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PubMed1983

Use of a transcutaneous PO2 regional perfusion index to quantify tissue perfusion in peripheral vascular disease.

In order to develop transcutaneous oxygen tension (PtcO2) measurements into a practical method for assessing peripheral vascular disease, the relationships between extremity and chest wall PtcO2 were examined in subjects with and without systemic atherosclerotic disease. The ratio of extremity to chest PtcO2, or transcutaneous regional perfusion index (RPI) assessed limb oxygenation more reliably than did direct PtcO2 measurement by obviating the effects of changes in systemic oxygen delivery upon local PtcO2. The authors find that transcutaneous oximetry can be used during treadmill exercise testing and that the RPI is unchanged by exercise in all normal subjects. PtcO2 and RPI were then measured during rest, position change, and exercise testing in patients with intermittent claudication. Whereas normal subjects maintain a constant thigh and calf RPI during exercise, patients with intermittent claudication consistently manifested large decreases in RPI in these areas when they were exercised until symptomatic. The authors find no overlap between the responses of normal subjects and patients with claudication; positive findings are, therefore, highly specific for exercise-induced limb ischemia. Since transcutaneous RPI exercise testing is easily performed and highly reproducible, it is well suited to clinical use in the diagnosis and documentation of intermittent claudication. Furthermore, since limb ischemia can be quantified, this method lends itself both to grading the severity of disease and to evaluating clinical progression of disease. It is suggested that such a quantitative approach to evaluation of intermittent claudication may allow refinement and extension of the indications for operative intervention in patients with intermittent claudication.

Adult↗
PubMed1995

Heterogeneity of myocardial perfusion provides the physiological basis of perfusable tissue index.

UNLABELLED: Assessment of viable from nonviable myocardium is critical for the care of patients being considered for revascularization procedures. Recently, the perfusable tissue index (PTI) has been proposed as an index of myocardial viability. METHODS: Computer simulations were performed for homogeneously and heterogeneously perfused tissue over a wide range of flows (0.04-6.4 ml/g/min) using both bolus and infusion inputs. RESULTS: PTI estimated from simulated homogeneously perfused tissue did reflect the amount of tissue being perfused independent of absolute level of flow, type of input or model configuration, whereas PTI obtained from simulated heterogeneously perfused tissue was consistently lower than the simulated "true" PTI and varied with flow, type of input function and model configuration. Flow estimated with 15O-water was not significantly different from that measured with radio labeled microspheres. CONCLUSION: Oxygen-15-water can diffuse into both acutely and chronically ischemic myocardium irrespective of its functional status. The results suggest that PTI is most likely an index of the heterogeneity of myocardial flow rather than an index of the amount of tissue being perfused. Its utility for delineating myocardial viability is thus related to the amount of tissue perfused that has low absolute levels of perfusion or high degrees of flow heterogeneity.

Analysis of Variance↗
PubMed1990

A perfused tissue phantom, for ultrasound hyperthermia.

A perfused tissue phantom, developed as a tool for analyzing the performance of ultrasound hyperthermia applicators, was investigated. The phantom, consisting of a fixed porcine kidney with thermocouples placed throughout the tissue, was perfused with degassed water by a variable flow rate pump. The phantom was insonated by an unfocused multielement ultrasound applicator and the temperatures in the phantom were recorded. The results indicate that for testing protocols where tissue phantoms are needed, the fixed kidney preparation offers an opportunity to use a more realistic phantom than has previously been available to assess the heating performance of ultrasound hyperthermia applicators.

Animals↗
PubMed1991

Visceral and peripheral tissue perfusion after cardiac surgery.

Visceral and peripheral tissue perfusion and oxygenation were studied in ten patients in the early phase after coronary artery bypass grafting. Visceral perfusion was assessed indirectly, by determining gastric intramucosal pH. As parameters of peripheral tissue perfusion and oxygenation, subcutaneous tissue PO2 (PscO2), transcutaneous PO2 (PtcO2). PtcO2 index (PtcO2/PaO2), laser-Doppler skin red-cell flux (RCF) and fingertip temperature (Tft) were recorded in the upper extremity. Central haemodynamics, rectal temperature and blood gases were also measured. The inspired oxygen concentration was maintained at 30 v/v%. Gastric intramucosal pH declined progressively during the first 3 hours in the intensive care unit, reached its minimum at 5 hours and thereafter slowly increased. The peripheral vascular bed was shut down on admission to the ICU, as indicated by low values of PscO2, PtcO2, PtCO2 index, RCF and Tft. These parameters began to rise after the next 2-4 hours and peaked by the end of the 8-hour study period, indicating complete opening of the peripheral vascular bed.

Body Temperature↗
PubMed2003

Thermodiffusion for the quantification of tissue perfusion in skeletal muscle--clinical evaluation in standardized traumatological procedures with tourniquet and potential application in the diagnosis of compartment syndrome.

The quantification of tissue perfusion in different parenchymal organs like liver, kidney, and brain by means of thermodiffusion has recently been validated experimentally and was introduced into clinical practice. Traumatology and plastic surgery deal as well with issues of microcirculation. Therefore, it was the aim of this study to validate thermodiffusion for use in skeletal muscle. Eighteen patients were studied during knee arthroscopic procedures that utilized a tourniquet. A thermodiffusion probe was inserted in the tibialis anterior muscle of the side under treatment. Measurement started before the initiation of limb ischemia (by tourniquet) and continued throughout the procedure until tissue perfusion returned to normal values postoperatively. Furthermore, an example of clinical applicability of this technique is given by monitoring muscle tissue perfusion in 3 patients with imminent compartment syndrome. Preoperative values of muscle tissue perfusion in the patients undergoing arthroscopic procedures were 17.74 +/- 4.27 ml/min 100 g. After initiation of tourniquet perfusion quickly decreased to 3.59 +/- 3.53 ml/min 100 g. Upon reperfusion tissue perfusion increased to values above normal for a few minutes and then returned to preischemic values of 20.86 +/- 7.01 ml/min 100 g. There was no significant difference between pre- and postoperative values (P=0.154) but tissue perfusion during tourniquet was significantly reduced (P=0.0001). In 3 patients presenting with the clinical signs of imminent compartment syndrome, thermodiffusion measurement was applied and showed microcirculatory impairment of different degrees. Fasciotomy was followed by a prompt increase of muscle microcirculation to levels slightly above normal. In summary, valid and stable measurements of tissue perfusion in skeletal muscle by means of thermodiffusion are possible under clinical circumstances. Thermodiffusion allows for on-line monitoring of muscle microcirculation, e.g., in compartment syndrome. The clinical potential of thermodiffusion measurements in trauma surgery needs further prospective evaluation.

Adult↗
PubMed1999

Color Doppler energy--a new technique to study tissue perfusion in renal transplants.

Information on renal tissue perfusion after transplantation remains important for renal allograft monitoring. Findings obtained by conventional Doppler sonography are limited to vascular resistance (RI). The new technique color Doppler energy (CDE) is Doppler angle independent, omits flow velocity and direction, and is proportional to the returning signal strength. The aim of our study was to standardize the application of this technique and to analyze the information obtained. Forty-six CDE studies were performed with an Acuson 128XP in 28 children (mean age 12.4+/-5.3 years) between 4 days and 10 years after renal transplantation. The most-reproducible information was obtained with a 5-MHz linear probe and a constant area of 2x3 cm (log compression 40 dB, filter 3). CDE provided a high-resolution cross-sectional display of perfused cortical tissue vessels. According to the density of signals, the perfusion could be grouped into six perfusion scores (PS). The interobserver concordance was more than 85%. No correlation was found between PS and RI or blood pressure. However, there was a significant correlation between PS and glomerular filtration rate (r=-0.78, P<0. 001). These first results demonstrate a significant relationship between PS and chronic rejection. Non-rejection-related functional impairment exhibited no decrease in PS. We conclude that our proposed standardized CDE renal study is observer independent. CDE is a promising new technique that provides information on renal allograft dysfunction that is different from classical color Doppler findings. Further studies will clarify its role in renal transplant monitoring and its ability to replace more-invasive techniques.

Adolescent↗
PubMed1998

Epidural analgesia with bupivacaine does not improve splanchnic tissue perfusion after aortic reconstruction surgery.

Inadequate splanchnic tissue perfusion is relatively common during and after aortic surgery. We hypothesized that vasodilation caused by thoracic epidural analgesia improves splanchnic blood flow and tissue perfusion after aortic surgery. In this prospective, randomized, controlled study, we studied 20 patients undergoing elective aortic-femoral or aortic-iliac reconstruction surgery. Gastric and sigmoid colon mucosal PCO2 and pH were measured during surgery. An epidural bolus of bupivacaine 40 mg followed by infusion of 15 mg h-1 was started after operation in 10 patients. After operation, splanchnic blood flow and gastric and sigmoid colon mucosal PCO2 and pH were measured before and 2 h after the start of epidural analgesia. During surgery, the gastric mucosal-arterial PCO2 difference remained stable, whereas the sigmoid mucosal-arterial PCO2 difference increased during aortic clamping but returned to pre-clamping values after declamping. After operation, epidural analgesia had no effect on gastric or sigmoid mucosal-arterial PCO2 differences or on splanchnic blood flow.

Acidosis↗
PubMedDate not supplied

Ineffective peripheral tissue perfusion: Clinical validation in patients with hypertensive cardiomiopathy.

PURPOSE: To validate defining characteristics of ineffective peripheral tissue perfusion using vasomotor function assessment. METHODS: Twenty-four patients with hypertensive cardiomiopathy were evaluated for 18 defining characteristics of ineffective peripheral tissue perfusion and underwent vasomotor function assessment with induction of reactive hyperemia, intra-arterial infusion of acetylcholine, and pulse wave velocity measurement. The Student's t test and Kruskall-Wallis test were used to assess the significance of relationships between defining characteristics and vasomotor function data. FINDINGS: Diminished lower extremity pulses were associated with diminished forearm blood flow during acetylcholine infusion; left ventricular overload, intermittent claudication, and diminished skin moisture were associated with elevated pulse wave velocity values. CONCLUSION: The defining characteristics of ineffective peripheral tissue perfusion were highly associated with vasomotor function data as "gold standards" for that diagnosis. PRACTICE IMPLICATIONS: Nurses should be able to accurately assess diminished lower extremity pulses, intermittent claudication, and diminished skin moisture as relevant characteristics of ineffective peripheral tissue perfusion in patients with hypertensive cardiomiopathy.

Acetylcholine↗
PubMed1981

Bubble dynamics in perfused tissue undergoing decompression.

A mathematical model describing bubble dynamics in a perfused tissue undergoing decompression is presented, taking into account physical expansion and inward diffusion from surrounding supersaturated tissue as growth promoting factors and tissue gas elimination by perfusion, tissue elasticity, surface tension and inherent unsaturation as resolving driving forces. The expected behavior after a step reduction of pressure of a bubble initially existing in the tissue, displaying both growth and resolution has been demonstrated. A strong perfusion-dependence of bubble resolution time at low perfusion rates is apparent. The model can account for various exposure pressures and saturation fractions of any inert gas-tissue combination for which a set of physical and physiological parameters is available.

Animals↗
PubMed2002

Endothelial cell dysfunction and abnormal tissue perfusion.

OBJECTIVE: To determine the precise role of the myoendothelial regulatory unit in improved tissue perfusion and metabolic regulation. DATA SOURCES AND STUDY SELECTION: A review of the published literature (MEDLINE and other original articles and reviews) on endothelial cells, vascular reactivity, and tissue perfusion. DATA EXTRACTION AND SYNTHESIS: According to the concept of intrinsic metabolic regulation, vasodilation in tissues with relatively high metabolic rates competes with sympathetic vasoconstrictor tone, thereby adjusting the balance between local tissue oxygen supply and demand. Although the nature of the oxygen-sensitive structures acting at the local tissue level is not completely understood, endothelial cells in direct contact with blood have a number of properties that confer the potential to act as effective oxygen sensors. The endothelium and smooth muscle of arteries and arterioles seem to be coupled both structurally and functionally. Sensing involves local depolarization and hyperpolarization of the capillary endothelial cell, and communication is achieved by an electronic spread via endothelium-smooth muscle cell-to-cell gap junctions. Therefore, during hypoxic challenge, the ability of a tissue to extract oxygen-and to minimize shunting through areas with a high rate of perfusion relative to their oxygen uptake-may be considered an integrative test of endothelium function and microcirculatory coordination. CONCLUSION: Endothelial cells seem to play a central role in coordinating the microcirculatory system and promoting tissue perfusion and oxygen supply. In a pathologic situation such as sepsis, abnormal interendothelial cell coupling and an abnormal arteriolar conducted response may account for impaired tissue perfusion and abnormal oxygen extraction.

Animals↗
PubMed1996

Intraoperative maintenance of tissue perfusion prevents ARDS. Adult Respiratory Distress Syndrome.

Patients undergoing prolonged, complex oncological surgery are at increased risk of developing the adult respiratory distress syndrome (ARDS) and other organ failures. Our hypothesis is that maintaining adequate tissue perfusion and oxygenation may prevent tissue hypoxia and acidosis in pulmonary, peripheral, and splanchnic microcirculations. Experimental evidence suggests that the hypoxic, acidotic endothelium stimulates the release of cytokines, kinins, and other mediators. We developed and tested an intraoperative protocol for surgical patients likely to develop ARDS and organ dysfunction; the protocol focuses on the intraoperative period but is not limited to this time. Nitroglycerin and fluids were used to maintain tissue perfusion and prevent tissue hypoxia as reflected by transcutaneous oxygen tension values. In 155 high-risk patients, none developed ARDS. We conclude that maintenance of tissue perfusion and oxygenation in high-risk surgical patients decreases the incidence of ARDS.

Adult↗
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↗
PubMed2003

Quantitative tissue perfusion measurements in head and neck carcinoma patients before and during radiation therapy with a non-invasive MR imaging spin-labeling technique.

PURPOSE: Tumor blood flow, tumor tissue perfusion and oxygen supply have substantial influence on the responsiveness of tumors to radiotherapy. This study was aimed at implementing and evaluating a non-invasive functional magnetic resonance (MR) imaging spin-labeling technique at a main magnetic field strength of 2T for measuring tissue perfusion changes in head and neck carcinoma patients before and during radiotherapy. METHODS: Tissue perfusion was determined quantitatively in ten patients with head and neck cancer. Five patients were investigated twice during radiation therapy. For perfusion measurements, a non-invasive MR spin-labeling technique was employed: The longitudinal relaxation time T(1) was measured with segmented Snapshot-FLASH imaging after either slice-selective or non-selective spin inversion. Perfusion values were calculated pixelwise employing a two-compartment tissue model. With this technique no contrast agents are required so that repetitive measurements are possible. Perfusion images with a slice thickness of 10mm and an in-plane resolution of 1.9x2.8mm(2) were acquired at a total scan time of 8:30min per scan. RESULTS: With the non-invasive MR imaging technique it was possible to visualize tumor and normal tissue perfusion as well as perfusion changes in the course of radiotherapy with a spatial resolution of less than 3mm. Among the investigated subjects measured tumor perfusion and changes in perfusion were heterogenous. In 4/5 patients studied at the start and end of radiotherapy, perfusion decreased, while in one patient there was an increase. CONCLUSIONS: A method is presented that allows non-invasive and repetitive characterization of tissue perfusion. This parameter may be used for treatment stratification, especially in treatments that use vasomodulation or anti-angiogenic agents.

Algorithms↗
PubMed1991

Measurement of tissue perfusion by dynamic computed tomography.

A method for quantifying tissue perfusion by dynamic computed tomography (CT) is described. By applying a nuclear medicine data processing technique to time-density data from a single-location dynamic CT sequence, tissue perfusion can be determined from the maximum gradient of the tissue time-density curve divided by the peak enhancement of the aorta. Using this method, splenic perfusion was measured at 1.2 ml min-1 ml-1, normal renal cortical perfusion at 2.5 ml min-1 ml-1 and normal renal medullary perfusion at 1.1 ml min-1 ml-1. Changes in cortical and medullary perfusion in renal failure and hypertension were demonstrated. The ability of dynamic CT to provide quantitative functional information is not well recognized and is potentially of value when studying structures, such as the renal cortex and medulla, that cannot be anatomically resolved by standard functional imaging techniques.

Contrast Media↗
PubMed1993

Pentoxifylline restores cardiac output and tissue perfusion after trauma-hemorrhage and decreases susceptibility to sepsis.

BACKGROUND: Although pentoxifylline produces various beneficial effects in a preheparinized model of hemorrhagic shock, it was unknown whether this agent restores the depressed cardiac output (CO) and tissue perfusion in a nonheparinized model of trauma-hemorrhage and resuscitation and, if so, whether it decreases the susceptibility to sepsis after hemorrhage. METHODS: After laparotomy (i.e., induction of trauma), rats were bled to and maintained at a mean arterial pressure of 40 mm Hg until 40% of the maximum shed blood volume was returned in the form of Ringer's lactate. The animals were then resuscitated with Ringer's lactate, four times the volume of shed blood. Pentoxifylline (50 mg/kg body weight) or normal saline solution was infused intravenously more than 95 minutes during and after resuscitation. At 1.5 and 4 hours after resuscitation, CO, tissue perfusion, and plasma liver enzyme levels were determined. Sepsis was induced by cecal ligation and puncture at 20 hours after hemorrhage, and the necrotic cecum was excised 10 hours thereafter. RESULTS: CO and tissue perfusion in the liver, kidney, spleen, and small intestine decreased significantly after hemorrhage and resuscitation. Pentoxifylline treatment, however, restored the depressed CO and tissue perfusion. The elevated liver enzyme levels were also significantly reduced by pentoxifylline treatment. Moreover, pentoxifylline prevented the increased mortality of posthemorrhaged rats subjected to sepsis. CONCLUSIONS: Because pentoxifylline restored the depressed CO and tissue perfusion and decreased the susceptibility to sepsis, this agent appears to be a useful adjunct to crystalloid resuscitation after trauma and hemorrhage, even in the absence of blood resuscitation.

Alanine Transaminase↗
PubMed1990

Tissue perfusion in anaesthetised sheep.

1. Tissue perfusion was measured in seven sheep by the radioactive microsphere method. 2. The sheep were anaesthetised and ventilated to a near normal arterial carbon dioxide tension. 3. Cardiac output was measured utilizing the Fick principle as applied to thermodilution and at the end of the investigation the sheep were killed by an overdose of anaesthetic. 4. The results were compared with previously published values for conscious sheep and anaesthetised horses and found to be similar when known variations in body composition and physiology were considered.

Anesthesia, General↗
PubMed1986

Intracellular brain pH, indicator tissue perfusion, electroencephalography, and histology in severe and moderate focal cortical ischemia in the rabbit.

Intracellular brain pH and indicator tissue perfusion were measured with a lipid-soluble, pH-sensitive fluorescent indicator in 10 rabbits who had either severe or moderate focal ischemia depending on whether the middle cerebral artery was occluded at its main trunk or bifurcation. Preocclusion tissue indicator perfusion was 50.1 ml/100 g/min and intracellular brain pH was 7.03. In severe focal ischemia, immediate postocclusion tissue perfusion was 12.7 ml/100 g/min and intracellular brain pH was 6.64. Four hours after occlusion, the perfusion was 5.2 ml/100 g/min and intracellular brain pH was 6.08. There was EEG and histological confirmation of infarction. In the moderate focal ischemia group, immediate postocclusion flow was 20.0 ml/100 g/min and intracellular brain pH was 6.92. At 3 h, postocclusion tissue perfusion was 22.6 ml/100 g/min and intracellular brain pH was 6.86. Therefore, for the first 3 h, this ischemic penumbra was stable. At the fourth hour, both cerebral tissue perfusion and intracellular brain pH worsened. This suggests that the ischemic penumbra is a dynamic state. The rabbit is a good experimental model for the production of both severe and moderate focal ischemia.

Animals↗
PubMed2002

Increased pressure during retrograde cerebral perfusion in an acute porcine model improves brain tissue perfusion without increase in tissue edema.

BACKGROUND: There is a significant lack of scientific data to support the clinically accepted view that 25 to 30 mm Hg is the maximum safe perfusion pressure during retrograde cerebral perfusion (RCP). This study was designed to investigate whether perfusion pressure greater than 30 mm Hg during RCP is beneficial to the brain during prolonged HCA in an acute porcine model. METHODS: Sixteen pigs underwent 120 minutes of circulatory arrest in conjunction with RCP at a perfusion pressure of either 23 to 29 mm Hg (group L, n = 8) or 34 to 40 mm Hg (group H, n = 8) at 15 degrees C, followed by 60 minutes of normothermic cardiopulmonary bypass. Cortical blood flow and oxygenation were measured continuously with a laser flowmeter and near-infrared spectroscopy, respectively. Tissue water content was measured at the end of the experiments. RESULTS: Brain tissue blood flow was significantly higher in group H than in group L (16.8% +/- 4.1% vs 4.8% +/- 0.9% of baseline, p < 0.01) during RCP. Brain oxygen extraction in group L reached a maximum (approximately 70%) immediately after starting RCP, whereas in group H it increased gradually and reached a maximum at 120 minutes of RCP, indicating a greater supply of oxygen to tissue in group H than in group L. After RCP, the ability of brain tissue to use oxygen was better preserved in group H than in group L, as indicated by tissue oxygen saturation and the deoxyhemoglobin level. There was no significant increase in tissue water content in either group (group H 79.2% +/- 0.3%, group L 79.1% +/- 0.4%) relative to normal control pigs (78.7% +/- 0.1%). CONCLUSIONS: In this acute porcine model, increasing perfusion pressure from 23-29 to 34-40 mm Hg during RCP increases tissue blood flow and provides better tissue oxygenation, without increasing tissue edema. The optimal perfusion pressure for RCP needs to be further investigated.

Animals↗