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Capnography-Guided Nasotracheal Intubation of a Patient with a Difficult Airway and Unwanted Respiratory Depression

Mentzelopoulos, Spyros D. MD, DEAA(P1); Augustatou, Callirroi G. MD; Papageorgiou, Evangelos P. MD, PhD

doi: 10.1213/00000539-199809000-00049
Case Reports

Department of Anesthesia, Egion General Hospital, Egion, Greece.

Accepted for publication June 9, 1998.

Address correspondence and reprint requests to Spyros D. Mentzelopoulos, 2A Kypseli St., GR-113 62 Athens, Greece.

We report the combined use of PETCO2 monitoring, low positive pressure ventilation, and endotracheal tube (ETT) cuff inflation to achieve blind nasotracheal intubation of a patient with a difficult airway and midazolam-induced respiratory depression. Nasal mucosa trauma was prevented by inserting a Foley catheter into the ETT with the cuff inflated to provide a smooth tapered end. The ETT tip's passage from the rhinopharynx to the trachea was facilitated by two consecutive ETT rotations at appropriate insertion lengths. Correct ETT placement was confirmed by both fiberoptic bronchoscopy and a chest roentgenogram.

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Case Report

A 48-yr-old woman presented with a subcapital right femoral head fracture. She had a history of Klippel-Feil syndrome and of healed, secondary pulmonary tuberculosis.

Physical examination revealed a 168-cm, 70-kg woman with signs of mild cardiovascular shock (heart rate 125 bpm; arterial blood pressure 90/50 mm Hg; cool, pale, moist skin; and collapsed neck veins). Her respiratory rate was 40 breaths/min, and auscultation of the chest revealed diminished breath sounds over the left hemithorax. A large ecchymosis covered the lateral aspects of her right thigh, hip, and femur. The electrocardiogram displayed sinus tachycardia, and the chest roentgenogram revealed left lower lobe atelectasis with left tracheal displacement and overinflation of the right lung.

Initial laboratory results showed a hemoglobin level of 10 g/dL. Serum urea, electrolytes, platelet count, and liver function tests were within normal limits. Activated partial thromboplastin time was 35 s, international normalized ratio was 1.10, PaO2 was 125 mm Hg, fraction of inspired oxygen was 0.35, PaCO2 was 33 mm Hg, and pHa was 7.38.

Initial treatment included oxygen administration and fluid resuscitation with lactated Ringer's solution, red cell concentrates, and fresh-frozen plasma. The patient was stabilized (heart rate 80-100 bpm, mean arterial pressure 85-95 mm Hg, respiratory rate 20-25 breaths/min, urine output >1 mL [center dot] kg-1 [center dot] h-1), fasted for 8 h, and moved to the operating room for total hip arthroplasty. Her airway was evaluated as Mallampati class IV with inadequate mouth opening (<3 cm), limited neck extension (<35[degree sign]), and a short tip of mandible-hyoid bone distance (approximately 4 cm) (Figure 1).

Figure 1

Figure 1

Regional anesthesia was ruled out because of lack of consent; based on specific experience, we selected the awake blind nasotracheal technique for intubation. Airway preparation included instillation of phenylephrine drops into both nostrils, spraying the oropharynx with 2% lidocaine, and performing both superior laryngeal and transtracheal nerve blocks with 2% and 4% lidocaine, respectively (total lidocaine dose <300 mg).

The patient was quite anxious, and small IV increments of midazolam were administered for light sedation. After a total dose of 3 mg, her speech became slurred, and her respiratory rate decreased to 10 breaths/min.

Without further delay, and with the head in neutral position, a 7.5 Portex-blue line ETT was passed through the seemingly wider left nostril after the application of 2% lidocaine gel. A 12 Foley catheter already inserted to the ETT's end was inflated with 3 mL of saline, resulting in a smooth tapered end. The ETT was introduced into the nostril 5 cm and then rotated 90[degree sign] counterclockwise for easier passage to the oropharynx. At approximately 8 cm, we removed the Foley catheter and rotated the ETT 180[degree sign] clockwise to rest its bevel slide smoothly and atraumatically on the anterior laryngeal wall.

After inflating the cuff with 20 mL of air, the intubationist listened for breath sounds through the ETT's connector; a few seconds later, he realized that the patient's respiration was severely depressed. An alternative approach was immediately followed: the circuit adapter of a side stream capnograph was distally connected to the ETT's connector and proximally connected to the Y-piece of the anesthesia breathing circuit; fresh gas flow was set to 7 L of O2/min, and low positive pressure (<10 cm H2 O) breaths were administered to the patient at a rate of 25-30/min by gently squeezing the reservoir bag.

Our capnograph monitor showed an PETCO2 of 28 mm Hg, which reached 36 mm Hg after the slow ETT advance for another 5 cm (total 13 cm). At this point, resistance to further insertion indicated the impact of the distal surface of the cuff on the vocal cords. The cuff was immediately deflated, the ETT was advanced another 6 cm, and the cuff was reinflated. Tracheal intubation had already been confirmed by capnography, and correct tube placement was confirmed by both fiberoptic bronchoscopy and a chest roentgenogram (Figure 2).

Figure 2

Figure 2

Anesthesia was induced with etomidate and fentanyl and maintained with sevoflurane and nitrous oxide in oxygen and small supplemental fentanyl boluses. Tracheal extubation was performed with the patient awake. Her recovery was smooth and uneventful.

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In any case of difficult airway, the American Society of Anesthesiologists recommends priority to the least invasive techniques of airway control and preservation of patients' spontaneous respiration and consciousness [1]. In this case, our first choice was the standard technique of blind nasotracheal intubation, which is simple, safe, noninvasive, and includes preservation of spontaneous respiration to guide the ETT toward and through the vocal cords [2]. ETT cuff inflation in the oropharynx nearly doubles the success rate of the first blind nasotracheal attempt (75% vs 40%) [3]. The use of a Foley catheter is suggested to prevent upper airway trauma during nasal insertion [4]. A 90[degree sign] counterclockwise ETT rotation facilitates its passage to the oropharynx, and a subsequent 180[degree sign] clockwise ETT rotation should provide easier passage of its tip through an anteriorly located larynx (Figure 1).

The combination of local anesthesia with superior laryngeal and transtracheal nerve blocks was used to ameliorate the physiologic responses to airway manipulations. The risk of lidocaine toxicity was low because total dose did not exceed 300 mg [5]. Light sedation with midazolam was necessary because the patient became quite anxious after entering the operating room.

After the unwanted respiratory depression, we had the following alternatives at our disposal: (a) intubation attempt with conventional direct laryngoscopy [1,6], which was technically difficult because of the patient's small mouth opening; (b) continuation of the initial attempt with the use of a fiberoptic bronchoscope [6], which was time-consuming; (c) insertion of a laryngeal mask airway [1,6]; (d) emergency surgical pathway [1,6]; (e) ETT withdrawal, reversal of respiratory depression with flumazenil, and consideration of feasibility of other options [1,6] (mask ventilation could be necessary until restoration of spontaneous respiration, and adequate mask fit was difficult because of the patient's facial features) (Figure 1); and (f) continuation of the initial intubation attempt, as described in our case report.

The last option seemed preferable because PETCO2 monitoring with a side stream capnograph capable of responding in <2 s [7] provided a reliable way to advance the ETT toward the glottis and confirm tracheal intubation. Low positive pressure (<10 cm H2 O) ventilation was possible before securing the airway. In the case of failed intubation, ventilation of the patient would still be possible by partially withdrawing the ETT according to the data display of our PETCO2 monitor. In such a case, restoration of spontaneous respiration with flumazenil would be a useful alternative.

We conclude that the combination of Foley catheter insertion into the ETT with the cuff inflated, 90[degree sign] counterclockwise and a subsequent 180[degree sign] clockwise ETT rotation, ETT cuff inflation, PetCO2 monitoring, and low positive pressure ventilation can be used as an alternative technique of atraumatic blind nasotracheal intubation in patients with difficult airway and depressed respiration.

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