From the Standpoint of an Institutional Review Board Research Would Include ____
J Gen Intern Med. 1998 Jan; 13(1): 24–31.
Risks of Complication Following Thyroidectomy
Mark R Burge
1Department of Medicine, University of New Mexico School of Medicine, Albuquerque, NM.
Tanja-Maria Zeise
1Department of Medicine, University of New Mexico Schoolhouse of Medicine, Albuquerque, NM.
Michael Westward Johnsen
aneDepartment of Medicine, Academy of New Mexico School of Medicine, Albuquerque, NM.
Martin J Conway
2Lovelace Scientific Resources, Albuquerque, NM
Clifford R Qualls
iiiUniversity of New Mexico Full general Clinical Inquiry Eye, Computerized Database Management and Assay Systems, Albuquerque, NM.
Abstract
OBJECTIVE
Because hypoparathyroidism is a serious complication of thyroidectomy, we attempted to elucidate factors determining the risk of this postoperative outcome.
SETTING
Four third intendance hospitals in Albuquerque, New Mexico.
PATIENTS
A retrospective study of 142 patients who underwent total or subtotal thyroidectomy between 1988 and 1995.
MEASUREMENTS AND MAIN RESULTS
Permanent hypoparathyroidism was defined as hypocalcemic symptoms plus a requirement for oral vitamin D or calcium half dozen months subsequently thyroidectomy. Factors analyzed to make up one's mind their contribution to the risk of persistent postoperative hypoparathyroidism were the indication for thyroidectomy, performance of a preoperative thyroid needle biopsy, blazon of surgery, postoperative pathology, presence and phase of thyroid carcinoma, resident surgeon involvement, and specialty of the surgeon performing the process. Surgical specialty and stage of thyroid carcinoma were independent hazard factors for persistent postoperative hypoparathyroidism past multivariate analysis. Nine (29%) of 31 patients who had thyroidectomy by otolaryngologists met criteria for permanent hypoparathyroidism, and six (5%) of 111 patients who had thyroidectomy past general surgeons met the same criteria (p < .001). Adjustment for the effect of stage did not eliminate the effect of specialty (p=.006), and adjustment for the effect of specialty did not eliminate the upshot of stage (p=.02), on the occurrence of postoperative hypoparathyroidism.
CONCLUSIONS
We conclude from our data that patients undergoing thyroidectomy by an otolaryngologist may be at a college take chances of permanent postoperative hypoparathyroidism than patients who undergo thyroidectomy past a full general surgeon. This may reflect differences in case selection or surgical arroyo or both.
Keywords: thyroidectomy, surgical complications, hypoparathyroidism, hypocalcemia, thyroid carcinoma
Chronic hypoparathyroidism is a serious and potentially debilitating disorder that results from a variety of causes. It most commonly occurs as a complication of thyroid surgery, with incidence rates of postthyroidectomy hypoparathyroidism ranging from 0% to 33% depending on the severity of the underlying affliction and the extent of the operative process. one,two,3,iv,1–5 Persistent postoperative hypoparathyroidism normally results from intentional or inadvertent extirpation of the parathyroid glands during thyroidectomy or from interruption of the blood supply to the glands with subsequent infarction. 6 Signs and symptoms of the ensuing hypocalcemia include perioral or distal extremity paresthesia, muscle cramping, positive Trousseau and Chvostek signs, laryngeal stridor, and convulsions. The latter conditions may prove fatal. The long-term sequellae of untreated or inadequately treated hypoparathyroidism include premature cataract development, calcification of the basal ganglia, recurrent seizures, osteomalacia, and psychiatric symptomatology. 7,8,7–nine Clinical management of these patients is costly and can be challenging because the therapeutic window for vitamin D (ofttimes a required component of therapy) is narrow. Even short-term vitamin D intoxication, which may be asymptomatic, can crusade nephrolithiasis and obstructive uropathy, resulting in permanent kidney harm. 6
Laryngeal nervus injury is another potentially serious complication of thyroidectomy. Permanent unilateral recurrent laryngeal nerve (RLN) paralysis manifests clinically as hoarseness, weakness, and breathiness of the vocalisation and occurs with an incidence between 0% and 3.six% after thyroidectomy. 3, x, xi
Traditionally, thyroidectomies have been performed past both full general surgeons and otolaryngologists (ear, nose, and throat [ENT] surgeons). Comparison of different medical and surgical specialties with respect to outcome parameters is currently the subject of intensive investigation and is beginning to impact the delivery of health care in the United States. 2,three,4,5,6,7,8,9,one,2,12–23 Although such studies are oftentimes controversial, they take the potential to do good patients, payers, and physicians alike. Moreover, studies of surgical consequence are of practical business to primary intendance providers who may alter their referral patterns on the basis of a proven difference in outcome between two surgical specialties.
Because permanent hypoparathyroidism is a clinically significant complication of thyroidectomy, we attempted to identify those factors that determine the risk of this postoperative complication and other result parameters. These retrospective data suggest that the pick of surgical specialty and the stage of thyroid carcinoma are independent take chances factors for persistent postoperative hypoparathyroidism. Other factors were considered as potential confounding variables.
METHODS
To assess the rate of development of persistent postoperative hypoparathyroidism amidst patients receiving thyroidectomy in a large southwestern community, a retrospective chart review was performed of patients who underwent full or subtotal thyroidectomy between 1988 and 1995 at four tertiary care hospitals in Albuquerque, New Mexico (University of New United mexican states Health Sciences Centre, Albuquerque Veterans Administration Medical Heart, Lovelace Medical Center, and Presbyterian Medical Eye). This retrospective report received exemption from regulations pertaining to human study by the Institutional Review Board of each hospital. Candidates for study inclusion were identified by querying preexisting databases from each hospital for all thyroidectomies performed during the preceding 6 years. From these, 142 cases of total or subtotal thyroidectomy were identified that included adequate postoperative follow-up data. Data from 438 patients were excluded from assay for the post-obit reasons: 377 patients received only fractional thyroidectomy, 9 patients underwent intentional parathyroidectomy as a component of surgery, 9 patients had incomplete or missing hospital records, and 43 patients' charts lacked adequate postoperative follow-upwards data.
Information gathered from patient charts included age at time of operation, gender, ethnicity, the indication for thyroidectomy, preoperative and postoperative total serum calcium concentrations, the type of surgery performed (i.east., subtotal, total, or total thyroidectomy with lymph node dissection), the postoperative diagnosis as taken from the postoperative pathology report, and the postoperative clinical status of those patients with carcinoma of the thyroid (i.due east., credible cure, persistent or recurrent affliction in the neck or distant metastases). Permanent hypoparathyroidism was divers equally the postoperative development of hypocalcemic symptoms plus a requirement for oral vitamin D or supplemental calcium therapy 6 months after surgery. Patients were designated to take transient hypoparathyroidism if symptoms of hypocalcemia developed within the first 2 weeks after thyroidectomy but resolved without the need for specific therapy within 6 months. The presence of postoperative RLN injury was besides noted.
Epithelial carcinoma of the thyroid was staged co-ordinate to the method of Mazzaferri practical to the postoperative pathology study. 24 Phase I tumors were less than 1.v cm in diameter or restricted to ane lobe of the thyroid and were free of local invasion or afar metastases. Stage Two tumors were one.five to 4.4 cm in diameter or involved both lobes of the thyroid and were free of local invasion or distant metastases. Phase III tumors were larger than four.4 cm in diameter or exhibited invasion of local structures in the neck. Stage IV tumors were any tumors that demonstrated distant metastases. Considering just one stage IV tumor was identified in this report, stages Iii and IV were grouped for the purposes of statistical analysis. For analysis of the outcome of thyroid cancer staging, all surgeries performed for reasons other than thyroid cancer were assigned a stage of zero.
In an endeavour to characterize further factors that may affect the incidence of persistent postthyroidectomy hypoparathyroidism, data for a number of other variables were collected and analyzed. Comparison of the indication for surgery was complicated by the inconsistent performance of preoperative thyroid biopsies in patients with thyroid nodules. Patients who underwent preoperative thyroid biopsy often carried a diagnosis of thyroid carcinoma as the indication for surgery, while those who did non undergo a preoperative thyroid biopsy carried a diagnosis of thyroid nodule or mass as the indication for surgery. For the purposes of analysis, the indications for surgery were based on the preoperative fine needle biopsy, if any, and were grouped as follows: no thyroid carcinoma, thyroid mass without preoperative fine needle biopsy, thyroid mass with indeterminate fine needle biopsy, thyroid mass suspicious for carcinoma by fine needle biopsy, or thyroid carcinoma. In addition, the potential relation of preoperative fine needle biopsy to the development of persistent postoperative hypoparathyroidism was explored and analyzed. For the analysis of ethnicity as a possible predictive factor for the evolution of persistent postoperative hypoparathyroidism, patients were grouped as Hispanic, not-Hispanic Caucasian, or other ethnicity. The presence of resident physicians during the operative process was too noted. The prospective decision to include subtotal equally well equally total thyroidectomies in the analysis derives from the fact that persistent postoperative hypoparathyroidism has been reported to occur in up to four% of patients afterwards subtotal thyroidectomy. 25
For the purposes of data analysis, postoperative hypoparathyroidism or song string paralysis were treated as outcomes, and other factors (such every bit postoperative diagnosis) were treated as grouping variables. Univariate analyses were performed using Wilcoxon's Exact Test for variables with ordered categories (such as cancer phase) and Fisher's Exact Exam for binary variables. Continuous variables were compared using the unpaired Educatee's t exam. Multivariate assay was performed using stepwise logistic regression to determine relations to independent variables and the effects of misreckoning variables using SAS software. (PROC GENMOD and the Logistics Procedure, SAS/STAT Software: Changes and Enhancements Through Version half-dozen.12, SAS Institute, Cary, NC). Results of the univariate analyses are presented first, followed by the multivariate logistic regression and the results of subanalyses and test of potentially confounding factors. A generalized estimating equation model with Logit link function and the usual compound symmetry correlation construction was employed to appraise for the potentially confounding effects of clustering within specific surgeons. Finally, adjusted odds ratios with 95% confidence intervals are provided for both the full logistic regression (including all variables) and for the best model (including only those factors identified as contained variables).
RESULTS
Study Subjects
Demographic and descriptive characteristics of the 142 qualifying patients who underwent full or subtotal thyroidectomy during the study menstruum are summarized in Tabular array 1
Table 1
Demographic and Operative Characteristics of Patients Undergoing Total or Subtotal Thyroidectomy in Albuquerque, NM; 1988–1995
Univariate Analyses
The following factors were found to be predictors of persistent postoperative hypoparathyroidism on the basis of univariate assay: the presence of thyroid carcinoma (p= .01), stage of thyroid carcinoma (p= .008), and surgical specialty (p < .001). The following factors were non found to be predictive of this postoperative complexity: age (p= .95), gender (p= i.0), ethnicity (p= .09), performance of a preoperative fine needle biopsy of the thyroid (p= .62), indication for thyroidectomy (p= .79), the type of surgery performed (p= .42) , or resident physician involvement in the thyroidectomy (p= .71). Information used for the univariate analyses are shown in Table 2
Table ii
Data for Univariate Analyses
Nine (29%) of 31 patients who had thyroidectomy past an otolaryngologist met criteria for permanent hypoparathyroidism, while 6 (5%) of 111 patients who underwent thyroidectomy performed by a general surgeon met the same criteria (Fig. 1;p < .001). Ten surgeons performed the 31 thyroidectomies in the ENT group, and 7 different surgeons were involved in the ix cases of permanent hypoparathyroidism observed in this group. In the general surgery group, 27 surgeons performed the 111 thyroidectomies, and 3 surgeons were involved in the 6 cases of permanent hypoparathyroidism observed in this group. Ane general surgeon was associated with 4 cases of postoperative hypoparathyroidism in a full of 35 thyroidectomies.
Postoperative parathyroid status according to surgical specialty among 142 patients receiving thyroidectomy in Albuquerque, NM, betwixt 1988 and 1 995. The occurrence of permanent postoperative hypoparathyroidism is increased in the ENT group by Fisher's Verbal Exam.
Multivariate Logistic Regression
Stepwise logistic regression for multivariate analysis identified surgical specialty and phase of thyroid carcinoma as the only independent predictors for the development of persistent postoperative hypoparathyroidism. Moreover, the outcome of each of these factors persisted when the model was adapted to account for the other: when adapted for the effect of thyroid cancer staging, the effect of surgical specialty remained significant (p= .006), and when adjusted for the effect of surgical specialty, the event of stage also remained pregnant (p= .02). Results of the multivariate logistic regression are shown in Table 3
Table StepwiseLogistic Regression for Multivariate Analysis of Factors Potentially Related to the Development of Persistent Post-Thyroidectomy Hypoparathyroidism
Subanalyses and Evaluation of Potentially Confounding Factors
Indication for Surgery and Postoperative Diagnosis.
Univariate analysis of the indication for surgery as adamant by preoperative thyroid biopsy, if any, revealed a p value of .06 for a deviation between surgical groups past Fisher'south Exact Examination. Analysis of the postoperative diagnosis, every bit taken from the postoperative pathology report, revealed that 28 (90%) of the 31 patients who received thyroidectomy by an ENT surgeon had a diagnosis of thyroid cancer, compared with 76 (68%) of the 111 patients who received thyroidectomy past a full general surgeon (p=.02 by Fisher'due south Exact Test). Postoperative diagnoses co-ordinate to surgical specialty are summarized in Table 4 All cases of persistent postoperative hypoparathyroidism occurred in patients with thyroid cancer in this report.
Table 4
Postoperative Diagnosis Following Thyroidectomy Co-ordinate to Surgical Specialty
Type of Surgery.
Of the 31 thyroidectomies performed by ENT surgeons, 8 (26%) were performed as full thyroidectomies with neck dissection, 21 (68%) were performed every bit total thyroidectomies, and ii (6%) as subtotal thyroidectomies. Of the 111 thyroidectomies performed by full general surgeons, 8 (7%) were total thyroidectomies with neck autopsy, 73 (66%) were total thyroidectomies, and xxx (27%) were subtotal thyroidectomies. Verbal Wilcoxon testing revealed a significant departure in the type of surgery performed between the two surgical groups (p= .002). When subtotal thyroidectomies were removed from the analysis, nonetheless, a pregnant difference persisted for the development of permanent postthyroidectomy hypoparathyroidism between the two surgical groups by Fisher'southward Verbal Test (p < .001).
Staging of Thyroid Carcinoma.
Patients who received thyroidectomy past an ENT surgeon had a more advanced stage of disease than those who received thyroidectomy by a general surgeon by Wilcoxon Exact Test when noncancer patients were included in the assay (Fig. 2;p= .02). When just patients with thyroid carcinoma were included in the assay, however, there was no divergence between the surgical groups in the phase of thyroid carcinoma (p= .63), and the difference between the surgical groups persisted with respect to the occurrence of permanent postoperative hypoparathyroidism (p= .004 by Fisher's Verbal Exam).
Distribution of staging of epithelial thyroid carcinoma according to the method of Mazzaferri.24
Clustering of Outcomes Within Specific Surgeons.
Logit analysis using a generalized estimating equation model to assess for the effects of clustering verified the divergence in hypoparathyroidism between the two surgical groups (p < .001).
Other Variables.
In that location was no departure betwixt surgical specialties in the development of transient postoperative hypoparathyroidism by Fisher'due south Exact Exam (p= .50). There were no significant differences betwixt surgical specialties in preoperative or postoperative serum calcium concentrations at 1 to 7 days, 1 month, or 6 months after thyroidectomy by unpaired Pupil's t test (information non shown, p>.05). Furthermore, Fisher'south Exact Test indicated no significant difference between the surgical groups in the performance of a preoperative fine needle thyroid biopsy (p= .62), the involvement of resident physicians in the operative procedure (p= .71), or the postoperative recurrence of thyroid carcinoma among those patients with cancer (p= .81). Laryngeal nervus injury occurred in two (six%) of 31 patients in the ENT group and in 2 (two%) of 111 patients in the general surgery group (p= .57). No deaths occurred among patients in this study over the relatively short follow-up period examined.
Give-and-take
This study suggests that thyroidectomy performed past an ENT surgeon (or unidentified associated factors) may carry higher risk of persistent postoperative hypoparathyroidism than thyroidectomy performed by a general surgeon. This finding is qualified, however, past other factors that may impact this hazard and are not uniformly distributed among the study groups. Specifically, a postoperative diagnosis of thyroid carcinoma appears to be a pregnant predictor of persistent postoperative hypoparathyroidism, and the ENT surgeons predominantly cared for patients with this status. These data might even be interpreted as suggesting that full general surgeons more oftentimes perform thyroidectomy for indications that are ambiguous or medically uncertain. Moreover, considering all of the cases of persistent postoperative hypoparathyroidism in this study occurred amidst patients with thyroid cancer, no conclusions can be drawn from these data regarding the take a chance of this complication following thyroidectomy for nonmalignant indication.
The fact that patients in the ENT grouping possessed a more advanced stage of disease than patients in the general surgery group further suggests that these patients were at higher risk of postoperative complications earlier thyroidectomy was even begun. As shown in Table 3, each increase in the phase of thyroid carcinoma was associated with a near doubling of the odds for developing persistent postoperative hypoparathyroidism. The discrepancy between the surgical groups in the phase of thyroid carcinoma apparent in this study may ultimately reflect an underlying referral bias, with more than severely afflicted subjects being referred to ENT surgeons. Finally, the performance of a more aggressive operative procedure past the ENT surgeons besides may have contributed to the difference we observed in our chosen outcome parameter. This practice may be desirable because modified radical cervix autopsy in addition to thyroidectomy is associated with a decreased rate of tumor recurrence in patients with thyroid carcinoma, although improved survival has not been demonstrated. 6,7,8,ix,26–thirty Because the presence of cancer as the indication for thyroidectomy and the performance of more aggressive surgery are both closely related to the phase of the underlying thyroid carcinoma, neither of these factors was identified as an independent variable when adjustment was fabricated for the result of stage.
Given the diversity of factors that appear to contribute to the development of persistent postoperative hypoparathyroidism, information technology is unlikely that one factor, such as surgical specialty, volition exert a asymmetric influence on this consequence if all other factors are equalized. Information technology may be more than accurate to consider a scenario in which a confluence of take a chance factors determines the ultimate incidence of this postoperative complexity. Such a schema is presented in Figure iii, with a postulated high-take chances pathway depicted on the left and a low-risk pathway depicted on the correct. Information technology seems likely that such a multifactorial scenario near accurately describes the occurrence of postoperative hypoparathyroidism in our study population.
Postulated chain of events leading to persistent postoperative hypoparathyroidism. Factors on the left are associated with an increased risk of this operative complexity. Numbers in italics represent subjects included in the current study.
Similar studies on surgical outcomes have been previously published. Ouriel et al., for example, demonstrated improved postoperative survival when ruptured aortic aneurysm is repaired past a vascular surgeon as compared with a general surgeon among 243 patients and vi hospitals in Rochester, New York. 21 Such studies highlight the existence of differences between and within specialties with respect to medical outcomes, merely how such information should be used by the medical customs is unclear. Variability between specialties in important issue measures may be attributable to differences in training, estimation of the existing literature, patient populations, physician feel, knowledge, skill, or luck. Moreover, it is probable that regional differences in event as well exist, and these geographic effects may be every bit (or more) important in determining outcome in any given patient. Thus, studies demonstrating an improved event with ane specialty relative to some other should be interpreted cautiously.
Limitations of this report include a small sample size, a reduced power of the report to detect differences equally a result of the modest number of cases of postoperative hypoparathyroidism, the possible restriction of its findings to New United mexican states, and the limitations inherent in a retrospective analysis. Likewise, we were unable to obtain information on the experience of the surgeons performing thyroidectomy in this study. Most experts feel that the experience of the surgeon is one of the most important factors in the avoidance of postoperative complications, and it is conceivable that less experienced physicians were clustered in the ENT group in this study. Furthermore, the validity of our clustering analysis, which was performed as a secondary analysis, may be express by the pocket-size sample size. Withal, considering randomized, controlled, prospective studies to determine the optimal surgical management of thyroid disease accept not been performed, retrospective studies provide valuable information about current medical practice, cost, and outcome. A preponderance of evidence obtained from such studies may ultimately effect a change in medical exercise. Conspicuously, more definitive studies of the outcome of thyroidectomy are required before such a change can exist advocated.
The interest of resident surgeons during thyroidectomy did not prove to be a significant factor in the evolution of permanent postthyroidectomy hypoparathyroidism in this study. Similarly, the performance of a preoperative fine needle biopsy of the thyroid did not affect this outcome parameter. Although these findings may reflect a type II statistical mistake resulting from the minor sample size, there is no a priori reason to suspect that either of these factors would play a significant role in the development of postoperative hypoparathyroidism. The lack of difference between the surgical groups in the occurrence of RLN injury may also reflect a type Ii statistical error, but the rates of RLN injury reported here are consistent with rates reported in other studies. 3, 10, eleven
Nosotros conclude that patients who undergo thyroidectomy by an ENT surgeon may exist at an increased take a chance of developing persistent postoperative hypoparathyroidism. Differences in example selection and surgical approach account for some of this disparity, however, and the presence of an advanced phase of thyroid carcinoma is likely to be the most important predictor of this effect. Referring physicians should be aware of the risk of hypoparathyroidism that accompanies thyroidectomy and talk over this hazard with their patients. The risk of permanent postoperative hypoparathyroidism may ultimately exist reduced by careful advice between the referring physician and the surgeon virtually the type and extent of surgery perceived to exist necessary.
REFLECTIONS
Respite
An intermezzo of silence and solitude: no failing heartbeats or murmurs, no crackles or coughs or shrill alarms, no cries or pleas or questions I cannot respond or comfort I cannot requite; no shadows to interpret, tracings to measure, or screens to picket; no grief to witness, suffering to see, hurting to affect, or lifeless eyes for me to shut. Out at present, of the fluorescent rendering of perpetual twenty-four hour period, I stand in the placidity darkness of night, twenty-two stories above the snow-wrapped earth, and spotter the city sleeping below, and I heed drowsily to its lullaby.
Garth Meckler, MD
Seattle, Launder.
Acknowledgments
The authors gratefully acknowledge the efforts of Robert Ferraro, MD, in assisting the acquisition of data from Presbyterian Medical Center for the purposes of this study.
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