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CARDIOVASCULAR ANESTHESIA

The Lack of Benefit of Tracheal Extubation in the Operating Room After Coronary Artery Bypass Surgery

Department of Anesthesia, Fundación Cardio Infantil–Instituto de Cardiologia, Santafé de Bogotá, Colombia, South America

Address correspondence and reprint requests to Félix R. Montes, MD, Apartado Aéreo 104006, Santafé de Bogotá, Colombia, South América. Address e-mail to cfmont{at}col1.telecom.com.co

	Abstract

Top Abstract Introduction Methods Results Discussion Appendix 1. Tracheal Extubation... Appendix 2. Discharge Criteria References

 
Although early tracheal extubation in cardiac anesthesia is safe and cost beneficial, questions still remain regarding how early after cardiac surgery patients should be tracheally extubated (TE). Our objective was to determine the effects on resource use if patients scheduled for coronary artery bypass grafting have TE in the operating room (OR). We studied 100 consecutive patients undergoing elective coronary artery bypass grafting, requiring extracorporeal circulation, and those eligible for a fast-track pathway. At the end of the procedure, the patients were evaluated for TE in the OR if they were hemodynamically stable, were without significant bleeding, and fulfilled clinical and blood gas analysis variables. Patients who did not meet the requirements had TE in the intensive care unit (ICU). Fifty patients had TE in the OR and 50 patients in the ICU. Time in the OR after skin closure, ICU length of stay, and postoperative length of stay were similar between the groups. Four patients (8%) in the OR group were tracheally reintubated secondary to respiratory depression (P = 0.11). Three patients (6%) in the OR group had postoperative myocardial infarction, and one postoperative myocardial infarction (2%) occurred in the ICU group (P = 0.61). All four patients recovered satisfactorily. The incidences of other complications were similar between groups.

Implications: Tracheal extubation in the operating room after uncomplicated coronary artery bypass grafting is not associated with significantly decreased intensive care unit and postoperative length of stay. This practice is, however, associated with a moderate risk of reintubation.

	Introduction

Top Abstract Introduction Methods Results Discussion Appendix 1. Tracheal Extubation... Appendix 2. Discharge Criteria References

 
Recent changes in health care have focused attention on cost. This attention has motivated clinicians and hospital administrators to develop and implement strategies to contain or reduce costs, particularly in high-cost areas such as cardiac surgery. One popular strategy known as the fast-track cardiac surgery pathway, uses modified anesthetic management that facilitates early tracheal extubation (TE) (1).

Although there is no official definition of early TE after coronary artery bypass grafting (CABG), many clinicians would define this as TE during the first 1 to 6 h after surgery (2). Although several studies have confirmed that early TE is safe and cost beneficial (3–8), questions remain regarding how early cardiac surgery patients should have TE. The continuous improvements in surgical, anesthetic, and perfusion techniques allow TE of selected patients directly in the operating room (OR), and some groups have used this approach during the last years without significant morbidity (9,10). However, some authors believe that the risk of hypothermia, bleeding, and cardiorespiratory instability outweigh the potential benefit of this practice and, therefore, do not recommend it (6,11).

The objective of this study was to perform a controlled, nonrandomized, and prospective comparison between patients having TE in the OR versus patients having TE early in the intensive care unit (ICU) to determine whether this practice was beneficial without compromising patient care.

	Methods

Top Abstract Introduction Methods Results Discussion Appendix 1. Tracheal Extubation... Appendix 2. Discharge Criteria References

 
After we obtained approval of the institutional ethics committee and informed consent of the involved patients, we studied 100 consecutive patients of either sex, undergoing elective CABG, requiring extracorporeal circulation, and eligible for a fast-track cardiac surgery pathway. The sample size for this study was based on previous statistics of our institution. In our unit, the average ICU stay (LOS) was 2.5 ± 1.7 days. We considered a decreased ICU LOS of one day (40%) an important goal. These data suggested that a power of 95% for detecting a 40% difference in ICU LOS at an level of 0.05 would be obtained with 46 patients in each group. Preoperative exclusion criteria included previous CABG or valvular heart operation, current intraaortic balloon pump support, severe hepatic disease (alanine aminotransferase or aspartate aminotransferase >150 IU/L), renal insufficiency (creatinine >1.8 mg/dL), severe chronic obstructive pulmonary disease (forced expiratory volume in 1 s < 0.8 L), and history of stroke. Moreover, the patients were excluded if, during the operation, there were complications that, in the judgement of the attending surgeon and anesthesiologist, would likely result in a complicated postoperative course.

All patients received oral lorazepam 2 mg immediately before transfer to the OR, and their cardiac medications were continued through the morning of surgery. Anesthetic induction consisted of fentanyl 5–15 µg/kg, thiopental 4–6 mg/kg, and pancuronium 0.1 mg/kg followed by maintenance with isoflurane and oxygen before, during, and after cardiopulmonary bypass (CPB).

After the induction of anesthesia, a central venous catheter or pulmonary artery catheter was inserted, depending on the patient’s characteristics and anesthesiologist’s criteria. Intraoperative hemodynamic management was standardized. Hypotension (systolic blood pressure < 90 mm Hg) was treated with volume replacement, ephedrine, or phenylephrine, as indicated. Persistent hypertension (systolic blood pressure > 140 mm Hg) was treated by increasing the depth of anesthesia or by using nitroglycerin. Tachycardia (heart rate > 110 bpm) was also treated by deepening anesthesia or by using a ß-blocker, and bradycardia (heart rate < 50 bpm) was treated with atropine or ephedrine. On rewarming during CPB, an analgesic/sedative infusion of fentanyl (20–30 µg/h) was initiated. The fentanyl infusion was continued into the postoperative period, and it was changed to patient-controlled analgesia when the patient had TE and was able to use the device. Supplemental analgesia with IV dipirone (50 mg/kg) was given as required.

After the patient was weaned from CPB, anesthesia was gradually reduced and terminated after the final skin stitch. Paralysis was reversed with atropine 1.0 mg and neostigmine 2.5 mg, and spontaneous respiration was allowed. The patients were transferred to their bed, and they were considered eligible for the study if they were hemodynamically stable and did not have significant bleeding (chest tube drainage < 50 mL in 30 min). The patients had TE in the OR if they fulfilled clinical and blood gas analysis variables (7,10) (Appendix 1). Patients who did not meet all the requirements were TE in the postoperative ICU when the clinical and blood gas analysis criteria were satisfied. When patients fulfilled ICU discharge criteria (7,8) (Appendix 2) and when ward beds were available, they were transferred to the general ward. Twelve-lead electrocardiograms were obtained preoperatively (control) and daily for the first three postoperative days. Blood samples for serum creatine phosphokinase isoenzyme (CPK) MB were obtained at 8, 16, and 24 h after surgery.

The primary outcome measured was ICU LOS. Incidence of reintubation, time in the OR after the end of surgery (last stitch in the skin), and postoperative LOS were recorded as secondary outcomes. Cross-clamp time, CPB time, duration of surgery, number of coronary grafts, routine postoperative results, administered drugs, and complications were also recorded. Acute myocardial infarction (MI) was defined as new Q waves ( 40 ms, 25% R wave height) in the electrocardiogram plus CPK MB > 50 UI/L.

Patients underwent a median sternotomy, with harvesting of saphenous veins and internal thoracic arteries as indicated. CPB was performed by using a membrane oxygenator (^TMMaxima Forté; Medtronic, Inc. Minneapolis, MN) with a continuous flow of 2 to 2.4 L · min^-1 · m^-2. Myocardial protection was achieved by using a combination of antegrade and retrograde cold blood cardioplegia, and the systemic temperature was allowed to drift down to 33°C during CPB. Patients were actively rewarmed to 37°C before discontinuation of CPB. Two surgeons were involved in the study.

Descriptive statistics were summarized as mean ± SD when the results were normally distributed and as median and range when they were not. Student’s t-test was used to determine the significance of normally distributed parametric values and Wilcoxon’s ranked sum test for nonnormally distributed data. Categorical variables were tested using 2 test or, when appropriate, Fisher’s exact test. Statistical significance was accepted at P < 0.05.

	Results

Top Abstract Introduction Methods Results Discussion Appendix 1. Tracheal Extubation... Appendix 2. Discharge Criteria References

 
Fifty patients (50%) were TE in the OR and 50 patients (50%) were TE in the postoperative ICU. The two groups did not have significant differences with respect to age, weight, preoperative physical status, and risk factors, as shown in Table 1. There were no significant differences between groups in duration of surgery, CPB time, minimum temperature, and number of vessels revascularized (Table 2).

Four patients in the group having TE in the OR were reintubated secondary to respiratory abnormalities (arterial oxygen tension < 60 mm Hg, inspired oxygen fraction > 0.5) (normal arterial oxygen tension in Bogotá is 60 mm Hg [8700 ft or 2600 m above sea-level]). In two of these patients, the hypoxemia was accompanied by hypercapnia (PCO₂ > 45 mm Hg), and one of these two patients had a postoperative MI with an uneventful recovery. In one of the other patients, hypoxemia was accompanied by agitation and in the other by supraventricular tachycardia with hemodynamic compromise. The lungs of the four reintubated patients were ventilated for 2–4 h, and they had TE after TE criteria were again achieved. Three patients in the OR group had postoperative MI, and one postoperative MI occurred in the ICU group (P = 0.61). All these four patients recovered satisfactorily. The rate of MI in both groups was typical for our unit in which the incidence of MI for these patients is 4.1%. The incidence of other postoperative treated complications was similar between the two groups, as shown in Table 4. No deaths occurred in either of the groups.

	Discussion

Top Abstract Introduction Methods Results Discussion Appendix 1. Tracheal Extubation... Appendix 2. Discharge Criteria References

Our study demonstrates that up to 50% of selected patients undergoing elective CABG can have TE in the OR, avoiding routine postoperative mechanical ventilation. Additionally, we found that 8% of the patients having TE in the OR required reintubation after developing respiratory abnormalities, whereas no patient having TE in the ICU required reintubation.

Our study differs from a recent study by Royse et al. (12) that showed no reintubations in a series of 100 patients who had TE in the OR after undergoing different cardiac operations. They used a different anesthetic technique (epidural analgesia in many of the patients), and the differences can be explained, in part, by the use of that particular anesthetic and surgical approach. Unfortunately, they did not report the ICU and hospital LOS that was achieved by using their protocol. Another study by Walji et al. (13) revealed an important reduction in the postoperative LOS by using an ultra-fast-track protocol with no patients having TE in the OR. Our results agree with the latter findings in that the TE times did not seem to have affected the transfer from the ICU because it is common practice to require a minimum ICU stay. This minimum ICU stay (in many centers overnight) permits monitoring of the patient and detection of any respiratory or cardiac instability. Other studies of early TE (less than 10 hours) show rates of reintubation from 0.68% to 2% (8,14,15). Our results, showing a rate of 8% reintubation with no change in ICU LOS and hospital LOS, suggest that there is no benefit to TE in the OR and it is no longer part of our routine practice.

The OR and the ICU are the areas associated with the highest cost for patients undergoing cardiac surgery (16). ICU LOS is a commonly used guide to measure cost indirectly, and it has been used in numerous studies (15,17). Decreasing the OR and the ICU LOS would theoretically reduce the cost associated with cardiac surgery. The present study demonstrates that TE cardiac surgical patients in the OR does not result in a significantly shorter ICU or hospital stay. Our data suggest that there are limits below which a further reduction in intubation time will have no effect on ICU LOS and will not produce any relevant cost savings. This observation is consistent with findings of other studies (5,6,18), as the overall method of delivering health care could have a more significant impact on ICU or hospital LOS than the choice of any particular drug or procedure (i.e., OR TE).

Other potential benefits of OR TE include less dependency on nurses or respiratory therapists (19), ventilator disposables are avoided, and patients can be transferred to a lower dependency ICU. We have not attempted to examine these theoretical cost savings. Our unit has a single ICU with a fixed number of medical, nursing, and paraclinical personnel and is without a dedicated lower dependency section. Patients are discharged directly to the ward from the ICU after an established protocol, and as in many hospitals, the transfer occurs at relatively set times of the day centered on nursing shift changes.

Cheng et al. (7) found that early TE (one to six hours) after CABG does not increase perioperative cardiac morbidity. Nonetheless, TE in the OR after CABG can augment respiratory and cardiac workload and potentially increase the incidence of postoperative ischemia and MI. In this study three patients TE in the OR had MI documented by CPK MB elevation and new Q waves in the electrocardiogram, whereas one patient in the group TE in the ICU had the same complication. Although the incidence of MI was higher in the OR group, the sample size in this study is too small to determine if this risk is definitely more with extubation in the OR.

Some authors believe that TE patients in the OR produces a delay in the time spent in the OR and it would increase the OR cost (11). In our experience, this practice does not significantly increase these variables because the patient is promptly evaluated, and any patient who does not achieve the TE variables is transferred to the ICU where he or she will have TE.

In conclusion, our results indicate that TE of selected patients in the OR after CABG is possible, but a moderate rate of reintubation should be expected. This practice is not associated with a significant reduction in the ICU or hospital LOS and, in our experience, it does not produce any benefit when compared with the conventional practice of early TE (one to six hours).

	Appendix 1. Tracheal Extubation Criteria

Top Abstract Introduction Methods Results Discussion Appendix 1. Tracheal Extubation... Appendix 2. Discharge Criteria References

 
Clinical
• Patient responsive to simple commands

Negative inspiratory force > -20 cm H₂O

Oropharyngeal temperature > 36.5°C

Hemodynamically stable

Absence of uncontrolled arrhythmia

Chest tube drainage < 50 mL in 30 min

Blood Gas Analysis
• pH > 7.30

Arterial oxygen tension > 60 mm Hg, inspired oxygen fraction < 0.5

PCO₂ >45 mm Hg

	Appendix 2. Discharge Criteria

Top Abstract Introduction Methods Results Discussion Appendix 1. Tracheal Extubation... Appendix 2. Discharge Criteria References

 
From the ICU
• Alert and cooperative patient

No inotropic support and no significant arrhythmia

Adequate ventilation (arterial oxygen tension > 60 mm Hg, arterial carbon dioxide tension < 45 mm Hg, arterial oxygen saturation > 90%, inspired oxygen fraction < 0.5 via a face mask)

Chest tube drainage < 50 mL/h in 2 h

Urine output > 0.5 mL · kg^-1 · mL^-1

No recent generalized seizures

No active seizure

From the Hospital
• Hemodynamically stable

Stable cardiac rhythm

Noninfected incisions and afebrile patient

Ability to void, bowel movements

Independent ambulation and feeding

	Acknowledgments

 
The authors wish to thank Dr. Luis G. Michelsen for a critical review of the manuscript.

	Footnotes

 
Presented, in part, at the annual meeting of the Society of Cardiovascular Anesthesiologists, Chicago, IL, April 21–24, 1999.

	References

Top Abstract Introduction Methods Results Discussion Appendix 1. Tracheal Extubation... Appendix 2. Discharge Criteria References

 

1. Shapiro BA, Lichtenthal PR. Inhalation-based anesthetic techniques are the key to early extubation of cardiac surgical patients. J Cardiothorac Vasc Anesth 1993; 7: 135–6.[Medline]
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4. London MJ, Shroyer AL, Jernigan V, et al. Fast-track cardiac surgery in a department of veterans affairs patient population. Ann Thorac Surg 1997; 64: 134–41.[Abstract/Free Full Text]
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Anesthesia & Analgesia® is published for the International Anesthesia Research Society® by Lippincott Williams & Wilkins with the assistance of Stanford University Libraries' HighWire Press®. Copyright 2006 by the International Anesthesia Research Society. Online ISSN: 1526-7598   Print ISSN: 0003-2999