Off-Site Anesthesia (Anesthesia Text)

General Considerations

Note that all standards must still be met – it is easy to take these for granted when in the OR environment. These standards include centrally supplied oxygen and suction, a full oxygen tank, waste gas scavenging, adequate power supply and lighting, a fully functioning anesthesia machine and supply cart, ready availability of resuscitation equipment, and a means of communicating should an emergency arise

Unfortunately for the anesthesiologist, workspace availability is often reduced. Extra length IV and circuit tubing should be available, as should plenty of padding and other supplies which can facilitate unique patient positioning



Acute contrast media reactions (ACMR) are rare and completely unpredictable, but can be fatal. Serious adverse reactions occur in ~ 1:200 patients, and fatal reactions in 1:100,000. ACMR are anaphylactoid in nature, as they are generally IgE negative. Symptoms will usually develop between 5 and 30 minutes of exposure (if awake, look for nausea, pruritus, diaphoresis, faintness, emesis), and may present as skin changes, airway edema, or cardiovascular collapse

Treat ACMR with epinephrine, corticosteroids, diphenhydramine and famotidine (H1 and H2 blockers), and oxygen, beta-2 agonists, or intubation if necessary

Risk factors include previous reaction, asthma or allergies, current use of beta-blockers or interleukin-2. Patients considered at risk can be prophylaxed with 40 mg prednisone, 50 mg diphenhydramine 50 mg, and 20 mg famotidine the night before and morning of the intervention. Steroids are generally not effective if started within 6 hours of a procedure, however if an emergency case arises, it is prudent to give 200 mg hydrocortisone IV and repeat every 4 hours

Medication Considerations

Dexmedetomidine may be ideal for procedural sedation > 1 hour in which CO2 retention is unacceptable

Radiologic Procedures


Sedation is usually required for uncooperative adults, and children. In adults, use propofol, benzodiazepines, or opiates for sedation as needed. In children, mild sedation can be provided with chloral hydrate (30-50 mg/kg PO or PR, 30-60 mins pre-procedure) or methohexital (25-30 mg/kg PR, 10 mins pre-procedure, lasts ~ 30 mins). Methohexital has the advantage of more rapid onset, however its absorption is unpredictable and can lead to general anesthesia, so must be used with caution

Consider an LMA or endotracheal intubation in children


MRI can be challenging for several reasons – first, other than “open” MRI, the magnet bore does not allow adequate visualization of the patient. Second, ferromagnetic materials must be avoided at all times. Third, MRI relies on radiofrequency pulses which can disturb monitoring devices. Fourth, metallic implants can overhead or become dislodged. ICDs, pacemakers, and PA catheters are absolutely contraindicated. Commercially available MRI-safe intubation equipment allows for induction/intubation in the MRI suite, otherwise patients who require general anesthesia must be intubated elsewhere and brought to the MRI suite. MRIs interfere with EKG and pulse oximetry (MRI-compatible pulse oximeters are available). Temp probes are avoided. Cap all arterial lines to minimize the risk of hemorrhage (ie following inadvertent stopcock manipulation). If the MRI machine had to be turned off, remove the patient beforehand as the MRI bore can become extremely cold. The radiologist may request lower FiO2, as hyperoxia can increase the signal intensity of CSF

Interventional Radiology

Transjugular Intrahepatic Portosystemic Shunt (TIPS)
First, the right IJV is cannulated, after which a trochar is passed through the liver parenchyma and into the portal vein – a stent is then used to keep the diversion open. MAC has been performed successfully, but due to procedure duration, general anesthesia is usually preferred. RSI is indicated in those with ascites, and paracentesis should be considered prior to intubation. Keep in mind that patients may have manifestations of advanced liver disease – coagulopathies, bleeding esophageal varices, ascites, and/or hepatorenal syndrome.

Percutaneous Lung Biopsy

Usually performed under light sedation. Patients are kept prone, and must be immobile during needle placement. Pneumothorax is a common complication, thus these patients should receive a chest X-ray at the completion of the procedure

Percutaneous Tube Insertion

(ex. gastrostomy tube) Usually do not require general anesthesia, although anesthesiology coverage may be required secondary to extensive medical comorbidities

Interventional Neuroradiology

Anesthetic goals revolve around akinesis, which is critical. Tight hemodynamic control, successful coagulation management, and rapid awakening must also be achieved. TIVA or mixed anesthesia can be used. Stimulation is minimal, thus one often does not need to achieve 1.0 MAC. ALL of these patients require urinary catheterization, as contrast dyes are hyperosmolar and lead to substantial diuresis. If anticoagulation is needed, the starting dose of heparin is often 70U/kg (for an ACT of 2-3x normal). Protamine at 1 mg/100U heparin should always be available

Endovascular Embolization

Avoid hypertension at all times. Heparin or argatroban are often required, and eptifibitide may be needed to prevent platelet aggregation. Aneurysm rupture does not lead to blood loss in a closed skull, but rather massive increases in ICP which may require placement of an emergent ventriculostomy as well as hyperventilation, mannitol, diuresis, and/or barbiturate coma.


Requires a second, large-bore IV, cross-matched blood, and usually endotracheal intubation

Balloon Test Occlusion

Temporary occlusion of a particular vessel to determine whether or not it can be sacrificed. To accomplish balloon test occlusion, the vessel of interested is occluded, and blood pressure is dropped for 30 minutes (to minimized collateral flow, thereby providing a margin of safety). These procedures require a completely alert and oriented patient, thus use short-acting agents only. If a neurologic deficit arises, the balloon is dropped and pressures are immediately returned to baseline. Seizures are unlikely, but can develop in these patients, so airway equipment should be readily available


Normally does not require general anesthesia


Prone, percutaneous, normally in osteoporotic women. MAC or GA are both acceptable options. Injection of cement can be painful and may require additional medication

Thrombolysis in Acute Stroke

IV tPA within 3 hours of anterior circulation stroke (6-12 for posterior circulation). Angioplasty may also be done concurrently, in which case GA with intubation is preferred. Time is critical, thus intraarterial catheterization may be delayed until after induction


IR treatment consists of vasodilator infusion, as well as possibly dilation/angioplasty. Patients in vasospasm usually receive “HHH therapy” (hypervolemia, hypertension, hemodilution). Optimizing cerebral perfusion is the goal, and ICP may need to be controlled. Note that intra-arterial papaverine and/or nicardipine may drop blood pressure significantly, thus ionotropes may be necessary

Trigeminal Neuralgia

Treated by percutaneous neurolysis. An electrode is placed in an awake patient, and opiates are avoided because pain symptoms must be accurately elicited. The patient has to be asleep for actual insertion into the ganglion and ablation, as this is excruciatingly painful (propofol usually suffices). Common complications include hypertension (due to painful stimulation), and bradycardia/asystole (oculocardiac reflex)

Radiation Therapy

Painless, but requires absolute akinesis for prolonged periods of time, thus many of these cases require stereotactic frame placement. 2% lidocaine with epinephrine usually suffices for frame placement in adults. Children often require general anesthesia for these procedures – propofol infusion through a Hickman or Broviac catheter (since treatment usually lasts 4 weeks) will often suffice. Nasal prongs or a facemask often suffices

CyberKnife cases must take into account the robotic arm, whose path must be completely clear. CyberKnife and GammaKnife cases take place in rooms with massive, shielded doors, many of which take 30-60 seconds to open in an emergency

Electroconvulsive Therapy

ECT produces a grand mal seizure that produces a brief vagal outburst (can lead to bradycardia and severe hypotension), followed by a 15 second tonic phase and a 45 second clonic phase. The tonic and clonic portions may be accompanied by sympathetic nervous system activation that can last up to 10 minutes and produce significant EKG changes as well as increased ICP. ECT produces profound amnesia and is not painful provided that the patient is adequately paralyzed

Elevated ICP is an absolute contraindication to ECT. These patients will be off of any antiseizure medications, but may be on TCAs or MAOIs, which can potentially lead to hypertensive crises. Risk of aspiration is ~ 1:2000, however there is no data to support premedication with citrate, motility agents, H2 blockers, or PPIs [Stoelting RK. Basics of Anesthesia, 5th ed. Elsevier (China) p. 557, 2007]

Premedication is not indicated. Standard monitors and an IV catheter must be applied before the procedure begins. Anesthesia has traditionally been induced with methohexial (0.5 – 1.0 mg/kg, helps induce seizures) or thiopental, although propofol has recently become more popular. A regimen of lower-dose propofol plus alfentanil or remifentanil can increase seizure duration by 50% without affecting hemodynamics or recovery [Recart A et. al. Anesth Analg 96: 1047, 2003].

Consider prophylactic labetalol in patients with CAD. Place bit blocks while mask ventilating, inflate a blood pressure cuff over an arm and then inject SCh (or mivacurium), thus allowing one limb to serve as a monitor. Hyperventilate just prior to ECT, as CO2 increases the seizure threshold. Following ECT administration, patients are masked until spontaneous ventilation occurs, then placed on their side

Summary of ECT

Summary of ECT:

  1. Beware TCAs and/or MAOIs
  2. Have esmolol or labetalol available
  3. Standard monitors
  4. IV induction (traditionally methohexital 0.5-1.0 mg/kg, propofol acceptable)
  5. Inflate cuff over forearm in excess of SBP
  6. Bite blocks
  7. SCh vs. mivacurium
  8. Hyperventilate
  9. ECT (ok to touch patient with gloved hand, fwd jaw thrust)
  10. Place on side when spontaneous ventilation occurs


Preoxygenate, then give propofol. Avoid etomidate if at all possible because the myoclonus interferes with the EKG and can complicate airway management if necessary


Immersion lithotripsy compresses the venous system (CVP rises ~ 10 mm Hg) and increases the work of breathing (vital capacity and FRC will both drop). Some patients will become hypotensive secondary to vasodilation (due to warm water). Arrhythmias can also occur – in order to minimize their potential the shock waves fire 20 msec after the R wave (total refractory period). Patients with poor cardiac function should NOT undergo ESWL. All patients will develop hematuria, but occasionally they can develop pulmonary contusions or pancreatitis

ESWL causes skin pain, which can usually be managed with short-acting medications. Immersion lithotripsy requires general or regional anesthesia


ERCP and PEG placement can be done with minimal sedation, however the gastroenterologist may prefer general anesthesia. Children will always require GA for these procedures

Dental Procedures

Because the teeth and gums are so highly innervated, stimulation can actually produce arrhythmias. IM ketamine or sevoflurane by mask are the most common induction methods in children. Nasal intubation is only required for procedures of long duration or with significant expected blood loss. Consider giving glycopyrrolate or atropine to reduce secretions. Maintenance with propofol should be considered, as it has an advantageous PONV profile [Apfel CC et. al. NEJM 350: 2441, 2004]