A comparative study of efficacy of different doses of fentanyl in the prevention of incision related tachycardia in children

 

J V Subba Rao¹, Khaja Ali Hassan^2*, G R Prasad³, Umer Majid⁴, Santosh Singh⁵

 

{¹Professor, ²Associate Professor, ⁴Assistant Professor, ⁵PG, Department of Anesthesiology} {³Paediatric Surgeon, Department of Paediatric}

Deccan College of Medical Sciences, Hyderabad, Telangana, INDIA.

Email: propofol123@gmail.com

 

Abstract               Background: Pain is a subjective sensation and assessment of pain during general anaesthesia is a difficult preposition. It can only be assessed indirectly by noting the features of a stress response like tachycardia and hypertension after a surgical stimulus. Skin is a very painful structure and skin incision is invariably associated with tachycardia. Objectives: We tried to determine the optimal dose of fentanyl that can provide adequate analgesia in paediatric patient. We have studied efficacy of two doses of Fentanyl, 1 and 2 mcg/Kg body weight on prevention of incision related tachycardia in children undergoing lower abdominal surgeries. Materials and Methods: Children of age group 1-5 years were randomly allocated into two groups, Group A and B. children in Group A received 1 mcg/kg of Fentanyl and those in Group B received 2 mcg/kg of Fentanyl. After induction with thiopentone sodium, all the children were given inhalational anesthesia with nitrous oxide, oxygen and halothane mixture. Heart rate was noted at different periods during surgery. Results: In both groups heart rate increased immediately after incision and the increase in heart rate was less in group B compared to group A. But this was not significant statistically. The rise in heart rate could be suppressed only partially by Fentanyl, 2 mics/Kg of body weight. Incision related tachycardia could not be suppressed entirely by either of the two doses. Conclusions: We conclude that incision related tachycardia cannot be suppressed altogether by either 1 mcg or 2 mcg/Kg dose. For adequate analgesia it is better to give 2 mcg Fentanyl per Kg body weight in children.

Key Words: Heart rate, Fentanyl, Lower abdominal surgeries incision related tachycardia.

 

 

 

INTRODUCTION

The utmost responsibility of the Anesthesiologist is to provide adequate pain relief during surgery. Unfortunately, we do not have adequate yardstick to assess pain. Hence we have to monitor other indirect variables like heart rate and blood pressure as markers of pain. Pain produces a sympatho adrenal response secondary to hypothalamic activation of the sympathetic autonomic system and release of norepinephrine. This increased sympathetic activity results in tachycardia and hypertension¹. Skin incision in children results in a stress response and produces increase in heart rate and blood pressure². This stress response can be modified by administration of narcotics³. Tachycardia in children immediately before surgery maybe because of anxiety and stress in children. But increase in heart rate immediately after incision can be taken as an indicator of pain. We have studied whether Fentanyl as a supplementary analgesic during gas oxygen inhalational anesthesia can suppress this tachycardia, Fentanyl is a short acting opioid and high doses of Fentanyl will be used during cardiac anesthesia and for induction. But as a supplementary analgesic during inhalational anesthesia it is given at a dose of 1-3 mcg/kg ⁴ We compared two doses of Fentanyl 1 mcg/kg and 2 mcg/kg on suppression of incision related tachycardia in pediatric patients. Our primary aim during this study was to know whether we are providing adequate analgesia to the child during nitrous oxide, oxygen, halothane anesthesia. We have taken incision related tachycardia as a yardstick of pain and we studied whether Fentanyl can suppress this tachycardia at the selected doses.

 

MATERIALS AND METHODS

Forty children of the age group 1 – 5 years undergoing nitrous oxide, oxygen, halothane anesthesia for routine lower abdominal surgeries were randomly allocated into two groups. We used a computer generated random table for this. All the even numbers in the table were included in Group – A. Those with odd numbers were included in Group – B. Children other than ASA grade l are excluded from the study. Children undergoing long surgeries(>45 minutes) were also excluded from the study. Group – A patients received 1 mcg/kg body weight of Fentanyl and Group – B patients received 2 mcg/kg body weight of Fentanyl intravenously at the time of premedication. A routine pre anesthetic checkup was done before taking the child inside. Their NBM status was checked. Most of the children come to the operation theater with an IV line inserted in the pediatric ward. We simply check the patency of IV line by flushing with normal saline and give premedication glycopyrrolate 6 mcg/kg body weight IV. We observed that giving glycopyrolate well in advance makes the Airway dry by the time of intubation and there will be decreased need for endotracheal suction. Then the child is shifted inside and the calculated dose of Fentanyl is given. Ondansetron 80 mcg/kg body weight was also given intravenously. Preoxygenation and induction are done simultaneously because it is difficult to restrain the child on operation table for a long period. Patient is induced with 5mg/kg of thiopentone and 2 mg/kg of suxamethonium. After this patient is connected to pulse oximeter. Immediately after the child is induced we started mask ventilation with oxygen. Child is intubated after one minute and connected to Boyle’s machine via Jackson Ree’s circuit and IPPV started with N₂O + O₂ + halothane. For relaxation Injection vecuronium 80mcg/kg intravenous was given after recovery from suxamethonium in all patients. We recorded pulse rate immediately after induction. For this we took the reading of heart rate on the pulse oximeter. We took this as base line value because before induction it would be difficult to connect the pulse oximeter probe to a struggling child. Hence we took the value after induction as base line value. Then we recorded the pulse rate at 1 minute and 3 minutes after intubation. The surgeon is allowed to start the surgery usually 5 minutes after intubation. We recorded pulse rate just before incision and again at 1 minute and 3 minutes after incision. During surgery we also recorded highest heart rate and lowest heart rate throughout the procedure. We recorded the pulse rate after surgery but before recovery. This we did, to have comparative values at different times during the surgical procedure. At the end of surgery after respiratory efforts started, usually after 30 minutes child was given 50 mcg/kg body weight of neostigmine and 10 mcg/kg body weight of glycopyrolate. Once respiratory efforts were adequate and the child is awake, the patient was extubated. 1 minute after reversal and extubation, child was assessed by Steward Recovery Score⁵. This was to check whether we were compromising on recovery by increasing dose of Fentanyl. After satisfactory recovery children were shifted to postoperative ward and monitored periodically till complete recovery. We also looked for side effects of Fentanyl in each case. we looked for nausea, vomiting, chest wall rigidity or post operative respiratory depression.

 RESULTS                                          

1 minute after intubation tachycardia was less in Group – B compared to Group-A. In Group – A increase in heart rate varied from 6 to 29 with a mean of 13.5 whereas increase in heart rate one minute after intubation in group – B varied from 4 to 31 with a mean of 6.7. But this was not significant statistically (p>0.05) Three minutes after intubation the heart rates started settling down and returned to almost base line values in both groups. When the heart rates in both groups were compared there was no statistically significant difference. There was increase in heart rate one minute after skin incision in both the groups. Increase in heart rate in Group – A varied from 6 to 19 with a mean of 10.6 in Group – B increase in heart rate varied from 2-11 with a mean of 5.6. Again this was not significant statistically. Three minutes after incision tachycardia was still there in both groups but comparatively less. When heart rates in both groups were compared it was observed that the increase in heart rate was more in group B. This was clinically irrelevant in relation to our study but statistically significant. Steward Recovery Score was 5 – 6 in both the groups. The maximum possible score is 6. That means we did not compromise on recovery by increasing Fentanyl dose from 1 mcg/kg to 2 mcg/kg body weight. One patient in Group – B had a recovery score of 3 but improved to 5 after 5minutes. None of the patients in either group, had nausea, vomiting and chest wall rigidity. No respiratory depression was observed in any of the patient in the post operative ward.

Statistical Analysis

Both the groups were similar in characteristics like age, ASA grade and site of surgery. The difference of age between both the groups was statistically not significant. But the mean duration of surgery in group B was more, and this difference was found to be statistically significant. But this is not relevant to our study.

RESULTS

Table 1: Demographic table

                           

Table 2:

 

Table 3: Comparison of effect of different doses of fentanyl on heart rate