Inhalation induction with sevoflurane in children: comparison of 3 different volumes of gas flow

Completed

Conditions: Medical and Surgical, posted for elective surgical procedures ( weight 10-20 kg)under general anaestehsia,

Registration Number: CTRI/2016/12/007608

Lead Sponsor: Chacha Nehru Bal Chikitsalya

Brief Summary: The technique commonly used for painless rapid inhalationalinduction of anaesthesia in children involves delivery of sevoflurane at themaximum vaporizer dial setting (8%) and at high fresh gas flow rate (4-8 L/min)via a rebreathing system. The rationale for using the highest dial setting ofsevoflurane is to achieve sufficient alveolar concentration for unconsciousnessas early as possible. However, the rate of fresh gas flow (FGF) is chosenarbitrarily. There is no recommendation for what FGF should be used duringinduction in children. A high FGF reduces the time required to achieve thedesired sevoflurane concentration in the circuit-patient system. But it maylead to wastage of anaesthetic gases making it un-economical and leading toenvironmental pollution. On the other hand, if the FGF is too low, the timetaken to achieve desired inhalational agent concentration in the system wouldbe too long, thus reducing OT turnover and increasing the stress of inductionon the child. Required FGF also varies with the physical size of the patient. Therate of delivery of an anaesthetic agent to the lungs depends on the minutealveolar ventilation. Thus if we can tailor the FGF during induction to thepatientâ€™s minute ventilation (MV), we can achieve a desired balance betweenrapid induction with minimal wastage. **This study has been designed to ascertainthe MV based FGF that offers the best balance between rapid induction andminimal wastage in pediatric patients( hypothesis).**

After informed parental consent, 30 children, between 1 yrand 10 yrs of age, scheduled to undergo superficial procedures under generalanaesthesia with LMA will be randomly divided into 3 groups (Groups 0.5MV, MVand standard FGF).All the children will undergo pre-anaesthetic evaluation. Standardfasting guidelines will be followed before taking the patient to OT. All caseswill be performed on a single anaesthesia machine (Drager Primus) foruniformity of measurements. Paediatric closed circuit and 1L reservoir bag willbe used for each case.

Prior to induction, the circuit will be flushed of anyresidual anaesthetic gases and then primed with the patient end occluded, theAPL valve set at 10 cm H2O, sevoflurane vaporizer at 8% and FGF (100% O2) at6L/min for 30 seconds7. Anaesthesia induction will then be started via facemaskwith sevoflurane at 8% dial setting in 100% O2 at FGF determined by MV. Baselineweight based MV for each patient will be determined from Radfordâ€™s nomogram.Patients in Group MV will receive FGF equal to MV. Similarly, Group 0.5MV andMV will receive FGF equal to half MV and one time MV respectively.

Starting time (T0) will be taken as the time of applicationof the facemask on the childâ€™s face. Once the child is calm, ECG leads,pulse-oximeter and NIBP cuff will be attached. After the loss of eyelash reflex(time = T1), sevoflurane vaporizer dial setting will be reduced to 5%attempting to maintain spontaneous ventilation. Inspired and end tidalsevoflurane concentration, MAC, fraction of inspired oxygen (FiO2) and endtidal carbon dioxide (EtCO2) concentration will be measured with a multi gas analyser.Patients were observed for adequate depth of anaesthesia for IV cannulation andLMA placement (regular respiration,loss of muscle tone, jaw relaxation,trapezius squeeze test). Once these conditions are achieved, IV access will besecured, followed by insertion of an appropriately sized Laryngeal Mask Airway(time = T2). Patients will be observed for any reflex movement or tachycardia(HR rise by > 20% from prior to LMA insertion) during LMA insertion.Propofol boluses of 1ml/kg will be administered in case of inadequate depth atthe time of LMA insertion.

The total amount of sevoflurane consumed during inductionwill be recorded from the â€œlogbookâ€ function of the anaesthesia machine. T1,T2, T3, total sevoflurane consumption during induction and incidence ofmovement or tachycardia at the time of LMA insertion will be compared among the3 groups.The cost for the period of the different flow rate settings at T1, T2and T3 was calculated according to theformula (cost (Indian national rupees [INR]) = P\*F\*T\*M\*C/2.412\*d), where P wasvaporizer setting (%), F was fresh gas flow (2 l/min), T was the duration ofsevoflurane administration (min), M is the molecular weight of sevoflurane(200), C is the cost (rupees per ml) of sevoflurane, and d is the density ofsevoflurane (1.52 g/ml).

Detailed Description: Not available

Recruitment & Eligibility

Status: Completed

Sex: All

Target Recruitment: 45

Inclusion Criteria

After informed parental consent, 30 children, between 1 yr and 10 yrs of age, weighing between 10-20 kg and scheduled to undergo superficial procedures under general anesthesia will be included in the study.
They will be randomly divided into 3 groups (Groups 0.5 MV, MV and fixed flow technique).

Exclusion Criteria

infants and children more than 10 years, ASA status 3 or more, weight less than 10 or more than 20 kg, history of Upper respiratory tract infection in previous 2 weeks and full stomach.

Study & Design

Study Type: Interventional

Study Design: Not specified

Primary Outcome Measures

Name	Time	Method
cost of sevoflurane consumed	at the time of insertion of LMA

Secondary Outcome Measures

Name	Time	Method
time( T1, T2 and T3)	loss of eyelash reflex(T1), IV line placement(T2), LMA insertion(T3)
total sevoflurane consumed	time of LMA insertion(T3)

Trial Locations

Locations (1): Chacha Nehru Bal Chikitsalya
🇮🇳
East, DELHI, India
Chacha Nehru Bal Chikitsalya
🇮🇳East, DELHI, India
Dr Anju Gupta
Principal investigator
9643308220
dranjugupta2009@rediffmail.com