Decrease in functional residual capacity and ventilation homogeneity after neuromuscular blockade in anesthetized preschool children in the lateral position.
BACKGROUND
While functional residual capacity (FRC) is reduced in children undergoing general anesthesia, the lateral position leads to an increase in FRC compared with the supine position. The impact of neuromuscular blockade remains unknown. We tested the hypothesis that neuromuscular blockade leads to a decrease in FRC and increase in lung clearance index (LCI) while the application of positive endexpiratory pressure (PEEP) of 6 cmH(2)O leads to a restoration in both parameters.


METHODS
After approval of the local Ethics Committee, we studied 18 preschool children (2-6 years) without cardiopulmonary disease, who were scheduled for elective surgery. Anesthesia was standardized using propofol and fentanyl. FRC and LCI were calculated by a blinded observer using a SF6 multibreath washout technique with an ultrasonic transit-time airflow meter (Exhalyzer D). Measurements were taken in the left lateral position (PEEP 3 cmH2O) after 1. intubation with a cuffed tracheal tube, 2. neuromuscular blockade with rocuronium, and 3. the additional application of PEEP (6 cmH2O).


RESULTS
Functional residual capacity mean (sd) decreased from 31.6 (4.4) ml.kg(-1) to 27.6 (4.2) ml.kg(-1) (P<0.001) following neuromuscular blockade while the LCI increased from 6.54 (0.6) to 7.0 (0.6) (P<or=0.001). After the application of PEEP (6 cmH2O), FRC increased to 32.4 (5.0) ml.kg(-1) whereas the LCI decreased to 6.58 (0.5) showing no significant changes from baseline measurements.


CONCLUSIONS
In the lateral position, neuromuscular blockade led to a significant decrease in FRC associated with a small increase in ventilation inhomogeneity. FRC and LCI were restored to baseline levels with the application of PEEP 3 cmH2O that is in addition to a background of PEEP 3 cmH2O giving a total of 6 cmH2O PEEP.
Division of Anesthesia, University Children's Hospital, Basel, Switzerland. bvonungern@uhbs.ch
Britta S
BS
von Ungern-Sternberg
Adrian
A
Regli
Franz J
FJ
Frei
Jürg
J
Hammer
Eva-Maria
EM
Jordi Ritz
Thomas O
TO
Erb
D000732:Androstanols; D000768:Anesthesia, General; D018686:Anesthetics, Intravenous; D002648:Child; D002675:Child, Preschool; D005260:Female; D005283:Fentanyl; D005652:Functional Residual Capacity / Q000187:drug effects*; D006801:Humans; D008297:Male; D019148:Neuromuscular Blockade; D003473:Neuromuscular Nondepolarizing Agents; D011175:Positive-Pressure Respiration; D011187:Posture / Q000502:physiology; D015742:Propofol; D015656:Respiratory Mechanics / Q000187:drug effects*; D000077123:Rocuronium; D018401:Sample Size
D000732:Androstanols; D018686:Anesthetics, Intravenous; D003473:Neuromuscular Nondepolarizing Agents; D005283:Fentanyl; D000077123:Rocuronium; D015742:Propofol