Does Preoperative Hemoglobin Value Predict Postoperative Cardiovascular Complications after Total Joint Arthroplasty? Kishor Gandhi MD, MPH, Eugene Viscusi MD, Luis Pulido MD, and Javad Parvizi, MD

Introduction: Anemia defined by the World Health Organization (WHO)1: Hemoglobin (Hb) <12 g/dl in women Hemoglobin (Hb) <13 g/dl in men The incidence of anemia in the U.S. age>70 is approximately 13%2. Literature shows: Mild degrees of anemia or polycythemia increased risk of 30-day mortality and cardiac events in older male veterans undergoing non-cardiac surgeries3. Multicenter Cohort study found preoperative anemia to be independently associated with adverse outcomes (death, stroke, or acute kidney injury) after cardiac surgery4. Preoperative anemia may have independent harmful effects due to limited patient physiologic reserve and added stress of surgery. 1. WHO. Technical Report Series No. 405, Geneva, Switzerland: WHO.1968. 2. Penninx et al. Journal of Gerontology. 2006. Vol. 61A. 474-479. 3. Wu et al. JAMA. 2007; 297: 2481-2488. 4. Karkouti et al. Circulation 2008;117;478-484.

Introduction (cont’d): Limited information is available on the impact of preoperative anemia in the elderly population following Total Joint Arthroplasty (TJA). Total joint replacements are increasing steadily each year to an estimated 3.48 million primary knee and 572,000 primary hip replacements by the year 2030. Epidemiologic implications are significant. Objective: Examine the association between preoperative hemoglobin levels and cardiovascular complications in patients undergoing total hip and knee replacements.

Methods: Following IRB approval of this retrospective study the sample (n=3954) consisted of all patients who underwent primary hip and knee arthroplasty during the years 2004 and 2005.   Patients were followed postoperatively during their hospitalization and were observed for complications. The past medical history of all patients was extracted from the preoperative evaluation office records and linked to the database containing patient information on complications.

Analysis All statistical analysis was conducted with use of SPSS software (version 11.0, Chicago, Illinois). Bivariate analyses were conducted on the three comparison groups categorized by preoperative hemoglobin values: 1. Less than 12 g/dl (anemia group) 2. 12-14 g/dl (normal reference group) 3. Greater than 14 g/dl (above normal group) Primary outcomes measured were the occurrence of any postoperative cardiovascular complications: Angina, arrhythmias, bradycardia, asystole, CHF, myocardial Infarctions, compartment syndrome, DVT’s, hypertension, hypotension, hypovolemic shock, and vascular injuries  Multivariate analyses controlled for potential confounders including: Age, BMI, race, gender, O.R. time, joint type (hips vs. knees), number of joints (unilateral vs. bilateral), DM, HTN, cardiac history (CAD, arrhythmia, CHF, valvular disorder), PVD, DVT, and previous placement of Greenfield filter.

Results: Table 1-Patient Demographics (n=3954)

Results: Table 2: Bivariate analysis of cardiovascular complications among groups (Total Sample Size=3954) Complications Hgb:<12 (n=742) Hgb:12-14 (n=1914) Hgb:>14 (n=1298) P value Cardiovascular (n=116) 41 (5.5%) 47 (2.5%) 28 (2.2%) P<0.05 Cardiac complication include: Angina, Tachycardia (SVT’s), Arrhythmias (A-fib), bradycardia, Asystole, CHF, and Myocardial Infarction. Vascular complications include: Compartment syndrome, DVT’s, Hypertension, Hypotension, Hypovolemic shock, and Vascular injury.

Results: Table 3: Logistic Regression Model for Cardiovascular Complications

Results: Table 4: Logistic Regression Model Summary Hemoglobin Beta S.E. P value Odds Ratio Hgb<12 0.575 0.219 0.022 1.778 Hgb 12-14 Reference Hgb> 14 0.024 0.274 0.931 1.024

Discussion: Ø  In this analysis, 742 patients had preoperative anemia, 1914 patients with hemoglobin levels in the reference range, and 1298 patients in the above normal group (Table 1). Ø   Average age of patients were 65.9 (Hgb<12), 65.5 (reference group), and 60.7 years (Hgb>14).   Ø  The anemia group had longer average length of surgery (128.3 minutes), compared to the reference and above normal groups (114.3 and 116.1 minutes, respectively). Ø  A higher percentage of patients with preoperative anemia had a history of CAD (16.8%), CHF (3.6%), arrhythmias (7%), and valvular disorders (11%). Ø Increased occurrence of comorbid hypertension (59.6%), diabetes (3.6%), peripheral vascular disease (1.7%), and DVT’s (3.6%) were also noted in this group. Ø Bivariate analyses indicated that patients with preoperative anemia have greater cardiovascular complications (Table 2). Ø  Due to significant differences in potential confounders between the three groups’ bivariate analyses, they were controlled for in logistic regression models (Table 3). Ø  Logistic regression model showed that patients with preoperative anemia (Hgb<12) have statistically significant risk of cardiovascular complications (Odds Ratio=1.778, p<0.05).

Conclusion: Ø   In this retrospective analysis, anemic patients (those identified with lower preoperative hemoglobin values) have an increased risk of cardiovascular complications.   Ø  Preoperative hemoglobin levels may be predictive of postoperative cardiovascular complications. Ø  These patients may benefit from more than just reversal of anemia preoperatively, rather increased surveillance for postoperative complications.

Limitations and Implications: Limitations of our study include: Small sample size relative to other published studies (JAMA). Retrospective analyses may result in omission of information regarding co-morbidities experienced by patients. There is the potential for selection bias because highest risk patients may not qualify for TJA. Information of intraoperative transfusion was not in the database and was not considered in the analysis. Implications: Patients identified to be at higher risk of cardiovascular risk may benefit from additional surveillance postoperatively.