Hypoxia In A Post-Partum Patient

Question 1

A 36-year-old female, who has just delivered, is complaining of dyspnoea.
Her oxygen saturations are 88% on room air.

What are the possible causes for hypoxia in this patient?

Answer 1

Anaesthetic causes:
* Opiate overdose (remifentanil, or following a general anaesthetic).

• High neuraxial blockade if epidural in situ.

Obstetric causes:
* Major obstetric haemorrhage.
* Pre-eclampsia.
* Peripartum cardiomyopathy.
* Amniotic fluid embolus.
* V/Q mismatch (carboprost).

Other causes
* Pulmonary embolus.
* Sepsis.
* Anaphylaxis.
* Exacerbation of asthma.
* Myocardial infarction.
* Structural cardiac problem (valvular or septal defect).
* Arrhythmias.

Question 2

What is your initial management for this patient?

Answer 2

• This is a medical emergency that requires urgent assessment and intervention. Initial management for this patient includes:
• Immediate ABCDE assessment prioritising the airway and breathing to determine the cause of hypoxia and facilitate specific treatment.
• 100% oxygen through a non-rebreathe mask and ensuring large bore intravenous access.
• Urgent senior anaesthetic and obstetric help, with early consideration of the intensive care team if rapid deterioration.

Question 3

What are the risk factors for the development of a peripartum cardiomyopathy?

Answer 3

• Increased maternal age.
• Multiparity.
• Ethnic minority (Nigeria, Haiti).
• Twin pregnancy.
• Chronic or new onset hypertension.
• Prolonged tocolysis.

Question 4

What is the pathophysiology in patients with a peripartum cardiomyopathy?

Answer 4

• The pathophysiology of peripartum cardiomyopathies is complex, and is currently based on a “2 hit” model: a genetic predisposition together with the effect of prolactin.
• Prolactin is broken down into a smaller fragment (16kDa), which is thought to exert cardiotoxic effects resulting in apoptosis and death of cardiac myocytes.
• Primarily patients display symptoms suggestive of left ventricular systolic dysfunction leading to biventricular dysfunction and cardiac failure.
• The disease cause is thought to be multi-factorial to include immune or hormone mediated, inflammatory and genetic.
• For a diagnosis of peripartum cardiomyopathy to be made, the specific criteria are:

1. Cardiac failure at the end of pregnancy or up to five months after delivery.
2. No other likely cause for cardiac failure.
3. New onset of symptoms.
4. Left ventricular dysfunction.

Question 5

An urgent echocardiogram shows an ejection fraction of 32%.

What are the next steps in the management of this patient?

Answer 5

• Stabilisation of this patient, referral to the cardiology team and admission to the coronary care or intensive care unit as appropriate.
• Multidisciplinary team management to include obstetricians, tertiary cardiology and anaesthetists.
• Medical management of acute cardiac failure using ACE inhibitors, nitrates, beta blocking agents and diuretics as directed by specialists.
• Supportive therapy and counselling for the patient and her partner.
• Severe cases may require further specialist intervention including the use of intra-aortic balloon pumps, cardiac implantable devices and left ventricular assist devices.
• Anti-coagulation and/or DVT prophylaxis should be considered.
• There is a possible role for bromocriptine in these patients; small studies currently suggest that suppression of prolactin production reduces the severity of PPCM and improves the rate of recovery.

Question 6

Two years later this patient remains stable on medical therapy. She is keen to have another baby.

How should she be counselled?

Answer 6

• Detailed medical assessment to determine her cardiac and other comorbidities, in order to evaluate whether the patient would be able to tolerate the physiological demands of pregnancy.
• Absolute contraindications to pregnancy include pulmonary hypertension and severe cardiac failure, which suggest a high risk of morbidity and mortality.
• The risks of pregnancy should be explained to the patient based on her current status. If her ejection fraction has not recovered to >50%, then the risk of mortality is 25%–50%. If her ejection fraction has normalised, there is a 20% risk of deteriorating left ventricular function during pregnancy.