Low power tissue sealing device and method

1. A surgical system for fusing a passageway of a fluid-carrying vessel with a diameter up to 5 millimeters, the system comprising:

an electrosurgical generator capable of delivering electrosurgical power;

a surgical instrument electrically connected to the electrosurgical generator and adapted to transfer electrosurgical power from the electrosurgical generator to a pair of end effectors disposed at a distal end of the surgical instrument, wherein the end effectors are adapted to close the passageway of the vessel by clamping a portion of the vessel between the end effectors; and

a power control circuit for controlling the delivery of radio frequency energy to the vessel through the end effectors; wherein the surgical system is configured to:

deliver radio frequency energy at a non-pulsing power to a portion of the vessel for a period of time, wherein the period of time is measured from the beginning of the radio frequency energy delivery and continues through a fusing of the portion of the vessel, the non-pulsing power having no less than 7 Watts and no more than 35 Watts, an output current between 0.2 and 1.75 Amperes RMS, and an output voltage between 5 and 135 Volts RMS throughout the period of time, the non-pulsing power further causing the portion of the vessel to reach a temperature of at least 140 degrees Celsius and begin to desiccate within the period of time;

monitor an impedance of the portion of the vessel being fused during the period of time;

limit the flow of non-pulsing power when the impedance of the portion of the vessel being fused reaches a set impedance threshold within the period of time; and

terminate the flow of non-pulsing power when the impedance of the portion of the vessel being fused reaches a predetermined level.

2. The surgical system of claim 1 , wherein the radio frequency energy is delivered to the portion of the vessel with a current density below 0.12 Amps per square millimeter.

3. The surgical system of claim 1 , wherein the radio frequency energy is delivered to the portion of the vessel with a current density between 0.034 and 0.1 Amps per square millimeter.

4. The surgical system of claim 1 , wherein the period of time is 3 seconds or less.

5. The surgical system of claim 1 , wherein each of the surgical instrument end effectors has a contacting surface area of less than 22 square millimeters.

6. The surgical system of claim 1 , wherein each of the surgical instrument end effectors has a contacting surface area of between 15 and 22 square millimeters.

7. The surgical system of claim 1 , wherein the output current is between 0.75 and 1.00 Amperes RMS.

8. The surgical system of claim 1 , wherein the output voltage is between 70 and 90 Volts RMS.

9. The surgical system of claim 1 , wherein the end effectors are adapted to apply between 25 and 125 lb/in 2 of pressure to the portion of the vessel.

10. A power control system for delivering radio frequency energy to a vessel fusing surgical instrument including an end effector, the power control system comprising:

a power supply for delivering an output voltage and an output current to the end effector;

an impedance sensing circuit for detecting an impedance of a vessel being fused;

a power sequencing module for automatically sequencing an electrosurgical power delivered to the surgical instrument;

wherein the power sequencing module is adapted to:

raise the output current of the power supply to between 0.5 and 1.75 Amperes RMS and the output voltage of the power supply to between 5 and 135 Volts RMS;

apply non-pulsing power of no less than 7 Watts and no more than 35 Watts, between 0.5 and 1.75 Amperes RMS and between 5 and 135 Volts RMS to the vessel being fused for a period of time of 3 seconds or less, wherein the non-pulsing power causes the vessel to reach a temperature of at least 140 degrees Celsius, and the period of time is measured from the beginning of the application of the non-pulsing power and continues through the beginning of a desiccation of the vessel and through a drying out and the fusing of the vessel;

monitor an impedance of the vessel being fused through the impedance sensing circuit during the period of time;

limit the flow of power to the vessel being fused when the impedance of the vessel being fused reaches a set impedance threshold within the period of time; and

terminate the flow of power to the vessel being fused when the impedance of the vessel being fused reaches a predetermined level.

11. The power control system of claim 10 , wherein the power sequencing module is adapted to terminate the flow of power to the vessel being fused when the impedance of the vessel being sealed reaches 150 or more ohms.

12. The power control system of claim 10 , wherein the power sequencing module is further adapted to limit the power delivered to the vessel being fused by 60%-80% when the impedance of the vessel being fused reaches the set impedance threshold.

13. The power control system of claim 12 , wherein the power sequencing module is further adapted to deliver the reduced power to the vessel being fused for a predetermined length of time prior to terminating the flow of power to the vessel being fused.

14. A surgical system for fusing a passageway of a fluid-carrying vessel with a diameter up to 5 millimeters, the system comprising:

an electrosurgical generator capable of delivering electrosurgical power;

a surgical instrument electrically connected to the electrosurgical generator and adapted to transfer electrosurgical power from the electrosurgical generator to a pair of end effectors disposed at a distal end of the surgical instrument, wherein the end effectors are adapted to close the passageway of the vessel; and

a power control circuit for controlling the delivery of radio frequency energy to the vessel through the end effectors; wherein the surgical system is configured to

deliver a radio frequency energy to a vessel, the radio frequency energy having a non-pulsed power having an output current between 0.2 and 1.75 Amperes RMS and an output voltage between 5 and 135 Volts RMS;

apply the non-pulsed power to the vessel for a period of time while the non-pulsed power is held at between 7 Watts and 35 Watts, while allowing the output current to fluctuate between 0.2 and 1.75 Amperes RMS and the output voltage to fluctuate between 5 and 135 Volts RMS, wherein the period of time is measured from the beginning of the application of the non-pulsed power and continues through fusing of the vessel, and the non-pulsed power causes the vessel to being to dessicate within the period of time, wherein the period of time is 3 seconds or less; and

monitor an impedance of the vessel being fused;

limit the flow of non-pulsed power when the impedance of the vessel being fused reaches a set impedance threshold; and

terminate the flow of non-pulsed power when the impedance of the vessel being fused reaches a predetermined level indicative that the vessel being fused is desiccated.

15. The surgical system of claim 14 , wherein the surgical system is configured to deliver non-pulsed power to a vessel with a current density between 0.034 and 0.1 Amps per square millimeter.

16. The surgical system of claim 14 , wherein the period of time is between 2 and 5 seconds.

17. The surgical system of claim 14 , wherein each of the surgical instrument end effectors have a contacting surface area of less than 22 square millimeters.

18. The surgical system of claim 14 , wherein the electrosurgical generator delivers non-pulsing power in the range of 9 to 16 Watts and a total power output is no more than 25 Watts.

19. The surgical system of claim 14 , wherein the non-pulsing power raises a temperature of the portion of the vessel to at least 140 Degrees Celsius to cause the portion of the vessel to begin to desiccate within the period of time.