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  2. 2. SELF ASSESSMENT QUESTIONS 1. Regarding parathyroid glands a. The chief cells secrete parathyroid hormone b. They develop from the third and fourth pharyngeal pouches c. The normal plasma level of intact parathyroid hormone is 10-55pg/mL d. The most common abnormality is multiple gland hyperplasia e. Hyperparathyroidism is associated with both MEN type I and II 2. With regards to calcium metabolism a. It is the ionised calcium concentration which influences the physiological effects b. The normal value of ionised calcium is 2.12-2.65mmol/l c. Calcitonin plays a major role in calcium homeostasis in humans d. Absorption of Ca2+ from the GI tract is regulated by parathyroid hormone e. 98-99% of filtered calcium is reabsorbed in the kidney 3. Regarding hyperparathyroidism a. The most common cause of primary hyperparathyroidism is a solitary adenoma b. The majority of patients with hyperparathyroidism are symptomatic at diagnosis c. The incidence of primary hyperparathyroidism in the UK is thought to be 25 per 100,000 d. The commonest cause of secondary hyperparathyroidism is chronic renal failure e. Technetium -99 m sestamibi scanning is the most accurate method for the preoperative localization of the parathyroid glands
  3. 3. 4. Regarding anaesthesia for parathyroid surgery a. An acceptable preoperative calcium level is <3mmol/l b. The usual indication for surgery is primary hyperparathyroidism from a parathyroid adenoma c. The intraoperative use of methylene blue can cause a false low SpO2 reading. d. Minimally invasive parathyroidectomy can be done under superficial cervical plexus block and sedation e. From an airway obstruction point of view a partial lesion of the recurrent laryngeal nerve is more serious than a complete lesion 5. With regard to the perioperative management of hyperparathyroidism a. Intravenous Bisphosphonate is the first line drug therapy in the treatment of life threatening hypercalcaemia b. Serum calcium should be checked at 6 and 24 hrs after parathyroidectomy c. Postoperative hypocalcaemia and hypomagnesaemia from “hungry bones” is seen more often after surgery for secondary hyperparathyroidism. d. Positive Chvostek’s sign refers to carpopedal spasm elicited by cuff inflation. e. Airway encroachment is common with parathyroid tumours
  4. 4. Endocrine surgeries have been on the rise for the last few years. During surgery, endocrine disorders present unique challenges to the endocrinologist and to the attending anesthesiologist. The endocrine, electrolyte and metabolic disturbances resulting from such disorders can have a profound effect on the normal human physiological milieu. Surgery of parathyroid glands is no exception and is associated with a multiple challenges during pre-, intra-, and post- operative period. Pre-op examination and optimization is essential so as to prevent any intra-op or post-op complications. The most striking electrolyte disturbance during parathyroid surgery is the imbalance of calcium levels in the body and the main emphasis during the entire peri- operative period revolves around the maintenance of normal serum calcium levels. INTRODUCTION
  5. 5. Disorders of the Parathyroid Glands Maintenance of calcium, phosphate and magnesium homeostasis is under the influence of two polypeptide hormones; parathyroid hormone(PTH), and calcitonin (CT), as well as a sterol hormone, 1,25 dihydro-cholecalciferol (1,25 (OH)2D3
  6. 6. Disorders of the Parathyroid Glands These hormones regulate the flow of minerals in and out of the extracellular fluid compartments through their actions on intestine, kidneys, and bones.
  7. 7. Disorders of the Parathyroid Glands The PTH acts directly on the bones and kidneys and indirectly on the intestine through its effect on the synthesis of 1,25 (OH)2D3. Its production is regulated by the concentration of serum ionized calcium. Lowering of the serum calcium levels will induce an increased rate of parathyroid hormone secretion
  8. 8. Disorders of the Parathyroid Glands Calcitonin is released by the “C” cells (parafollicular cells in the thyroid gland) in response to small increases in plasma ionic calcium. It acts on the kidney and bones to restore the level of calcium to just below a normal set point which in turn inhibits secretion of the hormone.
  9. 9. Disorders of the Parathyroid Glands Calcitonin is therefore the physiological antagonist of PTH. The two hormones act in concert to maintain normal concentration of calcium ion in the extracellular fluid.
  10. 10. Disorders of the Parathyroid Function Hyperparathyroidism Primary hyperparathyroidism is due to excessive production of PTH by one or more of hyper functioning parathyroid glands. This leads to hypercalcemia which fails to inhibit the gland activity in the normal manner.
  11. 11. Disorders of the Parathyroid Function Hyperparathyroidism The cause of primary hyperparathyroidism is unknown. A genetic factor may be involved. The clonal origin of most parathyroid adenomas suggests a defect at the level of the gene controlling the regulation and/or expression of parathyroid hormone.
  12. 12. Disorders of the Parathyroid Function Hyperparathyroidism The incidence of the disease increases dramatically after the age of 50 and it is 2-4 folds more common in women. A single adenoma occurs in about 80% of patients with primary hyperparathyroidism. Four glands hyperplasia account for 15-20% of cases. A parathyroid carcinoma could be the etiology in a rare incidence of less then 1%.
  13. 13. Disorders of the Parathyroid Function Clinical Features: The two major sites of potential complications are the bones and the kidneys. The kidneys may have renal stones (nephrolithiasis) or diffuse deposition of calcium- phosphate complexes in the parachyma (nephrocalcinosis). Now a days such complications are seen less commonly and around 20% of patients or less show such complications.
  14. 14. Disorders of the Parathyroid Function Clinical Features: In skeleton a condition called osteitis fibrosa cystica could occur with sub-periosteal resorption of the distal phalanges, distal tappering of the clavicles, a “salt and pepper” appearance of the skull as well as bone cysts and brown tumors of the long bones. Such overt bone disease even though typical of primary hyperparathyroidism is very rarely encountered.
  15. 15. Disorders of the Parathyroid Function Clinical Features: Now a days almost 90% of diagnosed cases in the developed countries are picked up by routine screening for calcium level using the new automated machines.
  16. 16. Disorders of the Parathyroid Function Clinical Features: Other symptoms include muscle weakness, easy fatigability, peptic ulcer disease, pancreatitis, hypertension, gout and pseudogout as well as anemia and depression have been associated with primary hyperparathyroidism.
  17. 17. 1. Primary hyperparathyroidism A. Solitary adenomas B. Multiple endocrine neoplasia 2. Lithium therapy 3. Familial hypocalciuric hypercalcemia 1. Vitamin D intoxication 2. 1,25(OH)2D; sarcoidosis and other granulomatous diseases 3. Idiopathic hypercalcemia of infancy Differential Diagnosis Causes of Hyper-calcemia Parathyroid - related Vitamin D – related
  18. 18. Differential Diagnosis Causes of Hypercalcemia Malignancy - related 1. Solid tumor with metastases(breast) 2. Solid tumor with humoral mediation of hypercalcemia (lung kidney) 3. Hematologic malignancies (multiple myeloma, lymphoma, leukemia) Associated with high bone turnover 1. Hyperthyroidism 2. Immobilization 3. Thiazides 4. Vitamin A intoxication Assocated with Renal Failure: 1. Severe secondary hyperparathyroidism 2. Aluminum intoxication 3. Milk alkali syndrome
  19. 19. Diagnosis The presence of established hypercalcaemia in more than one serum measurement accompanied by elevated immunoreactive PTH is characteristic (iPTH)
  20. 20. Diagnosis Serum phosphate is usually low but may be normal. Hypercalcemia is common and blood alkaline phosphatase (of bone origin) is raised.
  21. 21. Other Diagnostic tests Radiograph: Plain X-ray of hands can be diagnostic showing sub periosteal bone resorption usually on the radial surface of the distal phalanx with distal phalangeal tufting as well as cysts formation and generalized osteopenia.
  22. 22. Other Diagnostic tests Pre-operative localization of the abnormal parathyroid gland(s): • Ultrasonography • MRI • CT • Thallium 201 – Tehcnichum99m scan (subtraction study)
  23. 23. Parathyroid Scan Dual phase MIBI Scan Tc-Tl Subtraction Scan
  24. 24. Treatment A large proportion of patients have “biochemical” hyperparathyroidism but with prolonged follow up they progress to overt clinical presentation. Resection of the parathyroid lesion is curative with recurrences observed mainly in the multiple glandular disease.
  25. 25. Medical Treatment of the hypercalcaemia In acute severe forms the main stay of therapy is adequate hydration with saline and forced diuresis by diuretics to increase the urinary excretion of calcium rapidly along with sodium and prevent its reabsorption by the renal tubules.
  26. 26. Other agents • Glucocostiroids – In hypercalcaemia associated the hematological malignant neoplasms • Mythramycin – A toxic antibiotics which inhibit bone resorption and is used in hematological and solid neoplasms causing hypercalcaemia.
  27. 27. Other agents • Calcitonin – Also inhibit osteoclast activity and prevent bone resorption • Bisphosphonates – They are given intravenously or orally to prevent bone resorption.
  28. 28. Other agents • Phosphate – Oral phosphate can be used as an antihypercalcaemic agent and is commonly used as a temporary measure during diagnostic workup. • Estrogen – It also decrease bone resorption and can be given to postmenopausal women with primary hyperparathyroidism using medical therapy
  29. 29. Surgery Surgical treatment should be considered in all cases with established diagnosis of primary hyperparathyroidism. During surgery the surgeon identifies all four parathyroid glands (using biopsy if necessary) followed by the removal of enlarged parathyroid or 3 ½ glands in multiple glandular disease.
  30. 30. Secondary hyperparathyroidism An increase in PTH secretion which is adaptive and unrelated to intrinsic disease of the parathyroid glands is called secondary hyperparathyroidism. This is due to chronic stimulation of the parathyroid glands by a chronic decrease in the ionic calcium level in the blood
  31. 31. Major causes of chronic hypocalcemia other than hypoparathyroidism • Deficiency of vitamin D or calcium • Decreased intestinal absorption of vitamin D or calcium due to primary small bowel disease, short bowel syndrome, and post- gastrectomy syndrome. • Drugs that cause rickets or osteomalacia such as phenytoin, phenobarbital, cholestyramine, and laxative.
  32. 32. Major causes of chronic hypocalcemia other than parathyroprival hypoparathyroidism • States of tissue resistance to vitamin D • Excessive intake of inorganic phosphate compunds • Psudohypoparathyroidism • Severe hypomagnesemia • Chronic renal failure
  33. 33. Hypoparathyroidism Deficient secretion of PTH which manifests itself biochemically by hypocalcaemia, hyperphosphatemia diminished or absent circulating iPTH and clinically the symptoms of neuromuscular hyperactivity.
  34. 34. Hypoparathyroidism Causes: •Surgical hypoparathyroidism The commonest After anterior neck exploration for thyroidectomy, abnormal parathyroid gland removal, excision of a neck lesion. It could be due to the removal of the parathyroid glands or due to interruption of blood supply to the glands.
  35. 35. Hypoparathyroidism Causes: • Idiopathic hypoparathyroidism – A form occurring at an early age (genetic origin) with autosomal recessive mode of transmission “multiple endocrine deficiency – autoimmune-candidiasis (MEDAC) syndrome” – “Juvenile familial endocrinopathy” – “Hypoparathyroidism – Addison's disease – mucocutaneous candidiasis (HAM) syndrome”
  36. 36. Hypoparathyroidism Causes: • Idiopathic hypoparathyroidism – Circulating antibodies for the parathyroid glands and the adrenals are frequently present. – Other associated disease: • Pernicious anemia • Ovarian failure • Autoimmune thyroiditis • Diabetes mellitus
  37. 37. Hypoparathyroidism Causes: • Idiopathic hypoparathyroidism – The late onset form occurs sporadically without circulating glandular autoantibodies. • Functional hypoparathyroidism – In patients who has chronic hypomagnesaemia of various causes. – Magnesium is necessary for the PTH release from the glands and also for the peripheral action of the PTH.
  38. 38. A. Neuromuscular – The rate of decrease in serum calcium is the major determinant for the development of neuromuscular complications. – When nerves are exposed to low levels of calcium they show abnormal neuronal function which may include decrease threshold of excitation, repetitive response to a single stimulus and rarely continuous activity. Hypoparathyroidism Clinical Features:
  39. 39. A. Neuromuscular – Paresthesia – Tetany – Hyperventilation – Adrenergic symptoms – Convulsion (More common in young people and it can take the form of either generalized tetany followed by prolonged tonic spasms or the typical epileptiform seizures. – Signs of latent tetany • Chevostek sign • Trousseau sign • Extrapyramidal signs (due to basal ganglia calcification) Hypoparathyroidism Clinical Features:
  40. 40. B. Other clinical manifestation 1. Posterio -lenticular cataract 2. Cardiac manifestation: – Prolonged QT interval in the ECG – Resistance to digitalis – Hypotension – Refractory heart failure with cardiomegally can occur Hypoparathyroidism Clinical Features:
  41. 41. B. Other clinical manifestation 3. Dental Manifestation Abnormal enamel formation with delayed or absent dental eruption and defective dental root formation. 4. Malabsorption syndrome Presumably secondary to decreased calcium level and may lead to steatorrhoea with long standing untreated disease. Hypoparathyroidism Clinical Features:
  42. 42. Hypoparathyroidism Diagnosis: In the absence of renal failure the presence of hypocalcaemia with hyperphosphatemia is virtually diagnostic of hypoparathyroidism. Undetectable serum iPTH confirms the diagnosis or it can be detectable if the assay is very sensitive.
  43. 43. Hypoparathyroidism Treatment: The mainstay of treatment is a combination of oral calcium with pharmacological doses of vitamin D or its potent analogues. Phosphate restriction in diet may also be useful with or without aluminum hydroxide gel to lower serum phosphate level.
  44. 44. Emergency Treatment for Hypocalcaemic Tetany: Calcium should be given parenterally till adequate serum calcium level is obtained and then vitamin D supplementation with oral calcium should be initiated.
  45. 45. Pseudohypoparathysoidism and Pseudopseudohypoparathyroidism A rare familial disorders with target tissue resistance to PTH. There is hypocalcaemia, hyperphosphataemia, with increased parathyroid gland function. There is also a variety of congenital defects in the growth and development of skeleton including: • Short statue • Short metacarpal and metatarsal bones
  46. 46. • Endocrine surgeries and emergencies pose unique challenges to the attending anaesthesiologists and the intensivists. • The most striking electrolyte disturbance during parathyroid surgery is the imbalance of calcium levels in the body and the main emphasis during the entire peri-operative period revolves around the maintenance of normal serum calcium levels. • The precautionary measures have to be taken during administration of anesthesia as thiopentone and volatile anaesthetic prolong the QTc interval. Similarly few drugs like macrolides, quinolones, antifungals like ketoconazole and fluconazole should better be avoided during the peri-operative period as they also have a potential to prolong QTc interval. • Renal scans and ultrasound are sometimes carried out for diagnosis of renal stones which is very useful for the formulation and planning for peri-operative renal protection strategies when
  47. 47. Pre-op Optimization The clinical symptomatology is diverse and may include moderate to severe dehydration, tachycardia, polyuria, anorexia, vomiting, extreme weakness lethargy, and mental signs and symptoms including psychosis which needs thorough investigations. In untreated cases the condition can deteriorate rapidly and can progress to coma and collapse.
  48. 48. The emergency therapeutic interventions for optimization of hypercalcaemia include: • Infusion of normal saline@ 2.5-3.0 ml/kg/hr with a maximum optimization up to 4-6 liters. • Biphosphonates such as Pamidronate 60 mg is the first line of drug for treatment of life threatening hypercalcaemia (Ca2+>4.5 mmol/l) • Infusion of phosphate - to lower life threatening hypercalcaemia (>4.5 mmol/l) • Calcitonin in doses of 3-4 U/kg - either intravenously (IV) or subcutaneously to lower the calcium levels. • Plicamycin and mithramycin administration is done cautiously as these drugs have a very narrow therapeutic index. • Frusemide is administered for forced saline diuresis as it inhibits tubular reabsorption of calcium while simultaneously measuring central venous pressure. • Although controversial, corticosteroids administered during the acute phase possibly inhibit further absorption of calcium from the
  49. 49. Regional vs. General Anaesthesia
  50. 50. Premedication • Alprazolam • H2 antagonist ranitidine • Sodium citrate • Glycopyrrolate 0.2 mg Airway management pathological fractures due to prolonged hypercalcemia? unstable cervical spine as a result of lytic lesions
  51. 51. Hypercalcaemia may cause inadequate reversal due to unpredictable augmentation of non-depolarizing neuromuscular blockade, thus possibly leading to post-operative hypoxemia and respiratory obstruction. Extubation should be carried out in a fully awake state and after establishing a regular breathing pattern with adequate tidal volume and muscle strength.
  52. 52. POST-OP COMPLICATIONS • Bleeding: Post-operative episode of bleeding and subsequent development of hematoma can cause respiratory obstruction. Therefore, all the dressings should be checked thoroughly before the patient is shifted to their respective wards from the recovery area. • Metabolic abnormalities: Hypophosphatemia, hypomagnesemia, and hypokalemia can prove catastrophic during post-op period and should be rectified at the earliest. The combined picture projects a constellation of clinical symptomatology such as cardiac failure, dysarrhythmias, neuromuscular irritability hemolysis, platelet dysfunction, and leucocyte dysfunction. • Hypocalcemic tetany: It occurs due to drastic reduction in post- operative serum calcium levels four to five days post-operatively and is clinically manifested by laryngeal spasms, seizures, and presence of Chvostek's and Trousseau's sign.
  53. 53. Minimally invasive parathyroidectomy  Minimally invasive radio-guided parathyroidectomy is being performed with a gamma probe in cases of persistent and recurrent hyperparathyroidism.  The endoscopic dissection with insufflations of gas has also been performed for minimally invasive endoscopic parathyroidectomy. The bilateral neck exploration is an added advantage
  54. 54. • Recurrent laryngeal nerve (RLN) injury: Unilateral RLN nerve injury is mostly asymptomatic as there occurs compensatory over adduction of the uninvolved cord and is typically characterized by the development of hoarseness of voice. Unopposed adduction of the cord can occur during bilateral RLN injury and leads to closure of glottis. Endotracheal intubation is a temporary relief measure and tracheostomy is a definite long term preventive measure. • Soft tissue trauma and edema: It can progress to bullous glottic edema involving the glottis and the pharynx. The onset and origin of this complication remains controversial with no definite preventive measures. • Respiratory obstruction: Respiratory obstruction can occur due to enlarging hematoma from the wound site bleeding, bilateral recurrent laryngeal nerve injury, bullous glottis edema and metabolic abnormalities.[31,32] • Renal complications: The chances of renal dysfunction are high in patients who already have some renal disease associated with hypercalcemia pre- operatively. • Post-op pain: Numerous techniques and drugs are available nowadays to alleviate even a high intensity pain. Pre-emptive analgesia and patient controlled analgesia are the new dimensions in the pain relief category which are getting very popular at present.

Notas del editor

    Explanations for select questions
    1.D False: Most common abnormality is solitary adenoma
    1.E True: Multiple Endocrine Neoplasia type 1 characterised by tumours of parathyroid, pancreas and anterior pituitary (the three P’s in the midline). Hyperparathyroidism is the most common lesion in MEN 1
    2.B False: Ionised calcium 1.0-1.25mmol/l, total calcium 2.12-2.65mmol/l
    2.C False: Calcitonin is not proven to be of major significance in humans. Calcitonin is secreted by parafollicular c cells of the thyroid in response to high serum calcium. It induces a decrease in serum calcium by inhibiting osteoclastic activity and increasing urinary excretion of calcium. Absolute absence of calcitonin (after thyroidectomy) or absolute excess (medullary carcinoma thyroid) has no major effect on calcium metabolism.
    2 D False: Absorption of calcium from the intestine is regulated by 1, 25 –Dihydroxycholecalciferol (active form of vitamin D). PTH by facilitating synthesis of vitamin D3 indirectly promotes calcium absorption.
    3 B False: Most patients present with minimal symptoms. Mostly a biochemical diagnosis picked up on routine blood tests. Subtle symptoms can be elicited on detailed history.
  • 5 D false: Carpopedal spasm on inflating the cuff is Trousseau’s sign. Chvostek’s sign is facial twitching on tapping over the facial nerve at the parotid gland.
    5 E false: Airway is not a problem preoperatively although complications like glottal oedema, recurrent laryngeal nerve damage, hypocalcaemic tetany/stridor and neck haematoma can cause problems in the post operative period
  • For any elective and majority of emergency surgeries, pre-op medical management and optimization is extremely significant for prevention of various potential peri-op and post-op complications.
  • There is no specific technique which can be considered absolutely superior. Regional anesthesia such as superficial and deep cervical plexus blockades have been used for parathyroid surgery but such techniques can be extremely hazardous in light of inadequate anesthesia and can cause numerous complications ranging from parasthesia to cardio-respiratory arrest.[18,19] There is a renewed interest in regional anaesthesia with the advent of α-2 agonists such as clonidine and dexmedetomidine which are being extensively used as adjuvants with newer local anaesthetics such as ropivacaine and articaine in neuraxial anaesthesia.[20,21,22] However, in modern day anesthesia practice, GA with tracheal intubation and muscle relaxants has been widely accepted throughout the globe.