Original Article
Risk factors of prolonged mechanical ventilation following open heart surgery: what has changed over the last decade?
Abstract
Objective: To identify the risk factors for prolonged invasive mechanical ventilation after open heart
surgery in Pakistan.
Design: This study is based on retrospective analysis of database.
Place and duration: We conducted study of all patients who underwent open heart surgery at CPE
Institute of Cardiology, Multan from March 2009 to May 2011.
Patients & methods: The data was retrieved from the database in the form of electronic spreadsheet
which was then analyzed using SPSS software. The patients with incomplete data entries were removed
from the analysis resulting in a set of 1,617 patients The data of each patient consisted of 65 preoperative,
operative and postoperative variables. The data was summarized as means, medians and standard deviations
for numeric variables and frequencies and percentages or categoric variables. These risk factors were
compared using Chi-sqaure test. Their ODDs ratios and 95% confidence intervals of ODD’s Ratios and P
values were calculated.
Results: Out of a total of 1,617 patients, 77 patients (4.76%) had prolonged ventilation for a cumulated
duration of more than over 24 hours. Preoperative renal failure, emphysema, low EF (<30%), urgent
operation, preoperative critical state, prolonged bypass time, prolonged cross clamp time, complex surgical
procedures and peri-operative myocardial infarction were found to be risk factors for PIMV. Old age, female
gender, advanced ASA class, advanced NYHA class, diabetes mellitus, smoking, history of COPD, redo
surgery, left main stenosis, obesity and use of intra-aortic balloon pump were not found to have significant
ODDs ratios for PIMV. The patients with prolonged ventilation had significantly high mortality i.e. 32.47%
while the normal ventilation group had 0.32% overall mortality.
Conclusions: Many of the previously considered risk factors for prolonged ventilation after open heart
study are no more significant risk factors. However, prolonged ventilation continues to be associated with
very high mortality.
surgery in Pakistan.
Design: This study is based on retrospective analysis of database.
Place and duration: We conducted study of all patients who underwent open heart surgery at CPE
Institute of Cardiology, Multan from March 2009 to May 2011.
Patients & methods: The data was retrieved from the database in the form of electronic spreadsheet
which was then analyzed using SPSS software. The patients with incomplete data entries were removed
from the analysis resulting in a set of 1,617 patients The data of each patient consisted of 65 preoperative,
operative and postoperative variables. The data was summarized as means, medians and standard deviations
for numeric variables and frequencies and percentages or categoric variables. These risk factors were
compared using Chi-sqaure test. Their ODDs ratios and 95% confidence intervals of ODD’s Ratios and P
values were calculated.
Results: Out of a total of 1,617 patients, 77 patients (4.76%) had prolonged ventilation for a cumulated
duration of more than over 24 hours. Preoperative renal failure, emphysema, low EF (<30%), urgent
operation, preoperative critical state, prolonged bypass time, prolonged cross clamp time, complex surgical
procedures and peri-operative myocardial infarction were found to be risk factors for PIMV. Old age, female
gender, advanced ASA class, advanced NYHA class, diabetes mellitus, smoking, history of COPD, redo
surgery, left main stenosis, obesity and use of intra-aortic balloon pump were not found to have significant
ODDs ratios for PIMV. The patients with prolonged ventilation had significantly high mortality i.e. 32.47%
while the normal ventilation group had 0.32% overall mortality.
Conclusions: Many of the previously considered risk factors for prolonged ventilation after open heart
study are no more significant risk factors. However, prolonged ventilation continues to be associated with
very high mortality.
