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Chapter: Essential Anesthesia From Science to Practice : Clinical management : Pre operative evaluation

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Pre-operative medication management

The last few years have seen increasing interest in the prophylactic use of beta-blockade to reduce peri-operative cardiac morbidity, particularly in patients at high risk for a cardiac event and undergoing major elective non-cardiac surgery.

Pre-operative medication management

Peri-operative beta blockade

The last few years have seen increasing interest in the prophylactic use of beta-blockade to reduce peri-operative cardiac morbidity, particularly in patients at high risk for a cardiac event and undergoing major elective non-cardiac surgery. The target of this therapy is a heart rate of 70 beats/min and systolic BP of 110 mmHg – if tolerated by the patient. If the patient is not currently on beta-blockers, a cardioselective agent (atenolol or metoprolol) is recommended. Unless contra-indicated, this blockade should be initiated as early as possible and maintained throughout the hospitalization and after discharge (at least 30 days and probably longer).

Antihypertensives

Angiotensin-converting enzyme (ACE) inhibitors (and angiotensin II antagonists) have been linked to severe and refractory intra-operative hypotension under anesthesia. Unless the patient has very severe hypertension, many recommend discontinuation of these medications the day before surgery. Similarly, many advocate discontinuing diuretics the morning of surgery, both for the patient’s comfort (if awake) and for intra-operative fluid management. If the diuretic is for acute CHF, however, it should be continued. Otherwise, antihypertensive drugs should be continued the morning of surgery. In particular, agents with a known rebound phenomenon, i.e., clonidine and beta-blockers, must be continued or refractory hypertension may result. Because patients are instructed to be fast-ing, we must actually tell them to take their antihypertensives or risk significant hypertension in the pre-operative holding area.

Anticoagulants

Many patients are on some form of platelet inhibitors. While single agent ther-apy poses no problem for most operations, multi-modal platelet inhibition may increase the risk of peri-operative bleeding.

·           Non-steroidal anti-inflammatory agents (NSAIDs, including aspirin (ASA)) These can be safely continued unless there are special surgical (aesthetic plastic surgery, neurosurgery) or anesthetic (nerve block) considerations, or the patient is on multi-modal therapy. Many surgeons, however, want ASA discontinued 2 weeks prior to surgery and other NSAIDs stopped for at least several days, even though we lack evidence that this alters the incidence of intra-operative blood loss. Actually, it may increase the incidence of thrombotic complications (deep vein thrombosis (DVT), coronary thrombosis, thrombotic stroke), and prevent the pre-emptive analgesia and opioid-sparing capacity of pre-operative NSAIDs.

·           Platelet-function inhibitors (ticlopidine (Ticlid®), clopidogrel (Plavix®)) If thepatient receives multi-modal therapy, consider switching to a single agent. We must weigh the risks of discontinuing anticoagulation, with the risk of intra-operative or anesthetic-induced bleeding. Because of their prolonged half-lives, regional anesthesia would mandate discontinuing these agents many days (ticlopidine: 10–14 days; clopidogrel: 7 days) prior to surgery.

·           GP IIb IIIa inhibitors (abciximab (Reopro®), eptifibatide (Integrilin®), tirofiban (Aggrastat®)) These should be stopped prior to surgery and can be reversedwith transfusion of platelets. However, patients on these agents usually need the anticoagulation. These drugs represent a contraindication to regional anesthesia.

·           Heparin Subcutaneous prophylactic dosing probably need not be discontinuedunless a regional anesthetic is to be administered (4 h), but Lovenox® (low molecular weight heparin) should be stopped 12 h before surgery.

Monoamine oxidase inhibitors (MAOIs)

These agents interact with many drugs and may result in severe hypertension if indirect-acting vasopressors are administered. Even more worrisome are excita-tory/depressive (central serotonin syndrome) reactions with administration of opioids. In particular, meperidine (Demerol®) is absolutely contraindicated in these patients. Some still advocate discontinuation of these agents for 2 weeks pre-operatively.

Herbal remedies

Public enthusiasm for herbal supplements has its drawbacks. The following are current considerations together with the recommended discontinuation period prior to surgery:

·           Ephedra – works like ephedrine with direct and indirect sympathomimetic effects and all the consequent side effects including intra-operative hemo-dynamic instability from depletion of endogenous catecholamines; 24 h

 

·           Garlic – inhibition of platelet aggregation and increased fibrinolysis; 7 d Ginkgo – inhibition of platelet-activating factor; 36 h

 

·           Ginseng – hypoglycemia, inhibition of platelet aggregation; 7 d St. John’s Wort – induction of cytochrome P450 enzymes; 5 d

 

·           Others are sedatives such as Kava and Valerian, perhaps reducing the need for additional sedative agents – titrate!


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