outline the critical physiological changes of pregnancy. the critical physiological changes of...
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OutlineThe critical physiological changes of pregnancy.
Predictors of cardiac events during pregnancy
Risk of cardiovascular complications during pregnancy
Anesthetic management parturient with valvular diseases.
What are the critical physiological changes of pregnancy that affects a parturient with cardiac disease ?50% increase in the blood volume40% increase in cardiac output25% 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.
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%).
Many of the signs and symptoms of normal pregnancy can mimic those of cardiac disease.For example: Dyspnea due to LV failure From Labored breathing typical of normal pregnancy Leg edema due to CHF From Venous stasis due to aortocaval compression
heart murmurs due to organic lesions from those due to increased blood flow Rotation of the maternal heart, because of elevation of the diaphragm from cardiac hypertrophy.
C.O: 30-50% during gestation 30-45% during labor After delivery 50%of patients with symptoms of heart disease during minimal activity or at rest when not pregnant develop CHF during pregnancy. Circulatory Changes and Co.ExistingHeartDisease
Risk of cardiovascular complications during pregnancy
Low risk of complications ( 1%):Corrected tetralogy of fallotAtrial septal defectVentricular septal defectPatent ductus arteriosusMild pulmonic or tricuspid valve diseaseMitral stenosis (NYHA class I, II)Mild regurgitant valve lesionBioprosthetic valveCompensated heart failure (NYHA class I, II)
Intermediate risk of complications (5-15%):Mechanical valve prosthesisAortic stenosis (mild to moderate)Mitral stenosis with atrial fibrillationMitral stenosis (NYHA class III, IV)Uncorrected cyanotic congenital heart disease (tetralogy of fallot)Uncorrected coarctation of the aortaPrevious myocardial infarction
High risk of complications or death (25%):Pulmonary hypertension (severe)Eisenminger syndromeMarfan disease with aortic root involvementPeripartum cardiomyopathySevere aortic stenosisNYHA class IV heart failure
One of the most common maternal heart diseases are: Acquired valvular heart diseases included: MS (the most common type of cardiac( valvular defect in pregnant MR (the second most common cardiac valvular defect seen in pregnancy) AS ( rarely seen in pregnancy) AI ( is not common in pregnancy)
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.
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).
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.
Mitral stenosis (cont.):
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.
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.
There are increased incidence of: Pulmonary edema Atrial fibrilation Paroxismal atrial tachycardiaControl of the heart rate is critical Excessive perioperative fluid administrationTrendelenburg position Autotransfusion (via uterine contraction) central blood volume CHF.
Pregnant patients with Mitral Stenosis
Invasive monitoring is usually not necessary in the absence of cardiac symptoms. Exceptions are parturients with: Pulmonary hypertension Right-to-left intracardiac shunts Coarctation of the aorta invasive cardiac monitoring should be continued for 48 hours after delivery
Spinal anesthesiaFor most elective and urgent C/SEpidural anesthesiaDecrease likelihood of hypotensionCombined Spinal-Epidural anesthesiaGeneral anesthesia
Advantages : -A decreased risk of failed intubation and aspiration of gastric contents -Avoidance of depressant agents -The ability of the mother to remain awake and enjoy the birthing experience - Reduced blood lossDisadvantages: - Dural puncture - Reduced SVR & BP - Slower onset
Neuraxial anesthesia techniques
Advantages: - Speed of induction - Control of the airway - Superior homodynamic Disadvantages: - Failed intubation - Pulmonary aspiration of gastric contents - Neonatal depression - Maternal awareness
General anesthesia technique
Regurgitation of blood through an incompetent mitral valve chronic volume over load and dilatation of the LA
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.Mitral Regurgitation (MR):
Anesthetic consideration:Primary considerations are:Maintain slightly increased heart ratePrevent increase in SVR.Prevent hypoxemia, hypercarbia, acidosis which may increase PVR.Avoid aortocaval compression and myocardial depression.
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
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.Anaesthetic considerations:
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.
Anaesthetic considerations:Prevent catecholamine induced increases in SVR due to pain, and avoid bradycardia, which may increase regurgitant flow.