New Developments and Current Concerns in Cardiac Anesthesia

Educational Objectives

The goals of this program are to improve anesthesia management during thoracic aortic surgical procedures by re­viewing the evidence supporting new guidelines, and to improve the management of ST segment elevation during noncardiac surgery. After hearing and assimilating this program, the clinician will be better able to:

1.   Choose the most appropriate method of monitoring brain activity during hypothermic arrest.

2.   Prevent poor neurocognitive outcomes by choosing optimal cerebral protection strategies during hypo-thermic         arrest.

3.   Discuss the strength of evidence for or against various neuroprotective strategies used during thoracic aortic surgery.

4.   Manage intraoperative or perioperative ST segment elevation.

5.   Identify strategies for preventing ST segment elevation and associated myocardial infarction.

Faculty Disclosure

In adherence to ACCME Standards for Commercial Support, Audio-Digest requires all faculty and members of the plan­ning committee to disclose relevant financial relationships within the past 12 months that might create any personal con­flicts of interest. Any identified conflicts were resolved to ensure that this educational activity promotes quality in health care and not a proprietary business or commercial interest. For this program, the faculty and the planning committee re­ported nothing to disclose. In his lecture, Dr. Ramsay discussed the off-label or investigational use of a therapy, product, or device.

Acknowledgments

Dr. Reich spoke at 63rd Annual Postgraduate Assembly in Anesthesiology, held December 11-15, 2009, in New York, NY, and sponsored by the New York State Society of Anesthesiologists. Dr. Ramsay spoke at Texas Society of Anesthesiologists 2009 Annual Meeting, held September 10-13, 2009, in San Antonio, TX. The Audio-Digest Foundation thanks the speakers and the sponsors for their cooperation in the production of this program.

Thoracic Aortic Disease Guidelines: How They May Change your Practice

David L. Reich, MD, Professor and Chair, Department of Anesthesiology, Mount Sinai School of Medicine, New York, NY

Hypothermic circulatory arrest: important to measure temperature in multiple locations

Preparation: primarily involves achieving adequate cerebral cooling; bladder and rectal temperature more accurate reflectors of total body cooling than temperature in pulmonary artery or esophagus; allow >30 min on extracor­poreal circulation to cool brain adequately to withstand hypothermic arrest; electroencephalography (EEG), bispectral index (BIS), near-infrared spectroscopy, and jugular bulb oxygen saturation may help confirm cerebral cooling (hypothermia affects cerebral metabolism); jugular bulb catheter difficult to insert in »25% of patients, but sometimes used to validate spectroscopy readings; in speaker’s experience, relatively low jugular bulb satura­tion (<95%) has little impact on most neurocognitive outcomes, but some patients experience memory dysfunc­tion; overall, little difference seen in neurocognitive outcomes at speaker’s institution when <95% saturation achieved or if catheterization of jugular bulb not possible; use of jugular bulb catheter waning due to difficulty of insertion; animal studies suggest near-infrared spectroscopy good tool for monitoring saturation changes over time; bimodal pattern of cerebral desaturation  —  saturation decreases rapidly for first 2 to 3 min of hypothermia, followed by more consistent linear decline; thought to reflect rapid redistribution of blood volume, with blood al­ready in brain affecting measurement at first, followed by continued desaturation as blood redistributes; lowest read­ing may predict later neurocognitive problems

Transcranial Doppler ultrasonography: difficult to obtain signals in elderly women; “extraordinarily easy” to obtain signals in children; in speaker’s experience, if signal not obtained within first 5 min, unlikely to be successful with further effort; very effective for monitoring cerebral blood flow and occurrence of emboli (greatly increased risk for microemboli associated with vacuum-assisted drainage, low reservoir volumes, and [possibly] excessive coronary suction)

Cerebral protection: number of microemboli correlated with subsequent cognitive dysfunction; strategies  — monitoring of brain (eg, BIS, other forms of EEG, near-infrared spectroscopy); minimizing microemboli (if tran­scranial Doppler signal absent, facing probe toward descending thoracic aorta provides good alternative for counting microemboli); temperature management; cross-clamping

Perfusion management: old technique  —  induce hypothermic arrest for 20 to 40 min for aortic arch reconstruction; reperfusion associated with neurologic problems such as short-term memory loss; outcomes in patients undergo­ing 1 to 24 min hypothermic arrest similar to those of patients undergoing coronary or valvular surgery without hypothermic arrest; >25 min hypothermic arrest associated with higher probability of persistent neurocognitive dysfunction, especially  memory and fine motor skills (early dysfunction significant predictor of late and persis­tent dysfunction); retrograde cerebral perfusion  —  in one study, significant predictor of negative neuropsycho­logic outcomes (major stroke or significant decline in neuropsychologic testing scores); findings persisted even after controlling for duration of cerebral ischemia; on further analysis, age only significant predictor of poor out­comes; nevertheless, many centers abandoned use of retrograde perfusion as main technique (although still used at some centers with good results); in cadaver studies, associated with wide variation in flow achieved through internal jugular vein; in speaker’s opinion, does not provide sufficient metabolic support to brain; may flush out cerebral emboli (possibly at expense of significant cerebral edema); probably works through maintenance of ce­rebral hypothermia; outcomes may also be associated with target temperature (no standard exists); successful ret­rograde reperfusion may be associated primarily with good maintenance of hypothermia

Selective cerebral perfusion: at speaker’s center, perfusion done through axillary rather than femoral artery to avoid flushing atherosclerotic plaque in descending aorta toward brain; trifurcated graft of cerebral vessels (anastomo­sis of innominate, left common carotid, and subclavian arteries) permits application of cross-clamp and resump­tion of cerebral perfusion through axillary artery cannula; when perfusion achieved, anastomosis completed by grafting trifurcated graft to main graft in ascending aorta and completing surgical repair with adequate cerebral perfusion; in animal studies, degree of neurocognitive recovery associated with temperature of perfusate (early recovery better with cooler perfusate); data from Columbia University suggest that duration of hypothermic ar­rest significant predictor of poor neuropsychologic outcomes £5 yr after surgery; however, although length of time to achieve anastomosis influences outcomes, length of selective cerebral perfusion not associated with neu­ropsychologic decline; predictors included advanced age and lower educational level; duration of cardiopulmo­nary bypass also not associated with neuropsychologic problems

Warming after hypothermic arrest: data available only from coronary artery bypass graft procedures; overly aggres­sive cooling associated with negative outcomes; slow warming recommended; perfusate temperature should never exceed 37^o C

Neuroprotection guidelines for thoracic aortic surgery

Types of recommendations: class I  —  strong support from well-designed studies or expert opinion (should not be ignored); class IIA and class IIB   —  evidence progressively weaker; class III  —  indicates procedure or treatment not advisable

Repair of ascending aorta and transverse aortic arch: Class I  —  brain protection strategy to prevent stroke and pre­serve cognitive function should be key element of surgical, anesthetic, and perfusion techniques (implies anes­thesiologist must work with surgical team to develop neuroprotection strategy); Class IIA  —  deep hypothermic circulatory arrest, selective antegrade brain perfusion, and retrograde brain perfusion “reasonable” choices; can be used alone or in combination to minimize brain injury; consider institutional experience when selecting; Class IIIB  —  avoid perioperative brain hyperthermia (probably injurious)

Choice of anesthetic technique and agent (Class IC): tailor to individual patient; preserves independence of anes­thesiologist

Repair of descending thoracic aorta: Class IB  —  choice among invasive hemodynamic monitoring, transesophageal echocardiography (TEE), and motor- or somatosensory-evoked potentials should be tailored to individual patient needs and to surgical and perfusion techniques employed in open or endovascular procedure; capabilities vary among institutions; Class IIIC  —  regional anesthetic techniques not recommended for patients at risk for neurax­ial hematoma, due to use of potent anticoagulants; vascular surgeon cannot insist on regional anesthesia (deemed dangerous); Class III  —  routinely changing from double-lumen to single-lumen tube at end of procedure not rec­ommended if procedure complicated by significant upper airway edema or hemorrhage

Transfusions and antifibrinolytic and anticoagulation management: algorithmic approach “reasonable” for open and endovascular thoracic aortic repairs during perioperative period; institutional variations in coagulation test­ing capability and availability of transfusion products and/or pro- and antithrombotic agents important consider­ations; although designated level C evidence (indicates expert opinion; references Society of Thoracic Surgeons and Society of Cardiovascular Anesthesiologists joint statement on blood conservation guidelines), good litera­ture supports use of transfusion guidelines to protect patients

Conclusions: monitor patients closely; TEE helpful in all cases; EEG or derivatives and near-infrared spectroscopy also recommended; jugular bulb catheter becoming obsolete; choice of anesthetic agents not critical (avoid volatile agents if planning to use motor-evoked potentials); anticipate coagulopathy; institute transfusion algorithm; “be pa­tient during cooling and rewarming”; participate in designing organ preservation strategies; all guidelines above to be published by American College of Cardiology and American Heart Association

Acute ST Changes During Routine Surgery:
Etiology and Therapy

Michael A. E. Ramsay, MD, Chairman, Department of Anesthesiology and Pain Management, Baylor Univer­sity Medical Center, and President, Baylor Research Institute, Dallas, TX

Coronary arteries: key to patients’ well-being; normal coronaries should be wide open; endothelial dysfunction common, and often results in atherosclerosis and spasms; adequate perfusion pressure necessary to keep occluded surface artery open; lesions more dangerous (if blood flow becomes turbulent, piece of plaque may break off, oc­clude surface artery, and lead to full-thickness ischemia [sometimes fatal]); better tests needed to determine condi­tion of endothelium; “you’re as old as your endothelium” (responsible for constriction and dilation of arteries); endothelial dysfunction impairs vasoactivity; calcification leads to lack of system compliance, swings in blood pressure, plaque rupture and hemorrhage, embolization, and possible vessel obstruction

Case example: 45-yr-old woman with history of ovarian cancer; developed malignant left pleural effusion; admitted for left thoracoscopic pleurodesis; had history of heavy smoking; family history of coronary artery disease, but none noted during patient work-up; hemodynamic course stable during procedure, until occurrence of sudden in­ferior ST segment elevations near completion of surgery; blood pressure dropped rapidly; bradycardia developed; ST elevation quickly progressed

Management: speaker called for assistance; administered 1 mg nitroglycerin; blood pressure rose, heart rate in­creased, and ST elevations went down; in light of localized nature of elevation, patient presumed to have had acute coronary vasospasm; no other cardiac problems postoperatively

If patient has ST segment myocardial infarction: follow algorithm for supporting circulation; obtain cardiology consultation; if surface coronaries affected, may lead to full-thickness ischemia of cardiac muscle (likely le­thal); treat spasm with nitroglycerin or calcium channel blocker; presence of dislodged plaque calls for percu­taneous transluminal coronary angioplasty with stent, or administration of thrombolytic agent (if surgeon permits)

Differential diagnosis: acute pericarditis unlikely (associated with generalized rather than localized ST segment elevation); early repolarization ruled out because of “tombstone ST pattern” seen in this case; full-thickness myocardial infarction from disrupted plaque only other possible diagnosis

ST segment: observe shape (downward coving more reassuring than upward “tombstone” appearance); distribu­tion helps distinguish spasm from pericarditis; real-time detection via pulmonary artery catheter can provide early signals of dysfunction; TEE shows potential for wide application when less costly simpler versions be­come available

Preventive therapy: b-blockers, a₂-agonists, and statins; tight control of heart rate (associated with less turbulent blood flow and greater coronary protection); recent studies using b-blockers have produced mixed results (some show evidence of benefit, others do not); in Perioperative Ischemic Evaluation (POISE) trial, high-dose b-block­ers associated with increased risk for stroke; use only in carefully selected patients; statins  —  good evidence sug­gests protective effect on endothelium (by increasing plaque stability and decreasing platelet activity and levels of inflammatory markers); associated with decreased mortality; perioperative use should be considered

Therapeutic hypothermia: role in neuroprotection demonstrated; evidence for cardiac protection more controver­sial; some centers experimenting with regional cardiac hypothermia, with promising results in reducing extent of infarction

Questions and answers: choice of leads for monitoring high-risk patients in recovery room and intensive care unit  —  V2 and V5 used most commonly; ST elevations associated with noncardiac surgery seen more often in re­covery than during surgery (usually due to occlusion from plaque); combining nitroglycerin with phenylephrine (in case example)  —  if ischemia causing ventricle to fail, vasoconstrictor may increase afterload and hasten ventricular failure; may also speed onset of bradycardia; ultra-short-acting calcium channel blocker  —  metabolized by ester­ases; half-life of 1 min; may have role as substitute for nitroglycerin in such cases

Suggested Reading

Dunkelgrun M et al: Beneficial effects of statins on perioperative cardiovascular outcome. Curr Opin Anaesthesiol 19:418, 2006; Dunkelgrun M et al: Bisoprolol and fluvastatin for the reduction of perioperative cardiac mortality and myocardial infarction in intermediate=-risk patients undergoing noncardiovascular surgery: a randomized controlled trial (DE­CREASE-IV). Ann Surg 249, 2009; Fischer GW et al: Mathematical model for describing cerebral oxygen desaturation in patients undergoing deep hypothermic circulatory arrest. Br J Anaesth 104:59, 2010; Khaladj N et al: Hypothermic circu­latory arrest with selective antegrade cerebral perfusion in ascending aortic arch surgery: a risk factor analysis for adverse outcome in 501 patients. J Thorac Cardiovasc Surg 135:908, 2008; Mangano DT et al: Effect of atenolol on mortality and cardiovascular morbidity after noncardiac surgery. Multicenter Study of Perioperative Ischemia Research Group. N Engl J Med 335:1713, 1996; POISE Study Group et al: Effects of extended-release metoprolol succinate in patients undergoing non-cardiac surgery (POISE trial): a randomised controlled trial. Lancet 371:1839, 2008; POISE Trial Investigators et al: Rationale, design, and organization of the PeriOperative Ischemic Evaluation (POISE) trial: a randomized controlled trial of metoprolol versus placebo in patients undergoing noncardiac surgery. Am Heart J 152:223, 2006; Reich DL, Uysal S: Con: Retrograde cerebral perfusion is not an optimal method of neuroprotection in thoracic aortic surgery. J Cardiothorac Vasc Anesth 17:768, 2003; Sear JW et al: Perioperative beta-blockade, 2008: what does POISE tell us, and was our earlier cau­tion justified? Br J Anaesth 101:135, 2008; Society of Thoracic Surgeons Blood Conservation Guideline Task Force et al: Perioperative blood transfuion and blood conservation in cardiac surgery: the Society of Thoracic Surgeons and the So­ciety of Cardiovascular Anesthesiologists clinical practice guidelines. Ann Thorac Surg 83:S27, 2007; Spielvogel D et al: Aortic arch replacement with a trifurcated graft. Ann Thorac Surg 83:S791, 2007; Wiesbauer F et al: Perioperative beat-blockers for preventing surgery-related mortality and morbidity: a systematic review and meta-analysis. Anesth Analg 104:27, 2007.