Handbook of Clinical Anesthesia
Anesthesia Provided at Alternate Sites
Alternate sites may be defined as locations that are remote from the main operating room complex (radiology department or endoscopy) (Souter KJ: Anesthesia provided at alternative sites. In Clinical Anesthesia. Edited by Barash PG, Cullen BF, Stoelting RK, Cahalan MK, Stock MC. Philadelphia: Lippincott Williams & Wilkins, 2009, pp 861–875).
- General Principles
- Standards introduced by The Joint Commission (formerly the Joint Commission on Accreditation of Healthcare Organizations, or JCAHO) require that the anesthesia service of a hospital participate with non-anesthesiology departments in setting up a uniform quality of care for patients undergoing sedation in all parts of the hospital.
- The American Society of Anesthesiologists (ASA) has developed practice guidelines for sedation and analgesia by non-anesthesiologists.
- Anesthesiologists undertake most of their training in the operating room surrounded by familiar equipment and staff experienced in the care of anesthetized patients. Away from the operating room, these facilities may not be taken for granted, and a simple three-step paradigm can be used to approach an anesthetic assignment in an alternate site (Table 34-1).
- The Environment.The ASA has developed standards to apply to anesthesia in remote locations (Table 34-2).
- Anesthesia Equipment and Monitors.Anesthesia machines and monitors that remain in an outside location need to be routinely serviced along with the anesthesia equipment used in the main operating rooms. This equipment is not often used on a daily basis, so attention should be paid to the freshness of the soda lime.
Table 34-1 A Three-Step Approach to Anesthesia at Alternate Sites
- Technical Equipment.The complex technical equipment used in alternate sites, particularly in the radiology suites, is often bulky and fixed to the floor. Magnetic resonance imaging (MRI) creates its own environmental concerns related to magnetic fields.
- Procedures(Table 34-3). It is vital that the anesthesiologist understands the nature of the procedure, the position the patient will be in, how painful the procedure is, and how long the procedure will last. Knowledge of these areas allows for the development of an anesthesia plan to provide safe patient care and facilitate the procedure.
- Patients(Table 34-4). Children represent a special group of patients who are more likely to require sedation or anesthesia (pediatric procedural sedation) for various diagnostic and therapeutic procedures.
Table 34-2 American Society of Anesthesiologists Guidelines for Non-Operating Room Anesthetizing Locations
- Anesthesia Care
The Joint Commission defines anesthesia care as the administration of intravenous (IV), intramuscular (IM), or inhalation agents that may result in the loss of the patient's protective reflexes.
Table 34-3 Common Procedures Requiring Anesthesia at Alternate Sites
Table 34-4 Patient Factors Requiring Sedation or General Anesthesia at Alternate Sites
Table 34-5 Definition of General Anesthesia and Levels of Sedation/Analgesia
- Patients who receive anesthesia or sedation at alternate sites should expect the same standard of care that they would receive in the operating room.
- The ASA has published guidelines and standards and definitions of general anesthesia and levels of sedation (Table 34-5).
- At the conclusion of the procedure, patients should recover from anesthesia or sedation in a postanesthesia care unit (PACU) or similar setting supervised by personnel who are trained to take care of unconscious patients and with appropriate monitoring and resuscitation equipment immediately at hand.
III. Radiology and Radiation Therapy
Interventional radiologists now perform an increasing number of procedures that were once in the domain of surgeons. Two important aspects of the radiologic environment are the side effects of contrast media, which are commonly used to enhance radiologic images, and the hazards of ionizing radiation.
- Intravenous contrast agentsare iodinated compounds that are eliminated via the kidneys. Contrast-induced nephropathy is a recognized complication of their use.
- Contrast-induced nephropathy is the third leading cause of hospital-acquired acute renal failure, accounting for about 12% of cases.
- Patients with chronic renal disease, diabetes, and hypovolemia are most at risk for contrast-induced nephropathy; patients taking metformin are at risk of developing lactic acidosis.
- Adequate hydration, monitoring of urine output, and the use of low-osmolarity and non-ionic contrast media help reduce the risk.
- Contrast-induced nephropathy can be prevented by the use of adequate hydration and sodium bicarbonate infusions 1 hour before the procedure. (Dopamine and fenoldopam have not been shown to be effective.)
- Protection from Ionizing Radiation.Patients, physicians, and other health care workers are frequently exposed to ionizing radiation, usually in the form of x-rays. With the routine use of a lead apron, protective goggles, and a thyroid shield, exposure to radiation can be kept to a low level.
- Specific Radiologic Procedures
Cerebral and spinal angiography cause minimal discomfort and may be performed under local anesthesia with or without light sedation administered by non-anesthesiologists. Patients are required to remain completely motionless during these procedures.
- Interventional Neuroradiology.Endovascular treatment of intracranial aneurysms with detachable platinum coils has become an acceptable alternative to surgery for reducing the risk of spontaneous recurrent hemorrhage after subarachnoid hemorrhage. Endovascular treatment avoids the need for craniotomy and reduces the cognitive impairment and frontotemporal brain damage associated with craniotomy. Patients with arteriovenous malformations (AVMs) are increasingly being treated endovascularly.
- Anticoagulationis required during and up to 24 hours after interventional radiologic procedures to prevent thromboemboli.
Table 34-6 Complications of Interventional Neuroradiologic Procedures
- Complications(Table 34-6)
- Anesthetic Technique.General anesthesia is usually conducted with endotracheal intubation and intermittent positive-pressure ventilation, although the laryngeal mask airway (LMA) is a suitable alternative to an endotracheal tube. Propofol and thiopental are the most commonly used induction agents.
- Invasive monitoring is used less often in patients undergoing interventional neuroradiologic techniques than in those having neurosurgical procedures.
- Controlled hypotension is often requested to facilitate embolization of AVMs.
- Certain procedures require patients to be awake for at least part of the procedure. A “sleep–awake–sleep anesthetic technique” using a propofol infusion allows the patient to be rapidly woken up for appropriate neurologic testing, and after this is complete, the patient is resedated or anesthetized while the definitive procedure is carried out.
- Computed Tomography, Radiofrequency Ablation, and Magnetic Resonance Imagingare used for a wide array of diagnostic imaging procedures and an increasingly large number of therapeutic procedures, such as aspiration of masses and needle placement for nerve blockade. The procedures are similar in that they are relatively painless and most adults can tolerate them without the need for sedation or anesthesia. There is, however, an absolute requirement for the patient to remain motionless while the study is being performed. Children and adults with a variety of psychological or neurologic disorders may require sedation or anesthesia to allow them to tolerate the procedures (see Table 34-4).
- Computed Tomography (CT).Modern CT scanners obtain a cross-sectional image in just a few seconds, and spiral scanners can image a slice of the body in less than 1 second, minimizing the problems associated with motion artifacts.
- Radiofrequency Ablation (RFA).Percutaneous RFA is performed in the radiology suite for treatment of primary and metastatic hepatic tumors, including tumors of the lung, adrenal gland, kidney, breast, thyroid, prostate, and spleen.
- The majority of these procedures are tolerated without sedation. (Percutaneous RFA of pulmonary lesions requires conscious sedation or general anesthesia.)
- The presence of a cardiac pacemaker is an absolute contraindication to percutaneous RFA of lung lesions because surrounding tissues heat up.
- Magnetic Resonance Imaging.Deaths and adverse outcomes in MRI scanners are entirely caused by the presence of ferrometallic foreign bodies such as cerebral aneurysm clips or implanted devices such as pacemakers.
- Before entering the vicinity of the magnet, patients and staff members must complete a rigorous checklist to make sure they have no ferrometallic objects in their bodies.
- Ferromagnetic anesthetic gas cylinders become potentially lethal projectiles.
- Standard pulse oximeters work in the MRI scanner but have been reported to produce burns. Nonferrous or fiberoptically cabled pulse oximeters should be used. The electrocardiogram is sensitive to the changing magnetic signals, and it is nearly impossible to eliminate all artifacts. Non-invasive blood pressure monitors and transducers for invasive pressure monitoring are available. In the absence of MRI-compatible monitors, long sampling tubes can be connected to standard capnographs and anesthetic agent monitors.
- Resuscitation attempts should take place outside the scanner because laryngoscopes, oxygen cylinders, and cardiac defibrillators cannot be taken close to the magnet.
- Anesthetic Techniques.Fourteen percent of adult patients require some form of sedation to tolerate
MRI scanning. In most cases, it may be provided as either oral sedation with benzodiazepines or IV sedation administered under the supervision of a radiologist.
- Anesthesiologists are usually only involved in more complex cases, such as patients with obesity, obstructive sleep apnea, increased intracranial pressure, movement disorders, developmental delays, or the potential for a difficult airway.
- Most children younger than age 5 years and many up to the age of 11 years require sedation or general anesthesia to tolerate MRI and CT scanning.
- Radiation Therapy.Two different types of radiation therapy commonly require anesthesia care: external-beam radiation treatments (usually used for children with malignancies) and intraoperative radiation of tumor masses that cannot be completely resected.
- Patients with central nervous system tumors should be assessed for signs of increased intracranial pressure.
- Many children receive cytotoxic or immunosuppressive chemotherapy as well as radiotherapy. This may result in increased risk of sepsis, thrombocytopenia, and anemia.
- General anesthesia or deep sedation techniques with propofol is preferable to prevent patient movement (Table 34-7).
- Portable monitors and methods for delivery of oxygen and agents to maintain general anesthesia during transport are all required.
- After treatment, patients must be transported back to the operating room for surgical closure.
Table 34-7 Goals of Anesthetic Management of Pediatric Patients Undergoing Radiation Therapy
Table 34-8 Interventions in the Cardiac Catheterization Laboratory
- Cardiac Catheterization (Table 34-8)
- Cardiac catheterization is performed in children with congenital heart disease for both hemodynamic assessment and interventional procedures. Patients often present with cyanosis, dyspnea, congestive heart failure, and intracardiac shunts.
- Hypoxia, hypercarbia, and sympathetic stimulation as a result of anxiety may all exacerbate cardiopulmonary abnormalities.
- In patients with a patent ductus arteriosus, high oxygen tension may lead to premature closure and should be avoided. Prostaglandin infusions are often used to maintain duct patency.
- Meticulous attention must be paid to preventing air bubbles entering IV lines because they may cross to the arterial circulation via a right-to-left shunt.
- General anesthesia is necessary when children cannot tolerate sedation techniques, when a child has significant cardiac or other morbidity, and when the procedure involves severe hemodynamic disturbances such as ventricular septal defect occlusion. Ketamine is useful in children with myocardial depression and can be used as an infusion together with propofol.
- Electrophysiologic Procedures (EPs).EP studies and ablation of abnormal conduction pathways are performed increasingly for treatment of arrhythmias caused by aberrant conduction pathways.
- Volatile anesthetics and propofol have been shown not to interfere with cardiac conduction during these procedures.
- EP studies are lengthy and may be painful; children usually require general anesthesia.
- Automatic implantable cardiac defibrillatorsare usually implanted in the EP laboratory under general anesthesia or sedation rather than in the operating room.
Transthoracic cardioversion is an accepted, often used treatment for atrial fibrillation (AF) and atrial flutter.
- Two strategies are used to prevent thromboembolism after cardioversion in patients who have been in AF for longer than 48 hours. The conventional approach is to initiate anticoagulation 3 weeks before cardioversion, usually with Coumadin, and to continue it for 4 weeks after cardioversion.
- Transesophageal echocardiography(TEE) has been recommended to determine whether patients are at low or high risk of thromboembolism. In low-risk patients, the dose of anticoagulants can be reduced.
- Anesthetic Technique.Cardioversion is a brief but distressing procedure and should be carried out using sedation. The usual anesthetic technique for cardioversion is a small bolus of IV induction drug (propofol, etomidate, midazolam).
- Propofol provides a more rapid recovery than midazolam after cardioversion in elderly patients.
- A combination of propofol sedation together with an LMA may be used when TEE is performed before cardioversion.
Gastroenterologists are increasingly using propofol sedation techniques for upper and lower endoscopies (Table 34-9). The American Gastroenterological
Association recommends appropriate training for endoscopists in sedation techniques and involvement of an anesthesiologist in selected patients.
Table 34-9 Common Gastroenterology Procedures
- Upper gastrointestinal endoscopyis tolerated without sedation in the majority of patients. In the rest of patients, conscious sedation is usually sufficient.
- Endoscopic retrograde cholangiopancreatography (ERCP)is important in the diagnosis and treatment of biliary and pancreatic diseases.
- Patients usually experience discomfort during ERCP, particularly with instrumentation and stenting of the biliary and pancreatic ducts. Conscious or deep sedation techniques are recommended.
- If sphincter of Oddi manometry is being performed, opioids, glycopyrrolate, atropine, and glucagon should be avoided because they alter sphincter tone.
- Patients presenting for emergency ERCP may have significant comorbidities, including acute cholangitis with septicemia; jaundice with liver dysfunction; coagulopathy and bleeding from esophageal varices resulting in hypovolemia; and biliary stricture after major hepatobiliary surgery, including liver transplantation.
- Antispasmodics (IV hyoscyamine) decrease the incidence of spasm but may result in sinus tachycardia.
- Transjugular intrahepatic portosystemic shunt(TIPS) connects the right or left portal vein through the liver parenchyma to one of the three hepatic veins. The purpose is to decompress the portal circulation in patients with portal hypertension.
- The TIPS procedure causes minimal stimulation, lasts between 2 to 3 hours, and may be performed under sedation or general anesthesia.
- Patients presenting for a TIPS procedure generally have significant hepatic dysfunction and require careful preoperative assessment (Table 34-10).
VIII. Electroconvulsive Therapy (ECT)
Electroconvulsive Therapy is used to treat depression, mania, and affective disorders in patients with schizophrenia as well as a number of other psychiatric disorders. Typically, ECT is performed three times a week for six to 12 treatments followed by weekly or monthly maintenance therapy to prevent relapses.
- Physiologic Response to Electroconvulsive Therapy(Table 34-11).
Table 34-10 Preoperative Considerations in Patients Presenting for the Transjugular Intrahepatic Portosystemic Shunt Procedure
Table 34-11 Physiological Responses to Electroconvulsive Therapy
- Anesthetic Considerations
- Patients with depression presenting for ECT are often elderly with a number of coexisting conditions, so a thorough preoperative assessment and work-up should be performed before the patient begins treatment. Patients may be taking a variety of drugs (e.g., monoamine oxidase inhibitors), which can have important interactions with anesthetic agents.
- The anesthetic requirements for ECT include amnesia; airway management; prevention of bodily injury from the seizure; control of hemodynamic changes; and a smooth, rapid emergence.
- Propofol is effective at attenuating the acute hemodynamic responses to ECT, and recovery is rapid. Propofol has anticonvulsant effects, although seizure duration is usually acceptable with a small dose (0.75 mg/kg).
- The short-acting opioids alfentanil and remifentanil can be used to decrease the dose of induction drug and prolong seizure duration without reducing the depth of anesthesia.
- Muscle relaxants are used to prevent musculoskeletal complications such as fractures or dislocations during the seizure. Succinylcholine 0.75 to 1.5 mg/kg is the most commonly used agent and is preferable to the longer acting nondepolarizing agents.
- Before inducing the seizure, a bite guard is placed to protect the teeth.
- In younger patients, 15 to 30 mg of IV ketorolac helps to reduce ECT-induced myalgia.
- The parasympathetic effects of ECT (salivation, transient bradycardia, asystole) may be prevented by premedication with glycopyrrolate or atropine.
- Labetalol (0.3 mg/kg) and esmolol (1 mg/kg) both ameliorate the hemodynamic responses, although esmolol has a lesser effect on seizure duration than labetalol, controlling blood pressure without affecting seizure duration. Clonidine and dexmetomidine (1 µg/kg over 10 minutes) administered just before induction of anesthesia are effective in controlling blood pressure without affecting seizure duration.
- Dental Surgery
General anesthesia may be required during more complicated or prolonged cases and when patients are uncooperative, phobic, or mentally challenged.
- Patients with Down syndrome are commonly encountered, and the anesthesia team should be aware of their possible cardiac abnormalities, including conduction abnormalities and structural defects; the risk of atlanto-occipital dislocation; and a variety of potential airway problems, including macroglossia, hypoplastic maxilla, palatal abnormalities, and mandibular protrusion.
- If the patient is positioned head up in the dental chair, vasodilation and myocardial depressant effects of anesthetics can be pronounced, especially in patients with cardiovascular diseases.
- Anesthetic Management
- Ketamine is a useful induction drug. Doses are 1 to 2 mg/kg IV, 5 to 10 mg/kg orally, and, 2 to 4 mg/kg IM with an onset time of 5 to 10 minutes. Oral midazolam is popular. EMLA cream facilitates the placement of IV lines.
- Tracheal intubation, often via the nasal route, is required to protect the airway, although the LMA has recently been used successfully. The immediate postoperative complications include bleeding, airway obstruction, and laryngeal spasm.
- Transport of Patients
Patients who receive anesthesia or sedation at alternate sites need to be transported to the PACU at the end of the procedure, which may be some distance away. During transport, the patient should be accompanied by a member of the anesthesia team, who should continue to evaluate, monitor, and support the patient's medical condition.
Editors: Barash, Paul G.; Cullen, Bruce F.; Stoelting, Robert K.; Cahalan, Michael K.; Stock, M. Christine
Title: Handbook of Clinical Anesthesia, 6th Edition
Copyright ©2009 Lippincott Williams & Wilkins
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