An apparatus for cooling or heating the body temperature of a patient, the apparatus comprising: a housing; a blood inlet to receive blood into the housing and a blood outlet for expelling the blood from the housing, the blood inlet and the blood outlet fluidly connected inside the housing via a blood circuit; a pump portion contained within the housing for extracting blood from and infusing blood to a patient's body, the pump portion defining the blood circuit inside the housing; and a heat exchanger portion contained within the housing for selectively heating or cooling the blood; wherein the heat exchanger portion is fluidly connected with at least one fluid inlet to receive a heat exchange fluid and at least one fluid outlet to expel the heat exchange fluid, the fluid inlet and the fluid outlet defining a fluid circuit therebetween; wherein the heat exchanger portion further comprises a plurality of heat exchange tubes operative for flowing the heat exchange fluid therethrough, the plurality of heat exchange tubes being in thermal contact with the blood circuit, wherein the heat exchange fluid flows within the tubes; wherein the blood circuit comprises a first chamber for receiving the blood from the blood inlet, the first chamber being in thermal contact with the heat exchanger portion; and wherein the blood circuit and the fluid circuit are in fluid isolation from each other inside the housing, characterized by a blood conduit for delivering the blood from the first chamber into a pump, the blood conduit extending through the heat exchanger portion and in thermal contact with the heat exchanger portion; and a second chamber for receiving the blood from the pump, the second chamber being within the heat exchanger portion and in thermal contact with the heat exchanger portion. a housing; a blood inlet to receive blood into the housing and a blood outlet for expelling the blood from the housing, the blood inlet and the blood outlet fluidly connected inside the housing via a blood circuit; a pump portion contained within the housing for extracting blood from and infusing blood to a patient's body, the pump portion defining the blood circuit inside the housing; and a heat exchanger portion contained within the housing for selectively heating or cooling the blood; wherein the heat exchanger portion is fluidly connected with at least one fluid inlet to receive a heat exchange fluid and at least one fluid outlet to expel the heat exchange fluid, the fluid inlet and the fluid outlet defining a fluid circuit therebetween; wherein the heat exchanger portion further comprises a plurality of heat exchange tubes operative for flowing the heat exchange fluid therethrough, the plurality of heat exchange tubes being in thermal contact with the blood circuit, wherein the heat exchange fluid flows within the tubes; wherein the blood circuit comprises a first chamber for receiving the blood from the blood inlet, the first chamber being in thermal contact with the heat exchanger portion; and wherein the blood circuit and the fluid circuit are in fluid isolation from each other inside the housing, characterized by a blood conduit for delivering the blood from the first chamber into a pump, the blood conduit extending through the heat exchanger portion and in thermal contact with the heat exchanger portion; and a second chamber for receiving the blood from the pump, the second chamber being within the heat exchanger portion and in thermal contact with the heat exchanger portion.