|Year : 2021 | Volume
| Issue : 2 | Page : 90-95
Airway changes before & after delivery-does labour has any effect on the modified mallampati score?
Akshaya Kumar Das, Nikki Sabharwal, Meenakshi Kumar
Department of Anesthesia and Intensive Care, VMMC and Safdarjung Hospital, New Delhi, India
|Date of Submission||25-Mar-2021|
|Date of Acceptance||21-May-2021|
|Date of Web Publication||01-Oct-2021|
Dr. Meenakshi Kumar
A 224, Sector -31, Noida - 201 301, Uttar Pradesh
Source of Support: None, Conflict of Interest: None
Background: Changes in modified mallampati grade occur with the progress of pregnancy, labor, and delivery due to various reasons. This could lead to unanticipated difficulties in airway management, especially if the parturient were to undergo a surgical procedure in the postpartum period. Our study aimed to evaluate the change in airway parameters after delivery in parturient undergoing lower segment cesarean section (LSCS) under spinal anesthesia. Materials and Methods: This study was conducted at Vardhaman Mahavir (VMMC) and Safdarjung Hospital over a period of 18 months. A total of 160 patients posted for either elective or emergency cesarean section under spinal anesthesia were enrolled in the study (80 in each group). Airway parameters including modified mallampati grade (MMPG) were measured at various time intervals – before cesarean section (T1) and 2 h (T2), 6 h (T3), 24 h (T4), 48 h (T5), and 72 h (T6) after delivery and analyzed statistically. Results: Changes in MMPG occurred in 71.25% of cases in the emergency group as compared with 40% of cases in the elective group (P = 0.0001). The mean MMPG was significantly higher from 2 h up to 72 h after LSCS in the emergency group (having more patients in active labor). (P = 0.0001). Maximum changes in MMPG occurred 6 h after delivery in both groups. Normalization of MMPG to its precesarean value occurred earlier in elective patients (P = 0.0005). An association was found between the duration of labor and normalization of changes in MMPG to its preoperative value (P = 0.023). Conclusion: Airway changes in pregnant women are seen to worsen after emergency LSCS under spinal anesthesia and are affected by prolonged labor. Therefore, the maternal airway should be reassessed after the delivery of the baby, for any surgical procedure thereafter.
Keywords: Airway changes, labor, LSCS, modified Mallampati grade
|How to cite this article:|
Das AK, Sabharwal N, Kumar M. Airway changes before & after delivery-does labour has any effect on the modified mallampati score?. J Obstet Anaesth Crit Care 2021;11:90-5
|How to cite this URL:|
Das AK, Sabharwal N, Kumar M. Airway changes before & after delivery-does labour has any effect on the modified mallampati score?. J Obstet Anaesth Crit Care [serial online] 2021 [cited 2021 Dec 9];11:90-5. Available from: https://www.joacc.com/text.asp?2021/11/2/90/327416
| Introduction|| |
Obstetric anesthesia is a high-risk area of anesthetic practice due to the presence of a potentially difficult airway, and it remains the single most important cause of anesthesia-related maternal morbidity and mortality., Inadequate ventilation, esophageal intubation, and difficult intubation are the major contributors to adverse respiratory events. It is the seventh leading cause of maternal deaths in the United States.
The incidence of failed tracheal intubation in the pregnant population is eight times higher than in the general population, accounting for a drastic decrease in the use of, of general anesthesia for the cesarean section over the last few decades.
Various factors contribute to a potentially challenging airway in these patients. Amongst them are the anatomical and physiological changes of pregnancy such as capillary engorgement of the respiratory tract, mucosal edema due to estrogen level, weight gain, and large breasts.,,,, The risk of aspiration and thereby desaturation is increased due to cephalad elevation of the diaphragm and obesity. Furthermore, increased oxygen demand by the mother as well as the fetus and decreased expiratory reserve volume(ERV) and functional residual volume (FRC) can lead to ventilation-perfusion mismatch and early desaturation and hypoxia.
The mallampati score or mallampati classification is a simple, reproducible, and reliable preanesthetic airway assessment tool for difficult tracheal intubation.
Although the occurrence of airway changes during pregnancy and labor has been reported by many authors,,,,, there are very few studies predicting the factors which can increase the risk of difficult airway in these patients. We, therefore, conducted this study to find out the magnitude of airway changes and their predisposing factors in patients undergoing cesarean section under spinal anesthesia.
The primary objective was to evaluate the changes in modified mallampati grade, and the secondary objective was to evaluate changes in other airway parameters as well as the factors affecting it like labor and its duration before delivery and in the postpartum period, in parturient scheduled for cesarean section under spinal anesthesia. We hypothesized that the modified mallampati grade will improve after cesarean delivery in the study population.
| Materials and Methods|| |
After obtaining approval from the Hospital Ethical Committee, this prospective observational study was conducted in the Department of Anesthesia and Intensive care, Vardhaman Mahavir Medical College and Safdarjung Hospital, New Delhi.
As per the study conducted by M Boutonnet et al., mallampati class changes in 63% of patients during pregnancy, labor, and after delivery. Taking this value as reference, the minimum required sample size with a 7.5% margin of error and 5% level of significance with 80% power of the study was 160 patients.
The formula used to calculate the sample size was: -
ME = zα*Sqrt ((p (1 -p))/N)
Where Zα is the value of Z at a two-sided alpha error of 5%, ME is the margin of error, and p is the prevalence rate.
One hundred and sixty full-term patients scheduled to undergo elective or emergency cesarean section under spinal anesthesia were taken up for the study after obtaining a written informed consent from them.
All the patients, aged more than 18 years, having mono-fetal pregnancy of more than 37 weeks of gestation posted for LSCS under spinal anesthesia were included in the study and were divided into two groups of 80 patients each, undergoing elective or emergency LSCS. Those with morbid obesity, comorbid conditions such as heart disease, diabetes mellitus, eclampsia, coagulopathy, and patients with features of difficult airway were excluded from the study.
A detailed history and complete physical examination including airway assessment and all routine investigations were done. The parameters measured were height, weight, body mass index (BMI), and modified mallampati grade (MMPG), thyromental distance (TMD), sterno-mental distance (SMD), inter incisor distance (IID), neck circumference (NC), and height to thyromental distance (RHTMD). The number of patients in active labor and the duration of labor were also noted.
All the airway parameters were measured preoperatively (T0); 2 h. after delivery (T2); 6 h. after delivery (T6), 24 h after delivery (T24); 48 h after delivery (T48); and 72 h after delivery (T72).
In the operating room, standard monitors such as noninvasive blood pressure (NIBP), ECG, and pulse oximeter (SPO2) were applied. After recording the baseline vital parameters, vascular access was achieved through the superficial veins of the forearm.
Premedication and anesthesia
All patients received Inj. ranitidine 50 mg IV and Inj metoclopramide 10 mg IV and were transfused with 500 mL of warm Ringer lactate solution in the operation theatre before the subarachnoid block (SAB). After explaining the procedure to the patient, an SABwas given in a sitting position with a 25-G Quincke spinal needle at L2-L3/L3-L4 intervertebral space, using 1.8–2 mL of 0.5% heavy bupivacaine with or without fentanyl (10 μg). The patients were positioned supine on the operation table with a wedge under the right buttock after administration of SAB. The sensory block level was evaluated approximately 5 min later using a cold cotton swab. After confirmation of an adequate level of sensory block (T4-T5), surgery was allowed to proceed. Oxygen was administered to all patients through a facemask throughout the perioperative period. After the birth of the baby, an injection of oxytocin five units intravenous (i.v.) bolus was administered, and 15 units of oxytocin was added to the intravenous fluid. Warm intravenous fluids were administered as per requirement. Regular monitoring of systolic blood pressure (SBP), mean blood pressure (MAP), diastolic blood pressure (DBP), heart rate (HR) and SPO2, was done till the end of surgery.
Categorical variables were presented in number and percentage (%), and continuous variables were presented as mean ± SD and median. The normality of data was tested by the Kolmogorov-Smirnov test. If the normality was rejected, then a nonparametric test was used.
Statistical tests were applied as follows:
Quantitative variables were compared using the independent t-test/Mann-Whitney U test (when the data sets were not normally distributed) between the two groups. Paired T-test/Wilcoxon test was used for comparison within the group. Qualitative variables were correlated using the Chi-Square test/Fisher exact test. P value of <0.05 was considered statistically significant.
The data were entered in MS EXCEL spreadsheet, and analysis was done using Statistical Package for Social Sciences (SPSS) version 21.0.
| Results|| |
Both the groups were comparable for age, height, BMI, duration of surgery, the dose of bupivacaine, and dose of fentanyl as an adjuvant. [Table 1] In the elective group, only one patient (1.25%) was in active labor as compared to 73 patients in the emergency group (i.e. 91.25%). This difference was statistically significant (P < 0.0001). [Table 1].
The mean TMD, mean SMD, mean IID, mean NC, and mean RHTMD were 7.03 ± 0.29 cm, 13.64 ± 0.58 cm, 5.52 ± 0.24 cm, 34.58 ± 0.86 cm, and 22.16 ± 0.99 in elective caesarean group as compared to 7.01 ± 0.28 cm., 13.65 ± 0.63 cm, 5.46 ± 0.23 cm, 34.46 ± 0.83 cm, and 22.28 ± 0.98 in the emergency caesarean group in at all-time intervals, respectively. There were no changes in other airway parameters throughout the observation period. The mean parameters were comparable between the two study groups with a P value > 0.05 [Table 2].
There was a change in MMPG in 55.63% of patients in both the groups combined i.e. out of 160 patients, 89 patients exhibited a change. In the elective group, the change in MMPG from the baseline occurred in 40% of cases, whereas this change was detected in as many as 71.25% of cases in the emergency group. This was found to be statistically highly significant (P = 0.0001).
Out of the 40% cases (i.e. 32/80) in the elective group, showing changes in MMPG almost 90% (i.e., 29/32) had an increase of MMPG by 1, whereas only 9.38% (i.e., 3/32) had an increase in MMPG by 2. Out of the 71.25% cases (i.e., 57/80) in the emergency group showing changes in MMPG, 54.39% (i.e. 31/57) had an increase in MMPG by 1, whereas 45.61% (i.e. 26/57) patients had an increase in MMPG by 2. This difference was statistically significant (P = 0.0004) [Table 3].
We observed that in the elective group, at all-time intervals maximum percentage of patients were in MMPG grade I and grade II, whereas in the emergency group at 6 h and 24 h after delivery the percentage of patients in MMPG grade III and IV increased. [Table 4] This clearly pointed out the presence of preoperative labor and its effect on MMPG change in the emergency group. We observed that the mean MMPG at 2 h (T2), 6 h (T6), 24 h (T24) 48 h (T48), and 72 h (T72) was significantly higher in the emergency group as compared to the elective LSCS group with P values at different time intervals were 0.033, 0.004, 0.004, 0.004 and 0.031, respectively. Maximum mean MMPG was noted at 6 h and 24 h in both the groups [Graph 1].
Fifty-three of the 74 patients (71.62%) in active labor demonstrated a change in MMPG as compared to 36 of the 86 patients (41.86%) who were not in active labor. This difference was found to be statistically significant (P = 0.0002). MMPG started to change earlier (as early as 2 h afterdelivery) in patients in preoperative labor, and by 6 h a maximum number of patients (77.36% of those in labor, and 83.33% of those not in labor) in both the groups had manifested the change (P = 0.028). [Table 5].
|Table 5: Effect of Labor on time to peak changes in MMPG from pre delivery grade|
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The incidence of peak change in MMPG by grade 2 was higher in those patients with a labor duration of more than 10 h. This difference was found to be statistically and clinically significant (P = 0.007).
There was an association between duration of labor and return of MMPG to baseline preoperative value (P = 0.023). It is more significant when the duration of labor >10 h (P = 0.004). [Table 6]. The longer the duration of labor, the longer it took MMPG to revert to baseline.
|Table 6: Effect of duration of labor on normalization of MMPG to predelivery value|
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Normalization of MMPG to its precesarean value occurred earlier in patients who were not in active labor as compared to patients with active labor before LSCS. The normalization of peak MMPG occurred in 75% of cases at 48 h in patients not in active labor, whereas it occurred in 39.62% of cases at 48 h in patients with active labor, and the rest 58.49% cases took almost 72 h after delivery for normalization. The difference between the two groups was found to be statistically and clinically significant (P = 0.0004) [Graph 2].
| Discussion|| |
Though the majority of cesarean sections are performed under regional anesthesia, general anesthesia has a place when there is the inadequate effect of regional anesthesia or patient refusal for regional blocks, among others. The anatomical and physiological changes which occur during pregnancy, have a significant impact on the airway. These changes in the airway may persist for some time in the post-delivery period. Therefore, assessment of the airway is of paramount importance before proceeding with anesthesia for LSCS. Different studies have hypothesized probable causes of worsening of MMP grade during pregnancy and labor.,,, Pharyngeal edema due to fluid retention was the underlying cause for the worsening of MMPG in late pregnancy. Straining and Valsalva maneuver during labor aggravates airway edema. Intravenous fluids enhance this response by further decreasing oncotic pressure and aggravating airway edema. Increased return of blood by uterine contraction, tissue edema due to increased central venous pressure, and antidiuretic effect of oxytocin lead to persistence of airway changes after delivery of the placenta.,
Most of the studies have examined the airway during pregnancy, labor, and immediately after completion of the third stage of labor. However, few studies have assessed the airway changes in the post-partum period. So, we planned to study the effects of labor and duration of labor, on changes in airway parameters after delivery in patients posted for LSCS under spinal anesthesia.
In a study conducted by Pilkington et al. they examined the photographic version of mallampati class in pregnant women at 12 weeks of gestation and 38 weeks of gestation. They found out that there was a significant increase in Mallampati class at 38 weeks of gestation. There was a 34% enhancement of mallampati grade 4 at 38 weeks of gestation with P < 0.001. They found a relation between the gain in body weight and an increase in mallampati grade (r = 0.3, P < 0.001). We studied the influence of labor on MMPG changes, time of its maximum value, and time of normalization to its predelivery value. Morbidly obese patients were not part of our study, and most of the patients were within the normal BMI range.
We found that there was an increase in Modified Mallampati grade in 71.62% of patients with active labor (74 patients) up to 72 h postoperatively, whereas Pilkington et al. studied the airway of pregnant patients at 12 and 38 weeks. of gestation only with no comments about the changes in the airway occurring after delivery.
Kodali et al. evaluated the airway changes in patients undergoing labor. They found that there was a significant increase in airway class from pre-labor to post-labor value (P < 0.001). There was one grade increase in airway class in 33% of patients who showed an increase in airway class of 1 grade, and 5% of patients who showed an increase in airway class of 2 grades, which the authors attributed to mucosal edema of the airway. Straining and Valsalva maneuver during labor and pregnancy as well as intravenous fluids aggravated airway edema. We also observed that in cases with active labor a change in MMPG by 2 grades was seen in 23 patients (43.40%) as compared to only 6 patients (16.67%) in patients without active labor; hence, there is a definite relationship between the presence of active labor and magnitude of change in MMPG, the most probable cause for this being airway mucosal edema worsened by the presence of labor.
Hu et al. compared the airway changes between cesarean section and vaginal deliveries. Airway parameters such as MMPG, IID, TMD, SMD, and NC were measured at different time intervals. There was no significant difference in IID, TMD, NC, and SMD at different time points in the two groups. According to the authors of this study, a shorter observation period of duration of fewer than 30 h was the limitation of the study. We observed airway changes till 72 h after delivery and found no change in other airway parameters throughout the observation period, and both the groups were statistically comparable to these airway parameters. Hu et al. found that the peak MMPG class took place earlier i.e. 1 h after delivery in the case of the vaginal delivery group as compared to the cesarean group in which it occurred at 6 h after delivery. This finding is similar to our study finding which showed that the peak change in MMPG occurred 6 h after the delivery in both elective and emergency cesarean group.
In a study Boutonnet et al. the changes in mallampati class before, during, and after labor, and the factors influencing the change were evaluated. They assessed mallampati class in 87 patients with epidural analgesia for childbirth at four-time intervals: 8 months of pregnancy (T0), placement of an epidural catheter (T2), 20 min after delivery (T6), and 48 h after delivery (T24). Factors such as weight gain, duration of first and second stages of labor, and IV fluids administered were also evaluated for their predictive value. They found that mallampati class changed in 67% of patients in labor with epidural analgesia. No predictive factors were identified in their study. They included the parturients with active labor with epidural anesthesia for the study. We found that the changed MMPG was not fully reversed even 48 h after delivery. At 48 h postdelivery, normalization of MMPG occurred in 26 patients (81.25%) out of a total of 32 patients in whom a change in MMPG was seen in the elective group, whereas normalization occurred in 22 patients (38.60%) out of 57 patients in whom an increase/change in MMPG was seen, in the emergency group. In a total of 4 patients, the MMPG had not normalized even after 72 h of which 3 belonged to the emergency group, whereas 1 patient was of the elective group. The change in MMPG of four patients persisted even after 72 h In our study, we found that there was a relation between the presence of labor duration of labor for >10 h with normalization of MMPG to its predelivery value. Almost all patients in emergency LSCS group had active labor, and that was the probable cause behind the delayed normalization of MMPG as compared to the elective LSCS group.
Ahuja et al. conducted a prospective case-control study to evaluate and compare the airway changes during labor and delivery in normotensive and pre-eclamptic patients. Twenty-five normal and 25 pre-eclamptic patients were recruited for the study. The airway measurements were performed at three-time intervals; T0 before labor, T2 1 h after delivery of baby, and T6 at 24–48 h. post-partum. They found that there was a significant worsening of mallampati grade in both the groups, and it was comparable in both groups. A strong correlation was found between the total duration of labor and change of grade by one grade, mostly with the first stage of labor. They also found that mallampati grade did not return to its prelabor value even 48 h after delivery of the baby. Our result showed similar values in terms of worsening of MMPG after delivery, the association of total duration of labor and change of MMP grade, and normalization of MMP grade after delivery.
Strength of our study: Observations of MMPG and other airway parameters were performed till 72 h after LSCS.
Limitation of our study: We could not start the airway assessment from the early pregnancy period as most of the patients were admitted in late pregnancy or labor. The prospects of this study are to evaluate the influence of obesity, total fluid, and the dose of oxytocin administered during the hospital stay on changes in airway parameters.
| Conclusion|| |
Airway parameters seem to worsen even after a cesarean section is performed under spinal anesthesia. Change in MMPG post LSCS is affected adversely by the presence of labor and its duration. Airway changes during labor and after delivery are a dynamic process. Airway assessment of every patient should be done if they are posted for any surgical procedure such as resuturing, removal of retained placenta, etc., after delivery of the baby. Anesthesiologists should not rely on the previous airway assessment records and prepare for managing a difficult airway as the airway parameters may worsen after delivery.
DATE and PLACE OF PRESENTATION: AOA-2018 (11TH National Conference of Association of Obstetric Anesthesiologists) on 30th September, Jodhpur.
The study was registered in Clinical Trial Registry -India (CTRI) with CTRI No-CTRI/2018/04/013355.
Individual role of each authors:
Dr. Akshaya Kumar Das is the principal Investigators and Dr. Nikki Sabharwal is the Co-Investigator. Dr. Meenakshi Kumar has helped in writing discussion and statistical work.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]