Gravity Perfusion Research Articles

Zero-Intrarenal Pressure Percutaneous Nephrolithotomy for One-Stage Treatment of Non-Acute Infectious Calculous Pyonephrosis: A Strategy to Avert Sepsis.

Purpose: To evaluate the efficacy and safety of a novel zero-intrarenal pressure (IRP) percutaneous nephrolithotomy (PCNL) technique for one-stage treatment of non-acute infectious calculous pyonephrosis. Patients and Methods: This retrospective study analyzed 12 patients (4 males, 8 females; mean age 56.4 years) who underwent zero-IRP PCNL. The technique utilized a double-sheath vacuum suction system, with the outer sheath allowing for gravity irrigation and the inner sheath facilitating continuous suction. Keeping the height of gravity perfusion at the level of the kidney inherently prevented high IRP and achieved zero-IRP PCNL, even when stone fragments obstructed the suction channel. Results: The procedure demonstrated a high initial stone-free rate of 75%, improving to 91.7% after 1 month. The average operative time was 50.7 minutes. The mean hemoglobin drop was 6.1 g/L, managed without transfusions. Complications were minimal, with low-grade fever in two patients. No significant intraoperative or postoperative complications, such as sepsis, were noted. Conclusions: The zero-IRP PCNL technique, characterized by its double-sheath vacuum suction system and zero-pressure gravity perfusion, shows promise in safely and effectively managing non-acute infectious calculous pyonephrosis. Preliminary results are encouraging, but further research with larger sample sizes is essential for broader clinical validation.

A new strategy for the decellularization of whole organs by hydrostatic pressure.

Tissue engineering has been able to develop novel decellularization-recellularization techniques, which facilitates the research for the generation of functional organs. This is based in the initial obtention of the organ's extracellular matrix (ECM). Therefore, any improvement in the decellularization process would have a positive impact in the results of the recellularization process. Nevertheless, commonly the methods and equipment employed for this process are expensive and thus limit the access of this technique to various research groups globally. To develop a decellularization technique with the exclusive use of hydrostatic pressure of detergent solutions, to have an easily accessible and low-cost technique that meets the basic requirements of acellularity and functionality of the ECM. This experimental study was performed in 10 male Wistar rats, obtaining the liver to carry out serial washes, with 1%, 2%, and 3% Triton X-100 solutions and 0.1% SDS. The washes were performed by using a gravity perfusion system (GPS), which assured us a continuous hydrostatic pressure of 7.5 mmHg. The obtained ECM was processed using stains and immunostaining to determine the residual cell content and preservation of its components. The staining showed a removal of cellular and nuclear components of approximately 97% of the acellular ECM, with an adequate three-dimensional pattern of collagen and proteoglycans. Furthermore, the acellular ECM allowed the viability of a primary hepatocyte culture. The use of the GPS decellularization technique allowed us to obtain an acellular and functional ECM, drastically reducing experimentation costs.

Comparison of Perfusion Pressure in Aorta Using High-Pressure Perfusion and Gravity Perfusion During the Kidney Transplant Procedure

Organ perfusion is an element of organ donation aimed at cooling the organ, washing out morphotic elements, and creating favorable conditions for the storage and transport of organs. Depending on the method used, perfusion is performed under gravity perfusion (GP) or perfusion under high pressure (HPP). This study aimed to measure the pressure of the perfusion fluid in the abdominal aorta during the use of GP and HPP. The study was performed during 35 organ procurements from deceased donors. The direct proportional increase of pressure in the aorta, depending on the applied perfusion method, was observed. GP was on average 37.8 mm Hg; using a pressure of 50 mm Hg in the HPP, an average of 57 mm Hg was obtained, and using a pressure of 200 mm Hg, 99.4 mm Hg was obtained. The study found that during the application of GP, the pressure generated in the abdominal aorta is low, which may lead to inadequate perfusion of organs. HPP is a faster method that leads to a proper perfusion of the procured organs and is also a safe method because, despite the use of high pressure, no damage to the transplanted kidneys was observed.

Microfluidic flow-cell with passive flow control for microscopy applications.

We present a fast, inexpensive and robust technique for constructing thin, optically transparent flow-cells with pump-free flow control. Using layers of glass, patterned adhesive tape and polydimethylsiloxane (PDMS) connections, we demonstrate the fabrication of planar devices with chamber height as low as 25 μm and with millimetre-scale (x,y) dimensions for wide-field microscope observation. The method relies on simple benchtop equipment and does not require microfabrication facilities, glass drilling or other workshop infrastructure. We also describe a gravity perfusion system that exploits the strong capillary action in the flow chamber as a passive limit-valve. Our approach allows simple sequential sample exchange with controlled flow rates, sub-5 μL sample chamber size and zero dead volume. We demonstrate the system in a single-molecule force spectroscopy experiment using magnetic tweezers.

Brimonidine enhances inhibitory postsynaptic activity of OFF- and ON-type retinal ganglion cells in a Wistar rat chronic glaucoma model

Glaucoma is a multifactorial disease in which retinal ganglion cells (RGCs) undergo excitotoxic damage, leading to their degeneration. The α2-adrenoceptor (α2-AR) agonist brimonidine exerts a neuroprotective effect by regulating postsynaptic excitatory N-methyl-D-aspartate (NMDA) receptor activity in RGCs. However, researchers have not clearly determined whether or how brimonidine regulates inhibitory synaptic transmission in rat models of chronic glaucoma. Whole-cell voltage-clamp and current-clamp recordings were performed in ON- and OFF-type RGCs in retinal slices. Brimonidine directly and acutely enhanced γ-aminobutyric acidergic (GABAergic) transmission mediated by ionotropic GABAA receptors in ON- and OFF-type RGCs in rat retinal slices; this effect occurred at the synaptic terminals and was independent of action potentials and multi-synaptic connections. The highly selective α2-AR antagonist yohimbine blocked the effects of brimonidine. Regarding the postsynaptic GABA receptor sensitivity, brimonidine also increased the amplitude of the GABA-induced current. Additionally, compared to RGCs from the control group, the frequencies and amplitudes of spontaneous excitatory postsynaptic currents (sEPSCs) and miniature excitatory postsynaptic currents (mEPSCs) did not change after brimonidine gravity perfusion. Brimonidine significantly decreased the spontaneous firing frequency of rat RGCs with intact synaptic inputs and decreased the resting membrane potential of RGCs, changes that were blocked by the highly selective GABAA receptor antagonist SR95531. SR95531 alone increased spontaneous action potentials and the resting membrane potential. Based on these findings, an α2-AR agonist facilitated the frequency of the GABAergic inhibitory postsynaptic currents (IPSCs), directly increased the amplitude of the postsynaptic GABA-induced current (GABA receptor reactivity/sensitivity), suppressed the firing frequency of spontaneous action in RGCs with intact synaptic inputs and decreased the resting membrane potential of RGCs, thus deactivating RGCs from the neural network level and reducing the excitotoxic damage occurring during the pathological process of chronic glaucoma.

Whole-globe biomechanics using high-field MRI

The eye is a complex structure composed of several interconnected tissues acting together, across the whole globe, to resist deformation due to intraocular pressure (IOP). However, most work in the ocular biomechanics field only examines the response to IOP over smaller regions of the eye. We used high-field MRI to measure IOP induced ocular displacements and deformations over the whole globe. Seven sheep eyes were obtained from a local abattoir and imaged within 48 h using MRI at multiple levels of IOP. IOP was controlled with a gravity perfusion system and a cannula inserted into the anterior chamber. T2-weighted imaging was performed to the eyes serially at 0 mmHg, 10 mmHg, 20 mmHg and 40 mmHg of IOP using a 9.4 T MRI scanner. Manual morphometry was conducted using 3D visualization software to quantify IOP-induced effects at the globe scale (e.g. axial length and equatorial diameters) or optic nerve head scale (e.g. canal diameter, peripapillary sclera bowing). Measurement sensitivity analysis was conducted to determine measurement precision. High-field MRI revealed an outward bowing of the posterior sclera and anterior bulging of the cornea due to IOP elevation. Increments in IOP from 10 to 40 mmHg caused measurable increases in axial length in 6 of 7 eyes of 7.9 ± 5.7% (mean ± SD). Changes in equatorial diameter were minimal, 0.4 ± 1.2% between 10 and 40 mmHg, and in all cases less than the measurement sensitivity. The effects were nonlinear, with larger deformations at normal IOPs (10–20 mmHg) than at elevated IOPs (20–40 mmHg). IOP also caused measurable increases in the nasal-temporal scleral canal diameter of 13.4 ± 9.7% between 0 and 20 mmHg, but not in the superior-inferior diameter. This study demonstrates that high-field MRI can be used to visualize and measure simultaneously the effects of IOP over the whole globe, including the effects on axial length and equatorial diameter, posterior sclera displacement and bowing, and even changes in scleral canal diameter. The fact that the equatorial diameter did not change with IOP, in agreement with previous studies, indicates that a fixed boundary condition is a reasonable assumption for half globe inflation tests and computational models. Our results demonstrate the potential of high-field MRI to contribute to understanding ocular biomechanics, and specifically of the effects of IOP in large animal models.

The Quaternary Lidocaine Derivative, QX-314, Exerts Biphasic Effects on Transient Receptor Potential Vanilloid Subtype 1 Channels In Vitro

Transient receptor potential vanilloid subfamily member 1 (TRPV1) channels are important integrators of noxious stimuli with pronounced expression in nociceptive neurons. The experimental local anesthetic, QX-314, a quaternary (i.e., permanently charged) lidocaine derivative, recently has been shown to interact with and permeate these channels to produce nociceptive and sensory blockade in animals in vivo. However, little is known about the specific interactions between QX-314 and TRPV1 channels. Thus, the authors examined the mechanistic basis by which QX-314 acts on TRPV1 channels. The authors conducted an in vitro laboratory study in which they expressed TRPV1 and TRPV4 channels in Xenopus laevis oocytes and recorded cation currents with the two-electrode voltage clamp method. They used confocal microscopy for Ca²⁺ imaging in TRPV1 transient transfected tsA201 cells. Drugs were bath-applied by gravity perfusion. Statistical analyses were performed using Student t test, ANOVA, and post tests as appropriate (P < 0.05). QX-314 activated TRPV1 channels at 10, 30, and 60 mM (0.4 ± 0.1%, 3.5 ± 1.3%, and 21.5 ± 6.9% of normalized peak activation, respectively; mean ± SEM; n = 12) but not TRPV4 channels (P < 0.001). Activation by QX-314 was blocked by the TRPV1 antagonist, capsazepine (100 μM). QX-314 (60 mM) activation and blockade by capsazepine was also demonstrated in Ca²⁺ imaging studies on TRPV1-expressing tsA201 cells. At subactivating concentrations (less than 1 mM), QX-314 potently inhibited capsaicin-evoked TRPV1 currents with an IC₅₀ of 8.0 ± 0.6 μM. The results of this study show that the quaternary lidocaine derivative QX-314 exerts biphasic effects on TRPV1 channels, inhibiting capsaicin-evoked TRPV1 currents at lower (micromolar) concentrations and activating TRPV1 channels at higher (millimolar) concentrations. These findings provide novel insights into the interactions between QX-314 and TRPV1 and may provide an explanation for the irritant properties of intrathecal QX-314 in mice in vivo.

Whole-cell Voltage Clamp Measurements of Anthrax Toxin Pore Current

Protective antigen (PA) of anthrax toxin binds cellular receptors and forms pores in target cell membranes, through which catalytic lethal factor (LF) and edema factor (EF) are believed to translocate to the cytoplasm. Using patch clamp electrophysiological techniques, we assayed pore formation by PA in real time on the surface of cultured cells. The membranes of CHO-K1 cells treated with activated PA had little to no electrical conductivity at neutral pH (7.3) but exhibited robust mixed ionic currents in response to voltage stimuli at pH 5.3. Pore formation depended on specific cellular receptors and exhibited voltage-dependent inactivation at large potentials (>60 mV). The pH requirement for pore formation was receptor-specific as membrane insertion occurs at significantly different pH values when measured in cells specifically expressing tumor endothelial marker 8 (TEM8) or capillary morphogenesis protein 2 (CMG2), the two known cellular receptors for anthrax toxin. Pores were inhibited by an N-terminal fragment of LF and by micromolar concentrations of tetrabutylammonium ions. These studies demonstrated basic biophysical properties of PA pores in cell membranes and served as a foundation for the study of LF and EF translocation in vivo.

Safety and efficacy of living donor liver preservation with HTK solution

Background In living donor liver transplantation (LDLTx) organ procurement is usually well controlled, and allows to assess liver preservation and graft function under standardized conditions. Because publications on histidine-tryptophan-ketoglutarate (HTK) solution are limited, we prospectively studied its safety and efficacy in a consecutive series of LDLTx. Methods Twenty-four patients received 22 right, 1 left, and 1 left lateral lobe graft. Liver preservation was done by gravity perfusion with HTK through portal vein, and hepatic artery, and flushing of bile ducts. Total ischemia time was 191 ± 68 minutes. Results There was no primary nonfunction, and all partial liver grafts showed good recovery: peak aspartate aminotransferase 577 U/L, total bilirubin 15.15 mg/dL, and partial thromboplastin time 49.37 seconds. One graft was lost from parenchymal fracture secondary to portal hyperperfusion after 6 days, and the patient was salvaged with retransplantation. Thirty-day mortality, including sudden cardiac death, pancreatitis, and hepatic artery rupture, was not related to graft dysfunction. Eight of 24 recipients developed early biliary leakage. There was no late ischemic type biliary lesion. Conclusion These results confirm that HTK solution is safe and effective when used in LDLTx. Potential advantages of HTK in comparison to other preservation solutions are low potassium concentration, low viscosity, no particles, in situ perfusion, no need to flush before reperfusion, improved biliary protection, better recovery of microcirculatory changes, ready to use, and lower costs. Because the risk–benefit ratio is of particular importance in LDLTx the use of HTK solution should be encouraged.

SAFETY AND EFFICACY OF LIVING DONOR LIVER PRESERVATION WITH HTK SOLUTION

P44 Aims: Organ procurement in living donor liver transplantation (LDLTx) is usually well controlled, and allows to assess the quality of liver preservation as well as early graft function under standardized conditions. Since publications on histidine-tryptophan-ketoglutarate solution (HTK) are limited, we prospectively studied its safety and efficacy in LDLTx. Methods: This consecutive series included 23 patients (20 adults, 3 children; age 9 mo-61 yr), suffering from end-stage cirrhosis (16), malignant liver tumors (6), and acute hepatic failure (1), respectively. All donors (age 22-69 yr) had normal liver function tests, including six with steatosis of 5-20 %. The donor operation was performed by the same surgeon, and resulted in 21 right lobes, one left lobe, and one left lateral graft (graft weight 836±213 g). Liver preservation was done in a standard fashion by gravity perfusion with HTK, starting in situ through the portal vein (4.6±1.0 L), and continued on the backtable with infusion via the hepatic artery (1.0±0.5 L), for 10 min each to allow for adequate electrolyte equilibration. Aditionally, the bile ducts were flushed with HTK. Results: First and second warm ischemia times were <1 min, and 39±15 min, respectively; total ischemia time was 195±66 min. There was no primary non-function in this series, and all liver grafts showed good recovery with peak aspartate aminotransferase 589±498 U/L, total bilirubin 15.94±8.29 mg/dL, and partial thromboplastin time 49.90±9.58 sec. One graft was lost from parenchymal rupture secondary to portal hyperperfusion, and the patient was successfully retransplanted after six days. 30-day mortality was 13 %, and included pancreatitis, hepatic artery rupture, and sudden cardiac death. 7/23 recipients developed early biliary leakage after 8-45 d from the resectional surface, and following multiple duct reconstructions. There was no late ischemic type biliary complication. Conclusions: These results confirm earlier observations that HTK solution is safe and effective, also when used in LDLTx. Potential advantages of HTK in comparison to other preservation solutions are: low potassium concentration, low viscosity, high flow, fast cooling, ready to use, no particles, in situ perfusion, no flush before reperfusion, improved biliary protection, better recovery of microcirculatory changes, and lower costs. Since the risk-benefit ratio is of particular importance in LDLTx the use of HTK solution should be encouraged.

High-pressure perfusion versus gravity perfusion in liver harvesting: results from a prospective randomized study

High-pressure perfusion versus gravity perfusion in liver harvesting: results from a prospective randomized study

Heparin and phentolamine combined, rather than heparin alone, improves hepatic microvascular procurement in a non-heart-beating donor rat-model.

Improvement of organ procurement from non-heart-beating donors (NHBDs) could increase the donor organ pool for liver transplantation. Whether anti-coagulative and anti-vasospastic substances can improve hepatic microvascular preservation from NHBDs is unknown. In donor rats which were pretreated with either heparin (n = 6) or heparin combined with phentolamine (n = 7) 10 min prior to cardiac arrest, the extent and homogeneity of hepatic microvascular reperfusion was assessed at the end of a 60-min period of cardiac arrest using in situ fluorescence microscopy. Non-pretreated animals with cardiac arrest for 60 min served as controls (n = 6). In the non-treated NHBDs, arterial gravity perfusion of 100 cm H2O with HTK-solution led to a hepatic acinar reperfusion of only approximately 22 % with a remarkably diminished sinusoidal density. Application of heparin prior to cardiac arrest resulted in a two-fold, but insignificant increase of acinar perfusion and sinusoidal density with a still considerable heterogeneity of both parameters. Livers of NHBDs that additionally received phentolamine exhibited significantly increased values of both acinar perfusion and sinusoidal density. Phentolamine was found to reduce heterogeneity of organ microperfusion. Thus, our results indicate that the combined application of heparin and phentolamine is a useful additive for optimizing the quality of organs harvested from NHBDs.

Effect of warm ischemia time and organ perfusion technique on liver microvascular preservation in a non-heart-beating rat model.

Current organ shortage has led to a reconsideration of non-heart-beating cadaveric donation. We assessed the effectivity of dual, i.e., arterial and portal-venous versus exclusive, arterial gravity perfusion for procurement of rat livers after 30 min and 60 min of cardiac arrest, analyzing the rate and homogeneity of microvascular perfusion by in situ fluorescence microscopy. After 30 min of cardiac arrest, a nearly 100% recovery of acinar perfusion with a sinusoidal density not significantly different from that of normal, nonischemic livers was achieved by dual gravity perfusion. Prolongation of cardiac arrest to 60 min caused an almost 50% deficit of acinar and sinusoidal perfusion (P<0.05) with a concomitant 2-3-fold increase of heterogeneity of hepatic microperfusion. Regardless of the warm ischemic time period, dually perfused livers exhibited significantly (P<0.05) higher rates of both acinar and sinusoidal perfusion with increased homogeneity of microcirculation when compared with exclusive arterial perfusion. These data underline the need and benefit of dual perfusion as well as the limitation of warm ischemic tolerance to 30 min for safe liver procurement of non-heart-beating donors.

Gravity perfusion versus high-pressure perfusion in kidney transplantation: results from a prospective randomized study

HE VIABILITY of a kidney graft depends on several factors that can be classified as donor-dependent (DDF), recipient-dependent (RDF), or iatrogenic (IF). Among the latter, we distinguish six variables: therapy; surgical technique; preservation method; perfusion solution; type of perfusion; and perfusion technique. Several studies have focused on DDF, RDF, and some iatrogenic factors, but little is known about the effects of perfusion techniques and flow rate on organ viability in the clinical field. During donor operation, the in situ kidney is commonly perfused by a gravity-hydrostatic pressure of 75 to 100 cm H2O (gravity perfusion [GP]). In recent years, some investigators have advocated an apparently more physiologic technique in which perfusion solution is flushed under an additional pressure of 100 mm Hg (high-pressure perfusion [HPP]). The rationale is to create a mean pressure similar to that present in the arterial system in normal conditions, with the aim to perfuse better the small parenchymal vessels. This prospective randomized study was carried out to compare GP vs HPP in terms of outcome on early graft function after kidney transplantation.

Randomized study on in situ liver perfusion techniques: Gravity perfusion VS high-pressure perfusion

T HE VIABILITY of the donor liver depends on many factors such as perfusion techniques, perfusion solution and preservation methods. To date a number of studies have focused on perfusion solutions and preservation methods, but little is known about the effects of perfusion techniques and flow rate on organ viability in the clinical setting. In situ the liver can be easily perfused by a gravityidrostatic pressure perfusion of 75 to 100 cm H20. However some authors have advocated a more physiologic method in which the fluid is flushed under pressure (100 mm Hg) similar to the mean arterial blood pressure with the advantage of perfusing the small intrahepatic vessels, particularly those of the biliary tree, reducing post-transplantation ischemic damage and biliary complications. On the other hand, excessively high pressures would cause irreversible organ damage. To assess which in situ liver perfusion technique has the best outcome on early graft function after liver transplant, multiorgan donors were randomized to receive gravity perfusion or high-pressure perfusion.

Immunopathological observations after xenogeneic liver perfusions using donor pigs transgenic for human decay-accelerating factor.

Donor pigs transgenic for human decay-accelerating factor (hDAF) were used in a xenogeneic ex vivo liver perfusion model to study the effect of this modification on the development of hyperacute rejection. Three transgenic pigs were hepatectomized after hypothermic portal and transaortal gravity perfusion. Livers from six nontransgenic pigs served as controls. All livers were perfused for 3 hr with human blood from two donors diluted to a hematocrit of 30%. Particular importance was placed on the use of an optimal perfusion technique incorporating the floating suspension of the organs in a waterbath and intermittent external pressurization. Biochemical, physiological, and immunological parameters were assessed. Tissue specimens taken before and after perfusion were analyzed using routine histology, electron microscopy, and immunohistology. Complement activation was more pronounced in the control group. AP50 and CH50 values fell to about 60% of the initial levels in control experiments, whereas they remained at 80% of the initial levels during perfusion of hDAF livers. After 180 min, pig tumor necrosis factor alpha levels were 7862+/-1645 pg/ml for unmodified livers and 2830+/-734 pg/ml in the hDAF group. Human tumor necrosis factor alpha levels were similar in both groups. Control livers showed marked morphological alterations and distinct deposition of complement factors, whereas livers expressing hDAF showed no signs of hepatocellular necrosis and almost no complement deposition beyond C3 activation. These results confirm that the transgenic expression of the human complement regulatory protein hDAF reduces complement activation and prevents hyperacute rejection in a xenogeneic liver perfusion model over the 3-hr evaluation period used in this study.

PROLONGATION OF THE KIDNEY PRESERVATION PERIOD BY SIMPLE COLD STORAGE UP TO 72 HOURS BY HUMAN ATRIAL NATRIURETIC PEPTIDE

To prolong the preservation period of donor kidneys, we tried to evaluate the effect of human atrial natriuretic peptide (hANP), which has vasodilator, natriuretic, and GFR-increasing effects. Autotransplantations were successful in 6 of 8 hANP-treated cases, but only one of 7 untreated cases (P less than 0.05) was successful. When removed kidneys were perfused prior to preservation, the gravity perfusion time was shorter in hANP-treated kidneys, resulting in rapid cooling. Renal biopsy 1 hr after transplantation revealed normal histology in the hANP-treated kidneys while a remarkable capillary collapse occurred in controls. A hANP-like immunoreactivity contents of biopsied tissue in the hANP-treated kidneys showed a higher value than in the controls, and cyclic GMP contents were also higher in the hANP-treated kidneys. Microangiography showed complete clarity, down to the peripheral vessels, in the hANP-treated kidneys, but not in the controls. Thus, the present study suggests that hANP is useful for prolonging the preservation time of donor kidneys.

Gravity Cavernosometry—a Simple Diagnostic test for Cavernosal Incompetence

The papaverine test has been widely used as a diagnostic procedure in erectile impotence. However, when patients do not achieve full erection on the test, it is necessary to differentiate between insufficient inflow and excessive outflow. Gravity cavernosometry is a method designed to evaluate the pressure responses in the corpora when they are subjected to a constant infusion pressure. The infusion flow is of minor significance. The intracavernous pressure (ICP) was measured in cadavers, in psychogenically impotent patients and in patients with arteriogenic impotence, following administration of papaverine and gravity perfusion. During perfusion in cadavers and in psychogenic patients, the ICP showed values above 110 cm H2O, while in arteriogenic patients the values ranged from 30 to 141 cm H2O. In the arteriogenic group, 11/20 patients had an ICP lower than 110 during perfusion. There was no correlation between the pre-perfusion pressure and the final pressure with perfusion. Gravity cavernosometry is a simple, cost-effective and reliable method for the assessment of corporeal competence.

Constant-Pressure Coronary Artery Perfusion during Aortic Valve Operations

We considered the theoretical differences between the normal relationships of coronary blood flow and perfusion pressure in the working heart and those obtained with continuous, steady-flow perfusion by a roller pump during aortic valve replacement. Steady pump perfusion should deliver less blood flow to the endocardium because: 1. For the same mean artery perfusion pressure, the average coronary blood flow is less with constant-flow pump perfusion. 2. With constant pump perfusion, pressure would be excessively high during systole, and during diastole it would be significantly lower than the mean perfusion pressure. Instantaneous pressure and flow were measured in the left coronary artery in 8 patients undergoing aortic valve replacement, employing either roller pump perfusion or a gravity flow system to provide a steady pressure source. Although we did not attempt to demonstrate improved endocardial flow, the mean left coronary flow was always greater with gravity perfusion (297 versus 153 ml/min), lending support to the theoretically proposed differences between the two perfusion methods.

Simple Method for Monitoring Flow Rate during Gravity Perfusion

Simple Method for Monitoring Flow Rate during Gravity Perfusion