Anesthesia for therapeutic and diagnostic procedures

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SECTION XIII

Anesthesia for therapeutic and diagnostic procedures

A Brachytherapy

1. Introduction

    Palladium-103 prostate implants are being used for brachytherapy as an optional treatment for prostate cancer. The sources are permanently implanted directly into the tissue. The seeds are encased in a lead-lined cartridge that attaches to lead-lined placement needles. The seeds are placed by the radiation oncologist through these needles into the prostate through the perineum. Placement is guided by ultrasonography.

2. Preoperative assessment and patient preparation

a) The treatment is performed in the radiation oncology department.

b) Each patient is prescreened and admitted as an outpatient through the short stay unit.

c) The procedure lasts a maximum of 2 hours.

d) Patients may undergo a bowel preparation at home before the procedure.

e) An 18-gauge, 2-inch angiocatheter is placed before the procedure.

f) Each patient will require intravenous (IV) antibiotics before the procedure. One gram of cefazolin (Ancef) is required. If the patient has an allergy to penicillin, then clindamycin (Cleocin), 600 mg, is administered.

3. Room preparation

    Required monitoring equipment, anesthesia, and airway supplies are provided.

4. Anesthetic technique

a) Anesthesia is usually maintained by spinal anesthesia. A minimal T8 level is desired. If the patient is required to have consecutive treatments, an epidural anesthetic may be placed.

b) Sedation is given as needed.

c) The patient is placed in a lithotomy position for the procedure. A Foley catheter is inserted with Hypaque in the balloon. An ultrasound probe and perineum template are placed before needle placement.

d) The time of treatment is the time of radiation. Everyone must leave the room. Visual contact is always present through monitors. Treatment time is usually 5 to 15 minutes.

5. Postoperative implications

a) Radiation precautions

(1) Occasionally, seeds can become dislodged from the implanted tissue. Therefore, dressings and linens should not be removed from the room until they have been checked and cleared by the oncology physicist.

(2) If a seed is discovered, do not touch it with your hands. Use long forceps to place it in a lead storage container.

(3) Some seeds may pass in the urine for the first few days. Therefore, urine should be strained before being discarded.

(4) Pregnant personnel are not to provide anesthesia for these patients.

(5) All personnel remaining in the room during the procedure should have proper badges. No person or material should leave the room without being surveyed with a Geiger counter.

B Computed tomography

1. Introduction

    Computed tomography (CT) uses x-rays generated from a rotating anode x-ray generator. The patient is placed supine on a flat, wheeled platform and moved inside the scanning gantry. X-rays are then projected through the patient at different angles. The X-rays penetrate tissues differently according to the atomic numbers of the atoms within the tissue. The diagnostic quality of a CT scan is enhanced with the injection of IV contrast media (ICM). Contrast media containing iodine may be administered to the patient enterally or parenterally to further attenuate the x-ray beam to enhance the images for CT vascular or gastrointestinal studies.

2. Anesthetic technique

a) CT scans require that the patient remain as motionless as possible for several minutes to an hour. Patient motion can produce artifacts in the diagnostic images to be read by the radiologist.

b) Patients should lie on a flat, lightly padded wheeled platform, which is rolled into the short bore scanning gantry of the CT scanner.

c) Although the majority of patients are able to cooperate and tolerate CT, others may not be able to cooperate because of extremes in age, concurrent medical conditions, or mental disability.

d) The CT scan is neither physically invasive nor painful. Patients enter the CT scanner without precautions for ferromagnetic objects as for a magnetic resonance imaging (MRI) scan. CT is more rapidly performed than an MRI scan, especially if a spiral CT scanner is used.

e) The patient may require anesthesia anywhere along the continuum from minimal sedation to general anesthesia.

f) Use of ferromagnetic anesthesia equipment and supplies around the CT scanner is not a concern.

g) A standard anesthesia machine, laryngoscope and blades, and IV infusion pumps can be used as if in the operating room.

h) A laryngeal mask airway (LMA) is an appropriate alternative choice as a minimally invasive and secure airway in the patient without contraindications to its use.

i) Attention should be paid to securing the airway, and the anesthesia breathing circuit, the leads for the electrocardiogram (ECG), the noninvasive blood pressure cuff, the IV line, and the pulse oximeter should extend into the scanning gantry. If the use of general anesthesia is used, it is important to verify the presence of a suction canister with tubing that will reach the patient’s mouth in the event of an emergency. An Ambu bag with appropriately sized face mask should also be present.

j) The anesthesia provider should allow for extra anesthesia circuitry length and electrical monitoring leads lengths because of patient movement that will occur because of intermittent repositioning of the mechanized table that positions the patient within the scanning gantry.

k) Sedation can be performed with a variety of agents, including midazolam, chloral hydrate, diazepam, or propofol.

l) General anesthesia can be performed with total IV anesthesia (TIVA), such as with IV propofol, or with inhalation agents.

m) All personnel must be aware of the use of ionizing radiation during the CT scan and should take precautions to be shielded from any exposure to the radiation.

n) Radiation protection can be accomplished with the use of a lead glass barrier, a lead apron, a lead thyroid collar, and lead-glass safety glasses. Radiation dose badges that attach to the clothing are available.

o) ICM can cause an unexpected allergic reaction in some patients, varying from itching with hives to severe, life-threatening anaphylactoid and anaphylactic reactions that have led to patient death.

p) ICM can also cause renal toxicity as well as local tissue sloughing and necrosis if the ICM extravasates from the vein into the surrounding tissue.

q) The anesthesia provider will be involved with patient care related to ICM extravasation and should be familiar with treatment protocols to minimize patient morbidity, as shown in the following box.

Considerations and Treatment Protocols for Intravenous Contrast Media Extravasation Prevention

Considerations

• Use IV catheters (as opposed to metal needles or butterfly needles).

• Avoid use of the same vein if the first attempt at IV catheterization was missed.

• Ensure that the IV catheter is patent and is free flowing.

Treatments

• Attempt to aspirate as much ICM as possible.

• Elevate the affected limb.

• Apply ice packs for 20 minutes to 60 minutes until swelling resolves.

• A heating pad may be necessary in place of ice for swelling.

• Observe the patient for possible tissue damage related to continual contact with ice or heat.

• Observe the patient for 2 to 4 hours before discharge; consider medical or surgical consultation if necessary.

ICM, Intravenous contrast media; IV, intravenous.

C Gastroenterologic procedures: Colonoscopy, esophagogastroduodenoscopy, and endoscopic retrograde cholangiopancreatography

1. Introduction

    Endoscopy for gastrointestinal procedures is the use of a flexible fiberoptic endoscope that transmits brilliant, coherent, high-resolution, magnified, direct visual images to the operator. The operator can then examine, biopsy, dilate, or cauterize portions of the gastrointestinal tract. The endoscopist may pass accessory devices down the endoscope such as biopsy forceps, dilation devices, cytology brushes, measuring devices, needles for injection, Doppler probes, ultrasound probes, and probes to measure electrical activity and pH. Even foreign bodies may be removed with the aid of a snare passed through an endoscope.

2. Procedures

a) A colonoscopy allows total diagnostic visualization of the mucosa of the tortuous colon from the anus to the cecum.

b) An upper endoscopy, such as an esophagogastroduodenoscopy (EGD), is an accurate way for the operator to evaluate the mucosa of the esophagus, stomach, and duodenum.

c) Endoscopic retrograde cholangiopancreatography (ERCP) is used for the diagnosis of obstructive, neoplastic, or inflammatory pancreatobiliary structures.

d) Endoscopy for gastrointestinal procedures may be performed by a gastroenterologist, a general surgeon, a family practitioner, or a proctologist.

e) The endoscope is passed into the gastrointestinal tract with the aid of lubricant.

f) The endoscope has controls to change the direction of the flexible tip, allow flushing with water, apply suction, or insufflate air or carbon dioxide within the portion of the gastrointestinal tract being observed.

3. Anesthetic technique for colonoscopy

a) Because of the expectations of patients, endoscopically caused discomfort, and the desirability for no patient movement, moderate sedation, deep sedation, and, in some cases, general endotracheal anesthesia are used.

b) A proper preanesthetic assessment of the patient should be performed, focusing on the areas of age, ability to cooperate, level of anxiety, mental disability, allergies, fluid status, laboratory electrolyte values, cardiac history, hypertension, bleeding history, clotting status, respiratory status, obesity, drug and alcohol abuse, gastroesophageal reflux, and pregnancy.

c) Patients should adhere to proper NPO (nothing by mouth) guidelines.

d) Bacteremia is possible as a result of endoscopic procedures.

e) Necessary medications may be given, such as cardiac medications, antihypertensives, and antibiotics.

f) Preemptive analgesia with gargled flavored viscous Xylocaine helps patient acceptance of the procedure.

g) Moderate sedation is usually accomplished with the short-acting sedatives midazolam or propofol and analgesics such as remifentanil, alfentanil, or fentanyl.

h) Deep sedation can be achieved with titration of propofol until effective along with an analgesic medication. Upper endoscopy may necessitate the use of any antisialagogue such as glycopyrrolate.

i) Colonoscopy requires thorough cleansing of the lumen of the colon of fecal material. The colon may be partly prepared with a cleansing enema. Full preparation of the colon is accomplished commonly with orally administered balanced electrolyte solutions in a volume of up to 4 L.

j) After the preparation, abdominal cramping, diarrhea, weakness, and nausea can occur. Patients who arrive for the procedure require reassessment and the insertion of an IV catheter with IV fluid, usually lactated Ringer’s solution or normal saline.

k) Conventional monitors, including pulse oximeter, noninvasive blood pressure monitor, and ECG, are attached.

l) The patient is supplied with oxygen through a disposable nasal cannula or disposable face mask. The procedure is usually performed with the patient positioned in a lateral decubitus position with the body flexed, the head and back bent downward toward the knees, and the legs bent upward toward the abdomen.

m) Patient anxiety, distention because of insufflation, and acute discomfort during the maneuvering of the endoscope usually necessitate the administration of deep sedation or a general anesthetic in some cases.

n) Strong vagal nerve stimulation can occur as a result of distention of the colon. This may cause hypotension, bradydysrhythmia, and ECG changes.

4. Anesthetic technique for EGD

a) EGD requires a general patient assessment with special emphasis on any cardiac history, hypertension, bleeding disorders, postoperative nausea and vomiting (PONV), dysphagia, and gastroesophageal reflux.

b) The patient should be NPO according to guidelines. Most patients are able to have EGD performed with a spray or gargle of topical anesthetic such as Cetacaine, benzocaine, or 4% lidocaine liquid.

c) Rapid absorption of highly concentrated local anesthetics, applied topically over highly vascular and absorptive mucosal tissues, can lead to possible toxicity reactions whose symptoms could be masked while the patient is receiving sedative anesthesia.

d) Topical benzocaine can pose a small risk of methemoglobinemia if overused.

e) An IV catheter is inserted, with fluids such as lactated Ringer’s solution or normal saline attached.

f) The patient is connected to standard monitors. Oxygen can be supplied through a disposable nasal cannula or a disposable face mask. EGD is generally performed with the patient positioned supine.

g) After the patient is adequately sedated, the operator inserts a hollow oral airway gently into the patient’s mouth, and the endoscope is advanced through this airway, allowing direct visualization of the larynx, hypopharynx, esophagus, and stomach, and through the pylorus into the duodenal bulb.

5. Anesthetic technique for ERCP

a) ERCP requires thorough assessment of the patient, including a review of laboratory values of a complete blood count, serum liver chemistries and amylase or lipase levels to evaluate liver function, and clotting studies.

b) Patients should also be evaluated for anticoagulant medications, bleeding history, and prosthetic heart valves.

c) Allergies should be evaluated, especially those to iodinated contrast media.

d) Patients who require ERCP are usually more ill than patients seen routinely for colonoscopy or EGD.

e) The patient should be NPO according to guidelines.

f) IV access is obtained, and fluid is administered.

g) Standard monitors are applied, and oxygen is supplied to the patient via a disposable face mask.

h) The procedure requires that the patient be in a prone or slightly left lateral decubitus position.

i) Deep sedation is generally required, although painful or complex ERCP may require general anesthesia.

j) Pediatric endoscopy has been performed with patients under deep IV sedation with agents such as propofol when the patient will allow placement of the IV catheter and under general endotracheal anesthesia.

k) These procedures can cause bowel rupture or duct rupture. One should be ready with immediate airway and hemodynamic support as necessary along with monitored emergency transport to the operating room for surgical intervention.

6. Postoperative implications

a) Postprocedure morbidity differs with each of the described procedures. All patients should be monitored in a postanesthesia care area until they have recovered from the sedation or general anesthetic.

b) Patients having colonoscopy frequently complain of intestinal or abdominal pain immediately after the procedure caused by insufflation during the examination. Rectal bleeding, PONV, and hypotension may also be seen. Administration of a bolus of IV fluids along with an IV antiemetic agent, such as ondansetron, dolasetron, or granisetron, is indicated.

c) EGD morbidity relates to bleeding, PONV, aspiration, dysphagia, and hypotension. Treatments such as those used for colonoscopy may be indicated.

d) ERCP morbidity relates to possible reactions to iodinated contrast media. Patient reactions can be mild (e.g., PONV, pruritus, diaphoresis, flushing, or mild urticaria), moderate (e.g., faintness, severe vomiting, profound urticaria, mild bronchospasm, mild hypotension, mild tachycardia, or bradycardia), or severe (e.g., hypotensive shock, angioedema, respiratory arrest, cardiac arrest, convulsions, or death). PONV can be treated as described previously.

D Interventional radiology, radiotherapy, stereotactic radiosurgery, and interventional neuroradiology

1. Introduction

    Interventional radiology (IR) involves minimally invasive procedures and therapies performed by radiologists, especially in patients at high medical risk. Major IR therapies include angiography, embolization of blood vessels such as arteriovenous malformations or for epistaxis, delivery of chemical or physical vascular occlusive devices, removal of thrombi, ablation of aneurysms, and angioplasty of blood vessels with stent placement.

    Gamma radiation is used for radiotherapy and radiosurgery. The gamma radiation is introduced to the patient by the use of either a Gamma Knife or a CyberKnife. The CyberKnife therapy delivers a sequence of many hundreds of gamma beams to the cancerous tumor from many different directions. Gamma Knife therapy delivers gamma radiation to the cancerous tumor simultaneously in a single dose.

    Interventional neuroradiology (INR) is used for diagnosis and treatment of central nervous system (CNS) diseases endovascularly to deliver therapeutic medications or devices. Digital subtraction angiography first uses an original angiograph of the blood vessels to be studied. Then a contrast medium is injected into the same blood vessels, and opaque structures such as bone and tissues can be digitally subtracted or removed from the angiographic image, leaving a clear picture of the blood vessels.

    Improvements in vascular access techniques, new thin and flexible catheters and guidewires, and the development of innovative coils and therapeutic medications have made new treatments possible. Conditions that once required extensive surgery with accompanying patient morbidity and mortality can now be performed less invasively. Some major procedures performed with INR are mechanical or chemical removal of emboli or thrombi that cause stroke, the physical occlusion of malformed vascular structures such as an arteriovenous malformations with chemicals or flow-directed balloons, dilation of stenotic blood vessels, and embolization (blocking blood flow) of cerebrovascular aneurysms using catheter-deployed coils.

2. Anesthetic technique

a) As skills, techniques, and technology progress, more procedures will be performed with radiation or under radiological guidance.

b) These procedures all require the absolute immobility of the patient, with periods of controlled apnea, which assist in the viewing or treatment of the targeted area of the patient, especially during whole-body therapeutic radiation treatment.

c) These procedures are also time consuming, taking up to several hours to complete. Procedures may be necessary in patients within a wide range of ages (infant to geriatric) and with significant coexisting disease.

d) A thorough preanesthetic assessment is imperative.

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