Transcript Perioperative management of patients with hypothyroidism

Perioperative
management of patients
with hypothyroidism
H.Rezvanian MD
Introduction
 Thyroid hormones have a wide variety of actions in
virtually every organ system. They play a crucial role in
regulating important functions such as cardiac
contractility, vascular tone, water and electrolyte
balance, and normal function of the central nervous
system. It is now widely accepted that an euthyroid
state marked by adequate levels of thyroid hormones
is necessary to obtain the best possible results from
any kind of surgical intervention.
Effects of hypothyroidism on the
cardiovascular system
 the most important adverse effects of hypothyroidism
that may predict a bad surgical outcome are those
affecting cardiac function.
 decreased cardiac output, increased peripheral
vascular resistance, and decreased blood volume.
 These changes may be particularly important for the
surgical patient with some degree of preexisting heart
failure.
Surgical outcomes
 There are no randomized studies looking at surgical
outcomes in hypothyroid versus euthyroid patients
 Two retrospective cohort studies examined peri- and
postsurgical outcomes in moderately hypothyroid
patients.
 The authors concluded that there was no evidence to
justify deferring needed surgery in patients with mild
to moderate hypothyroidism
Management
 management is to base therapeutic decisions on the
severity of hypothyroidism.
 definitions of mild, moderate, and severe
hypothyroidism can be vague
 A useful definition of severe hypothyroidism includes
patients with myxedema coma, with severe clinical
symptoms of chronic hypothyroidism such as altered
mentation, pericardial effusion, or heart failure, or
those with very low levels of total thyroxine (eg, less
than 1.0 mcg/dL) or free thyroxine (eg, less than 0.5
ng/dL)
Moderate Hypothyroidism
 All other patients with overt hypothyroidism
(elevated serum TSH, low free thyroxine) can
be treated as having moderate disease.
 Subclinical hypothyroidism is defined
biochemically as a normal serum free thyroxine
(T4) concentration in the presence of an
elevated serum thyrotropin (TSH)
concentration and this is, by definition, mild
disease.
Subclinical hypothyroidism
we suggest not postponing
surgery in patients with
subclinical hypothyroidism
(elevated serum TSH, normal
free T4).
Moderate (overt) hypothyroidism
 we suggest that patients with moderate
overt hypothyroidism undergo urgent or
emergent surgery without delay, with the
knowledge that minor perioperative
complications might develop.
 postpone surgery until the euthyroid
state in a patient being evaluated for
elective surgery.
Euthyroidism in Moderate
(overt) hypothyroidism

young patients are started on close to
full replacement doses of thyroxine
(T4, 1.6 mcg/kg), while elderly patients
or patients with cardiopulmonary
disease are started on 25 to 50 mcg
daily with an increase in dose every
two to six weeks
Severe hypothyroidism
 these patients should be considered high
risk and surgery should be delayed until
hypothyroidism has been treated.
 If emergency surgery must be performed
in a patient with severe hypothyroidism and
there is concern about existing or
precipitating myxedema coma,should be
rapidly normalized thyroid function.
Euthyroidism in Severe
hypothyroidism
patients should be treated with both T3
and T4 to rapidly normalize thyroid
function. As an example, T4 is given in a
loading dose of 200 to 300 mcg IV
followed by 50 mcg daily. T3 is given
simultaneously in a dose of 5 to 20 mcg IV
followed by 2.5 to 10 mcg every eight
hours depending upon the patient's age
and coexistent cardiac risk factors.
Angina
Angina is not an absolute contraindication to
thyroid hormone replacement if the patient
has symptomatic hypothyroidism. Some
patients will experience improvement in
their angina symptoms with therapy.
Presently, most patients with angina have
coronary artery revascularization first and T4
is prescribed afterwards .
PTCA or CABG
 There were no differences between the
euthyroid and hypothyroid patients
undergoing PTCA
 Those having CABG had a higher incidence of
heart failure, hyponatremia, gastrointestinal
dysfunction, and fever.
 if hypothyroid patients need a
revascularization procedure, PTCA may be a
better choice if there is no time to render them
euthyroid.
IS PREOPERATIVE MEASUREMENT
OF TSH NECESSARY?
Despite the relatively high prevalence of
thyroid disease in the general population,
we believe there is no need to screen for
thyroid disease during the preoperative
medical consultation.
if the history and physical examination are
suggestive of thyroid disease, it is
reasonable to try to make the diagnosis
Perioperative management of
patients with hyperthyroidism
with
HYPERTHYROIDISM
 hyperthyroidism affects many bodily systems
that might influence perioperative outcome.
Patients with hyperthyroidism have an increase
in cardiac output, due both to increased
peripheral oxygen needs and increased cardiac
contractility. Heart rate is increased, pulse
pressure is widened, and peripheral vascular
resistance is decreased.
HYPERTHYROIDISM
 Atrial fibrillation occurs in about 8 percent of patients
with hyperthyroidism and is more common in elderly
patients. Dyspnea may occur for a variety of reasons,
including increased oxygen consumption and CO2
production, respiratory weakness, and decreased lung
volume.
 Weight loss is due primarily to increased calorigenesis,
and secondarily to increased gut motility and the
associated hyperdefecation and malabsorption; these
changes can cause the patient to be malnourished.
Management
 In patients with untreated or poorly controlled
hyperthyroidism, an acute event such as
surgery can precipitate thyroid storm, a
potentially life-threatening condition. Thus, all
elective surgeries should be postponed in
patients with newly discovered overt
hyperthyroidism until the patient has achieved
adequate control of their thyroid condition
(usually three to eight weeks).
subclinical hyperthyroidism
patients with subclinical hyperthyroidism
(low TSH, normal free T4 and T3) can
typically proceed with elective surgeries.
Unless contraindicated, we typically
administer a beta blocker preoperatively
to older patients (>50 years) or younger
patients with cardiovascular disease, and
taper after recovery.
Preoperative preparation for urgent
surgery
Such patients require preoperative
preparation, typically with beta blockers
and thionamides. If hyperthyroidism is
severe and the need for surgery is urgent,
we also add SSKI one to five drops three
times daily) one hour after thionamides.
Preoperative preparation for urgent
surgery
Extreme caution is necessary before
administering SSKI to a patient with
known or suspected toxic nodular goiter
since iodine, in the absence of a
thionamide to block organification, may
exacerbate the hyperthyroidism.
Urgent surgery
Patients with toxic nodular
goiter who are intolerant or
unable to take thionamides
should be pretreated with
beta blockers alone
urgent surgery
In contrast, in patients with Graves'
disease, exogenous iodine is unlikely to
exacerbate hyperthyroidism by acting as
substrate. Thus, for patients with Graves’
hyperthyroidism who are allergic to or are
intolerant of thionamides, the
combination of beta blockers and iodine
can be used for preoperative preparation
Beta blockers
beta blockers administered preoperatively
effectively control the clinical
manifestations of hyperthyroidism and
are as effective as a thionamide for
preoperative preparation of the
hyperthyroid patient
Beta blockers
The longer acting beta blockers are preferred in
patients who are candidates for therapy because
an oral dose taken one hour before surgery will
usually maintain adequate beta blockade until
the patient is able to take oral medications
postoperatively .
Beta blockers
Patients with relative
contraindications to beta
blockade may better tolerate
beta 1-selective agents, such as
metoprolol
Thionamides
 Thionamides block de novo thyroid hormone synthesis
but have no effect upon the release of preformed
hormone from the thyroid gland, and will therefore
not have a significant effect on thyroid hormone levels
over only a few preoperative days. Nevertheless, once
the diagnosis of hyperthyroidism is established,
thionamides should be initiated with the aim of
controlling hyperthyroidism in the postoperative
period.
Thionamides
 Methimazol 10 mg two to three times
daily or 20 to 30 mg once daily) is usually
preferred to PTU except during
pregnancy, because of its longer
duration of action (allowing for single
daily dosing) and a lesser degree of
toxicity.
IODINE
Iodine blocks release of T4 and T3
from the gland and thereby
shortens the time to achieving a
euthyroid state. we suggest adding
iodine.
Thyroid storm
The therapeutic options for thyroid storm
are essentially the same as those for
uncomplicated hyperthyroidism, except
that the drugs are given in higher doses
and more frequently. In addition,
infection needs to be identified and
treated, and hyperpyrexia should be
aggressively corrected.
Thyroid storm
 Acetaminophen is preferable to aspirin, which
can increase serum free T4 and T3
concentrations by interfering with protein
binding. Cooling blankets can be used if
hyperthermia develops during surgery. Full
support of the patient in an intensive care unit
is essential, since the mortality rate of thyroid
storm is substantial