Special situations in surgery: surgical considerations in the pregnant woman

Summary

Pregnancy is responsible for many changes in women. With regards to surgery and surgical diagnoses these can be divided up into the following categories:

Anatomy

Physiology

Pharmacokinetics

Anaesthesia

Imaging

Social considerations

Anatomy

The gravid uterus is responsible for a shift in organs that are mobile and are usually sitting in the pelvis, e.g. small bowel, sigmoid colon, caecum and appendix. This leads to a different pattern of pain or symptomatology from pathology arising in such organs. A common example is the presentation of appendicitis which may present with diffuse right-sided pain or even right upper quadrant pain late in pregnancy. Tenderness/guarding is not usually over McBurney's point once the uterus is large enough for it not to be in the pelvis.

The gravid uterus later in pregnancy may compress the IVC, or even the aorta, when the patient is supine, and thereby reduce venous return and uterine blood flow, respectively. This can be avoided by positioning patients at an angle on the examination couch/operating table (e.g. with the use of a foam wedge).

Physiology

CARDIOVASCULAR

Increased: cardiac output, HR, stroke volume, blood volume, coagulable state

Decreased: colloid oncotic pressure (i.e. increased risk of pulmonary oedema), SBP and DBP, systemic vascular resistance.

RESPIRATORY

Respiratory alkalosis early in pregnancy with a compensated metabolic acidosis leads to less buffering capacity

Increased: oxygen consumption, minute ventilation, tidal volume

A large gravid uterus will also splint the diaphragm and lead to further potential respiratory compromise.