Objectives: Patients who are being considered for renal transplant must undergo thorough preoperative pulmonary evaluation to determine risk of post­operative pulmonary complications. The aim of this study was to determine the relation between the preoperative pulmonary risk factor score and pulmonary complications in patients undergoing renal transplant.

Materials and Methods: Medical records of patients who underwent renal transplant at our institution between 2004 and 2015 were retrospectively reviewed. Patient demographics, smoking history, comorbidities, and preoperative pulmonary risk factors (age, oxygen saturation, hemoglobin level, type of incision, duration of surgery, history of lower respiratory tract infection 1 month before surgery, urgency of surgery), and type of pulmonary com­plications within 1 month after transplant were recorded.

Results: Our study included 131 patients (94 male patients; mean age of 38.25 ± 12.96 y). Of total patients, 21(16%) developed complications during the first month after transplant, with 10 of the 21 (7.6% overall) developing pulmonary complications. These complications were pleural effusion (2 patients), pneumonia (3 patients), respiratory failure (2 patients), and pulmonary embolism (1 patient). There were no deaths directly attributed to the pulmonary com­plications. A significant correlation was observed between the preoperative pulmonary risk factor score and postoperative pulmonary complications in renal transplant recipients (P = .003). A positive correlation between the preoperative pulmonary scores and postoperative pulmonary complications existed among life-long nonsmokers (r = 0.371; P = .003).

Conclusions: Renal transplant is an established modality in treatment of chronic renal failure. Prevention of pulmonary complications is essential for successful outcomes following transplant. Health care professionals involved with renal transplant and transplant centers should be aware of preoperative pulmonary risk factors. Patients should be observed so that these risk factors can be reduced before planned transplant. Moreover, we also suggest that smoking history should be considered as a preoperative pulmonary risk factor as it was found to be a factor leading to postoperative pulmonary complications in our study.

Key words : Pneumonia, Postoperative complications, Renal transplantation

Introduction

Patients with chronic renal failure due to various mechanisms are prone to significant pulmonary comorbidities. The treatment of chronic renal failure is kidney transplant.1 Therefore, patients who are selected for transplant must have a thorough preo­perative pulmonary evaluation to assess pulmonary status and to determine risk of postoperative pulmonary complications (POPCs).

Pulmonary complications of patients with chronic renal failure mainly include pulmonary edema and pleural effusions.² Other less common complications include pulmonary hypertension, pulmonary fibrosis, and pulmonary calcifications. It is important to identify these patients and to make sure they are treated more aggressively, as the rate of nonthoracic surgery patients with POPCs ranges from 2% to 19%.³

The field of preoperative pulmonary evaluation is increasingly driven by evidence-based medicine rather than expert opinion. With effects of pulmonary complications after surgery becoming increasingly apparent, estimation of risks should be a standard element of all preoperative medical evaluations. Patients undergoing renal transplant should routinely undergo general health assessment before surgery. Certain modifiable risk factors should be assessed and addressed to ensure minimal postoperative complications. The aim of this study was to determine the relation between the preoperative pulmonary risk factor score (preOPRS) and POPC in patients undergoing renal transplant.

Materials and Methods

Patient population
Medical records of patients who underwent renal transplant at our institution between 2004 and 2015 were retrospectively reviewed. Patient demographics, smoking history, and comorbidities were recorded. The study was approved by the institutional review board and the ethical committee of the university. All of the protocols conformed to the ethical guidelines of the 1975 Helsinki Declaration. Written informed consent was obtained from all patients.

Assessment of postoperative pulmonary risk
The Assess Respiratory Risk in Surgical Patients in Catalonia (ARISCAT) risk index was used to predict the overall incidence of POPCs (of any severity), by assigning a weighted point score to 7 independent risk factors. These risk factors are advanced age, low oxygen saturation, preoperative low hemoglobin level, type of incision, duration of surgery, history of lower respiratory tract infection 1 month before surgery, and need for emergency surgery.⁴ The ARISCAT risk index is shown in Table 1.

Definitions of postoperative pulmonary compli­cations
Types of pulmonary complications within 1 month after transplant were also recorded. Lower respiratory tract infection was defined as presence of cough with purulent sputum production, temperature higher than 39°C, and leukocytosis with response to appropriate antimicrobial therapy. Pneumonia was defined as including these same symptoms plus evidence of new lung infiltrates at radiography. Although microbiologic studies were ordered, a positive result was not mandatory to confirm the diagnosis.

Pulmonary embolism was suspected based on patient clinical presentation and laboratory data (eg, D-dimer, chest radiograph, arterial blood-gas analyses) and objectively confirmed using computed tomography pulmonary angiography. Deep venous thrombosis was diagnosed using bilateral deep venous compression and Doppler ultrasonography.

Statistical analyses
Data were analyzed using commercially available software (Statistical Product and Services Solutions, version 20.0, SPSS Inc., Chicago, IL, USA). Kolmogorov-Smirnov and Shapiro-Wilks tests and histograms were used as tests of normality. Continuous data are presented as means ± standard deviation. Chi-squared test was used to compare the qualitative variables. For investigation of associations between nonnormally distributed or ordinal variables, correlation coefficients and their significance were calculated with the Spearman test. All P values are 2-tailed, and P values < .05 were considered statistically significant.

Results

Our study included 131 patients (94 male patients; mean age of 38.25 ± 12.96 y). Patient demographics are shown in Table 2.

Of total patients, 21 (16%) developed com­plications during the first month after transplant. Pulmonary complications were observed in 10 of the 21 patients (7.6% overall) during this period. These complications were pleural effusion (2 patients), pneumonia (3 patients), respiratory failure (2 patients), and pulmonary embolism (1 patient). No statistically significant associations were observed between smoking history and POPC in the first month (P = .28). There were no deaths directly attributed to the pulmonary com­plications.

Forty percent of patients had a smoking history, and 44% of these were active smokers. Thirty-five patients developed acute rejection during the study period; 51.7% of these had a smoking history. Ex-smokers had a significantly higher rate of rejection than life-long smokers (P = .035). There was no correlation between the amount and the duration of cigarettes smoked and the rejection rate (P = .36 and P = .22).

A significant correlation was observed between the preOPRS and the POPC in renal transplant recipients (P = .003). A positive correlation between the preOPRS and POPC existed among life-long nonsmokers (r = 0.371; P = .003).

Among patients older than 45 years, a positive correlation was observed between preOPRS and occurrence of POPC (r = 0.321; P = 0.034).

Discussion

Renal transplant patients, routinely undergo general health assessment before surgery. Certain modifiable risk factors should be assessed and addressed to ensure minimal POPCs.

Lower respiratory tract infection is the most common complication in kidney recipients and can be associated with high mortality. Pneumonia is observed most frequently during the first 6 months after surgery. The immunocompromised state is primarily responsible for this complication.⁵ Pneumonia was the most common pulmonary complication in the present study, but it caused no major consequences.

The incidence of pulmonary embolism in trans­plant recipients varies between 2% and 14%.⁶ It occurs possibly due to impaired fibrinolysis and a persistent hypercoagulable state.⁷ In 1 of our patients, a pulmonary embolism developed as a consequence of deep venous thrombosis.

Pleural effusions may occur after renal transplant due to heart failure, tuberculosis, and uremic state.⁸ Differentiating these effusions requires a combined clinicopathologic approach, and this differentiation is absolutely necessary for proper management. In the present study, 2 patients developed pleural effusions due to a uremic state.

The field of preoperative pulmonary evaluation is increasingly driven by evidence-based medicine rather than expert opinion. With effects of pul­monary complications following surgery becoming increasingly apparent, estimation of their risks should be a standard element during all preoperative medical evaluations. We aimed to assess and estimate POPCs by scoring the patients according to the ARISCAT risk index. This tool is useful to stratify risk when advising patients before surgery and, in some cases, to identify patients most likely to benefit from risk-reduction interventions.

The influence of age as an independent predictor of POPCs has been questioned. A systematic review prepared for the American College of Physicians estimated the effect of age on POPC among studies that used multivariable analysis to adjust for age-related comorbidities.⁹ This review made the novel observation that age > 50 years was an important independent predictor of risk. The ARISCAT risk index has a similar classification of age as an independent risk factor (Table 1), and we scored the patients accordingly. Patients older than 80 years old had the highest risk score.

Pulmonary abnormalities seen in uremia such as pulmonary edema, pleural effusions, pulmonary calcification, and respiratory muscle myopathy¹⁰ lead to diminished pulmonary function and may alter respiration. Thus, a reduction in vital capacity, decreased expiratory flows, decreased respiratory muscle strength, and hypoxemia may occur.¹¹ Preoperative oxygen saturation levels gain an importance to estimate POPCs and stays as a risk factor in the ARISCAT risk index.

Data regarding the risk of POPCs among adults with recent upper respiratory infections are limited. Most data include children who are undergoing surgery. It has been shown that children with active upper respiratory infection have more minor postoperative respiratory events such as oxygen desaturation, but no apparent increase in major morbidity or long-term sequelae.¹² Whether the same applies to surgical outcomes in adults is unknown. However, it would seem wise to defer elective surgery in this setting. In the present study, only 1 patient had a recent upper respiratory infection.

Abnormal preoperative hemoglobin concentrations are associated with increased perioperative morbidity and mortality in patients undergoing noncardiac surgery.¹³ Several large-scale retrospective studies have reported that preoperative anemia is associated with an increased risk of 30-day postoperative mortality.^13-15 These results indicate that preoperative anemia is a risk factor for poor perioperative outcome. Moreover, anemia with chronic kidney disease, if severe and left untreated, can result in increased risk of morbidity and mortality. Preoperative assessment and correction of hemoglobin concen­trations to normal values might reduce mortality and reduce the intensive care resource use in renal transplant recipients. In the present study, 26 patients had hemoglobin levels of less than 10 g/dL.

Surgical site is the single most important factor in predicting the overall risk of POPC; the incidence of complications is inversely related to the distance of the surgical incision from the diaphragm. Renal transplant surgeries are done with flank incision in our center; thus, the surgical incision site would never be considered as a risk factor for POPC according to the ARISCAT index. Surgical procedures lasting more than 3 to 4 hours are associated with a higher risk of pulmonary complications.^16,17 Renal transplant surgery is a lengthy procedure, adding a high score for POPCs before the procedure starts.

In the present study, we found that smoking history correlated with higher rate of rejection in renal transplant patients. Moreover, a positive correlation was observed between preOPRS and POPC among life-long nonsmokers. According to the published data, current cigarette smokers have an increased risk for POPC. Smoking cessation of at least 4 weeks before surgery reduces the risk of postoperative complications, and longer periods of smoking cessation may be even more effective.¹⁸ In a 2014 meta-analysis, preoperative smoking was associated with an increased risk of POPC.¹⁹ Smokers with a greater than 20 pack-year smoking history have a higher incidence of POPC than those with a lesser pack-year history.²⁰ We suggest that including smoking history to the ARISCAT risk index may be essential to estimate POPCs before surgery.

The present study has some limitations. First, it is a retrospective study. The population of the study can be increased by reviewing more data to observe better correlations between preOPRS and POPCs.

In conclusion, health care professionals should be aware of possible risk factors that should be addressed before surgery. Renal transplant centers should evaluate patients according to the risk assessment indexes to estimate any postoperative complications. The ARISCAT risk index predicts the overall incidence of POPCs and has the advantage of being simple to calculate manually at the bedside with readily available clinical information. This study is unique in that it unfurls the necessity of ARISCAT risk index in renal transplant recipients to estimate POPCs. We also underline the importance of smoking history and strongly suggest to including this in the indexing system.

References:

1. Kaplan B, Meier-Kriesche HU. Renal transplantation: A half century of success and the long road ahead. J Am Soc Nephrol. 2004;15(12):3270-3271.
   CrossRef - PubMed
2. Fairshter RD, Vaziri ND, Mirahmadi MK. Lung pathology in chronic hemodialysis patients. Int J Artif Organs. 1982;5(2):97-100.
   PubMed
3. Fisher BW, Majumdar SR, McAlister FA. Predicting pulmonary complications after nonthoracic surgery: A systematic review of blinded studies. Am J Med. 2002;112(3):219-225.
   CrossRef - PubMed
4. Canet J, Gallart L, Gomar C, et al. Prediction of postoperative pulmonary complications in a population-based surgical cohort. Anesthesiology. 2010;113(6):1338-1350.
   CrossRef - PubMed
5. Kupeli E, Ulubay G, Colak T, et al. Pulmonary complications in renal recipients after transplantation. Transplant Proc. 2011;43 (2):551-553.
   CrossRef - PubMed
6. Humar A, Johnson EM, Gillingham KJ, et al. Venous thromboembolic complications after kidney and kidney pancreas transplantation: a multivariate analysis. Transplantation. 1998;65(2):229-234.
   CrossRef - PubMed
7. Kazory A, Ducloux D. Acquired hypercoagulable state in renal transplant recipients. Thromb Haemost. 2004;91(4):646-654.
   CrossRef - PubMed
8. Ray S, Mukherjee S, Ganguly J, Abhishek K, Mitras S, Kundu S. A cross-sectional prospective study of pleural effusion among cases of chronic kidney disease. Indian J Chest Dis Allied Sci. 2013;55(4):209-213.
   PubMed
9. Smetana GW, Lawrence VA, Cornell JE; American College of Physicians. Preoperative pulmonary risk stratification for noncardiothoracic surgery: systematic review for the American College of Physicians. Ann Intern Med. 2006;144(8):581-595.
   CrossRef - PubMed
10. Prezant DJ. Effect of uremia and its treatment on pulmonary function. Lung. 1990;168(1):1-14.
    CrossRef - PubMed
11. Sidhu J, Ahuja G, Aulakh B, Narang A, Whig J, Sidhu U. Changes in pulmonary function in patients with chronic renal failure after successful renal transplantation. Scand J Urol Nephrol. 2007;41(2):155-160.
    CrossRef - PubMed
12. Tait AR, Malviya S. Anesthesia for the child with an upper respiratory tract infection: still a dilemma? Anesth Analg. 2005;100(1):59-65.
    CrossRef - PubMed
13. Wu WC, Schifftner TL, Henderson WG, et al. Preoperative hematocrit levels and postoperative outcomes in older patients undergoing noncardiac surgery. JAMA. 2007;297(22):2481-2488.
    CrossRef - PubMed
14. Saager L, Turan A, Reynolds LF, Dalton JE, Mascha EJ, Kurz A. The association between preoperative anemia and 30-day mortality and morbidity in noncardiac surgical patients. Anesth Analg. 2013;117(4):909-915.
    CrossRef - PubMed
15. Musallam KM, Tamim HM, Richards T, et al. Preoperative anaemia and postoperative outcomes in non-cardiac surgery: a retrospective cohort study. Lancet. 2011;378(9800):1396-1407.
    CrossRef - PubMed
16. Brooks-Brunn JA. Predictors of postoperative pulmonary complications following abdominal surgery. Chest. 1997;111(3):564-571.
    CrossRef - PubMed
17. McAlister FA, Khan NA, Straus SE, et al. Accuracy of the preoperative assessment in predicting pulmonary risk after nonthoracic surgery. Am J Respir Crit Care Med. 2003;167(5):741-744.
    CrossRef - PubMed
18. Wightman JA. A prospective survey of the incidence of postoperative pulmonary complications. Br J Surg. 1968;55(2):85-91
    CrossRef - PubMed
19. Grønkjær M, Eliasen M, Skov-Ettrup LS, et al. Preoperative smoking status and postoperative complications: a systematic review and meta-analysis. Ann Surg. 2014; 259(1):52-71.
    CrossRef - PubMed
20. Warner MA, Divertie MB, Tinker JH. Preoperative cessation of smoking and pulmonary complications in coronary artery bypass patients. Anesthesiology. 1984; 60(4):380-383.
    CrossRef - PubMed