A sensor comprising: a first substrate having a sensing portion configured to be percutaneously inserted into a patient and an extracorporeal circuit mounting portion, the sensing portion defining a sensor thereon and the circuit mounting portion having at least one electrically conductive pad (22A, 22B) formed thereon that is electrically connected to the sensor, the sensor configured to produce a signal indicative of a condition of the patient, an anisotropic medium disposed on the circuit mounting portion, the medium configured to be electrically conductive in a direction through the medium and electrically insulating in directions along the medium, an electrical circuit having at least one electrically conductive terminal (34A, 34B), the circuit being mechanically mounted to the circuit mounting portion of the first substrate via the anisotropic medium with the at least one electrically conductive terminal juxtaposed over the at least one electrically conductive pad, the anisotropic medium establishing local electrical contact between the at least one electrically conductive terminal and the at least one electrically conductive pad characterized in that the electrical circuit comprises a second substrate defining the at least one electrically conductive terminal, wherein the anisotropic medium is an anisotropic elastomer configured to mechanically bond the circuit to the circuit mounting portion of the first substrate and/or wherein the anisotropic medium is an anisotropic tape configured to mechanically bond the electrical circuit to the circuit mounting portion of the first substrate, wherein the electrical circuit comprises: a number of electrical components mounted to the second substrate and electrically interconnected to form a sensor control circuit, the sensor control circuit being electrically connected to the at least one electrical terminal and wherein the second substrate is a flexible substrate. a first substrate having a sensing portion configured to be percutaneously inserted into a patient and an extracorporeal circuit mounting portion, the sensing portion defining a sensor thereon and the circuit mounting portion having at least one electrically conductive pad (22A, 22B) formed thereon that is electrically connected to the sensor, the sensor configured to produce a signal indicative of a condition of the patient, an anisotropic medium disposed on the circuit mounting portion, the medium configured to be electrically conductive in a direction through the medium and electrically insulating in directions along the medium, an electrical circuit having at least one electrically conductive terminal (34A, 34B), the circuit being mechanically mounted to the circuit mounting portion of the first substrate via the anisotropic medium with the at least one electrically conductive terminal juxtaposed over the at least one electrically conductive pad, the anisotropic medium establishing local electrical contact between the at least one electrically conductive terminal and the at least one electrically conductive pad characterized in that the electrical circuit comprises a second substrate defining the at least one electrically conductive terminal, wherein the anisotropic medium is an anisotropic elastomer configured to mechanically bond the circuit to the circuit mounting portion of the first substrate and/or wherein the anisotropic medium is an anisotropic tape configured to mechanically bond the electrical circuit to the circuit mounting portion of the first substrate, wherein the electrical circuit comprises: a number of electrical components mounted to the second substrate and electrically interconnected to form a sensor control circuit, the sensor control circuit being electrically connected to the at least one electrical terminal and wherein the second substrate is a flexible substrate.