Comparative Evaluation between Sevoflurane and Propofol for Endotracheal Intubation without Muscle Relaxants in Pediatric Cleft Surgeries.

BACKGROUND AND OBJECTIVES: Endotracheal intubation is the most important and crucial step during administration of general anesthesia. It is more so in pediatric patients with associated deformities of cleft lip, palate, and alveolus. Propofol, an intravenous (i.v.) induction agent, has profound depressant effect on airway reflexes with a quick and smoother induction. Similarly, sevoflurane, an inhalational agent, has relatively pleasant smell, low airway irritability, and more cardiostable properties. Hence, we sought to compare effectiveness of propofol with sevoflurane in achieving good intubation conditions without the use of muscle relaxants.
MATERIALS AND METHODS: In this prospective randomized study, eighty children belonging to American Society of Anesthesiologist physical status Class I and II, aged 1-10 years, scheduled for cleft surgery were included. All participants were premedicated. Patients were allotted to Group A and Group B randomly. Group A received propofol and Group B received sevoflurane as induction agents. Tracheal intubation was attempted in all patients at 150 s. Intubation conditions were assessed by using Steyn modification of Helbo-Hansen intubating conditions score. Statistical analysis was done using Student's t-test and Chi-square test with P < 0.05 regarded as significant.
RESULTS: Group B patients receiving sevoflurane had significantly more clinically acceptable intubation conditions than patients of Group A receiving i.v. propofol (P = 0.001).
CONCLUSION: We conclude that intubation conditions using inhalational 8% sevoflurane are superior to i.v. propofol of 3 mg/kg for tracheal intubation without muscle relaxants in children undergoing cleft surgeries.

INTRODUCTION

Endotracheal intubation is a very important and crucial step during administration of general anesthesia. It is more so in pediatric patients, especially if there are associated deformities in and around the airway like cleft lip and palate.

Although the use of neuromuscular blocking agents made the technique of endotracheal intubation much easier, it posed several potential risks to the patients. Until early 1990s, suxamethonium was the only drug for facilitating tracheal intubation due to its rapid-onset and ultra-short duration of action, but it had many potential side effects such as myalgia, elevated intraocular and intracranial pressure, hyperkalemia, masseter spasm, and malignant hyperthermia.[1234] The fatal or near fatal cardiac arrest incidence that occurred in children who received suxamethonium was attributed to hyperkalemia due to undiagnosed muscular dystrophies.[5] In 1993, United States Food and Drug Administration contraindicated the use of suxamethonium in children and adolescents; however, decision was revoked later but continued to carry a warning cautioning against its use in children.[5]

Nondepolarizing neuromuscular blocking agents are an alternative but they are slower in onset, have a prolonged neuromuscular blockade, and paralysis cannot be reversed quickly if airway management through mask or tracheal intubation fails.[134] Hence, avoiding muscle relaxants when they are not required for planned procedure may prevent complications of their use, misuse, and antagonism. Hence, we sought to provide a method of good intubation conditions rapidly without using muscle relaxants.

With the advent of potent short-acting opioid drugs and newer intravenous (i.v.) induction agents which are good in suppressing airway reflexes, possibility of intubating the trachea without muscle relaxants has been under evaluation. Propofol is found to be the most favorable induction agent due to its profound depressant effect on airway reflexes, pharyngeal and laryngeal activities and muscle tone.[4678] Induction with propofol is quick and smooth with rapid awakening and orientation during recovery.[4]

On the other hand, of the available inhalational agents, sevoflurane has relatively pleasant smell, low airway irritability, low blood gas solubility, less myocardial depression, and arrhythmogenicity, thus promising good intubation conditions.[91011] Currently, sevoflurane has been hailed as the inhalational agent of future. Furthermore, there is paucity of literature for comparisons of sevoflurane with propofol for endotracheal intubation among the south Indian children undergoing cleft surgeries. With this background, a study was conducted to compare the intubation conditions achieved by sevoflurane with that of propofol among children undergoing cleft surgeries.

MATERIALS AND METHODS

Eighty pediatric patients aged between 1 and 10 years of both the sexes belonging to American Society of Anesthesiologists physical status Classes I and II posted for cleft lip, cleft palate, and cleft alveolus surgery under general anesthesia in a private hospital of South India were included in this study. Study participants were included according to convenience sampling method. Children with history of significant cardiac, respiratory, renal, hepatic, or central nervous system diseases, with anticipated difficult airway and having active or recent upper respiratory tract infection were excluded from this study. Ethical clearance was obtained from the Institute's Ethics Committee. A written informed consent was taken from all the parents/guardians of the study participants after describing in full detail the nature and purpose of this study.

A thorough preanesthetic evaluation was done to assess the general conditions and status of cardiovascular, respiratory, and central nervous system. All the patients were made to fast for 6 hours for solids and milk and 2 hours for clear fluids. They were premedicated with a combination of midazolam 0.5 mg/kg and atropine 20 μg/kg orally, 45 min before the surgery. Eutectic Mixture of Local Anesthetics cream was applied to dorsum of hand 1 hour before surgery.

Patients were randomly allocated using envelope method into two groups: Group A and Group B. Patients belonging to Group A were administered propofol and those belonging to Group B were given sevoflurane. Patients were shifted to OT and i.v. access was established. Preoperative baseline values of heart rate (HR), blood pressure, and oxygen saturation were recorded, and infusion of crystalloid lactated Ringer's solution was started according to “4-2-1” formula which is based on body weight and hours of fasting.

Both the groups received 2 μg/kg of fentanyl i.v. over 30 s. After 5 min, patients belonging to Group A received 3 mg/kg of propofol i.v. Lignocaine 0.2 mg/kg was added to propofol solution to abolish pain on injection; speed of injecting propofol was about 30 mg/10 s. Group B patients received 8% sevoflurane through a face mask connected to Mapleson F breathing circuit after priming the circuit with 8% sevoflurane.

All patients received 50% nitrous oxide in O2 through Mapleson F circuit. After loss of eyelash reflex, intermediate positive pressure ventilation was commenced. Tracheal intubation was attempted in all patients at 150 s and performed using appropriate-sized oral Ring, Adair and Elwin (RAE) tubes.

Intubation conditions were assessed by using Steyn modification of Helbo–Hansen intubating condition scoring system wherein the ease of laryngoscopy, position of the vocal cords, presence of coughing, degree of jaw relaxation, and amount of limb movements were assessed.[1]

Intubation conditions were considered adequate only when scoring was ≤2 in all categories and unacceptable if scoring was >2 even in a single category.

An additional bolus of 1 mg/kg of propofol i.v. was given if laryngoscopy was not possible due to coughing or excessive movement. In those patients where intubation was impossible after 2 attempts due to any cause, suxamethonium 1 mg/kg i.v. was injected and intubation was completed.

HR, blood pressures, and O2 saturation were monitored continuously and recorded. Complications if any were noted down. After intubation, anesthesia was maintained with 66% nitrous oxide in oxygen with 1 minimum alveolar concentration sevoflurane. Muscle-relaxant vecuronium 0.1 mg/kg i.v. was given after the intubation.

Intubation time, i.e., time taken from insertion of laryngoscope into the oral cavity till the removal of laryngoscope and number of attempts of tracheal intubation were noted.

Statistical analysis was performed using Student's unpaired t-test to analyze the time taken for intubation, number of attempts for intubation, and hemodynamic parameters such as baseline HR, systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial pressure (MAP) between the two groups. Chi-square test was used to analyze intubation conditions and occurrence of any complications between the two groups. P < 0.05 was considered as statistically significant.

RESULTS

Both Group A and Group B were matched for age, weight, and gender [Table 1].

Table 1

Demographic data and other characteristics

Intubation time was similar in both the groups. Intubation conditions were clinically acceptable in only 52.5% of patients in Group A as compared to 87.5% in Group B, which was significantly less (P = 0.001) [Table 1].

The two groups were comparable with respect to laryngoscopy, vocal cord position, and jaw relaxation. Patients of Group A had significantly more coughing than patients of Group B (P = 0.001). Patients of Group A had significantly more limb movements than patients in Group B (P = 0.001) [Table 2].

Table 2

Steyn modification of Helbo–Hansen intubating condition scoring system

From the above results, overall intubation conditions were significantly better in Group B receiving inhalational 8% sevoflurane as compared to Group A receiving propofol i.v.

Tables 3 and 4 show the baseline hemodynamic parameters, namely HR, SBP, DBP, and MAP and were found to be comparable between both the groups.

Table 3

Hemodynamic parameter Group A

Table 4

Hemodynamic parameter Group B

Figures 1–4 depicting the SBP, DBP, and mean arterial blood pressure showed no significant difference between the two groups following induction and intubation. There was no significant change in arterial oxygen saturation in Group A compared to Group B during the study period.

Figure 1

Comparison of heart rate changes between the two groups

Figure 4

Comparison of mean arterial pressure changes between the two groups

Comparison of systolic blood pressure changes between the two groups

Comparison of diastolic blood pressure changes between the two groups

The following adverse events were noted in our study. In Group A, two patients required succinylcholine for intubation because of excessive coughing and limb movements during intubation. Three children had O2 desaturation in Group B due to laryngospasm, and two of them required succinylcholine for intubation. In addition to this, one patient had bronchospasm. These were not found to be statistically significant between the two groups.

DISCUSSION

Laryngoscopy and tracheal intubation are essential skills associated with practice of anesthesia. Intubation can be successful following either deep anesthesia, paralyzed patient or if the anesthesiologist is stronger than the patient.[12] Good intubation conditions could be achieved by appropriate combination of hypnotic, analgesics and neuromuscular blockers with minimal compromise of the hemodynamic parameters.[12]

Succinylcholine was known to provide ideal intubation conditions for endotracheal intubation. However, with the potential fatal complications that arose from its use in pediatric anesthesia, its use has been limited only for rapid sequence induction of anesthesia.[1234]

Use of nondepolarizing muscle relaxant in an anticipated difficult airway can quickly turn into a “cannot ventilate, cannot intubate” situation.

Over the past few years, newer generation of induction agents such as propofol and sevoflurane with potential benefits of early induction and recovery and abolition of upper airway reflexes with minimal airway complications have been making a mark in the pediatric anesthesia care and are being often used without accompanying muscle relaxants for intubation.[3678]

Cleft lip, palate, and alveolus surgical interventions pose potential threats for maintaining airway, laryngoscopy, and intubation following induction.[4] The goal in cleft lip and palate surgery is to maintain the airway integrity with preservation of spontaneous respiration following induction. This can be achieved by newer drugs such as sevoflurane and propofol.

We found that 87.5% of patients of Group B receiving 8% inhalational sevoflurane had clinically acceptable intubation conditions as compared to only 52.5% of Group A receiving propofol i.v. A similar study done in South India has demonstrated that 8% sevoflurane provided good intubation conditions in cleft surgeries in comparison to propofol which is in line with our findings.[5] A study done in UK also found that anesthetic induction and tracheal intubation after sevoflurane 8% in 60% nitrous oxide in O2 given for 3 min is superior to i.v. induction with low-dose alfentanil and propofol.[8]

However, when a study was conducted on varying doses of propofol, it was found that 3 mg/kg preceded by fentanyl 3 μg/kg was found to be optimal dose combination.[3] Similarly, a latest study has propounded that the combination of 3 μg/kg of fentanyl and 3 mg/kg of propofol can be an effective replacement for gold standard suxamethonium for endotracheal intubation.[13]

In our study, two factors that made the intubation scores unacceptable among most cases were coughing and limb movements. Patients receiving propofol experienced more cough and limb movements during intubation than those receiving sevoflurane. Our findings are in line with the findings of other studies.[1348]

When hemodynamic parameters were studied, we found that postinduction and postintubation with 8% sevoflurane in 50% nitrous oxide in O2, HR had no significant change. Propofol was found to have a significant reduction in HR following induction. Unlike sevoflurane, the fall in HR could be attributed to inhibition of baroreceptor reflex by propofol. SBP, DBP, and MAP were not significantly different in the two groups. Thus, we can safely tell that sevoflurane is hemodynamically more stable than propofol. However, a signifi cant fall in HR, SBP, DBP, and MAP with the use of propofol has been documented by Rajan et al., and Shaikh et al.,[414] Gupta et al. found a significant fall in HR and MAP at doses of 3.5 mg/kg.[3] Blair et al. showed a significant fall in HR in propofol alfentanil than 8% sevoflurane in 60% nitrous oxide and Naziri et al showed a significant decrease in HR and SBP following induction with propofol and remifentanil.[815]

Poor intubation condition achieved with propofol fentanyl combination forms the drawback of this study. Our study also had difficulty in blinding the groups since sevoflurane is inhalational and propofol is an i.v. agent. The findings following effective blinding in future trials might lead to modification of the scoring system presently used.

Intubation condition achieved by either increasing dose of fentanyl to 3 μg/kg or by adding lidocaine 1.5 mg/kg i.v. or topical laryngeal spray before intubation can be evaluated in future trials and is the future scope of this study.

Use of large doses of propofol i.v. might push the child to apnea more easily which might negate the advantages, as more drugs need to be redistributed from vessel-rich organs and metabolized for return of spontaneous respiration and awakening.

CONCLUSION

A combination of 8% sevoflurane in 50% nitrous oxide with oxygen preceded by fentanyl 2 μg/kg without muscle relaxants had more acceptable intubation conditions and good hemodynamic stability compared to combination of propofol 3 mg/kg preceded by fentanyl 2 μg/kg in children undergoing cleft surgeries. Greater number of children in the propofol group had coughing and limb movements during intubation which contributed to the poor response. Therefore, intubation conditions using 8% sevoflurane in 50% nitrous oxide with oxygen are superior to i.v. propofol 3 mg/kg in children undergoing cleft surgeries.

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Nil.

Conflicts of interest

There are no conflicts of interest.