A surgical instrument comprising: a first cutting blade having a tubular body with a proximal end and a distal end, a cutting window disposed at a side of the first cutting blade near the distal end; a second cutting blade having a tubular body with a proximal end and a distal end, a cutting window disposed at a side of the second cutting blade near the distal end, the second cutting blade rotatably disposed inside of the first cutting blade such that the surgical instrument cuts tissue by rotating the second cutting blade within the first cutting blade while a vacuum is applied through an internal bore of the second cutting blade to draw the tissue into the cutting windows of the first and second cutting blades and sever the tissue by rotation of the second cutting blade; the distal end of the first cutting blade including a first suction aperture; and the distal end of the second cutting blade including a second suction aperture, the first and second suction apertures being aligned with each other such that an open suction passage exists between the internal bore and an area external of the surgical instrument through the first and second suction apertures while the second cutting blade does not rotate and while the second cutting blade rotates within the first cutting blade, whereby the surgical instrument can be used as a suction tool by applying the vacuum through the internal bore of the second cutting blade while the second cutting blade is stopped from rotating with the cutting windows of the first and second cutting blades misaligned with each other so that the vacuum is applied through the open suction passage, characterized in that a diameter of the first suction aperture is smaller than a diameter of the second suction aperture. a first cutting blade having a tubular body with a proximal end and a distal end, a cutting window disposed at a side of the first cutting blade near the distal end; a second cutting blade having a tubular body with a proximal end and a distal end, a cutting window disposed at a side of the second cutting blade near the distal end, the second cutting blade rotatably disposed inside of the first cutting blade such that the surgical instrument cuts tissue by rotating the second cutting blade within the first cutting blade while a vacuum is applied through an internal bore of the second cutting blade to draw the tissue into the cutting windows of the first and second cutting blades and sever the tissue by rotation of the second cutting blade; the distal end of the first cutting blade including a first suction aperture; and the distal end of the second cutting blade including a second suction aperture, the first and second suction apertures being aligned with each other such that an open suction passage exists between the internal bore and an area external of the surgical instrument through the first and second suction apertures while the second cutting blade does not rotate and while the second cutting blade rotates within the first cutting blade, whereby the surgical instrument can be used as a suction tool by applying the vacuum through the internal bore of the second cutting blade while the second cutting blade is stopped from rotating with the cutting windows of the first and second cutting blades misaligned with each other so that the vacuum is applied through the open suction passage, characterized in that a diameter of the first suction aperture is smaller than a diameter of the second suction aperture.