Why is the left lateral decubitus (LLD) position preferred over the right lateral decubitus position?

Left Lateral Decubitus Position in Clinical Practice: Benefits Over Right Lateral Position

The left lateral decubitus (LLD) position is preferred over the right lateral decubitus position primarily because it reduces compression of the inferior vena cava by the gravid uterus during pregnancy, optimizing venous return and cardiac output.

Anatomical and Physiological Basis

Pregnancy-Related Considerations

• The pregnant uterus can compress the inferior vena cava (IVC) when a woman lies in the supine position, reducing venous return and cardiac output 1
• Left lateral positioning attenuates the hemodynamic impact of uterine contractions 2
• Research shows that the 30° left-lateral tilt position most consistently reduces IVC compression compared to right-lateral tilt positions 3
• MRI studies demonstrate that supine positioning decreases IVC height and flow, while the left lateral position maintains better venous return 4

Hemodynamic Effects

• The 30° left-lateral tilt position achieves the greatest IVC volume in 70% of pregnant women, compared to only 23% in the 30° right-lateral tilt position 3
• Supine positioning in late pregnancy is associated with a 16.4% reduction in cardiac output compared to the left lateral position 5
• Blood flow through the IVC decreases at its origin by 85.3% and by 44.4% at the level of the renal veins when pregnant women lie supine 5

Clinical Applications

Surgical Procedures During Pregnancy

• For oncologic procedures during pregnancy, the left lateral tilt position is advised due to longer operating times and the use of general anesthesia 1
• Right lateral tilt can be used if it leads to improved surgical exposure 1
• Most procedures should be performed with the patient in a left pelvic tilt or left lateral position to avoid vascular compression during pregnancy 1

Endoscopic Procedures

• For pregnant women undergoing endoscopy, positioning patients on their backs should be avoided as the pregnant uterus can compress the aorta or inferior vena cava 1
• This compression can result in maternal hypotension and decreased placental perfusion 1

Resuscitation Scenarios

• During maternal cardiac arrest, left lateral tilt results in improved maternal hemodynamics including blood pressure, cardiac output, and stroke volume 1
• Left lateral positioning also improves fetal parameters of oxygenation and heart rate 1

Special Considerations and Exceptions

Cardiac Patients

• Interestingly, for non-pregnant patients with coronary artery disease, the right lateral decubitus position may lead to higher vagal modulation and lower sympathetic modulation 6
• This suggests that positioning preferences may differ based on the underlying condition and pregnancy status

Surgical Exposure

• In some surgical scenarios, right lateral tilt may be preferred if it provides better exposure of the surgical field 1
• The decision should balance hemodynamic considerations with surgical access requirements

Recovery Position

• For general first aid recovery positioning, there is little evidence suggesting superiority of left versus right lateral position for preventing aspiration 1
• One observational study showed no benefit to left versus right lateral position for aspiration prevention (RR, 0.82; 95% CI, 0.42–1.6) 1

Practical Implementation

• For pregnant patients, particularly in the third trimester:

  • Use left lateral tilt or full left lateral positioning when possible
  • If using a tilt, maximize the degree of tilt for optimal hemodynamic benefit
  • Consider using a fixed, hard wedge of a predetermined angle to maintain consistent positioning 1
  • Monitor maternal vital signs and fetal heart rate when appropriate

• For surgical procedures during pregnancy:

  • Position with left lateral tilt when possible
  • Use right lateral tilt only when necessary for surgical exposure
  • Maintain lower intra-abdominal pressure (10-13 mmHg) during laparoscopic procedures 1

Conclusion

The left lateral decubitus position is generally preferred over the right lateral position, particularly in pregnant women, due to its beneficial effects on hemodynamics by reducing inferior vena cava compression. This positioning optimizes venous return, cardiac output, and ultimately tissue perfusion, which is critical for both maternal and fetal well-being.