Postoperative Continuous Pressure Monitoring in Thyroid Surgery: Pathophysiology of Post-Thyroidectomy Hemorrhage

Introduction:

Post-thyroidectomy hemorrhage is a rare, but life-threatening complication^1–3 with an incidence of about 1.8%.^2,3 It can cause severe morbidity and can possibly be fatal.^2–4 There are some known risk factors described in the literature.^5,6 Only little is known about the pathophysiologic background of apnea caused by post-thyroidectomy hemorrhage, but all available knowledge is based on case reports and clinical observation. In a previous series of experiments, we simulated post-thyroidectomy hemorrhage in an animal model and found the cervical compartment pressure to play a central role in the pathophysiology. With an increase of the cervical compartment pressure, respiration stopped and apnea occurred, when reaching a threshold pressure. With a pressure relief to normal, respiration started again. We could repeat this mechanism up to six times in one animal. Altogether, there seems to be a reversible, cervical compartment pressure-dependent apnea. But up to now, nothing is known about postoperative normal pressure levels in the cervical compartment. The aim of this study was to define physiologic and pathologic pressure levels in the cervical compartment and to evaluate whether the cervical compartment pressure could be used as detector for post-thyroidectomy hemorrhage.

Materials and Methods:

We performed a prospective clinical trial on 32 patients undergoing unilateral and bilateral thyroid resections. ⁷ At the end of surgery, a pressure microsensor (3PN Probe Spiegelberg, Hamburg, Germany) was placed into the cervical compartment in the former thyroid space. Postoperative continuous pressure measurement was carried out for 48 hours postoperatively during rest and during special activities and physical stress situations. Patients were randomized to groups with and without suction drains.

Results:

The overall mean pressure level at rest on both postoperative days with and without drains was 0.36 ± 2.84 torr. The mean pressure levels during all situations on the first/second postoperative days were 0.23 ± 3.71/1.33 ± 4.50 torr. During defined activities such as coughing, standing and coughing, and climbing or descending stairs, the pressure levels varied, but stayed close to 0 torr with short reversible stress-related peaks. Comparing all cases with and without drains, the pressure levels were close to 0 torr with a wider range of values in patients with suction drains than in patients without. One patient in this clinical trial developed a post-thyroidectomy hemorrhage and the pressure increased continuously up to 35 torr, before the wound was reopened and the patient was transferred to the operation theater.

Conclusion:

Respiratory drive can be suppressed by increased pressure levels in the cervical compartment. After thyroid resections, physiologic pressure levels were around 0 torr in the cervical compartment. In the case of post-thyroidectomy hemorrhage, pressure levels in symptomatic patients exceed 10 and even 20 torr. A postoperative cervical compartment pressure monitoring can detect a continuous increase of the cervical compartment pressure >10 torr and, therefore, might be ideal for an early detection of bleeding complications in thyroid surgery, thereby improving patient's safety.

This work was carried out at the Department of General and Vascular Surgery, Agatharied Hospital.

This clinical trial was supported by ISAR M GmbH, Holzkirchen, Germany. The presented data from animal experiments were generated with support of the German Federal Ministry for Economic Affairs and Energy.

No competing financial interests exist.

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