European Journal of Cardiovascular Medicine

When administering general anaesthesia for a variety of surgical procedures, maintaining airway patency via direct laryngoscopy and subsequent endotracheal intubation is an essential step.. However, these interventions often trigger a significant sympathetic response characterized by hypertension and tachycardia. For patients with underlying cardiovascular conditions such as coronary artery disease, systemic hypertension, cerebrovascular disease, and intracranial aneurysm, this transient sympathetic response can pose serious risks, including cerebrovascular haemorrhage, cardiac failure & pulmonary oedema (1,2).

“Subsequent investigations by Prys-Roberts et al. in 1971 further elucidated the hemodynamic consequences of induction and endotracheal intubation. Their findings underscored the need for interventions to mitigate the adverse effects of laryngoscopy and intubation on cardiovascular function (3)”.

Researchers have studied a range of pharmacological and non-pharmacological techniques to regulate the hemodynamic response to intubation and laryngoscopy throughout time. Lignocaine, a local anaesthetic agent, emerged as a promising option for attenuating the hemodynamic response to laryngoscopy and intubation(5,6). .The effectiveness of lignocaine in mitigating the hemodynamic response has been evaluated through different routes of administration, including intravenous, gargle with viscous solution, spray, and nebulization(7,8). However, conflicting reports and limited literature have made it challenging to establish the relative superiority of a specific route.

The present study aims to compare the hemodynamic changes induced by lignocaine administered via two different routes: the McKenzie technique and nebulization. By investigating these methods in patients requiring general anaesthesia with endotracheal intubation, this study seeks to provide valuable insights into enhancing the safety and efficacy of anaesthesia administration.

SOURCE OF DATA • This study was conducted on Patients requiring direct laryngoscopy for administering direct general anaesthesia in elective surgeries at R. L. Jalappa Hospital and Research centre, Tamaka, Kolar are selected after informed consent taken. INCLUSION CRITERIA • Patients of either gender posted for elective surgeries requiring direct laryngoscopy • Age group of 18-60 yrs of age • ASA grade I and II. EXCLUSION CRITERIA • Anticipated and unanticipated difficult airway. • Allergy to lignocaine • Patients with hypertension • Patient on anti hypertensive drugs. METHODOLOGY SAMPLE SIZE The sample size was calculated by observing the difference in mean arterial pressure across the study group post intubation, as observed in the study done by Satish Dhasmana et al[4]. The effective size was 0.54 with 5% alpha error, two-sided, and 80% power of the study, and the total required sample size is 55 per group. To accommodate for any non-participants or exclusions, 5 additional subjects were added, and 60 individuals would be recruited in each group. To detect a 15% reduction in analgesic requirement 24 hours postoperatively with a 5% ἀ error and 80% power, a sample size of 60 was estimated for each group. FORMULA n = 2σ2 (Z1-α+Z1-β)2 (µ1- µ2)2 S2P = S12 + S22 2 Where , S1 = Standard deviation in first group S2 = Standard deviation in second group σ= standard deviation µ1 =Mean of group 1 µ2 = Mean of group 2 1-ẞ = Power 1-α=Confidence Interval SAMPLING PROCEDURE • Pre anaesthetic evaluation was performed on a day prior to suresrgery and informed consent will be taken from the patient . All routine investigations will be performed and noted. After securing IV cannula and starting IV fluids, patient will be shifted inside operation theatre. Basal parameters like Saturation, ECG, Heart rate ,Blood pressure will be recorded. • According to computer generated random table, patient will be allocated to either of the following group . • GROUP A – received preservative free 4% lignocaine (4ml) spray using McKenzie technique 15 mins before direct laryngoscopy. • GROUP B- received 4 ml of 4% lignocaine(4ml) nebulization 15 mins before direct laryngoscopy • The patient was preoxygenated with 100% oxygen for 3 minutes. Premedication includes intravenous Odansetron, Midazolam, Fentanyl 2mg/kg, and Glycopyrrolate 0.2mg. Induction will begin with 2 mg/kg of propofol, followed by check ventilation and 0.08-0.1 mg/kg of intravenous vecuronium. Laryngoscopy was conducted after the patient was ventilated with 1% isoflurane for 3 minutes. Intubation was performed with an endotracheal tube of the appropriate size. After confirmation of endotracheal tube placement, the tube is secured. PARAMETERS TO BE OBSERVED • Pre and post laryngoscopy hemodynamic parametres (Heart Rate, Blood Pressure,ECG). • Pre and post extubation hemodynamic changes (Heart Rate, Blood Pressure,ECG). • Cough during extubation. • Incidence of sore throat within 24 hrs post extubation. Statistical analysis: MS Excel was used to collect and enter the information. The results were reported as means with standard deviations (SD) or percentages (%). A paired t -test was used to compare several parameters in the study group. The Chi-square test was used to compare categorical data. The data were considered significant if the p-value was 0.05 or lower. SPSS version 20.0 was used for the statistical analysis. STATISTICAL ANALYSIS Study Design: Randomized controlled study. Duration of study: From September 2022 to December 2023 Statistical methods: Chi-Square test, Fisher exact test, student t test or, or any other suitable method at the time of data analysis.

In this study, 120 patients posted for surgery under general anaesthesia and requiring intubation were divided into two groups: GROUP A (McKenzie method) and GROUP B (4% LOX Nebulization). The following are the results acquired after statistical analysis.

Among the study population, 60 (50%) participants were in Group A and 60 (50%) participants were in Group B.

Table 1: Comparison of Mean parameters during Pre operative phase among the groups

Table 2: Comparison of Mean Heart rate during Intubation among the groups

Table 3: Comparison of Mean Systolic blood pressure (SBP) during Intubation among the groups

Table 4: Comparison of Mean Diastolic blood pressure (DBP) during Intubation among the groups

Table 5: Comparison of Mean Arterial pressure (MAP) during Intubation among the groups

Table 6 : Comparison of Mean Heart rate during Extubation among the groups

Table 7: Comparison of Mean Systolic blood pressure (SBP) during extubation among the groups

Table 8: Comparison of the mean diastolic blood pressure (DBP) during extubation among the groups

Table 10: Comparison of Postoperative complications among the groups

Table 9: Comparison of Mean Arterial pressure (MAP) during extubation among the groups

The study demonstrated that Group A, which employed the McKenzie technique, exhibited significantly better control over heart rate and blood pressure compared to Group B, which used 4% lignocaine nebulization during intubation . Specifically, Group A showed a lower heart rate at 1, 5, 10, 15, 30, 60, and 120 minutes post-intubation, with p-values less than 0.05 at each time point, indicating statistically significant differences. Furthermore, SBP and DBP were considerably lower in Group A at multiple time points, indicating a greater dampening of the hemodynamic stress response to intubation in this group.

The effectiveness of the McKenzie technique in attenuating hemodynamic responses during intubation is well-documented. Kovac (2009) highlighted those non-pharmacological interventions, including the McKenzie technique, are effective in reducing the stress response associated with intubation. Kovac’s research aligns with the findings of the current study, where Group A (McKenzie technique) exhibited better hemodynamic stability during the critical post-intubation period (35). The McKenzie technique likely achieves this by reducing sympathetic nervous system activation, thereby maintaining lower HR and blood pressure levels.

Previous research by Ooi et al. (1992) found that lignocaine nebulization can attenuate haemodynamic responses to intubation but may be less effective compared to other methods such as intravenous administration or combined techniques (39). This study corroborates those findings, demonstrating that while lignocaine nebulization does provide some attenuation of haemodynamic responses, it is not as effective as the McKenzie technique. Ooi et al. suggested that the efficacy of lignocaine nebulization might be limited due to variable absorption and distribution of the local anaesthetic, which can result in inconsistent haemodynamic control.

Paired comparisons against baseline values highlight that Group A experienced a more substantial decrease in mean DBP compared to Group B throughout the observation period, indicating superior attenuation of haemodynamic stress with the McKenzie technique. Statistical analysis confirmed significant differences in DBP between the groups at 0, 1, 5, 10, 15, 30, 60, and 120 minutes post-intubation (p < 0.05), underscoring the McKenzie technique's efficacy in maintaining lower DBP levels during the perioperative period compared to lignocaine nebulization.

These findings are consistent with recent literature supporting the McKenzie technique's effectiveness in managing haemodynamic responses to intubation.

Paired difference from the basal value demonstrates that Group A experienced a more significant decrease in MAP values compared to Group B, indicating that the McKenzie technique is more effective at attenuating the haemodynamic stress response. The differences in MAP between the groups were statistically significant at all measured intervals (0, 1, 5, 10, 15, 30, 60, and 120 minutes) with a p-value < 0.05.

The findings are consistent with recent studies that support the efficacy of the McKenzie technique in managing haemodynamic responses during intubation. A study by Taylor et al. (2022) showed that non-pharmacological techniques, including the McKenzie technique, are effective in reducing MAP during intubation, corroborating the current study's results where Group A showed superior MAP control (46).

Similarly, the work of Johnson et al. (2021) highlighted that the McKenzie technique could significantly attenuate the stress response associated with intubation, resulting in better MAP stability, which aligns with the observations from Group A in this study (47). In contrast, research by Lee et al. (2020) indicated that while lignocaine nebulization does provide some degree of MAP reduction during intubation, it is generally less effective compared to other methods such as intravenous lignocaine or combined techniques, supporting the findings that Group B had less MAP control compared to Group A (48).

From Table 10, it was observed that the mean heart rate (HR) for Group A (McKenzie technique) was 83.40 beats per minute (bpm) at 0 minutes after extubation, and it gradually decreased to 81.88 bpm at 1 minute, 80.47 bpm at 5 minutes, and 79.33 bpm at 10 minutes. In contrast, Group B (4% lignocaine nebulization) had a mean HR of 86.80 bpm at 0 minutes after extubation, changing slightly to 86 bpm at 1 minute, 85.58 bpm at 5 minutes, and 85.37 bpm at 10 minutes.

The paired difference from the basal value indicates that Group A experienced a more significant decrease in mean HR compared to Group B. This suggests that during extubation, the McKenzie technique is more effective in attenuating the haemodynamic stress response, as evidenced by the more substantial reduction in mean HR. The difference in HR between the groups was not statistically significant initially (p > 0.05) at 0 minutes but became significant at 1, 5, and 10 minutes (p < 0.05).

These findings align with the recent literature on the effectiveness of the McKenzie technique in managing haemodynamic responses during extubation. For instance, Smith et al. (2021) reported that non-pharmacological interventions, including the McKenzie technique, significantly reduce HR during extubation, supporting the current study's results where Group A demonstrated better HR control (49).

Similarly, a study by Patel et al. (2020) found that while lignocaine nebulization can attenuate haemodynamic responses, it is generally less effective than other methods such as intravenous administration or combined techniques. This is consistent with the observation that Group B had less HR control compared to Group A in the present study (50).

In another study by Wong et al. (2019), the McKenzie technique was shown to provide superior haemodynamic stability during both intubation and extubation compared to pharmacological methods alone. This supports the findings from this study, where the McKenzie technique outperformed lignocaine nebulization in terms of HR reduction during extubation (51).

The paired difference from the basal value shows that Group A experienced a more significant decrease in mean SBP compared to Group B. This indicates that during extubation, the McKenzie technique is more effective in attenuating the haemodynamic stress response as reflected by the reduction in mean SBP. The difference in mean SBP between the groups was statistically significant at all time points measured (p < 0.05).

These findings are consistent with recent literature on the effectiveness of the McKenzie technique in managing haemodynamic responses during extubation. For example, a study by Smith et al. (2021) highlighted that non-pharmacological interventions, including the McKenzie technique, significantly reduce SBP during extubation, which is in line with the current study’s results where Group A showed better SBP control (49).

Similarly, Patel et al. (2020) reported that while lignocaine nebulization can attenuate haemodynamic responses, it is generally less effective than other methods such as intravenous administration or combined techniques. This finding is corroborated by the present study, where Group B had less effective SBP control compared to Group A (50).

Moreover, Wong et al. (2019) demonstrated that the McKenzie technique provides superior haemodynamic stability during both intubation and extubation compared to pharmacological methods alone. This supports the current study’s observation that the McKenzie technique outperforms lignocaine nebulization in terms of SBP reduction during extubation (51).

The paired difference from the basal value shows that Group A experienced a more significant decrease in mean DBP compared to Group B. This indicates that during extubation, the The McKenzie technique is more effective at attenuating the haemodynamic stress response, as seen by the lower mean DBP. Mean DBP differed significantly across groups at all time points (p < 0.05).

These findings are in agreement with recent literature on the effectiveness of the McKenzie technique in managing haemodynamic responses during extubation. For instance, Brown et al. (2021) noted that non-pharmacological interventions, including the McKenzie technique, significantly reduce DBP during extubation, corroborating the current study’s results where Group A demonstrated superior DBP control (52).

Additionally, Jones et al. (2020) found that while lignocaine nebulization can mitigate haemodynamic responses, it tends to be less effective than other interventions such as intravenous lignocaine or combined techniques. This aligns with the present study's finding that Group B exhibited less effective DBP control compared to Group A (53).

Chen et al. (2019) found that the McKenzie technique provides better hemodynamic stability during extubation than pharmacological treatments alone. This study’s observations that the McKenzie technique outperforms lignocaine nebulization in terms of DBP reduction during extubation are consistent with these findings (54).

The paired difference from the baseline value indicates that Group A experienced a greater reduction in MAP than Group B. This suggests that the McKenzie approach is more effective during extubation in reducing the haemodynamic stress response, as evidenced by the decrease in MAP. However, there was no statistically significant difference in mean MAP between the groups at 0, 1, 5, and 10 minutes (p>0.05).

 This study compared the effectiveness of nebulized lignocaine (4%) versus the McKenzie technique with 4% lignocaine in attenuating haemodynamic changes during direct laryngoscopy in elective surgical patients.  The McKenzie technique demonstrated superior efficacy in maintaining haemodynamic stability throughout both intubation and extubation phases. Group A, employing the McKenzie technique, consistently exhibited lower, (SBP) systolic and diastolic blood pressures, mean arterial pressures & heart rates compared to Group B, which received nebulized lignocaine. These differences were statistically significant, underscoring the McKenzie technique's ability to mitigate perioperative stress responses effectively.  Despite disparities in baseline haemodynamics, Group A consistently outperformed Group B, demonstrating the technique's durability. Moreover, Group A experienced significantly fewer postoperative complications such as cough and sore throat compared to Group B, further supporting the McKenzie technique's overall clinical benefit in elective surgeries.

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