Anesthesia for Procedures in NonOperating Room Locations

Importance of Communication

Remote locations are structured differently from the typical OR, but clear communication is prudent for efficient and safe practice in either site. With clear communication, the actions of anesthesia personnel can be integrated with those of the procedural team involved in the NORA intervention. The anesthesia provider should have a detailed plan for communicating with more centrally located anesthesia colleagues and technicians in case help is urgently required. For instance, an unexpected difficult airway can be especially challenging because of the remote NORA location. Additional anesthesia personnel and resources should be immediately available if needed. Sometimes the anesthesia providers in NORA locations feel isolated from the facilities available to OR personnel. The lack of mutual experience and vocabulary presents challenges for anesthesia providers and other staff working in NORA locations. Anesthesia providers and proceduralists should have a shared understanding of the specifics and challenges in the procedures in addition to those in medical care. Anesthesia providers working in an unfamiliar remote location must keep track of the identity and role of personnel participating in the interventional procedure or patient care. During times when the anesthesia provider may need experienced medical assistance (e.g., tracheal intubation, placement of an invasive monitor, or intravenous access), the availability of qualified staff members must be identified. Readily available preoperative documents for all patients in remote locations must include patient history and physical examination by the attending proceduralist. Patient arrival and check-in arrangements should be similar to those for patients undergoing procedures in a traditional OR setting.

Standard of Care and Equipment

Anesthesia care provided in remote locations must adhere to the same standards as those for the OR. The ASA has issued a Statement on Nonoperating Room Anesthetizing Locations that posts minimal guidelines for NORA procedures. In summary, the statement recommends adequate monitoring capabilities, the means to deliver supplemental oxygen via a facemask with positive-pressure ventilation, the availability of suction, the equipment for providing controlled mechanical ventilation, an adequate supply of anesthetic drugs and ancillary equipment, and supplemental lighting for procedures that involve darkness. The same perioperative precautions for infectious diseases must be followed in NORA locations to protect the health and safety of patients and health care workers. During the coronavirus disease 2019 (COVID-19) pandemic, mitigating the risk of airborne transmission poses extra challenges because an isolation room may not be readily available in every NORA location. One option is to perform airway management (intubation and extubation) in a designated negative-pressure room for patients with confirmed or suspected COVID-19 infection.

It is not always possible to place the anesthesia workstation in close proximity to the patient owing to the presence of essential, specialized equipment such as fluoroscopy systems. The additional distance and material between the anesthetized patient and the provider pose further safety concerns for both parties. There are frequently additional hazards, such as exposure to radiation, loud sound levels, and heavy mechanical equipment. Advance preparation should be made to ensure all the necessary safety equipment are available, such as personal radiation protective garments, portable radiation shields, and eye and ear protection. If anesthetic gases are to be used, scavenging must be sufficient to ensure that trace amounts are below the upper limits set by the Occupational Safety and Health Administration (OSHA) (also see Chapter 49 ). After the procedure, one often has to travel longer distances to the postanesthesia care unit (PACU). To do so safely and expeditiously, these remote locations should have available sufficient supplies of supplemental oxygen, transport monitors, and elevator access keys. The anesthesia provider should always know the location of the nearest defibrillator, fire extinguisher, gas shutoff valves, and exits.

Radiation Safety Practices

Ionizing radiation and radiation safety issues are commonly encountered in NORA locations. Radiation intensity and exposure decrease with the inverse square of the distance from the emitting source. Frequently, the anesthesia provider can be located immediately behind a portable lead-glass shield. Regardless of whether this is possible, the anesthesia provider should wear a lead apron and a lead thyroid shield and remain at least 1 to 2 m away from the radiation source. Radiation-induced cataracts are a recognized hazard for interventional cardiologists and radiologists. A 2017 study of eye lens dosimetry in anesthesiology highlighted the importance of maintaining radiation safety standards and adequate eye protection for anesthesia providers working for a significant time in the radiology suite. Clear communication between the radiology and anesthesia teams is crucial for limiting radiation exposure.

Monitoring the Radiation Dose

Anesthesia providers, like all other health care workers who are at risk for radiation exposure, can monitor their monthly dosage by wearing radiation exposure badges. The physics unit of measurement for a biologic radiation dose is the sievert (Sv): 100 rem = 1 Sv. Because some types of ionizing radiation are more injurious than others, the biologic radiation dose is a product of the type-specific radiation weighting factor (or “quality factor”) and the ionizing energy absorbed per gram of tissue. Radiation exposure can be monitored with one or more film badges. In the United States the average annual dose from cosmic rays and naturally occurring radioactive materials is about 3 mSv (300 mrem). Patients undergoing a chest radiograph receive a dose of 0.04 mSv, whereas those undergoing a computed tomography (CT) scan of the head receive 2 mSv. Federal guidelines set a limit of 50 mSv for the maximum annual occupational dose.

Adverse Reactions to Contrast Materials

Contrast materials are used in more than 10 million diagnostic radiology procedures performed each year. In 1990 fatal adverse reactions after the intravenous administration of contrast media were estimated to occur approximately once every 100,000 procedures, whereas serious adverse reactions were estimated to occur 0.2% of the time with ionic materials and 0.4% of the time with low-osmolarity materials. Radiocontrast materials can trigger anaphylaxis in sensitive patients, and such reactions necessitate aggressive intervention, including the administration of oxygen, intravenous fluids, and epinephrine, with epinephrine being the essential component of therapy (also see Chapter 45 ).

Adverse drug reactions are more common after the injection of iodinated contrast agents (used for x-ray examinations such as CT) than after gadolinium contrast agents (used for magnetic resonance imaging [MRI]). The signs and symptoms of anaphylaxis can be mild (nausea, pruritus, diaphoresis), moderate (faintness, emesis, urticaria, laryngeal edema, bronchospasm), or severe (seizures, hypotensive shock, laryngeal edema, respiratory distress, cardiac arrest). Premedication can be used to inhibit the activation of mast cells and basophils, which release inflammatory cytokines such as histamine, serotonin, and bradykinin and cause severe vasodilation and possible shock. The mainstays of treatment include steroids and antihistamines, administered on the night before and the morning of the procedure, with a typical regimen of 40 mg prednisone, 20 mg famotidine, and 50 mg diphenhydramine for an adult. Patients undergoing contrast procedures usually have induced diuresis from the intravenous osmotic load presented by the contrast agent. Adequate hydration of these patients is important to prevent worsening of coexisting hypovolemia or azotemia. Chemotoxic reactions to contrast media are typically dose-dependent (unlike anaphylactic reactions) and related to the osmolarity and ionic strength of the contrast agent.

A serious adverse reaction called nephrogenic systemic fibrosis (NSF) can occur after exposure to gadolinium-based MRI contrast agents. In NSF there is fibrosis of the skin, connective tissue, and sometimes internal organs. The severity can range from mild to fatal. However, NSF apparently occurs only when severe renal impairment (e.g., dialysis-dependent renal failure) also exists. Anesthesia providers and radiologists should not unnecessarily administer gadolinium-containing MRI contrast agent to patients with renal disease.

MRI Safety Considerations

Although MRI does not involve ionizing radiation, other safety issues are prominent in the magnet suite. Hearing loss may occur from high sound levels during the scan. Electrical burns can occur if incompatible monitoring equipment is attached to the patient. Similarly, patients with ferromagnetic implants should never be placed inside a large magnetic field, as device heating and malfunction can result in patient injury. Finally, missile injury can occur if ferromagnetic objects are brought within the vicinity of the magnetic field.

Objects in the magnet room need to be both MRI safe and MRI compatible. The term “MR conditional” was defined by the American Society for Testing and Materials to describe an item that poses no known hazards in a specified MRI environment (based on the static magnetic field strength and spatial gradient field generated by the MRI model). Before entering the magnet room, one needs to ensure the patient has been screened and cleared by MRI technicians to rule out the presence of susceptible metal objects such as incompatible orthopedic hardware, cardiac implantable electronic devices (CIEDs), or catheters with ferromagnetic material. Only an MRI-compatible fiber-optic pulse oximeter should be used; otherwise, burns can result at the point of skin contact with a standard pulse oximeter. Similar concerns pertain to any other monitoring or management devices that make patient contact. Of note, some popular brands of athletic clothing contain metallic microfibers that can result in skin burns during MRI.

Missile injury in an MRI suite is a serious and life-threatening risk. The superconducting electrical currents that generate an MRI scanner's large magnetic field are always “on.” Therefore MRI scanners are always surrounded by large magnetic field gradients (up to 6 m away). Magnetic field gradients can pull metallic objects into the magnet with alarming speed and force. Certain metals such as nickel and cobalt are dangerous because they are magnetic, whereas other metals such as aluminum, titanium, copper, and silver do not pose a missile danger. These metals are used to make MRI-compatible intravenous poles, fixation devices, and nonmagnetic anesthesia workstations. MRI-compatible intravenous infusion pumps are clinically available. If one must bring susceptible metal items such as infusion pumps into the MRI magnet room, they should be safely located and fixed, preferably bolted to a wall or floor. The additional equipment should be placed and verified as secure before the patient enters the MRI scanner. In the event that an object is pulled into the magnet causing patient injury and equipment damage the superconducting magnet can be turned off immediately. This process, called quenching, should only be performed by MRI technicians. The superconducting magnet of an MRI operates at cryogenic temperatures near absolute zero and requires coolant (cryogen) such as liquid helium to maintain the low temperature. The quenching process involves a rise in temperature of the superconducting magnet with escape of cryogen into a venting system outside the MRI room. However, cryogen can escape into the MRI room and displace oxygen, which can cause cold injury and asphyxiation.