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Risk factors for late extubation after coronary artery bypass grafting
Risk factors for late extubation after coronary artery bypass grafting Qiang Ji, MD, PhD,a Liangjie Chi, PhD,b Yunqing Mei, MD, PhD,a Xisheng Wang, MD, PhD,a Jing Feng, MD,a Jiangzhi Cai, MD, PhD,a and Yifeng Sun, MDa
OBJECTIVE: To evaluate the independent risk factors for late extubation after coronary artery bypass grafting (CABG). METHODS: Preoperative, intraoperative, and postoperative characteristics of patients undergoing isolated CABG between June 2005 and June 2008 at the Tongji Hospital were retrospectively analyzed. Elapsed time between CABG and extubation of more than 8 hours was defined as late extubation. RESULTS: The incidence of late extubation after CABG was 69.23% (288/416). Through univariate and logistic regression analysis, the independent risk factors for late extubation after CABG were older age (odds ratio [OR] = 4.804), duration of cardiopulmonary bypass (OR = 2.426), perioperative use of intra-aortic balloon pump (OR = 1.451), preoperative arterial oxygen partial pressure (OR = .204), and postoperative hemoglobin level (OR = .793). CONCLUSION: Older age, prolonged cardiopulmonary bypass time, perioperative intra-aortic balloon pump requirement, low preoperative arterial oxygen partial pressure, and low postoperative hemoglobin level were identified as the 5 independent risk factors for late extubation after CABG. (Heart LungÒ 2010;39:275–282.)
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ince Klineberg and colleagues1 reported early extubation within 8 hours after elective coronary artery bypass grafting (CABG) in 1977, it has been demonstrated that early extubation is feasible and safe.2-4 Early extubation improves ciliary function and mucous transport and reduces the incidence of pneumonia, lung atelectasis, and other pulmonary complications.5 It also ameliorates cardiac diastolic function,6 thereby shortening the length of intensive care unit (ICU) and hospital stay, thus cutting down on medical costs. A series of studies2-4,7,8 showed that 55% to 80% patients could be extubated within 8 hours after CABG. However, the proportion of early to late extubation at
From the aDepartment of Thoracic Cardiovascular Surgery of Tongji Hospital of Tongji University, Shanghai, P.R. China; and b Medical School of Tongji University, Shanghai, P.R. China. Corresponding author: Yunqing Mei and Qiang Ji, MD, PhD, Department of Thoraco-Cardiovascular Surgery of Tongji Hospital, Tongji University, 389 Xincun Rd, Shanghai, 200065, P.R. China. E-mail: [email protected] (Q.J.), drmeiyq2004@tongji. edu.cn (Y.M.) 0147-9563/$ – see front matter Crown Copyright Ó 2010 Published by Elsevier Inc. All rights reserved. doi:10.1016/j.hrtlng.2009.09.002
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Tongji Hospital and other medical centers in China was lower than that in the literature. This study sought to evaluate the risk factors for late extubation after CABG by reviewing 128 and 288 consecutive patients with early and late extubation, respectively, who underwent isolated CABG at Tongji Hospital between June 2005 and June 2008.
MATERIALS AND METHODS Patients From June 2005 to June 2008, 416 consecutive patients (335 male and 81 female, with a mean age of 66.36 9.69 years) with coronary artery disease underwent isolated CABG. The characteristics of the entire cohort are shown in Table I. Coronary artery angiography revealed double-vessel disease in 15 cases and triple-vessel disease in 401 cases. All patients underwent fast-track anesthesia (anesthesia was induced with midazolam [2-3 mg], fentanyl [.2 mg], propofol [.5-1.5 mg/kg], and vecuronium) and maintained with isoflurane and continuous infusion of propofol (2-5 mg/kg/h). Fentanyl (.1-.2 mg) was intravenously administered before skin incision, sternotomy, aortic cannulation, and initiation of cardiopulmonary bypass. The total amount of
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Table I Characteristics of the entire cohort Preoperative variables Age (y) Age > 65 y Gender (female/male) BMI (kg/m2) Recent smoking Diabetes mellitus Hypertension Dyslipidemia Renal dysfunction Diuretics Cerebrovascular disease COPD Recent MI Unstable angina Prior heart operation Congestive heart failure Level of hemoglobin (g/dL) LVEF LVEDD (mm) Triple vessel disease Left main trunk disease Left ventricular aneurysm PO2 (mm Hg) EuroSCORE (score) EuroSCORE > 6 Intraoperative variables Emergent operation Use of CPB CPB time (min) ACC time (min) Operation time (min) Number of grafts Quantity of operative bleeding (mL) Intraoperative infusion volume (mL) Postoperative variables (before decannulation) Duration of intubation (h) Perioperative IABP requirement Quantity of drainage (mL) Reoperation for bleeding Hemoglobin (g/dL) MI Atrial fibrillation Ventricular fibrillation Acute renal failure Stroke
66.4 9.7 258 (62.02%) 81/335 26.1 2.4 121 (29.09%) 119 (28.61%) 336 (80.77%) 264 (63.46%) 20 (4.81%) 44 (10.58%) 125 (30.05%) 70 (16.83%) 36 (8.65%) 160 (38.46%) 3 (.72%) 243 (58.41%) 13.7 1.5 .53 .10 52.6 8.4 401 (96.39%) 109 (26.20%) 37 (8.89%) 73.1 9.9 4.87 1.79 256 (61.54%) 12 (2.88%) 188 (45.19%) 112.9 21.2 64.3 38.6 264.9 72.1 3.2 .7 472 151 3824 1276 16.3 5.3 21 (5.05%) 362 196 15 (3.61%) 7.8 1.3 1 (.24%) 144 (34.62%) 1 (.24%) 25 (6.01%) 3 (.72%)
BMI, body mass index; COPD, chronic obstructive pulmonary disease; MI, myocardial infarction; LVEF, left ventricular ejection fraction; LVEDD, left ventricular end-diastolic diameter; CPB, cardiopulmonary bypass; ACC, aortic crossclamping; EuroSCORE, European System for Cardiac Operative Risk Evaluation; IABP, intra-aortic balloon pump; ICU, intensive care unit.
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fentanyl was less than 15 mg/kg during operation. A total of 276 patients underwent beating heart CABG (among whom 48 were passed on cardiopulmonary bypass during the procedure), and 140 patients underwent cardioplegic arrest CABG. The number of bypass conduits ranged from 2 to 5 (mean 3.2 grafts) per patient. The left internal thoracic artery was used as a bypass conduit in 96.15% of patients (n = 400), the radial artery was used in 66.59% of patients (n = 277), and the great saphenous vein graft was used in 85.34% of patients (n = 355). Overall mean European System for Cardiac Operative Risk Evaluation9 (EuroSCORE) was 4.87 1.79. Hemodynamic parameters were monitored by the Swan-Ganz catheter (Arrow International, Inc, Reading, PA) during and after operation. Arterial oxygen partial pressure (PO2) and hemoglobin level were preoperatively, intraoperative, and postoperatively measured by the blood gas analyzer (i-STAT Corporation, Princeton, NJ). Left ventricular ejection fraction and left ventricular end-diastolic diameter were preoperatively and postoperatively measured by the Doppler-Ultrasound (GE VIVID 7, Fairfield, CT).
Criteria for extubation and definition of late extubation Criteria for extubation10 included an alert and hemodynamically stable patient with no excessive bleeding, ability of the patient to breathe through a T-tube for at least 30 minutes with a fraction of inspired oxygen of less than .40, and a respiratory rate less than 25 breaths/min, an arterial blood PO2 greater than 70 mm Hg, a PCO2 less than 40 mm Hg, and a pH greater than 7.35, with no metabolic acidosis. Other criteria were a tidal volume of 6 mL/kg, a peak negative inspiratory pressure of less than 20 cmH2O, and a mandatory chest radiograph before extubation to rule out pneumothorax, pleural effusion, and atelectasis. With reference to previous reports,2,11,12 in which 8 hours was taken as a cutoff point to discriminate between early and late extubation, we used the same criterion in our study to describe early and late extubation, that is, elapsed time between CABG and extubation of more than 8 hours was defined as late extubation and that of less than 8 hours was defined as early extubation.
Methods The preoperative, intraoperative, and postoperative relevant data of all selected patients were retrospectively investigated and analyzed. Preoperative information included age, gender, body mass index,
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recent smoking (within 4 weeks of surgery), diabetes mellitus, hypertension, dyslipidemia, renal dysfunction (creatinine > 2.5 mg/dL or requiring dialysis), diuretics, cerebrovascular disease, chronic obstructive pulmonary disease, recent myocardial infarction (evidence of myocardial infarction within the last 30 days before surgery), unstable angina (use of intravenous nitrates within 48 hours of surgery), preoperative heart failure (New York Heart Association class III and IV), preoperative hemoglobin level, left ventricular ejection fraction, left ventricular end-diastolic diameter, PO2, left main trunk disease, and left ventricular aneurysm. Intraoperative variables included emergency operation, use of cardiopulmonary bypass, cardiopulmonary bypass time, aortic crossclamping time, number of grafts, and operation time. Postoperative variables included perioperative intra-aortic balloon pump (IABP) requirement, reoperation for bleeding, hemoglobin level, acute myocardial infarction (new Q-wave infarction within 48 hours after surgery), acute renal failure (creatinine > 2.5 mg/dL for > 7 days or requiring dialysis), stroke (new permanent neurologic event; early stroke: within 24 hours and delayed stroke > 24 hours postoperatively), and postoperative atrial and ventricular fibrillation.10,13,14
Statistical analysis Statistical analysis was performed using the SPSS 10 statistical software package (SPSS Inc, Chicago, IL). All P values less than .05 were considered statistically significant. Univariate analysis was performed using the unpaired t test or t’ test according to homogeneity test for variance to compare measurement data and chi-square or Fisher’s exact test to compare enumeration data. The relative risk factors obtained through univariate analysis were then entered into logistic regression analysis (early or late extubation as independent variable, relative risk factors as dependent variables), and the independent risk factors for postoperative late extubation were identified.
RESULTS A total of 416 consecutive patients who underwent isolated CABG were entered into this study. The mean duration time of intubation was 16.3 5.3 hours. Among them, 288 patients (69.23%) were extubated beyond 8 hours after CABG. The mean elapsed time between CABG and extubation in the early extubation group was 7.2 .8 hours, which was significantly lower than that in the late extubation group with a mean elapsed time of 20.1 6.6 hours (P < .0001).
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Table II Comparison of post-extubation data between early and late extubation groups
Reintubation Apnea Hypoxemia Pneumonia Pulmonary atelectasis Respiratory failurea LCOS Atrial fibrillation Ventricular fibrillation AMI ARF Stroke DSWI ICU stay (d) Hospital stay (d) Hospital mortality
Early extubation (n = 128)
Late extubation (n = 288)
P value
3 (2.34%) 38 (29.69%) 33 (25.78%) 11 (8.59%) 10 (7.81%) 2 (1.56%) 4 (3.13%) 15 (11.72%) 1 (.78%) 1 (.78%) 4 (3.13%) 2 (1.56%) 3 (2.34%) 2.80 .52 7.83 2.56 2 (1.56%)
5 (1.74%) 89 (30.90%) 81 (28.13%) 50 (17.36%) 25 (8.68%) 21 (7.29%) 8 (2.78%) 42 (14.58%) 3 (1.04%) 1 (.35%) 12 (4.17%) 3 (1.04%) 9 (3.13%) 4.12 .59 10.38 3.42 5 (1.74%)
.7059 .8188 .3559 .0236 .8500 .0187 1.0000 .5369 1.0000 .0942 .7849 .6455 .7624 <.001 <.001 .6300
LCOS, low cardiac output syndrome; AMI, acute myocardial infarction; ARF, acute renal failure; DSWI, deep sternal wound infection; ICU, intensive care unit. a Respiratory failure: prolonged ventilator therapy > 72 h.
Table II displays the complications after extubation and the length of ICU and hospital stays. As shown in Table II, there were no significant differences in the incidence of most complications, except for pneumonia and respiratory failure. The length of ICU and hospital stays in the late extubation group was significantly longer than that in the early extubation group. Results of the univariate analysis are shown in Tables III and IV. Age more than 65 years, recent smoking, preoperative renal dysfunction, preoperative use of diuretics, preoperative chronic obstructive pulmonary disease, preoperative heart failure, preoperative level of blood serum creatinine, preoperative left ventricular ejection fraction, preoperative PO2, CABG with cardiopulmonary bypass, duration of cardiopulmonary bypass, perioperative IABP requirement, reoperation for bleeding, postoperative atrial fibrillation, and postoperative level of hemoglobin were relative risk factors for late extubation after CABG. The relative risk factors obtained through the univariate analysis were then entered into multivariate logistic regression analysis (early or late extubation as independent variable and relative risk factors obtained through univariate analysis as dependent
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variables). As shown in Table V, independent risk factors for late extubation included older age (>65 years) (odds ratio [OR] = 4.804; 95% confidence interval [CI], 2.351-12.376), duration of cardiopulmonary bypass (OR = 2.426; 95% CI, 1.395-7.256), perioperative IABP requirement (OR = 1.451; 95% CI, 1.125-3.783), preoperative arterial PO2 (OR = .204; 95% CI, .061-.758), and postoperative hemoglobin level (OR = .793; 95% CI, .337-.956).
DISCUSSION In addition to the length of ICU and hospital stay, late extubation correlated with negative respiratory outcomes in this study. Although there were no significant differences in the incidence of reintubation, apnea, hypoxemia, and pulmonary atelectasis between early and late extubation groups, longer ventilation support led to a higher incidence of pneumonia and respiratory failure. The fact that there were no significant differences in the incidence of reintubation and pulmonary atelectasis between early and late extubation groups could be related to the small ‘‘absolute value’’ (reintubation: 3 vs 5; pulmonary atelectasis: 10 vs 25), the latter probably resulting from the limited sample size. No
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Table III Comparison of risk factors between early and late extubation groups Factors
Preoperation Age > 65 y Female Recent smoking Diabetes mellitus Hypertension Dyslipidemia Renal dysfunction Diuretics Cerebrovascular disease COPD Recent MI Prior heart operation Prior unstable angina Congestive heart failure Triple vessel disease Left main trunk disease Left ventricular aneurysm Intra-operation Emergency surgery Use of CPB Use of ACC Postoperation (before extubation) Perioperative IABP requirement Reoperation for bleeding AMI ARF Stroke Atrial fibrillation Ventricular fibrillation
Early extubation (n = 128)
Late extubation (n = 288)
P value
38 (29.69%) 21 (16.41%) 28 (21.88%) 32 (25.00%) 101 (78.91%) 86 (67.19%) 2 (1.56%) 8 (6.25%) 45 (35.16%) 14 (10.94%) 14 (10.94%) 1 (.78%) 45 (35.16%) 61 (47.66%) 121 (94.53%) 41 (32.03%)
220 (76.39%) 60 (20.83%) 93 (32.29%) 87 (30.21%) 235 (81.60%) 178 (61.81%) 18 (6.25%) 36 (12.50%) 80 (27.78%) 56 (19.44%) 22 (7.64%) 2 (.69%) 115 (39.93%) 182 (63.19%) 280 (97.22%) 68 (23.61%)
<.0001 .3481 .0352 .2926 .5899 .3217 .0457 .0009 .1338 .0336 .2640 1.0000 .3835 .0036 .2519 .0904
10 (7.81%)
27 (9.38%)
.7106
3 (2.34%) 42 (32.81%) 35 (27.34%)
9 (3.13%) 146 (50.69%) 105 (36.46%)
.7624 .0009 .0731
2 (1.56%) 1 (.78%) 0 6 (4.69%) 1 (.78%) 31 (24.22%) 0
19 (6.60%) 14 (4.86%) 1 (.35%) 19 (6.60%) 2 (.69%) 113 (39.24%) 1 (.35%)
.0296 .0451 1.0000 .5112 1.0000 .0036 1.0000
AMI, acute myocardial infarction; IABP, intra-aortic balloon pump; COPD, chronic obstructive pulmonary disease; CPB, cardiopulmonary bypass; ACC, aortic cross clamping; ARF, acute renal failure; MI, myocardial infarction.
significant difference in the incidence of hypoxemia between early and late extubation groups could be related to the findings of our previous study,15 in which it was shown that intubation time was not an independent risk factor of postoperative hypoxemia after CABG. In addition, there were no significant differences in the incidence of low cardiac output and acute myocardial infarction between the 2 groups, which indicated that early extubation did not increase the incidence of low cardiac output and acute myocardial infarction. Improvement in cardiopulmonary performance, shorter ICU and hospital stays, and reduction in
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costs could be achieved when cardiac surgical patients were weaned from the mechanical ventilator at the appropriate time.2-4,7,8 On the other hand, prolonged ventilation support may have contributed to increased morbidity, mortality, and cost.16,17 Thus, early extubation was recommended. In this study, 288 patients were included in the late extubation group, with an incidence of 69.23%, which was higher than the 20% to 45% documented in the literature.2-4,7,8 Severity of illness measured by the EuroSCORE scale in this study (mean EuroSCORE was 4.87 1.79; 256 patients with a EuroSCORE of > 6, accounting for 61.54%, were included in
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Table IV Comparison of risk factors between early and late extubation groups Factor
Age (y) BMI (kg/m2) Preoperative Scr (mg/dL) Preoperative Hb (g/dL) Preoperative LVEF Preoperative LVEDD (mm) Preoperative PO2 (mm Hg) CPB (min) ACC (min) Operation time (min) Number of grafts Postoperative Hb (g/dL)
Early extubation (n = 128)
128 128 128 128 128 128 128 42 35 128 128 128
64.5 10.1 25.8 2.6 .86 .29 13.8 1.5 .55 .10 51.6 5.8 75.0 11.3 97.8 15.3 52.6 12.0 260.0 67.6 3.1 .7 8.5 1.7
Late extubation (n = 288)
288 288 288 288 288 288 288 146 105 288 288 288
68.3 8.0 26.2 2.3 .98 .28 13.6 1.6 .52 .09 53.0 9.6 72.0 8.6 118.2 23.0 68.8 48.8 266.1 78.6 3.2 .8 7.1 .9
t (or t’)
P
4.1412 1.5715 3.9901 1.6027 3.0307 1.5299 2.9704 5.3833 1.9469 .7663 .8581 11.0608
<.0001 .1168 <.0001 .1098 .0026 .1268 .0031 <.0001 .0536 .4439 .3913 <.0001
BMI, body mass index; Scr, serum creatinine; LVEF, left ventricular ejection fraction; LVEDD, left ventricular end-diastolic diameter; PO2, arterial partial pressure of oxygen; CPB, cardiopulmonary bypass; ACC, aortic crossclamping; Hb, hemoglobin.
Table V Multivariate regression results for independent risk factors Predictors
Age (>65 y) Duration of CPB Perioperative IABP requirement Preoperative PO2 Postoperative Hb
OR value
4.804 2.426 1.451 .204 .793
95% CI
2.351-12.376 1.395-7.256 1.125-3.783 .061-.758 .337-.956
P value
.007 .010 .045 .001 .014
CI, confidence interval; CPB, cardiopulmonary bypass; Hb, hemoglobin; IABP, intra-aortic balloon pump; OR, odds ratio; PO2, arterial partial pressure of oxygen.
a high-risk group), intraoperative and postoperative course, and preoperative, intraoperative, and postoperative factors may have independently or mutually contributed toward longer ventilation support after CABG. In addition, because of the learning curve in CABG and lack of experience, consensus of opinion on the timing of extubation after CABG has not been established in our country; thus, it was crucial for clinicians to evaluate the relative risk factors for late extubation after CABG so that the appropriate time for extubation could be found. In this study, the independent risk factors for late extubation after CABG were older age (>65 years), prolonged cardiopulmonary bypass, perioperative
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IABP requirement, low preoperative PO2, and low postoperative hemoglobin. Older age was one of the major risk factors contributing to late extubation after CABG. Patients aged more than 65 years who underwent CABG often had multiple concurrent diseases, poor cardiopulmonary reserve, and diffuse vascular sclerostenosis. They had a further reduction in their cardiopulmonary performance after CABG with or without cardiopulmonary bypass, and were more prone to postoperative low cardiac output and pulmonary complications, usually requiring longer ventilation support. In addition, age more than 65 years has been shown to be an independent risk factor of atrial
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fibrillation after CABG.18 Although atrial fibrillation is a relatively benign arrhythmia, persistent or frequent atrial fibrillation can seriously interfere with the hemodynamics, increase myocardial oxygen consumption, reduce cardiac output, and lead to longer ventilation support. Therefore, it is important to treat atrial fibrillation, especially after CABG, when patients are more vulnerable to the effects of atrial fibrillation. Prolonged cardiopulmonary bypass was also a major risk factor for late extubation after CABG. Cardiopulmonary bypass is associated with a systemic inflammatory response, the production of oxygenderived free radicals, the activation of polymorphonuclear neutrophils, and the complement cascade and release of vessel constringent factors.19-21 All these have negative influences on important organs, such as the heart, lung, brain, and kidney. Prolonged cardiopulmonary bypass was expected to negatively influence cardiopulmonary and renal functions, and thus requirement of longer ventilation support. In addition, prolonged cardiopulmonary bypass associated with complex disease, complicated operation, and imperfect myocardial protection may have led to longer ventilation support. Thus, further refinement of surgical techniques, decrease in cardiopulmonary bypass time, and performance of off-pump CABG can lead to early extubation. Low postoperative hemoglobin level seemed to be an independent risk factor for postoperative late extubation. Low postoperative hemoglobin level may have been related to poor oxygen transport. A lower hemoglobin level after surgery increases the potential for blood transfusion. This in turn may have resulted in a change in the pulmonary ventilation/blood flow ratio and induction of pulmonary capillary embolism, thus further affecting respiratory functions. Consequently, early extubation may not have been possible. Thus, meticulous intraoperative hemostasis is recommended. Perioperative IABP requirement suggested poor cardiac performance or even severe myocardial ischemia and unstable hemodynamics. After CABG, patients with IABP usually required adequate sedation and longer ventilation support to provide adequate oxygen supply and reduce respiratory workload and myocardial oxygen consumption. Low preoperative PO2 often suggested poor cardiopulmonary function or severe chronic obstructive pulmonary disease in patients. After CABG, further depression in cardiopulmonary function was expected in these patients who consequently were more prone to low cardiac output and postoperative respiratory failure, thus requiring longer
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ventilation support. Therefore, proper perioperative management of cardiopulmonary dysfunction in patients undergoing CABG may help shorten postoperative ventilation support. Many studies have shown that female gender was an independent risk factor for late extubation after CABG. However, there was no significant difference in the proportion of female to male patients between the late and early extubation groups (21/107 vs 60/ 228), which may be related to fewer female patients undergoing CABG in this study (only 19.47%). In addition, many studies showed that preoperative renal dysfunction was also an independent high risk factor for late extubation after CABG. Although the number of patients with preoperative renal dysfunction in the late extubation group was significantly higher than that in the early extubation group (6.25% vs 1.56%), through the logistic regression analysis, preoperative renal dysfunction was not found to be an independent risk factor for late extubation after CABG in this study. This could be due to the small ‘‘absolute value’’ (2 vs 18 patients) as a consequence of the limited sample size.
LIMITATIONS The retrospective nature and small sample size of this study were the main limitations of this study. Another limitation of this study was the lack of detailed respiratory function data. PO2 was measured preoperatively, but forced expiratory volume in 1 second and forced vital capacity were not routinely measured before CABG at Tongji Hospital.
CONCLUSIONS Elective early extubation was safe and did not increase postoperative morbidity. Older age, prolonged cardiopulmonary bypass, perioperative IABP requirement, low preoperative PO2, and low postoperative hemoglobin level were the 5 independent risk factors for late extubation after CABG. Early extubation may be achieved by reducing intraoperative and postoperative hemorrhage, thus maintaining a reasonable postoperative hemoglobin level and shortening the cardiopulmonary bypass time. The proper perioperative management of cardiopulmonary dysfunction in older patients may contribute toward reducing postoperative ventilation support and facilitate early extubation. REFERENCES 1. Klineberg PL, Geer RT, Hirsh RA, Aukburg SJ. Early extubation after coronary artery bypass graft surgery. Crit Care Med 1977; 5:272-4.
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Late extubation after CABG 2. Hawkes CA, Dhileepan S, Foxcroft D. Early extubation for adult cardiac surgical patients. Cochrane Database Syst Rev 2003;(4). CD003587. 3. Reis J, Mota JC, Ponce P, Costa-Pereira A, Guerreiro M. Early extubation does not increase complication rates after coronary artery bypass graft surgery with cardiopulmonary bypass. Eur J Cardiothorac Surg 2002;21:1026-30. 4. Rashid A, Sattar KA, Dar MI, Khan AB. Analyzing the outcome of early versus prolonged extubation following cardiac surgery. Ann Thorac Cardiovasc Surg 2008;14:218-23. 5. Weissman C. Pulmonary complications after cardiac surgery. Semin Cardiothorac Vasc Anesth 2004;8:185-211. 6. Verrier ED, Wright IH, Cochran RP, Spiess BD. Changes in cardiovascular surgical approaches to achieve early extubation. J Cardiothorac Vasc Anesth 1995;9:10-5. 7. Wong DT, Cheng DC, Kustra R, Tibshirani R, Karski J, CarrollMunro J, et al. Risk factors of delayed extubation, prolonged length of stay in the intensive care unit, and mortality in patients undergoing coronary artery bypass graft with fast-track cardiac anesthesia: a new cardiac risk score. Anesthesiology 1999;91:936-44. 8. Silbert BS, Santamaria JD, O’Brien JL, Blyth CM, Kelly WJ, Molnar RR. Early extubation following coronary artery bypass surgery: a prospective randomized controlled trial. The Fast Track Cardiac Care Team. Chest 1998;113:1481-8. 9. Nashef SA, Roques F, Michel P, Gauducheau E, Lemeshow S, Salamon R. European system for cardiac operative risk evaluation (EuroSCORE). Eur J Cardiothorac Surg 1999;16:9-13. 10. Amram JC, Michael GK, George F, Benjamin M, Diklah G, Arie S. Morbid results of prolonged intubation after coronary artery bypass surgery. Chest 2000;118:1724-31. 11. Dumas A, Dupuis GH, Searle N, Cartier R. Early versus late extubation after coronary artery bypass grafting: effects on cognitive function. J Cardiothorac Vasc Anesth 1999;13: 130-5.
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Ji et al 12. Lee JH, Graber R, Popple CG, Furey E, Lyons T, Murrell HK, et al. Safety and efficacy of early extubation of elderly coronary artery bypass surgery patients. J Cardiothorac Vasc Anesth 1998;12:381-4. 13. Filsoufi F, Rahmanian PB, Castillo JG, Mechanick JI, Sharma SK, Adams DH. Diabetes is not a risk factor for hospital mortality following contemporary coronary artery bypass grafting. Interact Cardiovasc Thorac Surg 2007;6:753-8. 14. Antunes PE, Prieto D, Ferra˜o de Oliveira J, Antunes MJ. Renal dysfunction after myocardial revascularization. Eur J Cardiothorac Surg 2004;25:597-604. 15. Ji Q, Mei Y, Wang X, Feng J, Cai J, Sun Y, et al. Study on the risk factors of postoperative hypoxemia in patients undergoing coronary artery bypass grafting. Circ J 2008;72:1975-80. 16. Pappalardo F, Franco A, Landoni G, Cardano P, Zangrillo A, Alfieri O. Long-term outcome and quality of life of patients requiring prolonged mechanical ventilation after cardiac surgery. Eur J Cardiothorac Surg 2004;25:548-52. 17. Serrano N, Garcı´a C, Villegas J, Huidobro S, Henry CC, Santacreu R, et al. Epidemiological Project for ICU Research and Evaluation (EPICURE). Prolonged intubation rates after coronary artery bypass surgery and ICU risk stratification score. Chest 2005;128:595-601. 18. Mamoun NF, Xu M, Sessler DI, Sabik JF, Bashour CA. Propensity matched comparison of outcomes in older and younger patients after coronary artery bypass graft surgery. Ann Thorac Surg 2008;85:1974-9. 19. Lagan AL, Melley DD, Evans TW, Quinlan GJ. Pathogenesis of the systemic inflammatory syndrome and acute lung injury: role of iron mobilization and decompartmentalization. Am J Physiol Lung Cell Mol Physiol 2008;294:L161-74. 20. Hess PJ Jr. Systemic inflammatory response to coronary artery bypass graft surgery. Am J Health Syst Pharm 2005;62:S6-9. 21. Levy JH, Tanaka KA. Inflammatory response to cardiopulmonary bypass. Ann Thorac Surg 2003;75:S715-20.
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OBJECTIVE: To evaluate the independent risk factors for late extubation after coronary artery bypass grafting (CABG). METHODS: Preoperative, intraoperative, and postoperative characteristics of patients undergoing isolated CABG between June 2005 and June 2008 at the Tongji Hospital were retrospectively analyzed. Elapsed time between CABG and extubation of more than 8 hours was defined as late extubation. RESULTS: The incidence of late extubation after CABG was 69.23% (288/416). Through univariate and logistic regression analysis, the independent risk factors for late extubation after CABG were older age (odds ratio [OR] = 4.804), duration of cardiopulmonary bypass (OR = 2.426), perioperative use of intra-aortic balloon pump (OR = 1.451), preoperative arterial oxygen partial pressure (OR = .204), and postoperative hemoglobin level (OR = .793). CONCLUSION: Older age, prolonged cardiopulmonary bypass time, perioperative intra-aortic balloon pump requirement, low preoperative arterial oxygen partial pressure, and low postoperative hemoglobin level were identified as the 5 independent risk factors for late extubation after CABG. (Heart LungÒ 2010;39:275–282.)
S
ince Klineberg and colleagues1 reported early extubation within 8 hours after elective coronary artery bypass grafting (CABG) in 1977, it has been demonstrated that early extubation is feasible and safe.2-4 Early extubation improves ciliary function and mucous transport and reduces the incidence of pneumonia, lung atelectasis, and other pulmonary complications.5 It also ameliorates cardiac diastolic function,6 thereby shortening the length of intensive care unit (ICU) and hospital stay, thus cutting down on medical costs. A series of studies2-4,7,8 showed that 55% to 80% patients could be extubated within 8 hours after CABG. However, the proportion of early to late extubation at
From the aDepartment of Thoracic Cardiovascular Surgery of Tongji Hospital of Tongji University, Shanghai, P.R. China; and b Medical School of Tongji University, Shanghai, P.R. China. Corresponding author: Yunqing Mei and Qiang Ji, MD, PhD, Department of Thoraco-Cardiovascular Surgery of Tongji Hospital, Tongji University, 389 Xincun Rd, Shanghai, 200065, P.R. China. E-mail: [email protected] (Q.J.), drmeiyq2004@tongji. edu.cn (Y.M.) 0147-9563/$ – see front matter Crown Copyright Ó 2010 Published by Elsevier Inc. All rights reserved. doi:10.1016/j.hrtlng.2009.09.002
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Tongji Hospital and other medical centers in China was lower than that in the literature. This study sought to evaluate the risk factors for late extubation after CABG by reviewing 128 and 288 consecutive patients with early and late extubation, respectively, who underwent isolated CABG at Tongji Hospital between June 2005 and June 2008.
MATERIALS AND METHODS Patients From June 2005 to June 2008, 416 consecutive patients (335 male and 81 female, with a mean age of 66.36 9.69 years) with coronary artery disease underwent isolated CABG. The characteristics of the entire cohort are shown in Table I. Coronary artery angiography revealed double-vessel disease in 15 cases and triple-vessel disease in 401 cases. All patients underwent fast-track anesthesia (anesthesia was induced with midazolam [2-3 mg], fentanyl [.2 mg], propofol [.5-1.5 mg/kg], and vecuronium) and maintained with isoflurane and continuous infusion of propofol (2-5 mg/kg/h). Fentanyl (.1-.2 mg) was intravenously administered before skin incision, sternotomy, aortic cannulation, and initiation of cardiopulmonary bypass. The total amount of
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Table I Characteristics of the entire cohort Preoperative variables Age (y) Age > 65 y Gender (female/male) BMI (kg/m2) Recent smoking Diabetes mellitus Hypertension Dyslipidemia Renal dysfunction Diuretics Cerebrovascular disease COPD Recent MI Unstable angina Prior heart operation Congestive heart failure Level of hemoglobin (g/dL) LVEF LVEDD (mm) Triple vessel disease Left main trunk disease Left ventricular aneurysm PO2 (mm Hg) EuroSCORE (score) EuroSCORE > 6 Intraoperative variables Emergent operation Use of CPB CPB time (min) ACC time (min) Operation time (min) Number of grafts Quantity of operative bleeding (mL) Intraoperative infusion volume (mL) Postoperative variables (before decannulation) Duration of intubation (h) Perioperative IABP requirement Quantity of drainage (mL) Reoperation for bleeding Hemoglobin (g/dL) MI Atrial fibrillation Ventricular fibrillation Acute renal failure Stroke
66.4 9.7 258 (62.02%) 81/335 26.1 2.4 121 (29.09%) 119 (28.61%) 336 (80.77%) 264 (63.46%) 20 (4.81%) 44 (10.58%) 125 (30.05%) 70 (16.83%) 36 (8.65%) 160 (38.46%) 3 (.72%) 243 (58.41%) 13.7 1.5 .53 .10 52.6 8.4 401 (96.39%) 109 (26.20%) 37 (8.89%) 73.1 9.9 4.87 1.79 256 (61.54%) 12 (2.88%) 188 (45.19%) 112.9 21.2 64.3 38.6 264.9 72.1 3.2 .7 472 151 3824 1276 16.3 5.3 21 (5.05%) 362 196 15 (3.61%) 7.8 1.3 1 (.24%) 144 (34.62%) 1 (.24%) 25 (6.01%) 3 (.72%)
BMI, body mass index; COPD, chronic obstructive pulmonary disease; MI, myocardial infarction; LVEF, left ventricular ejection fraction; LVEDD, left ventricular end-diastolic diameter; CPB, cardiopulmonary bypass; ACC, aortic crossclamping; EuroSCORE, European System for Cardiac Operative Risk Evaluation; IABP, intra-aortic balloon pump; ICU, intensive care unit.
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fentanyl was less than 15 mg/kg during operation. A total of 276 patients underwent beating heart CABG (among whom 48 were passed on cardiopulmonary bypass during the procedure), and 140 patients underwent cardioplegic arrest CABG. The number of bypass conduits ranged from 2 to 5 (mean 3.2 grafts) per patient. The left internal thoracic artery was used as a bypass conduit in 96.15% of patients (n = 400), the radial artery was used in 66.59% of patients (n = 277), and the great saphenous vein graft was used in 85.34% of patients (n = 355). Overall mean European System for Cardiac Operative Risk Evaluation9 (EuroSCORE) was 4.87 1.79. Hemodynamic parameters were monitored by the Swan-Ganz catheter (Arrow International, Inc, Reading, PA) during and after operation. Arterial oxygen partial pressure (PO2) and hemoglobin level were preoperatively, intraoperative, and postoperatively measured by the blood gas analyzer (i-STAT Corporation, Princeton, NJ). Left ventricular ejection fraction and left ventricular end-diastolic diameter were preoperatively and postoperatively measured by the Doppler-Ultrasound (GE VIVID 7, Fairfield, CT).
Criteria for extubation and definition of late extubation Criteria for extubation10 included an alert and hemodynamically stable patient with no excessive bleeding, ability of the patient to breathe through a T-tube for at least 30 minutes with a fraction of inspired oxygen of less than .40, and a respiratory rate less than 25 breaths/min, an arterial blood PO2 greater than 70 mm Hg, a PCO2 less than 40 mm Hg, and a pH greater than 7.35, with no metabolic acidosis. Other criteria were a tidal volume of 6 mL/kg, a peak negative inspiratory pressure of less than 20 cmH2O, and a mandatory chest radiograph before extubation to rule out pneumothorax, pleural effusion, and atelectasis. With reference to previous reports,2,11,12 in which 8 hours was taken as a cutoff point to discriminate between early and late extubation, we used the same criterion in our study to describe early and late extubation, that is, elapsed time between CABG and extubation of more than 8 hours was defined as late extubation and that of less than 8 hours was defined as early extubation.
Methods The preoperative, intraoperative, and postoperative relevant data of all selected patients were retrospectively investigated and analyzed. Preoperative information included age, gender, body mass index,
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recent smoking (within 4 weeks of surgery), diabetes mellitus, hypertension, dyslipidemia, renal dysfunction (creatinine > 2.5 mg/dL or requiring dialysis), diuretics, cerebrovascular disease, chronic obstructive pulmonary disease, recent myocardial infarction (evidence of myocardial infarction within the last 30 days before surgery), unstable angina (use of intravenous nitrates within 48 hours of surgery), preoperative heart failure (New York Heart Association class III and IV), preoperative hemoglobin level, left ventricular ejection fraction, left ventricular end-diastolic diameter, PO2, left main trunk disease, and left ventricular aneurysm. Intraoperative variables included emergency operation, use of cardiopulmonary bypass, cardiopulmonary bypass time, aortic crossclamping time, number of grafts, and operation time. Postoperative variables included perioperative intra-aortic balloon pump (IABP) requirement, reoperation for bleeding, hemoglobin level, acute myocardial infarction (new Q-wave infarction within 48 hours after surgery), acute renal failure (creatinine > 2.5 mg/dL for > 7 days or requiring dialysis), stroke (new permanent neurologic event; early stroke: within 24 hours and delayed stroke > 24 hours postoperatively), and postoperative atrial and ventricular fibrillation.10,13,14
Statistical analysis Statistical analysis was performed using the SPSS 10 statistical software package (SPSS Inc, Chicago, IL). All P values less than .05 were considered statistically significant. Univariate analysis was performed using the unpaired t test or t’ test according to homogeneity test for variance to compare measurement data and chi-square or Fisher’s exact test to compare enumeration data. The relative risk factors obtained through univariate analysis were then entered into logistic regression analysis (early or late extubation as independent variable, relative risk factors as dependent variables), and the independent risk factors for postoperative late extubation were identified.
RESULTS A total of 416 consecutive patients who underwent isolated CABG were entered into this study. The mean duration time of intubation was 16.3 5.3 hours. Among them, 288 patients (69.23%) were extubated beyond 8 hours after CABG. The mean elapsed time between CABG and extubation in the early extubation group was 7.2 .8 hours, which was significantly lower than that in the late extubation group with a mean elapsed time of 20.1 6.6 hours (P < .0001).
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Table II Comparison of post-extubation data between early and late extubation groups
Reintubation Apnea Hypoxemia Pneumonia Pulmonary atelectasis Respiratory failurea LCOS Atrial fibrillation Ventricular fibrillation AMI ARF Stroke DSWI ICU stay (d) Hospital stay (d) Hospital mortality
Early extubation (n = 128)
Late extubation (n = 288)
P value
3 (2.34%) 38 (29.69%) 33 (25.78%) 11 (8.59%) 10 (7.81%) 2 (1.56%) 4 (3.13%) 15 (11.72%) 1 (.78%) 1 (.78%) 4 (3.13%) 2 (1.56%) 3 (2.34%) 2.80 .52 7.83 2.56 2 (1.56%)
5 (1.74%) 89 (30.90%) 81 (28.13%) 50 (17.36%) 25 (8.68%) 21 (7.29%) 8 (2.78%) 42 (14.58%) 3 (1.04%) 1 (.35%) 12 (4.17%) 3 (1.04%) 9 (3.13%) 4.12 .59 10.38 3.42 5 (1.74%)
.7059 .8188 .3559 .0236 .8500 .0187 1.0000 .5369 1.0000 .0942 .7849 .6455 .7624 <.001 <.001 .6300
LCOS, low cardiac output syndrome; AMI, acute myocardial infarction; ARF, acute renal failure; DSWI, deep sternal wound infection; ICU, intensive care unit. a Respiratory failure: prolonged ventilator therapy > 72 h.
Table II displays the complications after extubation and the length of ICU and hospital stays. As shown in Table II, there were no significant differences in the incidence of most complications, except for pneumonia and respiratory failure. The length of ICU and hospital stays in the late extubation group was significantly longer than that in the early extubation group. Results of the univariate analysis are shown in Tables III and IV. Age more than 65 years, recent smoking, preoperative renal dysfunction, preoperative use of diuretics, preoperative chronic obstructive pulmonary disease, preoperative heart failure, preoperative level of blood serum creatinine, preoperative left ventricular ejection fraction, preoperative PO2, CABG with cardiopulmonary bypass, duration of cardiopulmonary bypass, perioperative IABP requirement, reoperation for bleeding, postoperative atrial fibrillation, and postoperative level of hemoglobin were relative risk factors for late extubation after CABG. The relative risk factors obtained through the univariate analysis were then entered into multivariate logistic regression analysis (early or late extubation as independent variable and relative risk factors obtained through univariate analysis as dependent
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variables). As shown in Table V, independent risk factors for late extubation included older age (>65 years) (odds ratio [OR] = 4.804; 95% confidence interval [CI], 2.351-12.376), duration of cardiopulmonary bypass (OR = 2.426; 95% CI, 1.395-7.256), perioperative IABP requirement (OR = 1.451; 95% CI, 1.125-3.783), preoperative arterial PO2 (OR = .204; 95% CI, .061-.758), and postoperative hemoglobin level (OR = .793; 95% CI, .337-.956).
DISCUSSION In addition to the length of ICU and hospital stay, late extubation correlated with negative respiratory outcomes in this study. Although there were no significant differences in the incidence of reintubation, apnea, hypoxemia, and pulmonary atelectasis between early and late extubation groups, longer ventilation support led to a higher incidence of pneumonia and respiratory failure. The fact that there were no significant differences in the incidence of reintubation and pulmonary atelectasis between early and late extubation groups could be related to the small ‘‘absolute value’’ (reintubation: 3 vs 5; pulmonary atelectasis: 10 vs 25), the latter probably resulting from the limited sample size. No
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Table III Comparison of risk factors between early and late extubation groups Factors
Preoperation Age > 65 y Female Recent smoking Diabetes mellitus Hypertension Dyslipidemia Renal dysfunction Diuretics Cerebrovascular disease COPD Recent MI Prior heart operation Prior unstable angina Congestive heart failure Triple vessel disease Left main trunk disease Left ventricular aneurysm Intra-operation Emergency surgery Use of CPB Use of ACC Postoperation (before extubation) Perioperative IABP requirement Reoperation for bleeding AMI ARF Stroke Atrial fibrillation Ventricular fibrillation
Early extubation (n = 128)
Late extubation (n = 288)
P value
38 (29.69%) 21 (16.41%) 28 (21.88%) 32 (25.00%) 101 (78.91%) 86 (67.19%) 2 (1.56%) 8 (6.25%) 45 (35.16%) 14 (10.94%) 14 (10.94%) 1 (.78%) 45 (35.16%) 61 (47.66%) 121 (94.53%) 41 (32.03%)
220 (76.39%) 60 (20.83%) 93 (32.29%) 87 (30.21%) 235 (81.60%) 178 (61.81%) 18 (6.25%) 36 (12.50%) 80 (27.78%) 56 (19.44%) 22 (7.64%) 2 (.69%) 115 (39.93%) 182 (63.19%) 280 (97.22%) 68 (23.61%)
<.0001 .3481 .0352 .2926 .5899 .3217 .0457 .0009 .1338 .0336 .2640 1.0000 .3835 .0036 .2519 .0904
10 (7.81%)
27 (9.38%)
.7106
3 (2.34%) 42 (32.81%) 35 (27.34%)
9 (3.13%) 146 (50.69%) 105 (36.46%)
.7624 .0009 .0731
2 (1.56%) 1 (.78%) 0 6 (4.69%) 1 (.78%) 31 (24.22%) 0
19 (6.60%) 14 (4.86%) 1 (.35%) 19 (6.60%) 2 (.69%) 113 (39.24%) 1 (.35%)
.0296 .0451 1.0000 .5112 1.0000 .0036 1.0000
AMI, acute myocardial infarction; IABP, intra-aortic balloon pump; COPD, chronic obstructive pulmonary disease; CPB, cardiopulmonary bypass; ACC, aortic cross clamping; ARF, acute renal failure; MI, myocardial infarction.
significant difference in the incidence of hypoxemia between early and late extubation groups could be related to the findings of our previous study,15 in which it was shown that intubation time was not an independent risk factor of postoperative hypoxemia after CABG. In addition, there were no significant differences in the incidence of low cardiac output and acute myocardial infarction between the 2 groups, which indicated that early extubation did not increase the incidence of low cardiac output and acute myocardial infarction. Improvement in cardiopulmonary performance, shorter ICU and hospital stays, and reduction in
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costs could be achieved when cardiac surgical patients were weaned from the mechanical ventilator at the appropriate time.2-4,7,8 On the other hand, prolonged ventilation support may have contributed to increased morbidity, mortality, and cost.16,17 Thus, early extubation was recommended. In this study, 288 patients were included in the late extubation group, with an incidence of 69.23%, which was higher than the 20% to 45% documented in the literature.2-4,7,8 Severity of illness measured by the EuroSCORE scale in this study (mean EuroSCORE was 4.87 1.79; 256 patients with a EuroSCORE of > 6, accounting for 61.54%, were included in
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Table IV Comparison of risk factors between early and late extubation groups Factor
Age (y) BMI (kg/m2) Preoperative Scr (mg/dL) Preoperative Hb (g/dL) Preoperative LVEF Preoperative LVEDD (mm) Preoperative PO2 (mm Hg) CPB (min) ACC (min) Operation time (min) Number of grafts Postoperative Hb (g/dL)
Early extubation (n = 128)
128 128 128 128 128 128 128 42 35 128 128 128
64.5 10.1 25.8 2.6 .86 .29 13.8 1.5 .55 .10 51.6 5.8 75.0 11.3 97.8 15.3 52.6 12.0 260.0 67.6 3.1 .7 8.5 1.7
Late extubation (n = 288)
288 288 288 288 288 288 288 146 105 288 288 288
68.3 8.0 26.2 2.3 .98 .28 13.6 1.6 .52 .09 53.0 9.6 72.0 8.6 118.2 23.0 68.8 48.8 266.1 78.6 3.2 .8 7.1 .9
t (or t’)
P
4.1412 1.5715 3.9901 1.6027 3.0307 1.5299 2.9704 5.3833 1.9469 .7663 .8581 11.0608
<.0001 .1168 <.0001 .1098 .0026 .1268 .0031 <.0001 .0536 .4439 .3913 <.0001
BMI, body mass index; Scr, serum creatinine; LVEF, left ventricular ejection fraction; LVEDD, left ventricular end-diastolic diameter; PO2, arterial partial pressure of oxygen; CPB, cardiopulmonary bypass; ACC, aortic crossclamping; Hb, hemoglobin.
Table V Multivariate regression results for independent risk factors Predictors
Age (>65 y) Duration of CPB Perioperative IABP requirement Preoperative PO2 Postoperative Hb
OR value
4.804 2.426 1.451 .204 .793
95% CI
2.351-12.376 1.395-7.256 1.125-3.783 .061-.758 .337-.956
P value
.007 .010 .045 .001 .014
CI, confidence interval; CPB, cardiopulmonary bypass; Hb, hemoglobin; IABP, intra-aortic balloon pump; OR, odds ratio; PO2, arterial partial pressure of oxygen.
a high-risk group), intraoperative and postoperative course, and preoperative, intraoperative, and postoperative factors may have independently or mutually contributed toward longer ventilation support after CABG. In addition, because of the learning curve in CABG and lack of experience, consensus of opinion on the timing of extubation after CABG has not been established in our country; thus, it was crucial for clinicians to evaluate the relative risk factors for late extubation after CABG so that the appropriate time for extubation could be found. In this study, the independent risk factors for late extubation after CABG were older age (>65 years), prolonged cardiopulmonary bypass, perioperative
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IABP requirement, low preoperative PO2, and low postoperative hemoglobin. Older age was one of the major risk factors contributing to late extubation after CABG. Patients aged more than 65 years who underwent CABG often had multiple concurrent diseases, poor cardiopulmonary reserve, and diffuse vascular sclerostenosis. They had a further reduction in their cardiopulmonary performance after CABG with or without cardiopulmonary bypass, and were more prone to postoperative low cardiac output and pulmonary complications, usually requiring longer ventilation support. In addition, age more than 65 years has been shown to be an independent risk factor of atrial
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fibrillation after CABG.18 Although atrial fibrillation is a relatively benign arrhythmia, persistent or frequent atrial fibrillation can seriously interfere with the hemodynamics, increase myocardial oxygen consumption, reduce cardiac output, and lead to longer ventilation support. Therefore, it is important to treat atrial fibrillation, especially after CABG, when patients are more vulnerable to the effects of atrial fibrillation. Prolonged cardiopulmonary bypass was also a major risk factor for late extubation after CABG. Cardiopulmonary bypass is associated with a systemic inflammatory response, the production of oxygenderived free radicals, the activation of polymorphonuclear neutrophils, and the complement cascade and release of vessel constringent factors.19-21 All these have negative influences on important organs, such as the heart, lung, brain, and kidney. Prolonged cardiopulmonary bypass was expected to negatively influence cardiopulmonary and renal functions, and thus requirement of longer ventilation support. In addition, prolonged cardiopulmonary bypass associated with complex disease, complicated operation, and imperfect myocardial protection may have led to longer ventilation support. Thus, further refinement of surgical techniques, decrease in cardiopulmonary bypass time, and performance of off-pump CABG can lead to early extubation. Low postoperative hemoglobin level seemed to be an independent risk factor for postoperative late extubation. Low postoperative hemoglobin level may have been related to poor oxygen transport. A lower hemoglobin level after surgery increases the potential for blood transfusion. This in turn may have resulted in a change in the pulmonary ventilation/blood flow ratio and induction of pulmonary capillary embolism, thus further affecting respiratory functions. Consequently, early extubation may not have been possible. Thus, meticulous intraoperative hemostasis is recommended. Perioperative IABP requirement suggested poor cardiac performance or even severe myocardial ischemia and unstable hemodynamics. After CABG, patients with IABP usually required adequate sedation and longer ventilation support to provide adequate oxygen supply and reduce respiratory workload and myocardial oxygen consumption. Low preoperative PO2 often suggested poor cardiopulmonary function or severe chronic obstructive pulmonary disease in patients. After CABG, further depression in cardiopulmonary function was expected in these patients who consequently were more prone to low cardiac output and postoperative respiratory failure, thus requiring longer
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ventilation support. Therefore, proper perioperative management of cardiopulmonary dysfunction in patients undergoing CABG may help shorten postoperative ventilation support. Many studies have shown that female gender was an independent risk factor for late extubation after CABG. However, there was no significant difference in the proportion of female to male patients between the late and early extubation groups (21/107 vs 60/ 228), which may be related to fewer female patients undergoing CABG in this study (only 19.47%). In addition, many studies showed that preoperative renal dysfunction was also an independent high risk factor for late extubation after CABG. Although the number of patients with preoperative renal dysfunction in the late extubation group was significantly higher than that in the early extubation group (6.25% vs 1.56%), through the logistic regression analysis, preoperative renal dysfunction was not found to be an independent risk factor for late extubation after CABG in this study. This could be due to the small ‘‘absolute value’’ (2 vs 18 patients) as a consequence of the limited sample size.
LIMITATIONS The retrospective nature and small sample size of this study were the main limitations of this study. Another limitation of this study was the lack of detailed respiratory function data. PO2 was measured preoperatively, but forced expiratory volume in 1 second and forced vital capacity were not routinely measured before CABG at Tongji Hospital.
CONCLUSIONS Elective early extubation was safe and did not increase postoperative morbidity. Older age, prolonged cardiopulmonary bypass, perioperative IABP requirement, low preoperative PO2, and low postoperative hemoglobin level were the 5 independent risk factors for late extubation after CABG. Early extubation may be achieved by reducing intraoperative and postoperative hemorrhage, thus maintaining a reasonable postoperative hemoglobin level and shortening the cardiopulmonary bypass time. The proper perioperative management of cardiopulmonary dysfunction in older patients may contribute toward reducing postoperative ventilation support and facilitate early extubation. REFERENCES 1. Klineberg PL, Geer RT, Hirsh RA, Aukburg SJ. Early extubation after coronary artery bypass graft surgery. Crit Care Med 1977; 5:272-4.
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Late extubation after CABG 2. Hawkes CA, Dhileepan S, Foxcroft D. Early extubation for adult cardiac surgical patients. Cochrane Database Syst Rev 2003;(4). CD003587. 3. Reis J, Mota JC, Ponce P, Costa-Pereira A, Guerreiro M. Early extubation does not increase complication rates after coronary artery bypass graft surgery with cardiopulmonary bypass. Eur J Cardiothorac Surg 2002;21:1026-30. 4. Rashid A, Sattar KA, Dar MI, Khan AB. Analyzing the outcome of early versus prolonged extubation following cardiac surgery. Ann Thorac Cardiovasc Surg 2008;14:218-23. 5. Weissman C. Pulmonary complications after cardiac surgery. Semin Cardiothorac Vasc Anesth 2004;8:185-211. 6. Verrier ED, Wright IH, Cochran RP, Spiess BD. Changes in cardiovascular surgical approaches to achieve early extubation. J Cardiothorac Vasc Anesth 1995;9:10-5. 7. Wong DT, Cheng DC, Kustra R, Tibshirani R, Karski J, CarrollMunro J, et al. Risk factors of delayed extubation, prolonged length of stay in the intensive care unit, and mortality in patients undergoing coronary artery bypass graft with fast-track cardiac anesthesia: a new cardiac risk score. Anesthesiology 1999;91:936-44. 8. Silbert BS, Santamaria JD, O’Brien JL, Blyth CM, Kelly WJ, Molnar RR. Early extubation following coronary artery bypass surgery: a prospective randomized controlled trial. The Fast Track Cardiac Care Team. Chest 1998;113:1481-8. 9. Nashef SA, Roques F, Michel P, Gauducheau E, Lemeshow S, Salamon R. European system for cardiac operative risk evaluation (EuroSCORE). Eur J Cardiothorac Surg 1999;16:9-13. 10. Amram JC, Michael GK, George F, Benjamin M, Diklah G, Arie S. Morbid results of prolonged intubation after coronary artery bypass surgery. Chest 2000;118:1724-31. 11. Dumas A, Dupuis GH, Searle N, Cartier R. Early versus late extubation after coronary artery bypass grafting: effects on cognitive function. J Cardiothorac Vasc Anesth 1999;13: 130-5.
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Ji et al 12. Lee JH, Graber R, Popple CG, Furey E, Lyons T, Murrell HK, et al. Safety and efficacy of early extubation of elderly coronary artery bypass surgery patients. J Cardiothorac Vasc Anesth 1998;12:381-4. 13. Filsoufi F, Rahmanian PB, Castillo JG, Mechanick JI, Sharma SK, Adams DH. Diabetes is not a risk factor for hospital mortality following contemporary coronary artery bypass grafting. Interact Cardiovasc Thorac Surg 2007;6:753-8. 14. Antunes PE, Prieto D, Ferra˜o de Oliveira J, Antunes MJ. Renal dysfunction after myocardial revascularization. Eur J Cardiothorac Surg 2004;25:597-604. 15. Ji Q, Mei Y, Wang X, Feng J, Cai J, Sun Y, et al. Study on the risk factors of postoperative hypoxemia in patients undergoing coronary artery bypass grafting. Circ J 2008;72:1975-80. 16. Pappalardo F, Franco A, Landoni G, Cardano P, Zangrillo A, Alfieri O. Long-term outcome and quality of life of patients requiring prolonged mechanical ventilation after cardiac surgery. Eur J Cardiothorac Surg 2004;25:548-52. 17. Serrano N, Garcı´a C, Villegas J, Huidobro S, Henry CC, Santacreu R, et al. Epidemiological Project for ICU Research and Evaluation (EPICURE). Prolonged intubation rates after coronary artery bypass surgery and ICU risk stratification score. Chest 2005;128:595-601. 18. Mamoun NF, Xu M, Sessler DI, Sabik JF, Bashour CA. Propensity matched comparison of outcomes in older and younger patients after coronary artery bypass graft surgery. Ann Thorac Surg 2008;85:1974-9. 19. Lagan AL, Melley DD, Evans TW, Quinlan GJ. Pathogenesis of the systemic inflammatory syndrome and acute lung injury: role of iron mobilization and decompartmentalization. Am J Physiol Lung Cell Mol Physiol 2008;294:L161-74. 20. Hess PJ Jr. Systemic inflammatory response to coronary artery bypass graft surgery. Am J Health Syst Pharm 2005;62:S6-9. 21. Levy JH, Tanaka KA. Inflammatory response to cardiopulmonary bypass. Ann Thorac Surg 2003;75:S715-20.
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