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Results for “tissue perfusion”

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At least 19 recordsLinked to original sources
PubMed1979

Tissue perfusion inhomogeneity during early tumor growth in rats.

Tissue perfusion in BA 1112 sarcomas of WAG inbred Rijswijk rats was determined from in vivo measurements of capillary density, length, and erythrocyte velocity in modified Algire chamber preparations. Studies were done with the use of television techniques in situ during a period of 26 days, both in control chambers and after implantation of a 0.1-mm3 piece of tumor tissue. Perfusion in control areas void of tumor tissue. Perfusion in control areas void of tumor was approximately 8-10 ml/minute/100 g of tissue. Flow in active tumor growth regions on the outward side of the tumor edge was through undifferentiated channels and had characteristics of flow through a porous medium. Despite enhanced arterial supply, the stabilized tumor microcirculation at the inward side of the growing tumor retained its perfusion rate constant (15-18 ml/min/100 g). Perfusion in central portions of the tumor was about 2-4 ml/minute/100 g during 12 days, whereas the tumor doubled in diameter. Our findings support the concept of temporal and functional blood flow inhomogeneity in the microcirculation of spreading tumors.

Animals↗
PubMed1992

Influence of desflurane, isoflurane and halothane on regional tissue perfusion in dogs.

The actions of desflurane, isoflurane and halothane on regional tissue perfusion were studied using radioactive microspheres in dogs chronically instrumented for measurement of arterial and left ventricular pressure, global (left ventricular dP/dtmax) and regional (percent segment shortening) contractile function, and diastolic coronary blood flow velocity. Systemic and coronary haemodynamics and regional tissue perfusion were measured in the conscious state and during anaesthesia with equihypotensive concentrations of desflurane, isoflurane, and halothane. All three volatile anaesthetics (P < 0.05) increased heart rate and decreased mean arterial pressure, left ventricular systolic pressure, and left ventricular dP/dtmax Myocardial perfusion was unchanged in subendocardial midmyocardial, and subepicardial regions by the administration of either dose of desflurane. No redistribution of intramyocardial blood flow (endo/epi ratio) was observed during desflurane anaesthesia. Although regional myocardial perfusion was reduced (P < 0.05) in a dose-related fashion by halothane and by isoflurane at high concentrations, redistribution of intramyocardial blood flow was not observed during halothane or isoflurane anaesthesia. All three volatile anaesthetics reduced blood flow to the renal cortex, but only desflurane produced a decrease in renal cortical vascular resistance. Hepatic blood flow decreased in response to halothane but not desflurane or isoflurane. Concomitant decreases in hepatic resistance were observed during administration of desflurane and isoflurane. Dose-related decreases in intestinal and skeletal muscle blood flow were observed during halothane and isoflurane but not desflurane anaesthesia. The results suggest that desflurane maintains myocardial, hepatic, intestinal, and skeletal muscle blood flow while halothane and isoflurane decrease regional tissue perfusion in these vascular beds to varying degrees during systemic hypotension in the chronically instrumented dog.

Anesthetics↗
PubMed1992

The influence of different levels of PEEP on peripheral tissue perfusion measured by subcutaneous and transcutaneous oxygen tension.

OBJECTIVE: To compare subcutaneous (PscO2) and transcutaneous (PtcO2) oxygen tension measurements in relation to hemodynamic variables at different levels of PEEP, and to evaluate the usefulness of these measurements as monitors of peripheral tissue perfusion. DESIGN: Prospective trial. SETTING: Intensive care unit in a university hospital. PATIENTS: Seven patients with gastric cancer who where undergoing total gastrectomy. INTERVENTIONS: Silicone catheter was placed in the upper arm and transcutaneous oxygen monitor was placed on the upper part of the chest. A pulmonary artery catheter was placed in the right pulmonary artery. MEASUREMENTS AND RESULTS: PscO2 and PtcO2 together with hemodynamic variables were measured at different levels of PEEP. Progressive increase of PEEP reduced cardiac index (CI) (p < 0.05) with a concomitant decrease of PscO2 (p < 0.05) and oxygen delivery (DO2) (p < 0.05). Changes in PtcO2 paralleled changes in arterial oxygen tension (PaO2), but no correlation was found between PtcO2, CI and DO2. CONCLUSION: PscO2 is a sensitive indicator of subcutaneous tissue perfusion, which can be used to identify the PEEP level, with optimum peripheral perfusion. PscO2 seems to be a more reliable indicator of tissue perfusion than PtcO2.

Aged↗
PubMedDate not supplied

Observations of thermal gradients in perfused tissues during water bath heating.

Actual thermal gradients in perfused tissues are difficult to observe using thermocouples because of thermal conduction along the probes. We have used fine type-K (chromel-alumel) probes, which have a much lower thermal conductivity than equivalent-sized type-T (copper-constantan) thermocouples, to examine thermal gradients in two mouse tumour systems during water bath heating. The results indicate substantial heterogeneity in temperature distribution even in tumours transplanted in the foot and immersed to a depth of 2 cm in a 44 degrees C water bath for 20 min, i.e. thermal gradients greater than 1 degree C/mm were observed in KHT fibrosarcomas. The temperature heterogeneity for water bath heating is primarily a result of blood flow and appears to be tumour-specific. Temperature measurements using an excised perfused canine kidney demonstrate that increased perfusate volume flow increases the range of tissue temperatures. Consistent with theory, an artifactual improvement in temperature homogeneity resulted when temperature was measured using type-T thermocouples instead of type-K probes. These results emphasize the difficulties in obtaining accurate temperature measurements during experimental and clinical hyperthermia. Even extensive measurements of temperature in tissues may underestimate the true range of heterogeneity unless factors such as thermal smearing are controlled.

Animals↗
PubMedDate not supplied

Skeletal muscle PO2: indicator of peripheral tissue perfusion in haemorrhagic shock.

The following conclusions can be made on the basis of this work: 1) Measurements of skeletal muscle oxygen tension provide an excellent index of tissue perfusion in haemorrhagic shock. 2) Correction of cardiac output and arterial blood oxygen tension in haemorrhagic shock does not necessarily ensure normal tissue oxygenation. 3) In haemorrhagic shock adequate replacement of blood loss using a balanced salt solution in addition to blood replacement is an integral part of the fluid management. 4) Correction of hypovolemia with an equivalent volume of a plasma expander and subsequent reinfusion of shed blood also returns tissue perfusion to normal. However, this treatment results in marked haemodilution and correction of extracellular fluid loss remains inadequate.

Abdominal Muscles↗
PubMedDate not supplied

[Correction of disorders of tissue perfusion in surgical patients in critical conditions and their evaluation by changes in the indices of the acid-soluble fractions of blood plasma].

Rheopolyglucin infusion and vasodilation therapy with droperidol have been performed in 16 critically ill surgical patients with low O2 tissue utilization with the aim in view to assess tissue perfusion disturbances and normalize peripheral blood flow. Basic central hemodynamic parameters and oxygen transport system parameters have been determined. Using gel filtration, acid-soluble blood plasma fractions have been studied spectrophotometrically. Despite the fact that rheopolyglucin infusion caused an increase in oxygen flow index (OFI) at the expense of cardiac index (CI) growth, O2 extraction remained practically unchanged. Vasodilation therapy, with slight changes of CI and OFI, caused an increase in O2 consumption and arterio venous difference, as well as a reduction of mixed venous blood pO2, this accompanied by an increase in acid-soluble blood plasma fractions, especially second fraction at 255 nm. A direct correlation has been established between basic oxygen transport system parameters, characterizing O2 tissue utilization and changes of acid-soluble blood plasma fractions parameters. The changes in acid-soluble blood plasma fractions parameters may serve one of the criteria characterizing the efficacy of procedures aimed at the improvement of tissue perfusion.

Adult↗
PubMed1992

Arterial pH and carbon dioxide tension as indicators of tissue perfusion during cardiac arrest in a canine model.

BACKGROUND AND METHODS: Previous studies have shown that Paco2 and end-tidal CO2 reflect coronary artery perfusion pressures during cardiac arrest. We investigated the relationship of coronary artery perfusion pressure to central arterial pH and Paco2 values during resuscitation from cardiac arrest in a canine model. Twenty-four mongrel dogs were block randomized to three different resuscitation groups after induction of ventricular fibrillation and cardiac arrest: a) standard cardiopulmonary resuscitation (CPR) and advanced life support (n = 8); b) cardiopulmonary bypass (n = 8); or c) open-chest CPR (n = 8). Central arterial blood gases and perfusion pressures were monitored during cardiac arrest and during resuscitation. RESULTS: Prearrest blood gases and hemodynamic values were similar between groups. Sixteen dogs from all three groups were successfully resuscitated. Survivors had significantly higher coronary artery perfusion pressure (p = .03), Paco2 (p = .015), and lower pH (p = .01) values than nonsurvivors. There was no correlation of pH and Paco2 during mechanical external CPR. However, after institution of the different resuscitation techniques, pH and Paco2 each showed a statistically significant correlation (r2 = .50 and .33, respectively) with coronary artery perfusion pressure. CONCLUSIONS: Central arterial pH and Paco2 monitoring during cardiac arrest may reflect the adequacy of tissue perfusion during resuscitation and may predict resuscitation outcome from ventricular fibrillation.

Animals↗
PubMed1978

Dexamethasone treatment during hemorrhagic shock: blood pressure, tissue perfusion, and plasma enzymes.

In a study to determine beneficial effects of dexamethazone (5 mg/kg) during hemorrhagic shock, perfusion (as measured by radioactive microspheres) and plasma enzymes were measured. Hemorrhagic shock (mean arterial blood pressure, MABP, of 50 mm of Hg) was induced in dogs and then the dogs were isolated from the shed-blood reservoir and were allowed to compensate their MABP. Hemodynamic changes, tissue perfusion, and plasma enzymes were measured at different intervals of time in nontreated and dexamethasone-treated dogs. Beneficial effects were increased MABP, improved blood flow to the lungs, gastrointestinal tract, and kidneys, and less cell damage as indicated by amounts of plasma enzymes released from damaged tissues. These effects favor the maintenance of the homeostatic state and, in turn, a greater chance for survival of the dog.

Alanine Transaminase↗
PubMed1979

Tissue perfusion rate determined from the decay of oxygen-15 activity after photon activation in situ.

Rates of cerebral perfusion were obtained from measurements of the disappearance (wash-out) of oxygen-15 after in situ tissue activation with 45-million-volt x-rays. In an anesthetized cat, typical values were 90 milliliters per minute per 100 grams of tissue, with 55 percent wash-out. In a specific radiotherapy patient, the value was 65 milliliters per minute per 100 grams of tissue, with 63 percent wash-out of oxygen-15 through incorporation into tissue water.

Animals↗
PubMed1992

Analysis of oxygen exchange between arterioles and surrounding capillary-perfused tissue.

A theoretical model is used to analyze oxygen transport in a three-dimensional tissue region containing an arteriole surrounded by an array of capillaries in planes perpendicular to the arteriole. Convective removal of oxygen from the vicinity of the arteriole by nearby capillaries is shown to increase diffusive oxygen loss from the arteriole. This effect depends on the locations of the capillaries, particularly those nearest to the arteriole. The arteriolar oxygen efflux is comparable to that predicted by a previous model which used a continuum approach, but the efflux does not increase with increasing perfusion as rapidly as predicted by the continuum model. Even a small capillary flow rate strongly influences the oxygen field surrounding the arteriole.

Arterioles↗
PubMed1992

Effect of tissue perfusion and oxygenation on accumulation of collagen in healing wounds. Randomized study in patients after major abdominal operations.

OBJECTIVE: To compare the accumulation of collagen in standardised wounds in patients who had abdominal operations and whose postoperative fluid replacement was decided either clinically or by measurements of subcutaneous oxygen tension (PscO2). DESIGN: Prospective randomised trial. SETTING: University Hospital. SUBJECTS: Twenty-nine patients with cancer or inflammatory bowel disease who were undergoing abdominal operations. INTERVENTIONS: Silicone rubber catheter placed in the upper arm to measure PscO2. Two tubes of expanded polytetrafluoroethylene (ePTFE) implanted subcutaneously parallel to the silicone rubber catheter to measure the amount of collagen accumulated. MAIN OUTCOME MEASURES: Amount of postoperative fluid replacement required in each group, and measurements of hydroxyproline/cm of the ePTFE tubes. RESULTS: The group treated according to PscO2 measurements received more fluid on the day of operation than the group treated according to clinical criteria (p < 0.05). They had accumulated more collagen in their ePTFE tubes by day 7 (p < 0.05). CONCLUSION: Replacement of fluid according to measurements of PscO2 rather than by clinical criteria results in improved accumulation of collagen in healing wounds.

Adult↗
PubMed1992

Optimization of the blood for oxygen transport and tissue perfusion in critical care.

In present practice, patients in intensive care are managed with subnormal haematocrit values and oligovolaemia. Optimization of the blood for oxygen transport in preterm infants in intensive care yields major benefits in their prognosis. A rational basis is described for this optimization in terms of the circulating blood volume and haematocrit, represented by circulating red cell volume (mass). Extrapolation of these lessons in haematological management is proposed for adult patients in critical care, so as to reduce dependence on respiratory support and minimize clinical complications and costs.

Adult↗