Letter to the Editor
Clinics in Orthopedic Surgery 2017;9:126-128 • https://doi.org/10.4055/cios.2017.9.1.126
Blood Transfusion Rates as a Primary Outcome Measure: The Use of Predetermined Triggers and Display of Clinical Indications in Providing Accurate Comparative Transfusion Rates David Skipsey, MBChB*, Felix Allen, MBBS*, Anwar Hussein, FRCA*, Deiary Kader, MBChB*, Tomislav Smoljanovic, MD*,† *The South West London Elective Orthopaedic Centre, Epsom and St Helier University Hospitals NHS Trust, Surrey, UK, Department of Orthopaedic Surgery, University Hospital Center Zagreb, School of Medicine, Zagreb University, Zagreb, Croatia
†
To the Editor: We read with interest the paper by Kamath et al.1) on the efficacy of saline-coupled bipolar sealing devices in simultaneous bilateral total knee arthroplasty (TKA). The use of bipolar sealing and conventional electrocautery was compared in 71 consecutive patients who underwent bilateral TKA. Unfortunately, it must be noted that there are discrepancies in the reported transfusion rates. It was stated in the results section of the abstract that patients treated with the bipolar sealer were 35% less likely to require a transfusion when compared with patients treated with conventional electrocautery. The same percentage (35%) was presented in the conclusion section of the article. In contrast, the authors state that in their discussion that the blood transfusion rates were 33% lower in the experimental bilateral group when compared with the control group. The results section of the article and Table 2 claim that 55% (16 of 29) of patients in the experimental cohort required a blood transfusion, while the rate was 83% (35 of 42) in the control group. Therefore, the difference in transfusion requirements between the two groups would be 28% and not the 35% or 33% stated elsewhere in the paper. The need for blood transfusion was determined in the study based upon clinical need as determined by the surgeon and medical co-management team. This included consideration of pertinent medical comorbidities (e.g., strong history of cardiac disease), clinical symptoms such as lethargy, and hemodynamic parameters such as tachycardia and/or hypotension refractory to initial fluid resuscitation. In general, patients without cardiac history were not transfused for a haemoglobin level greater than 8 g/dL. Fixed, predetermined transfusion triggers were not employed, allowing the need for transfusion to appear vague
in nature. As stated as a limitation, the staff and surgeons were not blinded and therefore there was a possibility of bias in the decision making process but the authors state that the criteria for transfusing symptomatic patients was used consistently. It is interesting to note that patients who were treated with the bipolar sealing device when compared with patients in the control group had: matched demographics, similar preadmission haemoglobin level (13.5 g/dL vs. 13.3 g/dL), similar estimated blood loss (100 mL) and nonsignificant increased haemoglobin decline (4.2 g/dL vs. 4.8 g/dL), yet finished with the significantly less transfusion requirements.1) It is unclear why there should be a significant difference in transfusion rates when other parameters were similar. One potential explanation for this could be age. It is known that transfusion requirement after major joint arthroplasty is greater in the elderly.2) We note that the control group probably contained a greater number of more elderly patients compared with the experimental group (63.4 ± 17.9 vs. 59.1 ± 4.1), and it would be interesting to know the ages of those that required transfusions as a possible explanation to account for the differences between the two groups. Another possible explanation could be the contribution of dilutional anaemia, and it would be useful to know if there were any differences in the perioperative use of intravenous fluid between the two groups. The overall transfusion requirements found in this study are different to those experienced in our clinical practice. An analysis of bilateral TKA performed at our institution is presented in Table 1. A saline-coupled bipolar sealing device was not used in any of the cases. Our centre employs a fairly restrictive transfusion policy and is governed by a team of senior intensive care specialists who
Copyright © 2017 by The Korean Orthopaedic Association
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Clinics in Orthopedic Surgery • pISSN 2005-291X eISSN 2005-4408
127 Letter to the Editor Clinics in Orthopedic Surgery • Vol. 9, No. 1, 2017 • www.ecios.org
Table 1. Preoperative Patient Characteristics and Perioperative Haemodynamic Values* Variable
SWLEOC (n = 36)
†
Age (yr)
2‡
Body mass index (kg/m ) §
ASA classification Male sex
Preadmission haemoglobin (g/dL)
59.1 ± 4.1
31.0 (32.0–27.0)
32.4 (29.2–38.9)
35.0 (31.4–42.9)
2.0 ± 0.38
2.58 ± 0.55
2.59 ± 0.5
13.8 ± 3.7
‡
Units of blood transfused
> 2 Units of blood transfused ‡
Discharge haemoglobin (g/dL) Haemoglobin decline (g/dL)† Operative time (min)†
16 (38%)
14 (48%)
13.3 ± 0.5
13.5 ± 0.4
6 (17%)
35 (83%)
16 (55%)
0 (0–0)
2 (2–2)
1 (0–2)
2 (6%)
8 (19%)
2 (6.9%)
50 (50–100)
Estimated blood loss (mL)
Bipolar sealer group (n = 29)
63.4 ± 17.9
Transfusion required
‡,ΙΙ
Control group (n = 42)
69.9 ± 2.8
17 (47.2%) †
Kamath et al.1)
10.1 (9.6–10.9)
100 (42.5–150)
100 (75–200)
9.4 (8.7–10.1)
9.1 (8.7–9.4)
3.4 ± 4.0
4.2 ± 0.5
4.8 ± 0.4
154.1 ± 10.5
174 ± 8.7
196 ± 15.5
The table is displayed with the same units and descriptive statistics as the original paper. ASA: American Society of Anesthesiologists, SWLEOC: South West London Elective Orthopaedic Centre. *The values of patients who underwent bilateral total knee arthroplasty under the care of five surgeons at the SWLEOC over 2-year period (2014.6.1–2016.5.31). Values are presented as †mean ± 95% confidence interval, ‡median (interquartile range), §mean ± standard deviation. ΙΙ Intraoperative blood loss is reported as categorical values (minimal, < 100 mL, < 200 mL, < 500 mL). The upper limits were used for calculation and the minimal category was given a value of 50 mL for calculation.
work as perioperative physicians. In general, transfusion is avoided in patients with a haemoglobin level > 8 g/dL and used in all patients with a haemoglobin level < 6 g/dL. For those in between, the decision to transfuse is based on patient factors such as comorbidity and cardiorespiratory risk, ongoing blood loss, and symptoms related to anaemia. Haemoglobin levels between 8–10 g/dL, but who experience symptomatic anaemia despite an adequate circulatory volume. The transfusion protocol is similar to the protocol presented in the Levine et al.3) Our transfusion rate was much lower at 17% compared with 55% and 83% rates reported by Kamath et al.1) respectively (Table 1). Whilst stringent parameters are at odds with an individual patients needs based on the clinical picture, it would seem prudent that studies which use transfusion rates as the primary outcome should set fixed parameters. In cases where the parameters were not followed due to clinical need, a summary of indications could be included which would allow a clearer picture and explain results such as those found by Kamath et al.1)
CONFLICT OF INTEREST No potential conflict of interest relevant to this article was reported.
REFERENCES 1. Kamath AF, Austin DC, Derman PB, Clement RC, Garino JP, Lee GC. Saline-coupled bipolar sealing in simultaneous bilateral total knee arthroplasty. Clin Orthop Surg. 2014;6(3):298-304. 2. Dan M, Liu D, Martos SM, Beller E. Intra-operative blood salvage in total hip and knee arthroplasty. J Orthop Surg (Hong Kong). 2016;24(2):204-8. 3. Levine BR, Haughom B, Strong B, Hellman M, Frank RM. Blood management strategies for total knee arthroplasty. J Am Acad Orthop Surg. 2014;22(6):361-71.
Received September 11, 2016; Accepted December 27, 2016 Correspondence to: David Skipsey, MBChB The South West London Elective Orthopaedic Centre, Epsom and St Helier University Hospitals NHS Trust, Dorking Road, Epsom, Surrey, KT18 7EG, UK Tel: +44-13-7273-5825, Fax: +44-13-7273-5815 E-mail:
[email protected] https://doi.org/10.4055/cios.2017.9.1.126
128 Letter to the Editor Clinics in Orthopedic Surgery • Vol. 9, No. 1, 2017 • www.ecios.org
Atul F. Kamath, Daniel C. Austin, Peter B. Derman, R. Carter Clement, Jonathan P. Garino, Gwo-Chin Lee, Reply: We thank the readers for their letter to the editor, and for interest in our manuscript published in 2014. Issues surrounding blood management continue to be an important part of the global care of total joint arthroplasty patients as we move into 2017. In addition to our group’s multiple studies on the use of bipolar sealing devices in joint arthroplasty,1,2) we continue to examine our blood management and transfusion practices. We now routinely employ the use of tranexamic acid, which has further allowed a reduction in transfusion requirements. This may account for some of the differences between contemporary rates of transfusion, and historical rates presented before the routine use of tranexamic acid. We thank the readers for inquiring about the transfusion reduction rates as presented in our manuscript. The absolute reduction in transfusion rate was 83% to 55%, a difference of 28% points. The relative reduction as a percentage of the original transfusion rate of 83% would be approximately 35%. In a simpler comparison, for example, if the transfusion rate was reduced from 10% to 5%, we would have stated that there was an absolute reduction of 5% but a 50% reduction from the baseline rate (5%/10% = 0.5). In our manuscript, we acknowledge some of the limitations discussed by the readers’ letter to the editor. This study was not a prospective randomized controlled trial, and therefore issues of blinding and randomization do not apply. Rather, our study has important applications for real-world transfusion scenarios based on clinical scenario and patient comorbid conditions. We thank the readers for sharing their own data and algorithm for management, which, like our practice, involves careful evaluation of “comorbidity and cardiorespiratory risk, ongoing blood loss, and symptoms related to anaemia.” Likewise,
confounders of age and dilutional anaemia are important considerations in any study of blood management, but are not controlled for in our clinical practice review. Again, we thank the readers for their letter to the editor, as well as their own institutional efforts to examine transfusion thresholds, understand adjunctive tools in blood management, and further the perioperative care of total joint patients.
CONFLICT OF INTEREST No potential conflict of interest relevant to this article was reported.
REFERENCES 1. Derman PB, Kamath AF, Lee GC. Saline-coupled bipolar sealing in revision total knee arthroplasty for infection. Am J Orthop (Belle Mead NJ). 2013;42(9):407-11. 2. Clement RC, Kamath AF, Derman PB, Garino JP, Lee GC. Bipolar sealing in revision total hip arthroplasty for infection: efficacy and cost analysis. J Arthroplasty. 2012;27(7):1376-81.
Correspondence to: Atul F. Kamath, MD Department of Orthopaedic Surgery, Pennsylvania Hospital, 800 Spruce Street, Philadelphia, PA 19107, USA Tel: +1-215-687-8169, Fax: +1-215-829-7492 E-mail:
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