Propranolol does not prevent thyroid storm

A Patient with Graves' Disease Scheduled for Thyroidectomy with High Risk for Thyroid Storm Caused by Severe Medication Nonadherence: Anaesthetic and Surgical Considerations

In patients with failed hormone regulation who are scheduled for indispensable total thyroidectomy, the risk of thyroid storm with severe end-organ complications has to be anticipated. This case report presents the successful surgical and anaesthesiological management of a patient with Graves' disease, without any signs of perioperative thyroid storm. Possible recommendations for treatment are presented.

Thyroid emergencies

Myxedema coma and thyroid storm are among the most common endocrine emergencies presenting to general hospitals. Myxedema coma represents the most extreme, life threatening expression of severe hypothyroidism with subjects presenting with deteriorating mental status, hypothermia, and multiple organ system abnormalities. It typically appears in patients with pre-existing hypothyroidism via a common pathway of respiratory decompensation with CO₂ narcosis leading to coma. Without early and appropriate therapy, there is often a fatal outcome. It is a clinical diagnosis based on history and physical findings at presentation and not on any objective thyroid laboratory tests. Clinically based scoring systems have been proposed to aid in the diagnosis. While a relatively rare syndrome, the typical patient is an elderly woman (thyroid hypofunction being much more common in women) who may or may not have a history of previously diagnosed or treated thyroid dysfunction. Thyrotoxic storm or thyroid crisis also is a rare condition and it too reflects a clinical diagnosis. Diagnosis is based upon the appearance of severe hyperthyroidism accompanied by elements of systemic decompensation. Based upon the prospect of high mortality without aggressive treatment, therapy must be initiated as early as possible in a critical care setting. There are no clues to diagnosis based upon laboratory tests alone, but several scoring systems have been developed to aid in diagnosis. The usual clinical signs and symptoms of hyperthyroidism will be present along with more exaggerated clinical manifestations affecting the cardiovascular, gastrointestinal, and central nervous systems. A multi-pronged treatment approach has been recommended and has been associated with improved outcomes.

ANNIVERSARY REVIEW: Antithyroid drug therapy: 70 years later

The thionamide antithyroid drugs were discovered in large part following serendipitous observations by a number of investigators in the 1940s who found that sulfhydryl-containing compounds were goitrogenic in animals. This prompted Prof. Edwin B Astwood to pioneer the use of these compounds to treat hyperthyroidism in the early 1940s and to develop the more potent and less toxic drugs that are used today. Despite their simple molecular structure and ease of use, many uncertainties remain, including their mechanism(s) of action, clinical role, optimal use in pregnancy and the prediction and prevention of rare but potentially life-threatening adverse reactions. In this review, we summarize the history of the development of these drugs and outline their current role in the clinical management of patients with hyperthyroidism.

The Pharmacotherapy of Thyroid Storm

A review of thyrotoxic storm is presented. Included are causes, symptomatology, and mortality rates. Special emphasis is placed on the strong correlation between adrenergic blockade and success rates in treating thyrotoxic storm. Pharmacotherapy of the acute storm patient is discussed in detail with respect to agents that (1) decrease production of thyroid hormones; (2) block release of preformed thyroid hormones from the gland; (3) blunt the effects of excess thyroid hormones on the various target organs (e.g., CNS and heart); and (4) serve to decrease the metabolic strain on all organ systems caused by thyrotoxic storm.

Thyrotoxic Storm

Thyrotoxic storm is a syndrome of exaggerated thyrotoxicosis with systemic decompensation seen in 1-2% of hospital admissions for thyrotoxicosis. The diagnosis is based on recognition of typical cardinal manifestations, but even when diagnosed and treated, mortality rates are high. Results of thyroid function tests may be no more abnormal than those seen in uncomplicated thyrotoxicosis. Often, there is a history of partially treated thyrotoxicosis, and/or decompensation related to a precipitating event such as infection, stroke, pulmonary embolism, or radioiodine therapy. Treatment must be aggressive and includes volume repletion with i.v. glucose and saline, and pressor agents may be needed. Patients belong in an intensive care unit, with a cooling blanket for hyperpyrexia. Appropriate cardiac medications are employed to control ventricular rate in those with atrial fibrillation. The thyroid is blocked by large doses of antithyroid agent. In patients unable to swallow, tablets can be crushed and given by nasogastric tube or per rectum. After antithyroid drugs are started, stable iodine as Lugol's solution is given to block further hormone release from the gland. Sodium ipodate can be used instead of iodine and has the advantage of inhibiting conversion of T4 to T3. In severe cases, thyroid hormone may be removed from the circulation by peritoneal dialysis or plasmapheresis, and cholestyramine resin may be used to bind T4 and T3 within the gastrointestinal tract. β-adrenergic antagonists such as propranolol are given, or the very short-acting β-adrenergic blocker, esmolol, has also been used with success. A Swan-Ganz catheter is used to monitor central hemodynamics, especially in patients receiving high-dose propranolol, pressors, digoxin, diuretics, and fluids. Large doses of dexamethasone have been given based on presumed increased glucocorticoid requirements in thyrotoxicosis and because adrenal reserve may be reduced. Therapy must be continued until a normal metabolic state is achieved, at which time iodine is progressively withdrawn and plans made for definitive treatment.

Thyroid-adrenergic interactions: physiological and clinical implications

The sympathoadrenal system, including the sympathetic nervous system and the adrenal medulla, interacts with thyroid hormone (TH) at various levels. Both systems are evolutionary old and regulate independent functions, playing probably independent roles in poikilothermic species. With the advent of homeothermy, TH acquired a new role, which is to stimulate thermogenic mechanisms and synergize with the sympathoadrenal system to produce heat and maintain body temperature. An important part of this new function is mediated through coordinated and, most of the time, synergistic interactions with the sympathoadrenal system. Catecholamines can in turn activate TH in a tissue-specific manner, most notably in brown adipose tissue. Such interactions are of great adaptive value in cold adaptation and in states needing high-energy output. Conversely, in states of emergency where energy demand should be reduced, such as disease and starvation, both systems are turned down. In pathological states, where one of the systems is fixed at a high or a low level, coordination is lost with disruption of the physiology and development of symptoms. Exaggerated responses to catecholamines dominate the manifestations of thyrotoxicosis, while hypothyroidism is characterized by a narrowing of adaptive responses (e.g., thermogenic, cardiovascular, and lipolytic). Finally, emerging results suggest the possibility that disrupted interactions between the two systems contribute to explain metabolic variability, for example, fuel efficiency, energy expenditure, and lipolytic responses.

Perioperative management of the thyrotoxic patient

Preoperative thyrotoxicosis is a potentially life-threatening condition that requires medical intervention before surgery. Most patients are undergoing thyroidectomy for persistent thyrotoxicosis, usually Graves' disease, either having contraindications to or failing medical therapy. Fewer patients are undergoing nonthyroidal surgery that is likely urgent or emergent. The choice of treatment depends on the time available for preoperative preparation, the severity of the thyrotoxicosis, and the impact of any current or previous therapies. Generally treatment is directed at a combination of targets in the thyroid hormone synthetic, secretory, and peripheral pathway with concurrent treatment to correct any decompensation of normal homeostatic mechanisms. Thionamides are the preferred initial treatment unless contraindicated, but do require several weeks to render a patient euthyroid. beta-Blockers should always be used unless absolutely contraindicated because they improve thyrotoxic symptoms especially of the cardiovascular system. Other agents including iodine and steroids can be used if rapid preparation is required or more severe thyrotoxicosis is present. The goal of therapy is to render the patient as close as possible to clinical and biochemical euthyroidism before surgery. Overall, the morbidity and mortality of adequately prepared patients is low.

Use of propranolol and potassium iodate in the presurgical management of hyperthyroid cats

A prospective study was carried out using a combination of propranolol and potassium iodate to assess whether there were beneficial effects in preparing hyperthyroid cats for surgical thyroidectomy. Group A (n = 11) received propranolol from days 1 to 10, followed by propranolol and potassium iodate from days 11 to 20; group B (n = 10) received the reverse regimen. Blood samples were taken daily for subsequent determination of serum total L-thyroxine (TT4), L-triiodothyronine (TT3) and reverse T3 (rT3) concentrations. The signs of hyperthyroidism improved in all cats over the treatment period. At surgery, 36 per cent of the cats in group A had reference range serum TT4 concentrations, while 89 per cent with initially elevated TT3 concentrations had reference range concentrations. In group B, 10 per cent of the cats had reference range TT4 concentrations, while 75 per cent with initially elevated TT3 concentrations had reference range concentrations. The drug regimen used in group A was better tolerated and more effective and offers an alternative before thyroidectomy in cats that cannot tolerate carbimazole.

Successful treatment of massive acute thyroid hormone poisoning with iopanoic acid

We report a toddler with massive thyroid hormone poisoning in whom the addition of iopanoic acid to the treatment regimen (propylthiouracil and propranolol) resulted in a dramatic clinical and biochemical improvement. Iopanoic acid is a safe and effective drug in the treatment of massive thyroid hormone poisoning in children.

Beta-adrenergic blockade for the treatment of hyperthyroidism

PURPOSE

To review the clinical and biochemical effects of beta-adrenergic blocking drugs on hyperthyroidism.

MATERIALS AND METHODS

Studies published since 1972 were identified through a computerized search of MEDLINE and extensive searching of the bibliographies of the articles identified. Based on an understanding of the differences in beta-blocker metabolism in euthyroid and hyperthyroid patients, we reviewed the differences in pharmacokinetics and metabolic and clinical outcomes during their use in hyperthyroidism, as reported in the articles reviewed.

RESULTS

beta Blockers have been used to modify the severity of the hyperadrenergic symptoms of hyperthyroidism for the past 20 years. The clinical efficacy of these agents is affected by hyperthyroid-induced alterations in their gastrointestinal absorption, hepatic metabolism, and renal excretion. The mechanisms whereby these clinical changes are effected is unknown. The agents differ in their beta 1 cardioselectivity, membrane-stabilizing activity, intrinsic sympathomimetic activity, and lipid solubility. They do not appear to alter synthesis or secretion of thyroid hormone by the thyroid gland. Their effects on thyroxine metabolism are contradictory. Decreased thyroxine to triiodothyronine conversion is caused by some, but not all, beta blockers, and this appears to correlate with membrane-stabilizing activity. There does not appear to be any alteration in catecholamine sensitivity during beta-adrenergic blockade.

CONCLUSIONS

The principal mechanism of action of beta blockers in hyperthyroidism is to antagonize beta-receptor-mediated effects of catecholamines. beta Blockers are effective in treating hypermetabolic symptoms in a variety of hyperthyroid states. Used alone, they offer significant symptomatic relief. They are also useful adjuvants to antithyroid medications, surgery, and radioactive iodide treatment in patients with Graves' disease and toxic nodular goiters.

Thyroid emergencies

Thyroid storm is a rapid decompensation of severe hyperthyroidism which can best be described by the three criteria of hyperthermia, tachycardia and altered mental state with severe agitation. There has to be a precipitating factor such as infection, iodine contamination, surgery or even I-131 treatment. Severe hyperthyroidism not fulfilling the criteria of thyroid storm can also be an indication for emergency treatment, particularly in the elderly with heart disease. Suppressed serum TSH and elevated free T4 levels are essential to confirm the diagnosis. When rapidly available, radioiodine uptake of the thyroid can be useful. Therapy aims at rapidly reducing the active circulating hormone pool, hypermetabolic state, tachycardia, and finally hormone synthesis. Thyroid secretion can be blocked by ioipanoic acid or ipodate while hypermetabolic state can be reduced with beta-blockers or calcium channel-blockers. Treatment of hyperthyroidism in patients with iodine contamination is a real therapeutic challenge. Myxoedema coma, a complication of severe hypothyroidism, is defined by hypothermia (rectal temperature less than 36 degrees C), bradycardia, slow mentation, precipitating factor such as infection or drug overdose, and increased serum creatine phosphokinase levels. Diagnosis of severe hypothyroidism should be confirmed by serum measurements of TSH and free T4. Treatment consists of general supporting measures including rewarming, correction of serum electrolyte disturbances, and adequate alimentation. Thyroid hormone treatment should initially be aggressive using either 300-400 micrograms of T4 or 20-40 micrograms of T3 intravenously. Cortisone therapy may be added. Patients should be under close monitoring as arrhythmias and myocardial infarction are frequent complications of myxoedema coma and/or its treatment with thyroid hormones.

Endocrine emergencies in pregnancy

A number of endocrine conditions and emergencies have unique characteristics when present in the pregnant woman. Often the abnormal endocrine state affects both mother and fetus and the various diagnostic and therapeutic approaches have to be altered to avoid harming the fetus. Furthermore, the pregnant state itself may alter the natural course of the underlying endocrine condition. Prolactinomas may enlarge due to the hormonal milieu of pregnancy, causing mass effects and even apoplexy. Anticipation of this possibility and prompt recognition may prevent disastrous consequences. This stimulatory state may extend to the normal pituitary, resulting in Sheehan's syndrome. An acute form of Sheehan's may go unrecognized, leading to unnecessary maternal deaths. Autoimmune endocrine disorders may sometimes be exacerbated and at other times be ameliorated during pregnancy. Witness the development of lymphocytic hypophysitis during pregnancy, a condition best left alone if it can be diagnosed without surgery. Graves's disease usually improves during pregnancy but it may occasionally flare, resulting in potentially lethal thyroid storm. The various therapeutic alternatives for hyperthyroidism are very much affected by effects on the fetus. Cushing's syndrome has very bad consequences for the fetus and must be diagnosed and treated urgently, if not emergently. Phaeochromocytomas are always endocrine emergencies requiring urgent and sometimes emergent treatment. Hyperparathyroidism is usually mild, but severe hypercalcaemia can be a true endocrine emergency. Recognition of the interactions of these endocrine conditions and their specific treatments with the complicated maternal-fetal unit makes their diagnosis and treatment simultaneously both difficult and extremely rewarding.

Emergency department management of thyrotoxic crisis with esmolol

A previously healthy 26-year-old woman presented to the emergency department complaining of a severe, throbbing, and bifrontal headache. Initial vital signs were pulse rate, 130 beats/min; blood pressure, 128/50 mm Hg; temperature, 100.1 degrees F. Shortly thereafter the patient's pulse and temperature increased to 170 beats/min and 103 degrees F, respectively. Physical examination showed a tremulous, anxious woman in moderate distress who had a diffusely and symmetrically enlarged thyroid gland. A diagnosis of thyrotoxic crisis was made, and appropriate therapy instituted, including the use of an esmolol infusion for control of hypersympathetic activity. A review of the clinical presentation, diagnosis, and management of thyrotoxic crisis is presented.

Graves' disease. Current concepts

Graves' disease is an organ-specific autoimmune disorder. There is no universal agreement on the mechanism of Graves' disease, but the over-activity of the thyroid is due to an antibody capable of attaching to and activating the TSH receptor of follicular cells. There are other extrathyroidal features that are not caused either by this antibody or by hyperthyroidism. The clinical diagnosis is generally straightforward and can be confirmed by in vitro measurement of thyroid hormones and TSH. A measurement of radioiodine uptake is also valuable. Treatment is not specific for the immunologic defect, but its purpose is to lower the thyroid hormone levels to normal. This can be achieved with antithyroid medication, radioiodine iodine-131, or thyroidectomy. In most clinical situations, a strong argument can be made for iodine-131 therapy, which is safe and definitive, although posttreatment hypothyroidism and the need for lifelong thyroxine are to be expected.

Thyrotoxic crisis presenting as status epilepticus

A 30 year old male patient with thyrotoxic crisis presenting as status epilepticus is reported. The aetiology, manifestations and management of this medical emergency are discussed. The importance of prompt, vigorous and comprehensive treatment of thyrotoxic crisis is emphasized. Rapid control of hyperthyroidism as well as other supportive measures are essential if the high fatality rate is to be reduced. Comprehensive management reduces mortality from 90% to 20%.

Peri-operative management of severe thyrotoxicosis with esmolol

A case of severe thyrotoxicosis with cardiac decompensation is reported. Use of propranolol was followed by cardiovascular collapse. Esmolol, the beta-1 adrenoceptor blocking agent was successfully used to control the thyrotoxic state. A discussion of possible advantages of esmolol is provided.

[Postoperative thyrotoxic crisis during beta blockade: an atypical picture of generalized muscle deficiency]

The case is reported of a 42 year old female patient with Graves disease who presented with an atypical thyroid storm after subtotal thyroidectomy. Surgery was indicated because of poor patient compliance with the medical treatment, and its partial failure. High doses of propranolol (240 mg a day) were given for 5 days preoperatively. Anaesthesia and surgery were uneventful however, towards the end of the first postoperative day, a severe myopathic syndrome started, with neither fever nor tachycardia. Respiratory failure and pneumonia occurred 24 h later. This was deemed to be due to an atypical thyroid storm. The patient was intubated and ventilated, and treated with high doses of propranolol (320 mg a day). Muscle strength began returning to normal on the 4th postoperative day, being completely normal 2 months later. Even though a particularly severe form of thyrotoxic myopathy appeared to be the most likely cause of this temporary muscle disorder, beta-blockers may have been involved. Their potential role is discussed.

Current treatment of Graves' disease

In this review we have described the rationale for the appropriate treatment of patients with Graves' disease. Because the etiology of this disorder remains obscure, its management remains controversial. Since antithyroid drugs and radioiodine became readily available in the early 1950s, they have been widely used for the treatment of thyrotoxicosis, and the number of cases treated surgically has markedly decreased. However, almost four decades of experience have disclosed an unexpectedly high incidence of delayed hypothyroidism after radioiodine treatment and a low remission rate after antithyroid therapy. As a result, surgery is again being advocated as the treatment of choice. The three modalities of treatment have different advantages and disadvantages, and selection of treatment is of importance. In principle, we believe that for most patients a subtotal thyroidectomy should be performed after the patient has been rendered euthyroid by antithyroid drugs. We attempt to leave a thyroid remnant of 6 to 8 gm.

The selective beta 1-blocking agent metoprolol compared with antithyroid drug and thyroxine as preoperative treatment of patients with hyperthyroidism. Results from a prospective, randomized study

Despite the increasing use of beta-blocking agents alone as preoperative treatment of patients with hyperthyroidism, there are no controlled clinical studies in which this regimen has been compared with a more conventional preoperative treatment. Thirty patients with newly diagnosed and untreated hyperthyroidism were randomized to preoperative treatment with methimazole in combination with thyroxine (Group I) or the beta 1-blocking agent metoprolol (Group II). Metoprolol was used since it has been demonstrated that the beneficial effect of beta-blockade in hyperthyroidism is mainly due to beta 1-blockade. The preoperative, intraoperative, and postoperative courses in the two groups were compared, and patients were followed up for 1 year after thyroidectomy. At the time of diagnosis, serum concentration of triiodothyronine (T3) was 6.1 +/- 0.59 nmol/L in Group I and 5.7 +/- 0.66 nmol/L in Group II (reference interval 1.5-3.0 nmol/L). Clinical improvement during preoperative treatment was similar in the two groups of patients, but serum T3 was normalized only in Group I. The median length of preoperative treatment was 12 weeks in Group I and 5 weeks in Group II (p less than 0.01). There were no serious adverse effects of the drugs during preoperative preparation in either treatment group. Operating time, consistency and vascularity of the thyroid gland, and intraoperative blood loss were similar in the two groups. No anesthesiologic or cardiovascular complications occurred during operation in either group. One patient in Group I (7%) and three patients in Group II (20%) had clinical signs of hyperthyroid function during the first postoperative day. These symptoms were abolished by the administration of small doses of metoprolol, and no case of thyroid storm occurred. Postoperative hypocalcemia or recurrent laryngeal nerve paralysis did not occur in either group. During the first postoperative year, hypothyroidism developed in two patients in Group I (13%) and in six patients in Group II (40%). No patient had recurrent hyperthyroidism. The results suggest that metoprolol can be used as sole preoperative treatment of patients with hyperthyroidism without serious intra- or postoperative complications. Although the data indicate that the risk of postoperative hypothyroidism is higher after preoperative treatment with metoprolol than with an antithyroid drug, a longer follow-up period than 1 year is needed to draw conclusions regarding late results.

The effect of subtotal thyroidectomy with propranolol preparation on antibody activity in Graves' disease

The effect of subtotal thyroidectomy on thyroid stimulating antibodies (TSAb), thyrotrophin binding inhibitory immunoglobulins (TBII) and antimicrosomal antibodies (MsAb) was studied in 26 patients with Graves' hyperthyroidism treated pre-operatively with propranolol, but without antithyroid drugs. Following surgery, two patients relapsed in the first year and eight patients became hypothyroid. Eighteen patients (69%) had detectable TSAb at entry and no significant change in titre was seen during propranolol therapy. Following surgery TSAb levels fell within 24 h in eight patients, and at 6 weeks only seven patients had detectable TSAb. TSAb were still detectable in seven patients at 6 months. TSAb activity did not predict the late relapses. TBII were present in 13 patients (50%) before surgery and titres remained unchanged in all but two patients during the immediate postoperative period. At 6 weeks TBII had disappeared from the serum of only three patients. During the early post-operative period TBII became transiently detectable in five of the 13 patients initially TBII negative. The two patients who subsequently relapsed remained TBII positive throughout. Microsomal antibodies were present in the sera of 22 patients (85%). Surgery was followed by a decline in titre, which was substantial in only six of 13 patients studied in detail. Thus, in 92% patients hyperthyroidism was successfully eradicated. Propranolol treatment had no effect on antibody activity. TSAb and TBII disappeared from the circulation in 61% and 46% patients, respectively. These data are compatible with the concept that lymphocytes within the thyroid are the major site of TSAb production but other important sites for synthesis of thyroidal autoantibodies probably exist. Although outcome from surgery could not be accurately predicted from TSAb or TBII status either pre- or post-operatively, the two patients who relapsed had the most severe disturbances of thyroid autoimmunity; all patients in whom initially detectable TSAb or TBII disappeared remained in remission.

Surgery for thyroid disease

Thyroidectomy is the keystone of management in most patients with thyroid cancer, and has unique advantages in many cases of hyperthyroidism. The role of thyroidectomy in these two conditions is considered, with specific discussion of indications, extent of operation, complications, and technique.

Beta-adrenoceptor blockade and anaesthesia for thyroidectomy

The administration of beta-adrenoceptor blocking drugs in the pre-operative preparation and operative management of thyrotoxic patients undergoing subtotal thyroidectomy is reviewed. Particular reference is made to some of the recent advances and it is emphasised that there has been a considerable reduction in the incidence of problems following judicious use of these drugs. The choice of anaesthetic technique employed for thyroidectomy is less important than the degree of control of thyrotoxicosis by the beta-adrenoceptor blocking drug. Propranolol has proved safe and effective for the majority of patients. The longer acting agent nadolol is easier to administer, particularly in the peri-operative period. Patients are rendered less thyrotoxic and safety thereby enhanced by adding potassium iodide for 10 days preoperatively. The combination of nadolol and potassium iodide offers real advantages in the preparation of the thyrotoxic patient for surgery.

Radioiodine-induced thyroid storm. Case report and literature review

Thyroid storm developed following radioiodine therapy in a 43-year-old man with Graves' disease, weight loss, myopathy, severe thyrotoxic hypercalcemia, and a pituitary adenoma. The hypercalcemia may have been a significant, and previously unreported, predisposing factor for the radioiodine-associated thyroid storm. This case and 15 other well-documented cases of radioiodine-associated storm found in the literature are reviewed, as are several other cases of less severe exacerbations of thyrotoxicosis associated with radioiodine therapy. Although not often seen, these complications are often fatal. High-risk patients, such as the elderly, those with severe thyrotoxicosis, and those with significant underlying diseases, may benefit from preventive measures such as the judicious use of thyrostatic medications during the periods before and after isotope administration.

Propranolol and thyroidectomy in the treatment of thyrotoxicosis

For decades, the preparation of a hyperthyroid patient for surgery took several weeks or months utilizing thyroid blocking agents and iodine. In 1973, a preliminary report of 20 patients with hyperthyroidism treated with propranolol and thyroidectomy was presented. It was found that a thyrotoxic patient could be prepared for surgery, in an emergency, by intravenous propranolol in less than an hour, or electively by oral propranolol within 24 hours. Since then, 140 additional patients have been similarly treated. It continues to be true at this institution that propranolol, a beta-adrenergic blocking agent, effectively neutralizes the symptoms of autonomic hyperactivity, including sweating, tremor, fever, dilation of blood vessels, and increased pulse rate without significantly affecting thyroid function. An average dose of 160 mg/day was used, with a range of 40 to 320 mg/day. In none of these patients was iodine used; in fact, its use with propranolol is considered unnecessary. A subtotal, near total, or total thyroidectomy was done in all patients, resulting in a 55% incidence of hypothyroidism. There was no postoperative thyroid storm, nerve injury, or permanent hypoparathyroidism. It is believed that the administration of propranolol alone provides a rapid, safe, and effective preparation of the thyrotoxic patient for thyroidal or extrathyroidal surgical procedures during the perioperative period.

Pharmacokinetics of propranolol and sotalol in hyperthyroidism

The elimination and bioavailability of two beta-blocking agents, propranolol and sotalol, were studied in 10 thyrotoxic patients, both before and after treatment with iodine-131. Each subject received in random order propranolol 160 mg and sotalol 160 mg as single oral doses both while hyperthyroid and after euthyroidism had been achieved. The pharmacokinetics of sotalol was not affected by hyperthyroidism, whereas serum propranolol concentrations were significantly lower during hyperthyroidism than in the euthyroid state. During hyperthyroidism, the bioavailability of propranolol was significantly reduced (p less than 0.05) and its clearance was increased (p less than 0.005), whereas there was no difference in its serum t 1/2. This indicates that the bioavailability of propranolol in hyperthyroidism is reduced by a mechanism which may depend on increased first-pass metabolism in the liver, or on an increased distribution volume of the drug. Both propranolol and sotalol caused a slight decrease in serum tri-iodothyronine concentration. As the effects of beta-blocking agents on the symptoms of hyperthyroidism are correlated with the serum concentration of the drugs, sotalol, with its long half-life and unaltered elimination in hyperthyroidism, has certain advantages over propranolol in the treatment of thyrotoxicosis.

Propranolol in the surgical treatment of hyperthyroidism, including severely thyrotoxic patients

The perioperative course of 44 hyperthyroid patients prepared for surgery with propranolol alone, including 11 with severe thyrotoxicosis was compared to that of 20 euthyroid patients prepared for surgery with carbimazole. Conventional propranolol at a dosage of 160 mg/day was frequently insufficient to produce a high degree of beta-adrenergic blockade, particularly in severely thyrotoxic patients. A greater than 25 per cent reduction in sitting pulse rate was associated with a high degree of beta-blockade. The clinical course of patients with mild or moderate thyrotoxicosis was similar to that of the patients prepared with carbimazole. In contrast, the course of severely thyrotoxic patients was complicated and, in addition to a higher preoperative propranolol dosage, these patients commonly required supplemental propranolol after operation. Although thyroid crisis did not occur in any patient, we cannot recommend the use of propranolol alone for the severely thyrotoxic patient.

Childhood thyromegaly: recent developments

Evaluation of a child with goiter includes historical review, physical examination, and measurement of serum concentrations of PBI, T4 and T3RU, TSH, and titers of antithyroglobulin and antithyroid microsomal antibodies. If there are no indications for more intensive evaluation such as history of cervical irradiation, a palpable abnormality of the thyroid gland or unusual laboratory findings (e.g., a significant PBI-thyroxine iodine discrepancy in the absence of a positive antithyroid antibody titer), a trial of TSH-suppressive therapy with thyroxine is undertake, even if the cause of thyromegaly has not been identified. If thyroid size diminishes in the ensuing six to 12 months, treatment is maintained for approximately two years and then discontinued. If the goiter recurs, or if there is impaired thyroid function, treatment is resumed. Periodically, antithyroid antibody titers and indices of thyroid function are determined. If the goiter does not diminish after a reasonable trial of suppressive therapy with adequate amounts of thyroxine (i.e., those quantities which will inhibit TRH-induced secretion of TSH), subtotal thyroidectomy is recommended to be certain that an underlying neoplasm has not been overlooked. A biopsy of the thyroid is not performed routinely in such children prior to operative therapy. Almost invariably, examination of the surgical specimen reveals CLT. Postoperatively, suppressive doses of thyroxine are maintained indefinitely. Inasmuch as thyroxine suppression of TSH secretion is essential in the management of patients with thyroid neoplasms, a limited medical trial, as described, does not place the patient at undue risk.

Metabolic response to subtotal thyroidectomy in propranolol-treated thyrotoxic patients

Changes in plasma cortisol, glucose, cyclic AMP, blood leucocytes, pulse rate and body temperature were measured during and for 24 h after subtotal thyroidectomy in eight propranolol-treated (120-160 mg per day) mild to moderate thyrotoxic patients and eight patients with a non-toxic goitre. The results showed a similar metabolic response to surgery in the two groups without any trends towards a hypermetabolic response in the toxic group. The accumulating evidence of the safety of preoperative preparation with propranolol in patients with mild to moderate thyrotoxicosis is thus supported by our results.

Plasma propranolol steady state concentrations in thyroid disorders

Plasma propranolol steady-state concentrations (Css) were measured in 24 hyperthyroid and 6 hypothyroid patients before and after correction of the thyroid disorder. Following treatment of hyperthyroidism by surgery, antithyroid drugs or radioiodine, there was a significant rise in the plasma propranolol Css in patients receiving propranolol either 160 mg/day, 240 mg/day, or 480 mg/day. In addition, in five patients the area under the plasma propranolol concentration versus time curve during a dosing interval increased significantly from 405 ng/ml/h when hyperthyroid to 778 ng/ml/h when euthyroid. In the hypothyroid patients given propranolol 160 mg/day concomitantly with 1-thyroxine therapy the plasma propranolol Css fell significantly when euthyroid. There was a small but significant increase in the degree of plasma protein binding of propranolol, following treatment of hyperthyroidism and a significant decrease following correction of hypothyroidism. It is concluded that thyroid disorders markedly influence propranolol handling.

Preoperative endocrine and metabolic considerations

Patients with endocrine dysfunction have an increased risk of intraoperative and postoperative morbidity. Identification of such patients prior to surgery, and preoperative management to achieve normal hormonal status may prevent or lessen episodes of morbidity. Diabetics undergoing elective surgical procedures can be managed by any number of approaches. Whatever the method used, close monitoring of blood glucose levels is imperative.

Propranolol therapy in thyrotoxicosis. A review of 84 patients undergoing surgery

The effect of propranolol on the surgical course of 84 thyrotoxic patients undergoing partial thyroidectomy or extrathyroidal surgery was evaluated. Seventy-two patients (group 1) underwent surgery with propranolol as their sole preparatory medication, whereas in 12 (group 2) surgery was carried out after a rather prolonged period of thionamide preparation with the addition of propranolol preoperatively as an adjunctive therapeutic agent. Preoperative pulse rate and systolic blood pressure levels fell in both groups, and the clinical features of thyrotoxicosis were rapidly ameliorated with an average dose of propranolol of 330 mg (range 40 to 1,280 mg) daily. Maximal clinical response occurred within 48 to 72 hours of starting propranolol therapy. In 14 patients in group 1, paired serum calcium levels were reduced by the administration of propranolol preoperatively; serum thyroxine levels were unchanged. Serum thyroxine decay, evaluated postoperatively in the patients in group 1, was decreased. The half life of thyroxine was inversely related to the initial thyroxine levels. Analysis of these data indicates that the administration of propranolol alone provides rapid, safe and effective preparation of thyrotoxic patients for emergency or for elective thyroidal or extrathyroidal surgical procedures.

Reemergence of thyroidectomy as treatment for Graves' disease

Hyperthyroidism of Graves' disease may be treated very effectively by antithyroid pills, such as PTU and Tapazole, by radioactive iodine therapy, and by subtotal thyroidectomy. Each form of therapy has advantages and disadvantages, and thus treatment should be individualized. While therapy with radioactive iodine would appear to be ideal since it does not require an operation and is less expensive than surgical management, it suffers from a high rate of progressive hypothyroidism and from the fact that the time until a euthyroid state is obtained is often prolonged. In addition, the long-term carcinogenic risk of the therapy for thyroid neoplasia has never been completely defined since the data most often quoted have a mean follow-up time of only eight years. Furthermore, new "low-dose" radioiodine regimens may be more dangerous in this regard. Subtotal thyroidectomy, while not totally without complications, remains a rapid, safe, and effective treatment for Graves' disease. The careful use of propranolol has facilitated the preparation of some patients and has lessened the risk of operation. Thyroidectomy should remain the treatment of choice for young adults with this disease.