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 Table of Contents  
CASE REPORT
Year : 2018  |  Volume : 8  |  Issue : 1  |  Page : 43-45

Severe aortic stenosis in a parturient with twins: The challenges


Department of Anaesthesia and Intensive Care, Singapore General Hospital, Singapore

Date of Web Publication13-Apr-2018

Correspondence Address:
Dr. Wan Yen Lim
Department of Anaesthesia and Intensive Care, Singapore General Hospital, 7 Hospital Drive
Singapore
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/joacc.JOACC_50_17

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  Abstract 


Aortic stenosis (AS) in young women is often the result of a congenital bicuspid aortic valve, occurring in 1–2% of the population. Although the anaesthetic management of parturients with AS remains controversial, the high rate of caesarean delivery is consistent among studies. A 30-year-old primi gravida with severe AS presented for elective caesarean section at 36 weeks gestation (twins). She had a failed balloon valvuloplasty 15 years ago and declined further intervention. Prior to induction, invasive lines and prophylactic extracorporeal membrane oxygenation cannulas were placed. A modified rapid sequence intubation technique with propofol/remifentanil target-controlled infusion and suxamethonium was performed. Anaesthesia was maintained using total intravenous anaesthesia. Both twins were delivered uneventfully and oxytocin infusion was commenced. Gradual desaturation to 95% occurred intraoperatively and a focused lung ultrasound and transthoracic echocardiogram were performed. Intravenous frusemide 20 mg was administered empirically. Post-operatively, the patient was extubated and transferred to the Intensive Care Unit for monitoring.Severe AS is associated with high risk of maternal morbidity and mortality. In our case, due to the twin gestation, cardiac output and metabolic demands rise exponentially leading to increased risks. A multidisciplinary approach with appropriate monitoring and point-of-care testing are key to such complex cases to achieve favourable maternal and foetal outcomes.

Keywords: Anaesthesia, aortic stenosis, caesarean section/delivery, parturient, twins


How to cite this article:
Lim WY, Desai SR, Mok MU, Mathews AM. Severe aortic stenosis in a parturient with twins: The challenges. J Obstet Anaesth Crit Care 2018;8:43-5

How to cite this URL:
Lim WY, Desai SR, Mok MU, Mathews AM. Severe aortic stenosis in a parturient with twins: The challenges. J Obstet Anaesth Crit Care [serial online] 2018 [cited 2021 May 18];8:43-5. Available from: https://www.joacc.com/text.asp?2018/8/1/43/230066




  Introduction Top


Aortic stenosis (AS) in young women is often the result of a congenital bicuspid aortic valve, occurring in 1–2% of the population.[1] Although the anaesthetic management of parturients with AS remains controversial, the high rate of caesarean delivery is consistent among studies.[2] Whilst there are published reports on parturient with AS, there is limited documentation on patients with both AS and twin gestation.[3]

Case Description

A 30-year-old parturient with severe AS presented for elective lower segment caesarean section at 36 weeks gestation. This was her first pregnancy with spontaneous twins. She had a failed balloon valvuloplasty 15 years ago and declined further intervention thereafter. She had multiple transthoracic echocardiograms at 14, 24, 32 and 36 weeks of pregnancy, with regular cardiology and obstetric follow-ups. The latest echocardiogram at 36 weeks showed bicuspid aortic valve with commissures at 1 and 6 o'clock, severe AS with valve area of 1 cm 2, peak pressure gradient of 59 mmHg and mean pressure gradient of 39 mmHg.

Cardiothoracic surgeon with extracorporeal membrane oxygenation (ECMO) facility, interventional radiologist and cardiologist were informed prior to surgery. Prior to induction of anaesthesia, invasive lines (arterial line and central venous catheter) and prophylactic ECMO cannulas were placed. Monitoring with 5 lead ECG, pulse oximetry, bispectral index (BIS) were established. A modified rapid sequence intubation technique with propofol/remifentanil target-controlled infusion (TCI) and suxamethonium was performed to maintain haemodynamic stability. Anaesthesia was maintained using total intravenous anaesthesia (TIVA), titrated to BIS values of 40–60, and atracurium 20 mg was administered. Both twins were delivered uneventfully. Oxytocin infusion was commenced and modified B-lynch suture was applied in view of mild uterine atony.

Gradual desaturation to 95% occurred intraoperatively while maintaining FiO2 40% since the start of surgery. A focused point-of-care lung ultrasound and transthoracic echocardiogram (TTE) were performed. A lung recruitment manoeuvre was performed, and intravenous (IV) frusemide 20 mg was administered empirically in view of volume loading secondary to placenta auto-transfusion, with improvement of saturation to 100% on FiO2 40%. Surgery lasted 35 min with 800 ml blood loss. Post-operatively, the patient was extubated and transferred to the Intensive Care Unit for haemodynamic monitoring. She was transferred to general ward on post-operative day 1 and discharged home on day 4.


  Discussion Top


Severe AS is associated with high risk of maternal morbidity and mortality.[2] Guidelines by the American College of Cardiology defined AS as severe when the valve area is <1 cm 2, the mean gradient is >40 mmHg or the peak pressure gradient >63 mmHg.[4] These patients are at high risk of anaesthesia-related complications from the pathophysiology of the cardiac lesion, exacerbated by the cardiovascular changes of pregnancy and augmented by the hemodynamic aberrations caused by anaesthesia.[5] In a study by Tzemos et al., 40% of pregnant patients with AS had left ventricular hypertrophy (LVH) but the degree of hypertrophy was not predictive of adverse outcomes.[6] This contrasts with the findings in older patients with AS where ventricular hypertrophy was associated with adverse outcomes.[7],[8] Whilst recent evidence showed good outcomes in parturients with AS receiving regional anaesthesia, general anaesthesia is often reserved for patients with severe AS as there was no morbidity or mortality reported with this technique.[2]

Compared to pre-pregnancy state, cardiac output in the pregnant patient increases by 25–40% by 24 weeks of gestation. In severe AS, meeting the metabolic demands of pregnancy is challenging due to left ventricular outflow tract obstruction. The rate of cardiac complications can be up to 10%, including risk of arrhythmias and pulmonary oedema.[9] In our case, due to the twin gestation, cardiac output and metabolic demands rise exponentially, and there is potentially a higher risk of morbidity and mortality in the peripartum period. The prophylactic insertion of ECMO cannulas allows for rapid resuscitation and cardiovascular stabilisation in the event of cardiovascular compromise.

Worldwide, propofol has been used extensively for obstetric anaesthesia and scientific literature did not show more adverse maternal or neonatal effects compared to thiopentone.[10] Although there is limited data on the use of TCI propofol, we surmounted the need to have a predictive model by the use of BIS, which has good evidence and is an accepted practice for TIVA worldwide.[11] This was also guided by beat to beat monitoring, which facilitated titration of anaesthetic agents. Our choice of total IV anaesthesia over inhalational agents reduces risk of uterine atony, which may be significant in twin pregnancy.

The choice of concurrent pre-oxygenation with high flow oxygen 15 l/min via facemask prior to induction, as well as nasal oxygen insufflation 15 l/min and triple airway opening manoeuvre during the apnoeic phase helped to maintain SpO2 at 100% during intubation. The patient was positioned with left lateral tilt to reduce aortocaval compression, as well as semi-sitting 20° head up with cricoid pressure to prevent reflux and aspiration. Standard lung protective ventilation with positive end expiratory pressure 5 cm H2O and tidal volume 6 ml/kg was used, to avoid hyperventilation with left shift of the haemoglobin–oxygen dissociation curve, while maintaining haemodynamic stability and fetal oxygen delivery.

Severe AS may potentially result in a fixed cardiac output state with an inability to increase stroke volume. Cardiac output is therefore primarily dependent on heart rate. The presence of LVH may also result in adverse consequences, such as a potential for myocardial ischemia and left ventricle (LV) diastolic dysfunction, as well as LV outflow tract obstruction. Vasodilator therapy is relatively contraindicated as this may lead to reduced systemic vascular resistance, resulting in decreased blood pressure and coronary blood flow, and a compensatory tachycardia which may be detrimental. As such, oxytocin, a potent vasodilator, was administered as an infusion in our case instead of a bolus dose, in order to prevent tachycardia and maintain haemodynamic stability.

Patients with AS tolerate hypotension, vasodilation, hypovolaemia and tachycardia very poorly. They are very preload-dependent, and have a narrow therapeutic window for IV fluid administration, as hypervolaemia in the context of an elevated LV end diastolic pressure may result in flash pulmonary oedema. Delivery of the foetus with release of aortocaval compression, uterine auto-transfusion and excessive IV fluid administration may lead to pulmonary congestion. The use of point-of-care ultrasound in our case allows rapid diagnosis and tailored management, which showed atelectasis with no pulmonary oedema, no pleural effusions, no pneumothorax, no LV or right ventricle (RV) dilatation, and preserved LV and RV systolic function.[12],[13] This was reassuring as it identified an easily treatable cause, and made us certain that she could be extubated at the end of the case. Frusemide 20 mg was administered empirically in view of increased preload and autotransfusion secondary to the twin pregnancy.

In the immediate post-operative period, judicious fluid therapy with close monitoring in ICU/high dependency unit is essential. Optimal pain management post-operatively is crucial to minimise tachycardia, which is detrimental in AS. Multimodal analgesia was adopted with a combination of paracetamol, nonsteroidal antiinflammatory drugs and patient-controlled analgesia (PCA) morphine. Alternatives include regional technique such as transverse abdominis plane block; however, within our hospital and other local institutions, this is not a routine practice, and PCA analgesia leads to good pain relief and patient satisfaction.

Availability of blood gas assessment and real-time on-table point-of-care TTE and lung ultrasound helped guide haemodynamic and ventilatory management intraoperatively.[14],[15],[16] Coordination of specialties (obstetrics, cardiology, cardiothoracic surgery and perfusionists, anaesthesia and neonatalogy) and appropriate intraoperative monitoring are key to such complex cases. Good communication and planning between the multidisciplinary teams is essential.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient has given her consent for her images and other clinical information to be reported in the journal. The patient understands that name and initial will not be published and due efforts will be made to conceal identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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Tamura T, Kobashigawa T, Morishige Y, Morimoto M, Yonei A, Hasegawa M. Epidural anesthesia for cesarean section in a twin pregnant patient with severe aortic stenosis. Masui 1998;47:1212-6.  Back to cited text no. 3
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