Question 16

College Answer

a.       Indicate  how  the  following  variables  change  in  the  third  trimester  (either increase or decrease or no change).

Variable	Direction of Change
Systolic Blood Pressure	Decrease
Diastolic Blood Pressure	Decrease
Heart Rate	Increase
Blood Volume	Increase
Haematocrit	Mild decrease
Tidal Volume	Increase
pH	No change
PCO2	Decrease
PO2	Increase
Bicarbonate	Decrease

b.  List  4 conditions  specific  to pregnancy  which  may result  in right  or left heart failure or both.

•  Peripartum cardiomyopathy
•  Amniotic fluid embolism
•   Pre-eclampsia 
•  Tocolytic pulmonary oedema
•  Pulmonary thromboembolism

c.   Outline the major differences in approach to cardiopulmonary  resuscitation in pregnancy as compared to the non-pregnant adult.

•    CPR in left lateral position (27 degree tilt)
•    Consideration for emergency caesarian section
•    Hands slightly higher on sternum for chest compressions
•    Additional personnel / equipment for emergency c-section and neonatal resuscitation

Discussion

This entire question draws heavily from Oh's Intensive Care manual: Chapter 64   (pp. 684) General  obstetric  emergencies by Winnie  TP  Wan  and  Tony  Gin,

Question a) specifically refers to Table 64.1 on page 685. A summary of the normal physiological changes in pregnancy can be found elsewhere.

In summary:

a)

Question a) specifically refers to Table 64.1 on page 685. A summary of the normal physiological changes in pregnancy can be found elsewhere.

b) is perfect as a list. Amniotic fluid embolism actually causes right heart failure at first, and then turns into LV failure. In fact, it would be even more perfect as a table:

This works best as a table. In fact, in Sliwa et al (2010) there is an even better table (Table 3. p.772)

Left-dominant	Right-dominant
Pre-eclampsia Eclampsia Tocolytic therapy Peripartum cardiomyopathy Pituitary apoplexy (Sheehan's syndrome) Worsening of pre-existing rheumatic MR Pre-existing idiopathic dilated cardiomyopathy (IDC) unmasked by pregnancy	Massive PE Aminotic fluid embolism Worsening of pre-existing rheumatic TR
Potentially bi-ventricular: Pre-existing unrecognized congenital heart disease Pregnancy-associated myocardial infarction

c) is well discussed in the chapter on cardiac arrest in the pregnant patient. In short:

Keep in mind the following alternative causes of arrest:

• Amniotic fluid embolism
• Hypertensive disorder of pregnancy (with ensuing cardiac failure)
• Seizures (with ensuing hypoxia and arrest)
• Haemorrhage from liver rupture
• Haemorrhage from uterine rupture

Issues which complicate the pregnant arrest and peri-arrest scenario:

• Difficult intubation
• Increased risk of aspiration (the stomach just doent't empty)
• Venous return is impaired by the gravid uterus
• Systemic oxygen consumption is increased
• Cardiac output and circulating volume are greater; decompensation occurs later.

Manually displace the uterus to the left (off the aorta and vena cava)

• Manually displace the uterus to the left (off the aorta and vena cava)
• Add a left lateral tilt (the ideal angle is unknown, and is thought to be between 15° and 30°)
• Biaxillary defibrillator pad placement
• Prepare for an emergency perimortem caesarian.

b) is perfect as a list. Amniotic fluid embolism actually causes right heart failure at first, and then turns into LV failure

To (c) I might add that the emergency caesarian should be considered after 4 minutes of CPR, as per the ILCOR guidelines. The weirdly specific 27° pelvis tilt mentioned by the college can get you reaching for a protractor. It probably comes from the old AHA guidelines (these days the guideline-makers for the ECC and AHA no longer recommend the left lateral tilt (see the 2015 AHA update and the 2015 ECC guidelines).A left lateral tilt may compromise effective CPR, but is still recommended by the ARC Guideline 11.10  (2011) "Special Circumstances". Presumably, once the ARC get around to it, their guidelines will fall in line with international consensus. The 27° figure comes from Rees and Willis (1998), who got physicians to perform CPR on specially modified mannequins at different degrees of tilt. The authors found that the 27 degrees was the angle at which safe positioning and compression efficacy were at optimal compromise. Chest compression force was not too badly affected (80% of the force of compressions with the patient in a supine position), and the patient was unlikely to roll off the bed at this angle.

Oh's Intensive Care manual: Chapter 64   (pp. 684) General  obstetric  emergencies by Winnie  TP  Wan  and  Tony  Gin

ARC Guideline 11.10  (2011) "Special Circumstances". 

the 2015 AHA update:

2015 ECC guidelines:

Rees, G. A. D., and B. A. Willis. "Resuscitation in late pregnancy."Anaesthesia 43.5 (1988): 347-349.