Intensive Care Medicine

, Volume 22, Issue 7, pp 651–655

Effects of extreme lateral posture on hemodynamics and plasma atrial natriuretic peptide levels in critically ill patients

  • Th. Bein
  • Ch. Metz
  • C. Keyl
  • M. Pfeifer
  • K. Taeger
Original

DOI: 10.1007/BF01709741

Cite this article as:
Bein, T., Metz, C., Keyl, C. et al. Intensive Care Med (1996) 22: 651. doi:10.1007/BF01709741

Abstract

Objective

To quantify the hemodynamic effects of turning critically ill, mechanically ventilated patients to the extreme left and right lateral postures.

Design

Prospective investigation.

Setting

Eight-bed intensive care unit in a university hospital.

Patients

Twelve consecutive patients presenting with severe respiratory failure and requiring continuous positive inotropic support.

Interventions

All patients were mechanically ventilated and placed in a kinetic treatment system. They were positioned in the supine, left dependent, and right dependent postures, resting for 15 min in each position.

Measurements and results

Hemodynamic measurements, assessments of right ventricular function, and determinations of intrathoracic blood volume were performed in three different positions. Concentrations of atrial natriuretic peptide in plasma were quantified. In three patients, the findings were controlled by transesophageal echocardiography.

Cardiac index [median (range) 5.5 (3.2–8.1) vs 4.3 (3.2–7.5) l/min per m2,p<0.01], intrathoracic blood volume [1125 (820–1394) vs 1037 (821–1267) ml/m2,p<0.01], and right ventricular end-diastolic volume [130 (83–159) vs 114 (79–155) ml/m2,p<0.05] increased significantly in the left dependent position compared to supine. Mean arterial pressure did not change. Atrial natriuretic peptide levels rose from 140 to 203 pg/ml. In the right dependent position, we found a marked decrease in the mean arterial pressure [85 mmHg (supine) to 72 mmHg (right dependent),p<0.01]. Cardiac index and intrathoracic blood volume were unchanged, but right ventricular enddiastolic volume decreased from 114 to 102 ml/m2 (p<0.05) Additionally, atrial natriuretic peptide levels decreased significantly (median Δ value: 37 pg/ml). In echocardiographic controls we found an increase in right ventricular end-diastolic diameters in the left dependent position and shortened diameters in the right dependent position.

Conclusions

Extreme lateral posture affects the cardiovascular system in critically ill, mechanically ventilated patients: in the left dependent position a “hyperdynamic state” is reinforced, while the right decubitus position impairs right ventricular preload and predisposes to hypotension. Echocardiography and changes in plasma atrial natriuretic peptide values indicate that these findings are due to altered distensibility of the right ventricle caused by regional intrathoracic gravitational changes. We conclude that the duration and the angle of lateral posture should be restricted in hemodynamically unstable patients.

Key Words

Lateral posture Hemodynamic effects Kinetic therapy Respiratory failure Kight ventricular function Atrial natriuretic peptide 

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Copyright information

© Springer-Verlag 1996

Authors and Affiliations

  • Th. Bein
    • 1
  • Ch. Metz
    • 1
  • C. Keyl
    • 1
  • M. Pfeifer
    • 2
  • K. Taeger
    • 1
  1. 1.Department of Anesthesia University HospitalUniversity of RegensburgRegensburgGermany
  2. 2.Department of Internal Medicine II, University HospitalUniversity of RegensburgRegensburgGermany

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