ASA October 2003 Newsletter

The modern-day cardiac catheterization laboratory (CCL) has truly become a multimodality interventional suite in which patients undergo a variety of diagnostic and therapeutic procedures. The history of human cardiac catheterization can be traced back to 1929 when Werner Forssmann, M.D., a surgical resident, inserted a percutaneous catheter into his right atrium via his antecubital vein in a small hospital in Eberswald, Germany. In 1964 vascular radiologist Charles T. Dotter, M.D., introduced the concept of transluminal angioplasty, while the first CCL percutaneous transluminal coronary angioplasty (PTCA) in an awake patient was performed by Andreas Gruentzig, M.D., a cardiologist in Zurich, Switzerland, in 1977.^8-10 Pediatric cardiac catheterization was first described in the 1930s by Castellanos⁴ and was first used purely as a diagnostic tool. Balloon atrial septostomy, first reported by Rashkind in 1968 in order to palliate neonates with transposition of the great arteries, was the first widely performed interventional procedure.¹⁴

The scope and practice of pediatric cardiac catheterization has continued to expand and now includes a multitude of interventional procedures. Because noninvasive imaging with echocardiography and/or magnetic resonance scanning is frequently used for anatomic diagnosis, cardiac catheterization is reserved for smaller, more critically ill patients with complex congenital heart disease who may require interventional procedures and diagnostic imaging prior to surgical intervention.

At the Texas Heart Institute, approximately 10,000 patients are seen annually in the CCL, and many of these cases require the consultation of an anesthesiologist. Procedures performed in the CCL may include diagnostic angiography, PTCA and stenting, electrophysiology studies and ablations, exclusion of both thoracic aortic aneurysms (TAA) and abdominal aortic aneurysms (AAA), valvuloplasty, transcatheter closure of atrial septal defects, pacing and defibrillator devices and even the placement of life-sustaining devices such as the new TandemHeart™ percutaneous ventricular assist device (pVAD). At Texas Children’s Hospital, 970 cardiac catheterizations were performed between September 2002 and August 2003 with anesthesiologists participating in the care of 74 percent of these patients. As diagnostic and interventional catheterizations are performed on smaller and sicker patients with increasingly complex forms of congenital heart disease, skillful anesthetic management is critical in maintaining stable hemodynamics and rapidly managing any complications that may occur during the procedure.

Performing an anesthetic in the interventional suite may present quite a challenge for the anesthesiologist, considering the complexity of the procedures and the multiple comorbidities of the patients. Preparation and familiarity with the arrangement of the CCL are key to the delivery of an uneventful anesthetic. The interventional laboratories are commonly located in remote locations separate from the general operating rooms and usually consist of a large procedural area and shielded control room. As the CCL is often distant from the blood bank, packed red blood cells (PRBCs) are generally held in the CCL during pediatric interventional procedures. In infants a unit of PRBCs may be split in the blood bank and a partial unit brought to the CCL in order to limit the patient’s exposure to multiple units of blood. The use of fluoroscopy and X-radiation are prominent in the CCL; therefore, it is imperative that all anesthesia personnel strictly adhere to the following three radiation safety principles: maximize distance from the radiation source, minimize exposure times and always use proper shielding with leaded glass, acrylic, gowns, gloves, thyroid collars and stands. Dosimeters must be worn at all times to help track cumulative exposure, and practitioners should keep all radiation doses “as low as reasonably achievable” (the ALARA principle), a concept fully supported by the radiation safety program at the Centers for Disease Control and Prevention.

The use of radiocontrast media is quite common in the CCL due to the extensive use of fluoroscopy, and the anesthesiologist should be aware of the effects of these agents. Many of the newer low-osmolar, nonionic agents such as Omnipaque™ (iohexol) have improved adverse reaction profiles, but caution must be exercised in patients with pre-existing renal insufficiency and diabetes mellitus;¹⁶ furthermore, these agents continue to be associated with atrial and ventricular arrhythmias, prolonged Q-T intervals, vasovagal reactions and thromboembolic events that may lead to the development of a myocardial infarction or cerebrovascular accident. Thromboembolic complications seem to be related to the length of the procedure, the type of catheter and syringe material used and the patient’s underlying disease processes. In infants, hypotension may be seen after contrast injection. Nephrotoxicity and the development of acute renal failure also are related to these agents, but the etiology of the renal failure remains unknown. The presumed mechanism is related to direct chemical toxicity and the effects of hypertonicity on red blood cells leading to altered deformability and thus compromised flow characteristics resulting in hypoperfusion of end organs. Adjuncts such as furosemide, mannitol, dopamine, fenoldapam and acetylcysteine have been used in an attempt to prevent renal impairment; however, adequate hydration and stable hemodynamics remain as the most reliable defenses against contrast-induced nephrotoxicity.^{1,2,3,5,12,17}

Anesthetic requirements in the CCL may range from monitored anesthesia care (MAC) to full general anesthesia with invasive monitoring and other modalities such as transesophageal echocardiography. As interventional procedures may be lengthy, and the potential exists for hemodynamic instability and significant blood loss, general anesthesia with endotracheal intubation is commonly performed in infants and children undergoing procedures such as balloon valvuloplasty, coiling of aortopulmonary collaterals, dilation or stenting of pulmonary arteries, balloon dilatation of coarctation of the aorta and device closure of a ventricular septal defect. With the advent of intracardiac echocardiography, however, device closure of an atrial septal defect may now be accomplished with deep sedation and spontaneous ventilation, even in children. Even regional techniques such as spinals and epidurals may be performed depending on the procedure at hand. Due to the prevalent use of antihemostatic and antithrombotic drugs, however, such as clopidogrel, low molecular weight heparin and warfarin, the risk of hemorrhage and the formation of an epidural hematoma should always be considered, even though the incidence of neurologic compromise has been estimated at <1/200,000 cases with spinal anesthesia and <1/150,000 cases with epidural anesthesia.^{6,7,11,13,15,18} Caution also should be exercised when dealing with medications such as abciximab and eptifibatide, which significantly affect platelet function and hemostasis.

Ready access to skilled anesthesia personnel, the pharmacy and the stat laboratory are also important when working in the CCL. For example there is always the potential for acute blood loss during the stenting of a tortuous AAA due to perforation or rupture of the aneurysm. The CCL is then rapidly converted into an operating suite, and the need for frequent blood sampling and rapid transfusion is immediate. The presence of a transfusion device such as the Belmont FMS 2000™ and experienced colleagues and assistants are invaluable in helping to manage such an unfortunate situation. The care of critically ill patients in the interventional laboratory does not cease upon completion of the posted procedure, and arranging for an intensive care bed may be necessary to help continue an acute level of care.

Regarding electrophysiology mapping studies and ablations, the use of inotropic drugs and vasopressors should be held to a minimum due to their proarrhythmogenic effects. This will help the electrophysiologist to determine an accurate mapping baseline for the patient, leading to more effective ablation of ectopic foci and tracts. Patients with pacing devices and automatic implantable cardioverter-defibrillator devices (AICDs) also should receive special attention in the CCL. When using electrocautery, exit pads should be placed in positions that direct electrical current away from pacing and AICD leads; otherwise suppression of pacing and inappropriate triggering of AICDs may occur. Due to the negative effects of electromagnetic interference, a transdermal magnet should be available at all times to convert pacemakers into asynchronous mode and also to suppress antitachycardic therapies on AICDs. When specifically working on a pacing device, the anesthesiologist must be aware of the presence of unipolar leads; if the generator loses physical contact with the patient on a unipolar lead setup, the device will be unable to pace due to an open circuit, and immediate means for backup pacing must be readily available to avoid hemodynamic compromise.

Electrophysiologic studies and radiofrequency ablations of arrhythmogenic foci are frequently performed on children with supraventricular tachycardia and Wolff-Parkinson-White syndrome. Increasingly, however, patients undergoing pediatric electrophysiologic studies and ablations may have significant underlying congenital heart disease and arrhythmias resulting from surgical treatment of these lesions. Implantation of an AICD may be necessary for children with ventricular arrhythmias after Tetralogy of Fallot repair while supraventricular arrhythmias are often seen in patients who have undergone a Mustard or Senning repair of transposition of the great arteries or a Fontan procedure. It is essential that inotropes, resuscitative medications and, if necessary, alternative methods of pacing be available for these patients during their catheterization.

The cardiac catheterization laboratory is an evolving entity, and as cardiologists, surgeons and interventional radiologists continue to develop protocols for procedures performed in the CCL, the anesthesiologist must be able to formulate and fully adapt a care plan to this remote environment. Patient needs are ever-changing due to the increased complexity of procedures, and it is readily apparent that the well-prepared and experienced anesthesiologist is an integral part of the CCL team responsible for maintaining a high level of care with minimal complications and improved outcome.

References:

1. Brezis M, Epstein FH. A closer look at radiovontrast-induced nephropathy. N Engl J Med. 1989; 320:179-181.

2. Briguori C, Manganelli F, Scarpato P, et al. Acetylcysteine and contrast agent-associated nephrotoxicity. J Am Coll Cardiol. 2002; 40(2):298-303.

3. Briguori C, Tavano D, Colombo A. Contrast agent-associated nephrotoxicity. Prog Cardiovasc Dis. 2003; 45(6):493-503.

4. Castellanos AR, Pereiras R, Varcia A. Angiocardiography in the child. Proceedings of the 7th Congress of the Pan-American Medical Association, Havana. 1939; 75-82,109-113.

5. Gerlach AT, Pickworth KK. Contrast medium-induced nephrotoxicity: Pathophysiology and prevention. Pharmacotherapy. 2000; 20(5):540-548.

6. Horlocker TT, Wedel DJ, Benzon H, et al. Regional anesthesia in the anticoagulated patient: Defining the risks (the second ASRA consensus conference on neuraxial anesthesia and anticoagulation). Reg Anesth Pain Med. 2003; 28(3):172-97.

7. Horlocker TT. Complications of spinal and epidural anesthesia. Anesthesiol Clin North America. 2000; 18(2):461-85.

8. King, SB. Angioplasty from bench to bedside to bench, Circulation. 1996; 93:1621-1629

9. Mueller R, Sanborn T. The history of interventional cardiology. Am Heart J. 1995; 129:146-172

10. Myler R, Stertzer S. Coronary and Peripheral Angioplasty: Historic Perspective, Textbook of Interventional Cardiology, 2nd ed., Vol. 1. Topol E, ed. Philadelphia: WB Saunders Co;1993.

11. Onishchuk JL, Carlsson C. Epidural hematoma associated with epidural anesthesia: Complications of anticoagulant therapy. Anesthesiology. 1992; 77:1221-1223.

12. Parfrey PS, Griffiths SM, Barrett BJ, et al: Contrast-induced renal failure. N Engl J Med. 1989; 320:143-149.

13. Rao TLK, El-Etr AA. Anticoagulation following placement of epidural and subarachnoid catheters: An evaluation of neurologic sequelae. Anesthesiology. 1981; 55:618-620.

14. Rashkind WJ, Miller WW. Transposition of the great arteries. Results of palliation by balloon atrioseptostomy in thirty-one infants. Circulation. 1968; 38:453-462.

15. Rosenquist RW, Brown DL. Neuraxial bleeding: Fibrinolytics/thrombolytics. Reg Anes Pain Med. 1998; 23:152-156.

16. Rudnick MR, Goldfarb S, Wexler L, et. al. Nephrotoxicity of ionic and nonionic contrast media in 1,196 patients: A randomized trial. The Iohexol Cooperative Study. Kidney Int. 1995; 47(1):254-261.

17. Schwab M, Healthy MA, et al. Contrast nephrotoxicity: A randomized controlled trial of a nonionic and ionic radiographic contrast agent. N Engl J Med. 1989; 320:149-153.

18. Vandermeulen EP, Van Aken H, Vermylen J. Anticoagulants and spinal-epidural anesthesia. Anesth Analg. 1994; 79:1165-1177.

Randall R. Joe, M.D., is a cardiovascular anesthesiologist at the Texas Heart Institute, St. Luke’s Episcopal Hospital and Assistant Professor of Anesthesiology, University of Texas Health Science Center at Houston, Houston, Texas.

Laura K. Diaz, M.D., is Assistant Professor of Anesthesiology, Baylor College of Medicine and is a pediatric cardiovascular anesthesiologist at Texas Children’s Hospital, Houston, Texas.

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