Some blood loss following total knee arthroplasty is unavoidable and is often in excess of one liter when both intraoperative and postoperative bleeding are included. Minimizing blood loss and the adverse events that may be associated with acute postoperative anemia and its treatment is of paramount importance to ensuring the best possible outcome for our patients.
In their meta-analysis of randomized controlled clinical trials, Rama et al. attempted to delineate the role of timing of tourniquet release in total knee arthroplasty as it pertains to blood loss and postoperative wound complications. On the basis of this meta-analysis, the authors concluded that "early tourniquet release for hemostasis increases the blood loss associated with primary knee arthroplasty." However, the authors also noted that tourniquet release after wound closure increases the risk of early postoperative complications requiring another operation. To appreciate the findings of this study, it is useful to consider the relevant factors that affect blood loss following total knee arthroplasty.
The type of anesthetic administered may play a role in total blood loss. In total knee arthroplasty, hypotensive epidural anesthesia without the use of a tourniquet was found to be associated with a significant decrease in transfusion requirements when compared with spinal anesthesia with a tourniquet (p < 0.005)1. In fact, the use of an arterial tourniquet as a technique of blood conservation in total knee arthroplasty is questionable, given the available evidence in the literature. In a prospective study by Tetro and Rudan of tourniquet use with regard to blood loss in total knee arthroplasty, no difference in blood loss or transfusion rates was noted2. If a tourniquet is used in conjunction with hypotensive epidural anesthesia, it is noteworthy that reflex hypotension occurs within one minute of tourniquet release3, which, if managed by a chemically induced normotensive state, may obviate the benefit of the reduction of blood loss with hypotensive anesthesia. Unfortunately, one of the weaknesses of the meta-analysis by Rama et al. is the lack of specific reporting and analysis with respect to the type of anesthesia utilized in the various clinical trials, leaving us unsure how the anesthetic technique affected the conclusions drawn by the authors.
The decision to use a drain as well as the manner in which the drain is employed has also been implicated as having a role in determining total blood loss. A meta-analysis published in 2004 found closed suction drainage to be associated with higher blood transfusion rates, with no associated benefit regarding wound complication rates4. If a drain is used, delayed release of the drain clamp after tourniquet deflation has been associated with a significant decrease in postoperative blood loss (p < 0.001)5. One might also assume that the timing of drain removal might affect postoperative blood loss. The drain protocol used in the randomized control trials included in this meta-analysis was unclear in three studies, variable (depending on drainage and time) in two studies, and standardized (with some variability) in the remaining six studies. Therefore, without a standardized drain protocol, the calculation of total blood loss may vary considerably.
Compressive dressings, when properly applied, may also affect postoperative blood loss by decreasing the intra-articular volume required to reach tamponade pressures6. Along the same lines, limb position after knee arthroplasty has been shown to affect blood loss. Ong and Taylor found that knee flexion at 70° or knee elevation by maintaining hip flexion at 35° (with the knee in extension) resulted in a 25% reduction in hemoglobin loss7. In the meta-analysis by Rama et al., no information is given regarding types of dressings, limb position, or postoperative rehabilitation protocols with the notable exception that, in one study, continuous passive motion was initiated in the recovery room in one group but delayed until the third postoperative day in the other.
Chemical thromboprophylaxis differed considerably among the included studies. No thromboprophylaxis was used in one study; aspirin, in one study; warfarin, in one study; and low-molecular-weight heparin, in five studies. The method was unspecified in two studies. One study actually used low-molecular-weight heparin in one arm of the study and not the other. Clearly, the use of anticoagulation or a more potent anticoagulant may result in a greater amount of postoperative blood loss. The timing of the administration of such agents is also critical to the amount of bleeding that occurs. None of the above issues were definitively evaluated in the meta-analysis of Rama et al.
While the authors are to be commended on their attempt to bring clarity to such an important topic, far too many variables are nonstandardized and uncontrolled to truly address the specific question of timing of tourniquet release and blood loss following total knee arthroplasty. Unfortunately the diversity in methodology and quality of the available studies limits the significance of their findings, particularly given the complex interplay of factors relating to blood loss in total knee arthroplasty. Although the conclusion drawn by these authors is useful—that late release of the tourniquet results in an increased risk of complications leading to secondary surgery—the real take-home message lies in their final paragraph, in which they comment that "The inadequate reporting and methodology in many of the studies in this meta-analysis justify additional randomized trials…"
*The authors did not receive any outside funding or grants in support of their research for or preparation of this work. Neither they nor a member of their immediate families received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, division, center, clinical practice, or other charitable or nonprofit organization with which the authors, or a member of their immediate families, are affiliated or associated.
1. Juelsgaard P, Larsen UT, Sorensen JV, Madsen F, Soballe K. Hypotensive epidural anesthesia in total knee replacement without tourniquet: reduced blood loss and transfusion. Reg Anesth Pain Med. 2001;26:105-10.
2. Tetro AM, Rudan JF. The effects of a pneumatic tourniquet on blood loss in total knee arthroplasty. Can J Surg. 2001;44:33-8.
3. Kahn RL, Marino V, Urquhart B, Sharrock NE. Hemodynamic changes associated with tourniquet use under epidural anesthesia for total knee arthroplasty. Reg Anesth. 1992;17:228-32.
4. Parker MJ, Roberts CP, Hay D. Closed suction drainage for hip and knee arthroplasty. A meta-analysis. J Bone Joint Surg Am. 2004; 86:1146-52.
5. Roy N, Smith M, Anwar M, Elsworth C. Delayed release of drain in total knee replacement reduces blood loss. A prospective randomised study. Acta Orthop Belg. 2006;72:34-8.
6. Charalambides C, Beer M, Melhuish J, Williams RJ, Cobb AG. Bandaging technique after knee replacement. Acta Orthop. 2005;76:89-94.
7. Ong SM, Taylor GJ. Can knee position save blood following total knee replacement? Knee. 2003;10:81-5.