Planning and Risk Stratification of Parturient with Heart Disease
An anesthesiology consultation should occur in advance of delivery in patients with cardiac disease to review the patient’s anesthetic, obstetric and cardiac history with particular attention to the following:
• Functional status
• Intra-cardiac shunting and cyanosis
• Prior arrhythmias
• Pacemaker or defibrillator
• Left heart obstructive lesions
• Prior or current episodes of heart failure
• Left and right heart function.
Modified WHO Classification for Pregnancy
Obstetric Management of Parturient with Heart Disease
Typically, cardiac disease is not an indication for cesarean delivery. Exceptions may include patients with aortic dissection, aortic dilation of > 4.5cm, patients anticoagulated with warfarin at the time of delivery, patients with severe pulmonary hypertension or patients who are in distress requiring intubation or vasopressor administration. Many obstetricians perform a “cardiac delivery” for laboring parturients with significant heart disease. Such a delivery involves an early, dense epidural followed by a passive second stage(no pushing) and a forceps or vacuum delivery. With this technique, catecholamine release is limited by excellent pain control, and hemodynamic fluctuations from maternal expulsive efforts are avoided.
However, the risks of a surgical vaginal delivery to both the parturient (e.g. trauma, bleeding) and the neonate (e.g. head injury) need to be weighed against the potential hemodynamic compromise of maternal expulsive efforts.
Labor Analgesia and Monitoring
· A “cardiac delivery” with a passive second stage involves an excellent epidural and an involved anesthesia team. In this technique, after uterine contractions bring the fetus to the pelvic floor, low or outlet forceps or vacuum is used to avoid maternal Valsalva.
· Neuraxial analgesia is important in the cardiac parturient for it reduces catecholamine surges from labor pain that can result in tachycardia, hypertension, increased cardiac output, and ventricular stress.
· Maintaining a dense epidural not only decreases such cardiac stress but it also decreases the degree of hemodynamic alteration should an urgent cesarean delivery be required and the epidural need to be converted to a surgical block quickly.
· Monitoring: Pulse oximetry plus tocodynonometer machine. Laboring women with heart disease should have a pulse oximeter with a waveform for assessment and audible alarms. If the patient has a history of a tachyarrhythmia, ischemic heart disease, aortic stenosis or hypertrophic cardiomyopathy, then 5-lead ECG telemetry should be utilized during labor and delivery. Occasionally, an arterial line could be placed for labor management. Rarely would a central line or pulmonary artery catheter be necessary during labor.
The physiologic implications of pregnancy and the anesthetic goals for some common valvular and CHD lesions are reviewed in the table given below. Many parturient with CHD have multiple different lesions that have been repaired with various techniques resulting in complex hemodynamic physiology. In contrast, patients that have had complete repairs, for example, repaired tetralogy of Fallot with little residual hemodynamic defect, can have few physiologic concerns. However, experts in CHD emphasize that a “repair” is not a “cure” or complete “correction,” and therefore patients with CHD, even with good repairs, should be followed by a CHD specialist and have their labor and delivery occur at tertiary centers if possible.
Anesthesia for Cesarean Delivery
Regional anesthesia (single-shot spinal, an epidural, a combined spinal-epidural (CSE), or a continuous spinal technique) is typically preferred unless the patient is anticoagulated (risking spinal hematoma) or is critically ill and thereby unable to lie flat or maintain their natural airway. Further, with some CHDs, such as Fontan circulation, maintenance of spontaneous respirations with a neuraxial approach may result in more optimal hemodynamics. Alternatively, general anesthesia may be dictated by obstetric or anesthetic indications.
Spinal Anesthesia:
· The rapid decrease in preload and afterload - may carry additional risk in some cardiac lesions (eg, severe mitral stenosis, severe aortic stenosis, aortic coarctation, or patients at risk for right-to-left shunting).
· An arterial line placed prior to the spinal anesthetic with a carefully titrated phenylephrine infusion initiated at the time of the spinal anesthetic may provide adequate hemodynamic stability.
Epidural Anesthesia:
· Least cardiovascular disruption (slow onset).
· Addition of an opioid when dosing the neuraxial anesthetic (improve both intraoperative and postoperative analgesia; reduce local anesthetic dose).
· The elimination of epinephrine from the epidural test dose or loading dose will eliminate the possible deleterious effects of systemic epinephrine.
· May not provide the density of block that intrathecal local anesthetics provide.
Combined Spinal-Epidural Anesthesia (CSEA):
· Allows the anesthesiologist to maintain preload and afterload during the onset, while still achieving the greater block reliability of intrathecal local anesthetic administration.
· Cautious intravenous hydration and/or gentle titration of a phenylephrine infusion or ephedrine boluses are options to counteract the hemodynamic effects of surgical neuraxial block.
Arrhythmias and Management of Cardioverter Defibrillators during Labor
· Patients with a history of arrhythmias should have 5-lead ECG monitoring during labor.
· Maternal cardioversion can be performed in pregnancy.
· If the patient has a fetal scalp electrode, this should be removed prior to the cardioversion.
· Automatic implantable cardioverters defibrillators should be left “on” in labor as these provide the most rapid response to a tachyarrythmia.
· A magnet should be immediately available to use in the event of an emergent cesarean delivery requiring unipolar cautery.
Beta Agonist Drugs in Labor
· Beta agonist drugs such as terbutaline are occasionally used in labor to urgently relax the uterus when uterine hyperstimulation or tachysystole results in fetal compromise.
· It is important for the obstetric team to be aware that this drug is contraindicated in some cardiac lesions. Patients with Hypertrophic Obstructive Cardiomyopathy (HOCM) could have infundibular spasm and/or worsen their outflow gradient as a result of beta agonism.
· Likewise, patients who would not tolerate tachycardia or patients with a history of tachyarrhythmias should not receive beta agonist drugs in labor.
Management of Obstetric Hemorrhage in CHD Parturient
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