EDITOR:
Primary hyperparathyroidism (pHPT) is the most common cause of hypercalcaemia, accounting for more than 50% of cases [Reference Aguilera and Vaughan1]. Symptoms associated with hypercalcaemia generally correlate with both the magnitude and the rapidity of the increase in serum calcium. However, patients vary in their sensitivity to serum calcium elevations.
Hypercalcaemia increases the risk of anaesthesia because of potentially dangerous disturbances in cardiac rhythm. Moreover, HPT has been reported to coexist in 20–60% of the cases with nodular thyroid disease. Perioperative management of these patients should, therefore, include careful evaluation of the airway as the extent of compression and deviation caused by the mass can lead to a difficult intubation [Reference Voyagis and Kyriakos2]. Furthermore, meticulous monitoring of neuromuscular blockade should be performed since it has been suggested that hypercalcaemia associated with primary HPT may antagonize the effects of non-depolarizing muscle relaxants [Reference Al-Mohaya, Naguib, Abdelatif and Farag3]. We report here on the anaesthetic management of a patient who presented with parathyrotoxic crisis.
Case report
A 30-yr-old male presented to the emergency department with progressive dyspnoea and subsequent nausea and vomiting of 2 days duration. Physical examination revealed a mass on the left side of the neck that moved with swallowing and a fine stridor was clearly audible during inspiration.
Laboratory tests revealed the following: white cell count 11 950 μL−1; haematocrit 43.7%; platelet count 278 × 103 μL−1; glucose 119 mg dL−1; urea 57 mg dL−1, creatinine 1.5 mg dL−1, serum calcium 16.1 mg dL−1, uric acid 16.1 mg dL−1, sodium 148 mmol L−1 and potassium 4.9 mmol L−1, hormonal control and immunohistochemical staining demonstrated parathyroid hormone (PTH) level of 630 ng L−1.
Ultrasound demonstrated a parathyroid adenoma in the lower left pole of a goitrous thyroid gland. Chest X-ray showed compression and deviation of the trachea caused by a goitre that extended into the mediastinum. Electrocardiography showed shortening of the QT segment. The diagnosis of parathyrotoxic crisis was made and the patient was scheduled for emergency parathyroidectomy.
Routine preoperative assessment of the patient’s airway showed mouth opening of 30°, Mallampati score III, satisfactory neck mobility and thyromental distance 5.6 cm.
The patient received 6 L of normal saline during the first 24 h. Subsequently loop diuretics (furosemide 20 mg 4 h−1) were administered to produce a diuresis of 200 mL h−1. Corticosteroids (prednisolone 100 mg day−1) and biphosphonates (pamidronate 90 mg) were also prescribed.
Serum calcium was reduced to 11.8 mg dL−1 at 48 h. Fibreoptic awake endotracheal intubation was successful without bleeding or other complications, with a time of intubation of 4.6 min.
A bolus dose (2.0 mg kg−1) of propofol was given followed by remifentanil (1 μg kg−1) and parecoxib 40 mg. After loss of the eyelash reflex, cis-atracurium 0.2 mg kg−1 was administered. Lung ventilation was titrated to achieve an end-tidal carbon dioxide (etCO2) of 32–36 mmHg. Anaesthesia was maintained with sevoflurane (end-tidal 1.3%) with a mixture of 35% oxygen in air at a fresh gas flow of 8 L min−1 and remifentanil 0.1–0.2 μg kg−1 min−1. The infusion of remifentanil was adjusted in order to maintain mean arterial pressure (MAP) and heart rate (HR) within a 20% range of the preoperative values, and the value of bispectral index between 40 and 60. Neuromuscular blockade was monitored by measuring the contraction of the abductor pollicis using peripheral nerve stimulator after supramaximal stimulation of the ulnar nerve at the elbow in a train-of-four (TOF) pattern. Neuromuscular blockade was subsequently maintained with repeated doses of 0.03 mg kg−1cis-atracurium, whenever the first twitch (T1) recovered to 25% of control and this took 26.9 min. Systolic, diastolic and MAP, HR and body temperature were stable throughout the whole procedure (85 ± 5 mmHg, 47 ± 3 mmHg, 56 ± 4 mmHg, 75 ± 9 min−1 and 36.1 ± 0.2°C, respectively).
After completion of surgery, which lasted for 115 min, residual neuromuscular block was reversed with 2.5 mg neostigmine and 1 mg atropine. The response to neostigmine was rapid and the TOF ratio had recovered to 0.75 in 4.9 min. The ionized calcium concentration showed a significant decrease to 4.2 mg dL−1 after removal of the adenoma. Calcium was subsequently administered at a rate of 0.5 mg kg−1 h−1.
Upon return of spontaneous respiration, the trachea was extubated and the patient sent to the recovery room. He was discharged the 10th postoperative day.
Discussion
pHPT is the commonest cause of hypercalcaemia. Often the patients are elderly females who are found to have a benign adenoma of a single parathyroid [Reference Aguilera and Vaughan1]. Symptoms associated with hypercalcaemia include muscle cramps, laryngeal spasm, bronchospasm, bradycardia, arrhythmias, anxiety, constipation, anorexia, nausea and vomiting. Poor fluid intake and fluid loss due to emesis are responsible for dehydration and may contribute to an acute hypercalcaemic crisis. Therefore normal intravascular volume and electrolyte status must be restored before anaesthesia and surgery. Therapeutic strategy includes increasing urinary calcium excretion by means of hydration and diuresis.
Our patient presented with dyspnoea due to an enlarged thyroid that compressed and displaced the trachea. Bentrem and colleagues showed that 18% of patients with HPT had concomitant thyroid disease [Reference Bentrem, Angelos, Talamonti and Nayar4]. Goitre, when accompanied by tracheal compression, constitutes an aggravating factor for difficult airway, but no resistance has been encountered in passage of the endotracheal tube through the compressed or narrowed portion of the trachea [Reference Voyagis and Kyriakos2]. For this reason, fibreoptic endotracheal intubation is advisable.
Ljunghall and colleagues showed that patients with HPT who were apparently asymptomatic preoperatively did not have defects of their neuromuscular transmission that were of clinical significance [Reference Ljunghall, Akerstrom, Johansson, Olsson and Stalberg5]. In asymptomatic pHPT neither consistent abnormality of neuromuscular transmission nor abnormal muscle structure was found [Reference Jansson, Grimby, Hagne, Hedman and Tisell6]. On the contrary, Al Mohaya and colleagues reported a decreased response to both succinylcholine and atracurium in a patient with parathyroid adenoma [Reference Al-Mohaya, Naguib, Abdelatif and Farag3].
In patients there was a decreased duration of action of cis-atracurium. There was recovery of T1 to 25% of control at 26.9 min and repeated doses of cis-atracurium (0.03 mg kg−1) administered to maintain relaxation during surgery provided a clinical duration 10.2 ± 0.8 min. Wuffel and colleagues reported that recovery index 25–75% and time to a TOF ratio of 0.70 of cis-atracutium were prolonged significantly by sevoflurane compared with total intravenous anaesthesia [Reference Wuffel, Kahl and Ledowski7]. However, in our patient, increased minimum alveolar concentration (MAC) of sevoflurane did not result in significant effects on duration of or recovery from the block. On the contrary, recovery was considerably shorter in our patient. Intraoperative electrolytes and acid–base balance status were normal and normothermia was maintained.
In conclusion, special attention should be paid to neuromuscular function monitoring in patients with pHPT.
