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Respiratory mechanics and intrinsic PEEP during ketamine and halothane anesthesia in young children
D L Shulman1, E Bar-Yishay, S Godfrey
1Department of Anesthesia, Hadassah University Hospital, Mount Scopus, Jerusalem, Israel.
Insights
Ketamine anesthesia significantly increases respiratory system compliance (Crs) in children compared to halothane. This leads to a longer expiratory time constant (tau) and higher intrinsic positive end-expiratory pressure (PEEPi).
Area of Science:
- Pediatric Anesthesiology
- Respiratory Physiology
Background:
- Anesthetic agents can affect respiratory mechanics in children.
- Understanding the impact of ketamine versus halothane on respiratory system compliance (Crs) is crucial for safe pediatric anesthesia.
Purpose of the Study:
- To compare the effects of ketamine and halothane anesthesia on static respiratory system compliance (Crs) in children.
- To investigate the influence of these anesthetics on intrinsic positive end-expiratory pressure (PEEPi) and expiratory time constant (tau).
Main Methods:
- Static compliance (Crs) was measured using the interrupter technique in 18 anesthetized children.
- The pressure-volume (P-V) curve was analyzed to determine Crs and PEEPi.
- Expiratory time (Te) and passive expiratory time constant (tau) were measured.
Main Results:
- Crs was significantly higher in the ketamine group (22.8 ml/cm H2O) compared to the halothane group (15.7 ml/cm H2O).
- The expiratory time constant (tau) was significantly prolonged in the ketamine group.
- Mean PEEPi was higher in the ketamine group (2.3 cm H2O) versus the halothane group (0.4 cm H2O).
Conclusions:
- Ketamine anesthesia results in significantly greater Crs in children than halothane anesthesia.
- Ketamine's effects on tau and Te/tau contribute to increased PEEPi during pediatric anesthesia.
Abstract:
Static compliance of the respiratory system (Crs) was measured by the interrupter technique in 18 anesthetized children to compare the effects of ketamine on Crs with those of halothane. Crs was the slope of the pressure-volume (P-V) curve obtained by repeated brief airway occlusions throughout relaxed expiration, and the intercept of the P-V curve on the pressure axis was the intrinsic positive end-expiratory airway pressure (PEEPi). Expiratory time (Te) was measured during a period of quiet breathing, and the passive expiratory time constant (tau) was measured during the relaxed expiration after an end-inspiratory occlusion. Nine children were anesthetized with a continuous infusion of ketamine and a matching group of nine children inhaled halothane in oxygen. Crs was significantly greater in the ketamine group (22.8 +/- 6.2 ml/cm H2O) than in the halothane group (15.7 +/- 5.5 ml/cm H2O). The tau value was also significantly greater in the ketamine group. Mean PEEPi in the ketamine group was 2.3 +/- 1.8 cm H2O and in the halothane group was 0.4 +/- 0.8 cm H2O. PEEPi correlated inversely with Te/tau according to a logarithmic function. It was concluded that, in children anesthetized with ketamine, Crs is significantly greater than that in children anesthetized with halothane, and the resultant prolongation of tau and decreased Te/tau with ketamine anesthesia lead to increased PEEPi.