Perioperative cardiac pharmacology
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Transcript of Perioperative cardiac pharmacology
PERIOPERATIVE
MANAGEMENT
OF
PATIENTS ON
CARDIAC DRUGS
INTRODUCTION
Perioperative period is a stressful condition where a number of physiological changes take place which can result in a change in drug requirement.
May be due to altered hepatic or renal function or neuro hormonal changes.
INTRODUCTION
It is estimated that one fourth of all patients undergoing a surgical procedure are taking long-term medications
The issues surrounding the decision to discontinue such medications before surgery and when to reinstitute them are complex
In the preoperative period, it is important to avoid the use of medications that may negatively interacts with anesthetic agents.
INTRODUCTION
Postoperatively,the concern shifts towards avoiding withdrawal symptoms that may develop and possible progression of the underlying disease if the medications are not restarted in a timely fashion
The potential for decreased gastrointestinal motility in the postoperative patient, which may reduce the efficacy of oral medications must be also considered
INTRODUCTION
Antihypertensive medications may cause cardiovascular complications, such as hypotension or myocardial ischemia.
Psychoactive medications may cause prolonged sedation and withdrawal symptoms may develop
Antithrombotic agents may increase the risks of bleeding during surgery
INTRODUCTION
THE ROLE OF THE ANAESTHETIST
IN THE PREOPERATIVE , INTRAOPERATIVE
AND POSTOPERATIVE IS AN IMPORTANT
ONE
BETA BLOCKERS
MECHANISM OF ACTION: Decrease oxygen consumption Improve myocardial metabolism Block the action of catecholamines Decrease sympathetic outflow Shift ODC to right leading to increased oxygen
supply Suppress dysrrhymias LV remodelling
RECOMMENDATION
Perioperative betablocker therapy to be instituted before CABG if LVEF > 30% and preop status allows it.
Pt already on BB should take on morning of surgery and renew it immediate past op
In pt with COPD/reactive airway disease, preferable to use cardio selective agents
ANAESTHETIC IMPLICATIONS
Decrease in HR, decrease in BP and myocardial depressant effects of BB and GA agents appear to be additive
Severe decrease in HR and block may occur with drugs like fentanyl, vecuronium and propofol.
Intubation, incision and extubation occur during periop period result in a surge in endogenous catecholamines.
ANAESTHETIC IMPLICATIONS
ISIS-I study (International study of infarct survival) MIAMI study (Metoprolol in AMI) MAPHY study (Metoprolol Vs Thiazide diuretics
in HT) ASIST study (Atenolol ischaemia study)
-have shown that BB is effective in reducing cardiac complications and could be safely used in the periop period.
CCB - ADVANTAGES
Well tolerated and do not alter exercise tolerance like BB’s
Do not cause fluid retention although ankle edema is a well known side effect.
Control dysrhythmias Prevent coronary artery spasm Anti-HT effect Negative inotropic, chronotropic and dromotropic
CCB – DISADVANTAGES
Low response to inotropes and vasopressors AV node conduction block Peripheral vasodilation after CPB Profound brady cardia and low BP when given in
presence of BB
RECOMMENDATIONS
Preferable to continue CCB upto the time of surgery, including an oral dose on the morning of surgery
ANAESTHETIC IMPLICATIONS
CCB can also enhance the action of muscle relaxants and lowers MAC of inhaled agents
CCB being vasodilators and myocardial depressants are similar to volatile gents – synergistic role
CCB must be administered with caution to patient with impaired LV function or hypovolemia
ACEI/ARA
Renin-AT system plays a significant role in maintaining intraop BP
Inhibitors of this system exaggerate the hypotensive effects of anaesthesia, can cause refractory hypotension and reduced organ perfusion
ANAESTHETIC IMPLICATIONS
Patients treated chronically with ACEI will have significant reduction in MAP,CI,PCWP,SVR and HR in periop period
Increased incidence of low BP at induction requiring vasopressors after induction
RECOMMENDATIONS
Preferable not to continue ACEI/ARA upto day of surgery OMIT on the morning of surgery If continued, it is mandatory to maintain an adequate volume
load and BP with vasopressor, if necessary Discontinue ACEI preop (12 hours preop if captopril (or) 24
hours preop if enalapril) and substitute shorter acting IV anti-HT drugs
ACEI may increase insulin sensitivity and hypoglycemia-concern in DM patients
DIURETICS
Cause significant dyselectrolytemia and fluid imbalance
Should be discontinued preop Efficacy comes down with decrease in GFR
NITRATES
Weightman etal found nitrates to be independent predictors of mortality after CABG surgery
This may be due to tolerance to nitrates which in turn decreases the effectiveness of nitrates causing
decreased vasodilatation of IMA graft, decreased inhibition of platelets, decreased ischaemic preconditioning, decreased sensitivity to vasoconstrictors
NITRATES
Preop discontinuation results in rebound coronary
vasoconstriction and worsening of myocardial
ischaemia
RECOMMENDATIONS
Regarding patients on therapeutic and prophylactic NTG, this agent should be continued until and perhaps beyond induction of anaesthesia, especially in patients who were preop on nitrates for angina
DIGITALIS
INDICATIONS Prevents post operative arrhythmias after lung
surgery Controls ventricular rate in patients with atrial
fibrillation Improves cardiac contractility in patients with
congestive cardiac failure
DISADVANTAGES
Narrow margin of safety Exacerbation of hypokalemic risk –K+
concentration can fluctuate widely during anaesthesia due to fluid shifts,ventilatory acid-base dearrangements and adjuvant treatments
Intraoperative arrhythmia due to digitalis may be difficult to differentiate from those having other sources
DISADVANTAGES
Digitalis toxicity can present with such diverse cardiac arrhythymais on junctional escape rhythm,PVC Ventricular bigeminy or trigeminy,Junctional Tachycardia, PAT with/without, sinus arrest, Mobitz type I and II block or VT
Prophylactic digitalization to prevent arrhythmias after lung surgery has proven ineffective in a number of Randomized controlled studies
RECOMMENDATION
As digitalis has a long blood half-life(36 Hrs),pre-op discontinuation on the day of surgery should not result in a significant decrease in blood levels.
As intravenous preparation is available,the drug can be supplemented if required.
Moreover heart rate can be effectively controlled with b-blockers and cardiac contractility can be increased with inotropes.pre-op discontinuation of digitalis is recommended
AMIODARONE
Antiarrhythmic agent Used to treat recurrent SVT & VT It causes a significant reduction in the incidence of post-op
atrial fibrillation and duration of hospitilization Side effects Pulmonary infiltrates Hypo/Hyperthyroidism
Peripheral neuropathy Deranged LFT Prolonged QT interval
AMIODARONE
Increase quinidine, procainamide, digoxin levels Prolongation of Prothrombin time causing
bleeding in patient on warfarin Amiodarone increase phenytoin levels and
phenytoin enhance the conversion of amiodarone Synergism with BB
RECOMMENDATIONS
As amiodarone has a long T1/2 (29 days), and pharmacologic of effects may persists for over 45 days after its discontinuation, effective preoperatively discontinuation is not feasible
Omit morning dose as IV form is available and is fact acting Risk of discontinuation increases reappearance of life
threatening ventricular arrhythmias Amiodarone has to be started 7 days preop This is both inconvenient and costly
ANTIPLATELET DRUGS
RECOMMENDATIONS
To discontinue, aspirin, clopidogrel & Ticlopidine atleast 5-7 days before surgery to reduce the risk of periop bleeding & reinstitute them when the bleeding risk is diminished.
CONCLUSION
The decision to withhold and restart medications should be based on the
pharmacokinetics and pharmacodynamics of the agent, available clinical data and expert opinion Anaesthetists should exercise diligence in obtaining an
accurate medication history on all preoperative patients and in reviewing the medications in the post operative orders