Issues specific to the care of a pregnant ICU patient

This chapter discusses various pregnancy-related issues which come up uniquely in the intensive care environment. This vague and nebulous topic has never come up in the exam, which is not surprising. On one hand, one might expect something like that from the college ("Discuss the issues related to the management of a pregnant patient in Intensive Care", they might ask). However, if you think about it the possibility is fairly remote. Such a question would be essay-like, and therefore difficult to mark effectively. Many response would fall into the "any reasonable response" category. 

These considerations notwithstanding, pregnant patients do end up in the ICU, and they are a population which poses some unique challenges irrespective of what they presented with (be it a pregnancy related catastrophe like PPH or something completely unrelated). The purpose of this chapter is to combine these issues into some sort of easily recalled list. Most of this information was scraped together out of Oh's Manual and the excellent article by Trikha and Singh (2010). 

Respiratory and ventilation issues:

• Permissive hypercapnea is not permitted, as it will decrease the affinity of foetal haemoglobin for oxygen, thereby decreasing foetal oxygenation. Keep the PaCO₂ under 45mmHg. In fact, it should be lower than that (between 30-35mmHg) as it would normally be in later pregnancy.
• Permissive hypoxia is also not permitted: to improve the chances of transplacental oxygen trasnfer the PaO₂ of the mother should never be allowed to slip to 60-65mmHg as you might do in some crusty COPD derelict. Saturation should remain above 95%. 
• If they get ARDS, you will find it difficult to prone-ventilate them (though some have tried with substantial success - see this case report by Samanta et al, 2014 who safely ventilated a third-trimester patient with H1N1 ARDS)

Circulatory issues

• The placental vessels are said to be more sensitive than other vessels to the effects of noradrenaline (Dornhorst et al, 1952). Theoretically, this means that the placental blood flow will be impaired by high noradrenaline doses. Practically, nobody ever cares about this because the placental blood flow will be even more impaired when the hypotensive mother dies of septic shock. 
• The pregnancy-associated changes in Starling eqiation variables results in an increased propensity toward pulmonary oedema. Large-volume fluid resuscitation needs to be reconsidered.
• Some cardiovascular drugs are forbidden:
  • ACE-inhibitors and ARBs
  • Nitroprusside
  • Spironolactone
  • Statins
  • GTN (in PPH, it relaxes the uterus - which is undesirable)
• Corticosteroids should not be used for sepsis in the first trimester - they may cause a cleft palate.
• Cardiac output is supposed to be supra-normal; the usual ScvO₂ of a pregnant woman is around 80%. Ergo, a "normal" cardiac output is actually abnormally decreased. 
• ECMO is associated with an increased risk of intrauterine haematoma (eg. this case report from Steinack et al, 2016) but it has been done.

Issues with analgesia sedation and paralysis

• Most of these drugs cross the placenta, producing a sluggish or comatose neonate.
• Prolonged neuromuscular blockade can cause arthrogryposis, nasty congenital joint contractures.

Metabolic and nutritional issues issues

• The postpartum patient may be somewhat hypoglycaemic because of increased demand for glucose - it ends up being used up in the process of milk synthesis. In short, you are going to either need to supplement extra nutrients, or use less insulin (Riviello et al, 2009).
• In general nutritional requirements will be increased. On top of the usual 25kcal/kg/day, one needs to add food for the foetus -  around 452 kcal/day in the third trimester and 340 kcal/day in the second trimester.
• Protein content should be twice the normal amount.
• Dietary iron content should also be doubled

Renal and fluid balance issues

• Increased GFR means the clearance of drugs is more rapid
• Increased body water has implications for the volume of distribution of water-soluble drugs

Gastrointestinal issues

• Gastric empyting and peristalsis will be significantly impaired. Post-pyloric feeding may be required, if not TPN.
• Abdominal compartment pressure measurements are going to give wildly incorrect numbers

Haematological issues

• In abruption, thromboplastin is released, causing DIC. Also, in amniotic fluid embolism. 
• They are at 5 times greater risk of thromboembolism.
• Warfarin is contraindicated (as it is teratogenic)

Infectious disease issues

• Pregnancy limits your choice of antibiotics:
  • vancomycin (renal toxicity)
  • sulphonamides (neontatal jaundice)
  • tetracycline (abnormal bone and teeth development)
  • chloramphenicol (grey baby syndrome)
  • Antifungals (fluconazole, itraconazole, ketoconazole, griseofulvin) - pretty much the only antifungal thought to be safe for use in pregnancy is amphotericin.
• Beta-lactams, aminoglycosides and macrolides are generally safe.

Administrative issues

• APACHE scoring is frustrated by pregnancy: physiologic changes during pregnancy lead to elevated APACHE-II scores and falsely elevated predicted mortality rates. In contrast, apparently SAPS-II is still ok (Tempe et al, 2007).

End of life decisions involving pregnant women

• Treatment which would otherwise be futile is viewed differently if it is being administered to a critically ill pregnant patient, as if somehow the multiplication of wrongs makes a right. 
• If the foetus is given a life-ending diagnosis, the mothers will usually still prefer to carry it to term and then have perinatal palliative care (Wool, 2013)
• In the case of a mother diagnosed with brain death, maintaining the organ system function in order for the fetus to become more mature is possible - but will require extensive discussions with the family. In the words of Milliez et al (2001), "somatic support is justifed only to design appropriate obstetric strategies for the sake of the fetus". Examples of this abound; none are more extreme than the case presented by Bernstein et al (1989), where the body of a 30-year-old braindead woman was sustained for 107 days until a normal 1555g male infant was delivered by caesarian section at 32 weeks of gestation, with normal development thereafter.
• In the case where palliation is a reasonable option, there will be conflict between foetal vs. maternal best interest, as the legitimate value of the foetal life is weighed against the legitimate desire of the mother to have a peaceful death. The three options would be delivery of a premature foetus and then palliative care, or palliative care accepting the risk to the foetus, or no palliative care with a focus on making the gestation as normal as possible at the cost of the mother's comfort.