An adaptive algorithm monitors the rate of tissue impedance change during an electrosurgical procedure. Impedance levels are examined to determine an impedance ramp and/or slope rate, which indicates the rate at which a target tissue is undergoing a phase or state change. The level of electrosurgical energy applied to the target tissue is adjusted in real time. Energy is applied to the target tissue at levels that allow tissue phase or state change to occur in an optimum fashion. Undesired results such as thermal damage and defective sealing are mitigated. Another embodiment determines impedance achieved within a specific interval and adjusts the electrosurgical energy applied to the tissue after a threshold impedance has been maintained or exceeded for a predetermined interval. A further aspect of the invention provides mitigation during processing for partial tissue coverage of device electrodes or thin tissue.