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FREE FLAP CHECKS

Overview
Free tissue transfer for reconstruction of large or complex defects of the head and neck is commonly employed at most tertiary care centers. It is the responsibility of the entire care team to ensure appropriate monitoring of the flap and donor site to prevent and detect complications that could jeopardize flap viability or overall clinical outcome. Approximately 10% of flaps may require revision surgery for flap salvage, although overall success rates exceed 95%. Vascular pedicle thrombosis is the most common cause of flap failure and occurs most commonly in the first 48 hours following surgery. Reasons for vascular pedicle compromise include venous thrombosis (most common), arterial thrombosis, anastomosis rupture, torsion of the flap pedicle with subsequent reduced flow, external compression of the vessels from hematoma or other sources, and microthrombi in the capillaries and venules of the flap itself.

 

Early identification of problems with flap vascularity greatly increases the likelihood of successful salvage, and in general cases of flap vascular compromise should be treated as surgical emergencies. The color, turgor, warmth, and appearance of the flap are key components of every flap check; adjunctive measures include Doppler evaluation of the arterial and venous signals of the pedicle as well as pinprick or scratch testing of the flap skin paddle to assess bleeding. Venous compromise is more common than arterial and is suggested by a congested or boggy appearing flap that may be purple, blue, edematous, or mottled, or bleeds dark purple or black blood when pricked. Arterial loss typically will lead to loss of flap turgor and warmth, a pale appearance, and absence of bleeding with pinprick. Any concerns regarding flap viability or complications should immediately be conveyed to senior residents or attendings to facilitate timely management. The basics of flap checks apply across any free tissue transfer regardless of donor site, although it is the responsibility of the resident to understand the specific donor site potential morbidities and complications.

 

Common Free Flaps of the Head and Neck

 

Radial Forearm

The radial forearm is a workhouse flap of small defects of the head and neck and especially oral cavity. It is typically used as a fasciocutaneous flap, although it may be used as an osteocutaneous flap by including partial thickness radius for bony reconstruction. The neurovascular pedicle is composed of the radial artery, paired venae comitantes, the cephalic vein, and the lateral antebrachial cutaneous nerve that courses near the cephalic vein. The lateral antebrachial cutaneous nerve may be used for nerve anastomosis if sensory innervation of the graft is desired. The Allen test preoperatively is critical to confirm palmar arch patency and sufficient blood flow to the thumb and index finger from the ulnar artery alone. A skin graft is nearly always required for closure, and following reconstruction, the wrist is typically immobilized in a volar splint to prevent shearing forces. Casting past the elbow may be used if an osteocutaneous flap is harvested to minimize movement. Donor site checks on these patients should include finger warmth, finger capillary refill, and finger sensation and movement.

 

Fibula

The fibula osteocutaneous flap, based off the peroneal artery and vein, is now the most common osteocutaneous flap used for head and neck reconstruction of bony defects. There are multiple advantages to fibula free flaps including the ease of a two-team surgical approach, a relatively long and predictable vascular pedicle, and a thin yet long and dense harvestable bone segment that can allow for osseointegrated implant placement. Downsides of the fibula free flap include the potential destabilization of the ankle (thus requiring preserving the distal 5-7 cm of the fibula at the ankle joint during elevation) and risk to the common peroneal nerve that enables dorsiflexion of the foot (although this can be avoided by ensuring superior extent of skin incision is at least 5 cm from the fibula head). Additionally, the skin and soft tissue paddle is commonly relatively small, thus unsuitable for large soft tissue defects. Harvest site wound closure often requires skin grafting to lower risk of postoperative compartment syndrome. Preoperative vascular evaluation with doppler, CT or MR angiography, or conventional angiography to ensure normal vascular supply to the foot will preserve perfusion following peroneal artery harvest. The leg and ankle are stabilized after fibula free flap harvest with a temporary cast or walking boot, typically with gradual return to weight bearing status in 1-2 weeks postoperatively with the assistance of physical therapy. Donor site checks on these patients should include foot warmth (compare graft side to the other foot), capillary refill of the toes, and toe sensation and movement.

 

Anterolateral Thigh

The anterolateral thigh flap, typically based on the descending branch of the lateral femoral circumflex artery (branching off the profunda femoral artery), is commonly used to reconstruct large soft tissue defects of the head or neck. It shares many similarities to radial forearm free flaps: Predictable vascular pedicle and pliable soft tissue with the possibility for sensory innervation (through the lateral femoral cutaneous nerve) but is a larger and thicker graft with less donor site morbidity. The flap is often elevated including portions of the vastus lateralis and/or with the motor nerve to vastus lateralis harvested as an interposition graft (although this does cause some morbidity to the leg). The primary disadvantages of the anterolateral thigh flap are a short vascular pedicle and the variable skin perforator location and small size, which can make raising the flap technically challenging and time-consuming (although retrograde perforator dissection has circumvented this disadvantage to a degree). The skin and subcutaneous tissue of the graft are variable in thickness from individual to individual and should always be assessed preoperatively to ensure appropriateness of tissue bulk for the defect. Donor site defects less than 8-9 cm wide are typically closed primarily, although skin grafting or wound VAC placement may be used. Donor site checks on these patients should include foot warmth (compare graft side to the other foot), capillary refill of the toes, and toe sensation and movement.

 

Latissimus Dorsi

The latissimus dorsi flap, based off the thoracodorsal artery and vein, may be used for free tissue transfer or as a pedicled flap for reconstruction of the head or neck. The thin muscle makes the flap especially suitable for cranial and scalp defects while pedicled flaps may be useful when the availability of suitable vessels for anastomosis is doubtful, although reach can be limited. Disadvantages of this flap include needing lateral decubitus positioning, making a two-team surgical approach challenging, high incidence of postoperative seroma, and donor site morbidity (reduced shoulder range of motion). Postoperative care should include early shoulder mobilization exercises with physical therapy and occupational therapy. Because of the size of the latissimus, a hematoma in the wound bed could lead to a significant amount of blood loss.

 

Scapula

The scapula flap is based off the circumflex scapular branch of the subscapular artery and may be harvested as either a fasciocutaneous or osteocutaneous flap. It is most commonly used in an osteocutaneous fashion for bony reconstruction of the midface or mandible. Because of the branching of the subscapular system, this flap can be combined with the latissimus flap (mega flap), which allows both bony reconstruction and large volume soft tissue reconstruction (an advantage over fibula flaps where there is limited soft tissue available). Similar to the latissimus flap, a hematoma in the donor site could lead to a significant amount of blood loss.

 

Gracilis

Based off the adductor artery, the gracilis flap is used primarily for dynamic facial reanimation using the gracilis branch of the obturator nerve. It is rarely used with a skin paddle due to the small size and variable perforators, although this has been described. The muscle is usually thinned significantly based on weight and often separated to create multiple vectors of contractibility. These are typically muscle-only buried flaps; therefore, flap checks may be limited to overlying skin exam and implantable versus external doppler or ultrasound evaluations. The nerve to masseter is commonly used as the source for motor innervation. Alternatively, a two-step procedure with prior cross facial nerve transfer can allow eventual voluntary control of the flap contraction. Donor site morbidity is typically minimal with this flap, although the incision should be checked, and no hematoma or seroma collection ensured.

 

Key Supplies for Free Flap Checks

  • Appropriate PPE including mask, eye protection, gloves, and gown

  • Headlight or pen light

  • Tongue depressor and suction with Yankauer tip for intraoral flaps

  • 25- or 27-gauge needle

  • Doppler ultrasound (both portable/pencil Doppler and implantable Doppler monitor if applicable)

 

Management

  • Most academic institutions will have a standardized postoperative flap protocol with respect to frequency of flap checks, the team members involved in flap checks, and basic postoperative care.

  • Admitting unit: Some institutions may routinely admit flap patients to the ICU after surgery. In the setting of closed unit ICUs (i.e., where the ICU team is responsible for writing orders and managing the patient minute by minute), clear communication with the ICU team is critical as they may not always be familiar with the ENT service’s protocols.

  • Positioning: This may include elevating the head of bed 30 degrees, positioning the head in a particular direction to prevent kinking or putting tension on the pedicle, avoiding large pillows under the head to prevent neck flexion, and avoiding circumferential neck ties or dressings to prevent external compression of the vascular anastomosis. Be familiar with these protocols to ensure adherence to this during flap checks. Often, the operated extremity is also elevated (e.g., on 2-3 pillows) to prevent edema that can lead to compression of remaining distal vascular supply.

  • Flap checks: These are typically performed overnight by the on-call ENT resident as well as Nursing staff, although each institution has its own policy and the timing and frequency will vary based on institution as well. It is prudent for the on-call resident to examine the flap at the end of surgery or in the immediate postoperative period with a member of the surgical team. The on-call resident should review the anatomy of the flap including the anastomosed vessels and note the most distal site of the flap in relation to the vascular pedicle. This baseline exam will then serve as a reference upon which to compare future exams.

  • Flap check steps:

    • Review and know the patient’s past medical history with attention to major comorbidities, prior head and neck cancer treatment including radiation, as well as details from surgery (e.g., vessels used in anastomosis, difficulties that arose during the case, etc.).

    • Assess vitals to ensure hemodynamic stability and adequate mean arterial pressure.

    • Ensure positioning is appropriate based on institutional guidelines.

    • Ensure adequate visualization of the flap with the assistance of a headlight, tongue depressor, and/or suction if needed.

    • Observe flap appearance and color.

    • When present and visible, a well-perfused flap skin paddle should match the color of the patient’s skin at the donor site and have pink undertones. With brief pressure, there should be capillary refill after blanching. Blue or purple discoloration is concerning for venous congestion, while pallor and absence of capillary refill is concerning for arterial compromise. Bruising or ecchymosis of the skin paddle, especially with flap swelling, is concerning for a hematoma under the flap. Palpate the flap feeling for warmth and turgor. A tense, plethoric, or boggy flap suggests venous congestion, whereas a cold and flaccid flap suggests arterial insufficiency.

    • Listen to implantable Doppler signal if present or portable external Doppler probe.

      • If using a portable Doppler, the Doppler should be lubricated with ultrasound gel and gently positioned over the site of the anastomosis until a Doppler signal is heard, or over a perforator or distal vascular pedicle beneath the skin paddle. In some cases, a marking stitch may be placed on the skin paddle intraoperatively at the site of the best Doppler signal to guide future flap checks. Note: If using a portable Doppler to listen for a signal in the neck, be sure you are not listening to the carotid artery rather than the pedicle. (If the pedicle is situated in the midline, this is often a good location to be sure you are not picking up carotid.)

      • A normal arterial Doppler signal is a triphasic waveform, which includes rapid anterograde flow reaching a peak during systole, transient reversal of flow during early diastole, and slow anterograde flow during late diastole. The first and third phases of the Doppler signal should be crisp and loud. A water hammer pulse characterized by an abrupt, very rapid upstroke followed by rapid collapse may be a sign of venous congestion. An absent Doppler signal suggests arterial insufficiency. Venous doppler signals should have a constant venous hum with respiratory variation and may require temporarily laying the head of bed flatter or gentle distal venous finger occlusion to backfill the vein enough to appreciate venous signal variation and differentiate from background artifact.

    • Piercing (or “sticking”) a flap to assess for bleeding may be performed routinely or only when there is concern for flap compromise. Institutional policy may require notifying the supervising physician prior to performing.

      • Prick: Use a 25- or 27-gauge needle to prick the skin paddle superficially and peripherally, leaving the needle in place for a second and gently twisting before withdrawing. In a well-perfused flap, bright red blood should appear after about 1-5 seconds; immediate return of dark blood suggests venous congestion, whereas absence of any bleeding suggests arterial insufficiency.

      • Scratch: Alternatively, a 15-blade scalpel or the tip of an 18-gauge needle can be used to make a small partial dermal incision in the skin paddle and examining for bleeding as described above.

    • Strip drains and note if holding suction and volume since last check and assess the quality of the fluid (e.g., serous, serosanguinous, frank blood, etc.).

    • Review labs (most patients will have at least daily CBC and BMP) to evaluate for elevation in white count, decrease in hemoglobin and hematocrit, and fluctuations in Na+, K+, and Ca2+ (the most common electrolyte abnormalities in free flap patients).

    • Review fluid intake and outputs (third spacing and edema increase risk of flap compromise) and follow your institutional policy regarding fluid balances. If mean arterial pressures are low, consider notifying senior resident or consultant prior to fluid boluses and especially prior to consideration of vasopressors.

    • Review medications:

      • Antithrombotic therapy: Most microvascular surgeons will start an antithrombotic medication postoperatively. This is most commonly aspirin, although the dose or the medication may vary based on surgeon preference.

      • DVT prophylaxis: Commonly with heparin or low molecular weight heparin such as Lovenox®.

      • Antibiotics: These will often be continued in the perioperative period for a variable amount of time for any upper aerodigestive tract flap, or potentially longer in cases of osteoradionecrosis.

      • Proton pump inhibitors may be used routinely after free flaps in the upper aerodigestive tract.

      • If there is suspicion of any vascular compromise, contact your senior resident, fellow, or supervising attending as soon as possible. Time is flap! Prolonged ischemic time results in non-reversible microcirculatory collapse (“no re-flow” phenomenon).

  • Generally, there is a low threshold to return to the OR for reexploration as early surgical intervention results in higher salvage rates.

  • Non-surgical methods may be considered to improve blood flow or decrease venous congestion. These include leech therapy and low dose nitroglycerin ointment.

    • Leeches may alleviate venous congestion by producing the natural anti-coagulant hirudin in their saliva. One or two leeches can be applied at a time to the congested area and should be watched until they latch onto the skin and left in place until they are done feeding and detach on their own. The flap should leak dark venous blood after the leech falls off. Leeches will not attach on areas that have ointment. Ensure accountability of leeches. All patients undergoing leech therapy should be started on an antibiotic with activity against Aeromonas hydrophila. Often a fluoroquinolone such as levofloxacin is used. Hematocrits should be checked in patients undergoing leech therapy every 8 hours.

    • Low dose nitroglycerin ointment may also be applied twice daily to improve perfusion through vasodilation but should not be applied to overlapping areas intended for leech therapy as leeches will not feed if nitroglycerin ointment is on the surface.

 

Example Flap Check Note

Fibula Free Flap

___ year old patient who underwent a right fibula free flap reconstruction of an anterior mandibular defect on ___. The intraoperative course was uncomplicated with an ischemic time of 170 minutes. The peroneal artery was anastomosed to the left facial artery with placement of a Cook-Swartz Doppler on the arterial vessel. The venae comitantes were anastomosed to the left external jugular vein and the left facial vein in an end-to-end fashion. A tracheostomy was performed with an 8-0 cuffed Shiley™ tracheostomy tube sutured in place. The patient was left sedated overnight.

 

Physical Exam:

Vitals:

General: Sedated and not responding to questions.

Flap: Intraoral skin paddle warm and soft to palpation. The de-epithelized portion bled bright red when rubbed with a swab. The Cook-Swartz Doppler had a strong arterial signal. The flap edges were well apposed with suture.

Neck: Tracheostomy tube well positioned. No circumferential neck ties in place. Mild expected postoperative edema without any palpable hematoma. Jackson-Pratt (JP) drains x 2 in place with serosanguinous output.

Leg: Right leg elevated, in cast. Toes warm with a 2 second capillary refill. Dorsalis pedis pulse present. Right leg JP with sanguinous output.

Drain Output:

JP 1 neck: ___

JP 2 neck: ___

JP 3 leg: ___

 

Assessment: Patient now status post right fibula free flap reconstruction on anterior mandibular defect without signs of flap compromise.

·    First dose of aspirin tonight (per rectum), then daily per nasogastric tube.

·    Continue resident flap checks every ___.

·    Continue Nursing flap checks every ___ hours for ____ days.

·    No vasopressors without ENT notification.

·    Continue current maintenance IV fluids; no boluses without ENT notification.

·    Unasyn® IV for 24 hours postoperatively.

·    Chlorhexidine oral rinse and gentle oral care 3 times daily by Nursing.

·    Strip and record drain output every 2 hours.

·    NPO; please use nasogastric tube (or gastrostomy tube) for medication once radiographically cleared for use.

 

References
1. Başaran, B., Ünsaler, S., Kesimli, M.C., et al. (2021). Free flap reconstruction of the head and neck region: A series of 127 flaps performed by otolaryngologists. Turk Arch Otorhinolaryngol. 59(2):103-110.
2. Chepeha, D.B. (2013). Reconstructive Microsurgery of the Head and Neck. In Johnson, J.J., Rosen, C.A. (Eds.), Bailey’s Head and Neck Surgery-Otolaryngology 5e (pp. 2824-2848). Baltimore, MD: Lippincott Williams & Wilkins.
3. Hoffman, H., Elliott, S., Klein, K. (2019). Free Flap Monitoring and Salvage. Iowa Head and Neck Protocols, https://medicine.uiowa.edu/iowaprotocols/free-flap-monitoring-and-salvage.
4. Ishimaru, M., Ono, S., Suzuki, S. (2016). Risk factors for free flap failure in 2,846 patients with head and neck cancer: A national database study in Japan. J Oral Maxillofac Surg. 74(6):1265-1270.
5. Novakovic, D., Patel, R.S., Goldstein, D.P., et al. (2009). Salvage of failed free flaps used in head and neck reconstruction. Head Neck Oncol. 1:33.
6. Bank, J., Gottlieb, L.J. (2017). Flap Re-exploration and Salvage. In Wei, F.C., Mardini, S. (Eds.), Flaps and Reconstructive Surgery 2e. (pp. 333-47). Philadelphia, PA: Elsevier.
7. Sanati-Mehrizy, P., Massenburg, B.B., Rozehnal, J.M., et al. (2016). Risk factors leading to free flap failure: Analysis from the national surgical quality improvement program database. J Craniofac Surg. 27(8):1956-1964.
8. Zhu, Z., Wang, X., Huang, J., et al. (2018). Mechanical versus hand-sewn venous anastomoses in free flap reconstruction: A systematic review and meta-analysis. Plast Reconstr Surg. 141(5):1272-1281.

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POSTOPERATIVE HEMATOMA

Overview
Postoperative hematoma, a collection of clotted or partially clotted blood within the operative bed, is among the most common postoperative complications in Otolaryngology. Most cases occur without an apparent underlying risk factor; however, several factors have been found to increase the probability of this complication including male sex, older age, smoking, diabetes, antiplatelet therapy, anticoagulation, underlying hepatorenal insufficiency, congenital or acquired thrombophilic conditions, and certain surgeries. Basic methods to reduce the risk of postoperative hematoma include meticulous operative hemostasis, judicious drain placement and postoperative drain management, and use of a compression dressing in some circumstances. Signs of hematoma formation chiefly include fluctuant or firm expansion of tissue surrounding the confines of the operative space with or without surrounding ecchymosis and with or without pain. To mitigate confusion by the floor nurse or overnight on-call resident, thoroughly communicate the appearance of the surgical site after complex tissue reconstruction, as a vascular pedicle (e.g., pectoralis major myocutaneous flap) or excess flap bulk (e.g., anterolateral thigh flap) may have a similar appearance and generate concern for hematoma formation. It is also important to consider other overlapping conditions that may present in a similar manner. For example, a seroma may develop in a delayed fashion (>1 week after surgery) in larger operative defects, abscess formation may develop de novo or within a pre-existing hematoma but usually occurs more than several weeks after surgery, and pseudomeningoceles may develop in any skull base procedure that communicates with the subarachnoid space at any time after surgery. Broadly, high risk hematomas that require emergent evaluation and management include:

 

  • Expanding neck hematomas, particularly after thyroidectomy; risk of airway compression.

  • Hematomas occurring after free-tissue transfer; risk of vascular pedicle compromise.

  • Hematomas within an operative bed communicating with the intracranial space; risk of life-threatening brain compression.

  • Hematomas in an extremity after free-tissue transfer harvest; risk of peripheral limb ischemia.

  • Hematomas in very large dead space (e.g., latissimus free flap or pectoralis muscle harvest sites); risk of significant blood loss.

  • Hematomas under significant tension; risk of overlying skin necrosis.

  • Septal or auricular hematomas; risk of cartilage ischemia and necrosis.

 

Key Supplies for Postoperative Hematoma Consultation

  • Appropriate PPE including mask, eye protection, gloves, and gown

  • Headlight

  • Normal saline bottles, piston syringe or other large syringe with Angiocath®, or red rubber catheter for wound irrigation

  • Iodine swabs

  • 18- and 27-gauge needles with 3 mL syringes for local anesthesia

  • Gauze, fluffs, and kidney basin for collecting evacuated blood

  • Laceration tray with forceps, needle driver, Kelly/tonsil clamp, and scissors

  • 15-blade scalpel

  • Suction

 

Management

  • First, globally examine the patient to evaluate for signs of respiratory distress or pain; evaluate the ABCs (Airway, Breathing, Circulation) in any case that may result in critical airway compression.

  • If the patient is hypotensive, diaphoretic, or concerningly tachycardic, or you suspect a large volume of blood loss based on the wound size, consider obtaining a CBC, type and cross, and coagulation panel.

  • Carefully examine the site of concern, looking for fluctuance (e.g., wave-like or boggy feeling upon palpation), tenseness (e.g., soft or firm), skin color changes (e.g., surrounding ecchymosis or blanching), or wound dehiscence.

  • After initial evaluation, the first decision to be made is whether the hematoma needs to be evacuated emergently at the bedside or whether transport to the OR is appropriate. In some cases, minor hematomas may be evacuated non-emergently at the bedside without transport to the OR.

  • High risk hematomas (as defined above) should always be ultimately addressed in the OR; however, they may require bedside evacuation to start if the benefits of doing so outweigh the risks of waiting for an OR to become available. Examples of this include impending airway compromise, signs of free flap compromise, or hematomas causing overlying skin ischemia or peripheral limb ischemia. If a neck hematoma is large enough or has been present long enough, it may lead to generalized upper airway edema due to compression of the microcirculation. This can lead to continued airway compromise due to edema after hematoma evacuation at the bedside and should be kept in mind as plans for transport to the OR are made.

  • For non-emergent hematomas, or hematomas that have been first evacuated at bedside, definitive treatment usually includes a “take back” to the OR for wound exploration, hemostasis, probable drain (re)placement, and reclosure; depending on the perceived risks of rebleed, adjuncts such as fibrin glue, Surgicel®, or other hemostatic products can be considered at the time of wound exploration; compression dressing or compression binders may also be used in some circumstances but are generally avoided around the neck or adjacent free flap vascular pedicle and anastomosis.

  • If applicable, determine whether associated drains are functioning appropriately and determine recent drain output.

    • If the drains are not holding suction, try to identify the source of the leak, which most typically occurs where the drain enters the skin; a strategically placed stich, adjustment of the drain as it enters the skin, or application of an occlusive ointment (such as petroleum-based ointment) or Tegaderm® on the drain hole or incision will often correct the problem.

    • If the drains are clogged with clot, attempt to carefully strip the tubing by sliding it tightly between your thumb and index finger from proximal to distal; oftentimes it is difficult to effectively evacuate blood from a surgical site hematoma through a drain or via needle aspiration because of clot formation; always check the drain stitch to make sure it is not too tight around the tubing as an underlying cause.

  • Hematoma formation after septoplasty or auricular surgery (e.g., microtia or otoplasty) is generally best managed by early clot evacuation and bolster placement, Penrose drain placement, or packing, depending on the size and location.

  • For very mild or low risk hematomas, observation with or without compression or attempted needle aspiration can be considered, understanding the risk of secondary hematoma infection; if choosing observation, it may be beneficial to mark a line around the perimeter of the hematoma to document any potential progression; may consider prophylactic antibiotics if observing a hematoma or if using a bolster or splint through cartilage.

  • Patients with a large volume of blood loss may require transfusion, particularly in the setting of free tissue transfer surgery; reversal or correction of any underlying coagulopathy should be considered based on clinical context.

 

References
1. Mydlarz, W.K., Eisele, D.W. (2020). Complications of Neck Surgery. In Flint, P.W., et al. (Eds.), Cummings Otolaryngology: Head and Neck Surgery 7e. (pp. 1831-1839). Philadelphia, PA: Elsevier.
2. Zhang, I., DeMauro-Jablonski, S., Ferris, R.L. (2013). Treatment of Thyroid Neoplasms. In Johnson, J.J., Rosen, C.A. (Eds.), Bailey’s Head and Neck Surgery-Otolaryngology 5e (pp. 2115-2130). Baltimore, MD: Lippincott Williams & Wilkins.

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POSTOPERATIVE HYPOCALCEMIA

Overview
Transient postoperative hypocalcemia following total thyroidectomy, completion thyroidectomy, total laryngectomy, or level VI neck dissection is relatively common, occurring in up to 50% of patients depending on the procedure. The cause of this complication is related to compromised parathyroid gland function from direct parathyroid injury, ischemia, or unintentional removal; the latter resulting in permanent hypoparathyroidism. Importantly, hypoparathyroidism typically requires injury to more than three glands as one undisturbed gland is adequate to maintain calcium levels. Taken a step further, unilateral neck surgery such as thyroid lobectomy, which does not disturb parathyroid glands on the contralateral side, rarely causes hypoparathyroidism and hypocalcemia. However, hungry bone syndrome, a rare occurrence following surgery for severe primary hyperparathyroidism, may result in prolonged hypocalcemia and hypophosphatemia (differentiating it from postoperative hypoparathyroidism) secondary to the absorption of calcium by calcium-deprived bones and may occur even when leaving one or more functioning parathyroid glands undisturbed. Signs and symptoms associated with acute hypocalcemia range from asymptomatic to cramps, seizures, tetany, bronchospasm, laryngospasm, or cardiac arrythmia. Thus, at a minimum, serial postoperative calcium levels should be monitored closely in at-risk patients so early treatment can be initiated. Practice patterns vary by institution and among surgeons, although some advocate giving prophylactic calcium and vitamin D supplementation in the early postoperative period. At many institutions, postoperative parathyroid hormone (PTH) levels are frequently obtained following surgery to help predict the development of postoperative hypocalcemia.

Calcium in serum is bound to albumin; thus, serum calcium concentrations in patients with low or high serum albumin levels (normal range 3.5-5.4 g/dL) may not reflect ionized calcium concentrations – the physiologically active form. While ionized calcium (independent of albumin levels) remains the gold standard for evaluating calcium status, ionized calcium is not routinely performed because of higher cost and challenging sample handling requirements. For total serum calcium levels, consider using a calcium correction formula if albumin levels are abnormal. One commonly used formula for corrected total serum calcium (mg/dL) is serum calcium (mg/dL) + 0.8 x (4.0 − serum albumin [g/dL]).

HYPOCALCEMIA.png

Signs and Symptoms

  • Chvostek sign: Contraction of ipsilateral facial muscles subsequent to percussion over the facial nerve, usually approximately 2 cm anterior to the tragus and 1 cm inferior to the zygoma. Not reliable as up to 30% of adults without hypocalcemia exhibit a positive Chvostek sign and 30% of adults with hypocalcemia do not exhibit this response.

  • Electrocardiogram: QT prolongation or prolongation of the QTc (corrected QT interval) secondary to a prolonged ST segment. If critically low hypocalcemia is not appropriately treated, this may lead to arrhythmias such as torsades de pointes, ventricular tachycardia, or complete heart block.

  • Paresthesias: Tingling or prickling sensation, often in the lips, tongue, fingers, and feet.

  • Tetany: Development of spontaneous muscle cramping and pain (e.g., carpopedal spasm).

  • Trousseau sign: Spasm of the forearm and hand occurring after placing a blood pressure cuff on the upper arm at a pressure greater than the systolic blood pressure for 3 minutes. May be present in up to 4% of adults without hypocalcemia and carries test sensitivity of 94%.

 

Management

  • Goals of therapy are to relieve symptoms, decrease risk of cardiac arrhythmias, and increase and maintain a serum calcium concentration in the low-normal range (e.g., 8.0-8.5 mg/dL).

  • Proactive monitoring of calcium levels and early treatment are important for at-risk patients. Most recommend obtaining total serum calcium levels (with albumin correction if applicable) every 6 hours after surgery until levels stabilize; more frequent testing should be obtained if calcium levels are trending downward, are concernedly low (e.g., serum calcium <7 mg/dL), or IV calcium is administered. Some centers also obtain early postoperative PTH levels, usually within the first couple of hours, to help predict impending hypocalcemia.

  • Hypocalcemia may not correct until magnesium is corrected. Hypomagnesemia causes hypocalcemia through impairment of PTH secretion and renal resistance to PTH, leading to decreased reabsorption of calcium in the kidney. Phosphate levels are commonly monitored along with calcium levels (hyperphosphatemia may precede hypocalcemia from acute hypoparathyroidism).

  • Promptly evaluate patient if concern for symptomatic hypocalcemia develops or if critically low calcium values are discovered.

  • If administering IV calcium gluconate:

    • Calcium gluconate infusion must be administered slowly to avoid complications including cardiotoxicity (e.g., bradycardia, asystole), hypotension, and peripheral vein sclerosis. Follow institutional protocol for rate of infusion.

    • Ideally given via central line (e.g., peripherally inserted central catheter [PICC]); intramuscular administration should be avoided because of risk of localized soft-tissue and skin necrosis with extravasation.

    • For symptomatic hypocalcemia requiring IV calcium gluconate, it may take time to establish a central line and consideration may be given to initiating IV calcium gluconate therapy via peripheral IV with a slow infusion (over 10-20 minutes) to treat symptoms acutely.

    • Monitor calcium levels closely; consider serial labs every 4 hours as well as ionized calcium levels with a blood gas if severe or requiring IV calcium administration.

    • Replenish potassium and magnesium levels when necessary.

    • If patient is taking medications PO, start oral calcitriol (activated form of vitamin D) and calcium carbonate concomitantly.

    • Exercise caution in patients with renal insufficiency or taking digitalis.

    • Ensure patient is on continuous telemetry and consider obtaining a 12-lead electrocardiogram if severe.

  • Management of acute postoperative hypocalcemia following thyroid surgery or level VI neck dissection varies among centers, and you should understand the preferred management algorithm at your center; promptly notify other senior members of your care team if critically low values develop and maintain a low threshold for consulting Endocrinology based on clinical context.

 

Example Treatment Protocols

  • Example of a traditional protocol:

    • If corrected serum calcium >7.5 mg/dL (or ionized calcium is >3 mg/dL): Start oral calcium and vitamin D supplementation with calcitriol (activated form of vitamin D).

    • If corrected serum calcium <7.5 mg/dL (or ionized calcium is <3 mg/dL): Start IV calcium gluconate supplementation.

    • If carpopedal spasm, tetany, seizures, or prolonged QT with hypocalcemia: Start IV calcium gluconate supplementation and consider continuous infusion.

  • Example of a protocol incorporating postoperative PTH testing:

    • If corrected serum calcium >7.0 mg/dL with detectable PTH: Start oral calcium and vitamin D supplementation.

    • If PTH is undetectable: Start oral calcium and vitamin D supplementation and follow calcium levels.

    • If corrected serum calcium <7.0 mg/dL: Obtain electrocardiogram, place central line, and start IV calcium gluconate supplementation.

 

References
1. Shindo, M.L. (2013). Hyperparathyroidism: Evaluation and Surgery. In Johnson, J.J., Rosen, C.A. (Eds.), Bailey’s Head and Neck Surgery-Otolaryngology 5e (pp. 2131-2146). Baltimore, MD: Lippincott Williams & Wilkins.
2. Kakava, K., Tournis, S., Papadakis, G., et al. (2016). Postsurgical hypoparathyroidism: A systematic review. In Vivo. 30(3):171-179.
3. Khan, M.I., Waguespack, S.G., Hu, M.I. (2011). Medical management of postsurgical hypoparathyroidism [published correction appears in Endocr Pract. 17(6):967. dosage error in article text]. Endocr Pract. 17 Suppl 1:18-25.
4. Witteveen, J.E., van Thiel, S., Romijn, J.A., et al. (2013). Hungry bone syndrome: Still a challenge in the post-operative management of primary hyperparathyroidism: A systematic review of the literature. Eur J Endocrinol. 168(3):R45-R53.

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