Anesthesia at RemoteLocations

Dr Abdollahi

Remote anesthesia

Anesthesiologists are increasingly being asked to provide anesthetic care in locations outside of the OR.

It is the responsibility of the anesthesiologist to ensure that the location meets the ASA guidelines for safety.

Locations

1. Radiology suites (MRI, CTSCAN) 2. cardiac catheterization laboratories3. Psychiatric units4. Radiation therapy 5. Gastroentrology6. Pulmonary medicine7. Urology (ESWL)8. General dentistry

Anesthesiologists must maintain the same high standard of anesthetic care provided in the operating suite.

Large, mobile pieces of radiologic equipment, radiation hazards, intense magnetic fields, paramedical personnel not familiar with the anesthesia team, and other factors may make the delivery of quality anesthetic care problematic.

Remember that the key to efficient and safe remote anesthetic relies on open communication between the anesthesiologist and non-operating room personnel

1994 Guidelines for non-operating room anesthetizing locations. Reliable oxygen source with backup. Suction source. Waste gas scavenging. Adequate monitoring equipment. Self-inflating resuscitator bag. Sufficient safe electrical outlets. Adequate light and battery-powered backup. Sufficient space. Emergency cart with defibrillator, emergency drugs, and

emergency equipment. Means of reliable two-way communication. Compliance with safety and building codes.

Remote monitoring

Qualified anesthesia personnel must be present for the entire case.

Continuous monitoring of patient’s oxygenation, ventilation, circulation, and temperature.

Oxygen concentrations of inspired gas: low concentration alarm.

Blood oxygenation: pulse oximetry. Ventilation: end-tidal carbon dioxide detection and

disconnect alarm. Circulation: EKG, ABP (q 5min), invasive BP, and

oximetry.

MONITORING

1. Oxygenation

2. Ventilation

3. Circulation

4. Temperature

Anesthesia techniques used in non-operating room anesthetizing locations range from no anesthesia, to sedation/ analgesia, to general anesthesia.

RADIOLOGY SUITE

Radiologic procedures that may require sedation/analgesia include a number of imaging modalities such as radiology,

ultrasonography, CT, and MRI, as well as various interventions that may be directed by the imaging modalities.

Intervention

Percutaneous drain placement, nephrostomy tube placement, percutaneous placement of feeding tubes, placement of intravascular access catheters, thrombolysis, dilation of stenotic vessels, embolization of tumors or arteriovenous malformations (AVMs), Tissue biopsy specimens may be obtained under radiologic guidance and some conditions may be treatable in the radiology suite. some solid tumors may be treated by guided tissue ablation. Painful metastases may be treated by guided radiofrequency (RF) ablation. Cerebrovascular lesions may be treated endovascularly with guidance by digital subtraction angiography. Advances in imaging capability, as well as the availability of advanced endovascular devices and RF probes, has increased the use of radiology suites and increased the demand for anesthesia services in these areas .

General consideration

Medical history Immobile Claustrophobia Environment (crowded, Bulky radiology

equipment ,high voltage ,change of position ) Lack of gas scavenging

Radiation Safety

Radiation exposure is potentially harmful both in terms of its somatic effects during an exposed individual's lifetime (e.g., production of leukemia) and in terms of genetic injury resulting in fetal abnormalities caused by damage to the gonadal cells or developing fetus.

The maximal permissible radiation dose for occupationally exposed persons is 5O millisieverts (mSv) annually, a lifetime cumulative dose of 10 mSv x age, and monthly exposure of 0.5 mSv for pregnant women.

Radiation exposure can be limited by wearing appropriate lead aprons and thyroid shields, using movable leaded glass screens, and using innovative techniques such as video monitoring and remote mirroring of monitor data to allow remote conduct of anesthesia when appropriate and required for the safety of anesthesia personnel. Clearly, open communication between the radiology and anesthesia teams is essential to minimize radiation exposure. Adequate warning of initiation of imaging by the radiology team allows the anesthesia personnel to take appropriate precautions in a timely fashion

Iodinated Contrast Media

Iodinated contrast agents are often used in diagnostic and therapeutic radiologic procedures to assist imaging.

Adverse reactions to contrast media range from mild to immediately life-threatening, and etiologies include direct toxicity,idiosyncratic reactions, and allergic reactions, either anaphylactic or anaphylactoid Crable

Predisposing factors include a history of bronchospasm, history of allergy, underlying cardiac disease, hypovolemia, hematologic disease, renal dysfunction, extremes of age, anxiety, and medications such as ~-blockers, aspirin, and nonsteroidal anti-inflammatory drugs.

Prompt recognition plus treatment of contrast media reactions is important to prevent progression of less severe reactions and lessen the impact of severe reactions.

Treatment

Treatment is symptomatic, for example, oxygen and bronchodilators to treat bronchospasm. Severe or resistant bronchospasm may require treatment with epinephrine. Typically, corticosteroids and antihistamines are given to symptomatic patients under the assumption that the etiology is immunologic.

Prophylaxis

pretreatment with prednisolone, 5O mg 12 and 2 hours before a procedure requiring contrast media, and diphenhydramine, 5O mg immediately before the procedure.

Renal dysfunction is well documented in association with radiologic contrast media, particularly in patients with preexisting renal dysfunction and most especially in patients with preexisting renal dysfunction related to diabetes.

Most cases of new or worsened renal function related to contrast media are self-limited and resolve within 2 weeks.

However, some patients may progress to the point of requiring dialysis.

Recent studies have demonstrated a reduction in contrast media nephrotoxicity by the administration of acetylcysteine.Life- threatening lactic acidosis may develop in non-insulin-dependent diabetic patients who are receiving metformin and have preexisting renal dysfunction if their renal function declines further. Extra care is needed when patients taking metformin receive radiologic contrast media.

Anesthesia in the Radiology SuiteMinimal to moderate sedation/analgesia is the

technique used for most patients undergoing these procedures.

For most adults, combinations of intravenous benzodiazepines and opioids (i.e., titration of midazolam and fentanyl) are sufficient to ensure comfort during the procedure. As noted earlier, the use of more potent anesthetic agents such as propofol, methohexital, and ketamine is best reserved for specialists in anesthesia.However, understanding the procedure in question is important in selection of the appropriate anesthetic technique.

The patient's condition, the anticipated level of stimulation, and patient position during the procedure are all important considerations.

A patient undergoing ultrasound-guided

hepatic biopsy might have ascites, which would render that patient prone to aspiration if sedated, and penetration of the hepatic capsule by the biopsy needle would be anticipated to be quite painful. Such a patient might benefit from general anesthesia rather than sedation/analgesia.

Procedures that might be anticipated to last several hours may best be performed with general anesthesia at the outset rather than late conversion after failure of sedation/ analgesia, when patient access might be limited by catheter placement and radiologic equipment.

Pediatric patients merit special consideration. Some radiologic procedures require patients to remain still for prolonged periods, which may not be possible for infants and children, even with sedation/analgesia. (chloral hydrate orally for radiologic procedures 25 to 5O mg/kg for infants younger than 4 months, 5O mg/kg for older children)

Patients with difficult airways, whether anticipated or not, can be problematic in settings outside the operating suite . I prefer to perform anticipated difficult endotracheal intubations in the operating suite with its improved availability of skilled assistants and specialized equipment. Once the airway is controlled, the patient can be transported to the site of the planned procedure

should it be necessary to perform the procedure outside the operating suite.

MAGNETIC RESONANCE IMAGINGThe most significant risk posed in the MRI suite

is the effect of the magnet on ferrous objects.

MRI

MRI scanning has a number of limitations. Imaging is time consuming, and individual scans may take up to 20 minutes, with an entire examination lasting more than 1

hour.

Switching on and off of the RF generators produces loud noises (>90 dB)

MRI

Hearing protection is mandatory for both the patient and health care personnel who must be present in the scanning room. Heating resulting from the RF energy of nonferromagnetic prosthetic devices has not proved to be a problem. Body surfaces do absorb this RF energy, but it is unlikely that the patient's temperature will increase by more than 1°C.

MRI

The most significant risk posed in the MRI suite is the effect of the magnet on ferrous objects.

Dislodgement and malfunction of implanted biologic devices or other objects containing ferromagnetic material are also real possibilities. Such items include shrapnel, vascular clips and shunts, wire spiral endotracheal tubes, pacemakers,automatic implantable cardioverter-defibrillators (ICDs), mechanical heart valves, and implanted biologic pumps.

MRI

Tattoo ink may contain high concentrations

of iron oxide. Burns at tattoo sites have been

reported after exposure to MRI magnetic fields, but such incidents are very rare and the presence of, for example, permanent eyeliner should not exclude the patient from MRI examination.

Anesthetic Management for MRIAnesthesia in the MRI suite poses several unique problems, including the

following:1. Limited patient access and visibility, especially when the patient must be

placed head first into the magnet2. Absolute need to exclude ferromagnetic components3. Interference/malfunction of monitoring equipment produced by the

changing magnetic field and RF Currents 4. Potential degradation of the imaging caused by the stray RF currents

produced by the monitoring equipment and leads5. The necessity to not move the anesthetic and monitoring equipment

once the examination has started to prevent degradation of magnetic field homogeneity

6. Limited access to the MRI suite for emergency personnel in accordance with the recommended policies noted earlier

A common approach now is to induce anesthesia in an induction area adjacent to the MRI suite outside the magnetic field by using conventional equipment with the patient on a dedicated MRI transport table that is not ferromagnetic.

This transport table is then used to bring the patient into the MRI suite, where anesthesia and monitoring are continued with MRI-compatible devices. The MRI transport table is also used to remove the patient rapidly from the scanner should an emergency arise. This is important because the ferromagnetic equipment used for patient resuscitation by the code team and others must never be brought into the MRI scanner room .

MRI

Because the patient's airway is not easily accessed during the MRI scan and because patient assessment and communication are limited by both the magnet bore in which the patient is placed and the loud noise associated with MRI scanning, deep sedation/analgesia is not advisable. Patients requiring more than moderate sedation/analgesia are probably most safely administered a general anesthetic with airway control by either endotracheal intubation or a laryngeal mask airway (LMA).

MRI Able to obtain images in any plane. Excellent soft tissue contrast. Does not produce ionizing radiation, is non-invasive, and

does not produce biologically deleterious effects. Is often very time-consuming and any patient movement,

including physiologic motion, can produce artifacts. Obese patients can often not fit within the magnet. Hearing protection is mandatory (produces loud noises

>90 dB). Thermal injury has been reported at site of EKG

electrodes and areas where skin contacts the machine. Most significant risk in the MRI suite is the effect of the

magnet on ferrous objects.

MRI, contd. MRI magnet

Contraindications for MRI include: Shrapnel, vascular clips and shunts, wire spiral ETT’s,

pacemakers, ICDs, mechanical heart valves, recently placed sternal wire, implanted biological pumps, tattoo ink with high concentrations of iron-oxide (permanent eyeliner), and intraocular ferromagnetic foreign bodies.

Ferromagnetic items should never be allowed in the vicinity of the MRI magnet, including: scissors, pens, keys, gas cylinders, anesthesia machine, pro-pak monitor, syringe pump, beeper, phone, and steel chairs.

Cards with magnetic strips will be de-magnetized, including credit cards and ID badges.

*There is a yellow line within the MRI room which cannot be crossed with any ferromagnetic materials. Your syringe pump, pen, and monitor can be within this room as long as they are behind this line.

ANESTHESIA FOR INTERVENTIONAlNEURORADIOlOGYInclude embolization of cerebral and dural

AVMs, coiling of cerebral aneurysms, angioplasty of atherosclerotic lesions, and thrombolysis of acute thromboembolic stroke.

These procedures may involve deliberate hypotension, deliberate hypercapnia, or deliberate cerebral ischemia as part of the procedure; a requirement for rapid transition between deep sedation/ analgesia and the awake, responsive state; and severe potential procedural complications.

Anesthetic Management

Preprocedural anesthetic evaluation is similar to that before neurosurgical procedures. Airway examination is important in as much as airway manipulation during the procedure is not possible because of interference with head positioning for imaging. Particularly important is a history of previous experience with radiologic procedures and any history of contrast media reaction. Because bloodpressure management is important for these procedures,preoperative evaluation for hypertension is important, as is good preoperative control of existing hypertension.

Heparin is commonly administered during these procedures, with a target activated clotting time (ACT) of 2 to 2.5 times the baseline value. Deliberate hypotension is frequently used during AVM embolization to decrease flow to feeding vessels, as well as during some trial balloon occlusions. Agents such as esmolol, labetalol, or sodium nitroprusside are all useful in this situation. Deliberate hypertension is called for during cerebral ischemia in an attempt to maximize collateral flow.

Phenylephrine is generally used, both as a bolus and as an infusion titrated to increase systolic blood pressure 30%to 40% above baseline. Close monitoring of ECG parameters for signs of myocardial ischemia is critical in this case. Smooth emergence from anesthesia is important in these patients, who may be prone to device migration or intracranial hemorrhage. Administration of antiemetics before emergence is certainly reasonable, and precautions to avoid coughing andl/bucking" should be taken.

INTERVENTIONAL CARDIOLOGYlnterventional cardiology procedures include

coronary angiography and cardiac catheterization, coronary artery angioplasty/stenting, valvotomy, closure of intracardiac defects, electrophysiologic studies with pathway ablation, and cardioversion.

The usual anesthesia management is by sedation/analgesia, with general anesthesia reserved for sedation failure, uncooperative patients, or those who require airway control to manage respiratory failure.

Anesthetic agents used commonly include fentanyl andmidazolam, sometimes supplemented with propofol.Sedation and analgesia are helpful in reducing the discomfort .

Typical heparin doses range from 2500 to 5000 IV intravenously. For interventional procedures, higher heparin doses (i.e., 10,000 IV intravenously) are given, with a target ACT of over 300 seconds. Patients must be monitored carefully after protamine administration to detect the predictable peripheral vasodilation, as well as less predictable anaphylactic and anaphylactoid reactions or the rare catastrophic pulmonary vasoconstrictive crisis associated with protamine administration.

Heparin are increasingly commonly being administered during interventional cardiac catheterization and have resulted in improved outcomes despite the reduction in heparin dose. Platelet aggregation inhibitors used have included abciximab, ticlopidine, and clopidogrel. Numerous studies have shown the benefits of anti platelet therapy in both acute and chronic coronary syndromes.

A notable side effect of abciximab is elevation of the ACTindependent of heparin.

Coronary artery disease is assessed by detection ofstenoses after injection of contrast medium selectivelyinto each main coronary artery. Stenoses greater than50%to 70%f the normal arterial diameter are consideredhemodynamically significant, although lesser stenosesmay be clinically important. Coronary artery disease isclassified as one-, two-, or three-vessel disease or left maincoronary disease.

after dilation of the stenotic coronary artery, ventricular arrhythmias may develop and require treatment.

pericardial tamponade.

Pediatric Cardiac CatheterizationMedications administered for sedation include

fentanyl, midazolam, propofol, and ketamine.Premedication with midazolam, 0.5 mg/kg

orally, can be particularly helpful. Some evidence has indicated that ketamine can increase oxygen consumption, so care must be taken to ensure that it does not impair diagnostic accuracy.

Hypothermia Arrhythmia Tamponad Bleeding PG

1. Electrophysioiogic Studies and Catheter Ablation of Abnormal Conduction Pathways

2. Pacemaker and Cardioverter- defibrillator implantation

Elective Cardioversion-Elective cardioversion is uncomfortable, and

general anesthesia is required. Many medications have been used, including barbiturates, propofol, etomidate, and

benzodiazepines.

It should be noted that muscle relaxants are not typically needed for this procedure.

ELECTROCONVULSIVE THERAPYIndications for ECT include major depression, mania, certain forms

of schizophrenia, and perhaps Parkinson's syndrome. Pheochromocytoma is a contraindication to ECT. Relative contraindications include increased intracranial pressure, recent cerebrovascular accident, cardiovascular conduction defects, high-risk pregnancy, and aortic and cerebral aneurysms. In these conditions, the risk of the patient's psychiatric illness and the side effects of antidepressant medications must be weighed

against the risk associated with ECT and anesthesia.

Complications

Seizure activity causes an initial parasympathetic discharge manifested by bradycardia, occasional asystole, premature atrial and ventricular contractions, or a combination of these abnormalities. Hypotension and salivation may be noted and then sympatric activity.

EKG change

preexisting arrhythmias, are self-limited

and not in themselves a contraindication to treatment.

ECT has been found to be relatively safe even in high-risk cardiac patients, provided that careful management is provided.

Neuroendocrine responses to ECT include increased levels of stress hormones, including adrenocorticotropic hormone, cortisol, and arginine vasopressin, as well as prolactin and growth hormone.Norepinephrine and epinephrine increase immediately after ECT,and epinephrine levels decrease more rapidly thereafter. Glucose homeostasis is variably affected by ECT.Improvement in control of non-insulin-dependent diabetes is generally noted, whereas hyperglycemia may be seen when the diabetes is insulin dependent.

ECT contd.

What you need: Cart Suction Ambu bag Bite block O2 NC #22g IV Meds: STP, Sux, glyco, and esmolol (Poss. Caffeine) Paper charts: pre-op, OR records, charge sheet, and

PACU order forms

ECT contd. Pre-op the pt. These pt’s have often had this procedure multiple

time, therefore you can use old records as templates. Place IV and give glyco (0.2 mg IV). Give caffeine if the

psychiatrist requests. Treats the bradycardia/ asystole from the initial parasympathetic

discharge from the seizure activity Hyperventilate the pt. with 100% O2. STP Inflate the manual BP cuff in the arm opposite the IV and then

give Sux. Place the bite block. Goal is a seizure 30-60 seconds long. Ventilate until spontaneous respirations return. The parasympathetic discharge is often followed by a

sympathetic discharge associated with HTN and tachycardia. This is treated with esmolol.

Antidepressant Drug TherapyAntidepressants, monoamine oxidase inhibitors

(MAGIs),serotonin reuptake inhibitors, lithium carbonate, or a combination of these drug.

Tricyclic antidepressants block the reuptake of norepinephrine, serotonin, and dopamine into presynaptic nerve terminals, thereby increasing central sympathetic tone. Tricyclic antidepressants have anti. histaminic, anticholinergic, and sedative properties and also slow cardiac conduction. These side effects are less common with the newer types of antidepressant drugs such as trazodone, bupropion, and fluoxetine. The combination of centrally acting anticholinergics, such as atropine,

with tricyclic antidepressants can increase postprocedural delirium.

MAOIs can inhibit hepatic microsomal enzymes. They may interact with opioid analgesics and cause excessive depression. Used concomitantly with meperidine, MAOIs may result in severe, possibly fatal excitatory phenomena.

Lithium carbonate prolongs the action of neuromuscular blocking agents. Elevated lithium levels, higher than the therapeutic range, can prolong the action of benzodiazepines and barbiturates. Patients receiving lithium may demonstrate more cognitive side effects after ECT. The American Psychiatric Association recommends discontinuation of lithium therapy before ECT.

Anesthetic Management of ElectroconvulsiveTherapyAnesthesia and neuromuscular blockade

are necessary during ECT to prevent psychological and physical trauma. Rapid recovery is desirable.

particular attention paid to coexisting neurologic and cardiac disease, osteoporosis and other causes of bone fragility, and medications that the patient may be receiving. The patient

may be a poor historian because of the psychiatric condition, and accompanying caregivers may need to provide the necessary history and assurance of fasting status.

Glycopyrrolate (0.2 mg intravenously), which does not cross the

blood-brain barrier, can reduce the occurrence of bradycardia and the amount of oral secretions associated with ECT, as discussed later. After preoxygenation, anesthesia is administered by peripheral intravenous catheter, and neuromuscular blockade is induced. When relaxation is adequate and satisfactory mask ventilation with oxygen

is ensured, a bite block is placed and a stimulus is delivered to induce the seizure.

If the patient has a hiatal hernia and gastroesophageal reflux, rapid-sequence induction and endotracheal intubation with cricoid pressure may be a reasonable approach. Adequate ventilation is ensured

during the procedure because among other detrimental effects, hypoxia and hypercarbia decrease seizure duration and thus the efficacy of ECT

Many intravenous anesthetics have been used to induce anesthesia for ECT, including methohexital, thiopental, propofol, and ketamine. Methohexital (0.75 to 1.0 mg/kg) is the most commonly used drug for ECT anesthesia and is considered the "gold standard. "Propofol (0.75 mg/kg) was found to reduce seizure duration, which was believed to decrease the efficacy of ECT.

Thiopenta (1.5 to 2.5 mg/kg) avoids pain on injection, but it is associated with more hypertension and tachycardia than propofol .

Etomidate may prolong seizures and recovery, but prolongation of the seizure may be useful in patients in whom seizure duration is deemed too short with other agents. Benzodiazepines have anticonvulsant activity and should be avoided before ECT.

Ketamine has been demonstrated to not increase seizure length or produce excessive postprocedural agitation.

Given the hemodynamic response expected after ECT, ketamine would seem to be a less desirable agent.

Prophylactic medications have been advocated to avoid various side effects of ECT. Transient asystole is rare during ECT, but it may be prevented with anticholinergic pretreatment. Glycopyrrolate is preferred over atropine because glycopyrrolate has no central anticholinergic side effects. In addition, glycopyrrolate is an effective antisialagogue. Both esmolol and labetalol have been successfully used to control hypertension and tachycardia after ECT.Some evidence has shown that esmolol reduces seizure duration.Routine treatment with

esmolol or labetalol is not recommended because the hypertension and tachycardia are usually self-limited, as are premature ventricular contractions. Should treatment be necessary, these drugs can be administered immediately after the stimulus.

Office-based anesthesia ASA and JCAHO guidelines

Employment of appropriately trained and credentialed anesthesia personnel.

Availability of properly maintained anesthesia equipment. Complete documentation of the care provided as required

at other surgical sites. Use of standard ASA monitoring. Provision of a PACU that is staffed by trained nursing

personnel. Availability of emergency equipment. Establishment of a written plan for emergency transport of

the patient to a comprehensive care center if a complication occurs.

Office-based anesthesia, (contd.) Often used for ENT and dental procedures. Patient requires a full preoperative workup. Potentially difficult airways are not good

candidates. Procedures often involve local anesthesia

plus IV sedation or light general anesthesia with a mask or LMA.

Agents of choice include: propofol, sevo, des, and N2O.

Remote recovery care

Patient must be medically stable before transport.

Patient must be accompanied to the recovery area.

Provisions for O2 delivery and monitoring on the transport cart are required.

Appropriate recovery facilities and staff must be provided.