Akanksha Aggarwal

Department of Anaesthesia, Dr MK Shah Medical College & SMS Hospital, Ahmedabad, Gujarat, INDIA.

Email: agg.akanksha@gmail.com

Table 1: Intubation Condition Scoring

Successful intubation was defined as excellent intubation conditions when all variables were excellent. On finding suboptimal conditions second dose of rocuronium 0.3 mg/kg was administered. Hemodynamic variables were measured and recorded at the following times: pre-induction value; following fentanyl; after propofol; before laryngoscopy; 1 min after intubation. SPSS 11.0 (SPSS Inc., Chicago, IL, USA) was used to perform statistical analyses. A two-sample Z-procedure was used to compare time between the two groups. Values are expressed as the mean ± SD or median [interquartile range] or number of patients (%). Unpaired t test was used to compare patients’ characteristics and induction profiles. To compare the MAP and HR between the groups at each time point, an independent t test was used. Significance was defined as P<0.05.

RESULTS

All 75 patients completed the study satisfactorily. Demographic data and the baseline vitals were comparable in all three groups. Right herniotomy followed by left herniotomy was the most common surgical procedures. Heart rate and MAP of various groups at different time intervals are shown in Table 2 and 3 respectively.

Table 2: Heart rate at different times in all groups

Table 3: Mean Arterial Pressure at different times in all groups

Study revealed that mean pulse rate of atropine group was higher as compared to other groups. There was statistically significant change in pulse rate after the bolus dose of propofol, just before laryngoscopy and 1 minute after intubation observed in all three groups however changes were most significant in control group. For mean arterial pressure, study revealed statistically significant changes amongst all three groups from preinduction values to that after fentanyl administration and after the bolus dose of propofol. However, there was no significant change just before laryngoscopy and 1 minute after intubation. Intragroup analysis showed significant changes at various time intervals compared to pre induction values across all three groups. Using the Dixson’s up and down method the mean intubation time for patients of Group A was 136.52±13.88 seconds, of Group B was 98.32±10.39 seconds and of Group C was 117.00±13.83 seconds. Only 36% patients in Group A were intubated in less than 120 sec compared to 100% in Group B and 88% in Group C. Laryngoscopy was found to be difficult in 16% patients in Group A and C but only 4% patients Group B. Vocal cord was abducted in 60%, 72% and 64% in Groups A, B and C respectively. Ideal conditions were found in most of the patients in all three groups. Group B had highest proportion of patients with ideal intubation conditions however, the intergroup difference in proportion was not statistically significant. Second dose of rocuronium was required in 60% (Group A), 32% (Group C) but only in 16% of Group B patients. No complications were seen in any of the three groups.

DISCUSSION

A study by Eikermann et al.⁷ reported high dose of rocuronium (0.5–1.0 mg/kg) did not result in improvement of intubation conditions. With high dose, time for complete neuromuscular recovery is too long for short pediatric procedures. Low dose rocuronium in such a setting is preferable. We studied mean time for a low dose of rocuronium (0.3 mg/kg) that is required for successful tracheal intubation during iv anesthesia induction using propofol and fentanyl. The study proves that atropine (10 lg/kg) can reduce mean time of intubation with low dose rocuronium. The onset time for rocuronium (0.3 mg/kg) has been reported to be 87.3 s (range 30–150 s) in healthy children under halothane anesthesia.^8,9 However, we found that the time for successful tracheal intubation in 50 % of children was more than 90 seconds in both groups under i.v. anesthesia induction with rocuronium (0.3 mg/kg). One possible explanation for the different results may be that Driessen et al.⁷ used halothane anesthesia, which dramatically increases the neuromuscular blockade and shortens the onset time of any muscle relaxant compared to intravenous anesthesia. The onset of neuromuscular blocking agent action is reportedly influenced by the potency of the agent itself, the injected dosage, and circulation factors, which may influence its course to the neuromuscular junction.^10,11 An earlier study comparing the change in cardiac output before and after the administration of atropine demonstrated that i.v. atropine (10 lg/kg) could induce a significant increase in cardiac output during constant rate infusion of propofol in adult patients.¹² In this study, although cardiac output was not measured during anesthesia induction, HR was higher in the atropine group than in the control group during the study period. Therefore, in this study, atropine may increase cardiac output, with resultant favorable effects on rocuronium as well as i.v. anesthetics. In pediatric anesthesia¹¹, reducing the time required for the mask ventilation is very important during anesthesia induction. This study hence focused on the time for successful intubation rather than dose of anesthetic used. Thus, if the 0.3 mg/kg dose of rocuronium is selected for endotracheal intubation, other combinations of larger doses of propofol and/or opioids or inhaled induction using high concentrations of sevoflurane, rather than i.v. atropine, might be clinically helpful to facilitate intubation conditions. Among opioids, fentanyl has a rapid onset of 1 min, which does not delay the induction time, and has a duration of 20–30 min, which can be ideal for short surgeries¹². Although remifentanil also has a fast onset and an even shorter duration of action, we chose fentanyl because it is less expensive and can be used as a bolus dose instead of an infusion. There are several limitations to this study. One of them is the lack of cardiac output measurement. The hemodynamic effects of atropine may differ depending on the induction agents used as well as the chosen dose of atropine. Thus, further studies to elucidate the ideal dose of atropine along with quantitative measurements of the onset of neuromuscular block might be needed in children. Another limitation of this study is that neuromuscular function was not monitored in this study, we could not demonstrate the effect of atropine on the onset of rocuronium action. However, complete paralysis of the adductor pollicis muscle, the most frequent site at which neuromuscular blockade is measured, has been reported to be a poor indicator of intubation time.⁵ In conclusion, the time of intubation of a low dose of rocuronium (0.3 mg/kg) that is required for excellent tracheal intubation was 199 s during i.v. anesthesia induction using propofol and fentanyl in children. Although i.v. atropine (10 mcg/kg) before anesthesia induction reduced TimeEI95 by 28s, further evaluation is required to elucidate whether atropine could facilitate the onset of rocuronium in children.

CONCLUSION

Low dose rocuronium provides advantages over routine dose of rocuronium especially in pediatric age group. Premedication with i.v. atropine (10 mcg/kg) before anesthesia induction reduced mean time for intubation by 28s also while achieving satisfactory intubation conditions.

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