Airway Management in Non-Operating Room Locations

KEY POINTS

• Specific training for non-operating room anesthesia (NORA) should be incorporated into anesthesia residency programs.

• Monitoring for both oxygenation and ventilation is required during sedation, including the use of capnography.

• Intubation of the patient with an anticipated difficult airway (DA) may be best managed in the operating suite with optimal equipment and familiar anesthesia staffing before transporting the patient to the NORA location.

• An anesthesia machine offers convenient means of providing oxygenation, ventilation, volatile anesthesia, suction, and ease of conversion to general anesthesia, if required.

• Sedation can be safely used for many NORA procedures, but the precautionary principle should be applied for complex, lengthy procedures or where the need for immobility or risk of hemodynamic instability is present.

• Management of the unanticipated DA in a NORA location should be the same as in the OR, utilizing DA algorithms and calling for assistance early.

• Long anesthesia circuits are especially useful in many NORA locations.

Introduction

In recent years, the coverage responsibilities of anesthesiologists have evolved from traditional operating room (OR) locations to encompass more remote areas in the hospital. Non-operating room anesthesia (NORA) refers to administration of anesthetic care outside of the OR for patients undergoing procedures. Under the umbrella of NORA fits a diverse range of procedures with unique procedural requirements, equipment, and risks that are united in their out-of-OR location. NORA locations and specialties include endoscopy, cardiology, pulmonology, and radiology and are detailed in Table 42.1 . As expert providers of sedation and general anesthesia both inside and outside of the OR, anesthesiologists should take the lead in ensuring that safety is maintained in this growing specialty.

A rapidly increasing proportion of cases are being performed in remote locations due to advances in diagnostic and interventional techniques and greater patient expectations for amnesia and sedation. From 2005 to 2007, approximately 12% to 15% of the total anesthesia workload was outside of the OR. ^, Data from the National Anesthesia Clinical Outcomes Registry (NACOR) for the period 2010 to 2014 showed that NORA as a proportion of all anesthesia cases increased from 28.3% in 2010 to 35.9% in 2014. In other countries, NORA composes a much smaller percentage of all cases, accounting for only 8.2% of all cases in a large Korean study of 199,764 cases between 2013 and 2017. There are estimates that, within the next decade, the proportion of NORA will approach or even exceed traditional OR cases. ^,

Safety Profile and Risks of NORA

Safety data for non-OR locations are not reassuring, performing poorly compared with OR locations. Certain NORA locations feature prominently in closed claims analyses and observational studies, including the endoscopy suite, radiology, and cardiac catheterization suites. These closed claims analyses showed that injuries in NORA locations were more severe and more likely to result in death when compared to OR closed claims. Most adverse events in NORA locations are respiratory in origin, which is often attributed to oversedation resulting in inadequate ventilation and oxygenation during monitored anesthesia care (MAC). ^,

A prospective multicenter observational study in 2132 patients undergoing gastrointestinal endoscopy with propofol sedation confirmed the risks of NORA, reporting unplanned events in 23% of patients, significant hypotension in 11.8%, and a 30-day mortality of 1.2%. A large database study found that the incidence of cardiac arrest and death was 3.92 per 10,000 in patients undergoing gastrointestinal endoscopy, with most arrests attributed to hypoventilation and hypoxemia. Studies in the pulmonology suite and cardiac electrophysiology laboratory both report high rates of adverse events that are often respiratory in origin. ^,

Although some studies, especially those with a large proportion of pediatric patients, show that complications in the NORA setting are rare, ^{, ,} other studies point to concerning rates of complications when compared with OR locations. An understanding of the nature of these complications, including the overrepresentation of respiratory causes, is needed to improve the safety of NORA.

NORA locations are generally found at a distance from the main ORs; therefore, access to skilled anesthesia personnel and equipment may not be immediately available. Unlike the standardized layout of most ORs, NORA locations are highly differentiated, resulting in an unfamiliar working environment for the anesthesia provider. These suites are designed for the specific procedure being undertaken, incorporating bulky imaging and procedural equipment, resulting in limited available workspace for anesthesia personnel and equipment. Access to the patient, specifically the airway, may be limited as the anesthesia provider is often more physically distant from the patient during the procedure. The procedure table may lack the degree of adjustability of an OR table. The environment can be noisy and dimly lit, interfering with observation of the patient and monitors. Lower ambient temperatures are typical to avoid overheating of equipment, which can result in patient hypothermia. Radiation safety must be considered for both patients and staff, requiring the use of lead aprons, thyroid shields, and glass lead screens. Equipment that is taken for granted in OR locations may not be readily available, including scavenging and suction systems; piped wall air, oxygen, and inhalational anesthesia; an anesthesia machine; or difficult airway (DA) carts, cardiac arrest carts, and malignant hyperthermia carts.

Staff in NORA locations are generally less familiar with anesthesia procedures, their unique requirements and equipment, emergencies, and airway management. A growing number of emergency procedures and procedures are being performed outside of normal working hours when reduced staff familiarity and resource limitations are likely to be amplified. Because many procedures occurring in NORA locations are minimally invasive, they may be offered to patients who are otherwise too frail or unfit for open surgical procedures; thus NORA patients tend to be older and sicker than those in OR locations. ^{, ,}

In addition to the general risks of NORA, specific risks according to the procedure and patient cohort are outlined in Table 42.2 . Prior to anesthetizing a patient in a NORA location, the anesthesia provider should understand the planned procedure, duration, patient positioning, need for immobility and sedation, expected level of discomfort, and other specific requirements.

Monitoring Requirements of Nora

To ensure NORA locations meet the same safety profile as the OR, patient assessment and optimization should be equally thorough. Organizational policies should address minimum facility and equipment requirements. The use of a smaller pool of dedicated anesthesia providers for NORA locations who have undergone specific NORA training ^, can further assist with risk mitigation.

In closed claims analyses, inadequate oxygenation and ventilation feature highly in NORA claims, with anesthesia care often judged to be substandard and preventable by better monitoring. Patient monitoring in remote locations should be equivalent to OR standards and should adhere to guidance provided by the major national anesthesiology societies, including those published by the American Society of Anesthesiologists (ASA) ( Box 42.1 ), the Canadian Anesthesiologists’ Society, the Australian and New Zealand College of Anaesthetists, and the Association of Anaesthetists of Great Britain and Ireland.

Pulse oximetry should be used for all patients undergoing general anesthesia or procedural sedation, ^{, , ,} although it must be recognized that this is a useful indicator of oxygenation but not ventilation, as a fall in oxygen saturation may be delayed relative to the onset of apnea. ^, The oxygen reserve index is a novel noninvasive measure of oxygen reserve detecting Pa o ₂ levels <150 mm Hg, giving an early warning of impending desaturation. ^,

When capnography is used during procedural sedation, respiratory depression is more likely to be detected prior to the onset of hypoxia. ^, Monitoring for presence of exhaled carbon dioxide (CO ₂ ) became an ASA standard for general anesthesia in 1991 and was extended to moderate or deep sedation in 2011. ^, International guidelines endorse the use of exhaled CO ₂ monitoring for sedation, in addition to general anesthesia. Closed claims data support that monitoring requirements for oxygenation and ventilation should be independent of the depth of sedation, ^, and the findings in the Fourth National Audit Project of the Royal College of Anaesthestists (NAP4) were another major factor in encouraging widespread adoption of end-tidal CO ₂ monitoring outside of the OR.

CO ₂ monitoring during sedation can be achieved using capnography from a sampling line incorporated into nasal prongs or attached to a face mask or bite block. When used in this manner, air entrainment and dilution by high fresh gas flows will result in lower end-tidal CO ₂ levels and underestimation of arterial CO ₂ . However, there is value in detecting qualitative changes including waveform shape, respiratory rate, evidence of airway obstruction, or apnea. ^,

Other methods of monitoring ventilation are described in Table 42.3 , including acoustic respiratory monitoring, impedance monitoring, respiratory volume monitoring, and transcutaneous CO ₂ monitoring, with potential advantages over traditional capnography.

Choice of Anesthesia and Sedation

Many NORA cases can be performed using procedural sedation, especially brief procedures in relatively healthy patients. For complex procedures, medically unwell patients, or patients with an identified DA, general anesthesia with preemptive control of the airway may be preferred.

The purpose of sedation is to control pain or anxiety, improve patient cooperation, and/or provide amnesia and decreased awareness. The ASA defines four distinct levels of sedation on a continuum: minimal, moderate, deep, and general anesthesia. The commonly used term conscious sedation refers to mild or moderate sedation. Deep sedation is frequently chosen in NORA locations and is generally accomplished without a definitive airway. A 2015 survey of 409 Australian anesthesiologists of individual sedation practice for endoscopy patients revealed that a deep level of sedation, where the patient was unresponsive to painful stimulation, was targeted by 54% of respondents. In a study of 87 patients undergoing colonoscopy, the measured depth of anesthesia in the 43 patients who received propofol-based sedation was consistent with general anesthesia for a significant part of the procedure. MAC is commonly employed in NORA locations and featured highly in closed claims analysis. ^{, ,} MAC involves an anesthesia provider participating in the care of a patient undergoing a diagnostic or therapeutic procedure and includes all aspects of anesthesia care, including sedation and treatment of complications and coexisting medical problems. ^, A key requirement is that the qualified anesthesia provider must be prepared to convert to general anesthesia if necessary.