Anesthesia for Open Pulmonary Resection: A Systems Approach

Abstract

Perioperative morbidity and mortality are common following lung resection, with most deaths (>75%) attributed to major adverse pulmonary events (MAPE; including pneumonia, acute lung injury [ALI], and acute respiratory distress syndrome [ARDS]). Perioperative risk can be managed by dividing risk into two broad categories: iatrogenic risk and patient-attributed risk. Clinical care pathways manage iatrogenic risk, while perioperative strategies that allow identification and optimal management of high-risk patients manage patient-attributed risk. These factors will improve outcomes and reduce hospital costs. Patient safety and the delivery of quality care, with emphasis on systems improvement, have emerged as central tasks for healthcare providers. In fact, benchmarking of data will increasingly allow patients to identify institutions that deliver on the value proposition – providing medical care that measures up in safety and quality and yet is delivered at significantly lower costs.

Appendices

Clinical Case Discussion

Case: A 68-year-old male presents for anesthesia. He has a 40-pack-year smoking history, hypertension controlled with diltiazem, and hypercholesterolemia controlled with simvastatin. He gives no history of exertional angina. The chest X-ray indicates a mass in the left upper lobe (Fig. 23.5), with absence of metastatic disease as assessed by computerized tomography and by a nuclear bone scan. Pulmonary function testing shows impaired function, characteristic of moderate COPD, with a negligible reversible component and a predicted postoperative FEV₁ of 48%.

Fig. 23.5

Chest X-ray demonstrating a carcinoma of the left upper lobe

Previous diagnostic bronchoscopy revealed encroachment of a non-small cell lung cancer onto the left main stem bronchus. Consequently, he is now scheduled for a bronchoscopy, mediastinoscopy and left upper lobectomy with sleeve resection, and reattachment of the left lower lobe.

Questions

• 1. How does the mediastinoscopy alter perioperative management?

• 2. What airway management technique would be optimal?

• 3. What invasive monitoring is necessary?

• 4. Is there an optimal analgesic regimen?

• 5. Can perioperative fluid management affect outcome?

• 6. What ventilation strategy would promote optimal outcome?

Discussion

Given the rarity of blood loss requiring blood transfusion, an 18- or 16-gauge intravenous catheter, preferably placed in the nondependent hand, wrist, or forearm, would be appropriate. It is best to avoid the antecubital veins as the arms are bent at 90° when the patient is positioned in a lateral decubitus position, and this will hamper flow of the intravenous fluids. In anticipation of continuation to thoracotomy after mediastinoscopy, a thoracic epidural (alternatively, a paravertebral block) is placed in the T5–T8 region prior to induction. Standard noninvasive monitors will be used, with ECG leads placed as for any median sternotomy, thereby allowing the entire chest to be prepped in a sterile fashion in case an emergent sternotomy is required due to massive bleeding resulting from the mediastinoscopy.

After induction, tailored to the patient, the airway is secured using an 8.0-mm single-lumen endotracheal tube to facilitate bronchoscopy. A LMA can be used for bronchoscopy if mediastinoscopy is not required. The endotracheal tube is usually brought out to the side of the mouth closest to the anesthesia machine once the bed is turned 90° for mediastinoscopy.

Given the absence of significant cardiac disease, invasive monitoring, with placement of an arterial line, can be deferred until after the mediastinoscopy is completed, and the decision is made to proceed to a thoracotomy – based on the absence of mediastinal lymph node involvement by the cancer. Placement of the arterial line is preferred in the dependent radial artery. This allows vigilant hemodynamic monitoring since acute hemodynamic embarrassment often occurs during surgical manipulation and due to the risk of catastrophic pulmonary vasculature injury. Significant fluctuations in blood pressure are especially seen with left-sided procedures where compression of the heart may occur during surgical manipulation.

A right-sided DLT would be of greater advantage in this case. Since a thoracotomy with sleeve resection requires surgical reimplantation of the left lower lobe bronchus (Fig. 23.3), a left-sided DLT may hamper optimal surgical exposure. If intubation is profoundly difficult, to the point where even changing the endotracheal tube over a tube changer would place the patient at significant risk, then alternative strategies including placement of a left main stem bronchial blocker or advancement of the single-lumen endotracheal tube into the right main stem bronchus should be considered.

Clear communication between the surgical and anesthetic team is essential if the pulmonary artery requires resection and reconstruction. In this case blood products should be readily available in the operating room, and steps to reduce the pulmonary artery pressure should be implemented. Such steps may include increased oxygenation (FiO₂, 100%), moderate hypocarbia (P_aCO₂, 30–35 mmHg), an appropriately “deep” level of anesthesia, minimized use of phenylephrine (consider vasopressin if blood pressure is low), and inhaled epoprostenol therapy to the ventilated lung.

Timing of initiation of the epidural and the choice of neuraxial medications remains controversial. A common practice is to initiate the epidural prior to induction so that inhalational anesthetics can be reduced to levels where HPV is not hampered. The intraoperative use of the epidural also helps to minimize the use of systemic opioids to reduce the risk of postoperative respiratory depression. Typically, more concentrated local anesthetics (± opioids) are used intraoperatively and more dilute combinations of local anesthetics and opioids used postoperatively.

The management of perioperative fluid therapy remains a controversy without conclusive data to guide treatment. The origins of the controversy stem from the significant risk of mortality from patients who develop ALI after thoracic surgery, in particular, those that develop post-pneumonectomy pulmonary edema. Typical guidelines suggest minimizing crystalloid therapy to 1.0–1.5 L, as this may help to reduce post-lobectomy pulmonary edema and facilitate early postoperative extubation.

Ventilation parameters during OLV typically strive to reduce the risk of ALI associated with barotrauma or volutrauma through tidal volume reduction (<6 mL/kg), respiratory rate > 10 breaths per minute, I:E ratio of 1:2, and peak inspiratory pressure < 25 mmHg. Such a protective ventilatory strategy aims to maintain baseline CO₂ levels or tolerate permissive hypercapnia (pH >7.25) rather than mild hypocapnia. Importantly, prolonged positive-pressure ventilation may hamper the tenuous blood supply of the sleeve anastomosis and increase the risk for a BPF and its associated complications. As such, this necessitates that the overall anesthetic technique be tailored to afford prompt and comfortable extubation of the patient.