What is pre-anesthesia examination before open heart surgery? - P2

This is an automatically translated article.

The article was written by MSc Ho Thi Xuan Nga - Cardiac Anesthesiologist, Cardiovascular Center - Vinmec Central Park International General Hospital.

Before every surgery, no matter how big or small, the doctor needs to predict the level of success, failure, the risk of possible complications for his patients. Therefore, it is always required that at least one pre-anesthesia visit be performed at least 24 hours prior to commencing surgery.

1. Common drugs used before and during cardiac surgery: which drug should be stopped? Why?

1.1 ACE inhibitors and angiotensin II antagonists Converting enzyme (ACE) inhibitors and angiotensin II (AA-II) antagonists are the antihypertensive agents of choice because they reduce peripheral resistance and venous return without causing tachycardia; on the other hand, it has inhibitory activity on left ventricular remodeling in hypertension and heart failure.
Because general anesthesia inhibits sympathetic activity, the patient's cardiac output under IEC/AA-II only adapts to changes in preload with vasopressin (slow regulation); blood pressure becomes preload dependent.
Therefore, there is a risk of severe hypotension on induction of anesthesia and wide fluctuations in blood pressure during volume changes and central stimulation.... These effects are further contributed by hypokalemia and confusion. With diastolic dysfunction due to concomitant use of diuretics, ACE inhibitors should be discontinued 24 hours prior to surgical intervention.
Calcium channel blockers Calcium channel blockers should be continued until surgery, although their interruption is unlikely to cause acute ischemia and their maintenance may increase the need for catecholamines and prolong effects of muscle relaxants.
Vasodilators of peripheral vascular resistance decrease but do not cause stagnation, they cause hypotension is not serious. Nifedipine and isradipine cause reflex tachycardia, while diltiazem and verapamil have negative chronotropic effects that can lead to severe bradycardia when taken with beta-blockers or amiodarone.
β-blockers are the only drugs associated with a reduction in the rate of ischemic events in coronary surgery. It improves long-term prognosis after myocardial infarction and in chronic heart failure.
Therefore, it has many benefits and it is advisable to continue using them until surgery rather than stopping them before surgery, however they can cause acute ischemia within 48 hours by affecting their efficacy. backlash.
Other antihypertensive drugs α2 agonists (clonidine, dexmedetomidine) limit tachycardia and hypertension, and further induce sedation and analgesia; These effects are very beneficial in surgery, and reduce the incidence of cardiac complications after surgery.
However, they inhibit the release of norepinephrine at the sympathetic terminal, and thus cause a decrease in dopamine activity but conversely an increase in dobutamine activity.

Diuretics Associated with a lower risk of hypokalemia-induced hypotension and preload. They promote hypokalemia, hyponatremia, hypomagnesemia, and metabolic alkalosis. It is best not to use diuretics on the day of surgery, to maintain high circulating volumes; This high preload facilitates equilibrium during induction of anesthesia and mechanical ventilation.
Considering the high K+ content of cardiac paralytic solutions, hypokalemia is not a significant risk, but hypomagnesemia increases the risk of cardiac arrhythmias, especially atrial fibrillation.
Nitrogen derivatives Must be maintained at the usual dose until the day of surgery; they are administered on the morning of the day of surgery, because abrupt stopping can cause ischemia. The drop in preload they induce is related to a decrease in sympathetic tone during induction of anesthesia; it usually causes a significant reduction in blood pressure, which must be adequately rehydrated (crystals, colloids) or given low-dose ephedrine (2-5 mg IV: central venous effect predominates). Regardless of the hemodynamic instability caused, continuous nitrate infusion should be continued until CEC.
Statins 3-hydroxy-3methylglutaril coenzyme inhibitors is a very widely used reductase or statin for lipid-lowering, anti-inflammatory, antioxidant and stabilizing effects on atherosclerotic plaques.
In cardiovascular surgery, they have three interesting features: 1) they increase NO production, decrease platelet aggregation and improve endothelial function; 2) they reduce inflammatory and endothelial responses to CEC; and 3) they slow smooth muscle proliferation, reducing the risk of restenosis after PCI.
In cardiac surgery, statins reduce not only mortality but also the risk of stroke and atrial fibrillation. When treatment was resumed from the first postoperative day, they reduced the incidence of renal failure.
Their effect on infarct risk was variable, more pronounced when significant inflammation was involved. Therefore, statins have an important role in cardiac surgery. They must be maintained preoperatively, including preoperatively, and resumed within the first 24 hours following surgery.
Antiarrhythmic drugs Antiarrhythmic drugs have a protective role to maintain stable heart rhythm in the perioperative period. Class I antiarrhythmic drugs should be considered for drug interactions because they prolong the action of muscle relaxants. Amiodarone causes noncompetitive alpha and beta sympathomimetic which can cause severe hypotension and bradycardia.
Drug interactions with digitalis are numerous, but not with anesthetics; isoflurane, ketamine and fentanyl are highly tolerated by digitalis.
Diabetes medication The insulin required for the patient's glycemic control is continued until the day before surgery in the evening. The safest way is not to inject insulin at the time of anesthesia, but to control blood sugar (<10 mmol/L) with a continuous rapid-acting insulin infusion (Actrapid®) as soon as the patient arrives in the operating room.
Oral antidiabetic drugs (sulfonylureas) that act against myocardial protection by a pre-adaptation mechanism provided by halogens; not given on the day of surgery. In patients at high coronary risk, the drug should be discontinued a few days before surgery. The same is true for selective COX-2 inhibitors. Oral antidiabetic drugs can be replaced with insulin.

Anticoagulants Although there are clear recommendations regarding the time limits to be observed during heparin and anti-vitamin K therapy, for new generation anticoagulants only data are available. on the pharmacokinetics of these substances:
Unfractionated heparin 0-4 h Prophylactic LMWH 12 h LMWH 24 h therapy (48 h if creatinine clearance <50 ml/min) Fondaparinux (Arixtra®) 72 h ( 4 days if creatinine clearance <50 mL/min) Dabigatran (Pradaxa®) 48 h (4 days if creatinine clearance <50 mL/min) Apixaban (Eliquis®) 48 h (3 days if clearance creatinine <50 mL/min) Rivaroxaban (Xarelto®) 48 hours (3 days if creatinine clearance <50 mL/min) Coumarines 5 days (Marcoumar® 10 days); heparin replacement These recommended durations are based on an expectation corresponding to 5 times the drug half-life (serum levels fall to 3%) due to the high bleeding risk of cardiac surgery. In the case of renal failure, they are prolonged to give the substances enough time to be eliminated by the kidneys. The degree of anticoagulant obtained from different drugs was evaluated by several tests:
Vitamin K antagonists : TP and INR. Unfractionated heparin (HNF): aPTT (standard dose), ACT (high dose). Low molecular weight heparin (LMWH): anti Xa aPTT (non-quantitative modification). Fondaparinux (Arixtra®) : anti Xa Dabigatran (Pradaxa®) : anti IIa, Hemoclot TM (specific); TT, aPTT Rivaroxaban (Xarelto®), apixaban (Eliquis®) : adjusted anti Xa (specific); PT (non-quantitative, valid only if the reagent used is sensitive to rivaroxaban, such as Neoplastin Plus). Anti-platelet aggregation Secondary prevention Aspirin (75-325 mg/day) is effective in reducing the rates of recurrent infarction, stroke, peripheral arterial thrombosis, and mortality. It is a lifelong treatment that should never be discontinued, except in cases where there is a risk of excessive bleeding. In cardiac revascularization surgery, aspirin almost halves mortality, postoperative infarction, and secondary revascularization when initiated preoperatively and resumed as soon as 6 hours after intervention. , the current European recommendation (level IC recommendation).
Maintenance aspirin (75-160 mg/day) preoperatively (PAC and OPCAB); Discontinue aspirin 3-5 days before intervention in cases of high bleeding risk and in patients who refuse blood transfusion; Do not discontinue aspirin in people with mechanical valves or coronary stents, or in patients with acute coronary syndromes. Dual antiplatelet therapy (aspirin + clopidogrel or ticagrelor or prasugrel) is required after acute coronary syndrome or percutaneous revascularization with stenting. Duration of dual therapy varies depending on the situation 2 weeks after single-balloon angioplasty; 12 weeks after medicated balloon angioplasty; 4-6 weeks after passive stenting (BMS), but 12 months in case of acute coronary syndrome; 12 months after implantation of 1st generation active stents (DES); 6-12 months after implantation of second-generation DES 12 months after acute coronary syndrome with or without revascularization; 12 months in a very high-risk stent. Current data clearly demonstrate that the risk of infarction and death with antiplatelet therapy is 5 to 10 times higher than that of intraoperative bleeding when treatment is maintained. In cardiac surgery, the situation is made more delicate by the use of either a full-load heparin in CABG or a half-dose heparin during a pulsating coronary artery bypass graft. In the case of RTIs, clopidogrel administration for 5 days prior to coronary artery bypass grafting (CABG) was an independent predictor of bleeding risk, need for blood transfusion, reoperation for hemostasis, and duration of treatment. positive value. The situation is more complicated in acute coronary syndromes, where the risk of coronary events increases by 1%/day during discontinuation of loading doses of clopidogrel (300-600 mg) or ticagrelor (180 mg) is A formal recommendation even before coronary angiography is performed, it is therefore important to know precisely whether the patient is likely to undergo surgical revascularization in the emergency or sub-emergency. There is a risk that in the event that endovascular or PCI cannot be treated with stenting, an emergency coronary artery bypass graft surgery is required, which may pose a risk of severe intraoperative bleeding. The bleeding risk associated with ticagrelor is identical to that of clopidogrel, whereas prasugrel increases blood loss by at least 4-fold compared with clopidogrel. Current recommendations relate to the duration of discontinuation of prior antiplatelet agents. during coronary artery bypass surgery as follows:
Clopidogrel: 5 days; Ticagrelor: 5 days; Prasugrel: 7 days.

On the other hand, dual antiplatelet therapy (aspirin + clopidogrel/prasugrel/ticagrelor) should be discontinued for 24-48 hours only when indicated for acute coronary syndromes or during the revascularization period following trans-angiovascular angioplasty. skin (2 weeks) or after stenting (passive stent: 6 weeks; active stent: 6-12 months). Coronary artery bypass grafting is particularly indicated in these cases because it is less likely to bleed.
Thus, pre-anesthesia assessment is an extremely important step, contributing to 50% of the success or failure of heart surgeries that all GMHS doctors specializing in open heart surgery must understand and clearly explain to the patient. before going into major surgery. In addition, there is also an explanation of how open heart surgery is? What will they do for the patient? What are the solutions to overcome pain and complications after surgery? Let the patient really understand everything and be ready to go to the surgery in the most comfortable and gentle mood.
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