Practical Approach to Anesthesia for Parturient with Cardiac Disease

1. Practical Approach to Anesthesia for Parturient with Cardiac Disease CMEC 21st July 2009 by Nadine Mohamed Mamdouh Habib

2. Outline • The critical physiological changes of pregnancy. • Predictors of cardiac events during pregnancy • Risk of cardiovascular complications during pregnancy • Anesthetic management parturient with congenital and valvular diseases.

3. What are the critical physiological changes of pregnancy that affects a parturient with cardiac disease ? • 50% increase in the blood volume • 40% increase in cardiac output • 25% increase in heart rate to approximately 80-100 beats/min. • Reduced systemic vascular resistance and pulmonary vascular resistance. • Labor and delivery itself imposes approximately 50% increase in CO and oxygen demand.

4. The main predictors of cardiac events during pregnancy are: • Prior cardiac events: (heart failure, transient ischemic attack, stroke, or dysrrhythmias). • Baseline New York Heart association functional class≥ II or the presence of cyanosis. • Left heart obstruction: (mitral valve area ≤ 2cm2, aortic valve area ≤ 1.5 cm2, or left ventricular outflow tract gradient ≥ 30mmHg by echocardiography). • Reduced left ventricular function (ejection fraction ≤ 40%).

5. Risk of cardiovascular complications during pregnancy

6. Low risk of complications (≤ 1%): • Corrected tetralogy of fallot • Atrial septal defect • Ventricular septal defect • Patent ductus arteriosus • Mild pulmonic or tricuspid valve disease • Mitral stenosis (NYHA class I, II) • Mild regurgitant valve lesion • Bioprosthetic valve • Compensated heart failure (NYHA class I, II)

7. Intermediate risk of complications (5-15%): • Mechanical valve prosthesis • Aortic stenosis (mild to moderate) • Mitral stenosis with atrial fibrillation • Mitral stenosis (NYHA class III, IV) • Uncorrected cyanotic congenital heart disease (tetralogy of fallot) • Uncorrected coarctation of the aorta • Previous myocardial infarction

8. High risk of complications or death (≥25%): • Pulmonary hypertension (severe) • Eisenminger syndrome • Marfan disease with aortic root involvement • Peripartum cardiomyopathy • Severe aortic stenosis • NYHA class IV heart failure

9. Congenital heart disease • Prevention of accidental intravenous infusion of air bubbles • A slow onset of epidural analgesia is preferred • Supplemental O2 should be given to the patient • Hypercarbia and acidosis should be avoided

10. Tetralogy of Fallot (TOF) • TOF is the most common etiologic factor in the right to left shunt. • TOF consists of 4 structural abnormalities: • Ventricular septal defect (VSD) • Right ventricular hypertrophy (RVH) • Right ventricular outflow obstruction • Overriding of the aorta

11. In patients with uncorrected lesion, anaesthetic considerations must focus on minimizing the haemodynamic changes that would increase right to left shunting: • decrease in SVR. • decrease in venous return. • or myocardial depression. • In patients who had successful surgery in infancy or childhood, no special treatment is required; antibiotic prophylaxis is recommended

12. Anesthtic technique: Choice of induction agents for general anaesthesia: narcotic induction with etomidate. • Neonatal depression as a result of narcotic induction can be easily treated with endotracheal intubation • Invasive monitoring is mandatory and arterial line or CVP line is preferred to pulmonary artery (PA) catheter. CVP may be more useful (as the right ventricle is at the greatest risk of dysfunction). • Single shot spinal anaesthesia should be avoided. Slow induction of epidural may be advisable with caution.

13. Eisenmenger Syndrome • A chronic uncorrected left to right shunt  produces right ventricular hypertrophy (RVH)  elevated pulmonary artery pressure  right ventricular (RV) dysfunction. • The primary lesion is usually ASD, VSD or PDA.

14. Eisenmenger Syndrome (cont.) • The pulmonary and the RV musculature undergoes remodeling in response to the chronic pulmonary volume overload  the high fixed pulmonary artery pressure limits flow through the pulmonary vasculature and when pulmonary artery pressure exceeds the level of systemic pressure  reversal of shunt flow occurs. • The initial left to right shunt becomes a right to left shunt, ultimately leading to the Eisenmenger syndrome: which includes the sequelae of arterial hypoxaemia, and RV failure.

15. Clinical manifestations: • Dyspneoa, • Clubbing of nails, • Polycythemia • Peripheral oedema • Cynosis. In an established case of Eisenmenger syndrome, surgical correction of the defect is unhelpful and may increase mortality.

16. Anaesthetic consideration: • Avoid any decrease in the SVR insufficient RV pressure required to perfuse the hypertensive pulmonary arterial bed and may result in sudden death of the patient. • Acute arrhythmias are particularly dangerous as these patients have little or no cardiac reserve and need a normal sinus rhythm to keep up with the increased workload. • Ampicilin and gentamycin i.v. should be given as prophylaxis against infective endocarditis and repeated eight hourly after the initial dose.

17. Anesthetic technique: • O2 should be administered to all patients undergoing surgery under regional anaesthesia, as O2 reduces pulmonary vascular resistance, which benefits the patient with Eisenmeneger. • Caesarean section can also be conducted under general anaesthesia (but several disadvantages): • Effects of IPPV on venous return • ventilation/perfusion mismatch • high pulmonary artery pressure • increased shunt through the anatomic defect • myocardial depression by halogenated agents • Monitoring includes invasive blood pressure monitoring (A-line), and central venous pressure (CVP) monitoring (Pulmonary artery catheter (PA) use is controversial). • The blood loss should be promptly replaced by crystalloids, colloids, or packed cells. Postpartum autotransfusion may cause intravascular volume overload in these patients. Regional anaesthesia may reduce the risk of postoperative deep vein thrombosis. • Titrated epidural anaesthesia is probably the prefered regional technique, a dilute solution of phenylephrine may be given as needed to maintain maternal SVR.

18. Valvular Heart Disease: • In general regurgitant valvular lesions are well tolerated during pregnancy, where as stenotic lesions have a greater potential for decompensation. • Pregnant patients with valvular heart disease can expect to have worsening of their New York Heart Association (NYHA) functional class, while others may have adverse foetal outcome i.e. preterm birth or still birth.

19. Mitral stenosis (MS): • Normal mitral valve orifice has a surface area of4-6cms2, in mild stenosis the valve area (1.5 to 3 cm2), moderate mitral stenosis the valve area (1.1 to 1.5 cm2), while severe mitral stenosis the valve area (less than 1cm2).

20. Mitral stenosis (cont.): • Mitral valve stenosis prevents emptying of the left atrium (LA), with increased left atrial and pulmonary artery pressure, resulting in dyspnoea, haemoptysis and pulmonary oedema.

21. Peripartum considerations: The hyperdynamic state of pregnancy is poorly tolerated by women with severe mitral stenosis: • Increased plasma volume can cause pulmonary edema and worsen the left atrial enlargement. • Tachycardia decreases the left ventricular diastolic filling through the stenotic valve. • AF is common with MS, with loss of the atrial kick; which accounts for = 30% of the left ventricular stroke volume. Medical management of AF by a beta-adrenergic blocking agent.

22. Anesthetic considerations: • Should be based on the severity of the lesion,( according to the valve area, and the hemodynamic stability of the patient). • Avoid increased heart rate. • Maintain venous return and SVR. • Avoid aorto-caval compression. • Treat atrial fibrillation (AF) aggressively. • Maintain sinus rhythm. • Prevent pain, hypoxaemia, hypercarbia and acidosis as these can increase PVR.

23. Anesthetic technique • Slow epidural anaesthesia may be conducted with caution to maintain hemodynamics. • Prophylactic ephedrine administration should be avoided. If a need for vaspressor arises, the drug of choice in patients with MS is low dose phenylephrine.

24. General anaesthesia • The cardiovascular effects associated with laryngoscopy and intubation and oral suction should be minimized. • Induction agent should not produce wide swings in the haemodynamics( Etomidate is a suitable induction agent). A beta-blocker such as esmolol and a modest dose of opioid should be administered before or during the induction of general anaesthesia. • Oxytocin should be used with care, a dilute solution instead of bolus dose is recommended. • Emergence must be carefully controlled to avoid tachycardia.

25. Mitral Regurgitation (MR): • Regurgitation of blood through an incompetent mitral valve  chronic volume over load and dilatation of the LV • In the acute type, there is acute pulmonary congestion and pulmonary edema results. • If the patient survives this episode of acute mitral regurgitation, pulmonary artery pressure continues to increase and right heart failure occurs.

26. Anesthetic consideration: Primary considerations are: • Maintain slightly increased heart rate • Prevent increase in SVR. • Increase in the central blood volume. • Prevent hypoxemia, hypercarbia, acidosis which may increase PVR. • Avoid aortocaval compression and myocardial depression.

27. Anesthetic technique: • Epidural anaesthesia prevents increase in SVR, promotes forward flow of blood and helps to prevent pulmonary congestion. • If general anaesthesia is required: ketamine and pancuronium are desirable agents in these patients. • Atrial fibrillation (AF) must be treated promptly, and haemodynamic instability associated with AF warrants immediate cardioversion. • Invasive (intra-arterial) BP monitoring, and pulmonary artery catheter monitoring are advisable in severe cases.

28. Aortic stenosis (AS): • The pathophysiology of severe AS entail a narrowing of the valve to less than 1 cm2 associated with a trans-valvular gradient of 50mmHg with significant increase in after load to the LV. • A valvular gradient which exceeds 100mmHg carries an increased risk of myocardial ischemia as the LV hypertrophies significantly. • In aortic stenosis transvalvular gradient increases progressively throughout pregnancy, due to increasing blood volume and decreasing SVR

29. Anaesthetic considerations: • Avoid tachycardia (decrease time for coronary perfusion of the hypertrophied LV), and bradycardia (slow heart rate decreases CO). • Maintain intravascular volume and venous return. • Avoid aortocaval compression and myocardial depression. • Arrhythmias are not well tolerated and should be promptly treated. • Patients with trans-valvular gradient more than 50mmHg with symptomatic AS should have invasive monitoring i.e. A-line and PA catheter in place.

30. Anesthetic technique: • General Anaesthesia :Drugs of choice are a combination of etomidate and modest dose of opioids with succinylcholine for rapid sequence intubation. • Myocardial depression associated with volatile anaesthetic agents should be avoided. • Oxytocin should be avoided as it is known to cause marked vasodilation, with hypotension. The drug of choice for uterine contraction is ergometrine at the end of delivery. • PA catheter monitoring is controversial, as it entails a high risk of ventricular arrhythmias • CVP monitoring is desirable and should be maintained at a high normal level to protect cardiac output during unexpected peri-partum haemorrhage. • Regional anesthesia better avoided due to the risk of fall in SVR, that is poorly tolerated in patients with a fixed cardiac output.

31. Aortic regurge (AR): • The pathophysiology is chronic volume overload of the LV, with hypertrophy and dilatation and increase in LV End Diastolic Volume (LVEDV), decrease in ejection fraction (EF) and signs and symptoms of pulmonary edema. • Patients with aortic insufficiency tolerate pregnancy well as pregnancy results in a modest increase in heart rate.

32. Anaesthetic considerations: Prevent catecholamine – induced increases in SVR due to pain, and avoid bradycardia, which may increase regurgitant flow.

33. Anesthetic technique: • Epidural anaesthesia decreases the after-load, and prevents increases in SVR and acute LV volume overload in these patients. • General anaesthesia may be induced with etomidate to prevent severe haemodynamic swings, followed by intubation of the trachea with suxamethonium. • Remi-fentanil can be used as an infusion during induction and maintenance of anaesthesia and provides haemodynamic stability. • Neonatal respiratory depression is known to occur with remi-fentanil. It is treated with endotracheal intubation and no further medical management is required for the neonate.

34. Postoperative period in parturients with cardiac disease: • In the postoperative period, patients with severe cardiac dysfunction delivered by Caesarean section should be kept in the High Dependent Unit (HDU) / intensive care unit (ICU) for aggressive monitoring of fluid therapy, oxygen saturation and haemodynamics. During the first 24-72 hours significant fluid shift occurs, which may lead to CCF. • Adequate post-operative analgesia should be provided in the form of continuous epidural analgesia or patient controlled IV analgesia. Early ambulation to minimize the risk of deep venous thrombosis should be weighed against the risk of cardiovascular stress.

35. Thank you!