Endotracheal Tube Fallout in a Patient with Severe Obesity During Eye Surgery.
A 48-year-old man weighing 178 kg (392 pounds) and 176 cm (69 inches) tall, with a history of obstructive sleep apnea, was scheduled for corneal surgery under general anesthesia. After induction, he was intubated with a size 8 endotracheal tube, which was secured with sticky tape. On completion of the operation, the patient was transferred to a motorized gurney to extubate him in a sitting position because the operating room (OR) table was too narrow. However, while the team was moving him from the OR table to the gurney, a nurse inadvertently pulled on the anesthetic machine hoses. The endotracheal tube became dislodged and the patient could not be ventilated; his hemoglobin saturation decreased to the high 80s for about 30 seconds. He had already been given sugammadex to reverse rocuronium induced-neuromuscular block. After intravenous (IV) suxamethonium 150mg, his trachea was speedily re-intubated and his lungs were ventilated with 100% oxygen, restoring arterial oxygen saturation to normal levels. His neuromuscular transmission was monitored at the adductor pollicis and once fully recovered from neuromuscular blockade, he was awakened and extubated. He suffered no harm from the incident and was discharged after 4 hours of observation.
By Christian Bohringer MBBS
The incidence of obesity is rising in many countries around the world, which has led to an increase in sleep apnea, metabolic syndrome, type 2 diabetes mellitus, non-alcoholic fatty liver disease, cancer and premature death.1-9 Severe or class 3 obesity, with Body Mass Index (BMI) greater than 40 as in this case, may be one of the contributors to the observed decrease in life-expectancy in the United States.10
Obesity presents a challenge for anesthesia care providers. Obese patients have reduced functional residual capacity (FRC) in their lungs when they lie flat because the adipose tissue in their abdomen displaces the diaphragm in a cephalad direction.11 This displacement reduces lung volumes and the amount of oxygen that can be stored in the lungs. Many obese patients cannot sleep lying flat because they become too hypoxemic in this position, especially during periods of hypoventilation. They need to sleep sitting upright in a chair or propped up on pillows so that their lungs can be inflated adequately, and oxygen can be delivered into their arterial blood. When continuous positive airway pressure is prescribed for sleep apnea for these patients, it may not only reduce airway obstruction but also help to maintain alveolar patency and thereby improve oxygenation.12
Obesity-associated obstructive sleep apnea, principally due to increased soft tissue volume in the neck, may cause recurrent nocturnal desaturation leading to secondary polycythemia and pulmonary hypertension.13 The presence of pulmonary hypertension significantly increases the risk of anesthesia.14 Anesthesia care providers are in an ideal position to identify patients with undiagnosed sleep apnea because they essentially perform a drug-induced sleep study when they administer anxiolytic medications before surgery.15 If a patient displays signs of airway obstruction prior to losing consciousness, he or she should be informed of the possibility of sleep apnea and advised to undergo a formal sleep study.
Obese patients are also at increased risk for postoperative airway obstruction.16 Respiratory depressant medications such as opioids should be administered sparingly, and non-opioid analgesic drugs should be used whenever possible.17 Neuromuscular blocking drugs also need to be fully reversed prior to extubation.
Approaches to Improving Patient Safety
Employ regional anesthesia
Corneal surgery is often performed under regional anesthesia, which avoids many of the risks of general anesthesia.18 Regional anesthesia in this case was not an option because of the patient’s extreme obesity. A severely obese patient like this, with a body mass index (BMI) of 57, usually cannot lie flat for the operation while breathing spontaneously, as is required for the ophthalmic surgeon to perform the procedure. A general anesthetic with an endotracheal tube was therefore necessary in this case so that positive end expiratory pressure (PEEP) could be applied from the ventilator to the lung via the endotracheal tube (ETT).
Secure the ETT circumferentially
Whenever possible, the ETT should be secured in place with a mechanism that encircles the head.19,20 When the ETT is fixed securely, inadvertent traction applied to the breathing circuit will pull the breathing circuit apart rather than pull the ETT out of the trachea. A cotton tape or other commercially available device can be used for this purpose.21,22 With proper ETT fixation, OR team members should be able to lift the patient’s head off the pillow by pulling on the endotracheal tube without dislodging the tube.
Circumferential tube fixation should also be used whenever intubated patients are transferred from the OR table to a gurney or when they are moved from the supine to the prone position. ETT dislodgement is a constant risk when transporting intubated patients in prehospital care and within the hospital to the intensive care unit or to the imaging suite. Particular attention must be paid to ETT fixation whenever transporting intubated patients, especially when intubation was difficult and required the use of advanced intubation devices like video-laryngoscopes and flexible intubation scopes. In patients whose airways are difficult to control, reintubation is more likely to fail and an inadvertent extubation may therefore have much more devastating consequences than in this case.23
Disconnect the breathing circuit before transferring an intubated patient
This patient’s ETT was dislodged because the nurse was holding onto the breathing circuit during transfer. If the ETT had been disconnected from the circuit during the transfer, it would not have been pulled out accidentally. Disconnecting the ETT from the circuit leads to a transient loss of PEEP but makes it less likely for the ETT to become dislodged prematurely.
Hyperoxygenate and hypoventilate high-risk intubated patients before transfer
A high-risk patient like this should always be ventilated with a high concentration of oxygen prior to extubation and before transfer to the gurney. If this patient had more oxygen stored in his lungs before the accidental extubation, he may not have suffered hypoxemia so quickly.24 Inserting an airway, applying high flow nasal oxygen or continuous positive airway pressure via face mask, and sitting him upright might have stabilized the situation to the point where re-intubation would not have been necessary. Letting the carbon dioxide level in the blood rise above the apneic threshold at the end of the procedure is very important so that the patient has adequate drive to breathe spontaneously after extubation. Volatile anesthetic agents abolish the hypoxic drive to breathe, so the patient depends on a sufficiently high carbon dioxide level to drive respiration.25
Reverse neuromuscular blocking drugs
Persistent neuromuscular blockade is poorly tolerated by obese patients because of their increased work of breathing. This problem may have contributed to the patient’s inability to maintain adequate oxygenation after the ETT was inadvertently dislodged. Following succinylcholine administration, a nerve stimulator was used to document full recovery of neuromuscular function prior to successful extubation. The American Society of Anesthesiology now recommends the use of quantitative neuromuscular monitoring devices based on the principles of electromyography or acceleromyography applied to the adductor pollicis muscle to confirm full recovery from neuromuscular blocking drugs prior to extubation.26 This quantitative neuromuscular monitoring is now recommended because full neuromuscular recovery cannot be reliably determined by the use of a traditional peripheral nerve stimulator.
Monitor patients vigilantly
This patient was monitored thoroughly with pulse oximetry and the hypoxemia was recognized immediately, which prevented a hypoxic cardiac arrest. Given the severe hypoxemia, a full intubation dose of succinylcholine was given, and the patient was successfully ventilated and re-intubated. Monitoring the patient’s respiration and oxygenation is especially important immediately following extubation because at this time the airway could be obstructed from residual sedation, persistent neuromuscular blockade, or laryngospasm. Vigilant monitoring in this case led to the hypoxemia being treated expeditiously, so the patient did not suffer any harm and could be discharged home 4 hours after the procedure.
Provide high-flow nasal oxygen
High flow nasal oxygen also known as trans-nasal humidified rapid-insufflation ventilatory exchange (THRIVE) is a therapeutic modality that is very helpful in maintaining oxygen saturation following extubation in high risk patients. The oxygen is humidified and high gas flows up to 70 liters/minute are well tolerated by patients. It can reduce the incidence of apnea and desaturation in obese patients and others who are at high-risk for hypoxemia.27
- Consider regional anesthesia for high-risk patients when possible.
- Use a circumferential endotracheal tube fixation technique.
- Disconnect the ETT from the breathing circuit prior to moving the patient.
- Ensure adequate reversal of neuromuscular blocking drugs prior to extubation.
- Fill the lungs with oxygen and let the carbon dioxide level rise before extubation.
- Monitor vigilantly and correct problems rapidly.
- Consider using high flow nasal oxygen following extubation in obese and other high-risk patients.
Christian Bohringer, MBBS
Professor of Clinical Anesthesiology
Department of Anesthesiology and Pain Medicine
UC Davis Health
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