[Analysis of induction with 5% isoflurane and 60% nitrous oxide in premedicated adults].
OBJECTIVE
To analyze rapid inhalatory anesthetic induction in premedicated adults (fentanyl, droperidol, diazepam and atropine) with an inspired mixture of O2, N2O (60%) and 5% isoflurane as a means for accelerating induction time and reducing complications.


METHODS
We studied a series of 35 adult ASA-I patients at four times: baseline (1), premedication (2), induction (3) and postintubation (4). Measurements taken were arterial hemoglobin oxygen saturation (SpO2), arterial pressure (AP), heart rate (HR), end-tidal CO2 pressure (PETCO2) and respiratory frequency. We also recorded maximum end-tidal isoflurane pressure (FEtiso) at time 3; presence of apnea, cough and mask rejection at time 3; arrhythmia at times 3 and 4, and induction recall at time 3. Mean time of induction (time from start of induction to laryngoscopy) and the double product (HR x systolic AP) were calculated.


RESULTS
Coughing was observed in 20% (7/35) and was significantly associated with smoking; mask rejection was observed in 5.71% (2/35). The lowest SpO2 measurements occurred during period 2 and the highest during 3 (98.2 +/- 0.76). The incidence of apnea (77.14%, 27/35) was high during period 3, with mean PETCO2 values (+/- SD) of 40.71 +/- 4.19 mmHg and mean maximal FEtiso values of 1.6 +/- 0.53%. Mean time of induction was 96.28 +/- 5.19 s. There were no cases of recalled induction of arrhythmia in periods 3 and 4. The highest levels of AP and HR were recorded during period 4. The only difference in AP and HR between periods 2 and 3 was in diastolic AP, which was higher (p < 0.05) in period 3.


CONCLUSIONS
Rapid induction with 5% isoflurane is achieved within 1.5 min, with a 20% incidence of coughing and a 5% incidence of mask refusal. The high frequency of apnea (77%) is caused by the rapid elevation of alveolar isoflurane, which has an impact on the apneic threshold. Anesthetic induction with 5% isoflurane and 60% nitrous oxide in premedicated adults is accomplished with good maintenance of hemodynamic stability. However, tachycardia and arterial hypertension appear after laryngoscopy and tracheal intubation.
Servicio de Anestesiología, Clínica La Milagrosa, Madrid.
R
R
Martín-Larrauri
D000293:Adolescent; D000328:Adult; D000769:Anesthesia, Inhalation; D001145:Arrhythmias, Cardiac / Q000139:chemically induced / Q000517:prevention & control; D001285:Atropine; D003975:Diazepam; D004329:Droperidol; D005260:Female; D005283:Fentanyl; D006801:Humans; D007530:Isoflurane / Q000008:administration & dosage* / Q000009:adverse effects; D008297:Male; D008875:Middle Aged; D009609:Nitrous Oxide / Q000008:administration & dosage* / Q000009:adverse effects; D010342:Patient Acceptance of Health Care; D011229:Preanesthetic Medication; D012120:Respiration Disorders / Q000139:chemically induced / Q000517:prevention & control
D001285:Atropine; D007530:Isoflurane; D009609:Nitrous Oxide; D004329:Droperidol; D003975:Diazepam; D005283:Fentanyl
Análisis de la inducción con isoflurano al 5% y óxido nitroso al 60% en adultos premedicados.