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Ann Thorac Surg 2000;70:2008-2012
© 2000 The Society of Thoracic Surgeons

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Original article: cardiovascular

Rapid recovery protocol applied to 5,658 consecutive "on-pump" coronary bypass patients

^a Oslo Heart Center, Oslo, Norway

Accepted for publication May 4, 2000.

Address reprint requests to Dr Øvrum, Oslo Heart Center, 32, P O Box 2684 St. Hanshaugen, 0131 Oslo, Norway
e-mail: eivind.ovrum{at}hjertesentevet.no

	Abstract

Top Abstract Introduction Material and methods Results Comment Acknowledgments References

 
Background. Increasing hospital costs, restricted resources, and new surgical strategies have stimulated effectiveness of all routines in cardiac surgery. Over a 10-year period, 5,658 consecutive patients undergoing coronary artery bypass grafting followed a protocol aiming at short postoperative intubation times and rapid physical rehabilitation.

Methods. The patients were prepared for rapid recovery, emphasizing (1) preoperative education and respiratory training, (2) low-dose fentanyl anesthesia, (3) limited ischemic times and pump times, (4) mild hypothermia and rewarming to a rectal temperature of 36°C, (5) restricted use of extended monitoring, (6) autologous blood salvage to avoid allogeneic blood transfusions, and (7) active physical training from postoperative day 1. All in-hospital data relevant to these steps were prospectively stored in a database.

Results. The median extubation time after arrival in the intensive care unit was 1.5 hours (0 to 320 hours). More than 99% of the patients were extubated within 5 hours. Sixty-two patients (1.1%) were reintubated and ventilated for a median of 24 hours (1 to 430 hours), mostly due to resternotomy for bleeding or cardiopulmonary decompensation. In total, 5,594 patients (98.9%) were able to sit in a chair the first postoperative day. Within the fourth postoperative day, 82.5% were able to move freely in the hospital area and were in fact physically fit for hospital discharge. Allogeneic blood products were given to 3.9% of the patients. Twenty-three patients (0.41%) died in-hospital.

Conclusions. With the application of a protocol for rapid physical recovery in patients undergoing "on-pump" coronary artery bypass grafting, extubation within 1 to 2 hours was safe and feasible in most patients. After 5 hours, 99.3% of the patients were extubated, with a reintubation rate of 1.1%. More than 80% of the patients were fully physically mobile within 4 days after the operation.

	Introduction

Top Abstract Introduction Material and methods Results Comment Acknowledgments References

 
The development of less invasive methods for myocardial revascularization, like "off-pump" cardiac surgery [1, 2], has renewed the interest for faster recovery after conventional coronary artery bypass grafting using cardiopulmonary bypass (CPB) and cardiac arrest [3, 4]. This interest is not only driven by the wish to compare or to promote different surgical strategies, but reflects the concern of hospital costs associated with all types of cardiac surgery. Still a large proportion of coronary patients has to be operated "on-pump" to achieve complete revascularization, and for many types of cardiac operations CPB will remain inevitable, such as in valve operations and corrections of congenital defects.

Early extubation after operation is a main step for rapid postoperative recovery and may reduce the need for conventional intensive care to a small number of patients [5]. This approach of fast-track recovery has been shown to be safe, feasible, and cost effective by reducing length of hospital stay [6–8]. At start-up of our institution in 1989, we introduced a standard protocol for all patients undergoing coronary artery bypass grafting, aiming at short postoperative intubation times and early physical training. Simultaneously, all routines were simplified, avoiding unnecessary use of chest roentgenograms, laboratory tests, and extended monitoring like pulmonary artery catheter measurements. The operative procedures were performed with CPB and cardioplegic arrest and the goal was to obtain complete myocardial revascularization within short ischemic times and pump times. The present report describes our initial 10 years of experience with this strategy.

	Material and methods

Top Abstract Introduction Material and methods Results Comment Acknowledgments References

 
Patients
From 1989 through 1998, 5,658 consecutive patients underwent myocardial revascularization with CPB and cardioplegic arrest in our department. The majority of the patients underwent operation on elective basis, and 102 cases (1.8%) were redo operations. Some patient categories were taken care of by a neighboring university department, such as patients with severe renal dysfunction, patients in need of a combined carotid and coronary operation, left ventricular aneurysm procedures, and true emergencies like failed angioplasties. Consequently, the patient population is somewhat selected, which has to be taken into consideration when evaluating the results. Otherwise, a typical coronary artery bypass patient population was treated (Table 1).

Operation
Standard operative procedures included median sternotomy, preparing of the internal mammary artery, and CPB with a two-stage cannula in the right atrium and one cannula in the ascending aorta. Aorta was cross-clamped and either crystalloid cardioplegic solution or cold blood cardioplegia was infused in the antegrade fashion before performing the distal anastomoses. In some instances of critical left main stenosis retrograde infusion of cardioplegia was performed. Vein grafts were attached to the ascending aorta using partial occlusion while rewarming the patient. More than two-thirds of the patients were operated by one of two surgeons (EØ, GT). The number of consulting physicians were limited and all procedures were uniformly performed during the entire period under investigation.

The CPB was performed using pulsatile flow at a rate of 2.4 L/m² per minute and mild hypothermia (blood temperature, 32°C to 34°C) was instituted immediately after the start of bypass. The patients were weaned off CPB at a rectal temperature of 36°C, which was aimed to reach before completing the last proximal anastomosis.

Anesthesia
The anesthesia protocol was designed to permit early extubation and included a combination of diazepam (0 to 0.2 mg/kg), midazolam hydrochloride (0 to 0.2 mg/kg), low-dose fentanyl (4 to 8 µg/kg), and pancuronium bromide, supplemented with isoflurane and nitrous oxide. An arterial and central venous line was the standard. Extended monitoring with pulmonary catheters was rarely used and was mostly restricted to cases of postoperative cardiopulmonary decompensation. No transesophageal echocardiograms were done. About half of the patients were treated by one of two anesthesiologists (EH, SD).

Before extubation, the patients were often ventilated with some pressure support. Otherwise, the following criteria for extubation were used:

1. The patient should be awake and responsive;
   
2. Satisfactory blood gases (arterial oxygen tension >9 KPa [on fractional concentration of oxygen = 0.4], partial pressure of carbon dioxide less than 7 KPa);
   
3. Adequate spontaneous ventilation based on clinical observation;
   
4. Stable circulation with little or no inotropic drugs;
   
5. Mediastinal drainage less than 200 ml per hour.
   

If not particularly indicated, no chest roentgenograms were performed the day of operation.

Blood salvage
All patients, without exclusions, underwent a blood conservation protocol, previously described in detail [9]. The main steps included removal of autologous blood before bypass for retransfusion after bypass (if adequate preoperative hemoglobin concentration), intra- and postoperative retransfusion of the oxygenator and circuit contents (without cell processing), and postoperative autotransfusion of shed mediastinal blood up to 18 hours postoperatively. If possible, platelet inhibitors like aspirin were discontinued 7 days preoperatively. Normovolemic anemia was accepted to a hematocrit of 25%, which represented a level of consideration for allogeneic red cell transfusion.

	Results

Top Abstract Introduction Material and methods Results Comment Acknowledgments References

 
Patients
The demographic data are listed in Table 1. Most patients were in New York Heart Association functional class III and 5.8% of the patients were in class IV. More than 90% of the operations were performed electively.

Operation
At least one internal mammary artery was used in 5,612 patients (99.2%). The median number of distal anastomoses was four (one to nine). The median aortic cross-clamping time was 32 minutes (5 to 142 minutes) and the median extracorporeal circulation time was 55 minutes (14 to 240 minutes). The median wean-off rectal temperature was 36.4°C (34.0° to 38.9°C). One hundred fifty-four (2.7%) patients were reexplored for postoperative bleeding.

Postoperative course
The rectal temperature at ICU arrival was median 36.7°C (34.7° to 38.9°C). The patients were weaned from ventilator at a median of 1.5 hours (0 to 320 hours) postoperatively (Table 2). Within 5 hours, 99.3% of the patients were extubated and only 4 patients were primarily ventilated more than 24 hours. However, 61 patients (1.09%) were reintubated for a median 24 hours (1 to 430 hours), mostly due to resternotomy for bleeding (35 patients, 0.62%) or cardiopulmonary decompensation (26 patients, 0.46%).

Every day the physiotherapists monitored the progress of physical rehabilitation and the data are displayed in Table 3. The number of fully mobile patients (climbing stairs or walking outdoors) increased from 4,660 (82.4%) on the forth day to 5,442 (96.2%) within the seventh postoperative day. Due to tradition, most patients were discharged to their local hospitals for follow-up and eventual readmissions could not be registered in our database. However, all cases of deep infections were readmitted to our institution.

Subgroups
Redo operations
Due to the short history of our department (established in 1989), the number of redo operations was modest. One hundred two patients (1.8%) underwent their second or third myocardial revascularization. In the 100 survivors, the intubation time was similar to the total population, median 1.6 hours (0.3 to 5.2 hours) and within the seventh postoperative day, 96.1% of the patients were fully mobile.

Older age
In the patient group of more than 65 years of age (n = 2,211) the median intubation time was 1.8 hours (0 to 250 hours). Within the seventh postoperative day 93.6% of the patients were fully mobile. In patients younger than 66 years (n = 3,447), the intubation time was 1.3 hours (0 to 312 hours) and the 7-day recovery rate was 98.1%.

Perioperative myocardial infarction
The incidence of perioperative Q-wave myocardial infarction was 2.53% (143 patients). This subgroup was treated in a similar manner to the total population and median intubation time was 1.6 hours (0 to 312 hours). Most of the patients were asymptomatic and only 12.6% received any inotropic therapy. Of the 134 survivors, 82.8% of the patients were able to walk freely indoors on the third postoperative day, and 90.3% were fully mobile within the seventh postoperative day.

	Comment

Top Abstract Introduction Material and methods Results Comment Acknowledgments References

 
Restricted resources and increasing hospital costs have stimulated the interest to perform conventional cardiac surgery more effectively [3–6]. Although most cardiac centers experience an overall trend toward a higher operative risk [10], several researchers have succeeded in doing perioperative procedures more cost effectively [4, 5, 7]. Also, various new techniques for minimally invasive or "off-pump" cardiac operations, which claim to be less costly relating to the length of ICU stay and hospital stay [1, 2], have inspired more cardiac surgical units to improve their routines in conventional cardiac surgery. The health system would certainly favor this approach; however, the primary goal is the patient’s rapid and uneventful long-term recovery.

Early tracheal extubation is an important step for fast postoperative rehabilitation and may reduce the need for conventional intensive care to a small number of patients [5]. Early extubation improves postextubation intrapulmonary shunt fraction [11] and may avoid oversedation and the resultant depression of the respiratory center, which prolongs ICU stay. Concerns have been raised regarding postoperative myocardial ischemia following early spontaneous ventilation after operation [12]. However, Cheng and associates [11] could not find any differences in myocardial ischemia episodes or myocardial infarction in a prospective, randomized study comparing early and late tracheal extubation. Our setup do not include continuous monitoring of myocardial ischemia, but the low incidence of reintubation due to cardiorespiratory decompensation (0.46%) and the acceptable complication rate of postoperative myocardial infarction (2.53%), as well as hospital mortality (0.41%), confirm the feasibility and safety of early tracheal extubation. This experience is probably, at least partly, due to some selection of the patient population. However, Calafiore and associates [13] recently reported on their experience with a series of low-risk patients undergoing off-pump left internal mammary artery grafting to the left anterior descending artery through a left anterior small thoracotomy. They were able to extubate 71.2% of the patients within 2 hours postoperatively. In the present series, 75.1% of the patients were extubated within 2 hours after the operation, including all categories of patients who underwent multivessel on-pump coronary bypass grafting. The same protocol was applied to both patients who had redo operations and those sustaining a perioperative myocardial infarction, with similar results regarding length of ventilatory support and physical recovery. For patients older than 70 years, 75.0% of the patients were extubated within 2.5 hours postoperatively.

To facilitate early extubation, the choice of anesthetic technique appears to be important. Anesthesia based on moderate doses of narcotics and inhalation anesthetic agents are more appropriate than high-dose narcotic anesthesia for early extubation protocols [14]. Restrictive use of opiates for postoperative pain management and the use of nonsteroidal antiinflammatory drugs have proved satisfactory in our practice.

Habib and associates [15] suggested that early extubation may be achieved by actively reducing fluid retention after cardiopulmonary bypass. This is in contrast to our experience. For the last 3,787 patients, more extensive data concerning fluid balance have been collected, and the fluid overload on arrival at the ICU was a mean of 3,111 ± 708 mL. The total diuresis until the following morning was a mean of 1,619 ± 536 mL and diuretic drugs were given to only 27.1% of the patients. Nevertheless, the median intubation time was 1.5 hours. A moderate fluid overload is apparently well tolerated in most patients with normal kidney function. The hemodynamic situation is kept stable, with less need for fluid infusions, which in turn may worsen the blood gases and lead to delayed extubation and increased sedation.

The same investigators [15] also suggested that time on cardiopulmonary bypass was a determinant for prolonged mechanical ventilation after coronary artery bypass grafting. The side effects of CPB are well known [16], as the extracorporeal circuits expose blood to shear stresses and to contact with large areas of synthetic, nonendothelial surfaces. This results in mechanical damage to blood components and activation of biological cascades, which may contribute to the development of a generalized inflammatory response and organ dysfunction [17]. We have shown that the deleterious effects of CPB increase with time, both for blood cells, the coagulation and fibrinolytic systems, and for complement activation [18, 19]. Therefore, it might be suggested that shortening the time on bypass may diminish the damaging effects on organ functions, particularly the brain, the kidneys, and the lungs. As for the ischemic time, we were able to show in a multivariate study that the duration of ischemic time is an independent risk factor for development of postoperative myocardial infarction, starting relatively early after aortic cross-clamping [20]. Therefore, efforts should be made to plan the surgical procedures with the goal to reduce the ischemic and pump time to a minimum. However, this should certainly not compromise the aim of complete revascularization.

The rewarming of the patient to normal body temperature at the end of bypass reduces postoperative shivering and subsequent increased oxygen consumption. Also the blood pressure is easier to control in a normothermic patient and both make it more often possible to wean off ventilator soon after admission to the ICU. Furthermore, extended cardiopulmonary monitoring like pulmonary artery catheters were very rarely used. In a hemodynamically stable patient, there is no benefit compared with ordinary central venous pressure lines and may even be associated with greater weight gain and longer intubation [21].

Transfusion of allogeneic blood and blood products carry several complications [22], which may delay physical rehabilitation. A simple autotransfusion policy did restrict the use of bank blood to less than 4% of our patients and we suggest that the absence of transfusion-related morbidity may be a significant factor for an uneventful recovery after cardiac operation.

As previously shown by other researchers [5, 6], the present patient series indicate that conventional coronary artery bypass grafting using CPB does not necessarily require complicated and costly resources. Indeed, the majority of the patients were no real candidates for ICU facilities after 3 to 4 hours. On the other hand, more precise variables are needed to evaluate the clinical effects of fast-tracking recovery protocols. A short length of stay in the ICU and in the hospital is often used as a criteria for treatment success. However, such data are of little value, at least in European countries where Social Security covers most hospital costs. In these environments, there are traditions to keep the patients in hospital to fulfill both the demands for medical, social, and emotional well-being. Collection of detailed data, including a daily status of the physical capacity for each individual until hospital discharge, would obviously make the evaluation of the medical progress of the patients more accurate.

Implementation of a program for early recovery requires a close cooperation and communication between all the departments in a cardiac surgical unit, which include the surgeons, the anesthetists, the physiotherapists, and the nurses. With the application of a common philosophy for all steps during and after operation, extubation within 1 to 2 hours was attainable and safe in the majority of patients undergoing coronary artery bypass grafting with extracorporeal circulation. More than 80% of the patients in this series were medically ready for hospital discharge within 4 days after the operation.

	Acknowledgments

Top Abstract Introduction Material and methods Results Comment Acknowledgments References

 
We express our gratitude to our former chief anesthetist, Dr Einfrid m Holen, for initiating parts of the recovery protocol, and to Rolf Øystese, CCP, and Reidar Istad, CCP, for computer storing of data.

	References

Top Abstract Introduction Material and methods Results Comment Acknowledgments References

 

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