ABSTRACT
OBJECTIVE: To retrospectively analyze the effects of different ventilation modes on pulmonary function during minor operation of general anesthesia with streamlined liner of the pharynx airway (SLIPA) laryngeal mask and assess its safety of spontaneous respiration during general anesthesia. METHODS: A total of 76 adult patients (aged 28 - 44 years old, American Society of Anesthesiologists physical status I-II) scheduled for operations were randomly allocated into the mechanical ventilation and spontaneous respiration group (n = 38 each). Anesthetic induction was performed intravenously with propofol (2 mg/kg), sulfentanyl (0.5 µg/kg) and cisatracurium besylate (0.3 mg/kg) (in mechanical ventilation group). Anesthesia was maintained by sevoflurane at 0.7 minimum alveolar concentration (MAC), mixture of atmosphere and oxygen at 1:1 and a continuous infusion of propofol at the speed of 4 mg×kg(-1)h(-1). Neostigmine (2 mg) and atropine (1 mg) were administered intravenously before the extraction of SLIPA laryngeal mask in order to antagonize the residual effects of muscle relaxation. The parameters including heart rate (HR), mean blood pressure (MAP) and end-tidal pressure of CO(2) (P(ET)CO(2)), blood gas analysis and the alveolar-arterial oxygen gradient [P(A-a)DO(2)], respiratory index (RI) and dead volume/tidal volume (V(D)/V(T)) were calculated at Different time points. RESULTS: No significant differences were found in HR (spontaneous respiration group: 76 ± 7, 78 ± 6, 79 ± 7/min; mechanical ventilation group: 77 ± 6, 80 ± 5, 79 ± 6/min), MAP (spontaneous respiration group: 91 ± 10, 89 ± 9, 90 ± 9mm Hg; mechanical ventilation group: 89 ± 10, 88 ± 9, 92 ± 8) mm Hg at the monitored time points between two groups (P > 0.05). At the time of 30 min and 60 min after insertion, the pH value was significantly lower in spontaneous respiration group (7.351 ± 0.028, 7.338 ± 0.025) than those in mechanical ventilation group (7.391 ± 0.031, 7.389 ± 0.032). The values of PaCO(2) (42 ± 4, 46 ± 6) mm Hg and P(ET)CO(2) (41 ± 5, 45 ± 3) mm Hg were higher than those in mechanical ventilation group (37 ± 3, 35 ± 5; 37 ± 4, 36 ± 4) mm Hg (P < 0.05). No significant difference was found in the P(A-a)DO(2), RI or V(D)/V(T) at the monitored time points between two groups (P > 0.05). CONCLUSION: Neither mechanical ventilation mode nor spontaneous respiration ventilation mode has any effect upon pulmonary function by during minor operation of general anesthesia with SLIPA laryngeal mask. Spontaneous respiration can offer a sufficient supply of oxygen but it carries the risk of CO(2) accumulation.
