Year : 2011 | Volume
: 1 | Issue : 1 | Page : 38--40
Successful anaesthetic management of a case of hypertrophic obstructive cardiomyopathy posted for elective caesarean section using epidural anaesthesia with 0.75% Ropivacaine
Anjali R Bhure, Ketaki S Marodkar
Department of Anaesthesiology, N. K. P. Salve Institute of Medical Sciences, Nagpur, India
Ketaki S Marodkar
1st Floor, Shree Palace, Renghe Nagar, Talmale Layout, Trimurti nagar, Nagpur
Hypertrophic obstructive cardiomyopathy (HOCM) is a complex cardiovascular disorder with autosomal dominant inheritance and an incidence of 0.1-0.5% in pregnant females. Anaesthetic management of a pregnant female with HOCM posted for elective caesarean section is a challenge, as even minor hemodynamic insults may lead to life-threatening complications. We report successful management of one such patient using epidural anaesthesia with 0.75% Ropivacaine.
|How to cite this article:|
Bhure AR, Marodkar KS. Successful anaesthetic management of a case of hypertrophic obstructive cardiomyopathy posted for elective caesarean section using epidural anaesthesia with 0.75% Ropivacaine.J Obstet Anaesth Crit Care 2011;1:38-40
|How to cite this URL:|
Bhure AR, Marodkar KS. Successful anaesthetic management of a case of hypertrophic obstructive cardiomyopathy posted for elective caesarean section using epidural anaesthesia with 0.75% Ropivacaine. J Obstet Anaesth Crit Care [serial online] 2011 [cited 2021 Jan 27 ];1:38-40
Available from: https://www.joacc.com/text.asp?2011/1/1/38/84255
Hypertrophic obstructive cardiomyopathy (HOCM) is the most common genetic cardiovascular disorder transmitted as an autosomal dominant trait, with a prevalence of 1:500 (0.2%) in the general population and an incidence of 0.1-0.5% in pregnant females.  It is characterized by asymmetric hypertrophy of the interventricular septum, resulting in obstruction of the left ventricular outflow tract (LVOT). The hallmark of the condition is the dynamic obstruction of the LVOT, which can lead to sudden death.  Dynamic obstruction of the LVOT can be precipitated by sympathetic stimulation and decrease in preload and afterload to the left ventricle. Thus, it is important to avoid any factor which can lead to tachycardia, hypertension, decrease in venous return to heart or increase in systemic vascular resistance in these patients during anaesthesia.
Aortocaval compression due to gravid uterus reduces preload and labor pains increase the heart rate and hence pregnant HOCM patients may have increased risk of acute LVOT obstruction.  Although general anaesthesia has remained the modality of choice for such patients in the past, it causes laryngoscopy-related stress-induced tachycardia and comparatively more blood loss thereby may trigger LVOT obstruction.  Nowadays, epidural anaesthesia with precise drug titration is a safer and better alternative.  Moreover, with a quick onset, more sensory blockade, prolonged duration of analgesia and less cardiotoxic potential, Ropivacaine is a safe local anaesthetic, especially in obstetric patients.
We report successful anaesthetic management of a 21-year-old female, a known case of HOCM posted for elective caesarean section, using epidural anaesthesia with 0.75% Ropivacaine.
A 21-year-old female, primigravida, came to antenatal clinic with 12 weeks pregnancy and history of exertional breathlessness, giddiness and exertional palpitations since 2-3 days. There was a history of breathlessness on playing in her childhood. Positive family history included death of her mother at the time of her birth and history of sudden deaths in two of her maternal cousins. On general examination, she was averagely built female of weight 48 kg with a regular pulse rate of 78 beats per minute and blood pressure of 106/68 mm Hg. Cardiovascular examination revealed a grade 5/6 pansystolic murmur at cardiac apex and left parasternal region radiating to back and axilla. All the other systems were normal. Urgent ECG and 2D echocardiography were advised. ECG showed wide, peaked p waves, left axis deviation, left ventricular hypertrophy and T wave inversion in leads I, avL and V2. Her 2D echocardiography revealed severe concentric left ventricular hypertrophy, asymmetric septal hypertrophy, moderate mitral regurgitation, diastolic dysfunction with systolic anterior motion of anterior mitral leaflet, an ejection fraction of 55-60% and LVOT gradient of 60 mm Hg. Thus, a diagnosis of HOCM was confirmed. She was advised to take 40 mg of verapamil per orally twice a day, which was gradually increased to 80 mg thrice a day near term. The progress of pregnancy was uneventful from 12 to 36 weeks. At 36 weeks, per vaginal examination revealed moderate cephalo-pelvic disproportion and hence she was posted for elective caesarean section.
After a thorough preanaesthetic examination and routine blood tests, a due high risk consent was obtained and epidural anaesthesia was planned for her lower segment caesarean section (LSCS). She was infused 500 ml of dextrose-saline infusion overnight and kept nil orally the night prior to surgery. On the day of surgery, after confirming availability of compatible whole blood, the patient was taken inside the operation theater and peripheral intravenous access achieved with wide bore cannula. Monitoring included 5-lead ECG, pulse oximetry, temperature, invasive BP monitoring by cannulation of left radial artery with 20-G cannula, central venous pressure (CVP) monitoring by right internal jugular vein cannulation using triple lumen central venous catheter and urine output monitoring by urinary catheter. 5 l/min continuous oxygen was administered by a face mask. Patient was premedicated with intravenous 50 mg of ranitidine and 4 mg of intravenous ondansetron and preloaded with 400 ml Ringer's lactate (RL) solution over 20 min.
With the patient in left lateral position, the space between 3 rd and 4 th lumbar vertebrae was identified and infiltrated with 2 ml of 2% lignocaine after aseptic preparation. The epidural space was identified by loss of resistance to air technique at 3.5 cm and an 18-G epidural catheter was inserted and fixed at 8.5 cm mark. The patient was made supine and a wedge was placed below her right buttock. Epidural test dose was given with 3 ml of 2% lignocaine and vitals were monitored to rule out intravascular or intrathecal placement of catheter. Then, slow and titrated epidural top-up doses of 4, 2, 2 and 2 ml (total 10 ml) of 0.75% Ropivacaine were given to achieve the desired sensory level of 4th thoracic segment. Strict beat-to-beat monitoring of blood pressure was done to keep the systolic blood pressure more than 90 mm Hg. Mild hypotension was encountered twice, approximately 20 min after the last epidural dose and on each occasion, it was treated with 50 mcg of intravenous phenylephrine. Her heart rate remained between 80 and 90 beats per min and there were no episodes of arrhythmia or tachycardia. SpO 2 remained 100% and the patient remained normothermic throughout surgery. A healthy, 2.8 kg, female baby, with an APGAR score of 9/10, was delivered who cried well after birth and was handed over to pediatrician. Slow and titrated infusion of 10 units oxytocin was started and sedation was achieved with 1 mg of intravenous midazolam and 50 mcg of intravenous fentanyl. A total of 1250 ml of IV fluids was infused intraoperatively to maintain a CVP of 6-8 cm H 2 O. Intraoperative urine output was 400 ml.
The patient was shifted to ICU and oxygen was provided via nasal prongs and all monitoring lines were kept in situ. Analgesia was achieved by epidural top-up doses of 6 ml of 0.2% Ropivacaine 8 hourly. CVP and arterial lines were removed after 48 hours. Epidural catheter was removed after 48 hours and oral analgesics were continued to manage the postoperative pain. Patient was shifted to ward on the 4 th postoperative day and was subsequently discharged on the 10 th postoperative day.
HOCM is a complex cardiovascular disease with unique pathophysiological characteristics caused by mutation in genes encoding cardiac sarcomere proteins.  It is unique by virtue of its potential to present during any phase of life from infancy to older than 90 years. Though it is the most common cause of sudden cardiac death, a more balanced perspective regarding prognosis has evolved in which normal longevity is recognized. 
HOCM pathophysiology includes "dynamic" obstruction of LVOT, as obstruction is variable and dependant on volume of blood in ventricle immediately before ventricular systole.  The dynamic obstruction is due to systolic anterior motion of anterior mitral valve leaflet, leading to its contact with the hypertrophied septum. Diastolic dysfunction, increased risk of ischemic heart disease due to abnormal coronary anatomy and dysrhythmias further may complicate hemodynamic balance.  Severity of obstruction is increased by any intervention which reduces ventricular size. Therefore, hemodynamic goals include maintaining adequate preload and afterload and preventing excessive increase in heart rate and contractility.
Pregnancy in HOCM patients poses another challenge to the anesthesiologist. The anxiety, stress and labor pain can cause an increase in peripheral vascular resistance and tachycardia, leading to cardiac insufficiency and pulmonary edema.  Although risk of death during pregnancy is increased in HOCM patients, absolute mortality rate is low and confined only to females who are especially at high risk. 
Our patient received oral verapamil from 12 th week of gestation till her term. Verapamil imparts benefit due to improved ventricular relaxation and filling. Beta-blockers reduce heart rate, improve ventricular filling and reduce myocardial oxygen demand and so can be used, but their use in pregnancy is controversial as they may lead to fetal acidosis. 
We instituted strict intraoperative monitoring including CVP and invasive blood pressure (IBP) monitoring. Poliac et al. have advocated using arterial line for immediate recognition of hypotension and treating it.  Intraoperative transesophageal echocardiography can provide information on development of dynamic outflow obstruction,  but unfortunately this monitoring modality is not available at our institute and would be uncomfortable to the patient without general anaesthesia. Pitton et al. advocate use of systemic and pulmonary artery catheters in obstetric HOCM patients as obstruction may worsen acutely. 
We preloaded our patient with 400 ml of RL as preloading helps maintain stroke volume and prevents sudden reduction in cardiac preload after institution of regional anaesthesia. 
We chose epidural anaesthesia for our patient. Epidural anaesthesia is safe for such patients, provided adequate volume expansion is done.  Even in pregnant females with HOCM having significant LVOT gradient at diagnosis, epidural anaesthesia is tolerated well without any complications. 
We chose 0.75% Ropivacaine over 0.5% Bupivacaine due to its superior sensory blockade, better cardiovascular profile with fewer incidences of conduction disturbances, cardiac collapse and ventricular fibrillation as compared to Bupivacaine.
Use of positive inotropic drugs for treating hypotension in HOCM patients may lead to tachycardia and thereby precipitate LVOT obstruction. Therefore, we used phenylephrine, an α1 adrenergic agonist and a potent peripheral vasoconstrictor without chronotropic side effects.
A bolus or a rapid infusion of oxytocin administration may lead to hypotension and hence we used a slow and titrated oxytocin infusion after baby delivery.
Monitoring of HOCM patients should be continued postoperatively as cardiac failure has been noted even 48 hours postoperatively. Likewise, good analgesia should be given to keep the patient pain free postoperatively. Therefore, we continued IBP and CVP monitoring for 48 hours postoperatively in ICU and kept the patient on epidural analgesia with 0.2% Ropivacaine for 48 hours.
We conclude that epidural anaesthesia with 0.75% Ropivacaine is an effective and safe anaesthetic modality for conducting elective LSCS in patients with HOCM, However a thorough pre anaesthesia assessment, invasive monitoring and prompt correction of perioperative hemodynamic complications is essential.
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