Am. J. Respir. Crit. Care Med.,
Volume 161, Number 4, April 2000, 1372-1375
Contribution of Pain to Inspiratory Muscle
Dysfunction after Upper Abdominal Surgery
A Randomized Controlled Trial
THEODOROS
VASSILAKOPOULOS,
ZAFIRIA
MASTORA,
PARASKEVI
KATSAOUNOU,
GEORGE
DOUKAS,
SERAFIM
KLIMOPOULOS,
CHARIS
ROUSSOS,
and
SPYROS
ZAKYNTHINOS
Department of Critical Care and Pulmonary Services, University of Athens Medical School, Evangelismos Hospital; Department of Surgery,
University of Athens School of Nursing, Evgenidio Hospital; and Department of Surgery, Evangelismos Hospital, Athens, Greece
Upper abdominal surgery causes respiratory muscle dysfunction.
Multiple factors have been implicated in the occurrence of such
dysfunction; however, the role of pain remains unclear. To elucidate the role of pain, we studied 50 patients undergoing elective
upper abdominal surgery in a randomized, controlled investigation. Inspiratory and expiratory muscle function were assessed
through sniff mouth pressure (Psniff) and maximal expiratory
pressure (MEP), respectively. Pain during the pressure maneuvers
was assessed with a visual analog scale (VAS). Measurements were
made before surgery (Session 1), 24 h after surgery (Session 2),
and 1 h later, after intramuscular administration of pethidine (analgesia group) or placebo (placebo group) (Session 3). To evaluate
the effect of pain, we used a mixed-effects model with random intercept, having either Psniff or MEP as the dependent variable and
both surgical operation and the level of pain as fixed effects. Upper abdominal surgery decreased Psniff in both the analgesia and
placebo groups (from 70 ± 15 to 42 ± 11 cm H2O [p < 0.05] in the
analgesia group, and from 69 ± 15 to 42 ± 10 cm H2O [p < 0.05]
in the placebo group). Intramuscular pethidine caused an increase
in Psniff to 56 ± 14 cm H2O (p < 0.05), whereas placebo had no
effect. Pain increased comparably after upper abdominal surgery
in both groups (from 0.3 ± 0.6 to 4.4 ± 1.5) [p < 0.05] in the analgesia group and from 0.4 ± 0.5 to 4.3 ± 1.5 [p < 0.05] in the placebo group). Intramuscular pethidine decreased pain as measured
by VAS score to 2.1 ± 1.0 (p < 0.05) in the analgesia group,
whereas placebo had no effect. Psniff had a statistically significant
relationship to pain (p < 0.001). Adjusting for the occurrence of
surgical operation did not affect this result. MEP showed the same
tendency as Psniff, but the observed changes did not reach statistical significance. We conclude that pain contributes to inspiratory muscle dysfunction after upper abdominal surgery.
