Abstract
At our hospital, direct and video laryngoscopy are used in airway management for cesarean deliveries performed with general anesthesia. We hypothesized that video laryngoscopy would have a higher success rate of endotracheal intubation on the first attempt compared to direct laryngoscopy. We used our electronic medical record system to search for patients who had cesarean deliveries with general anesthesia with endotracheal intubation performed in the operating room from July 1, 2017, through June 30, 2021. Totals of 186 and 176 patients had direct and video laryngoscopy for the first intubation attempts, respectively; 177 (95%) and 163 (93%) patients, respectively, had a successful intubation on the first attempt with each method. The odds ratio of successful intubation on the first attempt for video laryngoscopy was 0.64 (95% CI 0.27, 1.53; P = 0.31) compared to patients who had direct laryngoscopy. There was no statistically significant difference in Cormack-Lehane grade views of the glottis between direct and video laryngoscopy on the first attempt. In conclusion, there was no statistically significant improvement in the success rate of intubation on the first attempt when video laryngoscopy was used for patients undergoing general anesthesia for cesarean delivery.
Keywords: Cesarean section, general anesthesia, intratracheal intubation
The American Society of Anesthesiologists guidelines on obstetric anesthesia encourage regional anesthesia for cesarean delivery when possible but state that general anesthesia should be used when indicated.1 A review article described the potential advantages of using video laryngoscopy to manage the parturient airway during cesarean deliveries performed under general anesthesia.2 At our hospital, direct and video laryngoscopy are routinely used for airway management for cesarean deliveries performed with general anesthesia. For our primary outcome, we hypothesized that video laryngoscopy would have a higher success rate for endotracheal intubation on the first attempt compared to direct laryngoscopy for cesarean deliveries performed with general anesthesia.
METHODS
The Baylor Scott & White Research Institute institutional review board waived informed consent for this study. We used our electronic medical record system (Epic, Verona, WI) to search for patients who had cesarean deliveries with general anesthesia with endotracheal intubation performed in the operating room from July 1, 2017, through June 30, 2021. Detailed demographic and clinical data were entered by an investigator into Research Electronic Data Capture hosted at the Baylor Scott & White Research Institute.
Frequencies and percentages were used to describe categorical variables. We used the Kolmogorov-Smirnov test of normality to determine if a continuous variable had a normal distribution. For continuous variables that had a normal distribution, we used means and standard deviations. For continuous variables that did not have a normal distribution, we used medians and interquartile ranges. A chi-square test was used to test for associations in bivariate comparisons with cell counts of ≥5, and a Fisher’s exact test was used when cell counts were ≤4. We used a two-sample t test to test for differences in continuous variables that fit a normal distribution and a Mann-Whitney-U test to test for differences in continuous variables that did not fit a normal distribution. We performed a logistic regression to determine the odds ratio of successful intubation on the first attempt for video laryngoscopy compared to direct laryngoscopy. Statistical significance was determined by P values < 0.05.
RESULTS
A total of 364 patients had cesarean deliveries under general anesthesia with endotracheal intubation performed in the operating room. Two patients were excluded for incomplete airway documentation, and the remaining 362 patients were included for analysis. Of this group, 186 had direct laryngoscopy for the first intubation attempt, and 176 patients had video laryngoscopy. Demographic and clinical data for the cohorts are presented in Table 1. The odds ratio of successful intubation on the first attempt for video laryngoscopy was 0.64 (95% CI 0.27, 1.53; P = 0.31) compared to patients who had direct laryngoscopy. For patients who had direct laryngoscopy, 142, 15, 25, 3, and 1 patient had Macintosh 3, Macintosh 4, Miller 2, Miller 3, and a Phillips 2 blade used for their first laryngoscopy, respectively. For patients who had video laryngoscopy, 106, 9, 58, 2, and 1 patient had C-MAC® (Karl Storz, El Segundo, CA) 3, C-MAC® 4, C-MAC® D, GlideScope® 3 (Verathon, Bothell, WA), and a McGrath™ (Medtronic, Dublin, Ireland) blade used for their first laryngoscopy, respectively. Of the 9 patients who were not successfully intubated on the first attempt with direct laryngoscopy, none had video laryngoscopy used for the second intubation attempt.
Table 1.
Demographic and clinical data for groups with direct or video laryngoscopy at first attempt
|
Direct laryngoscopy
(N = 186) |
Video laryngoscopy (N = 176) |
P
value |
|
|---|---|---|---|
| Age (years): median (IQR) | 27 (23–32) | 28 (23–32) | 0.55 |
| Height (cm): mean (SD) | 162.2 (8.3)a | 162.0 (8.9)b | 0.83 |
| Weight (kg): mean (SD) | 89.8 (20.3)c | 104.7 (30.6)d | <0.01* |
| Body mass index (kg/m2): mean (SD) | 34.5 (6.8)e | 39.8 (10.3)f | <0.01* |
| Gravidity: median (IQR) | 2 (1–3) | 2 (1–4) | 0.76 |
| Parity: median (IQR) | 1 (0–2) | 1 (0–2) | 0.48 |
| Gestational age at delivery (weeks): mean (SD) | 36.2 (3.9) | 35.9 (4.4) | 0.53 |
| Prior cesarean delivery | 49 (26%) | 48 (27%) | 0.84 |
| Unscheduled cesarean delivery | 132 (71%) | 133 (76%) | 0.33 |
| Location of cesarean delivery | 0.25 | ||
| Labor and delivery suite | 175 (94%) | 160 (91%) | |
| Main operating room | 11 (6%) | 16 (9%) | |
| Indication for general anesthesia | 0.10 | ||
| Failure of regional anesthesia | 98 (53%) | 76 (43%) | |
| Perceived lack of time to initiate regional anesthesia | 62 (33%) | 78 (44%) | |
| Maternal comorbidities | 26 (14%) | 22 (13%) | |
| Time of day cesarean delivery start | 0.72 | ||
| 0700–1559 | 87 (47%) | 87 (49%) | |
| 1600–2359 | 59 (32%) | 57 (32%) | |
| 0000–0659 | 40 (21%) | 32 (18%) | |
| Airway secured on first attempt | 177 (95%) | 163 (93%) | 0.32 |
| Training of operator of first attempt | 0.15 | ||
| CA1 or intern | 104 (56%) | 116 (66%) | |
| CA2, CA3, or CRNA | 49 (26%) | 31 (18%) | |
| Attending | 33 (18%) | 29 (16%) | |
| Cormack-Lehane grade view of glottis on first attempt | 0.14 | ||
| 1 | 123 (66%) | 130 (74%) | |
| 2a | 48 (26%) | 26 (15%) | |
| 2b | 8 (4%) | 9 (5%) | |
| 3 | 3 (2%) | 4 (2%) | |
| 4 | 1 (1%) | 1 (1%) | |
| Not documented | 1 (1%) | 6 (3%) |
CA, clinical anesthesia [year of training]; IQR, interquartile range; SD, standard deviation.
aN = 125; b N = 136; c N = 129; d N = 139; e N = 117; f N = 131.
DISCUSSION
We found that there was not a statistically significant difference in the success rate of first-attempt endotracheal intubation when using video laryngoscopy compared with direct laryngoscopy for patients who had cesarean delivery under general anesthesia. We also found that there was not a statistically significant difference in the Cormack-Lehane view of the glottis between direct and video laryngoscopy on the first intubation attempt.
A randomized controlled trial that compared C-MAC™ and King-Vision® video laryngoscopy to direct laryngoscopy found no statistically significant difference in first-attempt success rates for endotracheal intubation in parturients who underwent cesarean delivery under general anesthesia.3 The same study found a statistically significant difference between video and direct laryngoscopy in the Cormack-Lehane view of the glottic opening. The Cormack-Lehane classification assigns numbers that correspond to how much of the glottic opening can be viewed by the operator, with 1 signifying a complete view of the glottic opening, 2 signifying a partial view of the glottic opening, 3 signifying a view of only the epiglottis, and 4 signifying a view of no discernible glottic anatomy.4
A recent Cochrane database review found that video laryngoscopy increased the chances of successful endotracheal intubation on the first attempt in adult patients.5 At our institution, it is customary for the resident assigned to the obstetric anesthesia service to perform the first intubation attempt for a patient who has a cesarean delivery under general anesthesia, but this is at the discretion of the attending anesthesiologist of record. As a result of this practice, most of the first attempts at intubation were performed by either interns or resident physicians in their first year of anesthesia training (CA1s) for both direct and video laryngoscopy.
A single-center study reported a failed intubation rate of 1:232 for cesarean deliveries performed under general anesthesia,6 while a multicenter study reported a rate of 1:5337 and a literature review reported a failed intubation rate of 1:443.8 We did not have any failed intubations for our 362 patients who had complete documentation of airway management.
We found that patients who had video laryngoscopy on the first intubation attempt had a statistically significant higher weight and body mass index. We believe that our anesthesiologists and anesthesia residents had a perception that obese patients have a higher risk for difficult intubation and chose video laryngoscopy for the first intubation attempt accordingly. However, the association between obesity and difficult intubation is unclear, and one review article characterized body mass index as just one of several factors that could potentially predict difficult intubation.9
Our study had several limitations. One limitation was that a meaningful subset analysis comparing obese to nonobese patients could not be performed, since 31% of our patients had missing data on body mass index. Another limitation was that our obstetricians do not have a consistent method of documenting the urgency of cesarean deliveries. We considered the absence of an attempt at regional anesthesia to be due to obstetric urgency when a specific patient comorbidity that contradicted regional anesthesia or a patient preference to avoid regional anesthesia was not documented and did not find that video laryngoscopy was preferentially used for apparent emergent cesarean deliveries.
The results of this study are generalizable to institutions where resident physicians training in anesthesiology predominantly perform airway management for cesarean deliveries under general anesthesia.
Disclosure statement/Funding
The authors have no relevant financial conflicts of interest to disclose. This study was departmentally funded.
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