hypothyroidism before and after surgery
Due to the manifold effects of thyroid hormone across virtually all organ systems, the complications associated with thyroid dysfunction are numerous and diverse. The stresses encountered during the perioperative period may exacerbate underlying thyroid disorders, potentially precipitating decompensation and even death.
Challenges of patients with hypothyroidism before and after surgery
it is of the utmost importance for the clinician to comprehend the mechanisms by which thyroid disease may complicate surgery and postoperative recovery and to be cognizant of the most effective means of optimizing the status of thyrotoxic and hypothyroid patients perioperatively.
Cardiovascular failure
Thyroid hormones play a crucial role in homeostasis due to their effects on the cardiovascular, respiratory, renal, gastrointestinal, hematologic, and central nervous systems. The cardiovascular concerns are among the most relevant in perioperative situations. Patients with hypothyroidism are at increased risk of coronary events2 possibly due to increased cholesterol levels,3 prolonged half-life of multiple coagulation factors,4 and anemia.5 Nonspecific ST changes and low voltage on electrocardiogram are observed and, less commonly, “torsade de pointes” ventricular tachycardia has been described.6
Hypothyroidism has been associated with a diminished cardiac output of 30% to 50%, with both slowing of the pulse and decreased contractility.7 Furthermore, deficiency of thyroid hormones causes an increase in peripheral vascular resistance resulting in increased cardiac afterload, leading to a decreased pulse pressure via an increase in diastolic pressure and a decrease in systolic blood pressure.8 Even though catecholamine levels are increased in these patients, hypothyroid patients have a predisposition to develop hypotension under anesthesia
Renal and pulmonary system failure
In addition to the cardiovascular concerns, hypothyroid patients face additional challenges due to the ventilatory dysfunction and renal manifestations associated with this condition. Pleural effusions and respiratory muscle weakness, along with impaired hypoxic and hypercapnic respiratory drive and increased prevalence of obstructive sleep apnea, may complicate their perioperative management, as may a predisposition to pneumonia and atelectasis.8 Increased antidiuretic hormone leads to hyponatremia. These pulmonary and renal factors contribute to the increased susceptibility of hypothyroid patients to anesthetics, tranquilizers, and narcotics.
Decreased gastrointestinal motility
Decreased gastrointestinal motility, which is most commonly manifested as constipation in hypothyroid patients, increases the tendency for postoperative ileus.14 This is of increased concern considering that postoperative pain management regimens commonly use opioids which independently promote constipation.
Anemia
Hypothyroidism is associated with several hematologic effects. Most commonly described is a normochromic, normocytic anemia. However, because of the increased prevalence of pernicious anemia among patients with hypothyroidism, concomitant autoimmune-mediated vitamin B12 deficiency may cause macrocytosis.
Myxedema coma
A rare, yet most dreaded complication of surgery in hypothyroid patients is myxedema coma, a condition that has been associated with mortality as high as 80%. It is commonly associated with a precipitant such as surgery, infection, cold exposure, and administration of sedatives.
Preoperative Considerations and Preoperative Screening in the Hypothyroid Patient
Due to the myriad effects of thyroid hormone throughout the body, the effects of thyroid dysfunction are manifold and may complicate surgical procedures and postoperative recovery. Thus, although routine screening to detect thyroid disease is not indicated in patients where there is no index of suspicion for the same, the recognition, diagnosis, and optimization of preexisting thyroid conditions in patients undergoing surgery are important perioperative considerations. Patients with thyroid dysfunction are well represented in the general population. Studies report the prevalence of abnormal thyrotropin values to be as high as 21% in women and 3% in men.
Routine preoperative thyroid function testing is not recommended for patients with no history of thyroid dysfunction. In such patients, it would be appropriate to check the thyrotropin (TSH) level if there is a reason to suspect thyroid disease based on symptoms such as unexplained weight changes, palpitations, tremor or changes in bowel habits, skin, hair, or eyes that suggest thyroid dysfunction.
In patients with known hypothyroidism or hypothyroidism who have been undergoing treatment, a TSH test should be included in the preoperative assessment to determine the adequacy of treatment and to ensure that thyroid therapy is optimized before surgery.
The pathophysiologic changes associated with hypothyroidism are generally reversible with replacement of thyroid hormone. Thus, rather than face the risk of acute decompensation, it is preferable to postpone elective surgery until adequate treatment with thyroid hormone has achieved euthyroidism.
References
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5398303/
