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Abstract(s)
A identificação intraoperatória das glândulas paratiroideias é sempre um desafio que se
coloca aos cirurgiões, em cirurgia tiroideia e paratiroideia, pois as pequenas dimensões,
coloração e forma destas glândulas tornam difícil a sua diferenciação de gânglios linfáticos,
tecido adiposo e mesmo de pequenos nódulos tiroideus.
Em 2011, investigadores da Universidade de Vanderbilt descreveram pela primeira vez a
autofluorescência das paratiroides quando submetidas a luz infravermelho próximo,
propriedade potencialmente útil para a sua identificação intraoperatória.
No presente trabalho foram realizados vários estudos tentando contribuir para o aumento
do conhecimento neste campo.
Tendo as glândulas paratiroideias e tiroide características próprias pela sua natureza
secretória, tentámos em primeiro lugar assegurar a inocuidade da estimulação luminosa no
padrão de secreção hormonal, em modelo animal. Dois grupos de ratos Wistar foram
submetidos a incisão cervical para exposição da região tiro-paratiroideia, sendo um dos
grupos irradiado com fonte de luz infravermelho próximo. Efetuaram-se colheitas
sanguíneas para doseamentos de T3, T4, TSH, cálcio e PTH no pré-operatório, 7 minutos
após exposição e aos 30 e 60 dias do pós-operatório, nos animais de ambos os grupos. Não
foram registadas diferenças significativas nos resultados analíticos dos dois grupos, sendo
as pequenas alterações encontradas transitórias.
Noutro estudo procedeu-se ao exame histológico convencional e microscopia eletrónica das
peças operatórias dos dois grupos (irradiado e controlo). Não foram encontradas diferenças
estruturais ou ultraestruturais entre os tecidos de ambos os grupos.
Estes estudos permitem concluir que a irradiação da região cervical com luz infravermelho
próximo, nas condições que permitem a sua identificação por autofluorescência, é inócua
para os tecidos, não alterando o seu padrão de secreção.
Outra vertente deste trabalho teve como objetivo a demonstração da possibilidade de a
autofluorescência das paratiroides poder ser detetada sem recurso a tecnologia dispendiosa,
sendo estudada a utilização de um dispositivo de baixo custo baseado em óculos de visão
noturna com a adequada filtração luminosa. Este dispositivo foi testado in vitro, com análise de 32 peças operatórias, revelando-se
muito eficaz na discriminação entre os tecidos (p<0.001).
Os estudos subsequentes, com utilização do dispositivo desenvolvido, orientaram-se para a
utilização intraoperatória, contribuição para a validação da técnica.
- Quarenta peças operatórias de cirurgias tiroideias foram examinadas com recurso ao
dispositivo acima referenciado, para identificação de tecido paratiroideu incidentalmente
excisado, sendo os dados obtidos confrontados com o exame histológico. Foram detetados
com o dispositivo sete dos oito fragmentos de paratiroides identificados no exame
anatomopatológico, existindo um falso positivo (nódulo coloide), representando uma
sensibilidade de 87,5 % e uma especificidade de 97,1 %. A presença de tecido paratiroideu
na peça operatória não teve, contudo, repercussão nas taxas de hipocalcemia pósoperatória.
- Em cinco casos consecutivos de cirurgias por hiperparatiroidismo primário e exames de
localização não concordantes, relativamente à localização superior ou inferior da glândula
patológica, foi utilizada a autofluorescência como auxiliar na identificação das glândulas
paratiroideias. O sistema permitiu a identificação de todas as glândulas procuradas,
aumentando a confiança do cirurgião nessa identificação, refletindo-se na decisão de não
proceder à exploração bilateral.
- Quarenta e cinco pacientes consecutivos submetidos a tiroidectomia total com utilização
da autofluorescência para identificação das glândulas paratiroideias (grupo de estudo),
foram comparados com os 60 doentes operados anteriormente pelo mesmo cirurgião sem
utilização da autofluorescência (grupo controlo), sendo objetivos principais a avaliação da
hipocalcemia e hipoparatiroidismo pós-operatórios, o número de paratiroides
identificadas, bem como o número de paratiroides incidentalmente ressecadas.
Os pacientes no grupo de estudo apresentaram valores de hipoparatiroidismo
significativamente inferiores (p=0,044). Apesar da redução observada neste grupo nos
valores absolutos de cálcio e no número de pacientes com hipocalcemia, esta diferença não
foi estatisticamente significativa. No grupo de estudo não existiram casos de hipocalcemia
permanente, que ocorreu em três pacientes no grupo controlo.
O número de glândulas paratiroideias identificadas foi significativamente superior no grupo
de estudo (p<0.001). A capacidade de o dispositivo identificar acuradamente glândulas
paratiroideias inadvertidamente excisadas atingiu neste estudo uma sensibilidade de 100 %
e uma especificidade de 87,5 %. Sendo a autofluorescência das paratiroides um fenómeno pouco conhecido, desenvolvemos
um estudo in vitro para avaliar a persistência da autofluorescência em glândulas
submetidas a congelação, aquecimento e fixação em formalina. Os resultados obtidos
confirmaram a robustez do fenómeno, demonstrando-se a persistência da fluorescência
mesmo após exposição a condições extremas.
Também no sentido de um melhor esclarecimento do fenómeno, procedemos a análises
tecidulares com recurso a técnicas de Ground State Diffuse Reflectance Absorption Spectra
e Laser induced luminescence, que, apesar de não terem fornecido pistas sobre a origem da
autofluorescência, mostraram a existência de outros picos de emissão luminosa, passíveis
de ser utilizados para a identificação das paratiroides, abrindo outro campo de investigação.
Do conjunto de todos os trabalhos desenvolvidos, concluímos que a autofluorescência das
paratiroides na gama do infravermelho próximo, sendo inócua para os tecidos e não
influenciando significativamente o padrão de secreção hormonal, poderá tornar-se uma
ferramenta útil para a identificação intraoperatória das mesmas em cirurgia tiroideia e
paratiroideia.
surgeons performing thyroid and parathyroid surgery. Differentiation from lymph nodes, fatty tissue or small thyroid nodules is not straightforward due to their small size, uncharacteristic shape and color. In 2011 researchers from Vanderbilt university described for the first time the autofluorescence of parathyroid glands when submitted to a near infrared light, heralding a potentially useful property that may facilitate their intraoperative identification. In this work, the authors present the relevant studies that contribute to the increasing knowledge of this field. Bearing in mind the endocrine secretory nature of the thyroid and parathyroid glands, the authors tried to assure the innocuity of the light stimulation on the secretory pattern on an animal model. Two groups of Wistar rats were submitted to a cervical incision exposing the thyroparathyroid area. In one group the area was irradiated with a near infrared light, whereas in the other group no light stimulation was done. Blood samples were collected before surgery, 7 minutes after irradiation, 30 days and 60 days after surgery for the evaluation of T3, T4, TSH, total calcium and PTH. Results showed only mild and transient non-significant alterations. In another study we analyzed the thyroparathyroid blocs of both irradiated and nonirradiated rats by conventional histology and by electron microscopy. No significant structural or ultra-structural alterations were found. These studies suggest that near infrared irradiation of the cervical area is safe to the thyroid and parathyroid tissue from the secretory and morphological standpoint. Another objective of our study was proving the hypothesis of parathyroid autofluorescence detection using simple technology devices, namely low cost goggle devices with appropriate filters. For this purpose, 32 operative samples were subjected to in vitro analysis, revealing a high efficacy in tissue discrimination (p<0.001). Subsequent studies were directed to the intraoperative utilization of the device, contributing for validation of the technique. - Forty operative samples of thyroid surgeries were examined with the near infrared device for identification of incidentally removed parathyroid tissue and the results were compared with the pathological report. The device detected seven of eight fragments of parathyroid tissue identified by pathological exam with one false positive (colloid nodule), representing a sensitivity of 87,5 % and a specificity of 97,1 %. Presence of parathyroid tissue on sample didn’t affect post-operative hypocalcemia. - In five consecutive surgeries for primary hyperparathyroidism with non-concordant localization studies regarding superior or inferior position of the diseased gland, we used the device as an ancillary tool for identification of the glands. All the glands sought were identified. The increased confidence on the correct identification of parathyroid glands by the surgeon supported the decision of not performing bilateral exploration. - Outcomes of 45 consecutive patients submitted to total thyroidectomies using autofluorescence to identify parathyroid glands in situ (study group) were compared with the previous 60 patients operated by the same surgeon without using autofluorescence (control group). Main objectives were the evaluation of postoperative hypocalcemia and hypoparathyroidism, number of glands identified and number of incidentally removed parathyroid glands. The study group had a significant reduction in the incidence of postoperative hypoparathyroidism (p=0,044). Despite being observed a reduction of postoperative hypocalcemia and higher postoperative serum calcium levels in the study group, no statistically significant differences were verified. There were no cases of permanent hypocalcemia in the study group while 3 patients in the control group remained dependent of calcium supplementation for more than 6 months after surgery. The number of parathyroid glands identified was significantly higher in the study group (p<0.001). The capacity of the device to identify incidentally removed parathyroid glands achieved a sensitivity of 100 % and a specificity of 87,5 %. As autofluorescence of parathyroid glands is a relatively unknown phenomenon we performed a study to evaluate in vitro the persistence of autofluorescence in parathyroid glands submitted to heat, freezing and formalin fixation. Results confirmed the robustness of the phenomenon with persistence of autofluorescence even after exposition to extreme conditions. In order to increase current understanding of autofluorescence the author also performed spectroscopy of parathyroid and thyroid glands using techniques of Ground State Diffuse Reflectance Absorption and Laser Induced Luminescence. In spite of not providing clues about the responsible fluorophore those works identified other spikes of fluorescence emission that can be potentially useful for identification of parathyroid glands, opening a new field of research. The sum of our works allowed us to conclude that near infrared autofluorescence of parathyroid glands is harmless to the tissues and do not affect the glandular secretory pattern. As such, this technique may become a useful tool for intraoperative identification of parathyroid glands during thyroid and parathyroid surgeries.
surgeons performing thyroid and parathyroid surgery. Differentiation from lymph nodes, fatty tissue or small thyroid nodules is not straightforward due to their small size, uncharacteristic shape and color. In 2011 researchers from Vanderbilt university described for the first time the autofluorescence of parathyroid glands when submitted to a near infrared light, heralding a potentially useful property that may facilitate their intraoperative identification. In this work, the authors present the relevant studies that contribute to the increasing knowledge of this field. Bearing in mind the endocrine secretory nature of the thyroid and parathyroid glands, the authors tried to assure the innocuity of the light stimulation on the secretory pattern on an animal model. Two groups of Wistar rats were submitted to a cervical incision exposing the thyroparathyroid area. In one group the area was irradiated with a near infrared light, whereas in the other group no light stimulation was done. Blood samples were collected before surgery, 7 minutes after irradiation, 30 days and 60 days after surgery for the evaluation of T3, T4, TSH, total calcium and PTH. Results showed only mild and transient non-significant alterations. In another study we analyzed the thyroparathyroid blocs of both irradiated and nonirradiated rats by conventional histology and by electron microscopy. No significant structural or ultra-structural alterations were found. These studies suggest that near infrared irradiation of the cervical area is safe to the thyroid and parathyroid tissue from the secretory and morphological standpoint. Another objective of our study was proving the hypothesis of parathyroid autofluorescence detection using simple technology devices, namely low cost goggle devices with appropriate filters. For this purpose, 32 operative samples were subjected to in vitro analysis, revealing a high efficacy in tissue discrimination (p<0.001). Subsequent studies were directed to the intraoperative utilization of the device, contributing for validation of the technique. - Forty operative samples of thyroid surgeries were examined with the near infrared device for identification of incidentally removed parathyroid tissue and the results were compared with the pathological report. The device detected seven of eight fragments of parathyroid tissue identified by pathological exam with one false positive (colloid nodule), representing a sensitivity of 87,5 % and a specificity of 97,1 %. Presence of parathyroid tissue on sample didn’t affect post-operative hypocalcemia. - In five consecutive surgeries for primary hyperparathyroidism with non-concordant localization studies regarding superior or inferior position of the diseased gland, we used the device as an ancillary tool for identification of the glands. All the glands sought were identified. The increased confidence on the correct identification of parathyroid glands by the surgeon supported the decision of not performing bilateral exploration. - Outcomes of 45 consecutive patients submitted to total thyroidectomies using autofluorescence to identify parathyroid glands in situ (study group) were compared with the previous 60 patients operated by the same surgeon without using autofluorescence (control group). Main objectives were the evaluation of postoperative hypocalcemia and hypoparathyroidism, number of glands identified and number of incidentally removed parathyroid glands. The study group had a significant reduction in the incidence of postoperative hypoparathyroidism (p=0,044). Despite being observed a reduction of postoperative hypocalcemia and higher postoperative serum calcium levels in the study group, no statistically significant differences were verified. There were no cases of permanent hypocalcemia in the study group while 3 patients in the control group remained dependent of calcium supplementation for more than 6 months after surgery. The number of parathyroid glands identified was significantly higher in the study group (p<0.001). The capacity of the device to identify incidentally removed parathyroid glands achieved a sensitivity of 100 % and a specificity of 87,5 %. As autofluorescence of parathyroid glands is a relatively unknown phenomenon we performed a study to evaluate in vitro the persistence of autofluorescence in parathyroid glands submitted to heat, freezing and formalin fixation. Results confirmed the robustness of the phenomenon with persistence of autofluorescence even after exposition to extreme conditions. In order to increase current understanding of autofluorescence the author also performed spectroscopy of parathyroid and thyroid glands using techniques of Ground State Diffuse Reflectance Absorption and Laser Induced Luminescence. In spite of not providing clues about the responsible fluorophore those works identified other spikes of fluorescence emission that can be potentially useful for identification of parathyroid glands, opening a new field of research. The sum of our works allowed us to conclude that near infrared autofluorescence of parathyroid glands is harmless to the tissues and do not affect the glandular secretory pattern. As such, this technique may become a useful tool for intraoperative identification of parathyroid glands during thyroid and parathyroid surgeries.
Description
Keywords
Tiroide Paratiroide Autofluorescência Cirurgia Infravermelho próximo Hipocalcemia Hipoparatiroidismo