Regional Anesthesia and the Difficult Airway

Patient

Not all patients are good candidates for regional anesthesia. The use of regional anesthesia for anesthetic management, rather than securing the airway, may be considered in adult patients who are calm, motivated, possess adequate communication skills, and understand and accept the risks and benefits of a regional technique over general anesthesia.

In a patient with a known or anticipated DA, this condition and its implications must be discussed in detail with the patient. The benefits of regional anesthesia in general and specifically for the individual patient should be explained. The regional anesthesia procedure itself, effects, side effects, and complications, as well as general anesthesia, including the plan for airway management, must be discussed comprehensively because the need to manage the airway can arise at any time during the procedure. ^, Therefore, the anesthesia consent should include the perioperative management of the airway.

Contraindications for regional anesthesia include physical and psychological conditions of the patient, such as the inability to lie flat on a hard operation room table for a long period of time; back pain; restless leg syndrome; other movement disorders; anxiety; panic disorder; claustrophobia; or posttraumatic stress disorder. These factors can limit the patient’s tolerance for undergoing a surgical procedure under regional anesthesia and the feasibility of this approach. In addition, an increased requirement for sedation may represent a contraindication for the use of regional anesthesia.

Patients with morbid obesity are especially challenging, as these patients may be difficult to mask-ventilate and intubate. Additionally, neuroaxial and peripheral regional blocks may be taxing for this patient population, as surface landmarks are difficult to palpate and the target structures are deep and harder to identify with ultrasound (US). Furthermore, sedation is problematic as these patients often have obstructive sleep apnea. Nonetheless, regional anesthesia techniques are beneficial for this population as they are at higher risk for pulmonary complications and side effects of opioid medications with alternate techniques.

An appropriate assessment of the patient’s airway is the first step, irrespective of any initial thoughts. Although the ability to accurately predict a DA preoperatively would be of great value, it is evident from the literature that no single airway assessment nor any composite score can reliably do this. ^, Nevertheless, a preoperative airway history and physical examination should be performed to facilitate the choice and management of the DA, as well as to reduce the likelihood of adverse outcomes. Findings that are not reassuring should prompt a reconsideration of the primary airway management plan and exit strategies. ^,

The physical assessment of the airway should include assessments for indicators of difficult intubation (DI) and potentially difficult alternative or fallback strategies, such as face-mask ventilation, supraglottic airway (SGA) placement, and front-of-neck access. ^, Both face-mask ventilation and SGA are recommended fallback techniques or alternatives in the ASA’s DA algorithm, the recommendation of the CAFG, and the British DAS guidelines, and a front-of-neck approach to the airway is the recommended step in the “cannot intubate/cannot oxygenate” (CICO) situation.

Surprisingly, routine airway assessment is not performed reliably by all anesthesiologists in every patient undergoing general anesthesia, and even less so in patients undergoing regional anesthesia. In 2012 McPherson and colleagues took a survey in the United Kingdom and Europe of anesthesiologists’ practices for predicting DI. They found that 33% of the European and 44% of the UK anesthesiologists did not assess the airway in all patients undergoing general anesthesia, and 62% of the UK anesthesiologists and 52% of the European anesthesiologists did not always assess the airway in patients undergoing surgery under regional anesthesia.

The information that patients can provide about a previous DI differs widely. If available, review of a DA letter, previous anesthesia records, or imaging of the airway can provide further information; however, gaining timely access to such records can be challenging.

Notwithstanding the depth of information available regarding a previous intubation, any changes in the patient’s body habits and airway since that event must be explored because they can further complicate airway management. Information such as additional weight gain, radiation treatment, and scar formation also needs to be evaluated. Previously successful techniques might not be feasible when additional conditions further alter the airway.

A preoperative endoscopic airway examination (PEAE), done at the bedside, can provide further information about the current status of the airway and potential problems.

In a review of 50,000 anesthetics, Kheterpal and colleagues reported an incidence of impossible mask ventilation in 0.15% of the patients; 25% of these patients were difficult to intubate, but only 1 patient required surgical airway access. A history of radiation, male gender, Mallampati score of III or IV, and a beard were identified as risk factors for difficult mask ventilation. Ramachandran and colleagues reviewed 15,795 patients undergoing anesthesia with the Laryngeal Mask Airway Unique (LMA Unique) and reported a failure to achieve an airway in 1.1% of the patients; more than 60% of these patients developed hypoxia, hypercapnia, and airway obstruction. The risk for difficult mask ventilation was three times higher in patients with failed LMA Unique placement compared with successful placements. Independent risks for LMA Unique failures reported were male gender, poor dentition, elevated body mass index (BMI), and surgical table rotation.

Airway

A US assessment of the airway with identification of the cricothyroid membrane can also be performed during the preoperative visit. This examination does not require more than a couple of minutes and can be especially helpful in patients with ambiguous neck anatomy.

Portable handheld ultrasound probes are now widely available and simplify a screening assessment of both the airway and regional anesthesia target.

Airway Management Plans

Poorly planned airway management strategies in patients with potential DA and delays in changing unsuccessful strategies were identified as problems in the Fourth National Audit Project (NAP4) study. Joffe and colleagues identified lack of adequate planning as a contributing factor for airway-related morbidity in an analysis of closed claims. Because routine airway management techniques might not secure the airway in a patient with a DA, a safe plan specific for the individual patient needs to be delineated. ^{, ,} This plan should include strategies for an emergency/urgent access and a nonurgent/nonemergent access. A stepwise approach for both situations should be outlined, as well as alternative strategies in case the primary plan fails to successfully secure the airway. A flexible intubation scope, video laryngoscope, and SGA should be readily available for the patient during the entire time in the perioperative area.

Any plan is only as good as the anesthesia provider who executes the plan. Competence with the techniques and familiarity with the equipment are critical aspects for choosing a specific plan.