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PubMed2006

Morphological transformation in esophageal submucosa by bone marrow cells: esophageal implantation under external esophageal perfusion.

Accumulating clinical and experimental studies indicate that Barrett's esophagus might arise through multipotential stem cells under the stress of gastroesophageal reflux. Previously, we have presented a novel external pump perfusion rat model and demonstrated that perfusion with both acid and bile can induce severe esophagitis in 1 week with a similarly pathological change seen in humans. The aim of this study was to investigate the histological changes of esophagus after bone marrow cell engraftment with bile and acid perfusion. The external pump perfusion procedure involved implantation of a microosmotic pump for esophageal perfusion. Bone marrow cells were obtained by flushing of the femur marrow, and the cell suspension was injected between the esophageal muscular and inner mucosa layer. Histological changes were determined after 4 weeks of perfusion. Proliferating cell nuclear antigen, 8-hydroxy-deoxyguanosine, manganese superoxide dismutase, and apoptosis were measured by immunohistochemical staining and TUNEL assay, respectively. Severe esophagitis was seen in both acid and bile perfusion. Bone marrow engraftment and potentiation was seen in both the acid and bile perfusion, when compared to saline controls. Glandular-like cells in submucosa, consistent with intestinal metaplasia, confirmed by Alcin Blue-PAS staining were observed after bone marrow esophageal implantation along with bile perfusion, but not with acid perfusion and controls. Bone marrow implantation in conjunction with esophageal reflux injury contributes to abnormal histological changes consistent with early Barrett's esophageal changes. Engrafted bone marrow cells proliferate under oxidative stress conditions with bile perfusion.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed1988

Progesterone secretion by corpora lutea of the isolated perfused rabbit ovary during pseudopregnancy.

An ovarian in vitro perfusion method was adapted to examine rabbit corpus luteum (CL) function during pseudopregnancy. Ovaries were perfused in vitro with tissue culture Medium 199 with or without 3% bovine serum albumin (BSA). Samples were obtained from both arterial and venous cannulae, allowing rates of progesterone secretion to be determined. Two perfusion methods were compared: a closed system in which perfusion medium continuously recirculated through the tissue, and an open system in which the ovarian vein cannula was left outside the perfusion chamber. The addition of 3% BSA was found to prevent edema and distortion of the interstitial space, and to result in increased progesterone secretion. With the closed perfusion system, the progesterone secretion rate measured over the 6-h perfusion was significantly higher on Day 11 than on Day 1 of pseudopregnancy and had declined significantly on Day 18. There was no difference in secretion rates whether the perfusion system was open or closed, and the results obtained with both systems closely approximated in vivo progesterone secretion rates. Measurements of CL tissue progesterone content before and after in vitro perfusion indicated that the changes in progesterone secretion seen during pseudopregnancy resulted from differences in the synthesis and secretion of progesterone and not from leakage of progesterone already present in the CL prior to perfusion. Taken together, these results indicate that the modified in vitro perfused rabbit ovary preparation described herein is an appropriate model to examine progesterone secretion by ovaries bearing CL.

Animals↗
PubMed1997

Regional isolated perfusion of extremities for melanoma: a 20-year experience with drugs other than L-phenylalanine mustard.

Recurrent melanoma of the extremities can lead to bulky symptomatic lesions that become difficult management problems. Treatment of these tumors with isolated limb perfusion with high dose chemotherapy may offer palliation in a number of patients. Unfortunately, the most commonly used drug, L-phenylalanine mustard, has been known to have significant associated tissue toxicity. Therefore, during the years 1976-1995, we perfused 67 limbs in 60 patients with various other drugs: 36 with dimethyltriazeno imidazole carboxamide, 6 with cisplatin, 20 with carboplatin, and 5 with thiotepa). Perfusion was performed for 16 upper extremities and 51 lower extremities using the pump oxygenator for 1 hour. Among the 60 patients, 17 were treated prophylactically for high-risk melanoma, whereas 43 were treated for local and in-transit recurrences. The technique of perfusion successfully isolated the limbs from the systemic circulation: the median leaks over time were 0.5-1.6 percent for the upper extremities, and 0.2-7.5 percent for the lower extremities. Among the 43 patients treated with therapeutic isolated limb perfusion, 11 patients (26 percent) are alive with no evidence of disease for a median of 58 months (range: 8 months to 17 years 9 months), and another 5 patients (12 percent) are alive with recurrence for a median of 45 months (range: 27 months to 10 years 7 months). Four patients required two perfusions, and two patients required three perfusions (one patient has no evidence of disease 6 years after her third perfusion for recurring in-transit disease). There were 19 complications noted after 14 of the 67 perfusions (21%): postoperative edema, 5; seroma, 4; wound separation/infection, 9; and nonfatal pulmonary embolus, 1. In our experience, aggressive treatment in selected patients with regional isolated perfusion of limbs for melanoma has provided meaningful palliation and salvage of the limbs with adequate disease-free control, and occasional survival benefit. This regional treatment modality is associated with meaningful control and with few serious complications, especially when compared with studies using L-phenylalanine mustard. This series illustrates the safety of controlling limb recurrence with this technique, even with repeat perfusions in the same patient.

Adult↗
PubMed1985

The effect of verapamil on renal function after warm and cold ischemia in the isolated perfused rat kidney.

The potential usefulness of verapamil, a calcium channel blocker to renal allograft preservation, was investigated using the isolated perfused rat kidney. Two models of ischemic injury were used. In the first model, rat kidneys were exposed to 40 min of 37 degrees C ischemia on the perfusion circuit. Addition of verapamil in doses of 2.5, 5, and 100 microM concentration to the perfusate significantly improved inulin clearance (Cin) and total sodium absorption (TNa) in the hour of reperfusion following ischemia. Regeneration of adenosine triphosphate (ATP) and total adenine nucleotide TAN levels during reperfusion following warm ischemia were also significantly higher in verapamil-treated kidneys. In the second model, rat kidneys were flushed in situ with Collins C2 solution and stored at 0 degrees C for 8 hr. After this period of cold ischemia, they were perfused on a perfusion circuit with perfusion media. Verapamil 2.5 microM was absent from both flush and perfusate (control), or added to just the flush, both the flush and perfusate, or just the perfusate. Addition of verapamil to the flush or the flush and perfusate significantly improved Cin, urine flow rate (V) and TNa during reperfusion, compared with control. Addition of verapamil to just the perfusate did not effect Cin, TNa, or V but did significantly increase RPF. These findings suggest the verapamil may protect against organ damage occurring during both warm and cold ischemia in the absence of any systemic effects and thus may be useful for renal allograft preservation.

Adenine Nucleotides↗
PubMed1994

Temperature-dependent coronary reactivity after perfusion with University of Wisconsin solution in the isolated rat heart.

The purpose of this study was to determine the effects of different temperatures of University of Wisconsin solution on the reactivity of the coronary vasculature in retrogradely perfused isolated rat hearts. Hearts were perfused for 30 min at 20 degrees C or single-flush perfused at 12 degrees C and 4 degrees C. To study both endothelium-dependent and direct effects on smooth muscle, vasodilation was induced with 5-hydroxytryptamine (5-HT) and nitroglycerin (GTN). The vasodilatory effects of 5-HT and GTN during basal conditions were completely lost and instead a vasoconstriction was observed after 30-min perfusion at 20 degrees C (5-HT: 23.7 +/- 5% before to -19.2 +/- 8% after perfusion; GTN: 33.7 +/- 5.5% before and -11.9 +/- 6% after perfusion). The same response was observed after single-flush perfusion at 12 degrees C (5-HT: 26.5 +/- 5% and -6.5 +/- 3% and GTN: 35.9 +/- 6% and -11.2 +/- 4% before and after perfusion, respectively). Single-flush perfusion at 4 degrees C did not alter the response to 5-HT and GTN (5-HT: 25.9 +/- 6% and 30.4 +/- 7% and GTN: 45 +/- 5% and 32.7 +/- 7% before and after perfusion, respectively). This study suggests that the coronary reactivity after perfusion with University of Wisconsin solution is dependent of the temperature of the solution and provides good preservation of the coronary vascular function at 4 degrees C, whereas temperatures above 12 degrees C might be detrimental.

Adenosine↗
PubMed2002

Overcoming severe renal ischemia: the role of ex vivo warm perfusion.

BACKGROUND: The ability to effectively utilize kidneys damaged by severe (2 hr) warm ischemia (WI) could provide increased numbers of kidneys for transplantation. The present study was designed to examine the effect of restoring renal metabolism after severe WI insult during ex vivo warm perfusion using an acellular technology. After warm perfusion for 18 hr, kidneys were reimplanted and evaluated for graft function. METHODS: Using a canine autotransplant model, kidneys were exposed to 120 min of WI. They were then either reimplanted immediately, hypothermically machine perfused (4 degrees C) for 18 hr with Belzer's solution, or transitioned to 18 hr of warm perfusion (32 degrees C) with an acellular perfusate before implantation. RESULTS: Warm perfused kidneys with 120 min of WI provided life-sustaining function after transplantation, whereas the control kidneys immediately reimplanted or with hypothermic machine perfusion did not. The mean peak serum creatinine in the warm perfused kidneys was 3.7 mg/dl, with the mean peak occurring on day 2 and normalizing on day 9 posttransplant. CONCLUSIONS: These results indicate that 18 hr of ex vivo warm perfusion of kidneys is feasible. Furthermore, recovery of renal function during warm perfusion is demonstrated, resulting in immediate function after transplantation. The use of ex vivo warm perfusion to recover function in severe ischemically damaged kidneys could provide the basis for increasing the number of transplantable kidneys.

Animals↗
PubMed2002

Functional recovery of preserved livers following warm ischemia: improvement by machine perfusion preservation.

BACKGROUND: Hypothermic machine perfusion preservation has the potential to relieve the current donor shortage problem by reclaiming and preserving marginal donor organs including those from viable non-heart-beating donors. A number of problems exist with the current machine perfusion technology for preserving livers, and much research is needed to determine the clinical impact of this technology in preserving non-heart-beating donor livers. METHODS: This study was conducted to compare the poststorage function and microcirculation of simple cold stored and machine perfusion preserved livers that had experienced 30 min of warm ischemia followed by a 10 hr preservation period. In an isolated rat liver perfusion model, lactate dehydrogenase activity, indocyanine green secretion, and portal pressure values were determined at major time points. An intravital microscopy was conducted to assess microcirculation. RESULTS: The results showed an increase in flow homogeneity of machine perfused livers, which correlated with the reduction in portal pressure when compared with simple cold storage (5.4+/-0.4 vs. 8.7+/-0.6 mm Hg). A reduction in lactate dehydrogenase levels in the perfusate (333+/-22 vs.103+/-8 U/L) and an increase in bile production of the machine perfused livers (4.9+/-0.5 vs. 33.2+/-1.7 microg/min/g liver) and indocyanine green secretion (11.7+/-1.7 vs. 21.2+/-2.1 Abs/g bile) were observed at all time points (mean+/-SE of final point given). Intravital microscopic examination indicated that large regions of non flow, as indicated by the absence of fluorescein isothiocyanate-labeled albumin, were observed in the simple cold stored tissue, whereas machine perfused liver showed increase flow homogeneity. Values of bile production, indocyanine secretion, and cellular damages were comparable with controls. Histologic examination confirmed that simple cold stored tissue displayed increased vacuolization, and machine perfused tissue showed regions of normal hepatic structure. CONCLUSION: These results suggest that machine perfusion for 10 hr improves both poststorage function and microcirculation while reducing cellular damage of liver tissue that has experienced 30 min of warm ischemia, when compared with simple cold storage. Further studies need to be conducted, but this study suggests that machine perfusion preservation has the potential to reclaim and preserve liver tissues after warm ischemic insult.

Animals↗
PubMed1994

Neuronal protection by intraischemic brain perfusion: an electron microscopy study in the rat.

Organ perfusion with bloodless solutions is an established clinical method for protecting the heart against ischemic damage. In our study, we evaluated the effects of intraischemic bloodless brain perfusion on postischemic ultrastructural neuronal changes in a model of severe incomplete forebrain ischemia produced by hemorrhagic hypotension combined with temporary carotid occlusion in the rat. Four groups of rats were compared. During an ischemic insult of 30 min, the brains of two groups were perfused via both external carotids with either a normosmolar normothermic magnesium-enriched perfusate (MgSO4, 30 mM; NaCl, 37 mM; mannitol, 180 mM; n = 10) or a normothermic normal saline solution (n = 9) at a rate of 6 ml/h. Two other groups (ischemia without perfusion, n = 8; no ischemia and no perfusion, n = 7) served as controls. After 30 min of ischemia, withdrawn blood for hemorrhagic hypotension was reinfused, the carotid arteries reopened, and the brains reperfused for 2 h. After perfusion-fixation, qualitative and quantitative evaluation of postischemic cell changes of hippocampal CA1 neurons was performed by electron microscopy. Brain perfusion with the magnesium-containing solution significantly protected neurons against ischemic cell changes and provided an ultrastructural pattern similar to that seen in the nonischemic control group. In contrast, brain perfusion with normal saline solution did not result in neuronal protection. We conclude that intraischemic intracarotid brain perfusion with magnesium-enriched perfusate protects hippocampal neurons significantly against ischemic cell changes in the early reperfusion period after transient severe forebrain ischemia.

Animals↗
PubMed1971

Uptake kinetics and metabolism of 7-3H-dopamine in the isolated perfused rat heart.

1. The isolated, perfused rat heart accumulates dopamine by two distinct uptake mechanisms characterized by different kinetic constrants and different patterns of metabolite production (Uptake 1: Km 0.69 x 10(-6)M and Vmax (1.45 x 10(-9) mol/g)/min; Uptake 2: Km 5.9 x 10(-4)M and Vmax (0.14 x 10(-6) mol/g)/min).2. The metabolic fate of dopamine taken up by the isolated, perfused rat heart depends on the concentration of dopamine in the perfusion medium. At a very low perfusion concentration (0.047 x 10(-10) mol/ml) most of the radioactivity is stored as unchanged dopamine and the main metabolite is noradrenaline. With increasing perfusion concentrations deamination becomes the main metabolic pathway, deaminated metabolites accounting for more than 50% of the total radioactivity after perfusion with 2,614.4 x 10(-10) mol/ml for 16 minutes. The O-methylated, and the O-methylated deaminated metabolites are of minor importance at all perfusion concentrations.3. The resistance to wash out of the dopamine taken up by the isolated, perfused rat heart is dependent on the perfusion concentration used. At a concentration of 66.9 x 10(-10) mol/ml, 50% of the total activity is washed out during an 8 min wash period. Within the same time interval there is no wash out when a perfusion concentration of 0.042 x 10(-10) mol/ml is used.4. It is concluded that the metabolic fate of dopamine taken up at various perfusion concentrations reflects the distribution of dopamine within intra- and extraneuronal compartments in the hearts.

Animals↗
PubMed1990

The metabolism of recombinant erythropoietin in the isolated perfused rat liver.

Indirect evidence points to extrarenal organs, presumably the liver, as the site of degradation of erythropoietin (EPO). The metabolism of both fully glycosylated and desialated intrinsically labelled 35S-Cysteine recombinant human erythropoietin (rhEPO) was therefore studied in isolated Wistar rat livers perfused in a recirculating mode for 180 min with a hemoglobin-free medium containing rhEPO. Perfusate and bile levels of rhEPO were measured by RIA. Total 35S-radioactivity in liver, bile and perfusate as well as non-acid precipitable radioactivity in perfusate were determined. In addition, detection of 35S-radioactivity was performed after subcellular fractionation of rat livers perfused with desialo-35S-Cysteine rhEPO. While concentrations of fully glycosylated 35S-Cysteine rhEPO did not exhibit any detectable decrease during perfusion, desialo-35S-Cysteine rhEPO was rapidly cleared from the perfusate. After 60 min of perfusion, only 32% of the initial levels of both immunoreactive rhEPO and total radioactivity remained in the perfusate. Quantitative hepatic accumulation of desialated tracer was demonstrated. Subcellular fractionation showed extensive hepatic degradation of the desialated tracer. Furthermore, during perfusion progressively larger amounts of small molecular weight degradation products of the tracer were found in the perfusate. Bile excretion of both fully glycosylated and desialated tracer was negligible. The significance of hepatic metabolism of desialo-35S-Cysteine rhEPO was supported by reduced removal of desialo-35S-Cysteine rhEPO from plasma in hepatectomized rats. It is hypothesized that continuous in vivo desialation is a crucial rate-limiting step in the degradation of circulating EPO.

Animals↗
PubMed1998

Sensitivity of kidney perfusion protocol design to physical and physiological parameters.

The introduction and removal of cryoprotective agents (CPA) to a kidney via vascular perfusion may induce changes in cell volume that are destructive to the tubular epithelial or capillary endothelial cells as well as causing significant increases in vascular resistance that compromise the perfusion process. A network thermodynamic model of the coupled osmotic, hydrodynamic and elastic properties of the kidney was applied to evaluate the sensitivity of these critical outputs to a set of physiological and perfusion variables. Simulation results suggest that in the design of perfusion protocols for CPAs such as glycerol, it may be advantageous to: (a) select a CPA with as high a cell membrane permeability as possible; (b) increase the concentration of mannitol in the perfusate to about 200 mos/kg, beyond which there is no discernible benefit; (c) when glycerol is the CPA, limit the rate of reduction in the perfusate during removal to 30 mM/min or less; (d) limit the perfusion pressure to 20-30 mm Hg, within the practical constraints of the perfusion system; (e) increase the concentration of impermeant in the perfusate to as high as 400 mos/kg, although it is recognized that this departure from plasma-like composition might impose other problems that are not considered in this model. Further, it was observed that the vascular membrane permeability plays a relatively minor role in controlling cellular osmotic injury and vascular perfusion resistance and is therefore not a critical parameter in the perfusion design process.

Animals↗
PubMed1974

The effect of vasopressin upon the vasculature of the isolated perfused rat kidney.

The timed uptake of (131)I-labelled human serum albumin was used as an index of regional perfusion in the isolated rat kidney.1. Arginine vasopressin in doses of 1, 5 and 10 muu./ml. of perfusate decreased papillary perfusion. Total renal perfusion was decreased only by the 5 muu. dose.2. Ornithine-8-vasopressin in doses of 5 and 10 muu./ml. of perfusate decreased papillary perfusion. Total renal perfusion was decreased only by the 10 muu. dose.3. When the relative viscosity of the perfusate was increased to a value of 2.0 from the control value of 1.7, both papillary perfusion and total renal perfusion were reduced.4. Arginine vasopressin further reduced papillary flow in kidneys perfused with high viscosity artificial plasma.

Animals↗
PubMed1997

Pulmonary embolism: detection with MR perfusion imaging of lung--a feasibility study.

PURPOSE: To evaluate the feasibility of magnetic resonance (MR) perfusion imaging in the human lung to help detect perfusion defects distal to suspected pulmonary embolism. MATERIALS AND METHODS: Seven patients suspected of having pulmonary embolism first underwent ventilation-perfusion lung scintigraphy followed by MR perfusion imaging with rapid acquisition of two sets of dynamic images in the coronal and transaxial planes. A bolus of 0.05 mmol per kilogram of body weight gadopentetate dimeglumine or gadodiamide was administered. Single images obtained in each section that showed peak signal intensity from the first passage of contrast material were evaluated visually. An analysis of change in signal intensity over time was performed both on a pixel-by-pixel basis and in selected regions of interest. RESULTS: In the seven patients, a total of 18 regions of lung tissue with perfusion defects were shown on the ventilation-perfusion scans. In 16 of these regions, MR perfusion images showed a reduced peak signal intensity during first passage of the contrast agent. Perfusion defects could be detected in both the coronal and the transaxial planes on MR perfusion images. CONCLUSION: MR perfusion imaging was feasible for detection of perfusion defects distal to a pulmonary embolism.

Adult↗
PubMed1985

Crystalloid and perfluorochemical perfusates in an isolated working rabbit heart preparation.

Krebs-Henseleit buffer (KH) and a perfluorochemical (FC-43) were compared as perfusates in an isolated working rabbit heart preparation. Both perfusates were oxygenated in an identical manner using an infant bubble oxygenator. After 60 min of perfusion, no difference could be detected in the ratio of wet to dry heart weight between KH- and FC-43-perfused hearts (KH, 6.25 +/- 0.3; FC-43, 5.99 +/- 0.20). Left ventricular systolic pressure, maximal rate of left ventricular pressure rise, mean aortic systolic pressure, cardiac output, aortic flow, left ventricular power, and myocardial O2 consumption (MVO2) were significantly higher in FC-43-perfused hearts throughout the time of perfusion. However, there were no differences in resistance to cardiac output and heart rate. In KH- and FC-43-perfused hearts, MVO2 and left ventricular power were closely correlated (KH, r = 0.793; FC-43, r = 0.831). Significantly higher coronary flow of KH-perfused hearts could be attributed to the lower viscosity of KH (1.05 Pa . s) compared with FC-43 (1.91 Pa . s). Increased O2 extraction during KH perfusion could not compensate for low O2-carrying capacity of KH buffer (345 compared with 705 nmol O2 X ml-1 in FC-43 emulsion). A postischemic increase of coronary flow was observed only in FC-43-perfused hearts (28%). These results demonstrate a different response of perfused heart preparations to FC-43 and KH buffer.

Animals↗
PubMed1975

Influence of perfusion rate and compliance on esophageal manometry.

The accuracy of esophageal manometry using the conventional perfused three-lumen catheter depends on the proper choice of the perfusion rate. Previous investigators have used a wide range of perfusion rates without considering the compliance of the transducer-catheter assembly as a variable in the selection of the perfusion rate for the hydraulic systems. We present a relationship relating the perfusion rate and the compliance which specifies the minimum adequate perfusion rate for a given transducer-catheter assembly. This approach explains apparent discrepancies in the literature regarding the proper rate of perfusion for accurate measurement of esophageal contractions. Esophageal motility tests with 10 subjects confirmed the accuracy of manometric tests at the prescribed perfusion rate (1.25 ml/min) since they compared well with intraluminal pressures measured directly with a Honeywell intraesophageal transducer. The effect of perfusion rate on the apmlitude of esophageal contraction was also investigated and it is shown that high perfusion rates result in increased amplitudes of contraction. Furthermore, at large perfusion rates a large volume of liquid builds up in the esophagus. This fluid accumulation could possibly be responsible for the increased amplitudes of contraction.

Adult↗
PubMed1995

Continuous measurement of ATP by 31P-NMR in term human dually perfused placenta in vitro: response to ischemia.

ATP was examined in dually perfused term human placentas by using 31P-nuclear magnetic resonance (NMR) spectroscopy. 31P-NMR spectra were acquired every 30 min starting approximately 30 min after establishing fetal and maternal perfusions, and maternal perfusate samples were obtained to monitor glucose utilization, lactate production, and human chorionic gonadotropin (hCG) and human placental lactogen (hPL) release. In continuous-perfusion experiments, placentas were perfused as long as 10 h. ATP increased and Pi fell after initiation of perfusion. Fetal volume loss was < 2 ml/h, and constant production of hCG, hPL, and lactate as well as constant utilization of glucose were observed. In additional experiments, ischemia was produced by halting maternal and fetal perfusion pumps after a 2-h control period. After 2, 3, or 4 h of ischemia, ATP decreased 46 +/- 17, 51 +/- 5, and 85% of control, respectively. When perfusion was reinitiated, ATP increased and was maintained for the duration of the experiment (an additional 2 h). Recovery of ATP after reperfusion was not paralleled by recovery in glucose utilization, lactate production, or hPL and hCG release. However, during the reperfusion period, fetal pressure was < 70 mmHg and fetal volume loss was < 2 ml/h. These investigations suggest that the dually perfused human placental lobule can maintain ATP for > or = 10 h. Although the perfused human placenta recovers ATP and maintains fetal perfusion volume after ischemia lasting up to 4 h, utilization of glucose, production of lactate, and production and release of hCG and hPL are impaired.

Adenosine Triphosphate↗
PubMed2000

Correlation between ventilation and perfusion determines VA/Q heterogeneity in endotoxemia.

Endotoxin increases ventilation-to-perfusion ratio (VA/Q) heterogeneity in the lung, but the precise changes in alveolar ventilation (VA) and perfusion that lead to VA/Q heterogeneity are unknown. The purpose of this study was to determine how endotoxin affects the distributions of ventilation and perfusion and the impact of these changes on VA/Q heterogeneity. Seven anesthetized, mechanically ventilated juvenile pigs were given E. coli endotoxin intravenously, and regional ventilation and perfusion were measured simultaneously by using aerosolized and injected fluorescent microspheres. Endotoxemia significantly decreased the correlation between regional ventilation and perfusion, increased perfusion heterogeneity, and redistributed perfusion between lung regions. In contrast, ventilation heterogeneity did not change, and redistribution of ventilation was modest. The decrease in correlation between regional ventilation and perfusion was responsible for significantly more VA/Q heterogeneity than were changes in ventilation or perfusion heterogeneity. We conclude that VA/Q heterogeneity increases during endotoxemia primarily as a result of the decrease in correlation between regional ventilation and perfusion, which is in turn determined primarily by changes in perfusion.

Animals↗
PubMed2002

Microdialysis in human skeletal muscle: effects of adding a colloid to the perfusate.

Microdialysis catheters (CMA-60 with a polyamide dialysis membrane; 20,000-molecular wt cutoff) were either immersed in an external medium or were inserted in the quadriceps femoris muscle of healthy subjects, using perfusate with or without dextran 70. Varying the position of the outflow tubing induced changes in hydrostatic pressure. The sample volumes were significantly smaller in catheters perfused without a colloid compared with those perfused with a colloid [11-50% (in vitro) and 8-59% (in vivo) lower than in colloid-perfused catheters with the same position of the outflow tubing]. The sample volumes were also significantly smaller when the dialysis membrane was influenced by maximal hydrostatic pressure (above position) compared with minimal hydrostatic pressure (below position) [7-38% (in vitro) and 3-46% (in vivo) lower than in catheters in the below position with the same perfusion fluid]. In vivo, glucose concentration at a perfusion flow rate of 0.33 microl/min was higher when the catheters were perfused without a colloid [18-28% higher than in colloid-perfused catheters with the same position of the outflow tubing (P < 0.001)] than with a colloid. A corresponding difference also tended to occur with lactate, glycerol, and urea. At 0.16 microl/min, the glucose concentration was the same irrespective of whether fluid loss had been counteracted by colloid inclusion or by lowering of outlet tubing. The mechanism behind the observed concentration difference is thought to be a higher effective perfusion flow rate when fluid loss is prevented at low-perfusion flows. This study shows that fluid imbalances can have important implications for microdialysis results at low-perfusion flow rates.

Adult↗