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Assessment of the Morbidity and Complications of Total Thyroidectomy
Neil Bhattacharyya, MD;
Marvin P. Fried, MD
Arch Otolaryngol Head Neck Surg. 2002;128:389-392.
ABSTRACT
| |
Objective To determine the incidence and predictive factors for complications
after total thyroidectomy.
Design Cross-sectional analysis of a national database on total thyroidectomy
cases.
Methods The National Hospital Data Survey database was examined and all cases
of total thyroidectomy performed during 1995 to 1999 were extracted. In addition
to demographic information, postoperative complications including hypocalcemia,
recurrent laryngeal nerve paralysis, wound complications, and medical morbidities
were identified. Statistical analysis was conducted to determine potential
predictive factors for postoperative complications.
Results A total of 517 patients were identified (mean age, 48.3 years). The
most common indications for total thyroidectomy were thyroid malignancy and
goiter (73.9% of cases). Eighty-one patients (15.7%) underwent an associated
nodal dissection along with total thyroidectomy, and 16 patients (3.1%) underwent
parathyroid reimplantation. The mean length of stay was 2.5 days (95% confidence
interval, 2.3-2.8 days). The incidence of postoperative wound hematoma was
1.0%, wound infection was 0.2%, and mortality rate was 0.2%. The incidence
of postoperative hypocalcemia was 6.2%. Younger age was statistically associated
with an increased incidence of hypocalcemia (P =
.002, t test), whereas sex (P
= .48), indication for surgery (P = .32), parathyroid
reimplantation (P>.99), and associated neck dissection
(P = .21) were not. The mean length of stay was 2.5
days and was unaffected by occurrence of postoperative hypocalcemia. The incidences
of unilateral and bilateral vocal cord paralyses were 0.77% and 0.39%, respectively.
Conclusions Postoperative hypocalcemia is the most common immediate surgical complication
of total thyroidectomy. Other complications, including recurrent laryngeal
nerve paralysis, can be expected at rates approximating 1%.
INTRODUCTION
NEOPLASTIC, inflammatory, and endocrine abnormalities of the thyroid
gland are extremely common, affecting approximately 11% of the general population.1 As such, surgery for thyroid gland abnormalities is
quite common, with an estimated surgical volume of more than 80 000 procedures
per year in the United States.2 Total thyroidectomy
is generally reserved for patients with thyroid malignancy, toxic thyroid
disease (thyrotoxicosis or toxic multinodular goiter), or clinically significant
goiter. Less commonly, it is performed for chronic thyroiditis or parathyroid
disease. In the setting of thyroid malignancy, total thyroidectomy may be
accompanied by a regional nodal dissection as clinically indicated. Despite
its frequency, total thyroidectomy remains a technically demanding procedure.
The focus of modern thyroidectomy centers on potential morbidity from
the procedure with emphasis on prevention of injury to closely investing structures
such as the recurrent laryngeal nerves and the parathyroid glands. As opposed
to unilateral thyroid lobectomy, total thyroidectomy carries potential risk
to all 4 parathyroid glands and both recurrent laryngeal nerves. Whereas parathyroid
injury during unilateral thyroid lobectomy is unlikely to result in hypocalcemia,
postoperative hypocalcemia is a significant risk after total thyroidectomy.
Similarly, although unilateral recurrent laryngeal nerve injury during thyroid
lobectomy may have a significant impact on voice quality, bilateral recurrent
laryngeal nerve injury during a total thyroidectomy has more serious airway
consequences. Therefore, it is essential to quantify the incidences of postoperative
hypoparathyroidism and recurrent laryngeal nerve injury, and to identify potential
predictive clinical factors for these morbidities. Such information is important
to properly counsel patients and determine preoperative risks for patients
considering total thyroidectomy. We sought to examine the modern incidence
of and potential risk factors for postoperative hypoparathyroidism and recurrent
laryngeal nerve injury after total thyroidectomy using a national database.
METHODS
The National Hospital Discharge Survey (NHDS) database for the calendar
years 1995 to1999 was examined, and the records of patients undergoing total
thyroidectomy as the primary surgical procedure (International
Classification of Diseases, Ninth Revision [ICD-9], procedure code
6.40) were extracted. These data were imported into a SPSS database (version
10.0, SPSS Inc, Chicago, Ill) for subsequent analysis. In addition to total
thyroidectomy, associated procedures such as lymph node dissection and parathyroid
reimplantation were identified using corresponding ICD-9 procedure codes.
For each case, presence or absence of individual surgical complications
including wound infection, postoperative hemorrhage, fistula formation, hypocalcemia,
and death was determined based on corresponding ICD-9
codes. In addition, analysis for medical complications including myocardial
infarction, stroke, and pneumonia was conducted. Descriptive statistics were
computed for the patient population under study including demographic variables,
indications for total thyroidectomy, complication rates, length of stay (LOS),
and disposition.3
 2 Analysis was conducted to determine if patient sex,
surgical indication for total thyroidectomy, or lymph node dissection (in
addition to the thyroidectomy or parathyroid reimplantation) had any influence
on the incidence of postoperative hypocalcemia. The t
test was used to determine if age impacted on incidence of postoperative hypocalcemia
and also to determine if the presence of postoperative hypocalcemia significantly
added to the LOS.
RESULTS
From 1995 to 1999, a total of 517 patients were identified with total
thyroidectomy as their primary procedure in the NHDS database. The mean patient
age was 48.3 years, and 81.8% of the patients were female. The indications
for surgery are listed in Table 1. The most common indications for surgery were thyroid malignancy and goiter,
together accounting for 73.9% of cases. Eighty-one patients (15.7%) underwent
an associated nodal dissection along with total thyroidectomy, and 16 patients
(3.1%) received parathyroid reimplantation. The mean LOS was 2.5 days (95%
confidence interval, 2.3-2.8 days). Medical morbidities were distinctly unusual,
with rates for myocardial infarction, stroke, and pneumonia determined at
0.2%, 0.6%, and 0.6%, respectively. Five patients (1.0%) encountered a postoperative
hematoma or hemorrhage, 1 patient (0.2%) experienced a postoperative wound
infection, and 1 patient died (mortality rate, 0.2%). Overall, 32 patients
(6.2%) were identified with postoperative hypocalcemia. None of the 3 patients
who underwent total thyroidectomy for parathyroid disorders had postoperative
hypocalcemia. Four patients (0.77%) were diagnosed as having an associated
unilateral vocal cord paralysis and 2 patients (0.39%) had bilateral vocal
cord paralysis.
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Table 1. Surgical Indications for Total Thyroidectomy
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Results of the statistical analysis examining for associations between
patient characteristics, surgical indications, and procedures performed are
displayed in Table 2. No statistically
significant associations between the occurrence of hypocalcemia and sex, indication
for surgery, presence of a nodal dissection, or parathyroid reimplantation
were identified. The mean age of patients with postoperative hypocalcemia
was 40.6 years, whereas the mean age for patients without hypocalcemia was
48.8 years (P = .002, t
test). Although LOS was slightly longer for patients with postoperative hypocalcemia
(mean LOS, 3.1 days) than those without (mean LOS, 2.5 days), this difference
was not statistically significant (P = .10, t test).
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Table 2. Incidence of Hypocalcemia According to Potential Predictive
Variables
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As a cross-check in the database, the diagnosis of hypocalcemia was
cross-validated with the diagnosis of hypoparathyroidism to determine accuracy
of coding within the database. Every patient who experienced postoperative
hypocalcemia was also designated as postoperative hypoparathyroidism, indicating
100% concordance.
COMMENT
The NHDS is an annual survey conducted by the National Center for Health
Care Statistics, which is a public agency charged with tracking health care
utilization on a yearly basis across the United States. From the aggregate
group of all US hospitals, representative institutions are randomly selected
to provide data for the NHDS. A sample of discharge records from this national
sample of nonfederal hospitals from all 50 states and the District of Columbia
are reviewed; trained staff members collect data both manually and electronically.
Community hospitals, teaching hospitals, and tertiary care centers are all
sampled. This data set has been frequently used to determine benchmarks for
incidence of disease, rates of surgery, and annual trends. In addition, it
has been used to investigate mortality and morbidity in both surgical and
medical patient populations.4-7
The NHDS data have been previously used to determine the incidence of
various procedures, the prevalence of disease, and year to year trends in
surgery.4 We have previously reported on the
use of this database for assessing mortality, morbidity, and LOS for head
and neck surgical procedures.3 In general,
NHDS data are believed to accurately reflect disease and surgical mortality,
but less accurately reflect morbidity.6 The
NHDS data collection system consists of a random sampling of these institutions,
carefully chosen to represent an accurate cross section of medical practice
in United States. Therefore, treatment biases, selection biases, and institutional
biases are less likely to play a role.3 The
NHDS data extracted in this study differ significantly from the patient populations
in most of the head and neck surgical literature because almost all previously
published literature reflects experiences from single academic institutions.
This introduces an inherent bias, since teaching hospitals have a well-documented
lower mortality rate and different patient populations than community hospitals.8
Several authors have reported on institutional series of thyroid surgery
for benign and malignant disease. However, to accrue significant surgical
case volumes with which to study incidence and trends, the majority of the
studies have been retrospective, encompassing 10- to 20-year periods at a
single institution. This makes a true assessment of these incidences somewhat
difficult because of variabilities in surgical technique, accuracy of medical
records, and other factors that may change over time. Furthermore, many of
these series include several different procedures including total thyroidectomy,
subtotal thyroidectomy, completion thyroidectomy, and even unilateral thyroid
lobectomy. One reason for analyzing the NHDS database was to study a large
volume of procedures occurring in a short period without institutional biases.
Postoperative hypocalcemia after total thyroidectomy has been reported
to range from 1% to 40%.9-13
Recently, Sasson and associates14 reported
on a 9-year series of 141 thyroidectomies (69 total thyroidectomies). Not
unexpectedly, total thyroidectomy was strongly associated with postoperative
hypocalcemia (incidence, 13%) when compared with other forms of thyroid surgery.
Interestingly, unintentional parathyroidectomy was not associated with an
increased risk of postoperative hypocalcemia.14
Many of the published series regarding the incidence of hypocalcemia after
thyroidectomy include several different procedures aggregating unilateral
lobectomy, subtotal thyroidectomy, and total thyroidectomy. Careful review
of each study is necessary to determine the incidence of hypocalcemia in the
total thyroidectomy subgroups.11, 14-15
Calculation of hypocalcemia rates, while including the unilateral thyroidectomies
in the denominator, will tend to underestimate its overall incidence.
Controversy still exists regarding factors that are associated with
postoperative hypocalcemia. Overall, the pathogenesis of postoperative hypoparathyroidism
is likely to be multifactorial.16 Although
patients with nodal dissection were almost twice as likely to manifest postoperative
hypocalcemia, we did not find this association to be statistically significant.
Other investigators have found neck dissection to be associated with higher
incidences of both temporary and permanent hypoparathyroidism, and cite this
risk as an argument against prophylactic neck dissection.11, 17
As neck dissection may contribute to postoperative hypoparathyroidism via
devascularization or other surgical trauma, it should be reserved for cases
with clinically evident nodal disease.
Similarly, while some authors have identified parathyroid reimplantation
as a risk factor for postoperative hypocalcemia, other authors have not found
this to be the case.14, 18 We failed
to find an association between parathyroid reimplantation and the presence
or absence of postoperative hypoparathyroidism. Therefore, it seems that parathyroid
reimplantation neither protects against postoperative hypocalcemia nor predisposes
to it. The decision to reimplant should be based on clinical factors at the
time of surgery, retaining the parathyroid glands in situ whenever possible.19
We were somewhat surprised that the indication for total thyroidectomy
was not found to influence the rate of hypocalcemia. Other smaller series
have found that total thyroidectomy for malignancy is associated with higher
rates of postoperative hypocalcemia.14 However,
many of these studies include both hemithyroidectomy and total thyroidectomy
in their patient populations, or they group patients differently.11 As patients with malignancy are more likely to also
undergo total thyroidectomy, the true variable predicting hypocalcemia may
be in fact the extent of surgery. Although mean LOS was slightly higher for
patients with postoperative hypocalcemia than for those without, this difference
was not statistically significant. This suggests that corrective measures
for early postoperative hypocalcemia are able to rapidly correct serum values
or that other factors (such as suction drain output) more strongly influence
LOS.11, 20 Since postoperative
hypocalcemia generally manifests within 24 hours of surgery, delay in the
diagnosis of postoperative hypoparathyroidism does not tend to contribute
to an increased LOS.
Published rates of recurrent laryngeal nerve injury vary widely in the
literature. This is likely due to differences in definition of palsy, diagnostic
biases, and reporting biases. However, it is generally believed that recurrent
laryngeal nerve injury, either temporary or permanent, is likely to occur
in approximately 1% of unilateral lobectomy cases and 2% to 3% of total thyroidectomy
cases.11, 15 Total thyroidectomy
carries an increased risk for recurrent laryngeal nerve palsy, not only because
both recurrent laryngeal nerves are placed at risk, but also likely because
patients undergoing total thyroidectomy often have more advanced disease.
In this series, the rates of unilateral and bilateral vocal cord paralysis
were too small to undergo meaningful statistical analysis for predictive factors.
Our data clearly indicate that total thyroidectomy is a safe procedure,
with an expected mortality rate of only 0.2%. Medical complications such as
myocardial infarction, stroke, and postoperative pneumonia are quite rare.
Similarly, rates for local wound complications such as postoperative hematoma
and wound infection are distinctly low. The identified morbidity and mortality
rates for total thyroidectomy compare favorably with other series that include
both unilateral and bilateral surgery.11 These
relatively rare morbidities should not deter surgeons from performing total
thyroidectomy when appropriate for the patient's level of disease.
Although analysis of the large randomly sampled national database such
as the NHDS data set has distinct advantages in diminishing selection biases
and reporting biases, there are several limitations in its use for the present
analysis. Because the analysis is essentially retrospective, it is difficult
to assess causality. Rather, we are able to compute the incidence of selected
complications and identify associations between these postoperative complications
and clinical factors. For example, it is possible that some patients may have
had preoperative unilateral vocal cord paralysis, and therefore it would be
inaccurate to list such patients as having had recurrent laryngeal nerve injury
after total thyroidectomy. However, detailed review of the data indicates
that 3 of the 4 patients with unilateral vocal cord paralysis underwent total
thyroidectomy for benign disease. As these patients would be unlikely to have
preoperative paralysis, it is fair to conclude that the vocal cord paralysis
resulted from total thyroidectomy. Similarly, both patients with bilateral
vocal cord paralysis underwent surgery for benign disease (goiter), and would
be unlikely to have had preoperative bilateral vocal cord paralysis.
Also, the current methodology will fail to capture patients whose complications
were not diagnosed during their inpatient stay, but were subsequently diagnosed
in the outpatient setting.3 Given that the
mean LOS approached 2.5 days, we would expect that most cases of postoperative
hypoparathyroidism would be captured, since greater than 94% of cases of hypocalcemia
manifest within 24 hours after total thyroidectomy.20
It is also possible that some surgeons may have administered oral calcium
as part of routine postoperative management. This may mask the immediate onset
of postoperative hypocalcemia, tending to deflate the overall incidence of
immediately diagnosed postoperative hypoparathyroidism. In addition, it is
possible that some patients experienced postoperative recurrent laryngeal
nerve paralysis, but the diagnosis was not confirmed until postoperative follow-up
evaluation in the outpatient setting. The best determination of the true incidence
of postoperative recurrent laryngeal nerve paralysis would be obtained by
examining all patients before and after thyroidectomy with laryngoscopy with
electromyographic confirmation of selected cases. Understanding these limitations,
our data can be interpreted as minimum values for recurrent laryngeal nerve
complications in the total thyroidectomy setting since initially undetected
cases may be subsequently diagnosed on an outpatient basis.
CONCLUSIONS
Despite the fact that total thyroidectomy is a more involved procedure
that exposes more parathyroid glands and recurrent laryngeal nerves to surgical
risk than unilateral thyroid lobectomy, it is an inherently safe procedure.
Local complications such as recurrent laryngeal nerve paralysis and wound
complications can be expected to occur at rates near 1%, while postoperative
hypoparathyroidism may occur in approximately 6% of cases. Neither nodal dissection
nor parathyroid reimplantation seems to affect the risk of postoperative hypocalcemia.
Since few modifiable factors can be identified that predict increased surgical
risk for these complications, the extent of thyroidectomy surgery should be
based on patient preferences, the experience of the operating surgeon, and
the overall clinical setting.
AUTHOR INFORMATION
Accepted for publiction October 2, 2001.
Corresponding author: Neil Bhattacharyya, MD, Division of Otolaryngology,
333 Longwood Ave, Boston, MA 02115.
From the Department of Otology and Laryngology, Harvard Medical School,
and the Division of Otolaryngology, Brigham and Women's Hospital, Boston,
Mass (Dr Bhattacharyya); and the Department of Otolaryngology, Montefiore
Medical Center, Bronx, NY (Dr Fried).
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