Effects of midline laparotomy on cough strength: a prospective study measuring cough pressure.

BACKGROUND: Laparotomy is assumed to decrease cough strength due to three factors: abdominal muscle trauma, postoperative pain, and diaphragmatic dysfunction. However, the effect of trauma from laparotomy itself on strength (net of the other two factors) has not been measured to our knowledge. The aim of this study was to measure the effect of laparotomy on cough strength after first measuring the effect of epidural analgesia.

METHODS: In 11 patients scheduled for open midline laparotomy, cough pressure (PCOUGH), a proxy for strength, was measured with a rectal balloon at three moments: before the procedure, at baseline; before surgery, under epidural bupivacaine to T6; and postoperatively, under epidural bupivacaine to the same analgesic level (T6). Continuous variables were compared using the Wilcoxon signed-rank test. The repeatability of PCOUGH measurements was confirmed with the intraclass correlation coefficient (ICC). Pain on coughing, hand grip strength, and the Ramsay and modified Bromage scores were also recorded.

RESULTS: Median (interquartile range) PCOUGH decreased from a baseline of 103 (89-137) to 71 (56-116) cmH<inf>2</inf>O under presurgical epidural bupivacaine (P=0.003). Postoperative PCOUGH remained unchanged at 76 (46-85) cmH<inf>2</inf>O under epidural analgesia (P=0.131). The ICCs indicated excellent repeatability of the PCOUGH measurements (P<0.001). Pain on coughing was 0 to 1 in all subjects. Hand grip strength and the Ramsay and Bromage scores were unchanged.

CONCLUSIONS: Although thoracic epidural bupivacaine reduces cough strength as measured by PCOUGH, midline laparotomy does not further reduce strength in the presence of adequate epidural analgesia.