Parathyroidectomy

What the Anesthesiologist Should Know before the Operative Procedure

Parathyroidectomy is the definitive surgical treatment for elevated levels of parathyroid hormone (PTH). PTH is the principal hormone regulating calcium hemostasis. PTH maintains serum calcium by stimulating bone resorption, thus releasing calcium, and by enhancing gastrointestinal absorption and inhibiting renal excretion of calcium. In primary hyperparathyroidism levels of PTH are excessive and hypercalcemia occurs as a consequence. Patients with hypercalcemia (total serum calcium greater than 10.4 mg/dL this value may vary slightly from one laboratory to another) can vary from relatively healthy, asymptomatic individuals to seriously ill patients with multisystem complications of chronic hypercalcemia.

There are usually four parathyroid glands, two superior and two inferior, located behind the upper and lower poles of the thyroid gland. The most common reason for parathyroidectomy is to remove a single parathyroid adenoma that is producing excess PTH. Less commonly there may be multiple adenomas, a generalized glandular hyperplasia (usually involving all four glands), or a parathyroid carcinoma. More rarely, surgery is performed for primary hyperparathyroidism that is part of a syndrome of multiple endocrine neoplasia (MEN) or for secondary hyperparathyroidism, which is a consequence of chronic renal failure.

The traditional approach is to explore all four glands, even though in about 50% of patients only one gland is abnormal. The development of imaging techniques that allow preoperative localization of the abnormal gland, and the availability of a rapid intraoperative PTH assay, to check the effectiveness of the procedure, has allowed for more focused, “minimally invasive” parathyroidectomy procedures.

1. What is the urgency of the surgery?

What is the risk of delay in order to obtain additional preoperative information?

In the past, emergent parathyroidectomy was recommended for parathyroid crisis. This condition comprised vomiting, abdominal pain, acute pancreatitis, bone pain, ECG changes, mental status changes, and even frank psychosis. In modern practice, the crisis is treated medically with rehydration (calcium free solutions), calciuresis (loop diuretic), and bisphosphonates (Alendronate). Surgery should not be performed until the acute manifestations of hyperparathyroidism have been brought under control.

Emergent: There are no indications for emergent parathyroidectomy.

Urgent: There are no indications for urgent parathyroidectomy.

Elective: Parathyroidectomy should be a planned, elective procedure and the patient’s medical condition should be optimized prior to surgery.

2. Preoperative evaluation

a. Multisystem involvement is a characteristic of hyperparathyroidism and all the following systems and conditions need to be evaluated preoperatively.

I. Renal: Polyuria, polydipsia, renal stones, decreased glomerular filtration rate (GFR)

II. Cardiac: Hypertension, ECG changes (short QT, prolonged PR interval)

III. Gastrointestinal: Abdominal pain, vomiting, weight loss, peptic ulceration, pancreatitis

IV. Musculoskeletal: Bone pain and tenderness, demineralization of skeleton (osteitis fibrosa cystica), pathological fractures (e.g., collapse of vertebrae), muscle weakness, gout

V. Neurologic: Lassitude, psychosis, muscle weakness

VI. Ophthalmic: Band keratopathy, conjunctivitis

VII. Hematologic: Anemia

VIII. Acid-base: Elevated serum calcium and chloride, decreased bicarbonate and phosphorous, metabolic acidosis.

Medically unstable conditions warranting further evaluation include severe hypercalcemia (levels greater than 14 mg/dL), which requires urgent treatment. Patients may also have acute pancreatitis, pathological fractures, vomiting, dehydration, peptic ulceration, or hypertension, which require preoperative treatment and stabilization.

Delaying surgery may be indicated if the patient has any unstable medical condition than can be optimized before surgery.

3. What are the implications of co-existing disease on perioperative care?

N/A

b. Cardiovascular system

Perioperative Evaluation

Acute/unstable conditions:

Patients may be dehydrated and have anemia. The true severity of the anemia may be masked by the concomitant dehydration.

Baseline coronary artery disease or cardiac dysfunction – Goals of management:

Most patients with hyperparathyroidism present in the third to fifth decade of life and so coronary artery disease is not common. There are often ECG changes and short QT and prolonged PR intervals. A minority of patients have associated hypertension, which usually resolves with treatment of the underlying disease. In the rare circumstance of long-standing chronic hypercalcemia, there may be calcifications in the myocardium itself.

Perioperative risk reduction strategies

Monitoring: Usually standard ASA monitoring is sufficient.

Goals: Optimize perioperative hydration and correct anemia. Use normal saline for hydration and consider furosemide to increase calcium excretion if renal function adequate.

c. Pulmonary

Pulmonary disease is not specifically associated with this disease.

d. Renal-GI:

Perioperative Evaluation

• Dehydration may be secondary to polyuria, anorexia, and/or vomiting.

• Renal stones occur in 60-70% of patients.

• Chronic anemia is common.

• Acute pancreatitis and peptic ulcer disease may be present.

• Laboratory testing: BUN, creatinine, and hemoglobin

• Chronic renal insufficiency (CRI): GFR is often decreased. In addition, chronic renal insufficiency may be the actual cause of the hyperparathyroidism (secondary hyperparathyroidism).

Perioperative risk reduction strategies

• Correct dehydration and anemia.

• Goals: Optimize perioperative hydration and correct anemia. Use normal saline for hydration and consider furosemide to increase calcium excretion if renal function adequate.

e. Neurologic:

Acute issues: Rarely patients with intracerebral calcifications may present with seizures.

Chronic disease: Lethargy and depression are common. There may be psychomotor retardation and muscle weakness.

f. Endocrine:

N/A

g. Additional systems/conditions which may be of concern in a patient undergoing this procedure and are relevant for the anesthetic plan (eg. musculoskeletal in orthopedic procedures, hematologic in a cancer patient)

N/A

4. What are the patient's medications and how should they be managed in the perioperative period?

Cardiac medications: Patients may be taking antihypertensive medications. Beta-blockers should be continued until the time of surgery others should be managed according to hospital policy.

Diuretics:Furosemide is commonly used to decrease calcium levels and should be continued until the time of surgery.

Bisphosphonates: Many patients will have decreased bone density due to excessive bone resorption. Bisphosphonate drugs, such as Alendronate (Fosamax), are administered to counteract the bone loss and to increase bone density.

Cinacalcet lowers calcium by inhibiting production of PTH.

Glucocorticoids are sometimes used to counter the effects of vitamin D. They should not be withdrawn abruptly before surgery.

Calcitonin: This is a natural hormone that counteracts the effects of PTH. It stimulates osteogenesis and movement of calcium into bones. It is administered intravenously to rapidly lower severely elevated levels of serum calcium (>14 mg/dL).

h. Are there medications commonly seen in patients undergoing this procedure and for which should there be greater concern?

Rarely, IV mithramycin is used to lower calcium in an emergent situation. It blocks the osteoclastic effect of PTH. It is a toxic drug that carries the risk of thrombocytopenia and liver and renal injury.

i. What should be recommended with regard to continuation of medications taken chronically?

Cardiac:Patients may be taking antihypertensive medications. Beta-blockers should be continued until the time of surgery others should be managed according to hospital policy.

Endocrine:All medications for treatment of hypercalcemia and associated symptoms should be continued until the time of surgery. This includes beta-blockers, diuretics, bisphosphonates, and proton pump inhibitors.

Renal: Furosemide is commonly used to decrease calcium levels and should be continued until the time of surgery.

Neurologic: Antiepileptic drugs should be continued.

Psychiatric: Continue antidepressant and antipsychotic medications until time of surgery.

Herbals: According to hospital policy.

j. How To modify care for patients with known allergies –

N/A

k. Latex allergy- If the patient has a sensitivity to latex (eg. rash from gloves, underwear, etc.) versus anaphylactic reaction, prepare the operating room with latex-free products.

N/A

l. Does the patient have any antibiotic allergies? (common antibiotic allergies and alternative antibiotics)

N/A

m. Does the patient have a history of allergy to anesthesia?

Malignant hyperthermia (MH)

Documented: Avoid all trigger agents such as succinylcholine and inhalational agents,

• Proposed general anesthetic plan, total intravenous anesthesia

• Ensure MH cart available: [MH protocol]

• Family history or risk factors for MH

5. What laboratory tests should be obtained and has everything been reviewed?

a. Hemoglobin levels: Patients are frequently anemic so a preoperative hemoglobin is mandatory.

b. Electrolytes:

• Calcium: In primary hyperparathyroidism total serum calcium will be elevated above 10.4 mg/dL. This value may be lower if serum albumin is significantly decreased for any reason. Alternatively, ionized calcium, which is independent of albumin, may be measured. In secondary hyperparathyroidism, calcium may be decreased due to renal losses.

• Potassium: Patients may be on potassium-wasting diuretics or hemodialysis.

• Sodium and chloride: Both may be increased.

• BUN/creatinine: Patients may have some degree of renal dysfunction.

• Bicarbonate, magnesium, and phosphorous: All may be decreased.

c. Coagulation panel: Not specifically indicated.

d. Imaging: Technetium-99m-sestamibi scintigraphy has improved the ability to localize hyperactive parathyroid tissue preoperatively. This may allow for more focused surgery on a single gland.

e. Other tests: Elevated levels of PTH establish the diagnosis of hyperparathyroidism.

Intraoperative Management: What are the options for anesthetic management and how to determine the best technique?

The great majority of these procedures are performed under general anesthesia.

a. Regional anesthesia

Peripheral nerve block

Superficial cervical plexus nerve block can be performed with low risk. Deep cervical plexus block is not justified.

• Benefits: Can be helpful for postoperative pain control with unilateral procedures.

• Drawbacks: Bilateral blocks are contraindicated because of the large volumes of local anesthetic that would be required.

• Issues: May be combined with supplementation in the surgical field to allow the procedure to be performed with monitored anesthesia care.

b. General Anesthesia

• Benefits: Most patients and surgeons prefer general anesthesia and the airway is secured.

• Drawbacks: Coughing on the endotracheal tube will increase venous pressure may promote hematoma formation.

• Other issues: Endotracheal intubation with a special endotracheal tube is necessary for EMG monitoring of recurrent laryngeal nerve function.

c. Monitored Anesthesia Care

• Benefits: May be used in combination with cervical plexus block for unilateral minimally invasive surgery

• Drawbacks: Airway not protected.

• Other Issues: Restricted to unilateral minimally invasive procedures.

6. What is the author's preferred method of anesthesia technique and why?

The preferred technique of anesthesia is a product of patient, anesthesia provider, and surgeon preference. In the author’s institution, general anesthesia with endotracheal intubation is the norm. Patients are premedicated with midazolam, 1-2 mg IV in the preoperative holding area. For healthy patients, standard ASA monitors only are used. Additional monitors are used according to the patient’s medical status. Induction is with propofol and fentanyl and neuromuscular block for intubation is with rocuronium. On occasion, a special endotracheal tube modified to permit electromyographic evaluation of laryngeal nerve function is placed. Additional neuromuscular blocking drug is not administered. Anesthesia is maintained with propofol infusion, plus desflurane or sevoflurane, and supplementary opioid.

Commonly venous blood is drawn to measure PTH levels during the procedure. If the original IV catheter allows for blood sampling then that alone is sufficient. If necessary for blood sampling, a second IV catheter is inserted.

Antiemetic prophylaxis is important to prevent retching in the postoperative period. In addition to the propofol infusion, dexamethasone 4 mg is administered at the beginning of the procedure, and ondansetron 4 mg at the end. If the patient is at increased risk for postoperative nausea and vomiting (PONV) or has a history of protracted PONV, preoperative placement of a transdermal scopolamine patch and/or oral application of aprepitant prior to induction of anesthesia should be considered.

Residual neuromuscular block is reversed with neostigmine 20-40 mcg/kg of body weight together with an appropriate dose of glycopyrrolate.

Postoperatively, the patient is monitored in a setting where serious complications such as neck hematoma can be quickly recognized and treated. Regular measurement of the neck circumference may be indicated (“wet-neck-protocol”).

Not all surgeons use prophylactic antibiotics for what is a procedure with a very low infection risk. If prophylactic antibiotics are used, then the SCIP recommendation is for intravenous cefazolin given within 60 minutes prior to skin incision.

The surgical procedure

The traditional approach is to use a transverse neck incision, centered on the midline. This allows exploration of all four parathyroid glands, and is necessary if there is bilateral disease, generalized hyperplasia, or parathyroid cancer. On occasion, extension of the operation farther into the neck or into the thymus gland is necessary to find aberrant parathyroid tissue.

Some surgeons use a minimally invasive approach with a unilateral incision only. This is appropriate for surgery on a single active adenoma that has been localized preoperatively.

A few surgeons perform endoscopic, or video-assisted parathyroidectomy. This may involve the use of gas insufflation into the field with risk of gas embolization or subcutaneous emphysema.

What can I do intraoperatively to assist the surgeon and optimize patient care?

Some surgeons use electrical stimulation to identify the recurrent and superior laryngeal nerves. To enable this, the anesthesia provider inserts a special endotracheal tube that has wires on the outside at the point where the tube lies between the vocal cords. The anesthesia provider has to make sure that the tube is positioned correctly, and that there is no neuromuscular block during the procedure.

Most surgeons measure PTH before and at 5 and 10 minutes after the excision of the parathyroid. With a successful surgery, levels of PTH should fall by 50% by 10 minutes. The anesthesia provider is usually asked to draw these samples and should plan venous access accordingly. Alternatively, the surgeon can draw the samples from the internal jugular vein, which is within the surgical field.

What are the most common intraoperative complications and how can they be avoided/treated?

Intraoperative complications with traditional approaches are rare.

With endoscopic surgery, gas embolism and subcutaneous emphysema are possible.

Tracheal extubation provides particular challenges. It is important to minimize coughing and bucking to limit venous pressure in the neck and decrease the chance of hematoma formation. If there has been any possibility of laryngeal nerve injury the anesthesia provider may be asked to assess vocal cord function immediately after extubation. This requires that the patient is breathing spontaneously yet is sufficiently anesthetized to tolerate direct or video laryngoscopy.

Neurologic complications: Toxic metabolic encephalopathy is a rare complication. It is associated with methylene blue administration for preoperative gland localization in patients taking serotonin reuptake inhibitors.

a. Neurologic:

N/A

b. If the patient is intubated, are there any special criteria for extubation?

Avoid coughing and bucking.

c. Postoperative management

What analgesic modalities can I implement?

Simple intravenous analgesia with morphine or hydromorphone is usually all that is required.

What level bed acuity is appropriate?

Much will depend on the surgical technique (traditional versus minimally invasive), and the patient’s underlying medical condition. Patients considered at risk for a postoperative neck hematoma (“wet-neck”) need to be monitored in a high acuity setting.

What are common postoperative complications, and ways to prevent and treat them?

Sore throat is almost universal there is no effective prevention.

Recurrent laryngeal nerve injury can occur.

• If unilateral, it may be asymptomatic.

• If bilateral, it can lead to acute airway obstruction after tracheal extubation and may require reintubation.

• A permanent tracheostomy may be required if the paralysis persists.

Hypocalcemia may occur and presents with muscle spasms, laryngospasm, tetany, apnea, or paresthesias. It is treated with slow intravenous injection of calcium gluconate 1000 mg, repeated as necessary. This complication is most likely following surgery for generalized hyperplasia when only a small (and inadequate) portion of one gland is retained.

Neck hematoma is uncommon, but can produce life-threatening airway obstruction. The anesthesia provider should do all he or she can do to minimize coughing and bucking during emergence and extubation. Patients considered at risk for hematoma should be monitored in a high acuity unit where a developing hematoma can be rapidly recognized.

Toxic metabolic encephalopathy is a rare complication. It is associated with methylene blue administration for preoperative gland localization in patients taking serotonin reuptake inhibitors.

What's the Evidence?

WHAT THE ANESTHESIOLOGIST SHOULD KNOW BEFORE THE OPERATIV PROCEDURE

Phitayakorn, R, McHenry, CR. “Parathyroidectomy: overview of the anatomic basis and surgical strategies for parathyroid operations”. Clin Rev Bone Miner Metab. vol. 5. 2007. pp. 89-102. (This provides an authoritative review of the surgical literature.)

WHAT IS THE URGENCY OF THE SURGERY?

Phitayakorn, R, McHenry, CR. “Hyperparathyroid crisis: use of bisphosphonates as a bridge to parathyroidectomy”. J Am Coll Surg. vol. 206. 2008. pp. 1106-15. (This provides the evidence that parathyroidectomy should be performed only after medical treatment has stabilized the patient's condition.)

PREOPERATIVE EVALUATION

Shroff, P, Kudalkar, A, Kamath, S. “Anesthetic management of parathyroidectomy: retrospective analysis-15 years.”. Bombay Hosp J . 2006. (This is the most recent and extensive review of anesthesia for parathyroidectomy.)

INTRAOPERATIVE MANAGEMENT: PERIPHERAL NERVE BLOCKS

Snyder, SK, Robertson, CR, Cummings, CC, Rajab, MH. “Local anesthesia with monitored anesthesia care versus general anesthesia in thyroidectomy: a randomized study”. Arch Surg. vol. 141. 2006. pp. 167-73. (This provides a justification for using peripheral nerve block and monitored anesthesia care in selected patients.)

WHAT DO I NEED TO KNOW ABOUT THE SURGICAL PROCEDURE TO OPTIMIZE MY ANESTHESIA CARE?

Grant, CS, Thompsonn, G, Farley, D, van Heerden, J. “Primary hyperparathyroidism surgical management since the introduction of minimally invasive parathyroidectomy: Mayo Clinic experience”. Arch Surg. vol. 140. 2005. pp. 472-8. (This is a good review of more recent surgical approaches to parathyroidectomy.)

WHAT CAN I DO INTRAOPERATIVELY TO ASSIST THE SURGEON AND OPTIMIZE PATIENT CARE?

Snyder, SK, Hendricks, CR. “Intraoperative neurophysiology testing of the recurrent laryngeal nerve: plaudits and pitfalls”. Surgery. vol. 138. 2005. pp. 1183-91. (A good review and evaluation of what has become a de facto monitoring standard.)

POSTOPERATIVE MANAGEMENT

Shopes, E, Gerard, W, Baughman, J. “Methylene Blue Encephalopathy: A Case Report and Review of Published Cases”. AANA Journal. vol. 81. 2013. pp. 215-21. (A good description of a severe complication that may not be widely recognized.)

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