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Awake Heart Surgery: Useful Technique or "Trick"?Andrew Maslow, MD
"Fast track" care for cardiac surgical patients is safe and cost-effective. How to achieve this goal depends on individual practices and institutional protocols. Although pain control, early extubation, and patient mobilization are important components of the fast track process, these are not independent of major organ stability, thus highlighting the importance of patient selection, preoperative preparation, surgical technique, and perioperative management. Thoracic epidural analgesia (TEA) has increased and has been described as a significant component of the fast track process for cardiac surgical patients.1-6 Although the literature consistently reports superior analgesia with TEA, few studies describe earlier extubation, and only a handful report improvement of major organ function, earlier discharge from the intensive care unit, and shorter hospital stays.1-6 While feasible and potentially beneficial, there are still concerns regarding the safety of TEA for cardiac surgical patients. Although more than 6000 cardiac surgical patients have received TEA without a reported major complication (epidural hematoma or nerve injury), this does not allow us to state that epidurals can be used as safely for cardiac surgical patients as for non-cardiac surgical patients (incidence of nerve injury approx. 1:30,000).4-6 Furthermore, the risk may be elevated in the presence of coagulation abnormalities, which is a concern for cardiac surgical patients, given the use of preoperative anticoagulant medications, and the effects that surgery has on the coagulation system. Despite these concerns, the use of TEA for cardiac surgical patients continues. More recently, several manuscripts have reported the use of TEA as the sole anesthetic for the performance of CABG in the conscious (awake; ACAB).7-12 All but one of these cases have been performed in patients undergoing off pump CABG (OP CABG). Surgical procedures have included small lateral thoracotomy incisions, lower sternotomy incisions, and full median sternotomy. The majority of cases have included one and two vessel bypasses in the left anterior descending artery (LAD) or right coronary artery (RCA), while only 1-2 cases had three vessels bypassed, or involved bypass of the left circumflex artery (LCx). Only one case of conscious heart surgery has been reported in which cardiopulmonary bypass was employed during aortic valve replacement.9 Awake heart surgery (AHS) has been concluded to be "feasible" and "safe".7-12 The conversion rate to general anesthesia with endotracheal intubation ranged from 0-10%.7,8,10,11 Reasons for conversion included inadequate analgesia, or respiratory difficulties relating to pneumothorax. As many as 28% of cases are complicated by a pneumothorax.7,8,10 Approximately 8% of cases need additional infiltration with local anesthesia in the xyphoid or suprasternal notch, and one patient had inadequate analgesia.8 Of the 208 patients included in these articles, perioperative analgesia was excellent in 207 patients.7-12 Duration of stay in the intensive care unit ranged from 0 to < 24 hours, while hospital stay ranged from 1 to 7 days.7,8,10,11 In one study, 8 patients were discharged home the same day of surgery after meeting the following criteria:8
Although intriguing, attention must be paid to the criteria and protocols employed for these patients and other reports in which epidurals are placed for cardiac surgical patients.1-4,7-12 For ACAB, exclusion criteria included emergent surgery, severe pulmonary disease, a left ventricular ejection fraction (LVEF) < 35-40%, cardiomegaly, poor target vessels, and/or the need for LCx artery bypass. Epidural catheters are not placed in patients receiving platelet-inhibiting and/or anti-thrombotic medicines within 5-10 days of surgery. Low molecular weight heparin was replaced by a heparin infusion, which was discontinued 6 hours prior to surgery. Patients with any abnormal coagulation studies (e.g. PTT > 40 seconds; INR > 1.5; platelet count < 80,000 or < 100,000) were also excluded. Other exclusion criteria included those for which major conduction blockade is contraindicated (patient refusal, hemodynamic instability, local and/or systemic infection, major neurological deficits, thoracic or cervical spine abnormalities). The goal of TEA was to block sensory and motor function between C7 and T8. Blockade of nerve roots above C6 may impair diaphragmatic function. A transient Horner syndrome was reported in approximately 50% of cases.8 Epidural catheters were placed as high as C7/T1 and as low as T4/T5. While a number of protocols placed epidural catheters the day before surgery (with or without radiological confirmation),3,4,7,8 other reports described placement the day of surgery and at least one hour prior to systemic administration of heparin.1,4,8 A bloody tap may lead to postponement of the surgical procedure.1 A number of protocols described a variety of medications to administer through the epidural catheter, including local anesthetics, narcotics, and in one study, clonidine. Additional sedation was administered as needed. While the intraoperative care seemed uneventful, there is inconsistent data regarding the total amounts of medications administered, or changes in cardiac and pulmonary function. An editorial by Dr. Christina Mora Mangano accompanied several of the articles addressing AHS.5 Dr. Mangano correctly and appropriately highlighted a number of concerns, including the stress response (not necessarily limited to the patient), patient movement, irregular respiratory patterns, and the potential for respiratory difficulties. Other concerns include the potential for hemodynamic instability if one had to administer a general anesthetic to a patient with a major conduction block. Dr. Mangano concluded that "There is no place for this trick in the cardiac anesthesiologist's armamentarium ...innovation for the sake of change (or marketing) will increase our patients' risks."5 While Dr. Mangano's editorial accurately reflects the issues surrounding the use of TEA during cardiac surgery, as well as the practice of AHS, there are a number of points that should be readdressed. Although AHS patients were discharged early from the hospital, it is not known that the same results couldn't be obtained with a combined technique of general anesthesia and high thoracic epidural analgesia, or even general anesthesia alone, since no comparisons were made. Whether or not avoidance of CPB is a significant component of the success is also not known. These authors did not study these issues; they simply reported their experience with awake heart surgery. It is plausible that achieving similar results does not require avoidance of CPB, nor that the patient be awake with a high TEA, but instead requires a change in mindset and a coordinated effort along several levels of perioperative care, not the least of which includes the motivation of all those involved in the intraoperative care of the patient. Prior to adopting these practices, it must be noted that the data reported in these manuscripts involve a select group of patients with more stable heart function, undergoing relatively simpler cardiac surgical procedures (e.g. fewer coronary bypasses). At other hospitals similar patients may be candidates for percutaneous coronary intervention and revascularization (PCI) in the cardiac catheterization laboratory. As percutaneous techniques continue to improve and advance, the number of patients requiring surgical revascularization will decrease. Subsequently, patients presenting to the operating room will be older, with a more complicated history, with more significant heart disease, for which a variety of anti-thrombotic and anti-platelet medications are prescribed. Although Dr Mangano does not support the marketing aspect of ACAB, there are some economic realities. Karagoz et al described the use of ACAB for 137 cases.8 Nineteen patients were described as having "contraindications" for general anesthesia. These included 9 patients with end-stage liver disease, 8 with end-stage pulmonary disease, and 2 with mechanical airway obstruction. Of the remaining 118 patients, 26 were performed based on referring physician preference, and 92 cases were performed based on patient preference. Twenty-nine of these were chosen instead of PCI. ACAB may be preferred to PCI if it were similarly invasive, while offering more complete revascularization, and a reduced need for subsequent target revascularization. Whether or not each of us endorses AHS, there are some lessons to be learned. The seemingly routine use of anti-thrombotic and anti-platelet medications may not be necessary in the preoperative period (5-10 days) for more stable patients. As long as clinicians recognize the contraindications for placement of epidural catheters, their safety for cardiac surgical patients will soon be recognized. However, prior to placement of an epidural catheter, both the surgeon and the anesthesiologist must agree on how to proceed in the event of a bloody tap during epidural placement. It is evident that with the right mind-set and multi-level process, the perioperative care of cardiac surgical patients can be greatly improved, making it more safe and satisfying for patients, while improving resource utilization and cost-effectiveness. Instead of dismissing ACAB as a "trick" we should embrace the lessons learned from these authors' experience to make our own practices more effective, efficient, and safer. It is not inconceivable that for select patients, ACAB may be preferred to either GA, GAETT/TEA, or even to PCI. References:
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