Anesthesia for Electrophysiology Procedures

Acknowledgments

The authors thank Drs. David Callans, Lee Fleisher, and Sean Kennedy for their comments on a draft of this chapter.

In the electrophysiology laboratory, procedures are performed to diagnose and treat abnormal cardiac rhythms. These procedures can be accomplished less invasively and more safely than major surgical procedures that were required in the past, especially with higher-risk, older, and sicker patients. Procedures commonly performed in electrophysiology laboratories to diagnose and treat abnormal cardiac rhythms include catheter-based ablations, device implants, lead extractions, noninvasive programmed stimulations (NIPS), and cardioversions ( Table 11-1 ). A fuller understanding of these procedures and their potential complications will provide a better framework for planning a more rational and safer anesthetic approach. With the exception of cardioversion procedures, which are discussed in Chapter 12 , the focus of this chapter will be the most common interventions, issues, and challenges for the anesthesiologist in the electrophysiology laboratory.

Table 11-1

Common Electrophysiology Cases and Estimated Anesthesia Times

Category	Procedure	Usual Anesthetic Technique	Time
MAC in recovery unit	Cardioversion	A short period of deep sedation usually using a bolus dose of propofol (or etomidate if the ejection fraction is low)	15 min
—	TEE	Deeper sedation may be required for some patients undergoing TEE who are unable to tolerate the procedure with conscious sedation by the cardiology team	60 min
—	NIPS	Deep sedation may be required for cardioversion or defibrillation	30-45 min
MAC in electrophysiology laboratory	Pacemaker placement or battery change	Fentanyl/midazolam or infusions of propofol/remifentanil/midazolam	3-4 hr
—	ICD or biventricular ICD placements or battery changes	Fentanyl/midazolam or infusions of propofol/remifentanil/midazolam (defibrillator threshold testing will require a short period of deeper anesthesia similar to that in a cardioversion)	3-4 hr
—	Loop recorder placement in superficial anterior chest wall	Fentanyl/midazolam or infusions of propofol/remifentanil/midazolam	2-3 hr
—	Atrial flutter radiofrequency ablation ^∗	Infusions of propofol/remifentanil/midazolam	6-10 hr
—	Ventricular tachycardia or ventricular fibrillation or premature ventricular contraction radiofrequency ablation ^∗	Usually infusions of remifentanil only; discuss additional sedatives with cardiologist	6-10 hr
General anesthesia in electrophysiology laboratory	Atrial fibrillation radiofrequency ablation	General endotracheal anesthesia using jet ventilation and TIVA, which predominantly involves propofol and remifentanil infusions Radial arterial lines commonly placed	6-10 hr
—	Lead extraction (especially using laser)	General endotracheal anesthesia	3-4 hr
—	Ventricular tachycardia or ventricular fibrillation radiofrequency ablation using an epicardial approach	General endotracheal anesthesia	6-10 hr

ICD, Implantable cardioverter-defibrillator; MAC, monitored anesthesia care; TEE, transesophageal echocardiography; TIVA, total intravenous anesthesia.

∗ These cases may require conversion to general anesthesia on short notice.

Before an anesthesia group considers extending anesthesia coverage to the electrophysiology laboratory, a review should be made of the availability of anesthesia personnel within the practice and the economics of providing the requested coverage. Procedures in the electrophysiology laboratory often involve anesthesia hands-on attendance for 12 hours or more. Because most of the anesthesia revenue will be derived from the relatively poor time unit accumulation, the cost of providing anesthesia coverage may be significantly more expensive than the final reimbursement that is realized. Because the electrophysiology laboratory is usually a positive revenue generator for the hospital and anesthesia is critical for sustaining this revenue source, a serious discussion needs to occur with the hospital administrators concerning the hospital’s supplementing anesthesia services to cover any shortfall in revenue.

Role of the Anesthesiologist in the Electrophysiology Laboratory

In 2011 a statistical review of the incidence of cardiac arrhythmias in the United States revealed that over 14 million people suffered from some form of cardiac arrhythmia. Within this group of patients, more than 881,000 required hospitalization and 40,700 died as a result of the arrhythmia or associated comorbidities. With this increase in the patient population diagnosed with arrhythmias, as well as the improvements that have occurred in the technological approaches for treating arrhythmias, the number of interventional procedures in electrophysiology laboratories has greatly increased over the past several years. Included in this increase is a trend toward greater use of anesthesiology services in the electrophysiology laboratory. A consensus document published in 1998 indicated that conscious sedation was standard for arrhythmia-specific procedures, particularly catheter ablations in adults. A survey of the task force members of a consensus statement group concerning catheter ablation of atrial fibrillation published in 2007 found that approximately two thirds of centers used conscious sedation for these procedures and reserved general anesthesia support for patients at higher risk. A more recent publication reported that approximately 50% of centers routinely employed general anesthesia for all their atrial fibrillation ablation procedures.

Consistent with this trend, anesthesiology involvement in electrophysiology laboratories at the Hospital of the University of Pennsylvania increased significantly over the past several years ( Figure 11-1 ). A decade ago, an anesthesiologist would occasionally be called to the electrophysiology laboratory for a cardioversion, often as part of a longer ablation procedure done mostly with sedation by cardiology nurses.

Figure 11-1, Growth of annual case load at the Hospital of the University of Pennsylvania electrophysiology laboratories over the past several years with particular emphasis on the caseload requiring anesthesia services.

The role of anesthesiologists has rapidly changed in the last decade to one of active involvement in nearly every procedure except for straightforward venograms and tilt table testing. The primary reason mandating the presence of anesthesia personnel during nearly every electrophysiology procedure is that the use of anesthesiologists allows the electrophysiology procedures to be performed faster and more effectively. The need for qualified anesthesia services is of particular benefit when dealing with an anxious patient who is difficult to sedate by ordinary means or a patient with airway concerns such as sleep apnea or a history of difficult intubation. In addition, it is the rare patient undergoing an electrophysiological procedure without other major comorbidities who would not benefit from the input and management of an anesthesiologist. An anesthesiologist brings other skill sets to the electrophysiology table in addition to airway and sedation management. The high-risk procedure of transvenous lead extraction can be more effectively and safely directed by an anesthesiologist using the findings from real-time transesophageal echocardiography (TEE). TEE allows early warning of events such as clot embolization, ischemic myocardial changes, and tamponade.

Considerations in the Electrophysiology Laboratory

Preprocedure Testing

Before an electrophysiological procedure, an echocardiogram provides important information for the anesthesiologist concerning planned fluid management and left ventricular function, which is critical for determining the approach that will be used for induction and maintenance of anesthesia. In addition, the echocardiographic evaluation provides important information about the presence or absence of a thrombus. TEE is more sensitive than transthoracic echocardiography for determining the presence of thrombus. A thrombus can develop in the left atrial appendage in patients with atrial fibrillation and can lead to an embolic stroke on cardioversion. Therefore ruling out the presence of a left atrial thrombus before cardioversion is necessary. Echocardiography also can help define abnormal anatomy in patients with congenital heart disease who have right-to-left shunting of blood. These patients are at risk for systemic air embolization should air inadvertently be introduced into the venous circulation. Under these circumstances, extreme care must be given to ensure that all intravenous fluids provided are free of air ( Box 11-1 ). The presence of specific congenital anatomical abnormalities also may be a root cause for long-term dysrhythmias in spite of surgical or electrophysiology intervention.

Box 11-1

Air Bubble Precautions With Right-to-Left Shunting of Blood

Intravenous

Ensure that all injection ports and tubing are free of air. If the intravenous is prepared and left in a cold environment for any time, recheck before use, because air bubbles can form in the tubing from dissolved air coming out of solution.

Syringe

Air bubbles adhere to the plunger and should be removed before giving a bolus of a drug. It is suggested that avoiding use of the last half a milliliter of drug in a syringe will prevent the injection of micro air bubbles that adhere to the plunger.

Syringe in Stopcock

When connecting a syringe to a stopcock to give a drug, make sure the air in the stopcock connector and air in the tip of the syringe have been flushed out before connecting the two for giving medication. Draw back half a milliliter of intravenous fluid into syringe to ensure no air is present before injecting.

Syringe in Injection Port

Recheck injection port to ensure it is free of air, and squirt some of the drug out of syringe needle to ensure no air in needle before putting the needle into the injection port. Draw back half a milliliter of intravenous fluid into syringe to ensure no air is present before injecting.

Central Venous Catheter

A central venous catheter is rarely placed by an anesthesiologist in the electrophysiology laboratory. If one is used during the placement procedure, extreme caution should be taken in the nonparalyzed patient to never let the catheter be open to room air, which would allow entrainment of air into the venous circuit should the patient develop a negative intrathoracic pressure with inspiration.

Blood laboratory testing is recommended before most electrophysiology procedures. Complications of invasive, as well as “just” percutaneous, procedures can include significant hemorrhage, so a baseline hemoglobin or hematocrit value and blood type and screen results should be obtained before all major procedures. In cases with a high risk for hemorrhage, such as lead extractions, ensuring that blood is crossmatched before the start of the procedure and immediately available is recommended. Coagulation studies should be performed preoperatively, because many patients undergoing an electrophysiology procedure are medicated with anticoagulants in an attempt to reduce the risk for a thromboembolic event such as a stroke. Serum creatinine and blood urea nitrogen are good indirect methods for assessing renal function. The status of the kidneys becomes especially important in the electrophysiology laboratory for the longer ablation procedures because significant amounts of fluids are given by the electrophysiologist and intravenous contrast dye is often administered. Finally, serum electrolytes and thyroid function tests may help diagnose the underlying cause of some of the cardiac rhythm abnormalities.

A baseline electrocardiogram (ECG) should be obtained, with particular attention paid to the rhythm and any existing ischemic changes. During the ablation process, the coronary arteries and their branches, particularly on the right, can be harmed, and a baseline ECG for comparison is useful when trying to determine the cause for a sudden fall in blood pressure. Longer cardiac rhythm studies may have been performed on many of the patients undergoing electrophysiology procedures with such modalities as 24-hour Holter monitoring. A chest radiograph may be helpful in demonstrating cardiomegaly, heart failure, implanted devices, and preexisting pulmonary conditions.

Anesthetic Management

Procedures in electrophysiology laboratories are performed with either monitored anesthesia care (MAC) or general anesthesia. Some procedures, such as atrial flutter radiofrequency ablation, may start out as a MAC case and then convert to a general anesthetic (see Table 11-1 ). One commonly accepted approach to general anesthesia is the use of continuous infusions of propofol and remifentanil. The combination of propofol 50 to 100 mcg/kg/min and remifentanil 0.08 to 0.14 mcg/kg/min usually causes a fall in blood pressure, so once the infusions of anesthetics begin, an infusion of phenylephrine at a baseline rate of 25 to 75 mcg/min is also added. The infusion of phenylephrine is adjusted based on the patient’s individual response to the anesthetics, but it is rare that phenylephrine is not needed at all. In patients with poor left ventricular function, 1 to 2 mcg/min of epinephrine may be a better approach than phenylephrine. Succinylcholine is used by some anesthesiologists to facilitate endotracheal intubation, but other paralytics are not often used. The reason for avoiding long-acting muscle relaxation is to allow the electrophysiologist to determine the path of the phrenic nerve during the mapping procedure on the posterior endocardial wall and thereby avoid harming it during the ablation process. The reason for avoiding an inhalational agent is outlined in the section concerning the effect of anesthetics on electrophysiological function.

The anesthesia plan in electrophysiology will depend on the nature of the procedure and patient-specific considerations. Most procedures performed in electrophysiology laboratories are not as painful as invasive surgical procedures. However, some parts of the procedures are associated with pain, particularly if tunneling is necessary, if the patient experiences the burning sensation associated with ablation, or if cardioversion or defibrillation is necessary. Potential hemodynamic instability or the length of a procedure may be indications for general anesthesia with a secured airway. Although the procedures themselves may not be especially painful, patients with preexisting skeletal or joint injuries, especially spine issues, may have significant postprocedure pain as a result of remaining in one position for an extended period.

Airway Management

Airway management in the electrophysiology laboratory may be extremely difficult because of the large, bulky equipment in the room. During intubation, it is not uncommon for the anesthesiologist to contort his or her body, straddle one arm of an x-ray machine, and duck under another arm in an effort to gain a reasonable position from which to intubate ( Figures 11-2 and 11-3 ).

Figure 11-2, An illustration of the cramped space at the head of the table in the typical electrophysiology laboratory. The equipment required for the procedure envelops the patient, often leaving the anesthesia provider limited access during intubation. Note the distance of the anesthesia machine from the patient’s head. In addition, the anesthesia provider must be prepared to move the infusion pumps out of the way as the cardiology x-ray equipment moves.

Figure 11-3, Another view of the space allowed the anesthesia provider. Note that it will be necessary to straddle the lower arm of the x-ray equipment while ducking under the upper arm during intubation. Once again, the distance of the anesthesia machine from the patient’s head can be appreciated.

For intubation, a video laryngoscope may be less traumatic than conventional laryngoscopy and reduces the number of repeat laryngoscopies. Many patients undergoing electrophysiology procedures have received anticoagulation, so minor trauma during airway management can result in a major hematoma. Likewise, placement of a soft bite block between the teeth is recommended to decrease the chance of the patient biting the tongue or cheek during cardioversion and defibrillation.

Positioning and Padding

Procedures in electrophysiology laboratories are generally performed with the patient in the supine position with arms tucked and padded. This position grants the interventionist better access to the patient and facilitates biplane fluoroscopy, but having the arms tucked makes detecting intravenous and arterial catheter problems (e.g., infiltration or disconnection) more difficult. Proper positioning and padding are important to avoid patient injury, particularly during longer procedures. Procedures in the electrophysiology laboratories may last 8 hours or longer. Maintaining a well-padded patient who is comfortable throughout the procedure is the key to a pain-free postprocedure recovery ( Figure 11-4 ). After padding is complete, the arms of the patient must be restrained to prevent movement and injury during cardioversion and defibrillation. Because patients are not usually paralyzed after induction of anesthesia, cardioversion during the procedure may produce injury from flail movement of the limbs. Restraining the arms is important for patients receiving MAC and general anesthesia. If an arterial catheter is placed for the procedure, the arm to be used may be left unrestrained until the catheter is placed, usually after intubation and securing of the airway.

Figure 11-4, An illustration of the typical techniques used for padding the patient. These measures include a headrest (A), a horseshoe-shaped roll placed under the shoulders and then covered by soft padding (B), arm padding (C), and a large roll or pillow (D) placed under the knees to help alleviate pressure on the spine.

Monitoring

American Society of Anesthesiologists (ASA) standard monitoring should be used for patients anesthetized in electrophysiology laboratories. For electrophysiology procedures in which rapid changes in blood pressure might occur as a result of changes in cardiac rhythm or bleeding complications, blood pressure should be monitored by either a radial artery catheter or a femoral artery catheter. In most patients, these catheters may be placed after induction of anesthesia. An arterial cannula is useful for sampling blood for arterial blood gas, glucose, and electrolyte levels; titration of anticoagulation therapy; and helping with the differential diagnosis of a hypotensive episode. A urinary bladder catheter should be placed for longer procedures to monitor urine output, to guide fluid management, and to keep the bladder from becoming distended while the patient must remain motionless in the supine position for an extended period.

Fluid Management

Intravenous fluids must be actively managed by the anesthesiologist for all patients undergoing electrophysiology procedures. These patients often have a delicate cardiac status, and judicious management of fluids is mandatory. Liters of fluid may often be infused by the electrophysiologist during the ablation process. It is not unusual that by the end of the procedure the patient may have a positive fluid balance of over 3 L. Many patients undergoing electrophysiology procedures have cardiomyopathies and are prone to congestive heart failure; thus the anesthesiologist’s attention must be directed at both limiting the amount of fluids provided during the anesthesia and performing a continuous careful evaluation for signs of volume overload. This ongoing evaluation of fluids translates into not only monitoring the patient’s fluid intake and output but also periodically communicating the fluid status to the interventionist. Diuretics are often used when a large positive fluid balance exists, especially if signs of congestive failure appear.

Temperature Control

Electrophysiology laboratories are often cold, and patients are within this cold environment for hours under anesthesia. To prevent hypothermia, active warming devices should be used. However, based on the type of procedure, limitations exist concerning modalities such as full-body forced air heaters. Often, partial body warmers and fluid warmers are the extent to which the anesthesiologist can prevent hypothermia. In addition, core temperature measurements using an esophageal probe serve the dual purpose of providing guidance in regard to effectiveness of warming devices and providing warning when the ablating is being performed near the esophagus.

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