Influence of hypothyroidism on the postoperative course in elderly patients undergoing cardiac surgery

Background

An accurate diagnosis of hypothyroidism in elderly people may be challenging. Due to nonspecific symptoms it is usually performed at an advanced stage of the disease. The most frequent symptoms include persistent feeling of cold, dry skin/desquamation of skin, urine incontinence, worsening of anginal pain, changes in blood pressure, and constipation. The most frequent findings on physical examination are thick and pale skin, subcutaneous deposits of mucopolysaccharides, oedema of the eyebrows, cardiomegaly, and pleural and pericardial effusion. Laboratory findings consist of hyperlipidaemia, anaemia and hyponatraemia. In the elderly patient the symptoms of hypothyroidism may be masked by symptoms of other commonly present diseases such as bradycardia or ventricular arrhythmia in the course of coronary artery disease, respiratory failure, chronic obstructive pulmonary disease on steroid therapy with forced expiratory volume in 1 s (FEV1) < 60% of the reference values, previous stroke, dementia, diabetes or renal failure with glomerular filtration rate (GFR) < 60 ml/min [1-3].

Aim

The aim of the study was to assess whether a complicated postoperative course in elderly patients may be influenced by stress-related hypothyroidism.

Material and methods

The study included 312 patients  65 years of age who underwent cardiac surgery between 01.01.10 and 31.12.10 with euthyroidism documented before the surgery. Patients were divided into two groups. Group I included those with postoperative hypothyroidism (n = 295) and group II consisted of patients with postoperative hypothyroidism (n = 17). A panel of thyroid tests (TSH, fT3, fT4) was performed in all patients  65 years of age before the surgery and on day 5 after the surgery. Hormonal profile was assessed in the Drug Monitoring Laboratory of the Silesian Center for Heart Diseases by means of a non-isotopic immuno chemiluminescent method (CHLIA) which is characterized by high sensitivity (0.02 mIU/l and lower). Currently valid reference ranges were used: for thyroid-stimulating hormone (TSH) 0.47-4.64 mIU/l, for triiodothyronine (fT3) 1.45-3.48 pg/ml and for tetraiodothyronine (fT4) 0.45-1.37 ng/ml. The analysed geriatric patients suffered from many comorbidities which in both groups included mainly diabetes, chronic renal failure and peripheral atherosclerosis. Demographic and clinical characteristics of both studied groups are presented in Tables 1-2.

Results

One of the leading complications which occurred in the elderly patients after cardiac surgery, both in euthyroidism and hypothyroidism in the postoperative period, was a cognitive disorder in the form of delirium (8.3% vs. 23.5%; p < 0.001 vs. p = 0.04).

Respiratory therapy prolonged > 24 h was required in 29.4% (p = 0.041) of the elderly patients with diagnosed postoperative hypothyroidism, which led to a worse prognosis and ended with death in 11.7% of cases.

One fifth of the elderly patients with hypothyroidism in the postoperative period had a tendency towards accumulation of pericardial effusion. Acute cardiac tamponade requiring surgical decompression was noted in 4 patients (23.5%, p < 0.001).

Perioperative myocardial infarction occurred sporadically (1.4%, p = 0.949 vs. 7.0%, p = 0.525) and was insignificantly more frequent in the group of elderly patients with postoperative hypothyroidism. In 40% of the elderly patients with postoperative hypothyroidism pleural effusion required mechanical decompression (p < 0.001).

In contrast, the occurrence of pericardial effusion was very rare in operated patients with postoperative euthyroidism (3.5% vs. 3.9%, p = 0.705). The results are presented in Table 3.

Discussion

Currently used methods of thyroid hormone profiling such as the immuno chemiluminescence (CHLIA) used in our centre are characterized by very high sensitivity (< 0.02 ml/l) and therefore allow detection not only of primary but also of secondary (postoperative) hypothyroidism [4].

The diagnosis of hypothyroidism in patients after surgery is challenging. Low level of TSH, but also fT3 and fT4, may be worrisome in the first days after the procedure.

A few available scientific reports suggest that key factors expressing a suppressive effect on the excretion of TSH in patients in poor general condition include inflammatory factors such as cytokines, catecholamines (dopamine) and some hormones, for example steroids. Perioperative complications in the first hours after the surgery may lead to a decrease of TSH concentration to 0.02- 0.3 µIU/ml [5-7].

During recovery after the surgery, TSH concentration may increase to 20 µIU/ml. Difficulties in differential diagnosis between low T3/T4 and secondary or tertiary hypothyroidism may be resolved by means of pituitary gland or hypothalamus imaging (magnetic resonance imaging – MRI, computed tomography – CT) or by measurement of other hormones secreted by the anterior lobe of the pituitary gland and rT3. The TSH concentration of 0.05-10 mIU/l in hospitalized patients does not necessarily need to indicate a thyroid disease and therefore in this group of patients it is indicated not to assess TSH level or initiate therapy without a clear reason [8].

Observations from our centre based on a detailed analysis of each elderly patient suggest that a decision to initiate treatment with thyroid hormones is rational in patients presenting with symptoms of hypothyroidism. A decision to initiate hormonal therapy was made in each case of low fT3 concentration regardless of TSH level in an elderly patient who was in euthyroidism before the surgery and demonstrated normal psycho-physical activity, but suffered from delirium, depressed systolic heart function, effusion into the serous cavities and had a slow rehabilitation process. The importance of early detection and initiation of hormonal substitution in hypothyroidism was demonstrated by Rodondi et al., who assessed the risk of congestive heart failure episodes, coronary incidents, stroke, peripheral arterial disease and mortality from any cause in 2730 patients (mean age: 74.7 years) without known cardiovascular disease, but with diagnosed postoperative subclinical hypothyroidism. The authors found an increased frequency of heart failure episodes in patients with TSH concentration  7 µIU/ml [8].

In the case of an elderly patient with postoperative hypothyroidism, successful ending of hospitalization on the cardiac surgery ward is not limited to initiation of hormonal substitution. Other important issues include specialized care by physicians and nurses, psychological reassurance, continuation of efficient rehabilitation at home with help from the family or, in the case of institutionalisation, from the patient’s guardians.

Conclusions

Postoperative hypothyroidism increases the risk of postoperative complications in elderly patients. All patients

≥ 65 years of age should undergo an assessment of the thyroid hormonal function before and after cardiac surgery.

References

 1. Sawin CT, Chopra D, Azizi F, et al. The aging thyroid: increased prevalence of elevated serum thyrotropin levels in the elderly. JAMA 1979; 242: 247-250.

 2. Lewis GF, Alessi CA, Imperial JG, Refetoff S. Low serum free thyroxine index in ambulating elderly is due to a resetting of the threshold of thyrotropin feedback suppression. J Clin Endocrinol Metab 1991; 73: 843-849.

 3. Harman SM, Wehmann RE, Blackman MR. Pituitary-thyroid hormone economy in healthy aging men: basal indices of thyroid function and thyrotropin responses to constant infusions of thyrotropin releasing hormone. J Clin Endocrinol Metab 1984; 58: 320-326.

 4. Sawin CT, Geller A, Kaplan MM, et al. Low serum thyrotropin (thyroid-stimulating hormone) in older persons without hyperthyroidism. Arch Intern Med 1991; 151: 165-168.

 5. Wiener K, Utiger RD, Lew R, Emerson CH. Age, sex and serum thyrotropin concentrations in primary hypothyroidism. Acta Endocrinol (Copenh) 1991; 124: 364-369.

 6. Wenzel KW, Horn WR. Triiodothvromine (T3) and thyroxine (T4) kinetics in aged men. In: Tyroid research. Robbins J, Utiger RD (eds). Excerpta Medica, Amsterdam 1976; 270-273.

 7. Levy EG. Thyroid disease in the elderly. Med Clin North Am 1991; 75: 151-167.

 8. Francis T, Wartofsky IL. Common thyroid disorders in the elderly. Postgrad Med 1992; 92: 225-230, 233-236.