Compartment Pressure Monitoring After Thyroid Surgery: A Possible Method to Detect a Rebleeding

A diagnostic phase III/IV seamless design to investigate the diagnostic accuracy and clinical effectiveness using the example of HEDOS and HEDOS II

The development process of medical devices can be streamlined by combining different study phases. Here, for a diagnostic medical device, we present the combination of confirmation of diagnostic accuracy (phase III) and evaluation of clinical effectiveness regarding patient-relevant endpoints (phase IV) using a seamless design. This approach is used in the Thyroid HEmorrhage DetectOr Study (HEDOS & HEDOS II) investigating a post-operative hemorrhage detector named ISAR-M THYRO® in patients after thyroid surgery. Data from the phase III trial are reused as external controls in the control group of the phase IV trial. An unblinded interim analysis is planned between the two study stages which includes a recalculation of the sample size for the phase IV part after completion of the first stage of the seamless design. The study concept presented here is the first seamless design proposed in the field of diagnostic studies. Hence, the aim of this work is to emphasize the statistical methodology as well as feasibility of the proposed design in relation to the planning and implementation of the seamless design. Seamless designs can accelerate the overall trial duration and increase its efficiency in terms of sample size and recruitment. However, careful planning addressing numerous methodological and procedural challenges is necessary for successful implementation as well as agreement with regulatory bodies.

Predictors and Preventive Strategies of Bleeding After Thyroid Surgery

Postoperative compressive neck hematoma occurs in approximately 0.1% to 1.7% of cases, most occurring within the first six hours after surgery. Thyroid pathology, patient predisposition, and surgical technique are major risk factors for postoperative hematoma. This narrative review describes current perspectives on predicting and preventing bleeding following thyroid surgery. Predictors of bleeding after thyroid surgery include patient-related factors such as male sex and age, surgery-related factors like total thyroidectomy and operations for thyroid malignancy, and surgeon-related factors. Hemostasis is the primary focus after preserving critical structures in thyroid surgery. The clamp-and-tie technique has been the standard method for dividing the thyroid gland's main vascular pedicles for many years. Bipolar electrocautery has been used for vessels of small size. However, advanced bipolar and ultrasound energy and hybrid devices are now available options that may reduce operative time without increasing costs or complications. In cases where small bleeders close to critical structures are present and the clamp-and-tie technique is not feasible, hemostatic agents are commonly used. Drains do not appear to provide any significant benefits in preventing the sequelae of bleeding after thyroid surgery.

Neck Circumference Measurement for Surveillance and Early Detection of Hemorrhage After Thyroidectomy: A Diagnostic Accuracy Study

Importance

Postthyroidectomy hemorrhage is a potentially life-threatening complication with no reliable noninvasive method of early detection.

Objective

To evaluate the diagnostic accuracy of neck circumference measurement for early detection of postoperative hemorrhage after thyroidectomy.

Design, Setting, and Participants

This diagnostic accuracy study at an academic teaching hospital used a prospective cohort of patients undergoing thyroid surgery from November 1, 2015, to January 31, 2018 (group 1), and a retrospective cohort of patients undergoing the same surgery from January 1, 2020, to September 30, 2021 (group 2). We performed repeated perioperative neck circumference measurements to evaluate the association of increased neck circumference with postthyroidectomy hemorrhage among patients at risk for hemorrhage.

Main Outcomes and Measures

The primary end point was the diagnostic value of neck circumference measurement for detection of postthyroidectomy hemorrhage. Additionally, data on demographic information and risk factors for postthyroidectomy hemorrhage were examined. Data analyses were performed from November 1, 2021, to January 5, 2022.

Results

The prospective cohort (group 1) comprised 60 patients (45 [75%] women) with a mean (SD) age of 52.2 (13.5) years; those who experienced a postthyroidectomy hemorrhage had a mean (SD) age of 57.4 (9.0) years. The retrospective cohort (group 2) comprised 353 patients (258 [73%] women) with a mean (SD) age of 55.3 (14.1) years; patients who experienced a postthyroidectomy hemorrhage had a mean (SD) age of 62.2 (10.0) years. In group 1, postoperative neck circumference increased by a median (range) of 5.0 (4.0 to 7.0) cm in patients with hemorrhage, and only 1.0 (-2.5 to 4.0) cm in patients with no postoperative bleeding (difference in the medians, 4.0 cm [95% CI, 3.0 to 5.5 cm]; effect size, 3.74 [95% CI, 2.6 to 4.9]). Defining a 7% or greater increase in neck circumference as the cutoff value for detecting postthyroidectomy hemorrhage showed a diagnostic sensitivity and specificity of 1.0 (95% CI, 0.48 to 1.0) and 0.86 (95% CI, 0.71 to 0.92), respectively. The retrospective validation also showed a difference in median (range) increase of postoperative neck circumference between patients with hemorrhage and those without-3.0 (0 to 6.0) cm vs 0.0 (-6.0 to 5.0) cm (difference in medians, 3.8 cm [95% CI, 3.0 to 4.9]; effect size, 1.63 [95% CI, 0.96 to 2.3]). Considering 12 false-positive and 332 correct-negative results, the diagnostic tool showed a sensitivity of 0.89 (95% CI, 0.51 to 0.99) and a specificity of 0.97 (95% CI, 0.94 to 0.98).

Conclusions and Relevance

The findings of this diagnostic accuracy study suggest that neck circumference measurement is a feasible and easy-to-use diagnostic tool for routine clinical care to detect postthyroidectomy hemorrhage. A 7% or greater increase over the postoperative baseline neck circumference seems to be a reliable threshold for detecting postthyroidectomy hemorrhage. Neck circumference measurement should be used in combination with surveillance of clinical signs and symptoms.

A cervical compartment syndrome impairs cerebral circulation in post-thyroidectomy hemorrhage: data from an animal model

BACKGROUND

Post thyroidectomy hemorrhage is a potentially life-threatening complication. As the mechanism leading to hypoxemic brain damage and death is still unknown, our aim was to examine the underlaying pathophysiology in an animal model.

METHODS

A series of experiments was performed in our established model for post thyroidectomy hemorrhage in 6 pigs. First, post thyroidectomy hemorrhage was simulated with an artificial increase of cervical compartment pressure. Second, spontaneous bleeding into the cervical compartment was initiated. Primary outcome measure is the correlation between cerebral oxygenation and cervical compartment pressure.

RESULTS

With an increase in cervical compartment pressure apnea could be detected in all experiments. A significant 24.2% (9.5-34.4%) decrease of cerebral oxygenation at time of apnea (47.0%; 38.0-65.0%) compared to baseline values (63.5%; 56.0-74.0%; P=0.043) occurred due increase of cervical compartment pressure concurrent with an impaired cerebral perfusion. Apnea occurred about 200 sec after a 10% decrease of cerebral oxygenation, but 35 sec before a 10% decrease of peripheral oxygenation. Spontaneous bleeding into the cervical compartment causes an increase of cervical compartment pressure reaching levels of the mean arterial blood pressure 56.0 (35.0-72.0) mmHg.

CONCLUSIONS

Peripheral hypoxemia occurs with relevant delay in time after decrease of cerebral perfusion and cerebral hypoxemia, therefore cerebral hypoxemia seems to be causal for a central apnea. With this evidence of impaired cerebral perfusion and cerebral hypoxemia due to an increased cervical compartment pressure we can disprove the historic theory of tracheal collapse due to a compressive hematoma in post thyroidectomy hemorrhage. A cervical compartment syndrome seems to be causal, not only for brain hypoxemia but also an additional laryngo-pharyngeal mucosal edema.

Measuring neck circumference to predict and detect haemorrhage following thyroid surgery. A case series and literature review

Post-thyroidectomy bleeding is a fortunately rare but potentially life-threatening complication that may increase postoperative morbidity and hospital stay. In this case series, we demonstrate the relation between the measurement of neck circumference and haemorrhage following thyroid surgery and the value of this measurement in predicting post-thyroidectomy haemorrhage.

Currently, there is no simple and reliable method available for the early detection of post-thyroidectomy bleeding. Continuous pressure measurement could be a potential tool for the early detection of haemorrhage but is invasive, and more data are required to recommend threshold values for revision surgery. Early recognition and prompt surgical intervention are key to the management of cervical haematoma. Measurement of the neck circumference is a valuable adjunct tool in the early recognition of post-thyroidectomy bleeding. In this case series, we concluded that a 4-cm increase in neck circumference may trigger the clinical decision for cervical exploration.

Evaluation of an Electro-Pneumatic Device for Artificial Capillary Pulse Generation used in a Prospective Study in Animals for Surgical Neck Wound Healing

The paper examines the development and testing of an electro-pneumatic device for wound healing therapy after surgery in the neck area. The device generates air pressure values in a miniaturized cuff using electronic circuitry to drive an electro-valve and air compressor. The device works in two distinct modes: continuous pressure mode and pulsating pressure mode. The pressure value setting can vary from 3 to 11 mmHg, and the pulsating pressure mode’s operating frequency range is approximately 0.1 to 0.3 Hz. Laboratory measurements were conducted to evaluate the device’s correct functioning in both continuous and pulsating pressure modes. A four-day prospective study with animals (n = 10) was also conducted to evaluate neck wound healing therapy using the electro-pneumatic device. Out of the twelve histological parameters analysed to reveal the differences between the experimental and control wounds, only one demonstrated a significant difference. Out of the ten animals treated with the device, three showed a significant difference in terms of benefit after therapy. We can therefore conclude that the device potentially improves the wound healing process in the neck area if the pre-set air pressure value does not exceed 8 mmHg.

New insights into the pathophysiology of postoperative hemorrhage in thyroid surgery: An experimental study in a porcine model

BACKGROUND

Postoperative cervical hemorrhage is a rare but life-threatening complication that can cause severe morbidity. Different mechanisms leading to asphyxia have been described based only on clinical observation.

METHODS

We performed a series of in vivo animal studies simulating post-thyroidectomy hemorrhage and its effect on respiratory drive. Three series of tests were carried out in 12 German domestic pigs under general anesthesia. The pigs were breathing spontaneously with secured airways. An additional series using functional magnetic resonance imaging of the pigs' brainstem was also conducted.

RESULTS

The first experimental series carried out on 2 animals revealed an obvious difference between the effects of cervical hemorrhage and external bleeding with development of hemorrhagic shock. An experimental setting for the repeated simulation of cervical hemorrhage was established. A pressure-dependent mechanism was discovered that led to apnea in every animal despite the secured airway. In 8 of 10 animals, relief of cervical pressure led to complete respiratory recovery. The test was repeated up to 6 times per pig. Apnea was induced in 25 of 25 test procedures (100%) and was followed by respiratory recovery in 22 of 25 tests (88%). The threshold pressure at which the respiratory rate started to decrease was 47 ± 14 Torr when blood was used to increase the cervical compartment pressure. When silicone oil was used in a further experimental series, the threshold pressure was similar at 44 ± 21 Torr. The cervical compartment pressure needed to induce apnea was 74 ± 18 Torr using blood and 74 ± 39 Torr using silicone oil, both of which exceeded the mean arterial pressure by 28 Torr during apnea. Functional magnetic resonance imaging revealed a decrease in brainstem activity during phases of increased cervical compartment pressure, which suggests a possible role for cerebral vascular perfusion.

CONCLUSION

Respiratory drive can be suppressed by increased pressure in the cervical compartment, possibly because of a pressure-dependent impairment in cerebral perfusion through a form of cervical compartment phenomenon or, less likely, a pressure-dependent reflex (nervous) mechanism.