Fluid-assisted medical devices, systems and methods

This application is being filed as a PCT International Patent application in the name of TissueLink Medical, Inc. (a U.S. national corporation), for the designation of all countries except the US, and Michael E. McClurken, David Lipson, Robert Luzzi, Arnold E. Oyola, Jonathan E. Wilson, Christopher W. Maurer, and Roger D. Greeley (all US citizens), for the designation of the United States only, on 5 Sep. 2002.

This patent application is related to U.S. Patent Application Ser. Nos. 60/356,390, filed Feb. 12, 2002, and 60/368,177, filed Mar. 27, 2002, both now pending. This patent application is also related to U.S. patent application Ser. No. 09/947,658, filed Sep. 5, 2001, now pending, which is a continuation-in-part of U.S. patent application Ser. No. 09/797,049, filed Mar. 1, 2001, now pending, which is a continuation of U.S. Patent Application Ser. No. 60/187,114, filed Mar. 6, 2000. This patent application is also related to U.S. patent application Ser. No. 09/668,403, filed Sep. 22, 2000, now pending. This patent application incorporates the entire disclosure of each patent application herein by reference to the extent they are consistent.

This invention relates generally to the field of medical devices, systems and methods for use upon a body during surgery. More particularly, the invention relates to electrosurgical devices, systems and methods for use upon tissues of a human body during surgery, particularly open surgery and minimally invasive surgery such as laparoscopic surgery.

Electrosurgical devices configured for use with a dry tip use electrical energy, most commonly radio frequency (RF) energy, to cut tissue or to cauterize blood vessels. During use, a voltage gradient is created at the tip of the device, thereby inducing current flow and related heat generation in the tissue. With sufficiently high levels of electrical energy, the heat generated is sufficient to cut the tissue and, advantageously, to stop the bleeding from severed blood vessels.

Current dry tip electrosurgical devices can cause the temperature of tissue being treated to rise significantly higher than 100° C., resulting in tissue desiccation, tissue sticking to the electrodes, tissue perforation, char formation and smoke generation. Peak tissue temperatures as a result of RF treatment of target tissue can be as high as 320° C., and such high temperatures can be transmitted to adjacent tissue via thermal diffusion. Undesirable results of such transmission to adjacent tissue include unintended thermal damage to the tissue.

Using saline according to the present invention to couple RF electrical energy to tissue inhibits such undesirable effects as sticking, desiccation, smoke production and char formation. One key factor is inhibiting tissue desiccation, which occurs when tissue temperature exceeds 100° C. and all of the intracellular water boils away, leaving the tissue extremely dry and much less electrically conductive. However, an uncontrolled or abundant flow rate of saline can provide too much cooling at the electrode/tissue interface. This cooling reduces the temperature of the target tissue being treated, and the rate at which tissue thermal coagulation occurs is determined by tissue temperature. This, in turn, can result in longer treatment time to achieve the desired tissue temperature for treatment of the tissue. Long treatment times are undesirable for surgeons since it is in the best interest of the patient, physician and hospital, to perform surgical procedures as quickly as possible.

RF energy delivered to tissue can be unpredictable and often not optimal when using general-purpose generators. Most general-purpose RF generators have modes for different waveforms (e.g. cut, coagulation, or a blend of these two) and device types (e.g. monopolar, bipolar), as well as power levels that can be set in watts. However, once these settings are chosen, the actual power delivered to tissue and associated heat generated can vary dramatically over time as tissue impedance changes over the course of RF treatment. This is because the power delivered by most generators is a function of tissue impedance, with the power ramping down as impedance either decreases toward zero or increases significantly to several thousand ohms. Current dry tip electrosurgical devices are not configured to address a change in power provided by the generator as tissue impedance changes or the associated effect on tissue and rely on the surgeon\'s expertise to overcome this limitation.

In certain embodiments, a system for treating tissue is provided. The system comprises radio frequency power provided from a power source at a power level; an electrically conductive fluid provided from a fluid source at a fluid flow rate; and an electrosurgical device configured to provide the radio frequency power and the electrically conductive fluid to the tissue.

In certain embodiments the conductive fluid is an indicator of tissue temperature. The conductive fluid can relate the tissue temperature to boiling, an amount of boiling, or an onset of boiling of the conductive fluid.

The conductive fluid can cool the tissue or dissipate heat from the tissue. Alternately or additionally, the conductive fluid dissipates heat from at least one of the tissue and the conductive fluid by a boiling of at least a portion of the fluid.

For other embodiments, at least one of the radio frequency power level and the flow rate of the conductive fluid is used to effect a boiling of the electrically conductive fluid. Furthermore, in some embodiments, the effect on boiling may comprise at least one of initiating, increasing, decreasing and eliminating boiling of the electrically conductive fluid.

For other embodiments, the electrically conductive fluid functions to limit the temperature of the tissue at the tissue surface to about a boiling temperature of the electrically conductive fluid.

Generally, the electrically conductive fluid protects the tissue from desiccation. In some embodiments, the conductive fluid protects the tissue from desiccation by boiling at least a portion of the electrically conductive fluid. In other embodiments, the electrically conductive fluid protects the tissue from desiccation by boiling at least a portion of the conductive fluid at a temperature below the temperature of tissue desiccation.

For some embodiments, the electrically conductive fluid is provided to the tissue at the tissue surface and the radio frequency power is also provided to the tissue at the tissue surface. The radio frequency power reaches below the tissue surface into the tissue via (through) the electrically conductive fluid at the tissue surface.

At least one of the radio frequency power level and the conductive fluid flow rate can be adjusted based on a boiling of the conductive fluid. Furthermore, for other embodiments, adjusting at least one of the radio frequency power level and the conductive fluid flow rate based on a boiling of the conductive fluid comprises one of initiating, increasing, decreasing and eliminating boiling of the electrically conductive fluid.

In certain embodiments, a method for treating tissue is provided comprising providing radio frequency power at a power level; providing an electrically conductive fluid at a fluid flow rate; and providing an electrosurgical device configured to provide the radio frequency power with the electrically conductive fluid to the tissue.

Still further, a system for treating tissue is provided, the system comprising radio frequency power provided from a power source at a power level; an electrically conductive fluid provided from a fluid source at a fluid flow rate; an electrosurgical device configured to provide the radio frequency power and the conductive fluid to the tissue; and a fluid coupling which couples the tissue and the electrosurgical device, the coupling comprising the conductive fluid.