Is There a Best Approach for Patients with Difficult Airways: Regional versus General Anesthesia?

Introduction

Airway management is the essence of the practice of clinical anesthesiology. Preoperative assessment of the patient’s airway is the first step in the evaluation and planning of a safe, appropriate anesthetic plan. For the majority of patients, this can be readily achieved with a brief systematic history and physical examination and does not require additional diagnostic evaluation.

It may be anticipated that some patients will be difficult to intubate, based on a history of difficult intubation or clinical predictors of difficult intubation. The American Society of Anesthesiologists (ASA) Practice Guidelines for Management of the Difficult Airway reviews some of the historical and physical examination findings possibly suggestive of a difficult intubation. Some of these predictors of anticipated difficulty with conventional direct laryngoscopy (Mac/Miller) include a large overbite, large tongue, narrow mouth opening, or short chin. Various prediction models, such as correlation with Mallampati oral views I to IV to the Cormack-Lehane laryngoscopic view grades I to IV, have been proposed, but none offers 100% sensitivity for prediction of a difficult airway. Despite such an evaluation, an estimated 1% to 3% of patients in the operating room have an unanticipated difficult airway to intubate with conventional direct laryngoscopy.

In addition to this 1% to 3% incidence of patients, cohorts of patients have specific pathologic conditions that are known to cause difficulties with conventional laryngoscopy. These patients may require more complex or multispecialty clinician airway management that may only be readily or immediately available in specialty or tertiary care centers.

The ASA Practice Guidelines for Management of the Difficult Airway encourage all practitioners to review the airway algorithm presented in the document and provide resources for the creation of difficult airway management carts that can be readily mobilized for elective and emergency airway management.

The goal, then, of the preoperative airway evaluation is to categorize the patient into one of two categories: (1) not difficult to intubate with conventional Mac/Miller direct laryngoscopy; or (2) anticipated to be difficult to intubate with conventional Mac/Miller direct laryngoscopy. In either category, unanticipated difficulty with the chosen airway management technique is a reality.

Of the patients who have an anticipated difficult airway, a certain percentage will be scheduled for surgical procedures that are amenable to regional anesthesia as the primary anesthetic or for postoperative pain management. For example, many orthopedic limb cases, lower abdominal surgeries, and urologic procedures can be performed with a regional technique and without anticipated airway management.

In these instances, regional anesthesia can be an attractive option for some clinicians when faced with a patient with anticipated difficult intubation who is scheduled for an appropriate surgery and who does not have other contraindications to regional anesthesia. However, if, during the procedure, the regional technique needs to be converted to a general airway-controlled anesthetic and adverse outcomes may be related to the urgent nature of the airway management, many clinicians are quick to criticize the role of regional anesthesia in these patients as a primary anesthetic. They advocate that, in the case of the anticipated difficult airway, the patient’s airway must be electively controlled at the beginning of the case, and regional anesthesia should only be a component of a combined regional–general technique.

This chapter reviews the evidence supporting the decision to initiate a regional or general anesthetic in patients with anticipated difficult airways who are scheduled for appropriate surgical procedures. Patients in whom difficulty with airway management is not anticipated preoperatively and patients undergoing surgical procedures not amenable to regional anesthesia alone (e.g., intrathoracic or intracranial surgery) are not addressed in this chapter.

Options/Therapies

The appeal of choosing a primary regional anesthesia technique is that airway management and the potential complications in these complex patients may be able to be avoided. The ability to provide safe and adequate anesthesia without using an instrument on the airway can be a relief to both the patient and the anesthesiologist. The need to address issues of extubation of the difficult airway and postoperative care can also be avoided.

Depending on the surgical case, as well as the patient’s preferences, many different regional anesthetics may be appropriate. Neuraxial techniques, such as spinal or epidural anesthesia, as well as regional blocks such as brachial plexus, lumbar plexus, and specific nerve blocks, can provide excellent anesthesia, with or without concomitant sedation. Indwelling catheter techniques, such as for epidural or some extremity blocks, also allow postoperative pain to be managed successfully in certain cases.

The potential downfall of the regional anesthesia alternative is that the regional technique may be technically difficult, may be incomplete, or may fail, necessitating the conversion to a general anesthetic with or without intubation or a protected airway. The likelihood of failure of the regional technique cannot be predicted because it depends on the skill and experience of the anesthesiologist performing the neuraxial or nerve block. In addition, patient-specific factors, such as an inability to tolerate being awake or minimally sedated (so as to avoid respiratory depression), may require conversion to general anesthesia. Finally, surgical considerations such as extension of the procedure may require a change from regional to general anesthesia.

Conversion from a regional to a general anesthetic may be required at a time when the patient’s airway is relatively less accessible to the anesthesiology team, as well as at a time when the deteriorating patient condition mandates hastening the ventilation and intubation process. It is important to recognize, in the words of Benumof, “Use of regional anesthesia in the patient with a recognized difficult airway does not solve the problem of the difficult airway; it is still there.”

On the other hand, the appeal of a planned general anesthetic is that the airway can be approached in a controlled and measured fashion. This chapter does not provide an in-depth review of airway management techniques, but basic considerations include choosing between surgical and nonsurgical approaches, asleep versus awake techniques, and spontaneously ventilating or apneic patients. Specific intubating methods could include direct laryngoscopy, rigid or flexible fiberoptic laryngoscopy, or placement of a laryngeal mask airway (LMA) as a bridge toward definitive control of the airway, among many other possible forms of intubation ( Figure 16-1 ).