title: Blood-gas and circulatory changes during total knee replacement. Role of the intramedullary alignment rod.
abstract: The use of an intramedullary alignment rod in the distal part of the femur is an important step in performing total knee-replacement arthroplasty. On the basis of our observation of a sudden decrease in oxygen saturation in some patients after insertion of the rod, a prospective study was done of the circulatory and blood-gas changes that were associated with insertion in thirty-five patients. We examined the effects of the use of an eight-millimeter solid alignment rod, with and without venting; an eight-millimeter fluted alignment rod, with venting; and an eight-millimeter fluted or solid alignment rod, inserted through a 12.7-millimeter drill-hole, but without other venting. A statistically significant reduction in oxygen saturation, arterial oxygen tension (PaO2), and end-tidal carbon-dioxide tension (PETCO2) occurred after insertion of both solid and fluted eight-millimeter alignment rods through an eight-millimeter hold in both vented and unvented femoral canals, in association with a significant increase (p less than 0.01) in intramedullary pressure. Bone-marrow contents and fat were retrieved from samples of blood from the right atrium, indicating that embolization of marrow contents had occurred during insertion of the alignment rod. A small decrease in systemic blood pressure and heart rate also occurred. These changes were completely eliminated by the use of a 12.7-millimeter drill-hole as the entry site of the eight-millimeter fluted rod. We concluded that insertion of an intramedullary alignment rod in the femur causes embolization of marrow contents, which decreases arterial oxygen tension, oxygen saturation, end-tidal carbon-dioxide tension, arterial blood pressure, and heart rate.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Anaesthesia, Massachusetts General Hospital, Boston 02114.
authors.forename: N R
authors.initials: NR
authors.lastname: Fahmy
authors.forename: H P
authors.initials: HP
authors.lastname: Chandler
authors.forename: K
authors.initials: K
authors.lastname: Danylchuk
authors.forename: E B
authors.initials: EB
authors.lastname: Matta
authors.forename: N
authors.initials: N
authors.lastname: Sunder
authors.forename: J M
authors.initials: JM
authors.lastname: Siliski
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D016275:Atrial Function; D001794:Blood Pressure; D001853:Bone Marrow / Q000502:physiology; D002245:Carbon Dioxide / Q000097:blood*; D005260:Female; D006339:Heart Rate; D006439:Hemodynamics; D006801:Humans; D007719:Knee Joint / Q000601:surgery; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood*; D011312:Pressure
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen