Asian Cardiovasc Thorac Ann 2006;14:195-199
© 2006 Asia Publishing EXchange Ltd
Optimizing Early Extubation after Coronary Surgery
Georgios P Georghiou, MD,
Alon Stamler, MD,
Eldad Erez, MD,
Ehud Raanani, MD,
Bernardo A Vidne, MD,
Alexander Kogan, MD
Department of Cardiothoracic Surgery, Rabin Medical Center, Tel Aviv University, Tel Aviv, Israel
For reprint information contact: Georgios P Georghiou, MD Tel: 357 22 819 666 Fax: 357 22 819 667 Email: georgios{at}ahi.com.cy, Department of Cardiothoracic Surgery, American Heart Institute, 20 Lefkotheou Avenue, Nicosia 2054, Cyprus.
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ABSTRACT
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Early extubation after isolated coronary artery bypass surgery was assessed retrospectively in 545 of 779 patients treated by the same surgical team over one year. All underwent extubation within 10 hr of arrival at the cardiothoracic intensive care unit: 343 in < 6 hr and 202 in 6–10 hr. Operative mortality was 2.2%. Group comparisons revealed that patients who had earlier extubation were younger (61 vs. 66 years; p < 0.001), more likely to be male (72.5% vs. 61.3%; p < 0.05), with a shorter aortic crossclamp time (49.2 ± 15.0 vs. 53.3 ± 14.0 min; p < 0.05), cardiopulmonary bypass time (65 ± 18.4 vs. 72.2 ± 19.2 min; p < 0.05), intensive care unit stay (18.8 ± 5.6 vs. 22.4 ± 3.2 hr; p < 0.05) and postoperative hospital stay (5.2 ± 2.2 vs. 6.0 ± 2.4 days; p = 0.01). Extubation < 6 hr after cardiopulmonary bypass may accelerate recovery. The finding of no significant differences in clinical parameters between the groups suggests that efforts to further reduce the time to extubation might be worthwhile.
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INTRODUCTION
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Overnight sedation and ventilation of patients after cardiac surgery has been standard practice for decades. However, recent improvements in perfusion techniques and the use of inhalation-based anesthesia have made it possible to remove the tracheal tube within hours after cardiopulmonary bypass (CPB) in selected patients, with rapid stepdown from the cardiothoracic intensive care unit (ICU).1–4 Today, these fast-track protocols have become popular in many major centers, although the precise timing of early extubation is still unclear. Arom and colleagues1 advocated tracheal tube removal within 12 hr of arrival in the cardiothoracic ICU, whereas Reyes and colleagues5 limited it to 7–11 hr, and Higgins2 to 3–10 hr. Prakash and colleagues6 defined early extubation as tracheal tube removal within 3 hr of surgery. The aim of this study was to determine if early extubation could be accelerated to < 6 hr after arrival at the cardiothoracic ICU. We evaluated the demographic and intraoperative parameters associated with shorter extubation time and its impact on length of ICU and hospital stay.
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PATIENTS AND METHODS
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The cardiothoracic ICU in our tertiary-care university-affiliated center is a 12-bed unit run by a full-time intensivist; the patient-to-staff ratio is 2:1. Fast-track management has been part of the standard care policy at our institute for the past 5 years. Between September 2001 and August 2002, 779 patients underwent first-time isolated coronary artery bypass grafting (CABG) including urgent, emergency, and catheterization salvage procedures at our center. All were operated on by the same group of surgeons. In 545 patients (70%), extubation was performed within 10 hr of ICU admission. On arrival in the ICU, patients were targeted for fast-track management, defined as early extubation enabling discharge from the ICU on the 1st postoperative day. Exclusion criteria were the requirement for intraaortic balloon pump support, poor general condition, severe hemodynamic instability requiring increasing doses of cardioactive drugs, and anticipated need for prolonged respiratory support (severe chronic obstructive pulmonary disease, requirement for fractional concentration of inspired oxygen > 0.6, and high positive end-expiratory pressure). Patients in whom the tracheal tube was removed in less than 6 hr of arrival at the ICU (n = 343) were compared with those in whom the tube was removed at 6–10 hr (n = 202). As this was a retrospective review, institutional ethics committee approval was not required.
The anesthetic technique was geared toward facilitating early extubation, irrespective of preoperative comorbid conditions. Premedication consisted of midazolam syrup 0.1 mg·kg–1, and anesthesia was induced with fentanyl 10–15 µg·kg–1 and midazolam 0.02–0.04 mg·kg–1. Pancuronium bromide was given to facilitate tracheal intubation. The lungs were ventilated with an oxygenating mixture to maintain normocapnia. Anesthesia was maintained with isoflurane, fentanyl, and midazolam. The total dose of fentanyl was 20–35 µg·kg–1, and that of midazolam, 0.15–0.2 mg·kg–1. Surgery was performed via a median sternotomy using standard CPB techniques with moderate hemodilution (hematocrit, 21%–27%). Cardiopulmonary bypass was instituted with an ascending aortic cannula and a two-stage venous cannula. Mild (32°C) to moderate (28°C) core hypothermia was used. Myocardial protection was achieved with antegrade and/or retrograde delivery of tepid blood or crystalloid cardioplegic solution. In patients with ongoing ischemia, an initial induction dose of warm cardioplegic solution was administered. All patients were rewarmed to 37°C before discontinuation of CPB. After completion of surgery, patients were moved to the cardiothoracic ICU while still intubated.
On arrival at the cardiothoracic ICU, the lungs were ventilated mechanically in the assist-control mode, and the patients were given cardioactive drugs as indicated. Warm-air heaters were used to maintain normothermia. Analgesia consisted of intravenous morphine boluses, as required. The criteria for weaning from the ventilator were hemodynamic stability (no or decreasing use of cardioactive drugs), absence of significant bleeding (< 100 mL·h–1), no significant arrhythmias, adequate urine output (> 1 mL·kg–1·h–1), and oxygen saturation > 95% with fraction of inspired oxygen < 0.50; the patient also needed to be sufficiently awake to follow commands. Patients were placed on ventilation for 20–30 min and in the absence of respiratory or cardiac distress, extubation was performed immediately thereafter by a specially trained nurse. The ventilation was synchronized intermittent mandatory ventilation with pressure support and positive end-expiratory pressure. The tidal volume was 8–10 mL·kg–1, rate 10–15 per min, pressure support 20 cm H2O, positive end-expiratory pressure 5–10 cm H2O, and the fraction of inspired oxygen was 0.6–1.0. After extubation, close monitoring was continued as before. As there is no intermediate-care facility at our hospital, patients were discharged from the cardiothoracic ICU to the adjacent cardiothoracic ward on the 1st day after arrival. During this period, any increase in the requirement for cardioactive drugs or a significant decrease in oxygen saturation (< 90% despite oxygen mask), urine output, or level of consciousness was considered a contraindication to discharge.
All data were collected on standardized forms and entered into a computerized database. Values are expressed as means and standard deviations, or as percentages. Differences in clinical and operative parameters between the two groups were evaluated for statistical significance with Student’s t test; confidence intervals were used to express the difference between means. A p value of less than 0.05 was considered statistically significant.
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RESULTS
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Clinical and catheterization data, and the Bernstein-Parsonnet risk estimates are shown in Table 1
.7 Compared with patients extubated within 6–10 hr, those extubated before 6 hr were younger and comprised a higher proportion of men. There was no significant difference between the groups in the prevalence of diabetes mellitus, chronic obstructive pulmonary disease, peripheral vascular disease, hypertension, congestive heart failure, cerebrovascular disease, or chronic renal failure, nor was there any difference in the incidence of unstable angina or recent myocardial infarction. Both groups had a similar preoperative ejection fraction, degree of left main coronary disease, and incidence of cardiogenic shock. Neither had significant comorbidity, reflected in the low preoperative risk stratification scores. The intraoperative details are listed in Table 2. The left internal mammary was used in all patients. The mean number of grafts per patient was similar in both groups. Crossclamp and CPB times were significantly shorter in the patients extubated in less than 6 hr. The overall surgical mortality rate for all 779 patients operated on in our unit during the study period was 2.2% (17/779); none of the deaths occurred in the patients extubated before 10 hr. The postoperative outcome is shown in Table 3. The overall reintubation rate was < 1%. There was no difference in the frequency of atrial fibrillation between the groups. The length of cardiothoracic ICU stay was shorter in the group extubated earlier, and a higher percentage of patients who underwent earlier extubation were discharged from the hospital in 5 days or less. This group also had a significantly shorter overall postoperative length of stay.
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DISCUSSION
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Intensive care management following cardiac surgery has traditionally included prolonged elective ventilation. However, this practice, compounded by prolonged sedation, leads to a delay in the return of the patient to a regular ward, and perhaps to prolonged recovery. No benefit has been found for prolonged ventilation following CABG in low-risk patients.8 At the same time, there is also no benefit in extubation in the operating room.9 Recent series support a brief period of postoperative ventilation in the cardiothoracic ICU.9
To control the cost of CABG, most centers have replaced high-dose narcotic agents with inhalation agents for anesthesia, and introduced cell-saving techniques to lower transfusion requirements and weight gain.8 In addition, the application of heparin-bonded circuits using low-dose heparin has minimized fluid gain and transfusion requirements, thereby decreasing the incidence of ischemic events.10 These modifications have led to the adoption of fast-track postoperative protocols and critical steps to reduce ICU and hospital stays. Although several studies emphasize the advantages of high-dose narcotic anesthesia and prolonged mechanical ventilation after CPB to improve patient stability relative to the new ischemic events induced by anesthesia, and to decrease the myocardial work associated with mechanical ventilation, there are equally compelling reasons for early extubation.11–14 Positive-pressure ventilation has negative circulatory effects. For example, positive end-expiratory pressure has a corollary of decreased cardiac output accompanied by a reduction in myocardial and renal perfusion.4 The presence of the tracheal tube itself promotes pulmonary complications, such as loss of mucus transport, which in turn contribute to lobar collapse and tracheal complications such as granuloma formation.4 In addition, the inability to communicate while intubated tends to increase patient anxiety, which can only have adverse effects, while rapid mobilization and rehabilitation improves individual patient recovery and assists the patient turnover rate necessary for a successful open-heart program.15
Early extubation, an integral part of the CPB fast-track recovery process, depends on adequate patient physiologic reserve together with optimized postoperative cardiothoracic ICU care. However, the timing of early extubation varies among reports, and a precise definition has not been established. In this study, we defined early extubation as within 10 hr of ICU admission. Our findings show that even earlier extubation (< 6 hr) may be feasible and safe. Variables shown in other studies to increase intubation time include older age, female sex, unstable angina, hemodynamic instability, abnormal temperature, renal insufficiency, use of preoperative diuretics, postoperative intraaortic balloon counterpulsation, banked blood transfusion, and longer duration of CPB.16–18 In agreement with these studies, our analysis showed that patients in the earlier extubation group were younger and more of them were male; however, there were no differences between the groups in any of clinical or disease-related parameters. Intraoperative parameters seem to play an important role, with patients in the earlier extubation group showing a significantly shorter CPB and aortic crossclamp times. Those who underwent earlier extubation also had decreased ICU and hospital lengths of stay. The improved postoperative course of the patients with earlier extubation, combined with the similarities between the groups in all disease-related parameters before surgery, indicates that extubation within 6 hr of arrival at the cardiothoracic ICU is both feasible and safe. Further efforts to reduce postoperative extubation time in CABG patients may yield clinical, and consequently, economic benefits, especially in younger patients with a favorable intraoperative course.
That even earlier extubation (< 6 hr) was successfully achieved with a good outcome in the majority of patients in this series, supports the hypothesis that there should be no arbitrary time limit for postoperative extubation. Indeed, we believe a specific, predefined time limit for extubation following CABG is impractical, and that adequate patient physiologic reserve together with optimized postoperative cardiothoracic ICU care should be the factors that determine the timing of early extubation. In our institution, patients are extubated when they meet standard criteria: when they are awake, warm, not bleeding significantly, and hemodynamically stable, and when they have adequate oxygenation and ventilation. We suggest that early extubation should be an integral part of the CABG fast-track recovery process, although final conclusions regarding its safety and efficacy await prospective trials.
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ABSTRACT
INTRODUCTION
