The ideal time for intravenous cannulation following inhalational induction with sevoflurane in children is debatable. Loss of eyelash reflex or centralization of eyeballs has been recommended to assess adequate depth for painless cannulation but occasional patient may still respond to pain. Trapezius Squeeze Test (TST) elicits toe/body movement if the patient feels pain while being induced with sevoflurane. We tested the hypothesis that the loss of response to TST under sevoflurane anesthesia would give an accurate optimal time for pain-free intravenous cannulation.
37 patients between the age ranges of 1 to 8 years of either gender weighing 8-20 kg undergoing minor day care surgery were included in the study. Patients were randomly assigned to Group I (eyeball centralization), Group II (loss of eye lash reflex + 3.5 min), and Group III (Unresponsive to TST). All children were induced with a gradually increasing concentration of sevoflurane. After one minute of induction, the study indicators (eyeballs centralizing effect, loss of eye lash reflex + 3.5 min or negative response to TST) were checked every 15 s till the end point of the indicator had been reached. A person not associated with the study performed intravenous cannulation and noted movement, if any.
None of the TST group patients (Group III) showed any motor response to cannulation (0%). In contrast, 7.1% and 16.7% of Group I and II patients demonstrated some motor response respectively. Grade-3 response to the cannulation in the form of movement of the limb or head and neck accompanied with coughing and/or laryngospasm was not observed in any patient.