The Association Between Intestinal Perfusion and Prolonged Mechanical Ventilation in Patients After Cardiac Valve Surgery
Condition: Patient After Cardiac Valve Surgery; Patient With Prolonged Mechanical Ventilation
Study type: Observational

Summary: 
      Background This study aimed to confirm that alterations in Doppler parameters of superior
      mesenteric artery(SMA) blood flow caused by intestinal hypoperfusion are associated with
      prolonged mechanical ventilation(PMV) in patients after cardiac valve surgery.

      Methods The patients' basic hemodynamics parameters, and the SMA blood flow parameters
      monitored by Doppler ultrasound were collected in the supine position at admission. The
      length of mechanical ventilation continued to be monitored. The SMA Doppler parameters were
      measured again when the patient was extubated. PMV was defined as MV≥96 hours.
    

Detailed description: 
      Patient enrollment This prospective observational study was performed in the 15-bed adult
      critical care unit in Adult General Hospital from January 2021 to March 2022.

      The inclusion criteria were as follows: 1) patients admitted to ICU immediately after cardiac
      valve surgery; 2) age 18-80 years; 3) sinus rhythm; 4) without active bleeding or
      pneumothorax, and 5) complete measurement data.

      The exclusion criteria were as follows: 1) history of peripheral vascular disease, 2)
      patients with severe stenosis defined as SMA peak systolic velocity (SMA-PSV >275 cm/s or
      SMA-PSV/abdominal aorta peak velocity of >3, 3) hepatic dysfunction or liver cirrhosis,
      portal hypertension, 4) cancer or end-stage renal diseases, 5) poor quality of abdominal
      ultrasound images.

      Doppler ultrasound monitoring Doppler ultrasound was performed with an ultrasound system
      consisting of a 2-5 MHz C60xp Probe (X-Porte Ultrasound System, FUJIFILM SONOSITE, INC.,
      USA). Blood flow parameters were measured by two physicians, each physician measured twice
      and averaged, and then averaged the two results. Each of the two ICU physicians had more than
      four years of experience in critical ultrasound and obtained certification from the Chinese
      Critical Ultrasound Study Group. Two skilled physicians conducted a total of 40 measurements
      on ten patients after cardiac valve surgery to evaluate inter-observer reproducibility.

      The SMA flow was measured 1 cm proximal to the abdominal aorta. The angle of insonation was <
      60°. The time-velocity waveform readings were used to measure the peak systolic velocity
      (PSV), end-diastolic velocity(EDV), resistance index(RI), time-averaged mean velocity(TAMV),
      pulsatility index (PI), according to the calculation software carried by the ultrasound.
      PI=(PSV-EDV)/TAMV, and RI=(PSV-EDV)/PSV.

      Data collection Demographic information was recorded for further analyses (e.g., age, gender,
      EuroSCORE-II, sequential organ failure assessment (SOFA) score, body mass index (BMI), and
      hemodynamic parameters and blood gas analysis data). In addition, types of operation and
      operation time were collected. Moreover, outcome variables (e.g., hospital mortality, time of
      MV, length of ICU stay) were recorded for further comparison.

      Statistical analysis The median plus the interquartile range (IQR) or mean standard deviation
      is used to show demographic data. The Shapiro-Wilk test was used to evaluate normality. The
      differences between groups were compared using the student's t-test for continuous variables
      with normality distribution and the Mann-Whitney U test for those without normality
      distribution. The differences between groups for categorical variables were compared by
      performing a Chi-square test. Correlations between variables and PMV were assessed by
      conducting logistic regression analysis. Variables showing statistical significance in the
      univariate logistic regression were selected covered in the multivariate logistic regression.
      Furthermore, to evaluate the predictive ability of the variables for PMV, a receiver
      operating characteristic (ROC) curve was applied. Statistical significance was set at P <
      0.05. All analyzed P-values were two-sided. Statistical analyses were performed using the
      SPSS 25.0 software package (SPSS, Chicago). Bland-Altman plots with the mean difference and
      95 percent limit of agreement (LOA) were used to assess inter-observer agreement, and
      statistical analyses were done using MedCalc Statistical software.
    

Intervention name(s): no intervention
Intervention type(s): Other
Intervention description(s): no intervention
Observational model: Cohort
Time perspective: Retrospective
Sampling method: Non-Probability Sample
Study population: 
        The patient was enrolled in the 15-bed adult critical care unit in Adult General Hospital
      
Keywords: Pulsatility index of the superior mesenteric artery; Prolonged Mechanical Ventilation; cardiac valve surgery; intestinal perfusion