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Department of Anesthesiology, Nationwide Children's Hospital and The Ohio State University, Columbus, Ohio
Accepted for publication December 18, 2008.
* Address correspondence to Dr Winch, Department of Anesthesiology, 700 Children's Dr, Columbus, OH 43205 (Email: peter.winch{at}nationwidechildrens.org).
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Introduction |
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After informed consent was obtained, the patient was transported to the operating room and monitors were applied. Smooth intravenous induction of anesthesia was achieved with propofol (2.5 mg/kg) and pancuronium (0.1 mg/kg). Successful direct laryngoscopy and placement of a 28-French double lumen endotracheal tube was confirmed, but peak airway pressures of 50 to 60 cm H2O provided tidal volumes of only 50 to 60 mL/breath.
A rigid bronchoscopy was performed and greater than 150 mL of mucopurulent material was aspirated from the right lung and 50 to 60 mL from the left lung. Ventilation marginally improved, but after discussion with the cardiothoracic surgeon it was decided to perform the transplant on cardiopulmonary bypass.
Although a median sternotomy is generally less painful than a thoracotomy, nonetheless, it represents a significant surgical incision and necessitates narcotic infusions for adequate postoperative analgesia. Because this patient had no pre-existing coagulation abnormality and more than an hour would pass before anticoagulation, it was decided that the benefits of improved postoperative analgesia and respiratory function merited placement of an epidural catheter. A thoracic epidural was successfully placed at the level of T10 using a loss of resistance method with saline. After a negative test dose the epidural was connected to an infusion at 3 mL/hr of 0.1% ropivacaine with 2 mcg/mL fentanyl.
After catheter placement, the patient was repositioned in a supine manner and a bispectral index monitor was applied. A dexmedetomidine infusion was initiated at 0.6 mcg/kg/hr without an initial loading dose. Isoflurane was titrated as indicated, with an end tidal concentration of 0.3% providing stable hemodynamics and a bispectral index value of less than 60.
The patient remained remarkably stable throughout initial incision and the establishment of cardiopulmonary bypass. She required no intravenous narcotic throughout the duration of the case. Separation from cardiopulmonary bypass was efficient and uneventful with lung compliance markedly improved. When the sternum was closed the patient was returned to spontaneous ventilation and was noted to have a respiratory rate between 16 and 18 breaths per minute and tidal volumes between 300 and 450 mL/breath. Although the patient met extubation criteria, given the concerns of the pulmonologist regarding the possibility of reperfusion injuries postoperatively, it was decided that she remain intubated.
Her postoperative course documented remarkable analgesia. The epidural was continued at 3 mL/hr using the initial combination of ropivacaine and fentanyl, and the dexmedetomidine was likewise continued for sedation. Immunosuppression was initiated with tacrolimus, methylprednisolone, and mycophenolate. The patient remained intubated until after the bronchoscopy and bronchoalveolar lavage on postoperative day 2, which revealed mild reperfusion injury and right lower lobe consolidation. The patient was afebrile throughout her hospital course and her white blood cell count was followed daily. On postoperative day 5 the epidural catheter was removed intact.
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Epidural analgesia for major thoracic surgery attenuates the neurohumoral stress response, improves postoperative cardiopulmonary function, and ultimately decreases morbidity and mortality. Anesthesiologists at Texas Children's Hospital presented the use of thoracic epidurals for lung transplantation and concluded that the judicious use of thoracic epidurals can facilitate early extubation, mobilization, and discharge after lung transplantation [1]. Other reported advantages of epidurals include enhanced hemodynamic stability intraoperatively and postoperatively, earlier recovery of consciousness, and earlier recovery of spontaneous ventilation [2].
The safety of placing an epidural in an anesthetized patient is frequently debated. Although case reports describe injections into the spinal cord during epidural blocks, there are no studies demonstrating that epidurals placed in anesthetized patients are at an increased risk of complications. With pediatric patients who are unable to cooperate and remain motionless during epidural placement, there is seldom an alternative to placing the epidural without the patient either being asleep or deeply sedated. In this case, our patient's respiratory status precluded sedation without airway protection.
The placement of an epidural in a patient subsequently requiring immunosuppression mandates careful consideration. Studies suggest that neuraxial analgesia is associated with modest preservation of cellular and humoral immunity [3]. However, a large study from Sweden showed that patients with impaired immune function are at a statistically higher risk postoperatively of infectious complications from regional techniques [4]. Because the detection of an epidural infection or abscess in an intubated patient can be challenging, we maintained vigilance and strict sterility for placement and maintenance of the catheter.
Finally, the use of thoracic epidurals in patients requiring full heparinization for cardiopulmonary bypass is an additional area of concern. The use of such catheters has become more common in recent years. Ho and colleagues [5] presented a statistical analysis suggesting that (at most) one epidural hematoma secondary to catheter placement will occur for every 1,520 patients after coronary artery bypass surgery. His analysis is based on no reported epidural hematomas in the 1,500 reported uses of epidural analgesics in cardiac surgery patients. He states that the actual risk might be considerably lower if the risk of epidural hematoma in cardiac patients is identical to all patients receiving epidurals (without anticoagulation), estimated between 1 in 50,000 to 1 in 250,000 [6].
Pain often heralds the development of epidural hematomas or abscesses. Rapid progression of radicular pain, motor dysfunction, or sensory deficits, or a combination thereof, necessitates frequent neurologic evaluations to detect epidural hematomas or abscesses. Such examinations require a cooperative patient who has received minimal amounts of intravenous narcotics that might otherwise mask these early signs. We credit dexmedetomidine with eliminating her need for supplemental intravenous narcotics and allowing us to perform careful periodic examinations [7]. The dexmedetomidine infusion was continued in the intensive care unit, and the patient was noted to transition smoothly from sleep to wakefulness, allowing for easy evaluation of her neurologic status postoperatively [8].
The risks presented by using regional anesthesia demands that practitioners carefully consider the relative risks and benefits of all available techniques. When discussing with patients the risks and benefits of any procedure, the question is often asked, "Doctor, what would you want for yourself or your child?" If all epidurals functioned as well as the one illustrated in the previously described case report, the question could be easily answered by most practitioners. As a result of this experience, we now consider all patients as potential candidates for thoracic epidurals regardless of intraoperative plans for anticoagulation, and we routinely use dexmedetomidine for intraoperative and postoperative sedation. Although inserting a thoracic epidural in this patient was not without risk, we maintain that the benefits justified the placement.
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