Mediastinal masses are an unusual type of mass, which compresses the surrounding structures. Patients having therapeutic and diagnostic mediastinal procedures performed may receive perioperative care from the anesthesiologist itself. They can be extremely difficult to treat because mediastinal masses, particularly those in the anterior mediastinum, can lead to significant airway obstruction and vascular congestion during surgery, which can worsen under general anesthesia and result in perioperative morbidity and mortality. Many case reports exist of anesthesia-related deadly or almost fatal consequences in individuals with anterior mediastinal masses [1-3]. Our patient also had a huge ventral hernia that needed to be corrected surgically.

Successful management of the mediastinal mass vital structures requires knowledge of its nature and pathophysiology, a thorough preoperative evaluation of the patient, communication with the surgeon, and readiness for the management of cardiorespiratory complications resulting from compression of the trachea and vascular structures [4,5]. Because of the low prevalence and rare presentation, our PubMed search could not find any articles that describe the anesthetic management of such patients. We described such thymoma excision with restricted lung pattern in a patient with dwarfism in this case report. The patient also had a restricted respiratory pattern. We also addressed the assessment for both the surgical procedures and protocols for the postoperative care of these small-stature obese patients.

A general anesthetic procedure was planned for a 39-year-old female patient who had a large ventral hernia and a thymoma. The patient was determined to be moderately obese during the pre-anesthetic evaluation. Her height, at 132 cm (4 feet and 4 inches), was short, and her BMI was 32. Her neck movements were severely restricted by a large thymoma located in the anterior region of the thoracic cavity, and her mandible was receding. She measured about 20 inches around the neck overall. She has Mallampati-grade 4 airways. She had a history of snoring and frequent nighttime sleep-wake cycles. When engaging in mild physical activity, she experiences excessive dyspnoea due to exertion. Furthermore, the patient stated to be sleeping in upright position, which could be a sign of obstructive sleep apnea (OSA). With a FEV1/FVC ratio of 62%, a FEV1 of 63% (1.5 L), and an FVC of 55% (1.7 L), spirometry indicated a moderate restriction in lung function. We started the patient on suitable chest physiotherapy and incentive spirometry to improve lung functioning prior to surgery. The patient was advised about the need for postoperative ventilation in the intensive care unit due to the difficulties involved with weaning.

Since the patient had a history of OSA and was obese, premedication was avoided. On the day of the operation, 10 ml of 4% lignocaine was nebulized to anesthetize the airway for 20 minutes prior to intubation. With difficulty and using a paraspinal technique, an 18G epidural was inserted in the T5 level. The catheter was fixed at 12 markings aiming two levels above the insertion site. Next, the patient was turned into a supine position on the operating table, with two pillows ramping in, and standard ASA monitors were connected. When the patient was positioned comfortably, a flexible bronchoscope with an endotracheal tube was inserted into the patent nostril, as depicted in Figure 1. Above the level of vocal cords were anaesthetized with 2ml of 4% lignocaine spray.

Figure 1: Intubated patient in ramping position and epidural catheter in situ.

An endotracheal tube, nasally cuffed and with a 6.5 mm ID, was inserted and fixed. General anesthesia was administered soon after confirming the endotracheal tube position. To ensure sufficient analgesia during surgery, the epidural was activated and bolus doses were administered intermittently. The rate of fentanyl infusion was kept at 20 mcg/hr for the purpose of enhancing intraoperative analgesia and achieving postoperative endotracheal tube tolerance.

The patient's endotracheal tube was kept in place due to a number of variables, including the patient's difficult airway, history of OSA, surgical resection within the thoracic cavity, massive ventral hernia treated with extensive open dissection in the abdominal region, and other conditions. It was very difficult to manage any possible airway complications during the postoperative period because of these factors. The patient was extubated the following day. The patient remained very drowsy, maintained a 91% saturation, and had difficulty breathing on trial after being extubated. As a result, on the first postoperative day, she was given non-invasive ventilation (NIV).

On the third postoperative day after NIV weaning, the patient maintained an oxygenation PaO2 level below 50%; hence, CPAP was started for an additional three days, and an alternate NRBM approach was applied. The patient was switched to a non-rebreathing mask with a flow rate of 10 liters on the seventh day following the procedure, as depicted in Figure 2. The patient was transferred to the ward and nasal prongs were added the next day. Even while in the ward, the patient had incentive spirometry exercises to improve lung expansion and blood oxygen level monitoring. The patient was discharged from the hospital with pulmonary physical therapy exercises after a 14-day stay.

Figure 2: The patient mobilized after 9 days with 2Litres of oxygen in nasal prongs.

During surgery, providing mechanical ventilation to patients who are extremely obese can present several technically challenging situations, such as keeping the patient's airway open, appropriately oxygenating their lungs, and successfully weaning the patients from the ventilator. This second challenge—appropriately ventilating the obese patient's lungs during surgery—is the main emphasis of our reporting.

In the critical care arrangement, we had a central line for fluid and electrolyte balance and an arterial line monitor for continuous arterial blood gas collection. Although they have been employed, lung function testing and flow volume loops may not be the most effective methods for identifying mediastinal tumours. Thoracic surgery procedures have been found to benefit from flow volume loops. Furthermore, studies have shown that despite their purported capacity to determine the level of impairment and differentiate between intrathoracic and extra-thoracic blockage, they have a weak correlation with airway obstruction severity.

It has been suggested that the risks associated with general anesthesia stem from the relaxation of bronchial smooth muscle and the reduction of lung capacity during the procedure. When diaphragm paralysis is brought on by muscle relaxants, the transpleural pressure gradient is lowered, which opens up the airway [6]. As a result, the airways are of lower quality and extrinsic compression works more effectively. The risk of intraoperative cardiopulmonary collapse during a diagnostic procedure requiring general anesthesia must be carefully weighed against the risk of preoperative treatment leading to an inaccurate diagnosis in patients with large anterior mediastinal masses causing significant cardiopulmonary compromise [7].

Patients who undergo prolonged procedures and have SVC obstruction are additionally at risk for postoperative stridor and glottic oedema [8]. During emergence and recovery, there may be an increased risk of airway problems. Only when the patient is completely aware, compliant, and has fully recovered muscle strength should the airway be extubated. Opioids, muscle relaxants, and short-acting anesthesia medications may be helpful. The patient should be constantly monitored in the post-anesthetic care unit even after a successful extubation, and the anesthesiologist should be prepared to reintubate the patient if necessary because deterioration can happen quickly [9].

Reduced respiratory muscle tone causes a new lung-chest wall equilibrium at a reduced respiratory system volume, which in turn causes a drop in the functional residual capacity of anaesthetized patients [10]. Additionally, under general anesthesia and when supine, there is a cephalad displacement of the diaphragm, which can lead to the development of atelectasis, particularly in obese individuals due to the enormous weight of the displaced stomach contents. In a patient whose end-expiratory pleural pressure is 2 cm H₂O, 5cm H₂O PEEP should be adequate to sustain alveolar patency and a positive end-expiratory pleural pressure.

In contrast, a patient with an end-expiratory trans pulmonary pressure of 15 cm H₂O will require a PEEP of 5 cm H₂O, which is woefully inadequate to prevent alveolar collapse and atelectasis at expiration. The recruiting manoeuvres positive effects, such as decreased atelectasis and increased oxygenation, were only maintained in the group that obtained PEEP following recruitment, according to the authors' findings. After the recruiting manoeuvre, atelectasis resumed within 20 minutes in the group that had returned to zero end-expiratory pressure. Furthermore, atelectasis and oxygenation did not improve in the group that received PEEP alone, which is in contrast to the finding of Futier at al. 35 that PEEP alone can reverse atelectasis [9].

 For an obese patient, VENTI-pressure support ventilation (PSV) may be the most advantageous option because PSV patients must continue to exert some muscle in order to initiate each breath that is provided by the ventilator. Our study focuses on the second challenge which is adequately venting the short, obese patient’s lungs during surgery, as well as the pre-and postoperative use of Non-Invasive Ventilation (NIV) in the obese patient. We observed that NIV was better tolerated [10]. In the days that followed, NIV assistance was progressively reduced and its duration was extended by the clinical symptoms and ABG measurements. It is important to avoid these issues throughout the perioperative period. PEEP must be used during the perioperative phase since most obese individuals cannot be kept in a sitting posture during surgery.

From extubation to NIV, then slow weaning to NRBM with high flow oxygen support and the step down to low flow oxygen with blood gas monitoring must be done in such patients. It is recommended to prepare for facing complications like acute respiratory failure, gas exchange impairment, and further ARDS and need for ECMO.

Patients who are obese and having anesthesia and surgery run the risk of experiencing atelectasis, auto-PEEP, expiratory flow limitation, and reduced oxygenation. This can be avoided only when we wean from higher-pressure devices to lower ones. Additionally thoracic epidural plays a vital role in pain-related complications, especially in pulmonary compromised patients.

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