Apneic oxygenation refers to continuous insufflation of oxygen to an apneic patient to maintain adequate arterial oxygen content in the absence of lung movement.1 Recently, transnasal humidified rapid-insufflation ventilatory exchange (THRIVE) has gained popularity in the anesthesia community and has been used to maintain arterial oxygen saturation and increase apnea times after induction of anesthesia.2 Historically, the rate of rise of arterial carbon dioxide (CO2) has been a significant limiting factor for airway surgeries performed under apneic conditions. Prior studies have quantified generally expected rates of CO2 rise that correlate with different apneic scenarios. Specifically, Stock et al3 clamped tracheal tubes in apneic patients and measured an average Paco2 rise of 12.0 mm Hg in the first minute, followed by a rise of 3.4 mm Hg/min thereafter. Eger and Severinghaus4 studied Paco2 rise during low-flow apneic oxygenation, demonstrating an increase of 13.4 mm Hg during the first minute of apnea, followed by a 3.0 mm Hg/min rise thereafter. It has been suggested, however, that THRIVE leads to better CO2 clearance than previous methods through gaseous mixing and dead space flushing.5 Using THRIVE, Patel and Nouraei2 reported an average rate of end-tidal CO2 (ETco2) rise of 1.1 mm Hg/min, and Lyons and Callaghan1 reported a 1.3 mm Hg/min average rate of rise of ETco2.
Laryngeal and tracheal surgeries are often performed with microlaryngeal tubes in place, but portions of the glottis may remain difficult to see. Techniques to provide an unobstructed surgical field include the use of jet ventilation or intermittent apnea with repeated extubation. The risk of barotrauma and the potential for hypoxia or airway injury from these methods should not be overlooked.1
We report a series of 3 patients who underwent laryngeal and tracheal surgeries under apneic conditions using a combination of high-flow nasal oxygen, jet ventilation, and intubation with mechanical ventilation. The Teleflex Comfort Flo (Morrisville, NC) high-flow nasal cannula was utilized as the sole method for oxygenation and ventilation for the first 15 minutes of each case. Transcutaneous carbon dioxide (CO2) levels measured with a SenTec Digital Monitoring System (Fenton, MO) were recorded throughout the apneic period.
All patients were deidentified, and written consent regarding compliance with Health Information Portability and Accountability Act of 1996 and use of medical information was obtained from the patient before the publication of this case report.
A 59-year-old, 82-kg woman with a history of hypertension, mild chronic obstructive pulmonary disease, smoking, and a hoarse voice presented for microsuspension laryngoscopy with microdebridement of bilateral true vocal cord polyps and Reinke’s edema. In the operating room, a transcutaneous CO2 monitor and all standard American Society of Anesthesiologists (ASA) monitors were placed on the patient. While in a 45° head-up position, the high-flow nasal cannula was placed in the patient’s nares 5 minutes before induction and titrated to its maximum settings (60 liters per minute, fraction of inspired oxygen [Fio2] 100%). During this time, the patient was asked to breathe through their nose with their mouth closed.6 The transcutaneous CO2 monitor was allowed to equilibrate, and baseline values were recorded. General anesthesia was induced with fentanyl, propofol, and rocuronium, at which point the apneic period commenced. A jaw thrust was performed until loss of twitches was confirmed by train-of-four stimulation. The patient was placed in suspension using a Teleflex Dedo-Pilling (Morrisville, NC) microlaryngoscope, and anesthesia was maintained with propofol and remifentanil infusions. The transcutaneous CO2 measurements were recorded at 5-minute intervals (Figure). After 15 minutes, transcutaneous CO2 reached 70 mm Hg, and the decision was made by the anesthesia team to transition to jet ventilation for the remainder of the procedure to avoid significant hypercarbia and acidosis. The maximum transcutaneous CO2 during 33 minutes of jet ventilation was 68.4 mm Hg. At the conclusion of the procedure, the surgeons placed a 6.0 mm microlaryngeal tube with an initial ETco2 of 67 mm Hg. Emergence and extubation were uneventful, and the patient was taken to the postanesthesia care unit (PACU).
A 26-year-old, 73-kg man status-post gunshot wound and prolonged tracheal intubation at an outside hospital presented with shortness of breath and was scheduled for microsuspension laryngoscopy and tracheal balloon dilation of subglottic stenosis. In the operating room, a transcutaneous CO2 monitor and all standard ASA monitors were placed on the patient. High-flow nasal cannula (60 LPM, Fio2 100%) was applied for preoxygenation and induction with fentanyl, propofol, and rocuronium ensued. Jaw thrust was performed until the patient was placed in suspension. The transcutaneous CO2 measurements were recorded at baseline and at 5-minute intervals during apnea (Figure). After 15 minutes of apnea and a peak transcutaneous CO2 of 70 mm Hg, the surgeon placed a small diameter laser endotracheal tube, and the Fio2 was decreased to 30% in preparation for laser use. The initial postintubation ETco2 measurement of 67 mm Hg correlated well with the transcutaneous CO2 reading. The laser tube was removed after 3 minutes, and jet ventilation was used to improve the surgeon’s view for the remainder of the laser portion of the procedure. A 6.0 mm microlaryngeal tube was placed at the conclusion of the case. Emergence and extubation were uneventful, and the patient was transferred to the PACU.
A 60-year-old, 72-kg man with history of hypertension, mild chronic obstructive pulmonary disease, and squamous cell carcinoma of the vocal cords presented for microsuspension laryngoscopy and biopsy of a vocal cord lesion suspicious for recurrence. After arrival to the operating room and placement of a transcutaneous CO2 monitor and ASA standard monitors, high-flow nasal cannula (60 LPM, Fio2 100%) was applied for preoxygenation and induction with fentanyl, propofol, and rocuronium ensued. Jaw thrust was performed until the patient was placed in suspension, and transcutaneous CO2 measurements were recorded at baseline and at 5-minute intervals during apnea (Figure). The initial transcutaneous CO2 reading was 32 mm Hg, and after 15 minutes, the transcutaneous CO2 was 56 mm Hg. After 40 minutes of apnea, the transcutaneous CO2 rose to 89.4 mm Hg, and the decision was made to intubate the patient to avoid further hypercarbia. The initial postintubation ETco2 reading was 70 mm Hg. For the remaining 22 minutes of the procedure, mechanical ventilation was maintained and the transcutaneous CO2 and ETco2 values decreased appropriately to 50 and 46 mm Hg, respectively. Emergence and extubation were uneventful, and the patient was transferred to the PACU.
We have demonstrated that THRIVE can be used in apneic patients during laryngeal and tracheal surgeries for at least 15 minutes. Average apnea time for the 3 patients was 23.3 minutes with a range of 15–40 minutes. Apnea duration was determined partially by our comfort level with hypercarbia and the reliability of the transcutaneous CO2 monitor to accurately reflect rising arterial CO2 levels and partially by requests from the surgical team for laser use.
In 2 of the 3 cases, we found that transcutaneous CO2 measurements correlated well with ETco2 readings after intubation. In an earlier study using transcutaneous CO2 monitoring, Bolliger et al7 demonstrated unreliability of transcutaneous monitoring and suggested that these noninvasive systems cannot replace conventional blood gas analysis, but the accuracy and correlation of ETco2 monitoring with transcutaneous or arterial CO2 monitoring was not evaluated. Vivien et al8 found that transcutaneous CO2 monitoring during apnea testing in brain-dead patients could accurately predict when Paco2 reached 60 mm Hg. Of note, the largest postintubation discrepancy between ETco2 and transcutaneous CO2 occurred during case 3 at transcutaneous CO2 levels >60 mm Hg. Therefore, for short surgical procedures requiring apnea, use of high-flow nasal cannula may be feasible if assessment of hypercarbia and acidosis can be made with intermittent blood gas analysis in addition to continuous monitoring of transcutaneous CO2.
The rates of rise of transcutaneous CO2 in the 3 cases were 1.81, 2.85, and 1.50 mm Hg/min, respectively. Using a linear regression, we determined an average rate of rise of 1.68 mm Hg/min (0.23 kPa/min), which is higher than previously reported. Factors contributing to this variation are many and include a small sample size, different monitoring techniques, and patient factors. The average rate of rise of CO2 is an observational point of interest only, because the comparison to previously reported rates is limited due to our small sample size. During apneic oxygenation, gas transfer in the alveoli is driven by oxygen consumption and CO2 production in the tissues. All patients were oxygenated adequately, and the lowest arterial saturation recorded was 97%. We administered an Fio2 of 100% to provide the greatest possible oxygen reserve. Jet ventilation was utilized during the laser portions to decrease the risk of airway fire because the potential for the tissues to ignite during high-flow oxygen insufflation remains unknown.
These results demonstrate that use of THRIVE during airway surgery is possible for short durations to provide unobstructed views of the surgical field. The observed rates of rise of transcutaneous CO2 among our patients suggest that continuous and reliable transcutaneous CO2 monitoring or intermittent blood gas sampling may be necessary when using THRIVE. Much remains to be studied regarding appropriate use of THRIVE in the field of anesthesiology.
Name: Callie Gittemeier Ebeling, MD.
Contribution: This author helped write and edit the manuscript.
Conflicts of Interest: None.
Name: Christina Anne Riccio, MD
Contribution: This author helped perform anesthesia for the cases and edit and review the manuscript.
Conflicts of Interest: Dr Riccio received speaker honoraria and travel expense reimbursement from Teleflex Incorporated to speak at 2 sales meetings.
This manuscript was handled by: BobbieJean Sweitzer, MD, FACP.
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