Stop-flow perfusions

Pharmacokinetic Principles 33 Dose-Response Relationship 34 Intraperitoneal Application 34 Intra-arterial Application 34 Isolated Perfusion Techniques Application Techniques 35 Intracavitary Application 35 Intra-arterial Infusion 36 Regional Perfusion Techniques Stop-Flow Perfusions 36 Isolated Extremity Perfusion (ILP) 37 Hyperthermic Peritoneal Perfusion (HIPEC) 38 Clinical Indications 38 Pancreas Carcinoma 38 Bronchial Carcinoma 39 Extremity Sarcoma 40 Peritoneum 41 Surgical Technique 41 Rationale 42 Clinical Results 43 References 44 Further Reading 45... 

To exemplify the benefit of isolated perfusion techniques our group compared pharmacokinetic data achieved by high-dose intravenous chemotherapy versus isolated abdominal perfusion using a stop-flow perfusion technique. Details of the techniques of this form of application are given later in this chapter. This special technique has shown promising efficacy in patients with heavily pre-treated, recurrent peritoneal metastatic ovarian cancer. 

Figure 4.11 Effect of glutathione on the reduction of myocardial Na/K ATPase activity associated with Ischaemia and reperfuslon. Isolated rat hearts were perfused in the Langendorff mode with oxygenated Tyrode s solution for a control period of 10 min. This was immediately followed by a 60 min period of global, stop-flow ischaemia and 5 min subsequent reperfuslon. Glutathione (GSH) (1 mM) was added to the perfusion fluid 5 min prior to the onset of Ischaemia and throughout the reperfuslon period. The data are presented as means standard errors of the means (n = 6).

Impose global no-flow ischemia for 25 min by completely stopping coronary perfusion (see Note 7). 

As with all immunological assay formats, antigen diffusion is a major issue in the speed of immunochromatographic assays. This limitation has been attacked in several ways. One is to incubate antigen and antibody prior to injection into the column [29,37]. Another is to incorporate a stop-flow step in the method to allow incubation in the column [29]. The use of microcolumns made of perfusive packing materials, with small diffusion distances and high surface areas, is still another way to overcome these difficulties [38]. 

Now consider a more realistic situation, where the tumor vessels are 200 /urn apart and uniformly perfused, but Pi has increased in the center so that fluid extravasation, and hence convective transport of macromolecules across vessels, has stopped. In such a case the only way macromolecules extravasate in the center is by the slow process of diffusion across vessel walls. Also, they can reach the center from the periphery (where is near zero) by interstitial diffusion. As stated earlier, if the distance between the center and periphery is — 1 mm, it would take days for them to get there, and if it is 1 cm, it would take months (Clauss and Jain, 1990). If, owing to cellular proliferation, the central vessels have collapsed completely, then there is no delivery of macromolecules by blood flow to the necrotic center (Jain, 1988 Baxter and Jain, 1990). In such a case there are no molecules available for extravasation by diffusion across the vessel wall, and consequently the central concentration would be even lower (Baxter and Jain, 1990). However, once the molecules have arrived there, the central region may serve as a reservoir for slow release later when the periphery has been cleared by plasma. 

Figure 1 Schematic diagram cf the in vitro capillary perfusion system. S 50 ml plastic syringe containing protein or antibody solution, antiocagulated whole blood or washed platelet suspension P piston driven by syringe pump SC 3-v ay stop-cock J joint in silicone tubing C glass capillary (C.80 or 0.56 mm i.d.) F direction of blood flow T plastic tube for blood collection R rinsing buffer from a reservoir at 37 C, flow controlled by a peristaltic pump. The entire apparatus is enclosed in a thermostatec hood at 37 C.

Stop the peristaltic pump and begin the flow of fixative. Perfuse at approx 20 mL/min such that approx 500 mL of fixative is perfused over a 10- to 20-min period. 

Perfuse the cells into the channels at a shear force of 2 dyn/cm and monitor this process on microscope. Stop the shear flow (generally within 5—7 s) when you see the whole channel is evenly covered with cell suspension. 

Fig. 10.2. a A 59-year old male patient with known colorectal cancer and acute hemiparesis. NECT 1 h after stroke-onset does not show any early stroke signs, hemorrhage or edema, b MIP reconstruction of intracranial CTA scan shows a stop of contrast agent arrows) at the distal main stem of the left middle cerebral artery (MCA), c Dynamic perfusion-CT (PCT) analysis reveals subtotal restriction of cerebral blood flow... 

An example of the calculated coronary perfusion flow based on the above relations, is shown in Figure 8. The coronary flow to the endocardial layers is seen to stop during systole (compression) while the flow in the epicardial layers, which are subjected to much lower compression values of P (y, t), is seen to reduce only slightly. The autoregulatory effect which adjusts the blood flow to the metabolic demand, is demonstrated by comparing curves A and B in Figure 8. Lower blood... 

Figure 1 Models for analyzing tissue PO2 disappearance rates measured with PO2 microelectrodes after stopping perfusate flow to the carotid body, (a) Inhibitory effects of NO on a single enzyme model for C3tiochrome oxidase (high-affinity pathway) are shown, based on a decrease in maximum tissue PO2 disappearance rate (top panel) and increase in (middle panel) with NO. Predicted 02-dependent PO2 disappearance rates (bottom panel) for NO concentrations of 0 (circle), 100 (triangle). 250 (diamond), and 500 nM (square) are shown, (b) The single-oxidase model was modified by adding a second, low-affinity (high enzyme (top panel) for 02-dependent production of NO by neuronal nitric oxide synthase (nNOS). Predicted 02-dependent PO2 disappearance rates (bottom panel) are shown with the additional amount of O2 consumed by the low-affinity pathway (dashed lines) over that required by the high-affinity pathway (solid lines) for each NO concentration (symbols same as above).

Recessed gold microelectrodes (29) with 5-pm tips were used to measure tissue P02- Disappearance curves were obtained by briefly stopping perfusate flow... 

Figure 2 Time course of changes in intracellular pH ( ), ATP(D) and PCr ( ) in a rat heart subjected to 25 min of total global ischaemia followed by 30 min of reperfusion. pH was determined from the chemical shift of Pj. Changes in ATP and PCr are expressed as percentage change from the basal levels measured prior to ischaemia. Total global ischaemia was achieved by stopping all flow of perfusate to the heart.

Korin, N., Bransky, A., Dinnar, U., and Levenberg, S. 2009. Periodic flow-stop perfusion microchannel bioreactors for mammalian and human embryonic stem ceU long-term culture. Biomed Microdevices 11 87-94. 

Microscale devices may serve as a tool for optimization of culture conditions while also providing the precise control over the cell microenvironment. Arrays of micro-bioreactors have been developed to study growth and differentiation of hESCs in a perfusion system (Cimetta et al., 2009 FigaUo et al., 2007), as well as a micro-bioreactor with a periodic flow-stop perfusion system for coculture of hESCs with human feeder cells (Korin et al., 2009). 

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