Tuesday, March 23, 2021

Cases Outside the Operating Room Case File

Posted By: Medical Group - 3/23/2021 Post Author : Medical Group Post Date : Tuesday, March 23, 2021 Post Time : 3/23/2021
Cases Outside the Operating Room Case File
Lydia Conlay, MD, PhD, MBA, Julia Pollock, MD, Mary Ann Vann, MD, Sheela Pai, MD, Eugene C. Toy, MD

Case 46
You are scheduled to provide anesthesia for three cases outside the operating room. The first case is a 4-year-old child for an MRI, the second case is an endoscopic retrograde cholangiopancreatography (ERCP) in an adult, and the third case of the day is an electro-convulsive therapy (ECT) for an adult. These cases will all likely be general anesthetics, and all require consideration about the site of anesthesia delivery.

➤ What three factors are common to all cases performed outside the operating room?

ANSWER TO CASE 46:
Cases Outside the Operating Room
Summary: You are asked to provide anesthesia for three very different patients undergoing three different types of procedures in three different locations— radiology, GI, and the induction room (or ECT suite).

Three common factors: (1) Need for equipment and drugs must be anticipated, since these items are not likely to be readily available in the remote site; (2) inexperienced health care personnel unfamiliar with the “ways of the operating room” to be able to provide effective assistance in an emergency; (3) absence of essential equipment such as “piped” oxygen, and sometimes even wall suction.


ANALYSIS
Objectives
1. Understand the unique environment of out of OR cases.
2. Become acquainted with how some of these challenges are met.
3. Understand the unique equipment challenges of MRI anesthesia.


Considerations
Since an MRI can be performed under sedation, if anesthesia services are requested, then there is usually an indication for general anesthesia. Children who are unable to cooperate represent just such an indication. The safest way to care for this child is to provide a general anesthetic using an ETT and an MRI-compatible machine. The child is kept NPO for a suitable period depending on his age, and standard monitors are applied (BP, pulse oximetry, capnography, ECG, and temperature) and must be compatible with the MRI environment. The MRI room is usually cold, but the scanner itself produces heat, so hypothermia is generally not as problematic as in the operating room.

ERCP is a fairly invasive and painful procedure usually performed under general anesthesia. The prone position involves turning the patient after induction, as well as turning the patient’s head to one side to allow entry of the endoscope. Preoperative assessment of neck sideway range of motion is important in anticipation of this positioning.

ECTs are performed in a wide variety of patients using general anesthesia with mask ventilation. Since antidepressant drugs may have some synergies with anesthetic drugs, doses are minimized and reduced on subsequent treatments if possible.


APPROACH TO
Cases Outside the Operating Room

Providing anesthesia outside the operating room suite is challenging for many reasons. The equipment to perform the anesthetic and treat complications must be anticipated, and transported to the distant site. Generally, each institution will set up equipment carts to accomplish this task efficiently. These carts have limited capacity, however, so compromises are made and one doesn’t have all the equipment necessary to deal with any and all potential anesthetic scenarios.

Another challenge is the remote location away from other anesthesia personnel. In an emergency situation having help and equipment is important, so it is easy to see the challenge when those resources are not available. Also, the personnel at the locations away from the operating room may not be familiar with anesthesia services. There may be limited room for equipment in the procedure room and there may be limited understanding of the sequence and timing of events during anesthesia delivery. Communication can help bridging this disconnect, but in the emergency situation the anesthesia provider can be left feeling very much alone.


The MRI Scanner
The magnet in an MRI scanner is a remarkably powerful device. All equipment inside the room housing the MRI must be nonmagnetic (this includes implants within the patient). Stories of intubating stylets hurling as projectiles across the room, or even a metal anesthesia cart with a resident holding on to it are not unheard of. (The resident’s nose was broken, the cart had minor damage, but the MRI was out of service for several months). A second consideration is that the scanner is a long narrow tube. The patient’s airway is inaccessible inside the scanner. Moreover, sudden patient movement can result in injury to the patient.

The anesthetic procedure is dictated largely by the availability (or lack of) equipment compatible with the MRI within a given institution. If the anesthesia machine is not MRI compatible, then it must remain outside the scanner and long breathing circuit tubing will be needed to connect the patient to the machine. First, a choice must be made as to whether to induce the patient on a stretcher outside the MRI room and transfer him/her into the MRI machine while anesthetized, or whether MRI-compatible equipment is available which can allow induction with the patient lying on the MRI. Most institutions currently have devices capable of measuring blood pressure, ECG (including ECG patches), and pulse oximetry probes and devices that are MRI compatible. However, the pulse oximetry devices used in the operating room interfere with the imaging process, and the imaging process interferes with the pulse oximetry.

Securing the airway in the MRI scanner must be done with MRI-compatible laryngoscopes or the patient has to be outside the MRI scanner for intubation. Some institutions have anesthesia machines that are MRI compatible. The presence or absence of an MRI-compatible anesthesia machine is particularly important with respect to ventilatory dead space. Some centers have MRI-compatible machines and therefore the circle system dead space is identical to that in the operating room. However, if there is no MRI-compatible machine, then the anesthesia machine is placed outside the MRI scanner. Dead space ventilation is the space occurring beyond the y-piece of a circle system, so the extensive tubing required to reach from outside to inside the scanner increases dead space ventilation and leads to inaccurate tidal volume measurements. Most Ambu bags are MRI compatible, however don’t forget to have long enough oxygen tubing to reach an oxygen source (which could be an oxygen E-cylinder located outside the MRI) if providing positive pressure breaths inside the scanner. If relying on spontaneous ventilation, there must be some assessment of adequacy of ventilation (ET CO2 monitoring) as well as a plan for positive pressure ventilation if that becomes necessary.

The issue of an MRI-compatible machine is a particular issue when taking care of a child with a small tidal volume. Because the child’s tidal volume is small, any inaccuracies in its measurement represent a larger percentage of the child’s tidal volume. Another option is to use Mapleson circuits (provided the circuit has no magnetic metal) or to provide oxygen by cannula or mask and have the patient spontaneously ventilate. 


The GI Suite
Anesthesia services are most often requested in the GI suite because of patient intolerance to sedation, extensive comorbid diseases, or an anticipated painful or long ERCP. General anesthesia is most often performed for ERCP using standard monitors. The patient may be prone or supine, depending on the preferences of the gastroenterologist. The prone position involves turning the patient after induction as well as turning the patient’s head to one side to allow entry of the endoscope. Preoperative assessment of neck sideway range of motion is important in anticipation of this positioning. The placement and removal of the endoscope can also dislodge the ETT, so careful observation and monitoring for continued ventilation is imperative. An ERCP produces only minor postoperative pain in comparison to other surgeries (if sphincterotomy is performed at the sphincter of Oddi then expect more pain). However, the gas insufflation will often lead to bloating and discomfort post procedure despite the gastroenterologist’s attempts to decompress the stomach. At the conclusion of the procedure, the prone patient is turned supine and then ETT removed when extubation criteria are met.


Anesthesia for Electroconvulsive Therapy
ECTs are performed under general anesthesia with ventilation by mask. Premedication is limited to an antisialagogue (glycopyrrolate), atropine, analgesics, or antihypertesives if appropriate. Caffeine is sometimes administered as a premed to promote longer seizure duration. Benzodiazepines are avoided,
because they raise the seizure threshold. If the patient is on chronic benzodiazepines, then flumazenil may be requested by the psychiatrist to reverse their effects (with the caveat that a benzodiazepine will be given before emergence to prevent excessive patient anxiety). The patient is positioned on the procedure table with standard monitors and an extra BP cuff on the arm opposite the intravenous or on the leg. Sometimes the procedure is performed in the patient’s stretcher.

After preoxygenation, anesthesia is induced with methohexital. The dose of methohexital is titrated so that unconsciousness is attained at the lowest possible dose so as to minimize any elevation of seizure threshold. The dose is often determined by that administered at the previous ECT treatment, or it is reduced if at all possible. Once the patient is unresponsive, the BP cuff on the arm or leg is inflated to a sustained pressure to cut off blood flow and prevent muscle relaxant from paralyzing that limb. A bite
block is placed to protect the patient’s teeth and the patient is hyperventilated to lower the seizure threshold. Succinylcholine is given and twitches monitored. Once there are no twitches an electrical stimulus is applied to the head and a seizure ensues.

The peripheral seizure activity is monitored in the leg with the BP cuff and the central seizure is monitored by EEG strip on the ECT machine. The initial tonic phase of the seizure is accompanied by a parasympathetic surge that usually manifests as bradycardia. The clonic phase follows shortly thereafter. It is conversely accompanied by a sympathetic surge resulting in tachycardia and hypertension. Pharmacologic treatment of these two phases can be employed depending on the comorbidities of the patient. Since the parasympathetic surge is very brief, treatment generally focuses on lessening the sympathetic surge by beta blockers or i.v. antihypertensives.

Once the seizure activity has abated, the patient’s airway is supported until emergence. Analgesics are sometimes given to lessen any myalgias associated with succinlycholine-induced fasciculations. Once the patient is awake and supporting their airway they are transported to recovery.


Comprehension Questions

46.1. Which of the following statements best describes the difference between delivering anesthesia in the OR versus outside the OR?
A. Endotracheal tubes are not used for anesthetics in remote locations.
B. There are always extra personnel to help in remote locations.
C. Equipment must be transported to these locations.
D. Most out of OR procedures can be completed with a regional anesthetic technique

46.2. Which of the following is accurate for anesthesia in the MRI scanner?
A. Standard monitoring equipment will work in the scanner.
B. Hypothermia in the MRI scanner is uncommon.
C. The anesthesia machine is never located outside the scanner.
D. General anesthesia is contraindicated during an MRI.

46.3. Which of the following statements is most accurate regarding ERCP?
A. They are all performed in the supine position.
B. Accidental extubation is uncommon.
C. Patient neck range of motion is only important for intubation.
D. The procedure is painful.

46.4. Which of the following hemodynamic changes are seen with ECT?
A. Hypertension during the tonic phase
B. Tachycardia during the clonic phase
C. Tachypnea during the clonic phase
D. Tachycardia during the tonic and clonic phases


ANSWERS
46.1. C. The need for equipment must be anticipated, and then transported to the appropriate site. Help is not as readily available. The space may be insufficient for the amount of equipment required. The personnel may not be familiar with anesthesia services.

46.2. B. The MRI scanner gets warm during a scan. Special MRI-compatible monitors must be used near the MRI scanner. The anesthesia machine is often located outside the scanner (unless it is a special MRI-compatible machine). General anesthetics are common for MRI scans when anesthesia services are requested.

46.3. D. An ERCP can be performed under sedation, but because it is painful, general anesthesia is often chosen. Movement of the endoscope out of the esophagus can dislodge the ETT. Patient neck range of motion is important for intubation, but in ERCP it is also important to assess because if done in the prone position the head will be turned to the side.

46.4. B. When the electrical stimulus is applied for an ECT, there is an initial parasympathetic discharge manifested by bradycardia during the tonic phase. Upon initiation of the clonic phase, there is a sympathetic discharge manifested by tachycardia and hypertension. The patient is paralyzed and apneic during for the application of electrical stimulus and seizure, and cannot thus become tachypneic.


Clinical Pearls
➤ Anesthesia outside the operating rooms is challenged by the remote location and unique setup of each site.
➤ When giving anesthesia outside the OR, equipment must be transported, and one must be cognizant that the personnel and amount of equipment is limited.
➤ Providing anesthesia in the MRI area presents unique challenges including
ensuring that the equipment and monitoring devices are MRI compatible.
➤ ECT is a wonderful opportunity to provide mask general anesthetics.

References

Gross WL, Gold B. Anesthesia outside the operating room, an issue of anesthesiology clinics. Anesthesiol Clin 2009;27(1). Elsevier Health Sciences.

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