Abstract
BackgroundDiaphragm paresis is common after cardiac surgery and may delay the weaning from the ventilator. Our objective was to evaluate diaphragm thickening during weaning and secondly the muscle thickness as a marker of myotrauma.MethodsPatients undergoing elective cardiac surgery were prospectively included. Ultrasonic index of right hemidiaphragm thickening fraction (TF) was measured as a surrogate criterion of work of breathing. A TF < 20% was defined as a low diaphragm thickening. Measurements of TF were performed during three periods to study diaphragm thickening evolution defined by the difference between two consecutive time line point: preoperative (D − 1), during a spontaneous breathing trial (SBT) in the intensive care unit and postoperative (D + 1). We studied three patterns of diaphragm thickness at end expiration evolution from D − 1 to D + 1: > 10% decrease, stability and > 10% increase. Demographical data, length of surgery, type of surgery, ICU length of stay (LOS) and extubation failure were collected.ResultsOf the 100 consecutively included patients, 75 patients had a low diaphragm thickening during SBT. Compared to TF values at D − 1 (36% ± 18), TF was reduced during SBT (17% ± 14) and D + 1 (12% ± 11) (P < 0.0001). Thickness and TF did not change according to the type of surgery or cooling method. TF at SBT was correlated to the length of surgery (both r = − 0.4; P < 0.0001). Diaphragm thickness as continuous variable did not change over time. Twenty-eight patients (42%) had a > 10% decrease thickness, 19 patients (29%) stability and 19 patients (28%) in > 10% increase, and this thickness evolution pattern was associated with: a longer LOS 3 days [2–5] versus 2 days [2–4] and 2 days [2], respectively (ANOVA P = 0.046), and diaphragm thickening evolution (ANOVA P = 0.02). Two patients experience extubation failure.ConclusionThese findings indicate that diaphragm thickening is frequently decreased after elective cardiac surgery without impact on respiratory outcome, whereas an altered thickness pattern was associated with a longer length of stay in the ICU. Contractile activity influenced thickness evolution.Trial registry number ClinicalTrial.gov ID NCT02208479
Highlights
Diaphragm paresis is common after cardiac surgery and may delay the weaning from the ventilator
All patients had elective cardiac surgery with cardiopulmonary bypass (CPB) and none had a history of neuromuscular disease
The findings of this study indicate that (1) diaphragm thickening can be markedly reduced in the postoperative cardiac surgery with an incidence of 75% of patients assessed with a thickening fraction (TF) below 20%; (2) the time course of diaphragm thickening was associated with diaphragm thickness changes
Summary
Diaphragm paresis is common after cardiac surgery and may delay the weaning from the ventilator. Diaphragm paresis observed in cardiac surgery may share the same pathways involved in ventilatorinduced diaphragmatic dysfunction [7, 8] It is caused by diaphragm disuse during mechanical ventilation or in sepsis as described in ICU settings [9]. In times of personalized physiological medicine, diaphragm myotrauma is an interesting model of the crosstalk between treatment monitoring and organ dysfunction [13]. This highlights the need for a direct measurement of diaphragm effort at the early phase after surgical injury [10]
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