II. FIELD OF THE INVENTION

This application relates to apparatus and methods for treating intracorporeal fluid accumulations, such ascites, pleural effusion and pericardial effusion.

III. BACKGROUND OF THE INVENTION

There are a variety of conditions which result in pathologic chronic collection of bodily fluids within the peritoneum, pleura or pericardial sac. Chronic ascites, pleural effusion and pericardial effusion are conditions in which chronic fluid collections persist and result in increased morbidity and mortality.

These foregoing conditions currently are treated typically by one of three methods: 1) external drainage, which poses a risk of infection and long-term requirement for multiple punctures, 2) drainage to another body cavity, or 3) treatment with drugs. In pleural effusion, excess fluid arising from an underlying pathology, such as lung cancer, breast cancer or lymphoma, accumulates in the pleural cavity. If left untreated, the fluid accumulation may interfere with proper lung function, significantly increasing morbidity and mortality. Depending upon the underlying cause of the pleural effusion, treatment may consist of drug therapy, thoracentesis, in which a needle is periodically inserted through the chest and into the pleural cavity to drain the fluid accumulations, or installation of an intercostal drain, in which one end of a pigtail catheter is inserted into the pleural cavity and the fluid is drained to an external canister. Although a relatively simple procedure, placement of an intercostal drain is associated with a relatively high rate of major complications, including hemorrhage and infection. Repeated effusions also may be treated by pleurodesis, in which two pleural surfaces are attached to one another so that no fluid can accumulate between them. However, this procedure requires a lengthy hospital stay and is reported to be associated with the onset of adult respiratory distress syndrome, a potentially life-threatening complication.

In pericardial effusion, fluid accumulates in the pericardial sac and may lead to increased intrapercardial pressure and reduced cardiac output. Where the fluid accumulation interferes with proper heart function, pericardiocentesis may be performed, in which the fluid is drained to an external site through a needle or catheter inserted through the chest wall and into the pericardial sac. For chronic cases, the treatment of choice is formation of a pericardial window. In this highly invasive procedure, a section of the pericardial sac is removed to create a fistula that permits fluid to drain to the abdomen. Although this procedure is usually well tolerated by patients, the pericardial window may close, requiring re-operation.

Ascites is a highly debilitating complication associated with many medical conditions including liver failure, congestive heart failure and certain cancers. Untreated ascites can result in respiratory compromise, compression of the inferior vena cava (a vital blood vessel) and spontaneous bacterial peritonitis (a life-threatening condition). Conventional treatment for ascites includes a regime of drugs and dietary restriction, and for chronic cases, repeated surgical interventions.

The drugs often employed to treat ascites are usually long-term and often result in complications. The most common pharmaceutical treatment of ascites involves the use of diuretics to remove fluid from the patient's body through their urine. The difficulty with this treatment, however, is that fluid is removed from the entire body, including the circulating volume of blood. This in turn may result in excessive loss of fluid required to perfuse the vital organs of the human body. Thus, even with frequent application, the medicines frequently provide unsatisfactory results. In such cases, surgical, or invasive, procedures are indicated.

For chronic ascites refractory to drugs, a patient typically is required to undergo paracentesis on a regular basis, e.g., every 2-4 weeks, to drain accumulated fluid. In this procedure, peritoneal fluid is drained through the abdominal wall via the insertion of a needle through the abdominal wall into the peritoneal cavity. The regular accumulation and drainage by paracentesis of large quantities of fluid in the peritoneal cavity adversely impacts patient quality of life and often can interfere with the patient's ability to combat the underlying disease, such as cirrhosis. Moreover, repeated paracenteses place the patient at increased risk for a life-threatening infection of the peritoneal cavity. Other surgical/invasive procedures typically involve treatment of the cause of the ascites (for example, the Transjugular Intrahepatic Portosystemic Shunt) but these measures also frequently result in serious and life-threatening complications or become ineffective over time. Consequently, such procedures are performed infrequently.

Paracentesis often provides only a temporary solution in chronic cases, as the ascites quickly refills the peritoneal cavity. In particular, the presence of large quantities of fluid within the peritoneal cavity frequently disturbs the patient's fluid equilibrium, such that the patient's body attempts to compensate for fluid loss due to paracentesis by increasing ascites production. To combat this phenomenon, it is standard practice for clinicians to infuse a plasma expander, usually human albumin, into patients undergoing paracentesis. The cost of human albumin used for a typical 5-7 liter extraction can cost upwards of $500 per procedure. Consequently, regularly scheduled paracenteses followed by infusion of human albumin impose significant economic burdens on the patient and the health care system.

Previously known attempts to treat ascites have included indwelling catheters including external ports, and squeeze-bulb and magnetically-driven reciprocating pumps to transfer ascites from the peritoneal cavity into the venous vasculature, through an external port, or into the bladder. For example, U.S. Pat. No. 4,240,434 to Newkirk and U.S. Pat. No. 4,657,530 to Buchwald each describes a squeezable tube-type ascites shunt having an inlet end configured to the placed in the peritoneal cavity and an outlet end configured to be placed in a vein. Rosenblit et al., in an article entitled “Peritoneal-Urinary Drainage for Treatment of Refractory Ascites: A Pilot Study,” J. Vascular & Interv. Radiology, 9(6):998-1005 (November/December 1998) describe a similar squeeze-bulb system having an outlet disposed in the bladder. U.S. Pat. No. 4,610,658 to Buchwald et al. describes an implantable pump for treating ascites that includes a magnetically-driven pump to transfer fluid from the peritoneal cavity to the vasculature system. Such previously known devices suffer from a variety of drawbacks, including fibrous encapsulation, frequent clogging and infection. Such devices provided little improvement over periodic paracenteses, and resulted in increased rates of infection, re-operation or other complications if left in place for any length of time. Moreover, a key drawback of such previously-known systems is the requirement that the patient must repeatedly locate and manually actuate the pumping mechanism on a daily basis. Such activity may be difficult for patients, especially the elderly and obese, and further complicated by an ascites-distended abdomen. Consequently, the difficulty of manipulating such previously-known systems promotes patient non-compliance, in turn leading to clogging and infection.

In view of the above-noted drawbacks of previously-known systems, it would be desirable to provide methods and apparatus for treating ascites that remove small quantities of fluid multiple times per day, and thereby avoid fluid disequilibrium caused by periodic removal of large volumes of fluid using paracentesis and concomitant use of costly plasma expanders.

It further would be particularly desirable to provide methods and apparatus for treating ascites and other intracorporeal fluid accumulations using implantable devices that are resistant to clogging, reduce risk of infection, and do not interfere with normal working of a patient's vascular system.

It also would be particularly desirable to provide methods and apparatus for treating ascites and other intracorporeal fluid accumulations using implantable devices that are configured to pump at high flow during multiple intervals daily, thereby reducing the risk of pump or catheter blockage.

It still further would be desirable to provide methods and apparatus for treating ascites and other intracorporeal fluid accumulations using implantable devices that are capable of sensing environmental conditions and that move fluid only when doing so is consistent with a patient's activity level.

IV. SUMMARY OF THE INVENTION

The present invention overcomes the drawbacks of previously-known fluid management systems for treating ascites by providing a fluid management system that automatically and autonomously removes ascites accumulations with little patient involvement. The fluid management system of the present invention preferably comprises an implantable device including a pump, a controller, a battery and a transceiver; a charging and communication system configured to periodically charge the battery of, and communicate with, the implantable device; and monitoring and control software, suitable for use with a conventional personal computer, for configuring and controlling operation of the implantable device and charging and communication system. Preferably, the monitoring and control software is available only to the treating physician, such that the patient generally interacts with the implantable device only via the charging and communication system for purposes of recharging the implantable device. In accordance with one aspect of the present invention, the implantable device is configured to pump fluid in small increments, at relatively high flow rates, during predetermined times of the day to achieve a target volume, and further is configured to periodically alter the pump position to reduce the risk of clogging of the implantable device during non-pumping intervals. The pump also may be programmed to perform a rapid sequence of backward and forward movements if a blockage is detected, thereby clearing the blockage. Additionally, the fluid management system may include one or more sensors configured to detect indicia of the onset of infection, e.g., an increase in temperature, respiratory rate, or the viscosity of ascitic fluid, and one or more alarms configured to indicate to the physician a prediction or detection of infection based on the output(s) of those sensors.

In one embodiment, the fluid management system is configured to move ascites accumulating in the peritoneal cavity to the patient's bladder in small increments on a daily basis, so that the ascitic fluid is evacuated from the body during urination. In another embodiment, designed for treating pleural effusion, the fluid management system is configured to move fluid accumulating in the pleural cavity to the patient's bladder in small increments on a daily basis, so that the effusive fluid is evacuated from the body during urination. In yet another embodiment, the implantable device is configured to have an inflow catheter that communicates with the pericardial sac to move pericardial effusion to the bladder. Alternatively, the embodiments for treating pleural and pericardial effusion may deposit the effusive fluid within the patient's peritoneal cavity (rather than the bladder), where it will be reabsorbed and excreted via the kidneys.

In one preferred embodiment, the implantable device includes an electrically-driven mechanical gear pump configured for subcutaneous implantation. The pump has an inlet port coupled to an inflow catheter and an outlet port coupled to a bladder catheter. In accordance with one aspect of the present invention, the pump employs a pair of floating gears that function as a positive displacement pump, wherein a driving gear is coupled to a splined shaft of an electric motor to minimize power consumption arising due to manufacturing variations or shaft eccentricity. The inflow catheter comprises a tube having a first end configured to be coupled to the pump inlet and a second end configured to be positioned in a selected cavity, e.g., peritoneum, pleura or pericardial sac. The second end of the inflow catheter includes a plurality of through-wall apertures that permit fluid accumulating to pass into the catheter. The bladder or outflow catheter comprises a tube having a first end configured to be coupled to the pump and a second end configured to be inserted through the wall of, and fixed within, a patient's bladder. Alternatively, for treating pleural or pericardial effusions, the second end may be configured for placement in the peritoneal cavity, rather than the bladder. The fluid circuit further includes sensors arranged to monitor ambient pressure, pressure at the pump inlet, pressure at the pump outlet, pressure in the bladder (or peritoneal cavity, if this is used as a sink), and optionally the temperature of the ascitic fluid and the respiratory rate of the patient. The inflow and outflow catheters include connectors configured to reduce the risk of improper implantation.

The implantable device further comprises a controller, packaged together with the pump, electric motor, battery, charging coil, and radio transceiver within a low volume sealed housing. The controller is coupled to the pump motor, battery, transceiver and a plurality of sensors to continually monitor pressure, temperature, humidity, charge status, pump status, patient movement and other environmental and system related parameters. The controller preferably comprises a processor, nonvolatile memory for storing firmware, implant identification information, and system and environmental data, and volatile memory that serves as a buffer for computations and instructions during execution and firmware updating. The pump motor is configured for extended use and low power consumption, and preferably includes Hall effect sensors for position sensing and to determine the direction of rotation (and correspondingly, flow and fluid viscosity). The battery preferably is a long-lasting lithium-ion or lithium polymer battery that is coupled to an inductive charging circuit, thereby enabling the battery to be recharged using the external charging and communication system. A radio frequency transceiver preferably is employed in the device for transmitting system information to, and receiving information from, the external charging and communication system, including system performance data, commands, and firmware upgrades. All of the foregoing components preferable are disposed within the housing, which further includes a filler having a low permeability for water, thereby reducing infiltration of moisture into the housing.

In accordance with one aspect of the present invention, the fluid management system includes an external charging and communication system. In a preferred embodiment, the charging and communication system comprises a housing containing a controller, radio transceiver, inductive charging circuit, power source and quality-of-charging indicator. The controller is coupled to the inductive charging circuit, power source, quality-of-charging indicator, radio transceiver, and memory for storing information to be transmitted between the monitoring and control software and implantable device. The charging and communication system preferably includes a data port, such as a USB port, or a wireless port, such as Bluetooth, Zigbee or GPRS, that permits the charging and communication system to be coupled to a conventional computer, such as a personal computer or laptop computer, configured to run the monitoring and control software. In one embodiment, the charging and communication system may include a cord that enables the system to be directly coupled to a conventional power supply, such as 120V AC wall socket. More preferably, however, the charging and communication system includes a battery-powered handpiece that periodically may be coupled to an AC powered charging base, so that the handpiece may be separated from the base to recharge the implantable device without tethering the patient with a power cord. In one preferred embodiment, the control circuitry of the charging and communication system may be configured to boost power supplied through the inductive charging circuit to the motor of the implantable device to unblock potential clogging of the gear pump.

The fluid management system further comprises monitoring and control software that preferably is accessible only to the patient's physician. The software is configured to run on a conventional personal computer or laptop computer, and enables the physician to configure and monitor operation of the charging and communication system and implantable device. The software may include routines for controlling any of a number of parameters associated with the pump operation, such as a target amount of fluid to move daily or per motor actuation, and limits for inflow catheter pressure, bladder pressure, pump pressure, and implant temperature. The software also may be configured to control operation of the implantable device so as not to move fluid during specific periods (e.g., at night) or to defer pump actuation if the patient is asleep. The software further may be configured, for example, to send immediate commands to the implantable device to start or stop the pump, or to operate the pump in reverse or at high power to unblock the pump or its associated catheters, such as when the patient is visiting his or her physician. The software may be configured to download data collected from the implantable device and stored on the charging and communication system, such as during a patient visit to the physician's office. Optionally, based on the downloaded information, such as the patient's respiratory rate, temperature, and fluid viscosity, the software may be configured to alert the physician of a prediction or detection of infection.

It is contemplated that the system of the present invention may avoid difficulties typically associated with the previously-known apparatus and methods for addressing ascites. It is expected, for instance, that the system and methods of the present invention will enable small quantities of peritoneal fluid to be moved to the bladder without the inconvenience and complications generally associated with use of pharmaceuticals or paracenteses. In particular, because the apparatus and methods of the present invention avoid repeated, periodic removal of large quantities of fluid, as occurs with paracenteses, the tendency to generate additional ascites to offset the removed fluid will be reduced. These effects in turn are expected to obviate the need to infuse plasma expanders, such as human albumin, into the patient following paracentesis, thereby resulting in significant cost savings to the patient and health care system. The prediction or detection of infection, particularly at an early stage of infection, further may improve patient outcomes and reduce the need for more expensive treatments. Finally, the apparatus and methods of the present invention are expected to provide improved quality of life for chronic ascites patients, allowing such patients to pursue less sedentary lifestyles than would otherwise be possible, and encouraging better compliance with medically-directed dietary and exercise regimes.

In an alternative embodiment, a fluid management system is provided generally as described above, but instead configured for treating pleural or pericardial effusion. As discussed above, few surgical options are available for treating these conditions, and most of those present significant risks for morbidity and morality. In particular, the system of the present invention may be configured for treating pleural or pericardial effusion, and comprises an implantable device, a charging and communication system and software substantially as described above. This embodiment differs from the ascites fluid management system of the present invention primarily in that the pump has an inflow catheter coupled to a pleural or pericardial cavity, the controller is configured to work under negative pressures, and the outflow catheter may deposit the drained fluid into the peritoneal cavity. More particularly, the inflow catheter has a first end configured to be coupled to the pump inlet and a second end configured to be positioned in the pleural or pericardial cavity, and includes a plurality of through-wall apertures that permit fluid accumulating in the cavity to pass into the catheter without interfering with proper functioning of the lungs or heart. As some fluid is required to lubricate movement of the organ within these cavities, the implantable device preferably is programmed not to pump all of the fluid from the cavity. In addition, the implantable device is programmed to interpret and provide drainage that accounts for pressure fluctuations arising in the cavity during normal respiration or cardiac activity.

Methods of implanting and operating the fluid management system of the present invention also are provided. The implantable device preferably may be placed subcutaneously using interventional radiologic techniques including radiographic imaging or ultrasound, while the inflow catheter and outflow catheter may be placed using surgical, or more preferably, minimally invasive procedures. The inflow catheter, in one variation, may be tunneled subcutaneously to the site of drainage and the outflow tubing can be subcutaneously channeled to the bladder (or peritoneal cavity). The implantable device preferably is programmed using radio frequency coupling of the transceivers in the implantable device and charging and communication system, while power is supplied to the battery of the implantable device by coupling the inductive charging circuits of the implantable device and charging and communication system. Additional details of methods of implanting and operating a system in accordance with the present invention are described below.

