Subclinical Hypothyroidism Increases the Requirement of Renal Replacement Therapy After Cardiac Surgery

Abstract

Background: Subclinical or biochemically diagnosed hypothyroidism (SCH) is defined as an elevated serum thyroid-stimulating hormone (TSH) with normal free thyroxine (FT4) levels. Thyroid hormones play a major role in the normal function of the heart and vascular physiology. Atherosclerosis, increased systemic vascular resistance, and decreased arterial compliance are common pathophysiological changes that may occur in hypothyroidism. Acute kidney injury (AKI) is one of the devastating complications after cardiac surgery. Age, diabetes mellitus (DM), preexisting renal dysfunction, hypertension, impaired left ventricular function, and severe arteriosclerosis are the major risk factors for the development of AKI. The purpose of the current study was to analyze the influence of SCH on AKI and the requirement of renal replacement therapy (RRT) after isolated coronary artery bypass graft surgery (CABG). Methods: We retrospectively reviewed the prospectively collected data of 336 adult patients who underwent isolated CABG surgery with normal renal function (baseline serum creatinine value <1.4 mg/dL) from January 2017 to January 2019. The patients were divided into two groups either having the diagnosis of SCH (Group I, N = 47) or not (Group II, N = 289). SCH was diagnosed based on preoperative serum TSH and FT4 levels. Kidney injury was interpreted, according to RIFLE classification. The effect of SCH on AKI and the need for RRT after CABG was determined using logistic regression analysis and the results were expressed as odds ratio (OR) with a 95% confidence interval (CI). A P value < .05 was considered statistically significant. Results: Subclinical hypothyroidism was diagnosed in 14% of all patients. Postoperative AKI occurred in 15 patients (31.9%) in Group I, whereas there were 42 patients (14.5%) in Group II. On logistic regression analysis, the presence of SCH was shown to be associated with an increased incidence of postoperative AKI (OR, 0.363; 95% CI, 0.181-0.727; P = .004). RRT was used in 2.97% of patients (seven patients in Group I and three patients in Group II, P < .001). The 30-day mortality was 2.1%. Conclusion: The presence of SCH seems to be associated with an increased incidence of AKI and increased requirement for RRT after cardiac surgery.

Thyroid hormones regulate both cardiovascular and renal mechanisms underlying hypertension

“…Such a discrepancy between renal supply and demand in O 2 and nutrients could predispose patients with hypoparathyroidism to the development of acute kidney injury. 75 A prolonged hypothyroid state could also provoke irreversible damage to the kidney. Population-based studies reveled the association between thyroid-stimulating hormone (increased during hypothyroidism) with higher prevalence of chronic kidney disease.…”

“…The subsequent activation of the tubule‐glomerular feedback triggers a more robust vasoconstriction of the preglomerular arterioles, exacerbating the already low blood supply. Such a discrepancy between renal supply and demand in O 2 and nutrients could predispose patients with hypoparathyroidism to the development of acute kidney injury 75 . A prolonged hypothyroid state could also provoke irreversible damage to the kidney.…”

Subclinical hypothyroidism and clinical outcomes after cardiac surgery: A systematic review and meta-analysis

“…Our study is the first meta-analysis to evaluate the association between SCH and postoperative and long-term outcomes following cardiac surgery. The primary outcome was reported by 6 of the 7 retrospective studies that we analyzed, 18 , 19 , 23 , 25 , 26 , 28 and based on our analysis, SCH patients had a greater risk of operative mortality compared to their euthyroid counterparts. Although not surgery-related, other meta-analytic studies have been conducted focusing on cardiovascular outcomes, showing that SCH is associated with increased CHD and mortality.…”

Hypothyroidism Is Correlated with Ventilator Complications and Longer Hospital Days after Coronary Artery Bypass Grafting Surgery in a Relatively Young Population: A Nationwide, Population-Based Study

“…It is also reported that impaired renal function is linked to both overt and subclinical hypothyroidism, which are associated with hypotension, increased vascular resistance, and decreased sodium reabsorption, which leads to volume contraction, reduced renal blood flow, and low glomerular filtration rate [4].…”

“…Patients with advanced coronary artery disease (CAD) require a coronary artery bypass grafting (CABG). Some single-center retrospective clinical studies on the long-term prognosis of patients with hypothyroidism who underwent CABG have revealed a higher risk of revascularization, atrial fibrillation, and all-cause mortality [5][6][7] and increased risk of renal replacement therapy [4]. The exact physiology of thyroid disease and the relationship with post-CABG prognosis remain unclear.…”