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Cardiac Anesthesia_ Made Ridiculously Simple by Art Wallace, M.D., Ph.D

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summary of cardiac anesthesia useful for trainees or practising anesthesiologists
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  Cardiac Anesthesiology MadeRidiculously Simple by Art Wallace, M.D., Ph.D. Cardiac surgery is a dangerous and complex field of medicine with significant morbidity andmortality. Quality anesthetic care with specific attention to detail can greatly enhance patientsafety and outcome. Details that are ignored can lead to disaster. This document will attemptto describe the bare bones sequence for cardiac anesthesia for adult CABG and VALVE procedures with specific recommendations. It is not all inclusive or definitive but it is theminimal critical requirements.If you keep your head screwed on very tightly and pay 100% attention at all times, thingswill only go poorly some of the time.A good reference is: The Practice of Cardiac Anesthesia by Frederick Hensley andDonald Martin, Little Brown Handbook. Patient Examination: Anesthetic evaluation must include attention to cardiac history. The cath report, thallium,echo, and ECG. Critical information includes: Left main disease or equivalent, poor distaltargets, ejection fraction, LVEDP, presence of aneurysm, pulmonary hypertension, valvular lesions, congenital lesions. Each of these points requires a modification of anesthetictechnique and specific information is required. How is their angina manifest? You need to be able to understand their verbal reports. If a patient’s angina is experienced as shortness of  breath, or nausea, or heart burn, or whatever, you need to be able to link that symptom to possible myocardial ischemia.Past medical history including history of COPD, TIA, stroke, cerebral vascular disease,renal disease (CRI is an independent risk factor), hepatic insufficiency will change anestheticmanagement.AllergiesMedications : Look specifically for anti-anginal regimen - synergism between calciumchannel and beta blockers, is their COPD being treated? It is very important for patients tostay on their anti-anginal therapy throughout the hospital stay. If a patient is on a beta blocker, calcium channel blocker, nitrate, and/or ACE inhibitor they should remain on thatdrug throughout the perioperative period. The patient should get all anti-anginal medicationson the day of surgery and following surgery. The day of surgery is the wrong time to gothrough a withdrawal process on any anti-anginal drug.Physical exam: AirwayChest: Is the patient in failure? Pneumonia? COPDCardiac: Do they have a murmur? Are they in failure?Abd: Ascities, Obesity  LABS: Minimal CBC, Plt, Lytes, BUN, CR, Glu, PT,PTTCXR: Cardiomegaly? Tumors? Pleural effusions?ECG: LBBB: Critical information if a pulmonary artery catheter is planned. Occasionally patients with LBBB can develop third degree block with PA catheter placement.Have they had a recent MI? Do they have resting ischemia? Where are their ST-T changes?PFT and ABG: Are they going to become a respiratory cripple? Information:  Tell them about the A-line, the PA catheter, and post op ventilation. Consent:  Patients having cardiac surgery have serious and frequent complicationsincluding: MI 6%, CVA 5%, Neuropsychiatric Effects 90%, Death 1-3-10% (Depends onrisk), Transfusion (40-90%), Pneumonia 10%. You must discuss these risks. Note: Write a clear note with all the standard details and consent. They will get an Aline,PA catheter, TEE. With the computerized records it is easy to get all the patient’sinformation. Make sure you sign your note so that it is visible to other computer users. Premedication: These patients are scared. They understand there is real risk. They also will become ischemic with stress. At least 40% get ischemia preop with good premedication.Most will without. Give them oxygen by nasal cannula with some premed: Valium,Morphine, something. Diazepam 10 mg PO on call to OR is a good choice. Medications Preop:  All patients must get their anti-anginals. If the nurses put patient on 9P- 9A BID drugs then state in the chart that patient is to get Drug X, Y, and Z with a sip of water at 6 AM. Otherwise at 9AM they will be in the OR, needing their anti-anginals. Beincredibly clear in your preop orders or they won't get their premeds. Withdrawal of anti-anginal medications during cardiac surgery increases risk of death, MI, CVA, and renalfailure. DO NOT DO IT. PA Catheters:  At the present time all bypass cases get the standard monitors plus an a-line,and a pa-catheter. There is an article in JAMA that suggests PA catheters offer littleadditional information and have inherent risk in ICU patients. As yet, this has not changedour practice. It is clear however that placement of PA catheters must be incredibly skillfulwithout injury to other structures. With no proven benefit all risk must be reduced. Onemethod to achieve this is ultrasonic mapping prior to catheter placement. Remove the towelsfrom behind their head, place the patient in the position you would like, then tape the head in place. Place the patient in tredellenburg. Take a permanent marker and draw out theanatomy, sternocleidomastoid, clavicle, carotid, etc. The more lines the better as it is hard todraw once the ultrasonic goop is in place. Place the blue line in the center of the echo screen.Place the blue dot on the probe to the patient's right. Make sure the probe is absolutely perpendicular to the bed. If you point it at an angle to the bed you will have to take the angleinto account and few can do trigonometry in your head. I will be glad to test you on this point. Then take the 5 mHz probe and map out the path of the carotid and the IJ. The IJ is bigger and collapses under pressure, the carotid is round and doesn't collapse under reasonable pressure. If you don't have a line in an appropriate place, wipe off the goop,redraw, and then map again. This technique requires the patient to not move betweenmapping and placement. I think this system is faster than not using the echo, as you waste 2minutes mapping, and save 10 minutes of searching with a needle. Anesthesia:  Despite our best efforts we have not been able to demonstrate that one form of   anesthesia is obviously better than any other with one exception. Halothane, Enflurane,Isoflurane, high and low dose narcotics, and propofol based anesthetics are equivalent aslong as hemodynamics are controlled. Desflurane inductions have been demonstrated tocause pulmonary hypertension and myocardial ischemia. Desflurane is the only anestheticnot recommended for patients with known coronary disease. There is also high dose spinalnarcotic (MS 1 mg subarachnoid) but safety data for this technique is limited. During themonth you will do two kinds of cases - non research cases during which you should try eachof the different techniques to get a feel for them, and research cases with an anestheticcontrolled by protocol. With skill, all techniques work, with luck, we may someday knowwhich are truly superior. Dose Ranges Fentanyl (High)100-200 mcg/kg (Medium) 20-40 mcg/kg (Low)1-5 mcg/kgSufentanyl (High) 20-40 mcg/kg (Medium) 10-20 mcg/kg (Low) 1-2 mcg/kgRemifentanyl 0.2 to 1.0 mcg/kg/minMidazolam (High) 3-5 mg/kg (Medium) 2 mg/kg (Low) 0.5 mg/kgRemifentanyl: To quote one of the great masters of cardiac anesthesia, there are a lot of things that one can do while standing up in a canoe, but why bother? Remifentanyl has avery short half life (5 - 10 minutes) because of its metabolism by non specific cholinesterase.It allows very rapid emergence. It can be used for cardiac anesthesia but the cost is high andsome narcotic must be given prior to wake up in the ICU. Reduction in the dose may be possible by giving a longer acting cheap narcotic (fentanyl) to occupy a fraction of the mureceptors and then use the remifentanyl to occupy a smaller fraction. This method of mixinga short half life with a longer half life narcotic may also smooth emergence and preventaccidental emergence should the infusion terminate prematurely. You should try a case withremifentanyl but clearly recognize the dangers and cost of this new drug.Propofol: You should try a case with propofol used continuously from the start of the case,and one where it is added after bypass. It is expensive but allows a simple technique for early extubation. If early extubation and discharge from the unit is planned the expense of drugs that make it possible is easy to justify.Dexmedetomidine is an alpha 2 agonist with a 1500:1 alpha 2 to alpha 1 ratio. For example,clonidine has a 30:1 alpha 2 to alpha 1 ratio. It may be used as an adjunct to anestheticswith reductions in MAC or as a post operative sedative by infusion. Its role in cardiacanesthesia is just being figured out. Planning for Early Extubation:  With the health care revolution this is the new thing. Thekey is multiple little changes in anesthetic technique that make it possible and a goodcandidate who is problem free to make it work. The problem is simply that many patients appear to be good candidates and then aren’t when they get to the ICU,others look like problems and do well. The simplest solution is to treat all patients ascandidates for early extubation and then see who qualifies. Early extubation should be planned for in all patients because it requires planning right from the start of thecase. The most successful candidates have reasonable cardiac and pulmonaryfunction but it is certainly not a requirement. The changes we have made includelimiting fluid given to the patient. Limiting the total narcotic and benzodiazepinedose. Rely on volatile agents or propofol during the case. Provide sedation post opthat is easy to get rid of (propofol). Careful control of blood pressure with  emergence. Remember some vasodilators (nitroprusside) inhibit hypoxic pulmonaryvasocontriction, increase shunt, and make weaning of FIO2 more difficult. Rapidweaning of FIO2 post op is critical. Then extubate the patient. Extubation time iscontrolled by nursing shift changes and protocols. If you want to extubate early,wean the FIO2 rapidly, wake the patient up, and when the patient meets writtenextubation criteria do it. It requires a cultural shift to accomplish. The most commonreason for delayed extubation is simply V/Q mismatch (shunt) caused by heparin- protamine complexes in the lung. The second most common reason is excessivesedation. Finally, hemodynamics, coagulopathy, etc. get on the list. Set Up: Standard room set up including Suction, Machine checkout, Airway equipment,Drugs (Succinyl choline, thiopental, non-depolarizing muscle relaxant, atropine,glycopyrolate, ephedrine, neosynephrine (syringe and infusion ready), dopamine (infusionready), calcium chloride, heparin (30,000 units drawn up), lidocaine and epi in drawer. Patient Preparation:  At least one large IV ( < 16g), two are better, a-line on right (left sideis occluded by retractor for IMA), take into room and place on O2 for rest of setup, 5 leadfor machine, 3 lead for echo, cover V5 with tegaderm. Right IJ PA catheter. Preox whilegetting baseline values. Intraoperative Safety: Cardiac surgery has large quantities of blood at arterial and higher  pressures. There is frequent splash. You must wear eye protection at all times in theoperating room. Expensive goggles around the neck are not acceptable. Put them on at alltimes in the OR. You should consider the operating room as a woodshop with HIV on allthe wood chips. You would not operate power tools in a woodshop without eye protection,do not do it in the OR. Communication: This operation is a long series of repetitive procedures that absolutely, positively, have to be done correctly. If any are done incorrectly the patient will suffer.Communicate with the surgeon. Ask questions. Tell him what you are doing. If you arehaving trouble, tell him/her. The operation requires a team approach and you are a member of the team. Don't let your activities or problems be a mystery to the surgeons. Hypotension:  The surgeons can cause profound hypotension with cardiac manipulation. If the pressure suddenly drops or PVC's develop look at what they are doing. Before you givea drug to treat episodic hypotension look to see what they are doing. If you give a drug because of hypotension caused by the surgeons and then they let go of the heart, the pressure will sky rocket. State clearly Pressure is 70/30) they will get the message and stoplifting up the heart. They may ask you to hand ventilate during some dissection. Watch whatthey are doing to make sure you are helping not hindering. Hemodynamics: Prior to Valve Repairs there are specific recommendations: AS: Preload: Keep it up Afterload:  Maintain SVR:  Maintain HR:  50-80 Rhythm:  NSR  AI: Preload: Keep it up Afterload:  Down SVR:  Drop HR:  60-80 Rhythm:  NSR  MS: Preload:  Keep it up Afterload:  Maintain SVR:  Maintain HR:  50-80 Rhythm:  NSR  MR: Preload: Keep it up Afterload:  Down SVR:  Down HR:  50-80 Rhythm:  NSR  Prebypass Hemodynamics: You should try to keep the blood pressure within ± 20% of 
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