The efficacy of a subhypnotic dose of propofol in preventing laryngospasm following tonsillectomy and adenoidectomy in children.

BACKGROUND: Laryngospasm is a well-known problem typically occurring immediately following tracheal extubation. Propofol is known to inhibit airway reflexes. In this study, we sought to assess whether the empiric use of a subhypnotic dose of propofol prior to emergence will decrease the occurrence of laryngospasm following extubation in children. METHODS: After approval from the Institutional Ethics Committee and informed parental consent, we enrolled 120 children ASA physical status I and II, aged 3-14 years who were scheduled to undergo elective tonsillectomy with or without adenoidectomy under standard general anesthesia. Before extubation, the patients were randomized and received in a blinded fashion either propofol 0.5 mg.kg(-1) or saline (control) intravenously. Tracheal extubation was performed 60 s after administration of study drug, when the child was breathing regularly and reacting to the tracheal tube. RESULTS: Laryngospasm was seen in 20% (n = 12) of the 60 children in the control group and in only 6.6% (n = 4) of 60 children in the propofol group (P < 0.05). CONCLUSIONS: During emergence from inhalational anesthesia, propofol in a subhypnotic dose (0.5 mg.kg(-1)) decreases the likelihood of laryngospasm upon tracheal extubation in children undergoing tonsillectomy with or without adenoidectomy.

The relationship between end tidal carbon dioxide and arterial carbon dioxide during controlled hypotensive anaesthesia.

OBJECTIVES: To prospectively assess the magnitude of changes in the arterial-to-end tidal carbon dioxide gradient [P(a-ET)CO2] as well as in the ratio of physiological dead space to tidal volume (Vdphys/Vt) during controlled hypotensive anaesthesia, and to evaluate whether or not ventilatory requirements remain unaltered during this procedure. SUBJECTS AND METHODS: Twelve adult patients with American Society of Anesthesiologists' physical status I and II undergoing middle ear surgery were selected. A standard anaesthetic procedure was followed for all cases, using thiopental sodium, succinylcholine, fentanyl, atracurium and 60% N2O in 40% oxygen supplemented with isoflurane. Mean arterial blood pressure (MAP) was reduced to 60 +/- 5 mm Hg in all patients using a sodium nitroprusside infusion. The end tidal (ET) CO2, PaCO2, MAP, peak airway pressure, plateau pressure and expiratory minute volume were recorded during a period of normal arterial blood pressure (time 1) and during hypotension (time 2). RESULTS: A significant decrease in PaCO2 (7%) and ETCO2 (17%) from time 1 to time 2 (p < 0.01) was noted, as was a significant increase in P(a-ET)CO2 (48%) and in the Vdphys/Vt ratio (41.17%) (p < 0.01) during the same period. CONCLUSION: The decrease in ETCO2 does not reflect the changes in PaCO2. The larger decrease in ETCO2 is mainly due to the increase in the Vdphys/Vt ratio. During anaesthesia, once normocapnia is achieved with normal arterial blood pressure, there is hardly any need to change the ventilation after initiation of controlled hypotension.