Outflow Cannula Research Articles

A new method for estimating intestinal capillary pressure.

The purpose of this study was to compare the venous occlusion method for measuring capillary pressure with the stop-flow isovolumetric method in the cat small intestine. Venous occlusion pressures were determined from the inflection point of the venous pressure tracing after sudden occlusion of the venous outflow cannula. Venous occlusion pressure was highly correlated (r = 0.98, P less than 0.01) with stop-flow capillary pressure. This finding indicates that the major sites of fluid filtration and vascular capacitance reside at the same segment of the intestinal microcirculation. The venous occlusion method is a relatively simple technique for measuring whole-organ capillary pressure that is not constrained by the technical difficulties associated with volumetric/gravimetric techniques.

Development of a totally implantable, electrically actuated left ventricular assist system

A totally implantable left ventricular assist system has been under development at Stanford since 1972. The system fabricated for clinical use employs a highly efficient, electrically powered solenoid drive system coupled to a dual pusher-plate blood pump with xenograft inflow and outflow valves. The system is of suitable size for implantation either within the anterior abdominal wall or anterolateral within the peritoneal cavity, with pump inflow and outflow cannulas from the left ventricular apex and to the supraceliac aorta, respectively. Thus, the system is well suited for short-term cardiac support after cardiac surgical procedures, being easily explantable due to its superficial location. In addition, long-term support, with the possibility of subsequent cardiac transplantation, is feasible when intrinsic myocardial dysfunction is irreversible, in contrast to existing pneumatically powered systems which require percutaneous drive-lines and compressed air sources. Although the integrated clinical left ventricular assist system described has not been extensively tested in vivo, more than 6,500 hours of operation in calves has been accumulated with a related system; the maximum duration of continuous left ventricular assist using this system in vivo has been 129 days, the longest reported successful operation of such an electrically driven system. These experimental studies have demonstrated the capability of the device to provide total systemic circulatory support for a prolonged period in the context of a severely failing left ventricle.

Improved irrigation in arthroscopy

Efficient irrigation during arthroscopy mainly depends on the patency of the outflow cannula. By inserting the cannula into the posteromedial recess of the knee joint good drainage is obtained.

A modified technique for the selective perfusion of the fourth cerebral ventricle in conscious dogs

A method is described which permits selective and repetitive perfusion of the fourth cerebral ventricle in the conscious dog. An inflow needle is introduced stereotaxically at an angle of 42°–44° through the occipital bone and the cerebellum until its tip reaches the ventricular space. The outflow guide needle is placed vertically above the cisterna cerebello-medullaris. Later a matching outflow needle is introduced through the guide needle, punctures the atlanto-occipital membrane and drains the cisterna magna. A retaining ring with a set-screw, which fits into the hub of the guide cannula, is used to adjust the outflow needle in the vertical plane. The inflow needle and outflow cannula are fixed permanently in place with the aid of a kneadable solidifying dough (Technovit) to two self-threading screws at the external protuberance. In a separate study fentanyl perfused through the fourth cerebral ventricle in increasing concentrations (2.5, 5, 10, and 20 μg/ml) induced a dose-related hypotension, bradycardia, and electroencephalograph-synchronization. These effects could be reversed by subsequent naloxone (20 μg/ml) perfusion.

Sites of cholinergic vasoconstriction in trout gills

Sites of cholinergic vasoconstriction were investigated in isolated saline-perfused holobranchs of trout (Salmo gairdneri and S. trutta). Acetylcholine (ACh) always increased overall branchial vascular resistance (BVR) and, in addition, decreased the proportion of the total inflow appearing at the outflow cannula from the efferent arch artery. Since this was observed in both constant pressure and constant flow situations, it was concluded that ACh exerted most of its effect at a site downstream from the secondary lamellae, probably at the bases of the efferent filament arteries. Prussian blue dye injections indicated that, in addition, ACh caused a marked reduction in flow to the distal halves of the filaments and that flow within the proximal secondary lamellae was restricted during ACh administration to the inner and outer marginal channels of the lamellae. The results are discussed in terms of recent findings concerning the vascular anatomy of teleost gills.

Supporting effects of myoepithelial cells in submandibular glands of dogs when acting against increased intraluminal pressure.

1. In dogs under chloralose-urethane anaesthesia secretion from the submandibular gland was recorded with the outflow at gland level and at heights of up to 50 cm above the gland.2. With the outflow level increased, secretion elicited by sympathetic nerve stimulation was far better maintained before than after injection of the alpha-adrenoceptor blocking agent dihydroergotamine.3. When the outflow level was raised while no secretion occurred, fluid flowed into the gland. Part of this amount was returned on lowering the outflow to gland level. This volume was assumed to have been accommodated in the distended luminal system, whereas some fluid was obviously lost into the gland tissues.4. Both these fractions of the fluid flowing into the gland when the outflow level was high could be reduced by injecting the alpha-receptor agonist phenylephrine. Bradykinin, which like phenylephrine is known to contract salivary myoepithelial cells, had the same effect on the two inflow volumes.5. It is concluded that myoepithelial contraction reduced the distensibility of the luminal system and in addition supported the acini, thereby diminishing backflow into the glandular tissues and enabling the gland to discharge saliva against a high pressure.6. Morphologically it was found that in resting glands PAS-positive saliva was displaced from the ductal system when the outflow cannula was raised, but it was preserved in the lumina under similar conditions when the myoepithelial cells were being stimulated by phenylephrine or bradykinin.7. Although sympathetic secretion could be maintained against a head of pressure, so long as it was accompanied by myoepithelial contraction, the increased force caused by the secretion led to disruptive damage of striated ducts which are the first part of the luminal system not supported by myoepithelial cells.8. The morphological findings reinforce the belief that contraction of myoepithelial cells gives active support to the underlying parenchyma.

A vasodepressor effect of pentobarbitone sodium

1. In anaesthetized cats under artificial ventilation, a few milligrams of pentobarbitone sodium injected into the cerebral ventricles produced a pronounced fall in arterial blood pressure, which was central in origin and resulted from inhibition of vasomotor tone.2. Pentobarbitone sodium was more effective in lowering blood pressure when injected into the cerebral ventricles than when injected into the cisterna magna, yet the pentobarbitone sodium did not act on structures in the ventricular wall, but acted on structures reached from the subarachnoid space.3. To produce its vasodepressor effect, the pentobarbitone sodium had to pass through the foramina of Luschka into the subarachmoid space beneath the medulla oblongata and to penetrate its ventral surface in a region caudal to the trapezoid bodies and lateral to the pyramids. This was the outcome of experiments in which the pentobarbitone sodium was injected into or perfused through the cerebral ventricles with or without an outflow cannula inserted into the aqueduct or into the fourth ventricle, and of experiments in which pentobarbitone sodium solutions were applied by means of Perspex rings to this region of the exposed ventral surface of the medulla. Whereas the application of pentobarbitone sodium to this region on one side had a weak vasodepressor effect only, its application on both sides produced a pronounced fall in arterial blood pressure.4. The region where pentobarbitone acted on topical application covers the region where nerve cells are found in the marginal glia immediately under the pia mater. The possibility is discussed that these cells are the morphological substrate on which the pentobarbitone acts, that arterial blood pressure is maintained by their activity which is suppressed by the pentobarbitone sodium.

Pancreatic Secretion in the Bovine Calf1,2

Fourteen dairy calves, ranging in age from 3–180 days, were used for pancreatic secretion studies. The aseptic return cannula loop was adapted to connect to an electronic drop-counter and recorder. Generally, this cannula could be kept in place only 3–6 wk. Pancreatic flow increased with age. Flow during and after feeding in young calves followed a characteristic pattern similar to that of the simple-stomached animal, but by four months of age it became more constant, approaching the pattern observed in mature sheep. There was no evidence of physical disability in four calves having total loss of pancreatic juice through the outflow cannula for 3–6 wk. A gradually declining flow was observed in two calves fasted for 61 hr.

A contribution to the bio-physics of intestinal absorption

The following experiments were suggested by purely biophysical considerations concerning absorption from the intestines and it was deemed desirable to report the same in this preliminary communication.On purely physical-chemical grounds it can be shown that the absorption of a chemical in solution which flows through a membranous tube will depend on the speed of flow of the solution through the lumen of the tube. The authors attempted to test this postulate on the living intestine in the following manner. Loops of intestines were tied off in dogs, cats and rabbits under anesthesia, and large inflow and outflow cannulas were attached to the two ends of the same respectively. A solution of the drug was perfused through the loop under proper precautions from above downwards, maintaining the temperature of the animal constant and a record was made of the blood pressure and respiratory effects. The drugs employed in these experiments were solutions of potassium cyanide and the powerful alkaloid, aconitin. Thes...