organ failure complicating trauma and shock, however, is the normalization not only of macrohemodynamics (systemic blood pressure. cardiac output), but the restitution of the disturbed microvascular perfusion. In case of major blood loss and exsanguination this can not be achieved by crystalloids and synthetic colloids used in conventional volume therapy. A new concept consists of i.v. bolus infusion of a small volume (4 ml/kg body weight) of a hyperosmolar (7.2-7.5%) NaCl/colloid solution, which is termed "Small-volume Resuscitation". Recently presented data from a cohort analysis of 8 preclinical studies show an increase in survival rate by about 5% when compared to standard of care. In addition, artificial oxygen carrying solutions are currently investigated. by which-through an increase of O2-blood content-oxygen delivery to the tissues might be augmented.

Emergency Medical Services↗

PubMed1996

The bradykinin antagonist CP-0597 can limit the progression of postischemic pancreatitis.

Bradykinin mediates the inflammatory process of acute pancreatitis characterized by an increase of microvascular permeability, vasodilation and leukocyte activation. These phenomena are characteristic also for the ischemia/reperfusion injury of the pancreas, which in time is considered a causative factor in the pathogenesis of acute pancreatitis. The aim of this study was to investigate the influence of the bradykinin B2 receptor antagonist CP-0597. After complete ischemia/reperfusion of the pancreas in rats there is progression from postischemic acute edema to necrotizing pancreatitis over a reperfusion period of 5 days. In 8 Sprague-Dawley rats (treatment group) 18 micrograms/kg/h CP-0597 was administered intraperitoneally over 5 days with an osmotic minipump starting 15 min before release of 2 h ischemia. Animals of the placebo group (n = 8) were identically treated, but received the solvent, phosphate buffer. Animals of a control group (n = 7) underwent sham operation without ischemia. After 5 days the animals were sacrificed for histology. No morphological changes of the pancreatic gland were observed in the control group. Ischemia for 2 h resulted in necrotizing pancreatitis with high mortality (4/8 animals) during the reperfusion period of 5 days. In contrast, all animals in the treatment group survived without clinical or histological signs of necrotizing pancreatitis.

Acute Disease↗

PubMed1996

Perisurgical erythropoietin application in anemic patients with colorectal cancer: A double-blind randomized study.

BACKGROUND: Blood transfusions are associated with higher postoperative morbidity and tumor recurrence rates in colorectal cancer surgery, To reduce the need for transfusions in patients with tumor-induced anemia who are not suitable for autologous blood donation, it was tested whether perisurgical erythropoietin application would be able to stimulate hematopoiesis adequately. METHODS: In a double-blind randomized study 150 IU/kg body weight erythropoietin was given subcutaneously every 2 days beginning 10 days before operation and continuing until postoperative day 2. Twenty patients were randomized into the erythropoietin group with three observed dropouts and 10 patients into the placebo group. RESULTS: In the erythropoietin group two episodes of hypertension and one deep venous thrombosis were observed. Preoperative hemoglobin response in the erythropoietin group (p = 0.069) was paralleled by a highly significant reticulocyte increase (p = 0.0004). However, frequency of blood transfusion was not different between both study groups (erythropoietin, 1.82 +/- 0.80 units/ patient; placebo, 1.80 +/- 0.97 units/patient). If iron availability was analyzed, a strong correlation between ferritin blood levels and transferrin iron saturation with hemoglobin response was observed in regression analysis (p < 0.001). CONCLUSIONS: These results indicate that hematopoiesis in anemic patients with colorectal cancer can be stimulated by erythropoietin; however, clinical efficacy is to be expected only in selected patients with high iron availability, which calls for further studies combining erythropoietin and parenteral iron application.

Adult↗

PubMed1996

In vivo assessment of hepatic alterations following gadolinium chloride-induced Kupffer cell blockade.

BACKGROUND/AIMS: In recent years, Gadolinium chloride (GdCl3), a rare earth metal, has frequently been used to study the role and function of Kupffer cells under physiological and pathological conditions. This study was performed to elucidate the consequences of GdCl3-induced Kupffer cell blockade for hepatic microcirculation, hepatocellular function and integrity. METHODS/RESULTS: Using intravital fluorescence microscopy, we studied the hepatic microcirculation of rats pretreated with either GdCl3 (n = 12; 10 mg/kg; 1 ml i.v. for 2 d) or saline (n = 9; 1 ml). The GdCl3-treated animals revealed a significantly lower phagocytic activity of Kupffer cells when compared to controls. Concomitantly, GdCl3-treatment resulted in a pronounced rise of serum cytokine activity (tumor necrosis factor-alpha; interleukin-6). The hepatic microvascular perfusion was characterized by a moderate increase in the number of non-perfused sinusoids accompanied by a reduction of bile flow. In addition, GdCl3-treatment caused a slight increase in liver enzyme activity (< 200 U/l) (aspartate aminotransferase and alanine aminotransferase) with no substantial parenchymal tissue injury (light microscopy). The groups did not differ in concentrations of circulating endotoxin (GdCl3-treatment: 0.044 +/- 0.042 ng/ml; controls: 0.052 +/- 0.014 ng/ml). CONCLUSIONS: We conclude that hepatic alterations following Kupffer cell blockade with GdCl3 may possibly be the consequence of cytokine release as a response to the phagocytic challenge of GdCl3-aggregates. If used for Kupffer cell blockade, the hepatic alterations following GdCl3-treatment described in the present study should be taken into consideration.

Animals↗

PubMed1996

Protective effect of the somatostatin analogue octreotide in ischemia/reperfusion-induced acute pancreatitis in rats.

Somatostatin and its stable analogue octreotide are proposed to ameliorate the outcome from acute pancreatitis by inhibiting pancreatic secretion and preventing cell injury. This study investigated the effect of somatostatin analogue octreotide on pancreatic microcirculatory injury (by means of intravital fluorescence microscopy) and enzyme release after ischemia/reperfusion of the pancreas in rats. Octreotide, injected 15 min before the end of 2 h of ischemia as a bolus injection (50 micrograms kg-1 i.v.) or as a continuous infusion (50 micrograms kg-1 h-1 i.v.), attenuated postischemic reperfusion injury of the pancreas as evidenced by a significant (p < 0.05) improvement in capillary perfusion and decrease in leukocyteendothelium interaction in postcapillary venules compared to ischemia without treatment. Pancreas amylase concentration remained unchanged in the octreotide group but increased significantly (p < 0.05) in the ischemia group. These results indicate a protective effect of octreotide against postischemic reperfusion injury of the pancreas in rats.

Acute Disease↗

PubMed1996

Liver ischemia and reperfusion induces a systemic inflammatory response through Kupffer cell activation.

To study the role of Kupffer cells (KC) as a cellular source of proinflammatory cytokines in hepatic ischemia/reperfusion, Sprague-Dawley rats were subjected to 20 min global hepatic ischemia. Sham-operated animals served as controls. Blood levels of tumor necrosis factor-alpha (TNF-alpha), interleukin-1 alpha (IL-1 alpha), and interleukin 6 (IL-6) were determined after 10, 30, 60, 120, and 240 min of reperfusion and compared with spontaneous cytokine release by KC isolated after 60 min of reperfusion. Hepatic ischemia/reperfusion resulted in an enhanced (p < .01) spontaneous release of TNF-alpha (+482%), IL-1 alpha (+33%), and IL-6 (+175%) by KC. Kinetic analysis of cytokinemia revealed an early increase (p < .01) of TNF-alpha and IL-1 alpha within minutes upon reperfusion, while an elevation of IL-6 serum levels was observed with a delay of 2 h. Early cytokinemia was associated with dysfunction/injury of the liver, lung, and kidney after 4 and 24 h of reperfusion, respectively. These data indicate that hepatic ischemia/reperfusion results in Kupffer cell activation and increased cytokine levels, which may produce systemic inflammation and may be responsible for tissue injury locally and on remote sites.

Animals↗

PubMed1996

Systemic and subcutaneous microvascular Po2 dissociation during 4-h hemorrhagic shock in conscious hamsters.

The relationship between systemic and microvascular Po2 in subcutaneous connective tissue and hemodynamics was investigated during 4-h hemorrhagic shock (40 mmHg) in conscious Syrian hamsters (n = 66) fitted with a dorsal skinfold window. Systemic blood gases, metabolic parameters, arteriolar, venular, and tissue Po2, microvascular red blood cell velocity, and blood flow were evaluated in survivors (S) and nonsurvivors (NS). Surviving animals were resuscitated with shed blood. Microvascular and tissue Po2 were measured by phosphorescence decay of Pd-meso-tetra (4-carboxyphenyl) porphyrin (30 mg/kg body wt iv). Shock caused a significant dissociation between systemic arterial and microvascular arteriolar Po2 levels. Arterial Po2 increased from 59.7 +/- 12.0 to 110.8 +/- 19.7 mmHg (S) and from 64.0 +/- 13.7 to 128.5 +/- 10.1 mmHg (NS), whereas Po2 in large arterioles decreased from 56.9 +/- 5.5 (control) to 29.5 +/- 20.1 (S) and 6.0 +/- 5.7 mmHg (NS). Correspondingly, tissue Po2 fell from 24.1 +/- 6.8 (control) to 0.9 +/- 0.6 (S) and 0.4 +/- 0.3 mmHg (NS). Venous Po2 decreased from 28.8 +/- 3.7 to 20.4 +/- 4.1 (S) and from 28.0 +/- 2.9 to 16.3 +/- 0.5 mmHg (NS). Shock outcome and tissue oxygenation were predicted by arterial blood gases and metabolic and microcirculatory conditions but not by central venous Po2.

Animals↗

PubMed1996

Effects of hemodilution on gastric regional perfusion and intramucosal pH.

UNLABELLED: Acute normovolemic hemodilution (ANH) has been shown to be a cost-effective method of reducing allogenic blood transfusion during elective surgery. ANH has been implicated with impaired oxygenation in isolated canine gastric flaps. The present study was designed to investigate the effects of ANH on gastric mucosal oxygenation using a model closely imitating the clinical situation. Sixteen splenectomized anesthetized beagles were isovolemically hemodiluted to a hematocrit of 20 +/- 1% (6% hydroxyethyl starch; mol wt 200,000; substitution ratio 0.45-0.55). Blood volume (indocyanine green), cardiorespiratory parameters, gastric intramucosal pH (pHi), and gastric regional blood flow (radioactive microspheres; 15 microns) were measured before and after ANH. RESULTS: blood volume was unchanged (87 +/- 8 ml/kg before and 88 +/- 7 ml/kg after ANH). Median total gastric mucosal blood flow at baseline was 0.51 +/- 0.35 ml.min-1.g-1 and did not change significantly upon ANH. The mean pHi was 7.29 +/- 0.05 before and 7.28 +/- 0.05 after hemodilution. There was a homogenization of blood flow distribution in gastric mucosa. Severe hemodilution to a hematocrit of 20% does not impair gastric mucosal oxygenation and poses no risk to gastric mucosal integrity.

Animals↗

PubMed1996

Skeletal muscle microvascular and tissue injury after varying durations of ischemia.

The purpose of this study was to examine the effect of varying durations of ischemia on several microvascular parameters in the awake hamster chamber model. The goal was to characterize the microvascular damage that occurs in skeletal muscle as a result of ischemia and reperfusion. The chamber tissues were subjected to 1-5 h of ischemia, and then the following parameters were measured: vessel diameter, endothelial thickness, macromolecular leakage, red blood cell velocity, adherent leukocytes, rolling leukocytes, freely flowing leukocytes, functional capillary density, and propidium iodide-positive cell nuclei. In control animals there was no significant difference in any parameters over the entire observation period. After 1 or 2 h of ischemia an increase in rolling and adherent leukocytes was measured. After 3 h of ischemia there was a significant increase in the mean endothelial thickness and in the number of nonviable cells. After 4 h of ischemia a significant difference in the extent of macromolecular leakage and the functional capillary density was additionally observed. After 5 h of ischemia this damage was more pronounced and often so severe that approximately 50% of the vessels demonstrated no reflow.

Animals↗