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At least 109 records · Page 6Linked to original sources
PubMed2000

Stimulated acoustic emission detected by transcranial color doppler ultrasound : a contrast-specific phenomenon useful for the detection of cerebral tissue perfusion.

BACKGROUND AND PURPOSE: Experimental and clinical data suggest that insonation of echo-contrast agents with high acoustical power produces disintegration of microbubbles, resulting in a pseudo-Doppler phenomenon called stimulated acoustic emission (SAE). The purpose of this study was to investigate whether SAE might be detected by transcranial color Doppler imaging and whether these signals might be used for cerebral tissue perfusion measurements. METHODS: Nonmoving microbubbles (SHU 563 A) were insonated in vitro through the temporal parts of a human cadaver skull, and contrast signals were detected by velocity-coded color Doppler and power Doppler recordings. Transcranial color as well as power Doppler investigations were performed in 10 healthy volunteers with the echo-contrast agent Levovist (SHU 508 A). RESULTS: Color Doppler signals indicating SAE were observed in vitro and in transcranial human investigations. These signals were characterized by a mosaic of color Doppler pixels ranging over the full color scale. Apparent velocity information and spatial distribution of SAE signals changed from image frame to image frame. In the experimental model, the intensity of SAE signals decreased exponentially over time. With an increase of acoustic power, there was a significant increase of the maximum signal intensity (P<0.01) and a significantly shortened signal duration (P<0.01), consistent with stronger and more rapid disintegration. In humans, SAE signals were clearly detected in cerebral tissue regions. The intensity of SAE signals in those regions (eg, temporal cortex, 3.7+/-1.2 dB) was approximately 8 times lower than the signal enhancement in the major cerebral arteries (eg, in the MCA, 29.5+/-5.6). CONCLUSIONS: Echo-contrast specific color Doppler signals known as SAE are detectable by transcranial color and power Doppler sonography. Signals due to SAE might represent tissue perfusion, thereby providing a method for imaging flow with transcranial ultrasound.

Adult↗
PubMed2001

Effect of radial artery harvesting on tissue perfusion and function of the hand.

This study was designed to measure the degree to which hand and forearm blood flow is reduced following harvesting of the radial artery in myocardial revascularization surgery and determine whether there is an effect on hand function. Twenty patients who had the radial artery used for myocardial revascularization underwent bilateral blood flow assessment of hands and forearms using Technetium-99m human serum albumin and clinical evaluation of hand function. Mean tissue perfusion in ml/100 ml/min +/- SD was as follows: donor hand 21.9 +/- 5.6, non-donor hand 25.5 +/- 6.1 (P = 0.00043), donor arm (hand and forearm) 17.5 +/- 3.7 and non-donor arm (hand and forearm) 21 +/- 5.1 (P = 0.000681). No clinical evidence of hand claudication was detected. This study suggests that removal of the radial artery reduces the tissue perfusion of the hand and forearm but does not affect hand function in the short term. The use of radial artery grafts in patients at risk of developing peripheral vascular disease should be carefully considered

Adult↗
PubMed1991

Hydralazine-induced changes in tissue perfusion and radiation response in a C3H mammary carcinoma and mouse normal tissues.

Hydralazine has been reported to reduce blood perfusion in tumours, thereby increasing hypoxia and subsequently enhancing tumour sensitivity to certain drugs and hyperthermia. We have investigated the ability of hydralazine to induce such changes in a C3H mouse mammary carcinoma and various normal tissues. In tumours, hydralazine (5 mg/kg; i.v.) modified the radiation response, measured by a local tumour control assay, producing an effect equivalent to that seen in tumours made fully hypoxic by clamping. This effect was time-dependent and correlated with the decrease in tissue perfusion estimated by the 86-RbCl extraction procedure. Similar effects were seen in normal skin, although the changes were less dramatic and of a shorter duration. Hydralazine also reduced 86-RbCl uptake in liver, kidney, gut and spleen, but not in bladder, muscle and lung, suggesting that it may have the potential to increase the sensitivity of some normal tissues to hypoxic cell cytotoxins.

Animals↗
PubMed1980

Tissue perfusion and distribution of cardiac output during ketamine anesthesia in normovolemic rats.

Based on previous clinical experience, an anesthetic technique for the rat, using ketamine, has been evaluated. The method comprised an i.v. bolus injection of 30 mg/kg for induction and an i.v. continuous infusion of 1.5 mg/kg/min for maintenance of anesthesia. Minor differences in ketamine metabolism between man and the rat are discussed. It appears that a higher ketamine concentration at the receptor site was required in the rat as compared to man. During ketamine anesthesia in the rat, fractional distribution of cardiac output and regional tissue perfusion were determined with the aid of the microsphere method. The study showed increased fractions to the heart, brain and tongue. The carcass fraction was elevated shortly after induction but reduced during steady-state anesthesia. Stomach, bowel and kidneys received reduced fractions early, but after these fractions returned to their initial levels. As a consequence of the increased cardiac output, regional tissue perfusion was increased in practically all organs.

Anesthesia, Intravenous↗
PubMed1981

Continuous tissue pH and transcutaneous PO2 measurement as an index of tissue perfusion in critically ill patients.

Measurements of transcutaneous PO2 (tcPO2) and tissue pH (pHt) were compared with arterial values in 28 critically ill patients. Eleven of the patients were undergoing continuous flow cardiopulmonary bypass and the other 17 were admitted to the Intensive Therapy Unit (ITU) suffering from a variety of medical and surgical disorders. A total of 135 observations were made on the 28 patients. The overall correlation between the two sets of measurements was poor. The correlation coefficient (r) between arterial PO2 (Pa,O2) and tcPO2 was 0.41 (P less than 0.01) and between arterial pH (pHa) and pHt 0.67 (P less than 0.01). However, the value varied greatly in different groups of patients. In those patients with cardiopulmonary failure, the tcPO2 and pHt measurements rapidly and accurately reflected changes in peripheral tissue perfusion, by contrast the core-peripheral temperature deficit did not change significantly. It is concluded that the technique can be used as a sensitive index of peripheral blood flow and may have prognostic significance

Adult↗
PubMed2003

Measurement of renal tumour and normal tissue perfusion using positron emission tomography in a phase II clinical trial of razoxane.

Measurement of tumour and normal tissue perfusion in vivo in cancer patients will aid the clinical development of antiangiogenic and antivascular agents. We investigated the potential antiangiogenic effects of the drug razoxane by measuring the changes in parameters estimated from H(2)(15)O and C(15)O positron emission tomography (PET) to indicate alterations in vascular physiology. The study comprised 12 patients with primary or metastatic renal tumours >3 cm in diameter enrolled in a Phase II clinical trial of oral razoxane. Perfusion, fractional volume of distribution of water (VD) and blood volume (BV) were measured in tumour and normal tissue before and 4-8 weeks after treatment with 125 mg twice-daily razoxane. Renal tumour perfusion was variable but lower than normal tissue: mean 0.87 ml min(-1) ml(-1) (range 0.33-1.67) compared to renal parenchyma: mean 1.65 ml min(-1) ml(-1) (range 1.16-2.88). In eight patients, where parallel measurements were made during the same scan session, renal tumour perfusion was significantly lower than in normal kidney (P=0.0027). There was no statistically significant relationship between pretreatment perfusion and tumour size (r=0.32, n=13). In six patients scanned before and after razoxane administration, there was no statistically significant change in tumour perfusion: mean perfusion pretreatment was 0.81 ml min(-1) ml(-1) (range 0.46-1.26) and perfusion post-treatment was 0.72 ml min(-1) ml(-1) (range 0.51-1.15, P=0.15). Tumour VD and BV did not change significantly following treatment: mean pretreatment VD=0.66 (range 0.50-0.87), post-treatment VD=0.71 (range 0.63-0.82, P=0.22); pretreatment BV=0.18 ml ml(-1) (range 0.10-0.25), post-treatment BV=0.167 ml ml(-1) (range 0.091-0.24, P=0.55). Tumour perfusion, VD and BV did not change significantly with tumour progression. This study has shown that H(2)(15)O and C(15)O PET provide useful in vivo physiological measurements, that even highly angiogenic renal cancers have poor perfusion compared to surrounding normal tissue, and that PET can provide valuable information on the in vivo biology of angiogenesis in man and can assess the effects of antiangiogenic therapy.

Antineoplastic Agents↗
PubMed1985

Improved tissue perfusion during pressure regulated hyperthermic regional isolated perfusion. A clinical study.

In previous studies on isolated hindlimb perfusions in dogs, the authors proved that the extracorporeal circuit should be regulated at a delta pressure (systemic mean arterial pressure minus hindlimb mean arterial pressure) of not more than 15 mmHg, to achieve adequate tissue perfusion. To confirm this in patients the authors performed clinical perfusions, divided into three groups. In group I and II the extracorporeal circuit was regulated at a delta pressure of 15 mmHg and 50 mmHg, respectively. In group III perfusions were performed using the common technique of a predetermined fixed flow. Tissue oxygenation, determined by means of a transcutaneous pO2 electrode, was adequate in group I and was severely impaired in group II and III. Although in group I high perfusion flows were needed, leakage was less than 10%. To achieve adequate tissue perfusion during clinical regional perfusions, the extracorporeal circuit must be regulated at a delta pressure of 15 mmHg.

Adult↗
PubMed1999

Intraoperative evaluation of tissue perfusion in high-risk patients by invasive and noninvasive hemodynamic monitoring.

OBJECTIVE: Although invasive monitoring has not been effective in late stages after organ failure has occurred, early postoperative monitoring revealed differences in survivor and nonsurvivor patterns and provided goals for improving outcome. We searched for the earliest divergence of survivor and nonsurvivor circulatory changes as an approach to earlier preventive therapy. The aim was to describe the intraoperative time course of circulatory dysfunction in survivors and nonsurvivors among high-risk elective surgery patients using both the thermodilution pulmonary artery catheter (PAC) and multicomponent noninvasive monitoring. DESIGN: Prospective intraoperative description of circulatory dysfunction. SETTING: University-run county hospital. PATIENTS: Two hundred nine consecutively monitored high-risk elective surgery patients. MEASUREMENTS AND MAIN RESULTS: We evaluated the data of high-risk elective surgery patients using both PAC and multicomponent noninvasive monitoring. The latter consisted of the following: a) an improved bioimpedance method for estimating cardiac output; b) the standard pulse oximetry to screen for pulmonary problems; c) transcutaneous oxygen and carbon dioxide tension sensors to evaluate tissue perfusion; and d) routine noninvasive blood pressure and heart rate. The current noninvasive impedance cardiac output estimations closely approximated those of the thermodilution method; r2 = .74, p < .001; the precision and bias was -0.124 +/- 0.75 L/min/m2. Outcome measures included intraoperative description of circulatory patterns of high-risk surgical patients who survived compared with nonsurvivors. Hypotension, low cardiac index, arterial hemoglobin desaturation, low transcutaneous oxygen, high transcutaneous carbon dioxide tensions, low oxygen delivery, and low oxygen consumption developed intraoperatively gradually over time; the abnormalities were more pronounced in the nonsurvivors than in the survivors. CONCLUSIONS: The survivors had slightly higher mean arterial pressure, cardiac index, and mixed venous oxygen saturation, as well as significantly higher oxygen delivery, oxygen consumption, transcutaneous oxygen tension, and transcutaneous oxygen tension/FIO2 ratios, than did the nonsurvivors. The data suggest that blood flow, oxygen delivery, and tissue oxygenation of the nonsurvivors became inadequate toward the end of the operation. Noninvasive monitoring provides similar information to that of the PAC; both approaches revealed low-flow and poor tissue perfusion that were worse in the nonsurvivors. The continuous on-line real-time displays of hemodynamic trends facilitate early recognition of acute circulatory dysfunction.

Carbon Dioxide↗
PubMed1989

Arterialization of liver transplants in rats: I. Application of the tissue perfusion monitor in hemodynamic studies.

This study demonstrates the use of the tissue perfusion monitor in the investigation of arterialization (using an arteriovenous fistula) of the heterotopic partial liver transplant. An index of peak perfusion rate was introduced as a reliable and accurate measure of the index of delivery rate of blood to the liver. Results revealed a significant (P less than .01) difference between arterialized and nonarterialized liver grafts when compared with their respective recipient host livers. Arterialization of grafted livers raised the index of peak perfusion rate to levels that were comparable to host livers. Arterialization also had a significant effect (P less than .01) on the host liver, whose values dropped by 74.26% when compared with the normal liver. Surprisingly, host values of the nonarterialized group fell by 61.54%. At this point, explanations for this phenomenon are speculatory. An extensive review of the literature exposes the variability in the observations of the role and usefulness of arterialization in hepatocellular function.

Anastomosis, Surgical↗
PubMed1982

The effect of hypothermia and tissue perfusion on extended myocutaneous flap viability.

The salutary effect of hypothermia and tissue perfusion on extending the ischemic tolerance of the canine latissimus dorsi myocutaneous flap was demonstrated in this experimental study. A total of 175 flaps from 89 adult mongrel dogs were elevated with one-half the flaps perfused with iced Collins renal preservation solution. With the exception of control flaps kept at ambient temperature, the remaining flaps were stored at 4 degrees C for periods ranging from 24 to 192 hours followed by transplantation into the groins of recipient dogs, with anastomosis of the thoracodorsal artery and vein in an end-to-side manner to the femoral artery and vein, respectively. The study was divided into two distinct sections. The acute phase involved the transplantation of 77 flaps into random recipient dogs, and following a 3-hour period of systemic perfusion, the flaps were removed, weighed, and sectioned for later histologic study. Progressive increase in flap weight was observed up to 96 hours of hypothermia with a sharp decline in weight at 120 hours of hypothermia. The increase in flap weight in the nonperfused flaps was significantly greater than the previously perfused flaps. Histologically, at 120 hours of hypothermia, loss of vascular integrity was noted, suggestive of a no-reflow phenomenon. In the second, or extended-flap, study, 98 flaps were transplanted into the groins of the original donor animal and allowed to remain in situ for a 2-week period. The flaps were then carefully observed for viability, removed, and sectioned for histologic study. Hypothermic support of up to 96 hours extended viability in both perfused and nonperfused flaps, although beyond this hypothermic period viability was seen only in previously perfused flaps. The clinical implications of this study include hypothermic perfusion of a major-extremity amputation prior to replantation or the temporary storage of a free myocutaneous flap.

Animals↗
PubMed1971

Sites of lipoprotein lipase activity in adipose tissue perfused with chylomicrons. Electron microscope cytochemical study.

Lipoprotein lipase activity was studied in rat parametrial adipose tissue perfused with chylomicrons and in gelatin blocks containing postheparin plasma and chylomicrons. The tissues and blocks were fixed in glutaraldehyde and incubated in 0.035 M CaCl(2)-0.1 M Tris medium (pH 8.3) at 38 degrees C. The doubly labeled chylomicron triglycerides (glycerol-(3)H and palmitate-(14)C) in the tissues and blocks were hydrolyzed during incubation to free fatty acids (FFA) and the FFA remained in the specimens; hydrolysis was inhibited by 0.004 M diethyl paranitrophenyl phosphate (E-600). Incubated blocks and tissue were treated with 0.05 M Pb(NO(3))(2), postfixed in OsO(4), dehydrated with acetone, embedded in Epon, and examined by electron microscopy. The incubated blocks contained electronlucent areas and granular and laminar precipitates at sites of hydrolysis. Similar precipitates were found in incubated tissue, within vacuoles and microvesicles of capillary endothelium, and in the subendothelial space (between the endothelium and pericytes), but not in the capillary lumen or in or near fat cells. The cytochemical reaction was greatly reduced, in blocks and tissues incubated with E-600. It is concluded that plasma glycerides are hydrolyzed by lipoprotein lipase in capillary endothelial cells and in the subendothelial space of adipose tissue and that glycerides across the endothelial cells within a membrane-bounded system.

Adipose Tissue↗
PubMed2005

Regional carbon dioxide monitoring to assess the adequacy of tissue perfusion.

PURPOSE OF REVIEW: Tissue dysoxia is now widely regarded as the major factor leading to organ dysfunction in critically ill patients. Recent data suggests that early aggressive resuscitation of critically ill patients, which limits and/or reverses tissue dysoxia may prevent progression to organ dysfunction and improve outcome. The traditional clinical and laboratory markers used to assess tissue dysoxia are, however, insensitive and have numerous limitations. Regional carbon dioxide monitoring appears to be ideally suited to monitoring the adequacy of resuscitation. This review provides an update on this evolving technology. RECENT FINDINGS: Gastric intramucosal carbon dioxide as measured by gastric tonometry has proven to be useful as a prognostic marker, in evaluating the response to specific therapeutic interventions and as an end point of resuscitation. Gastric tonometry is, however, cumbersome and has a number of limitations that may have prevented its widespread adoption. The measurement of carbon dioxide in the sublingual mucosa by sublingual capnometry is technically simple, noninvasive, and provides near instantaneous information. Clinical studies have demonstrated a good correlation between gastric intramucosal carbon dioxide and sublingual mucosa carbon dioxide. Sublingual mucosa carbon dioxide responds more rapidly to therapeutic interventions than does gastric intramucosal carbon dioxide and may be a better prognostic marker. SUMMARY: Sublingual capnometry may be the ideal technology for guiding early goal directed therapy. This technology may be useful for monitoring tissue oxygenation, titrating therapeutic interventions, and as an end point for resuscitation in critically ill and injured patients.

Administration, Sublingual↗
PubMed1990

Tissue perfusion in humans studied by Fourier velocity distribution, line scan, and echo-planar imaging.

In tissue perfusion studies, FT velocity distribution imaging (VDI) intrinsically distinguishes signals from moving blood and volume-averaged tissue. Results in human thyroid gland, in vivo, using VDI line scan technique demonstrated separation of moving blood signal from glandular tissue, while VDI inner-volume echo-planar imaging of brain showed only CSF velocity above the image noise level. New alternating polarity gradient sequences which permit separation of diffusion and slow velocity are discussed. A novel method of 3D FT imaging (two spatial and one velocity dimension) combining inner-volume imaging and echo-planar imaging with velocity resolution of 0.15 mm/s per pixel is demonstrated. A novel graphical method of calculation and display of diffusion dependence in pulsed gradient sequences is presented.

Blood Flow Velocity↗
PubMed2000

Adenovirus-mediated VEGF(121) gene transfer stimulates angiogenesis in normoperfused skeletal muscle and preserves tissue perfusion after induction of ischemia.

BACKGROUND: Administration of angiogenic factors stimulates neovascularization in ischemic tissues. However, there is no evidence that angiogenesis can be induced in normoperfused skeletal muscles. We tested the hypothesis that adenovirus-mediated intramuscular (IM) gene transfer of the 121-amino-acid form of vascular endothelial growth factor (AdCMV.VEGF(121)) could stimulate neovascularization in nonischemic skeletal muscle and consequently attenuate the hemodynamic deficit secondary to surgically induced ischemia. METHODS AND RESULTS: Rabbits and rats received IM injections of AdCMV.VEGF(121), AdCMV.Null, or saline in the thigh, 4 weeks (rabbits) or 2 weeks (rats) before femoral artery removal in the injected limb. In unoperated rats, at the site of injection of AdCMV.VEGF(121), we found 96% and 29% increases in length density of arterioles and capillaries, respectively. Increased tissue perfusion (TP) to the ischemic limb in the AdCMV.VEGF(121) group was documented, as early as day 1 after surgery, by improved blood flow to the ischemic gastrocnemius muscle measured by radioactive microspheres (AdCMV.VEGF(121)=5.69+/-0.40, AdCMV.Null=2.97+/-0.50, and saline=2.78+/-0.43 mL x min(-1) x 100 g(-1), P<0.001), more angiographically recognizable collateral vessels (angioscore) (AdCMV. VEGF(121)=50.58+/-1.48, AdCMV.Null=29.08+/-4.22, saline=11.83+/-1.90, P<0.0001), and improvement of the bioenergetic reserve of the gastrocnemius muscle as assessed by (31)P NMR spectroscopy. Follow-up studies showed that superior TP to the ischemic limb in the AdCMV.VEGF(121) group persisted until it was equalized by spontaneous collateral vessel development in untreated animals. CONCLUSIONS: IM administration of AdCMV.VEGF(121) stimulates angiogenesis in normoperfused skeletal muscles, and the newly formed vessels preserve TP after induction of ischemia.

Adenoviridae↗
PubMed1981

Liver tissue perfusion: comparison of radiologic and isotope clearance techniques in a patient with portal hypertension.

A patient with portal hypertension was investigated preoperatively with splenoportography and found to have a large extrahepatic shunt through esophageal varices but poor portal perfusion of the liver. However, intraoperative measurement of the hepatic tissue perfusion using the krypton-85 clearance technique showed it to be essentially normal. Erroneous conclusions about actual hepatic perfusion may be made on the basis of findings on splenoportography alone.

Aged↗
PubMed2001

In vivo assessment of endothelin-induced heterogeneity of hepatic tissue perfusion.

Specific vasoactive substances such as endothelin (ET) have been proposed to induce heterogeneity of tissue perfusion and thus the oxygen delivery at the sinusoidal level in the liver, but a direct method for testing this hypothesis has not been available. Our objective was to develop a method to test the hypothesis that functional heterogeneity of blood flow can be induced at the sinusoidal level by mediators such as endothelin-1, which act at the sinusoidal level. We constructed oxygen-sensitive membranes using tris (1,10-phenanthroline) ruthenium (II) chloral hydrate, a dye whose fluorescence is quenched by oxygen incorporated into a silicon rubber membrane. The membrane (less than 40 microm thick) was formed on a glass coverslip that served as the viewing window of the system for in vivo fluorescence microscopy and allowed determination of the PO2 distribution in rat liver acini during intraportal infusion of ET or phenylephrine (PE) in vivo. Heterogeneity was quantified by comparing the coefficient of variation (CV) of the fluorescence intensity within the zone 1 before, during, and after drug infusion. PE and ET doses were matched to produce a similar increase in portal pressure. PE caused a gradient of PO2 across zones, but within zone 1 no significant increase in CV was observed. In contrast, ET produced a patchy pattern of both an increase and decrease in PO2 resulting in doubling (P < 0.01) in CV of fluorescence intensities within zone 1. These results indicate that PE, which acts at presinusoidal sites, results in a homogeneous decrease in tissue PO2 within a zone, while ET, which additionally acts at sinusoidal sites, induces significant microheterogeneity of tissue PO2. The oxygen-sensitive membrane provides a useful tool for oxygen mapping in vivo.

Animals↗
PubMed1999

Effect of carbogen inhalation on peripheral tissue perfusion and oxygenation in patients suffering from sudden hearing loss.

The effects of repeated carbogen inhalation on peripheral tissue perfusion and oxygenation were assessed in 5 patients suffering from sudden hearing loss by means of continuously measured subcutaneous tissue oxygen and carbon dioxide tension, transcutaneous oxygen tension, laser Doppler red cell flux, and fingertip temperature. The subcutaneous oxygen tension increased clearly during the carbogen inhalation periods, and also, a smaller increase in subcutaneous carbon dioxide tension was simultaneously noticed. The changes in transcutaneous oxygen tension were even greater and the latency was shorter as compared with the subcutaneous gas tensions. The laser Doppler measurements showed no signs of vasoconstriction during the study. In conclusion, carbogen inhalation increases peripheral tissue oxygenation without microvascular vasoconstriction and with only a minor retention of carbon dioxide.

Administration, Inhalation↗