Misconceptions About the Starling Principle as Applied to Fluid Therapy

Abstract

To the EditorThe recent publication by Löffel et al 1 concerning the Starling principle reveals some important misunderstandings common among clinicians about the science. The authors confuse the Frank Starling Law (of the heart) with Starling's principle of fluid exchange, often expressed as the Starling equation which I explain here.

In Response

“…We propose that, in addition to the "visual inspection" of myocardial function and size of the inferior vena cava (IVC), echocardiographic assessment can specifically identify dynamic parameters, such as maximal aortic blood flow velocity, velocity time integral (VTI), IVC collapsibility index, and stroke volume variability, that are known to reliably predict fluid responsiveness in septic patients. They offer a significant advantage over static macrocirculatory parameters, that is, arterial pressure, central venous pressure, pulmonary artery occlusion pressure, and CO. 2 However, in addition to the need for specialist training, numerous patient-related and logistical concerns stand in the way of a widespread implementation of serial echo assessments. this proposal from Woodcock and Woodcock's 3 2012 review about the Revised Starling Principle, where the abstract reads: "The oncotic pressure difference across the endothelial glycocalyx layer opposes, but does not reverse, the filtration rate (the 'no absorption' rule)."…”

“…Woodcock criticizes us for making the "false" claim that interstitial fluid cannot be recruited by raising the plasma oncotic pressure. 2 We have taken…”

“…Woodcock criticizes us for making the “false” claim that interstitial fluid cannot be recruited by raising the plasma oncotic pressure. 2 We have taken this proposal from Woodcock and Woodcock’s 3 2012 review about the Revised Starling Principle, where the abstract reads: “The oncotic pressure difference across the endothelial glycocalyx layer opposes, but does not reverse, the filtration rate (the ‘no absorption’ rule).” In the subsequent text, Woodcock elaborates on the futility of trying to raise the plasma volume by hyperoncotic albumin because the “no absorption rule” holds that recruitment of interstitial fluid cannot occur in this way. Our current finding that 20% albumin expands the plasma volume by twice the infused volume 1 might challenge the “no absorption rule” but we purposely avoided to discuss whether recruitment occurs across the capillary wall or via the lymph.…”