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27 (); 17-22
doi:
10.1016/j.jor.2021.08.008

Preoperative risk factors for postoperative pneumonia following primary Total Hip and Knee Arthroplasty

, , ,
Department of Orthopaedic Surgery, University of Illinois, 835 S. Wolcott Avenue, Chicago, IL, 60612, United States

∗Corresponding author: Michael Foy. mfoy3@uic.edu

Received: , Accepted: ,
Disclaimer:
This article was originally published by Reed Elsevier India Pvt. Ltd. and was migrated to Scientific Scholar after the change of Publisher.

Abstract

Abstract

The purpose of this study is to evaluate risk factors for pneumonia following THA and TKA.

Patients were identified from the American College of Surgeons National Quality Improvement Database (NSQIP) who experienced postoperative pneumonia after undergoing primary THA and TKA.

Many characteristics including old age, anemia, diabetes, cardiac comorbidities, dialysis, and smoking were independent risk factors for postoperative pneumonia after THA or TKA.

This analysis offers new evidence on risk factors associated with the development of pneumonia after THA and TKA. These risk factors can help guide clinicians in preventing postoperative pneumonia after THA and TKA.

Keywords

Arthroplasty
Risk factors
Pneumonia
1

1 Introduction

Pneumonia is the third most common post-operative complication following surgical procedures, resulting in early re-admissions, a lengthening of the length of stay (LOS) by 7–9 days and a high burden of morbidity and mortality.1 Post-operative pneumonia is also associated with more frequent discharge to post-acute care and higher rates of 30-day mortality.2,3 It is one of the major causes of readmission and death after surgery, conferring a 5.2-fold increase in the risk of mortality after arthroplasty.4–6 The cost burden is hefty, as well – increased medical costs range from $12,000 to $40,000, with an estimated national benchmark of $46,600 per case of post-operative pneumonia and a financial burden of $10.5 million per year.7–9

The incidence of pneumonia in different surgical procedures vary, with studies showing 17.5% of patients developing pneumonia after undergoing elective thoracic, upper abdominal and lower abdominal surgeries.10 Orthopedic surgical procedures have reported a postoperative pneumonia incidence ranging from 0.45% in cervical decompression, 4% in knee amputations, to as high as 14.4% in total knee arthroplasties (TKA).11,12 For orthopedic surgeries, postoperative pneumonia has been significantly associated with several factors such as lower body mass index (BMI), blood transfusion, greater age, dependent functional status, chronic obstructive pulmonary disease, greater operative duration, steroid use, and insulin and non-insulin-dependent diabetes mellitus.13–15 Among these, poor lung function/COPD and older age have most commonly and consistently been associated with postoperative pneumonia in orthopedic and spinal surgeries. Despite these data, the number of studies analyzing postoperative pneumonia after Total Hip Arthroplasty (THA) and Total Knee Arthroplasty (TKA) procedures is limited.

Total Hip Arthroplasty (THA) and Total Knee Arthroplasty (TKA) procedures have been increasing worldwide and are predicted to be as high as 439,097 and 1,219,362 respectively by 2035 according to a 2015 study conducted by Culliford et al.16 Given the increasing numbers of THA and TKA, and the demonstrated high burden of pneumonia following these procedures, it is instrumental to better characterize the risk factors associated with postoperative pneumonia. Mitigating the risk factors has the potential benefit to improve patient outcomes and patient satisfaction, as well as make a contribution to the overall quality and cost of care.

2

2 Material and methods

2.1

2.1 Data collection

The American College of Surgery National Quality Improvement Database (NSQIP) is a database of clinical information compiled from more than 500 participating hospitals within America. The NSQIP includes information on various procedures and variables including patient demographics, preoperative risk factors, intraoperative variables, and 30-day postoperative outcomes.

This study used Current Procedural Terminology (CPT) codes to detect patients from the NSQIP database undergoing THA or TKA from 2010 to 2017. Specifically, CPT code 27130 was used to identify patients for THA and code 27144 was used for TKA. The NSQIP database provided a list of patients who received primary THA or TKA who experienced postoperative pneumonia as decided by their care team, and these patients were selected for further analysis.

Pneumonia was defined as meeting clinical symptoms, indicative laboratory values, and diagnostic imaging within 30 days of the procedure.

Patients who contracted pneumonia following THA or TKA were included and assessed for independent association with the following preoperative and perioperative characteristics were included and evaluated for independent association with the following pre and perioperative components: age, Body Mass Index, procedure time, sex, race, current dialysis, shortness of breath (dyspnea) with moderate exertion, shortness of breath (dyspnea) at rest, admission quarter, cardiac conditions, pulmonary conditions, a chronic condition requiring steroids or immunosuppressants, diabetes mellitus with oral medications or insulin, cigarette smoking status within the last year, preoperative transfusion of red blood cells (RBCs) within 72 h before the procedure, anemia, bleeding disorders, less than 150,000 platelets, and perioperative (within 72 h of the start of the procedure) transfusion of RBCs. Table 1 shows the stratification for age, Body Mass Index, admission quarter, and procedure time.

Table 1 The stratification for Age, BMI, Admission quarter, and Operative time for association with pneumonia following THA and TKA.
Total Knee Arthroplasty Total Hip Arthroplasty
Risk Factor Ranges Risk Factor Ranges
Age 18-60,60–67,67-73, or 73+ Age 18-57,57–65,65-72, or 72+
BMI <18.5,18.5-24.9,24.9-29.9, or 29.9+ BMI <18.5,18.5-24.9,24.9-29.9, or 29.9+
Admission Quarter 1,2,3, or 4 Admission Quarter 1,2,3, or 4
Operative Time (minutes) <70, 70–86,86-107, or 107+ Operative Time (minutes) <68, 68–86, 86–110, or 110+

Based on criteria from the American Heart Association, preoperative cardiac conditions included a history of chronic heart failure, myocardial infarction, angina, hypertension requiring medication, percutaneous intervention including stent placement, or a previous cardiac surgery. pulmonary conditions included ventilator dependency and history of severe Chronic Obstructive Pulmonary Disease. Bleeding disorders included any condition that placed the patient at risk for increased bleeding such as deficiency of vitamin K, having less than 150,00 platelets, hereditary conditions that reduce the ability of the blood to clot, and chronic anticoagulation therapy that was not stopped prior to the procedure. Anemia was categorized as hematocrits that were less than 36% in females and 39% in males. Body Mass Index (BMI) was stratified into four categories: underweight (BMI <18.5), normal (18.5< BMI <25), overweight (25.0< BMI <30), and obese (BMI >30 kg/m2).10

2.2

2.2 Statistical analysis

A multivariate regression model was used to determine any independent association pneumonia and pre-/perioperative risk factors. Odds ratios (OR) and 95% confidence intervals (CI) were reported to measure the association between pneumonia and risk factors. All analyses were conducted in SAS studio version 3.82. Statistical significance was set at p < 0.05.

3

3 Results

3.1

3.1 Total Hip Arthroplasty

119,096 patients who received primary Total Hip Arthroplasty were identified that had data points for all of the components of interest. Within this group, 395 (0.3%) encountered pneumonia. The multivariate analysis found the following risk factors to be independently associated with pneumonia after primary Total Hip Arthroplasty: anemia, perioperative transfusion, age above 65, diabetes, dyspnea with moderate exertion or at rest, cardiac comorbidities, dialysis, steroid or immunosuppressant use, pulmonary comorbidities, and smoking within the last year. Table 2 contains the full results.

Table 2 Multivariate analysis of preoperative and perioperative risk factors for pneumonia following primary THA.
Condition Odds Ratio 95% CI P-value
Bleeding disorder 1.28 0.80-2.07 0.305
Preoperative Transfusion 0.59 0.08-4.38 0.606
Anemia 1.28 1.16-1.88 0.001
Platelet <150 k 1.04 0.69-1.57 0.846
Operative time 68–86 min 1.04 0.79-1.38 0.780
Operative time 86–110 min 1.01 0.76-1.34 0.937
Operative time >110 min 1.04 0.78-1.38 0.809
Admission Quarter 2 0.769 0.57-1.03 0.076
Admission Quarter 3 0.840 0.64-1.11 0.219
Admission Quarter 4 1.02 0.78-1.33 0.901
Perioperative transfusion 2.43 1.87-3.15 < 0.001
Age 57-65 1.30 0.91-1.87 0.151
Age 65–72 1.76 1.23-2.52 0.002
Age 72+ 3.14 2.22-4.42 < 0.001
Diabetes 1.35 1.04-1.76 0.023
Dyspnea with Moderate Exertion 1.40 1.02-1.94 0.040
Dyspnea at Rest 2.46 1.11-5.47 0.027
Cardiac Comorbidities 1.29 1.02-1.64 0.034
Dialysis 3.16 1.25-7.95 0.015
Steroid/Immunosuppressant use 1.98 1.40-2.80 < 0.001
BMI <18.5 1.08 0.46-2.49 0.866
BMI 24.9–29.9 0.804 0.61-1.06 0.122
BMI 29.9+ 0.885 0.68-1.16 0.370
Male Sex 1.02 0.83-1.26 0.823
Pulmonary Comorbidities 4.13 3.14-5.42 < 0.001
Smoking Status 1.96 1.50-2.56 < 0.001
3.2

3.2 Total knee arthroplasty

189,327 patients who received primary Total Knee Arthroplasty were identified that had data for all the components of interest. Within this group, 618 (0.3%) encountered pneumonia. The multivariate analysis found the following risk factors to be independently associated with pneumonia following primary Total Knee Arthroplasty anemia, perioperative transfusion, age greater than 73, dyspnea with moderate exertion or at rest, cardiac comorbidities, dialysis, steroid or immunosuppressant use, male sex, pulmonary comorbidities and smoking within the last year.Table 3 contains the full results.

Table 3 Multivariate analysis of preoperative and perioperative risk factors for pneumonia primary TKA.
Condition Odds Ratio 95% CI P-value
Bleeding disorder 0.80 0.48-1.30 0.359
Preoperative Transfusion 0.00 0.00–0.00 0.951
Anemia 1.88 1.56-2.28 < 0.001
Platelet <150 k 1.03 0.74-1.43 0.863
Operative time 70–86 min 0.83 0.67-1.04 0.106
Operative time 86–107 min 0.92 0.74-1.13 0.430
Operative time >107 min 0.87 0.70-1.09 0.229
Admission Quarter 2 0.85 0.67-1.06 0.154
Admission Quarter 3 1.05 0.85-1.30 0.642
Admission Quarter 4 0.88 0.70-1.10 0.259
Perioperative transfusion 2.12 1.64-2.73 < 0.001
Age 60-67 1.03 0.80-1.33 0.832
Age 67-73 1.23 0.95-1.60 0.122
Age 73+ 2.04 1.60-2.61 < 0.001
Diabetes 1.21 1.00–1.47 0.051
Dyspnea with Moderate Exertion 1.79 1.39-2.29 < 0.001
Dyspnea at rest 3.58 1.73-7.42 0.001
Cardiac Comorbidities 1.31 1.07-1.59 0.008
Dialysis 2.93 1.19-7.22 0.020
Steroid/Immunosuppressant use 2.29 1.72-3.03 < 0.001
BMI <18.5 0.61 0.08-4.40 0.620
BMI 24.9–29.9 1.01 0.76-1.34 0.967
BMI 29.9+ 0.95 0.72-1.25 0.700
Male Sex 1.23 1.04-1.45 0.013
Pulmonary Comorbidities 2.76 2.15-3.55 < 0.001
Smoking status 1.62 1.26-2.10 < 0.001
4

4 Discussion

Understanding the variety of preoperative risk factors associated with the incidence of pneumonia following total hip or total knee arthroplasty are vital in efforts to prevent and reduce pneumonia occurrence. With the growing numbers of total hip and knee arthroplasty operations across the world, this current study contributes to a growing body of literature evaluating potential risk factors for postoperative pneumonia following total joint arthroplasty. Targeted measures that mitigate the identified risk factors may help reduce the overall incidence of postoperative pneumonia following THA and TKA.

Notably, in this analysis of NSQIP data, 0.3% of patients (N = 119,096 for THA and 189,327 for TKA) undergoing TKA and THA developed postoperative pneumonia, which is on lower than the previously reported prevalence of 0.45–14% seen in orthopedic surgeries. The wide range in these rates could be contributions of the small number (N = 111) and narrower age range of participants (43–83 years), as exhibited by Song et al.14 Given the small number of currently available epidemiological studies on postoperative pneumonia in orthopedic surgeries, our paper provides an important perspective on this growing body of literature.

In both total hip and total knee arthroplasty patients, the findings of the present study showed preoperative comorbidities such as anemia, perioperative transfusion, age greater than 73, dyspnea with moderate exertion or at rest, cardiac comorbidities, dialysis, steroid or immunosuppressant use, pulmonary comorbidities and smoking within the last year as independent risk factors for postoperative pneumonia. These findings are consistent with several studies showing blood transfusion, greater age, pulmonary comorbidities such as COPD, steroid use and diabetes.3–5

Age has long been associated with increased community-acquired pneumonia and adverse post-operative complications.17–21 This is also reflected in orthopedic surgery.11,15 However, several authors have argued that it is age-related comorbidities and not age that is a risk factor.22–25 In our analysis, both THA and TKA had age above 73 characterized as a risk factor, and specific to THA, age above 65 was an additional risk factor for postoperative pneumonia. This distinction is meaningful since about 16% of the U.S. population (over 52 million people) was 65 years old or older in 2018, according to annual mid-year population estimates from the U.S. Census Bureau.26 With increasing life expectancy and retirement age, TKA and THA after the age of 65 may be commonly needed procedures and it can be reassuring for both physicians suggesting these procedures and patients to understand this difference in risk under and over the age of 73.

In the current study, male patients were associated with an increased risk for pneumonia following TKA. Many epidemiological studies have historically reported an overall greater incidence of pneumonia occurring in males, including during the 2020 SARS-Cov-2 pandemic.27–31 The results of this study are consistent with the current literature and suggest that males are at a greater risk for not only nosocomial and community-acquired pneumonia, but also pneumonia following total joint arthroplasty of the knee. While this is an unmodifiable risk factor, it may be something important to consider, especially when greater age and other comorbidities act as additional risk factors.

Preoperative steroid or immunosuppressant use was reported as an independent risk factor for postoperative pneumonia following both THA and TKA. There is a well-documented history of reported increased rates of infection following pre-operative steroid use, including a 2- to 3-fold increased risk of infections and an almost 4-fold higher risk of death.32,33 Studies have suggested this is dependent on dosage of steroids and the timing when steroid injections have been administered.34,35 However, steroids have also been reported to decrease postoperative pain without increasing the length of stay significantly.36 Clinical recommendations include decreasing dosage of steroids to under 5 mg/day prior to arthroplasty.37 If this is not possible, current daily dose of glucocorticoids should be given on the day of surgery if taking <15 mg instead of giving perioperative supraphysiologic doses referred to as “stress doses”.38 Surgeons should take note of patients who have received corticosteroid injections within 3 months before total joint arthroplasty and consider them at a higher risk for infection.39

Pulmonary comorbidities, such as COPD have long been associated with increased rates of community-acquired, nosocomial and post-operative pneumonia.40 The result of this study was in agreement with the existing body of literature for both THA and TKA. A potential mechanism suggests that proinflammatory mediators produced during this process combined with the respiratory muscle dysfunction caused by anesthesia and surgery can lead to atelectasis in the basal lung segments, thus compromising gas exchange and further reducing lung function.41 This atelectasis area acts as a nidus for infection and post-operative pneumonia. Medical interventions that are effective in reducing the risk of exacerbations of COPD, such as salmeterol and fluticasone, have the disadvantage of increasing risk of pneumonia.42 This increased risk due to use of steroids was also seen in our analysis. The role of corticosteroids in management of patients with COPD with pneumonia is not well-defined.43 As a result of all of these factors, close consultation with pulmonologists is necessary, and delaying or cancelling the TKA or THA surgery until COPD is moderately controlled can be a difficult choice that should be discussed with the patients.44 Changing the anesthetic to a local anesthesia may also be considered. Early distinguishing of exacerbations of COPD from pneumonia is important for management purposes. Given the multiple factors, prophylactic antibiotics, especially those that target Staphylococcus aureus and Gram-negative bacilli should be considered peri and post-operatively.45,46

Cardiac comorbidities were also identified as a risk factor for post-operative pneumonia after both THA and TKA. Patients with adverse cardiac conditions are more likely to develop deep surgical site infection, pneumonia, pulmonary emboli, chronic and acute renal failure amongst a host of other problems.47 Hypertension and congestive heart failure have been linked as independent cardiac risk factors for post-operative pneumonia.48,49 However, there is limited literature evaluating role of cardiac comorbidities as risk factors post-arthroplasty. Hypertension could be linked to potential cerebral and vascular diseases which has been shown to increase aspiration, leading to postoperative pneumonia. Clinical management should consider empiric antibiotic regimen that includes at least a broad-spectrum antibiotic targeting non-fermenting Gram-negative bacilli, regardless of the type of pneumonia, and targeting S. aureus in ventilator-associated patients.

Dialysis was identified as a risk factor for post-operative pneumonia after both THA and TKA. There are not many examples of dialysis as a pre-operative risk factor in the literature. Chen et al. identified 6.7% risk of developing post-operative pneumonia within 90 days, but had a small sample size (N = 15).50 Kawanishi et al. identified hemodialysis as an independent risk factor for developing postoperative pneumonia, especially aspiration pneumonia.51 A confounding factor may be malnutrition, since patients on hemodialysis are more likely to be poorly nourished and malnutrition is regarded as a risk factor for aspiration pneumonia due to a weaker immune system. Interestingly, our study did not identify BMI as a risk factor for post-operative pneumonia. Given the increasing rate of patients on dialysis (726,000 and growing), our study adds a cautionary risk factor when considering arthroplasty.52

Anemia was identified as a risk factor for post-operative pneumonia after both THA and TKA. Anemia has been reported as a significant risk factor for postoperative complications, including pneumonia, increased hospital stays and increased mortality, while some have debated anemia's impact as an independent risk factor due to its link with other comorbidities and classified it as a confounding factor.53–55 Preoperative anemia reduces hemoglobin's lower oxygen-carrying capacity, which may predispose to impaired wound healing, cardiac perfusion and pulmonary function. Furthermore, anemia is a predictor for pre-operative and peri-operative transfusion, and the latter is classified as a risk factor for pneumonia post-THA and TKA in literature and in our analysis.56–59 Thus, anemic patients should consider nutritional interventions with supplemental iron, vitamin B12, folic acid or the use of erythropoietin prior to surgery in order to increase hemoglobin levels as perioperative RBC transfusions were shown to be risk factors for postoperative pneumonia.60,61 Implementation of hemoglobin monitoring and anemia management prior to elective orthopedic surgeries can reduce need for peri-operative blood transfusion, mitigate risk of pneumonia and improve patient outcomes.

The association between blood transfusion and complications following surgical procedures has been shown in a number of studies, including in hip fracture repairs and primary TKA and THA's.62 Carson et al. found a 52% greater risk of pneumonia following blood transfusions in a retrospective cohort of 9598 consecutive hip fractures.63 Hart et al. showed that perioperative blood transfusions are significantly associated with post-operative pneumonia, but not an increased 30-day mortality in THA, but was associated with an increased 30-day mortality post- TKA's.59 The current study supports the precaution of using a restrictive transfusion policy for total joint arthroplasties since several high-quality randomized control trials have demonstrated the efficacy and safety.63–65

Smoking was identified as a risk factor for post-operative pneumonia after both THA and TKA. Several studies have indicated that smoking increases risk of post-operative infections, including pneumonia and result in higher postoperative morbidities, a longer length of stay and higher morbidity.66 Lugg et al. reported a 11-fold increase in the frequency of postoperative pulmonary complications, including pneumonia amongst current smokers.67 While smoking cessation reduced the incidence of pneumonia and re-admissions, there is no definitive timing when cessation is most effective. Patients should be consulted to cease smoking at least 4 weeks prior to surgery to observe a marked reduction in incidence of pneumonia.68 Since smoking contributes to pulmonary comorbidities and both were identified as risk factors for post-operative pneumonia post arthroplasty, a multivariate analysis needs to be done to tease out the confounding variables, if any.

Dyspnea at rest and on exertion were also associated with increased risk for postoperative pneumonia following THA and TKA. Dyspnea has been reported as a significant risk factor for postoperative pneumonia in several studies.13,69 Patients with dyspnea or cough should be carefully evaluated with a thorough history and physical and undergo pulmonary function tests. While the American College of Physicians does not recommend routine pre-operative chest x ray and pulmonary function tests for all patients, the value of these tests is higher for patients who have dyspnea and are at a higher risk for post-operative pneumonia.70

Diabetes has been considered a common risk factor for post-operative pneumonia in literature, including in hip fractures and arthroplasty.1,13,18,71–74 Our study confirms this link between diabetes and postoperative pneumonia post-THA. Blood sugar monitoring and control before the arthroplasty is recommended for clinical practice. Those with uncontrolled diabetes have risk of developing dehydration from polyuria or hyperosmolar coma.75

Interestingly, the present study does not report overweight or obese status, as reported by higher BMI, as a risk factor for postoperative pneumonia following THA or TKA. Operative duration has been reported in literature as a risk factor for post-operative pneumonia.1 However, this study does not identify it as a risk factor post THA or TKA.

Given the high morbidity of postoperative pneumonia, efforts to prevent postoperative pneumonia should be actively pursued for high-risk patients. Kazaure et al. conducted a successful intervention program that reduced the rate of postoperative pneumonia by 43.6% in a single surgical ward over a 5-year period (from case rates of 0.78% pre-intervention to 0.44% post-intervention)9. This program identified interprofessional collaboration and small process measures that can overall improve the quality of care. The program consisted of quarterly program improvement, education of physicians and ward staff, coughing and deep-breathing exercises and a standardized postoperative electronic order set consisting of incentive spirometer, chlorhexidine oral hygiene, ambulation and pain control, head-of-bed elevation and sitting up for all meals76. Cassidy et al. conducted a similar intervention process (COUGH Program) with incentive spirometry, coughing and deep breathing, oral care, patient and family education, getting out of bed and head-of-bed elevation showing a 38% reduction in the incidence of pneumonia (from case rates of 2.6% pre-intervention to 1.6% post-intervention)77. It must be noted that the COUGH Program has had difficulties in sustaining its initial success, and so continuous training and improvement may be necessary to observe long-term changes78.

Although it might be financially unfeasible to apply these interventions for all patients, identifying risk factors allows us to stratify patients who would benefit most from such intervention programs. In addition, it enables surgeons to identify which patients are at a higher risk and need prophylactic antibiotics.79 Using a national average of $46,400 in attributable health costs of postoperative pneumonia, Kazaure et al. predict a national cost-savings of $280 million at ACS-NSQIP hospitals if a similar reduction rate was achieved at each site.9 Given the increased rate of excess deaths due to pneumonia associated with the SARS-CoV-2 (Covid-19) pandemic, and the potential for co-infection with SARS-CoV-2 in patients with existing pneumonia, it is crucial to reduce the rates of post-operative pneumonia.80–83

Limitation of this study include those inherent to all retrospective observational analyses. Selection bias may exist in this study. In addition, it could be possible that patients had pneumonia preoperatively. Additional pertinent details, such as timing of pneumonia post-operatively is missing. Lack of temporal information on pneumonia prevents us from understanding which risk factors can have a higher burden of morbidity and mortality. There is no information on case-specific potential preventative interventions, such as posture, bed head settings, and comorbidities collected by the database. As discussed earlier, these could have acted as mitigating factors and reduced cases of pneumonia, thus leading to the data underestimating the potential impact of a risk factor. In addition, the study does not enable a meaningful distinction between ventilator associated and non-ventilator associated pneumonias, or nosocomial and community-acquired pneumonia which have different levels of antibiotic resistance and difficulties in clinical management.

5

5 Conclusion

Patients were found to have a statistically significant independent risk of postoperative pneumonia following primary THA and TKA. Perioperative transfusion of packed red blood cells, increasing age, male sex, diabetes, preoperative steroid use, and hematologic disorders can be vital in preventing lung infections. Future randomized controlled studies utilizing the risk factors discovered in this study should be performed to determine if prophylactic interventions can reduce the incidence of postoperative pneumonia following major joint arthroplasty.

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