ASA October 2003 Newsletter

Delivering anesthesia care outside of the operating room (O.R.) is becoming increasingly prevalent. This article will discuss the provision of anesthesia in endoscopy units, diagnostic/therapeutic imaging suites and radiation therapy suites.

Anesthesiologists are increasingly being asked to provide services in areas that are foreign to the usual operating room setup, in places that are poorly stocked or set up, and often on short notice for very sick patients who have frequently had poor medical/preoperative assessments. Be aware that the personnel in many of the locations that you are called to may not be helpful, cooperative or educated about your needs. In many institutions, anesthesiology departments have a policy of never proceeding to any of these areas without an anesthesia care team of an anesthesiologist and another anesthesia provider. Additionally it is essential to have an anesthesia technician that is committed to off-site anesthetizing locations who is immediately available for unanticipated situations that may require additional equipment or help. It is also the prerogative and responsibility of the attending anesthesiologist not to start a procedure or to insist that it be performed in the operating room if patient condition warrants.

Anesthesia in Endoscopy Suites
The provision of anesthesia in this type of unit can be challenging from many perspectives. In many institutions, including ones that this author has set up, the suite exists as an “open” unit. In other words, requests are forwarded to the person responsible for scheduling each particular procedure, and the patient simply appears on the appointed day for the procedure without having ever seen an endoscopy physician! Issues of medical necessity for a particular procedure along with the more obvious lack of a doctor-patient relationship can make the anesthesiologist’s job more challenging.

Generally the referring physician has recognized when the patient will require monitored anesthesia care (MAC), which should be set up under a stringent set of institutional guidelines established by the anesthesiology department. The patient should go through the preoperative assessment clinic like any other preoperative patient and undergo evaluation by the anesthesiology department.

From a technical perspective, like most other off-site anesthetizing locations, the rooms are small. Upper endoscopies (EGDs) require adequate topical anesthesia that is best administered by the anesthesiology team because the gastroenterologists may frequently wait too late for the local to work well, or they do not use enough or spread it adequately into the retropharynx. Cetacaine should be avoided as it leaves a filmy residue on the tissue, making visualization difficult at best. Preference is given to a gargled solution of flavored viscous xylocaine for a minimum of 60 seconds. On occasion it may become necessary, if a patient’s condition allows, to administer an antisialogogue such as glycopyrrolate to provide a drier examination environment. Endoscopies during which multiple fine-needle aspiration biopsies are performed and echocardiography is used can be quite lengthy.

Nasal cannula oxygen with end-tidal CO2 monitoring capability as well as the other usual monitoring equipment are a must for all procedures. Complicated procedures such as endoscopic retrograde cholangiopancreatography (ERCPs) generally are done in a diagnostic imaging suite and will require the patient to be in the left lateral decubitus or prone (more common) position. It is important to time your sedation for the various more stimulating parts of each procedure. It has been this author’s general practice to use a combination of fentanyl and midazolam given intermittently as well as a propofol infusion for almost all endoscopy procedures.

For lower-endoscopy procedures such as colonoscopies, the patient may be rotated through a variety of positions during the examination and may require several boluses of medication for particularly stimulating parts of the study. The same medication regimen may be used as for upper-endoscopy procedures.

The most important caveats for providing anesthesia in the endoscopy suite are: 1) take control of the anesthesia schedule as early as possible upon arrival in the suite to minimize down-time; 2) ensure that space and equipment are available to provide a safe anesthetic; 3) be prepared for a bowel or duct rupture at any time requiring emergent transport to the operating room; and, when indicated, 4) you should always have blood or blood products on hand in the suite, i.e., for banding of esophageal varices or for a patient who is already bleeding due to a gastrointestinal condition or for an underlying pre-existing coagulopathy.

Anesthesia in a Diagnostic Imaging Suite
Diagnostic/therapeutic imaging suites are extremely varied and offer a variety of anesthetic and radiologic services hospital-to-hospital. In some facilities, large numbers of both diagnostic and therapeutic invasive procedures are performed on patients within the extremes of age and health. As stated above, it is important to have a patient go through the usual preoperative assessment process and to have adequate monitoring equipment and space to provide safe service. From a technical standpoint, frequent barriers to an adequate setup may include the inability to fit an anesthesia machine in the room, inadequate oxygen hookups and inadequate or unavailable suction or evacuation outlets. It is important to have familiarized yourself with these limitations long before you are called to administer an anesthetic, which may be urgent in nature.

In the case of anesthesia in a magnetic resonance imaging (MRI) suite, the institution should have made adequate arrangements during installation of the MRI scanner to hard-wire appropriate monitoring equipment into the suite, including the capability to monitor end-tidal CO₂. There are now anesthesia machines with ventilators available for use in the MRI scanner that do not succumb to magnetic interference. The vast majority of these ventilators are pressure-controlled.

MRI cases done under “sedation” can usually be done with ease using an infusion of propofol and intermittent boluses of fentanyl and midazolam (or other narcotics as indicated for the narcotic-tolerant patient). This author has found that the Medfusion 2010 pump does not seem to be affected by the magnet as long as it mounted at the end of the scanning table. Other practitioners set up extremely long extension tubing to infusion pumps just outside the door.

In general whether you are administering a general anesthetic or a heavy sedation (either one of which should be performed by the anesthesiology department), there should be a “slave monitor” and large observation windows in the suite that enable you to optionally sit just outside the door and visually observe your patient and his or her vital signs as well as maintain auditory communication via a microphone setup in the suite. During some cases, it may be necessary to remain in the room; these instances might include an inability to see the airway and/or movement of the chest, particularly if the patient has entered the scanner headfirst and/or the patient is a tiny baby or child. If in doubt, insert a laryngeal mask airway (LMA) and maintain spontaneous ventilation with a Jackson-Reese type set up.

Anesthesia in a Therapeutic Radiation Suite
The anesthesiology department will generally be asked to provide anesthesia for two different types of procedures in a therapeutic radiation suite (XRT): sedation for pediatric patients receiving therapeutic radiation, particularly to the head and neck, and for simulations (mostly on pediatric patients). Simulations can take up to two or three hours and are the time when “marking” of radiation fields is done and when “helmets and/or jackets” are molded for radiation treatment. In other words, the areas that are to be radiated are fitted with devices that can be marked by the radiation therapy physician for the exact points to be radiated during treatment. Molding these devices is tantamount to certain types of braces that are made and molded by occupational therapists while lying in the usual hard-fitted headrest; this can be quite painful and long.

Technically the provision of anesthesia for either of these services can be quite tricky. Clearly one cannot be present in the room for actual radiation therapy cases because of the mega-doses of radiation being administered. There is a “slave” monitor available outside where the anesthesia team and the technician watch the patient. Fortunately each treatment (there may be as many as four to five during any one session) takes just minutes, and the anesthesia team checks the patient between each treatment. The general practice (usually only needed for pediatric patients) is to simply access the central venous access port that most of the pediatric patients already have as a part of their ongoing treatment (including chemotherapy) and to use a propofol infusion and routine monitoring, including nasal cannula oxygen with end-tidal CO₂ monitoring. Patients generally wake up almost immediately with cessation of the propofol and are ready for discharge within 15 to 30 minutes.

For simulations the setup can be much more difficult; no two cases are the same. None of the simulation rooms is big enough for an anesthesia machine (one is kept in the hall). Again routine monitoring, including oxygen with end-tidal CO₂ monitoring, is used. If it is felt that the patient will be unable to maintain his or her airway, particularly in the prone position, propofol is given and an LMA is inserted and spontaneous ventilation is restored and maintained with a Jackson-Reese type circuit. Propofol infusion, intermittent fentanyl and midazolam are used as indicated. It is important to note that if the patient is in the prone position, careful measurement of the LMA and any extensions must be calculated, prepared and ready prior to the beginning of the procedure to ensure a proper fit in the rigid headrest.

Jesse A. Leak, M.D., is Clinical Professor, University of Texas Health Science Center at San Antonio, San Antonio, Texas.

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