Abstract: A blood vessel puncturing means within the internal cavity of the sealing jaws of an electrosurgical instrument. A forceps type electrosurgical device provided with jaws having electrically conductive sealing plates on the inner surfaces that is used to seal a blood vessel during will usually have an inner cavity of the jaws between the jaws within which a blood vessel is received and may expand during electrosurgical sealing. To prevent a blood vessel expanding during electrosurgical sealing to a dangerous size, the inner cavity is provided with a means to puncture the blood vessel in a controlled fashion, and thereby relieve the pressure within the blood vessel. The puncturing means may comprise one or more relief vents. The relief vents may provide channels to allow pressure to be vented to the external of the jaws, thus relieving the internal pressure on the jaws during coagulation.