Clinical review: thyroid hormone replacement in children after cardiac surgery--is it worth a try?

Changes of serum TSH, FT3, and FT4 levels in infants received surgical correction of congenital heart disease under cardiopulmonary bypass

OBJECTIVE

This study aimed to explore the fluctuations and clinical relevance of serum thyrotropin (TSH), free triiodothyronine (FT3), and free thyroxine (FT4) levels in infants undergoing surgical correction for congenital heart disease (CHD) using cardiopulmonary bypass (CPB).

METHODS

In a retrospective design, 58 infants who underwent CHD surgical correction under CPB between January 2021 and January 2022 at our institution were incorporated. These infants were categorized into two groups: simple CHD (n = 34) and complex CHD (n = 24). TSH, FT3, and FT4 serum concentrations were assessed at four intervals: 24 h pre-surgery (T0) and 24 h (T1), 48 h (T2), and 72 h (T3) post-surgery.

RESULTS

The simple CHD group displayed a significantly reduced CPB duration compared to the complex CHD group (P < 0.001). Both groups exhibited a notable decline in serum thyroid hormone concentrations at T1 compared to T0. However, from T1 to T3, an upward trend in hormone levels was observed. By T3, though the levels in both groups had risen notably from T1, they remained significantly diminished from T0 (P < 0.01). In both the simple and complex CHD cohorts, significant fluctuations in thyroid hormone levels (TSH, FT3, FT4) were noted across the different timepoints (T0, T1, T3) (P < 0.01). While no significant disparities were found between the two groups' hormone concentrations at T0 and T1 (P > 0.05), at T2 and T3, the simple CHD group manifested higher TSH, FT3, and FT4 levels compared to the complex CHD group (P < 0.05).

CONCLUSIONS

Infants undergoing CHD surgical correction under CPB experience significant declines in TSH, FT3, and FT4 serum levels. The post-surgery thyroid hormone recovery was more pronounced in infants with simple CHD compared to those with complex CHD. As such, vigilant monitoring of thyroid hormone levels during the perioperative phase is imperative, and timely intervention measures should be employed when necessary.

Thyroid Hormones and Health-Related Quality of Life in Normal Pressure Hydrocephalus Patients before and after the Ventriculoperitoneal Shunt Surgery: A Longitudinal Study

Objective: The aim of this study was to explore the serum levels of thyroid-stimulating hormone (TSH), free thyroxine (FT4), and free triiodothyronine (FT3), and to correlate the hormone levels among iNPH patients with their self-reported quality of life before and three months after the surgery. Methods: Twenty-five patients (52% women), mean age 63.5 (SD 9.5) years, were operated on by inserting a VP shunt. Patients with FT3 level ≤3.34 pmol/L were diagnosed as having low T3 syndrome. Results: The changes in thyroid hormones resulted in a U-shaped curve throughout the follow-up period. The significant changes occurred the next day after the surgery, including a decrease in TSH, FT3, and an increase in FT4. Additionally, the decrease occurred in mean FT3 for six patients with preoperative low T3 syndrome. Three months after the surgery, thyroid hormones were restored to their baseline and/or normal values. All six patients with preoperative low T3 syndrome had significant improvement in all SF-36 subscales (except for the role emotional and physical). Patients with preoperative normal high FT3 and low FT4 had increased FT3/FT4 ratio which was associated with deterioration in all SF-36 subscales 3 months after the surgery. Conclusion: Routine assessment of the FT3/FT4 ratio might be a simple and effective tool for the risk stratification of iNPH patients before VP shunt surgery.

Effect of perioperative use of oral triidothyronine for infants undergoing complex congenital cardiac surgeries under cardiopulmonary bypass: A double-blinded randomised controlled study

Background

Thyroid hormone metabolism disrupts after cardiopulmonary bypass both in adults and pediatric patients. This is known as Euthyroid sick syndrome, and it is more evident in pediatric patients who were undergoing complex cardiac surgeries compared to adults. This decrease in serum T3 levels increases the incidence of low cardiac output, requirement of inotropes, prolonged mechanical ventilation, and prolonged intensive care unit (ICU) stay.

Aims and Objectives

The primary objective was to compare the mean Vasoactive-inotropic score (VIS) at 72 hours postoperatively between T3 and Placebo groups.

Materials and Methods

One hundred patients were screened, and 88 patients were included in the study. Triidothyronine 1 mic/kg 10 doses 8^th hourly was given orally postoperatively to cases and sugar sachets to controls. The blood samples for analysis of FT3, FT4, and TSH were taken every 24 hours postoperatively, and baseline values were taken after induction. Mean VIS scores, ejection Fraction (EF), Left ventricular outflow tract velocity time integral (LVOT VTi), hemodynamics and partial pressure of oxygen/ fraction of inspired oxygen(PaO2/FiO2) were recorded daily.

Results

The Mean VIS scores at 72 Hours postoperatively were significantly less in the T3 group (5.49 ± 6.2) compared to the Placebo group (13.6 ± 11.7). The PaO2/FiO2 ratios were comparatively more in the T3 group than the Placebo group. The serum levels of FT3 FT4 were significantly higher in the T3-supplemented group than the Placebo group. The VIS scores were significantly lower from 48 hours postoperatively in children < 6 months of age.

Conclusion

In this study, we observed that supplementing T3 postoperatively decreases the ionotropic requirement from 72 hours postoperatively. This is more useful in children <6 months of age undergoing complex cardiac surgeries.

Patterns and Determinants of Change in Cortisol Levels and Thyroid Function as a Function of Cardiac Risk in Children Undergoing Cardiac Surgery

Background

Children undergoing cardiac surgery with cardiopulmonary bypass (CPB) are exposed to the risk of hormonal imbalances resulting from acute stress, which may eventually result in high postoperative mortality and morbidity.

Objective

We assessed adrenal and thyroid hormonal changes and their determinants following cardiac surgery in children and explored their prognostic value in predicting cardiac outcomes. Study Design and Methods. A prospective cohort study was conducted at King Abdulaziz University Hospital (KAUH), between 2017 and 2018. The study involved 46 children aged 14 years or younger who underwent elective cardiac surgery with cardiopulmonary bypass. Serum levels of cortisol, TSH, fT3, and fT4 were measured preoperatively and 24, 48, and 72 hours after surgery. The cardiac risk was assessed using the risk adjustment for congenital heart surgery (RACHS) scale. A composite cardiovascular outcome was analyzed as a numerical variable and calculated as the number of cardiovascular events.

Results

Overall, the changes in thyroid function parameters resulted in a U-shaped curve, while cortisol levels yielded a bell-shaped curve. The most significant changes occurred at 24 hours postop, including a decrease in mean TSH by 2.08 μIU/L (p < 0.001), fT3 by 2.39 pmol/L (p < 0.001), and fT4 by 2.45 pmol/L (p < 0.001) and an increase in cortisol levels by 406.48 nmol/L (p < 0.001) with respect to the baseline. Cortisol concentration peaked higher and recovered slower among patients with high cardiac risk than their counterparts. Cardiovascular outcomes were independently predicted by the extent of the decline in fT4 and TSH at 48 and 72 hours postop, with reference to the baseline, and by the cortisol level at 24 h postop, independent of the baseline, besides the RACHS category.

Conclusion

Cardiac surgery among children yields a high adrenocortical response and a high incidence of nonthyroidal illness syndrome, increasing cardiovascular risk. A preventive management strategy involves improving surgical techniques to minimize trauma-related stress.

Relationship of Preoperative Thyroid Dysfunction to Clinical Outcomes in Pediatric Cardiac Surgery

CONTEXT

Thyroid function may be assessed in children before cardiac surgery because of concerns that hypothyroidism or thyrotoxicosis might adversely affect cardiac function perioperatively. However, the relationship between preoperative thyroid dysfunction and surgical outcomes is unknown.

OBJECTIVE

Determine the relationship between preoperative thyroid dysfunction and outcomes of pediatric cardiac surgery.

METHODS

Retrospective cohort study (January 2005 to July 2019).

SETTING

Academic pediatric hospital.

PATIENTS

All patients <19 years old who underwent cardiac surgery with cardiopulmonary bypass and had thyrotropin (TSH) measured within 14 days preoperatively. Exclusion criteria included neonates (≤30 days), preoperative extracorporeal life support, salvage operations, or transplantation procedures.

MAIN OUTCOME MEASURES

Subjects were stratified by preoperative TSH concentration (mIU/L): low (<0.5), normal (0.5-5), mildly high (5.01-10), or moderately high (>10). Outcomes were compared among subjects with normal TSH (control) and each group with abnormal TSH concentrations. The primary outcome was 30-day mortality. Secondary outcomes included time to extubation, intensive care unit and hospital length of stay, and operative complications.

RESULTS

Among 592 patients analyzed, preoperative TSH was low in 15 (2.5%), normal in 347 (58.6%), mildly high in 177 (29.9%), and moderately high in 53 (9.0%). Free thyroxine was measured in 77.4% of patients and was low in 0 to 4.4% of subjects, with no differences among TSH groups. Thirty-day mortality was similar among TSH groups. There were no differences in any secondary outcome between patients with abnormal TSH and patients with normal TSH.

CONCLUSION

Preoperative mild to moderate subclinical hypothyroidism was not associated with adverse postoperative outcomes in children undergoing cardiopulmonary bypass procedures.

Congenital Heart Disease and Thyroid Dysfunction: Combination, Association, and Implication

BACKGROUND

Patients with congenital heart disease have higher prevalence of thyroid dysfunction due to embryonic and genetic coexistence. Marked changes in cardiac function occur secondary to alternations in thyroid hormone levels. Cardiac catheterizations or cardiac surgeries with cardiopulmonary bypass can cause abnormalities in the circulating hormones, in the absence of primary thyroid disease. Therefore, monitoring of thyroid function should be routinely performed in children with congenital heart disease. Thyroid hormone supplementation has been postulated as a possible therapeutic option; however, the therapeutic decisions should be made based on individual circumstances, symptoms, and the severity of the thyroid dysfunction.

OBJECTIVES

To describe the correlation between congenital heart disease in children and thyroid dysfunction and the debate on monitoring, intervention, and treatment.

METHODS

PubMed, Clinical Key, and the Cochrane Library were searched using keywords relevant to congenital heart disease/surgery, cardiopulmonary bypass, thyroid hormones, sick euthyroid syndrome, and cardiac catheterization. Studies were limited to the English language and to children 0 to 18 years old. Studies in adults with important findings were reviewed as well. All clinical studies believed to have relevance were considered. All relevant studies were reviewed, and the most pertinent data were incorporated in this review.

CONCLUSION

There is lack of significant evidence concerning treatment for thyroid dysfunction in children with a congenital cardiac diagnosis. Adequately powered studies are needed before a uniform recommendation about treatment can be made.

Nonthyroidal illness in critically ill children

PURPOSE OF REVIEW

This review summarizes recent literature on nonthyroidal illness syndrome (NTI) and outcome of pediatric critical illness, to provide insight in pathophysiology and therapeutic implications.

RECENT FINDINGS

NTI is typically characterized by lowered triiodothyronine levels without compensatory TSH rise. Although NTI severity is associated with poor outcome of pediatric critical illness, it remains unclear whether this association reflects an adaptive protective response or contributes to poor outcome. Recently, two metabolic interventions that improved outcome also altered NTI in critically ill children. These studies shed new light on the topic, as the results suggested that the peripheral NTI component, with inactivation of thyroid hormone, may represent a beneficial adaptation, whereas the central component, with suppressed TSH-driven thyroid hormone secretion, may be maladaptive. There is currently insufficient evidence for treatment of NTI in children. However, the recent findings raised the hypothesis that reactivation of the central NTI component could offer benefit, which should be tested in RCTs.

SUMMARY

NTI in critically ill children can be modified by metabolic interventions. The peripheral, but not the central, component of NTI may be a beneficial adaptive response. These findings open perspectives for the development of novel strategies to improve outcome of critical illness in children.

Oral Triiodothyronine Supplementation Decreases Low Cardiac Output Syndrome After Pediatric Cardiac Surgery

The oral triiodothyronine for infants and children undergoing cardiopulmonary bypass (OTICC) trial showed that Triiodothyronine (T3) supplementation improved hemodynamic and clinical outcome parameters. We tested the validity of low cardiac output syndrome (LCOS), derived using clinical parameters and laboratory data, by comparing the LCOS diagnosis with objective parameters commonly measured in a cardiac intensive care unit (CCU) setting. OTICC, a randomized, placebo-controlled trial included children younger than 3 years with an Aristotle score between 6 and 9. We used the existing trial data set to compare the LCOS diagnosis with echocardiographic hemodynamic parameters. Additionally, we determined if LCOS, prospectively assigned during a clinical trial, served as an early predictor of clinical outcomes. All LCOS subjects at 6 and 12 h after cross-clamp release later showed significantly lower pulse pressure, stroke volume and cardiac output, and higher systemic vascular resistance. These LCOS patients also had significantly longer time to extubation (TTE) and higher mortality rate. LCOS incidence was significantly lower in the T3 treatment group [n = 86 vs. 66, respectively, p < 0.001; OR (95% CI) 0.43 (0.36-0.52)] particularly at 6 h. Also, LCOS patients in the placebo group had significantly lower FT3 serum levels over time. These analyses confirm that early clinically defined LCOS successfully predicts cardiac dysfunction determined later by objective hemodynamic echocardiographic parameters. Furthermore, early LCOS significantly impacts TTE and mortality. Finally, the data support prior clinical trial data, showing that oral T3 supplementation decreases early LCOS in concordance with reducing TTE.

Transient Secondary Hypothyroidism and Thyroid Hormone Replacement Therapy in Pediatric Postoperative Cardiopulmonary Bypass

Background:

To develop an understanding of current practices in the management of transient secondary hypothyroidism in pediatric postoperative cardiopulmonary bypass (CPB) patients.

Methods:

Electronic survey comprising a 10-item questionnaire was sent to sixty-four high volume pediatric heart centers in the United States and United Kingdom. Survey participants included cardiologists, intensivists, cardiothoracic surgeons, and advanced practice providers. A retrospective chart review was also performed at a large regional referral center in the Midwest on subjects 0-18 years old who underwent CPB from 2005-2015. Information obtained included a unique identifier, date of birth, age, procedure performed, CPB time, date of surgery and date and type of Thyroid Function Test (TFT) ordered.

Results:

1,153 individuals from 64 congenital heart centers were contacted via email to participate in the electronic survey. In the 3-month response window, 129 completed surveys were received from cardiologists (55%), intensivists (17%), surgeons (15%), “other” (8%), and advanced practice providers (5%). This yielded a response rate of 11.2%. Of the 129 respondents, only 10 providers routinely order TFTs prior to (n=7) and after (n=1) CPB or when clinically indicated (n=2). All 10 providers order thyroid stimulating hormone test, 7 order thyroxine, and 3 order triiodothyronine. Only 1 provider routinely treats children with prophylactic thyroid hormone replacement therapy after CPB. Our retrospective review included 502 CPB events with 442 unique patients. Of the events, 20 patients received preoperative TFT testing while 11 received postoperative testing.

Conclusions:

There is a general lack of uniformity in the evaluation, diagnosis, and treatment of transient secondary hypothyroidism in pediatric postoperative CPB patients.

Preoperative oral thyroid hormones to prevent euthyroid sick syndrome and attenuate myocardial ischemia-reperfusion injury after cardiac surgery with cardiopulmonary bypass in children: A randomized, double-blind, placebo-controlled trial

BACKGROUND

Both euthyroid sick syndrome and myocardial ischemia-reperfusion injury are common and have been significantly associated with morbidity and mortality after pediatric cardiac surgery with cardiopulmonary bypass. This single-center, prospective, double-blind, randomized placebo-controlled clinical pilot trial was designed to assess if preoperative oral thyroid hormone therapy could prevent the occurrence of euthyroid sick syndrome (ESS) and attenuate myocardial ischemia-reperfusion injury (IRI) after cardiac surgery with cardiopulmonary bypass (CPB) in children.

METHODS

Forty children aged 3 to 12 year, scheduled for elective congenital heart disease repair surgery with CPB, were randomized into 2 groups of equal size to receive the following treatments in a double-blind manner: placebo (control group) and thyroid tablet 0.4 mg/kg (trial group) taken orally once a day for 4 days before surgery. The perioperative serum thyroid hormone levels and hemodynamic variables were determined. The extubation time, duration of intensive care unit (ICU) stay, and use of inotropic drugs in the ICU were recorded. The myocardial expressions of heat shock protein 70 (HSP70), myosin heavy chain (MHC) mRNA, and thyroid hormone receptor (TR) mRNA were detected. The serum creatine kinase-MB (CK-MB) activity and troponin I (TnI) positive ratio at 24 hour after surgery were assessed.

RESULTS

There were no significant differences in hemodynamic variables at all observed points, extubation time, and duration of ICU stay between groups. As compared with baselines on administration, serum triiodothyronine (T3) and free T3 (FT3) levels on the first, second, and fourth postoperative day, and serum thyrotropic-stimulating hormone (TSH), tetraiodothyronine (T4), and free T4 (FT4) levels on the first postoperative day were significantly decreased in the 2 groups. Serum T3, FT3, and T4 levels on the first and second postoperative day, and serum FT4 level on the first postoperative day were significantly higher in the trial group than in control group. As compared with the control group, the number of patients requiring inotropic drugs in the ICU, serum CK-MB activity, serum positive TnI ratio, and myocardial expression of MHCβ mRNA were significantly decreased, and myocardial expressions of both HSP70 and MHCα mRNA were significantly increased in the trial group.

CONCLUSIONS

In children undergoing cardiac surgery with CPB, preoperative oral small-dose thyroid hormone therapy reduces severity of postoperative ESS and provides a protection against myocardial IRI by increasing HSP70 and MHCα expression.

Thyroid hormones and cardiovascular disease

Myocardial and vascular endothelial tissues have receptors for thyroid hormones and are sensitive to changes in the concentrations of circulating thyroid hormones. The importance of thyroid hormones in maintaining cardiovascular homeostasis can be deduced from clinical and experimental data showing that even subtle changes in thyroid hormone concentrations - such as those observed in subclinical hypothyroidism or hyperthyroidism, and low triiodothyronine syndrome - adversely influence the cardiovascular system. Some potential mechanisms linking the two conditions are dyslipidaemia, endothelial dysfunction, blood pressure changes, and direct effects of thyroid hormones on the myocardium. Several interventional trials showed that treatment of subclinical thyroid diseases improves cardiovascular risk factors, which implies potential benefits for reducing cardiovascular events. Over the past 2 decades, accumulating evidence supports the association between abnormal thyroid function at the time of an acute myocardial infarction (MI) and subsequent adverse cardiovascular outcomes. Furthermore, experimental studies showed that thyroid hormones can have an important therapeutic role in reducing infarct size and improving myocardial function after acute MI. In this Review, we summarize the literature on thyroid function in cardiovascular diseases, both as a risk factor as well as in the setting of cardiovascular diseases such as heart failure or acute MI, and outline the effect of thyroid hormone replacement therapy for reducing the risk of cardiovascular disease.

Long-Term Neurodevelopmental Outcome of Children Treated with Tri-Iodothyronine after Cardiac Surgery: Follow-Up of a Double-Blind, Randomized, Placebo-Controlled Study

BACKGROUND

Transient thyroid dysfunction occurs in children after cardiopulmonary bypass (CPB). We demonstrated significant benefits of acute postoperative tri-iodothyronine (T3) treatment for recovery and myocardial function. Now we report the long-term neurodevelopment of these children.

METHODS

Twenty-eight children (70% of the original study population) could be recruited for a follow-up examination (median age 10.7 years, range 10-19.6 years) retaining the double-blind, randomized, placebo-controlled protocol. Cognitive function and motor development were tested, as were growth and thyroid and cardiac functions.

RESULTS

The median full-scale intelligence quotient of all children was within the reference range and similar in the placebo and T3 groups. Tests for motor and cognitive functions, growth, and thyroid and cardiac functions revealed concurrent results.

CONCLUSIONS

Overall intellectual development is preserved in adolescents treated with CPB in infancy irrespectively of low postoperative thyroid hormone concentrations. While acute postoperative T3 treatment in children after CPB improves recovery, no significant long-term effects on neurodevelopment could be detected. We therefore speculate that transient postoperative thyroid dysfunction by means of nonthyroidal illness syndrome is predominantly mediated by extranuclear, nongenomic mechanisms and thus acutely affects the cardiovascular system but not the development of the central nervous system mediated by genomic mechanisms.

Thyroid Hormone in the Pediatric Intensive Care Unit

Thyroid hormones are key factors necessary for normal growth and development in children. They have tight control of metabolic rate and, as a result, frequently become altered in their synthesis and/or release during times of stress or critical illness. Disturbances in thyroid hormone homeostasis have been well described in several pathologic states, including sepsis/septic shock, renal failure, trauma, severe malnutrition, and following cardiopulmonary bypass. Specifically, a decrease in serum triiodothyronine (T₃) and a concomitant increase in reverse triiodothyronine (rT₃) levels are the most common changes observed. It is further noteworthy that serum thyroxine (T₄), rT₃, and T₃ levels change in relation to severity of nonthyroidal illness. Many past investigators have speculated that these alterations are a teleological adaptation to severe illness and the increased metabolic demands that critical illness bears. However, this paradigm has been challenged through multiple avenues and has lost support over the past few years. Instead the "inflammatory hypothesis" has emerged implicating a cytokine surge as the mediator of thyroid hormone disruption. Overall, the demonstrated association between low thyroid hormone levels and poor clinical outcomes, the beneficial effects of thyroid hormone supplementation in multiple critically ill subpopulations, and the well-established safety profile of T₃ therapy make thyroid hormone supplementation in the pediatric ICU worth consideration.

Thyroid function status and its impact on clinical outcome in patients admitted to critical care

OBJECTIVE

To analyze alterations in thyroid function and the correlation between results of thyroid function test and mortality in medical and surgical intensive care unit (ICU) patients. It also aimed to evaluate the effect of thyroid dysfunction in ICU patients and their need for mechanical ventilation (MV).

METHODS

A single-center, prospective, observational study was conducted on patients admitted to medical and surgical ICU between 2013-2014.. Clinical and paraclinical findings (free triiodothyronine, free thyroxine and thyroid stimulating hormone) were documented for all patients. Regression analysis and chi-square were used for death and MV outcome variables.

RESULTS

We included 502 patients. Of these, 340 (67.7%) were admitted to the medical ICU. Results of thyroid function tests were normal in 320 (64%) and 162 (32.3%) medical and surgical ICU patients, respectively. Euthyroid sick syndrome (ESS) was documented in 86 patients (17%). Mortality was twice higher among surgical ICU patients with ESS compared to those with normal thyroid function (p=0.085), which is not statistically significant. Based on thyroid function status, no differences in the risk to be mechanically ventilated was found between medical or surgical ICU patients.

CONCLUSION

There is a significant association between ESS and mortality in ICU patients. Future studies should determine whether abnormal thyroid function increases the risk for MV in ICU patients.

Central regulation of hypothalamic-pituitary-thyroid axis under physiological and pathophysiological conditions

TRH is a tripeptide amide that functions as a neurotransmitter but also serves as a neurohormone that has a critical role in the central regulation of the hypothalamic-pituitary-thyroid axis. Hypophysiotropic TRH neurons involved in this neuroendocrine process are located in the hypothalamic paraventricular nucleus and secrete TRH into the pericapillary space of the external zone of the median eminence for conveyance to anterior pituitary thyrotrophs. Under basal conditions, the activity of hypophysiotropic TRH neurons is regulated by the negative feedback effects of thyroid hormone to ensure stable, circulating, thyroid hormone concentrations, a mechanism that involves complex interactions between hypophysiotropic TRH neurons and the vascular system, cerebrospinal fluid, and specialized glial cells called tanycytes. Hypophysiotropic TRH neurons also integrate other humoral and neuronal inputs that can alter the setpoint for negative feedback regulation by thyroid hormone. This mechanism facilitates adaptation of the organism to changing environmental conditions, including the shortage of food and a cold environment. The thyroid axis is also affected by other adverse conditions such as infection, but the central mechanisms mediating suppression of hypophysiotropic TRH may be pathophysiological. In this review, we discuss current knowledge about the mechanisms that contribute to the regulation of hypophysiotropic TRH neurons under physiological and pathophysiological conditions.

Low triiodothyronine predicts mortality in critically ill patients

OBJECTIVE

Alteration in thyroid hormones are seen in critically ill patients admitted to intensive care units. Our objective was to study the thyroid hormone profile, prolactin and, glycosylated hemoglobin (HbA1c) at admission and analyze their correlation with mortality.

MATERIALS AND METHODS

In this single centre, prospective, observational study, 100 consecutive patients (52M; 48F) admitted to medical ICU irrespective of diagnosis were included. Patients with previous thyroid disorders and drugs affecting thyroid function were excluded. All participants underwent complete physical examination and a single fasting blood sample obtained at admission was analyzed for total triiodothyronine (T3), total thyroxine (T4), thyroid stimulating hormone (TSH), HbA1c, and prolactin. The patients were divided into two groups: Group 1 - survivors (discharged from the hospital) and Group 2 - nonsurvivors (patients succumbed to their illness inside the hospital). The data were analyzed by appropriate statistical methods and a P-value of <0.05 was considered significant.

RESULTS

The mean age of the participants was 58.7 ± 16.9 years and the mean duration of ICU stay was 3.3 ± 3.1 days. A total of 64 patients survived, whereas remaining 36 succumbed to their illness. The baseline demographic profile was comparable between survivors and nonsurvivors. Nonsurvivors had low T3 when compared with survivors (49.1 ± 32.7 vs. 66.2 ± 30.1, P = 0.0044). There was no significant difference observed between survivors and nonsurvivors with respect to T4, TSH, HbA1c, and prolactin.

CONCLUSION

Our study showed that low T3 is an important marker of mortality in critically ill patients. Admission HbA1c, prolactin, T4, and TSH did not vary between survivors and nonsurvivors.

Cardiopulmonary bypass and serum thyroid hormone profile in pediatric patients with congenital heart disease

OBJECTIVE

To study the effect of cardiopulmonary bypass (CPB) on serum thyroid hormone profile in children undergoing open-heart surgery.

DESIGN

Prospective cross-sectional study.

SETTING

Multispecialty tertiary level referral center.

PATIENTS

One hundred consecutive patients (age 15.9 ± 14.6 months, weight 6.7 ± 2.5 kg) undergoing open-heart surgery under CPB.

INTERVENTIONS

None.

OUTCOME MEASURES

Levels and trends of serum total thyroxine (TT4), free thyroxine (FT4), total tri-iodothyronine (TT3), free tri-iodothyronine (FT3) and thyroid stimulating hormone (TSH), survival, inotropic score, duration of mechanical ventilation, postoperative complications.

RESULTS

TT4 levels were 9.08 ± 3.6, 6.4 ± 2.5, 6.24 ± 2.1, 6.43 ± 2.4, 7.20 ± 3.0 µg/dL at baseline and at 1, 24, 48 and 72 hours; FT4 levels were 1.82 ± 0.5, 1.49 ± 0.3, 1.29 ± 0.3, 1.32 ± 0.4, and 1.43 ± 0.5 ng/dL; TT3 levels were 1.81 ± 0.4, 1.31 ± 0.3, 0.99 ± 0.2, 1.0 ± 0.37, and 1.17 ± 0.48 ng/ml; FT3 levels were 4.09 ± 1.0, 3.02 ± 0.8, 2.21 ± 0.6, 2.22 ± 0.7, and 2.66 ± 1.05 pg/ml; TSH levels were 5.40 ± 3.8, 2.0 ± 3.1, 1.24 ± 1.1, 2.90 ± 3.3, and 4.03 ± 3.4 mIU/L. There was significant fall (29.1% for FT4, 32.1% for TT4, 77% for TSH, 46% for FT3 and 45% for TT3, p < 0.0001). When area under curve (AUC) TT4 was compared between survivors (n = 87) and nonsurvivors (n = 12), significantly larger AUC was seen in survivors (492.81 ± 158.6) than nonsurvivors (360.75 ± 179.6 p = 0.0125). In survivors >72 hours, AUC TT4 was larger in patients with uneventful postoperative course versus those with postoperative complications (516.48 ± 18.6 vs. 394.78 ± 29.9, p = 0.001). AUC TT4 showed significant inverse correlation with inotropic score and borderline inverse correlation with duration of mechanical ventilation.

CONCLUSION

Children undergoing surgery under CPB showed significant fall in thyroid hormones. Because TT4 level is modifiable, prophylactic administration of TT4 for improving outcomes needs to be studied further.

Evaluation and clinical application of changes in thyroid hormone and TSH levels in critically ill full-term newborns

INTRODUCTION

The term "euthyroid sick syndrome" (ESS) has been used to describe a pattern of thyroid hormone changes during the course of critical illness in adult patients without thyroid disease, often associated with reduced thyroid hormone secretion.

OBJECTIVE

To describe the thyroid hormone profile in full-term newborns critically ill compared with thyroid hormone profile of healthy infants, and determine if alterations could be related to the severity of the disease and outcome.

METHODS

A cross-sectional, observational, and prospective study of full-term infants admitted to the neonatal intensive care unit (NICU) of the Hospital de Pediatría J.P. Garrahan between July 2007 and April 2008. Serum T3, T4, and thyroid stimulating hormone (TSH) levels were measured at admission and severity of the disease was evaluated through SNAP, lactic acid, respiratory assistance and number of organs affected.

RESULTS

Sick newborns showed significantly lower T3 and T4 levels compared with healthy infants [T3: -0.97 μg/dL (95% CI -0.89, -1.13) and T4: -4.37 μg/dL (95% CI -2.95, -5.78)]. Only 29 out of 94 (31%) infants presented a normal profile; 37 (39%) infants showed isolated low T3 levels, 20 (21%) infants had low T3 and T4 levels and eight (9%) infants had low TSH, T3, and T4. Of this latter group, five of eight (62%) children died suggesting a significantly higher risk of death for patients with low T3 associated with low T4 and TSH [Risk ratio (RR) 10.75 95% CI 3.93, 29].

CONCLUSIONS

Full-term sick newborns frequently have lower thyroid hormone levels than healthy ones. These observed thyroid hormones changes might be related to the underlying disease and could be used as a prognostic marker of the severity and fatal outcome of the patient.

Serum thyroid hormone profile in critically Ill children

OBJECTIVE

To study thyroid hormone profile in critically ill children and its correlation to disease severity and clinical outcome.

METHODS

Total serum triiodothyronine (T3), thyroxine (T4) and TSH were estimated at admission and discharge from PICU/ just before death.

RESULTS

Mean T3 levels in cases were significantly lower than controls and lower in patients who expired, both at admission and just prior to death. Mean T4 levels were lower in cases, and just prior to death. Mean TSH levels were not different in cases and controls; or in survived and expired cases. When both T3 and T4 are low, mortality risk increases 30 times. Serum T3, T4 and TSH values improved in patients who survived unlike in those who expired. Age, sex, duration of hospital stay, ventilation, inotropic support, and PICU stay did not show any correlation with patient outcome or thyroid hormone profile. PRISM score at 24 hours and T4 levels in the second sample were significant predictors of survival.

CONCLUSION

T3 levels reflect the patient's clinical status, T4 levels can predict survival.

Nonthyroidal illness syndrome in children

Neuroendocrine changes in the hypothalamic-pituitary-thyroid axis during critical illness result in nonthyroidal illness syndrome (NTIS) characterized by abnormal thyrotropin (TSH) and thyroid hormone levels. Studies looking at the natural history of neuroendocrine changes during critical illness have revealed the presence of NTIS. NTIS has been described in a variety of patient settings. Many studies have tried to uncover the pathophysiology behind NTIS and several theories are proposed. Whether NTIS requires treatment or intervention is still controversial and the results of the treatment studies are arguably mixed. Whether implicitly stated or not, the underlying purpose of all the natural history, pathophysiology, or treatment studies is to determine whether NTIS is adaptive or maladaptive. Some studies have illustrated a correlation between illness severity and the degree of NTIS but a cause and effect relationship is still elusive. The human studies can be divided between those with either adult or pediatric subjects, with much less data available in the latter. This review examines the available literature on NTIS with an emphasis on the pediatric literature.

Nonthyroidal illness syndrome and euthyroid sick syndrome in intensive care patients

This article reviews the pathophysiology of non-thyroidal illness syndrome (NTIS) and euthyroid sick syndrome (ESS), a multifactorial phenomenon characterized by suppression of thyroid hormone levels that has been described in several disease states, probably due to different causes in different patients. It also describes the laboratory values of thyroid function tests (TFTs), relevant animal studies, the association of NTIS and ESS with cardiovascular problems and sepsis, and the rationale for treatment.