Perioperative Autotransfusion in Total Hip and Knee Arthroplasty

The Journal of Arthroplasty Vol. 21 No. 1 2006

Perioperative Autotransfusion in Total Hip and Knee Arthroplasty Charles R. Clark, MD,* Kevin F. Spratt, PhD,*y Martha Blondin, RN, MSN,* Steven Craig, BS,z and Linda Fink, RN, MSN*

Abstract: We assessed the OrthoPAT Orthopedic Perioperative Autotransfusion System (Zimmer Inc, Warsaw, Ind) in reducing the need for allogeneic blood in hip or knee arthroplasty. Patients (N = 398) were divided into 5 cohorts: unilateral primary hip (n = 131), unilateral revision hip (n = 38), unilateral primary knee (n = 179), unilateral revision knee (n = 26), and bilateral primary knee (n = 24). Primary or revision hip arthroplasties with no preoperative autologous blood donation, knee arthroplasties with no preoperative autologous blood donation, and unilateral primary hip arthroplasties were 2.7, 2.3, and 2 times less likely ( P b .05), respectively, to use allogeneic blood with OrthoPAT. We conclude that OrthoPAT use significantly reduced the risk of receiving allogeneic blood transfusions in defined patient subsets. Key words: arthroplasty, autotransfusion, hip, knee, OrthoPAT, perioperative. n 2006 Elsevier Inc. All rights reserved.

to justify in orthopedic surgeries. Alternatively, banked blood—either autologous or allogeneic— may be used in patients requiring transfusion. Unfortunately, allogeneic transfusions carry risks, albeit low, of viral disease transmission, allergic reactions, and posttransfusional immunosuppression [1-5]. To reduce patient exposure to allogeneic blood in orthopedic elective surgery, stimulation of hematopoiesis with administration of erythropoietin and iron before surgery [6] and various autologous blood options have been explored [7], including preoperative autologous blood donation (PAD) [8], acute normovolemic hemodilution [9-11], and perioperative red blood cell salvage [12,13]. Grosvenor et al [14] showed that postoperative blood salvage significantly ( P b .0001) reduced the risk of allogeneic transfusion among patients undergoing total hip arthroplasty, even in those who had donated autologous blood preoperatively. The rate of allogeneic blood transfusion in orthopedic surgery can be substantial. Blood management in patients undergoing total hip (3920 patients) or knee arthroplasty (5562 patients) was analyzed by Bierbaum et al [15] in a study involving

Perioperative salvage of blood involves the collection and reinfusion of autologous red blood cells lost by a patient during surgery. Blood salvage is not uncommon during major surgical procedures such as coronary artery bypass graft surgery or organ transplants. However, comparatively less blood is lost by patients undergoing hip or knee arthroplasty. Therefore, the use of blood salvage devices—which are typically cumbersome, difficult to use outside the operating room, and of questionable cost-effectiveness—is sometimes difficult

From the *University of Iowa Hospitals, Iowa City, IA; y Iowa Testing Programs, University of Iowa, Iowa City, IA, and z The Roy J. and Lucille A. Carver College of Medicine, The University of Iowa, Iowa City, IA. Submitted January 26, 2004; accepted January 25, 2005. Investigation was performed at the University of Iowa Hospitals, Iowa City, Iowa. This study was supported by Zimmer Inc, Warsaw, IN. Reprint requests: Charles R. Clark, MD, Departments of Orthopaedic Surgery and Biomedical Engineering, University of Iowa, 200 Hawkins Drive, no. 01075 JPP, Iowa City, IA 52242-1009. n 2006 Elsevier Inc. All rights reserved. 0883-5403/06/1906-0004$32.00/0 doi:10.1016/j.arth.2005.01.021

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24 The Journal of Arthroplasty Vol. 21 No. 1 January 2006 the practices of 330 orthopedic surgeons. Of the total patient population studied, almost half (46%) received a blood transfusion (57% in the hiparthroplasty cohort and 39% in the knee-arthroplasty cohort). Of the patients requiring transfusion, 34% received allogeneic blood (mean 2.1 U, range 1-16 U). Compared with patients who did not receive a transfusion, those who were transfused with allogeneic blood were more likely to have infection ( P V .001), fluid overload ( P V .001), and increased duration of hospitalization ( P V .01). These results suggest the need to explore new methods or devices to reduce the incidence of allogeneic blood transfusion in patients undergoing knee or hip arthroplasty. The OrthoPAT Orthopedic Perioperative Autotransfusion System (Zimmer Inc, Warsaw, Ind) represents a new alternative to perioperative blood salvage and infusion devices. The OrthoPAT system collects and cleanses red blood cells lost during and after surgery and is designed specifically to adapt to the perioperative intermittent blood loss experienced by patients undergoing orthopedic surgery. The adaptability of the device to both the intraoperative and postoperative environments suggests that it might help reduce the need for allogeneic blood transfusion in these patients. The primary purpose of this study was to evaluate the efficacy of the OrthoPAT blood salvage device in reducing the use of allogeneic blood in total hip and knee arthroplasties.

Patients and Methods Patient Population Patients who underwent elective total hip arthroplasty (unilateral primary or revision) or total knee arthroplasty (TKA) (unilateral primary or revision, or bilateral primary) were included from a single, large, orthopedic practice. Eligible patients were required to be sufficiently healthy to undergo total hip or knee arthroplasty. The study was approved by the investigational review board at the University of Iowa Hospitals. Study Design The patients were enrolled consecutively and divided into 5 main cohorts: (1) unilateral primary hip, (2) unilateral revision hip, (3) unilateral primary knee, (4) unilateral revision knee, and (5) bilateral primary knee. Analyses, described below, were done for subsets within each cohort by patient sex, age, body mass index, preoperative hemoglobin (Hb) and hematocrit (Hct), presence or

absence of PAD, and availability and use of the OrthoPAT device. There were no rigid criteria for the transfusion of allogeneic blood, although both surgical teams followed the same general protocol for transfusion. Generally, patients received allogeneic blood for an Hb/Hct less than 8.0/24 without symptoms or an Hb/Hct less than 10.0/30 with symptoms. Measurements The primary clinical outcome measured in this study was the perioperative use of allogeneic blood. A secondary measurement was the waste of predonated autologous blood (wasted blood). CHAID Modeling chi-Square automatic interaction detector (CHAID) analyses were performed to predict the use of allogeneic blood and the incidence of wasted blood—the 2 outcomes considered most relevant in evaluating the efficacy of the OrthoPAT. Separate models were planned for each cohort with sufficient size. Analyses were done using AnswerTree version 3.0 (SPSS Inc, Chicago, Ill). These analyses were done within the parameters noted below. CHAID modeling was used to evaluate potential interrelationships of multiple predictors and to estimate the accuracy of predicting the outcomes. Although relative risks (RRs) and odds ratios (ORs) provide useful information about individual predictors, these results can be difficult to interpret because the interrelationships among predictors are not considered. For example, sex and preoperative Hb and Hct levels might all be identified as significant risk factors for the use of allogeneic blood. However, sex might have been identified as a risk factor solely because women in the sample happened to have low preoperative Hb and/or Hct levels. One way to control for this type of problem is to consider multiple predictors simultaneously. Predictors and Outcomes. As indicated above, the outcomes of interest were use of allogeneic blood and incidence of wasted blood. The predictor set for these outcomes included 6 dichotomous variables (use of OrthoPAT [yes/no], blood donation [(yes/no], sex [male/female], surgeon [A/B], preoperative Hb [low/normal], and preoperative Hct [low/normal]) and 2 continuous variables (age and body mass index ). bLowQ for preoperative Hb and Hct was defined from sex-based norms. Low Hb was defined as b13.2 g/dL for men and b11.9 g/dL for women. Low Hct was defined as less than 40% for men and less than 35% for

Autotransfusion in Joint Arthroplasty ! Clark et al 25

women. When evaluating the incidence of wasted blood, blood donation was forced into the model before any other analysis because lack of donation forced the incidence of wasted blood to be. Training/Testing Sample Split. Reasonably large training sets relative to the number of variables considered in the model are important for establishing accurate models. Furthermore, the importance of validating the model established in the training sample to an independent testing sample is recognized as imperative in establishing the generalizability of the model. Although there is no well-established training/testing sample size ratio, with the given sample sizes available and the number of potential predictors available, a 70/30 random split of the data was considered appropriate for establishing training and testing samples. Node Size. CHAID is a methodology that attempts, in a hierarchical fashion, to identify variables (predictors) that will divide a data set into statistically significantly different subgroups. At any given point in the analysis, the data under consideration are a bparentQ node, and the resulting split(s) in that node are bchildQ nodes. In the next stage of the analysis, these child nodes are treated as parent nodes if analysis criteria are met. Because v 2 analyses are known to lose robustness when sample sizes per cell become less than 5, forcing parent nodes of 10 or greater are generally considered sufficient to permit a v 2 analysis to identify statistically significant data splits, especially if the resultant child nodes must contain 5 or more counts. Statistical Significance. The criteria for identifying child nodes were established as P values b.05. Statistical significance was not necessary to retain the parameter of blood donor status because this predictor was forced into the model for reasons noted earlier. Blood Salvage Device The OrthoPAT consists of single patient–use disposable sets and an electromedical device that collects and processes red blood cells. The device does not require a dedicated operator, weighs approximately 9 kg (20 lb), and can be mounted on a standard intravenous pole. The portability of this unit allows its use in both intraoperative and postoperative autotransfusion. The OrthoPAT uses a 2-L reservoir and can process up to 2 L of fluids per hour. A soft rubber diaphragm inflates like a balloon and draws 100 mL of blood into the dynamic disk centrifuge through a disposable plastic stopcock valve. Centrifugation at 5500 rpm for 90 seconds separates red blood cells from other

blood components, saline, bone chips, and other matter. Subsequent pressure applied to the bottom of the diaphragm pushes the supernatant fluid out until an optical sensor detects red blood cells and closes the valve. The fluid is replaced by clean saline for washing the red blood cells. After a second separation process, the cells are transported to a reinfusion bag. A complete cycle can be accomplished in approximately 5 minutes. Manufacturer specifications for this device include a red blood cell product Hct of 74.4% to 79.6%, red blood cell recovery of 75.6% to 98.2%, albumin removal of 93.9% to 99.6%, free Hb removal of 89.6% to 98.8%, and heparin removal of 96.9% to 100%.

Results Patient Disposition and Demographic Characteristics Between May 6, 1999, and May 30, 2001, a total of 398 patients undergoing unilateral primary hip arthroplasty (131 patients) or revision hip arthroplasty (38 patients), bilateral primary knee arthroplasty (24 patients), or unilateral primary knee arthroplasty (179 patients) or revision knee arthroplasty (26 patients) were enrolled consecutively in the study. Patient demographic data are summarized in Table 1. A total of 221 (55.5%) women and 177 (44.5%) men participated. Across the 5 cohorts, the percentage of men ranged from 33% (8 of 24) in the bilateral primary knee cohort to 65% (116 of 179) in the unilateral primary knee cohort. The mean age of patients ranged from 60 years in the unilateral primary hip cohort to 71 years in the unilateral knee revision cohort. Mean preoperative Hb and Hct levels exceeded 13.0 g/dL and 39%, respectively, across all cohorts. The incidences of low Hb and Hct levels were 22% and 24% for the unilateral primary hip cohort, 43% and 40% for the unilateral hip revision cohort, 18% and 18% for the unilateral primary knee cohort, 20% and 24% for the unilateral knee revision cohort, and 13% and 13% for the bilateral primary knee cohort, respectively. The OrthoPAT was available in 87.9% of cases in the study population and was used in 77.4% of cases. Patient Transfusion History The transfusion history for the patient population is presented in Table 2. Relatively few patients (18.8% [75 of 398]) participated in a PAD program, with 30.2% (120 of 398) of the sample receiving a perioperative transfusion. However, a substantial

26 The Journal of Arthroplasty Vol. 21 No. 1 January 2006 Table 1. Patient Demographics Parameter

Unilateral Primary Hip (n = 131)

Unilateral Revision Hip (n = 38)

Unilateral Primary Knee (n = 179)

Unilateral Revision Knee (n = 26)

Bilateral Primary Knee (n = 24)

54 (41) 71 (59)

23 (61) 15 (39)

116 (65) 63 (35)

16 (62) 10 (38)

8 (33) 16 (65)

60 (15) 28-88

61 (15) 33-87

65 (12) 34-89

71 (10) 49-87

62 (11) 38-82

30 (6) 18.6-46.9

30 (8) 19.5-68.6

34 (8) 19.4-53.3

33 (7) 21.2-46.3

31 (5) 21.4-41.0

14.0 (1.0) 9.4-17.2

12.9 (1.7) 9.7-17.2

13.5 (1.5) 9.2-18.0

13.2 (1.2) 10.3-15.3

14.3 (1.5) 12.4-17.5

40.9 (3.9) 28-50 27 (20.6)

39.1 (4.8) 29-51 5 (13.2)

40.7 (4.2) 28-54 35 (20.8)

40.0 (3.3) 32-46 3 (19.5)

42.9 (3.9) 37-52 5 (11.5)

85 79

97 65

86 79

95 70

92 82

Sex, n (%) Male Female Age (y) Mean (SD) Range BMI (kg/m2) Mean (SD) Range Hb* (g/dL) Mean (SD) Range Hct* (%) Mean (SD) Range PAD, n (%) OrthoPAT Available (%) Used (%)

Abbreviation: BMI, body mass index. *Preoperative.

portion (19.6% [78 of 398]) of patients required an allogeneic transfusion. Only 2 of the patients receiving allogeneic blood had participated in the PAD program. Approximately 41% (31 of 75) of the patients who donated blood preoperatively did not require a transfusion. Therefore, the incidence of wasted blood for those who participated in the PAD program was 41% (31 of 75). The transfusion history relative to OrthoPAT use is presented in Fig. 1. The OrthoPAT was used by approximately 80% of patients who did not require perioperative transfusion of allogeneic blood or predonated autologous blood (columns 1 and 3 in Fig. 1).

Table 3. The RRs of wasting autologous blood and of using banked blood with use of the OrthoPAT across the 5 cohorts are summarized in Table 4. Of particular interest are the results for these parameters in patients who underwent unilateral primary hip or knee arthroplasty. The RRs and, for

Risks of Wasting Autologous Blood and Using Banked Blood A summary of the use of banked blood and wasted blood across patient cohorts is presented in

Table 2. Transfusion History for All Patients Transfusion History No donation/no transfusion No donation/allogeneic transfusion Donation/no transfusion Donation/some autologous transfusion Donation/autologous and allogeneic transfusion Donation/complete autologous donation

Patients, n (%), N = 398 247 76 31 4 2

(62.1) (19.1) (7.8) (1.0) (b1.0)

38 (9.5)

Fig. 1. Transfusion history relative to OrthoPAT use. The percentage of OrthoPAT use was significantly different across the 6 transfusion history types, v25 = 42.6, P b .0001. Transfusion history categories: (1) no donation/no transfusion, (2) no donation/allogeneic transfusion, (3) donation/no transfusion, (4) donation/some autologous transfusion, (5) donation/autologous and allogeneic transfusion, and (6) donation/complete autologous transfusion.

Autotransfusion in Joint Arthroplasty ! Clark et al 27 Table 3. Use and Waste of Allogeneic Blood Across Cohorts Donated Blood: Yes

Cohort Unilateral primary hip Unilateral hip revision Unilateral primary knee Unilateral knee revision Bilateral primary knee All hips All knees

Donated Blood: No

Patients (n)

Wasted Donated Blood (%)

Patients (n)

Used Allogeneic Blood (%)

27

33

104

26

5

60

33

52

35

63

144

17

3

33

23

13

5

0

19

21

32 43

38 54

137 186

32 17

continuous predictors, the ORs associated with 8 selected predictors of banked blood use and incidence of wasted blood are presented for the unilateral primary hip cohort in Table 5 and the unilateral primary knee cohort in Table 6. Unilateral Primary Hip Arthroplasty. For patients who underwent unilateral primary hip arthroplasty, the blood donation rate was 21% (27 of 131 patients), the incidence of wasted blood was 33% (9 of 27 patients), and the use of banked blood was 22% (29 of 131 patients). Use of banked blood. For dichotomous predictors, use of the OrthoPAT produced a significant protective effect (RR 0.493, 95% confidence interval [CI] 0.26-0.93), indicating that patients undergoing surgery with the OrthoPAT were 2.03 (1/0.493)

times less likely to use banked blood than those undergoing surgery without the OrthoPAT. Low Hb (RR 2.52, 95% CI 1.37-4.63) and low Hct (RR 1.91, 95% CI 1.01-3.56) levels were significant risk factors for using banked blood. The patients’ sex (RR 1.71, 95% CI 0.89-3.24), which surgeon performed the procedure (RR 0.85, 95% CI 0.42-1.73), and whether preoperative autologous blood was donated (RR 0.23, 95% CI 0.07-1.13) were not predictive risk factors. For continuous predictors, an increase of 7.31 years was considered a significant increase in risk for using banked blood (OR 1.04, 95% CI 1.01-1.07), and an increase of 3.24 body mass index units was a significant protective effect for using banked blood (OR 0.89, 95% CI 0.81-0.98). Incidence of wasted blood. For dichotomous predictors, low Hct was a significant risk factor for wasting donated blood (RR 3.91, 95% CI 1.12-13.67). Wasting of donated blood was 3.91 times more likely in patients with low preoperative Hct levels than in patients with normal Hct levels. Moreover, donated blood was 6.25 (1/0.16) times less likely to be wasted from patients operated on by surgeon A compared with patients operated on by surgeon B (RR 0.16, 95% CI 0.04-0.61). This significant difference between surgeons appears to be related to the incidence of donated blood for surgeon A’s patients (3% [3 of 99 patients]) compared with surgeon B’s patients (19% [6 of 32 patients]). OrthoPAT use (RR undefined), patient sex (RR 0.40, 95% CI 0.08-1.83), PAD (RR undefined), and preoperative Hb (RR 2.85, 95% CI 0.82-9.94) were not predictive risk factors. For continuous predictors, neither age nor body mass

Table 4. RRs of Using Allogeneic Blood or Wasting Donated Blood Associated With Use of the OrthoPAT for 5 Patient Cohorts OrthoPAT

Used Allogeneic Blood

Wasted Blood

Cohort

Yes

No

RR

95% CI

Yes

No

RR

95% CI

Unilateral primary hip

Yes No Yes No Yes No Yes No Yes No Yes No Yes No Yes No

19 10 8 9 17 8 3 1 1 2 27 19 21 11 20 9

85 17 17 4 124 30 17 3 17 6 102 21 158 39 141 33

0.493

0.26-0.93 0.23-0.91

0.573

0.26-1.23

0.600

0.08-4.40

0.222

0.02-2.11

0.441

0.28-0.70

0.533

0.27-1.03

0.580

0.28-1.18

95 27 22 13 124 33 20 4 18 7 117 40 162 44 144 37

–

0.462

9 0 3 0 17 5 0 0 0 1 12 0 17 6 17 5

Unilateral hip revision Unilateral primary knee Bilateral primary knee Unilateral knee revision All hips All knees All primary knees

– 0.916

0.36-2.33

– – – 0.791

0.32-1.90

0.887

0.34-2.27

28 The Journal of Arthroplasty Vol. 21 No. 1 January 2006 Table 5. Unilateral Primary Hip Arthroplasty Patients’ RRs and ORs for Each Predictor for Both Allogeneic Blood and Wasted Blood Outcomes Used Allogeneic Blood Dichotomous Predictors OrthoPAT Yes No Sex Female Male Surgeon A B PAD Yes No Preop Hb (g/dL) Low Normal Preop Hct (%) Low Normal Continuous predictors Age (y) BMI (kg/m2)

Delta* NA

Yes

No

19 10

85 17

16 13

39 63

21 8

78 24

2 27

25 77

12 17

16 83

11 18

20 79

NA

95% CI

0.49

0.26-0.93

1.71

NA

0.85

NA

Wasted Blood

RR

0.23 2.52 1.91

Yes

No

RR

9 0

95 27

–

2 7

53 69

3 6

96 26

9 0

18 104

4 5

24 95

5 4

26 93

0.89-3.24 0.42-1.73 0.072-1.13

95% CI

0.40

0.08-1.83

0.16

0.04-0.61

–

1.37-4.63 1.01-3.56

2.85

0.82-9.94

3.91

1.12-13.67

Deltaa

OR

95% CI

OR

95% CI

7.31 3.24

1.04 0.89

1.01-1.07 0.81-0.98

0.97 1.05

0.92-1.01 0.95-1.17

Abbreviation: Preop, preoperative. *For continuous predictors, the use of 1 point of change, which is obvious for dichotomous variables, often has little meaning. The delta column in this table indicated the number of units of change associated with the computed odds ratio, where the unit of change was set at 0.5 of an SD.

index were significant risk factors. For age, an increase of up to 7.31 years was associated with an OR of 0.97 and a 95% CI of 0.92 to 1.01. For

body mass index, an increase of up to 3.24 U was associated with an OR of 1.05 and a 95% CI of 0.95 to 1.17.

Table 6. Unilateral Primary Knee Arthroplasty Patients’ RRs and ORs for Each Predictor for Both Allogeneic Blood and Wasted Blood Outcomes Used Allogeneic Blood Dichotomous Predictors OrthoPAT Yes No Sex Female male Surgeon A B PAD Yes No Preop Hb (g/dL) Low Normal Preop Hct (%) Low Normal Continuous Predictors Age (y) BMI (kg/m2)

Delta* NA

Yes

No

17 8

124 30

22 3

97 57

21 4

127 27

0 25

35 119

11 14

22 131

9 16

23 130

NA

95% CI

0.57

0.26-1.22

3.70

NA

1.10

NA

Wasted Blood

RR

Yes

No

17 5

124 33

14 8

105 52

18 4

130 27

22 0

13 144

7 15

26 130

6 16

26 130

1.15-11.86 0.40-2.98

– 3.45 2.57

RR

95% CI

0.92 –

0.36-2.32

0.88

0.39-1.99

0.94

0.34-2.59

– 1.72-6.91 1.25-5.28

2.05

0.90-4.63

1.70

0.72-4.03

Delta*

OR

95% CI

OR

95% CI

6.06 3.51

1.06 0.95

1.02-1.10 0.88-1.02

0.93 1.04

0.89-0.97 0.97-1.11

*For continuous predictors, the use of 1 point of change, which is obvious for dichotomous variables, often has little meaning. The delta column in this table indicated the number of units of change associated with the computed odds ratio, where the unit of change was set at 0.5 of an SD.

Autotransfusion in Joint Arthroplasty ! Clark et al 29

Unilateral Primary Knee Arthroplasty. For patients who underwent unilateral primary knee arthroplasty, the blood donation rate was 20% (35 of 179 patients), the incidence of wasted blood was 63% (22 of 35 patients), and the use of allogeneic blood was 14% (25 of 179 patients). Use of allogeneic blood. For dichotomous predictors, women were 3.7 times more likely than men

to use allogeneic blood (RR 3.70, 95% CI 1.1511.86). Moreover, low preoperative Hb (RR 3.45, 95% CI 1.72-6.91) and low preoperative Hct (RR 2.57, 95% CI 1.25-5.28) were both significant risk factors for use of allogeneic blood, which was consistent with the results for the unilateral primary hip cohort. Use of the OrthoPAT (RR 0.57, 95% CI 0.26-1.22) and which surgeon

Fig. 2. A, Decision-tree analysis for use of allogeneic blood in patients who underwent unilateral primary hip arthroplasty. B, Decision-tree analysis for use of allogeneic blood in patients who underwent unilateral primary knee arthroplasty. Abbreviation: Preop, preoperative.

30 The Journal of Arthroplasty Vol. 21 No. 1 January 2006

Fig. 2. (continued).

performed the procedure (RR 1.10, 95% CI 0.402.98) were not predictive risk factors. For continuous predictors, an increase of 6.06 years was considered a significant increase in risk for using banked blood (OR 1.06, 95% CI 1.02-1.10), but an increase of up to 3.51 body mass index units was not

a significant protective effect for using banked blood (RR 0.95, 95% CI 0.88-1.02). Incidence of wasted blood. None of the dichotomous predictors were significant, including use of the OrthoPAT (RR 0.92, 95% CI 0.36-2.32), sex (RR 0.88, 95% CI 0.39-1.99), different surgeons (RR

Autotransfusion in Joint Arthroplasty ! Clark et al 31 Table 7. Unilateral Primary Hip Cohort Results of CHAID Analysis Predicting Incidence of Use of Allogeneic Blood CHAID-Based Decision-Tree End Points Donor

Preop Hb

OrthoPAT

Yes – No Low No Normal No Normal No Normal Percent correct prediction for the model

– – No Yes Yes with (SE)

Correct Prediction Rates for No Use of Allogeneic Blood Age – – – N68 V68

Training (% [n/N]) 89 14 44 65 97 84.3%

(17/19) (2/14) (4/9) (11/17) (35/36) (3.7%)

Testing (% [n/N]) 100 100 66 100 86 77.8

(8/8) (4/4) (2/3) (6/6) (13/15) (6.9%)

Abbreviation: SE, standard error of estimate.

0.94, 95% CI 0.34-2.59), PAD (RR undefined), preoperative Hb (RR 2.05, 95% CI 0.90-4.63), and preoperative Hct (RR 1.70, 95% CI 0.72-4.03). For the continuous predictors, an increase of 6.06 years was considered a significant protective effect for using allogeneic blood (OR 0.93, 95% CI 0.89-0.97), but an increase of up to 3.51 body mass index units was not a significant protective effect for incidence of wasted blood (RR 0.95, 95% CI 0.88-1.02). CHAID Modeling Wasted Blood. The CHAID-based decision-tree analysis that modeled the incidence of wasted autologous blood in the unilateral primary hip cohort showed that donated blood (yes/no) was the only significant predictor ( P b .0001). By definition, the incidence of wasted autologous blood was 0% for patients who did not donate. The incidence of wasted autologous blood for those who did donate was 28% (5 of 18 patients) in the training sample and 44% (4 of 9 patients) in the testing sample. The CHAID-based decision-tree analysis that modeled the incidence of wasted autologous blood in the unilateral primary knee cohort indicated that donated blood ( P b .0001) and patient age ( P b .05) were significant predictors. The incidence

of wasted autologous blood for patients older than 60 years was 43% (6 of 14) in the training sample and 50% (1 of 2) in the testing sample. For patients 60 years or younger, the incidence of wasted autologous blood was 100% (12 of 12) in the training sample and 43% (3 of 7) in the testing sample. Use of Allogeneic Blood. The CHAID-based decision-tree analyses that modeled the use of allogeneic blood in the unilateral primary hip and the unilateral primary knee cohorts are presented in Fig. 2A and B, respectively. Key results from these analyses are summarized in Table 7 for the hip and Table 8 for the knee. Unilateral primary hip arthroplasty. In this cohort, when patients donated blood preoperatively, the use of allogeneic blood was low (11% [2 of 19 patients] in the training samples and 0% [0 of 8 patients] in the testing samples). When no preoperative donation was involved, low preoperative Hb was a significant risk factor for the use of allogeneic blood: in the training sample, 86% (12 of 14) of patients with low Hb required allogeneic blood compared with 19% (12 of 62) of those with normal Hb (RR 4.43, 99.9% CI 1.75-11.17). However, none of the 4 patients in the testing sample used allogeneic blood. Importantly, when no preoperative blood donation was involved, and preoperative Hb levels were within

Table 8. Unilateral Primary Knee Cohort Results of CHAID Analysis Predicting Incidence of Use of Allogeneic Blood CHAID-Based Decision-Tree End Points Donor

Preop Hb

OrthoPAT

Yes – – No Low – No Normal Yes No Normal No No Normal No Percent correct prediction for the model with (SE)

Correct Prediction Rates for No Use of Allogeneic Blood Sex – – – Male Female

Training (% [n/N]) 100 62 93 100 55 87.5%

(23/23) (10/16) (66/71) (6/6) (6/11) (2.7%)

Testing (% [n/N]) 100 38 88 100 83 82.7%

(12/12) (3/8) (22/25) (1/1) (5/6) (5.2%)

32 The Journal of Arthroplasty Vol. 21 No. 1 January 2006 the reference range, patients who did not use the OrthoPAT were 2.7 times more likely to use allogeneic blood than those who did use the OrthoPAT (95% CI 1.01-7.24), with 56% in the training sample and 33% in the testing sample using allogeneic blood. Finally, a subset of patients was identified who used the OrthoPAT with no prior blood donation and had normal preoperative Hb levels. In this subpopulation, patients who were older than 68 years were 12.7 times more likely to use allogeneic blood than patients who were younger than 68 years (95% CI 1.66-97.54). Allogeneic blood was not used by 11 of 17 patients in the training sample and 6 of 6 in the testing sample. For patients in this subset who were younger than 68 years, allogeneic blood was not used by 35 of 36 in the training sample and 13 of 15 in the testing sample. Unilateral primary knee arthroplasty. In this cohort, no allogeneic blood was required for patients who donated blood preoperatively. When no preoperative donation was involved, low preoperative Hb was a significant risk factor for use of allogeneic blood: in the training sample, 38% (6 of 16) of the patients with low Hb used allogeneic blood, compared with 11% (10 of 88) of those with normal Hb (RR 3.67, 95% CI 1.55-8.71). In the testing sample, 62% (5 of 8) of patients with low Hb compared with 12% (4 of 32) of patients with normal Hb used allogeneic blood (RR 5.00, 95% CI 1.73-14.46). When no preoperative donation was involved and preoperative Hb levels were in the normal range, patients not using the OrthoPAT were 4.2 times more likely to use allogeneic blood than patients using the OrthoPAT (95% CI 1.3612.81). In the testing sample, this RR was not significant (RR 0.84, 95% CI 0.10-6.87). Under operative conditions in which the patient had normal preoperative Hb levels and there was no blood donation and no OrthoPAT use, no allogeneic blood was required for any of the male patients in either the training (6 of 6) or the testing (1 of 1) phase of the model. For women, however, incidence of allogeneic blood use was relatively high in the training sample (5 of 11) but lower in the testing sample (1 of 6).

Discussion Patients undergoing major orthopedic procedures such as total hip or knee arthroplasty are at risk for transfusion of allogeneic blood. Various blood conservation and blood management strategies are available to the orthopedic surgeon to

reduce the patient’s risk for allogeneic blood transfusion, including perioperative blood salvage and reinfusion (autotransfusion). Autotransfusion is indicated when (1) the patient is expected to lose sufficient blood during the perioperative period to require a red blood cell transfusion, and autotransfusion will likely reduce or eliminate the need for donor blood; (2) religious beliefs prevent the patient from using donor blood, but allow the patient to accept autologous blood; (3) compatible donor blood is not available; (4) the patient cannot donate sufficient quantities of autologous blood before surgery to satisfy the anticipated transfusion requirement; or (5) the patient or physician prefers perioperative autotransfusion to PAD or transfusion of donor blood. Several factors have an impact on the need for perioperative blood transfusion in patients undergoing total joint arthroplasty. Pola et al [16] have shown that age, sex, hypertension, and body mass index have a synergistic effect on the risk of transfusion in patients undergoing elective total hip arthroplasty. They believe that the simultaneous analysis of these parameters might help to stratify patients with different risks for transfusion and may increase the efficacy and reduce the cost of blood ordering practices associated with total hip arthroplasty. Hatzidakis et al [17] have shown that the efficacy of collection of autologous blood can be improved by identifying patients with a very low risk of transfusion. They found that patients who had an initial Hb of at least 150 g/L or an initial Hb level of between 130 and 150 g/L and an age younger than 65 years have a minimal risk of needing a transfusion. There are several strategies for perioperative blood management. These include PAD, the use of recombinant human erythropoietin, intraoperative blood collection, and reinfusion, as well as intraoperative and postoperative blood collection and reinfusion. Billote et al [18] performed a prospective randomized study of PAD for hip arthroplasty surgery and concluded that PAD provided no benefit for nonanemic patients undergoing primary total hip arthroplasty surgery. Furthermore, they stated that PAD increased the likelihood of autologous transfusion, wastage of predonated units, and cost. Note that we had a similar transfusion trigger to that of Billote et al; we usually did not transfuse asymptomatic patients with an Hct greater than 8 g/dL or an Hct greater than 24%. The low hgb/hct trigger used in both studies likely relates to the high rates of wasted blood. Woolson and Wall [19] evaluated the transfusion of autologous blood after TKA. They found that postoperative unwashed

Autotransfusion in Joint Arthroplasty ! Clark et al 33

blood salvage was as effective as predonated autologous blood in preventing the risk associated with allogeneic blood after TKA. Bezwada et al [20] found that the preoperative use of erythropoietin in conjunction with PAD reduced the need for allogeneic blood transfusion associated with total joint arthroplasty more effectively than did either erythropoietin or PAD alone. Zarin et al [21] studied the efficacy of intraoperative blood collection and reinfusion in patients undergoing revision total hip arthroplasty and found that the intraoperative collection and reinfusion substantially decreased net perioperative blood loss in patients who had a revision of both components and in those who had revision of the acetabular component alone. They concluded that the use of intraoperative blood collection and reinfusion appears to be a valuable method of preserving blood volume in the perioperative period. An overall blood management strategy appears to be important in reducing the use of allogeneic blood. Pierson et al [22] found that the use of their blood conservation algorithm resulted in a significant reduction in the need for allogeneic blood transfusion after unilateral total hip and knee arthroplasties. A distinct advantage of perioperative reinfusion of blood is that erythrocyte viability in salvaged blood typically exceeds that of the minimum viability of that in allogeneic blood. Colwell et al [23] studied erythrocyte viability in salvaged blood and found that the mean erythrocyte viability was 88.0% F 3.8% as opposed to the Standard of the American Association of Blood Banks where the minimal erythrocyte viability inadequately crossmatched blood or predeposited autologous blood with 70%. They concluded that the intraoperative salvage was a valuable adjunct to other blood management strategies in patients having total joint arthroplasty. The present study was designed to assess the efficacy of the OrthoPAT in reducing the need to use allogeneic blood in total hip or knee arthroplasty. The results of the RR analysis reported herein demonstrated that patients who did not donate autologous blood preoperatively and underwent knee or hip arthroplasty were 2 to 3 times less likely ( P b .05) to use allogeneic blood if the OrthoPAT was used perioperatively. Friederichs et al [24] had similar findings in their study of perioperative blood salvage as an alternative to predonating blood for primary total knee and hip arthroplasties. They concluded that perioperative blood salvage is safe and cost-effective and makes it possible to discontinue the practice of predonating blood for primary total knee and hip

arthroplasties in patients with a preoperative Hct greater than 37%. Although this reduction in the use of allogeneic blood was statistically significant and clinically relevant, it was not dramatically so. Furthermore, there are certain limitations in the study design. For example, the study was not controlled or randomized. Moreover, assessments were limited to knee and hip procedures in the practices of 2 surgeons, with one contributing the majority of the cases. Thus, extrapolation of these results to a broader array of orthopedic surgical procedures and surgeons must be done with caution. Nevertheless, the results obtained with the OrthoPAT in this study are encouraging for hip and knee arthroplasty cases in which surgeons may use similar case management techniques. In addition, use of the device may have implications for cost savings. Although a formal cost analysis has not been done, potential areas for cost savings were identified as eliminating the need for a dedicated operator and eliminating the need for the orthopedic surgeon’s office staff and hospital staff to arrange for preoperative blood donation by the patient. In addition, the OrthoPAT system is designed with a single disposable set that can be used perioperatively and is therefore less costly than separate sets for intraoperative and postoperative salvage. Furthermore, salvaging of red blood cells occurs only when the observed blood that was lost is replaced only with the blood that was lost, which likely makes autotransfusion cost-effective when compared with intraoperative or postoperative transfusion of donor units. In the authors’ institution, the charge for collecting, processing, typing, screening, and transfusing 2 U of autologous blood is between US$981 and US$1077. A recent report evaluated the broad implementation of the OrthoPAT in a community hospital setting [25]. The OrthoPAT has been used for all joint arthroplasty surgeries at the hospital since October 1999. There has been a low rate of allogeneic blood transfusion (10.5% for TKA and 7.7% for total hip arthroplasty); no transfusion reactions have been reported, and in elective joint arthroplasty patients, postoperative Hct has been maintained at a level that is generally asymptomatic. Using perioperative blood management strategies is important to reduce the risk for transfusion, to maximize Hb status, and to have a positive effect on early and long-term outcomes in patients undergoing total hip or knee arthroplasty. At the authors’ institution, emphasis is placed on developing a plan specific to each patient [26]. Patients are categorized as high risk for transfusion (eg, difficult

34 The Journal of Arthroplasty Vol. 21 No. 1 January 2006 revision surgery) or low risk for transfusion (eg, routine primary hip or knee arthroplasty). If the patient is categorized as low risk and has an Hb level greater than 13 g/dL, the use of perioperative blood salvage with the OrthoPAT, normovolemic hemodilution, or PAD is recommended. If the patient is low risk and has an Hb level less than 13 g/dL, the options include preoperative treatment with erythropoietin alpha, PAD, or perioperative use of the OrthoPAT. Use of the OrthoPAT is strongly considered in all patients undergoing total hip arthroplasty, revision TKA, and bilateral hip or knee arthroplasty. In appropriate patients, use of the OrthoPAT can replace the use of autologous donated blood, allow patients to enter their surgery with a normal Hct, and lessen their chance of receiving a blood transfusion. Further studies to substantiate the benefits of the OrthoPAT might include using a research instrument that assesses postoperative vigor in patients undergoing elective total joint arthroplasty [27]. In conclusion, perioperative use of the OrthoPAT during total knee or hip arthroplasty can significantly reduce the risk of receiving allogeneic blood transfusions for several defined subsets of patients. Future studies should be directed to further define those patients most likely to benefit from use of the OrthoPAT and assess the attendant cost savings to the healthcare system.

Acknowledgments The authors acknowledge the efforts of Carol Strabala, RN, BSN, and Susan Dean, RN, BSN, in the collection of data.

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