Effects of midazolam on ventilatory response to carbon dioxide when used as sedative during epidural blockade / 中华麻醉学杂志

ABSTRACT

Objective To investigate the effect of midazolam on ventilatory response to carbon dioxide (CO 2) when it is used as sedative supplement to epidural blockade(EB) Methods Fifteen ASA Ⅰ Ⅱ patients [age (49?7) years , weight (56?13)kg] undergoing upper abdominal surgery were studied Patients with respiratory disease were excluded No patient was addicted to smoking,alcohol,received any sedatives or hypotics within one month before surgery The patients were premedicated with intramuscular phenobarbital 0 1g and atropine 0 5mg Epidural catheter was inserted in a cephala direction for 4 cm into epidural space via the tuohy needle at T 9 10 1% lidocaine and 0 2% pontocaine solution was used for epidural block The level of block was T 3 5 When the level of block was fixed, midazolam 0 1 mg/kg was given intravenously Respiratory rate(RR), tidal volume (V T), end tidal concentration of CO 2 (P ET CO 2) and pulse oxygen saturation (SpO 2) were measured before anesthesia (baseline values), before midazolam when the level of block was fixed and 5 min after midazolam Measurement of ventilatory response to CO 2 the patient was asked to breathe with a closed system without a CO 2 absorber P ET CO 2 increased to 55 mm Hg in 6 10 min RR,V T and minute ventilation (MV) were measured at P ET CO 2 40, 45, 50, and 55 mm Hg The patient then breathed fresh air and P ET CO 2 returned to normal 5 min after midazolam the measurment was repeated The CO 2 ventilatory response curve was obtained by plotting MV against the corresponding P ET CO 2 Results P ET CO 2, RR and SpO 2 did not change significantly after epidural block and midazolam There was no significant change in V T after epidural block as compared with the baseline value but V T decreased significantly after midazolam(P