Effects of Dobutamine on Microcirculation, Regional and Peripheral Perfusion in Septic Shock Patients

• Change in the perfused vascular density [ Time Frame: 2.5 h ] [ Designated as safety issue: No ]
  Perfused vessel density is a measure of sublingual microcirculation. It will be assessed with SDF videomicroscopy (Microscan ® for NTSC, Microvision Medical, Amsterdam, NL). (Crit Care 2007; 11:R101).
  
  

• Macrohemodynamics [ Time Frame: 2.5 h ] [ Designated as safety issue: No ]
  Macrohemodynamic values: mean arterial pressure, heart rate, and pulmonary artery catheter derived values (pulmonary artery occlusion pressure, cardiac index, systemic vascular resistance index)
  
  
• Transthoracic echocardiography [ Time Frame: 2.5 h ] [ Designated as safety issue: No ]
  1. Morphology and diameters of cardiac cavities
  2. Left ventricular systolic function
  3. Right ventricular systolic function
  4. left ventricular diastolic function
  
  
• Gastric mucosal perfusion [ Time Frame: 2.5 h ] [ Designated as safety issue: No ]
  Gastric mucosal perfusion: gastric air tonometry will be used to measure intraluminal pCO2 and calculate gastric - arterial pCO2 gradient (Tonocap, Datex)
  
  
• Hepatosplanchnic blood flow [ Time Frame: 2.5 h ] [ Designated as safety issue: No ]
  This will be assessed by the ICG-PDR method. Each patient will receive an ICG finger clip which will be connected to a liver function monitor (LiMon Pulsion Medical Systems, Germany).
  
  
• Peripheral perfusion [ Time Frame: 2.5 h ] [ Designated as safety issue: No ]
  1. Peripheral flow index (PFI), derived from the pulse oxymetry signal (MP20 IntelliVue monitor, Philips Medical systems, Amsterdam,NL)
  2. Temperatures at the blood (by PAC), and at different places in the skin. We will calculate central to toe gradient (Tc-toe), and forearm to fingertip skin temperature gradient (Tskin-diff)
  3. NIRS: Tissue oxygen saturation (StO2) will be measured by a tissue spectrometer (InSpectra Model 325, Hutchinson Technology, Hutchinson, Minn.)
  
  
• Metabolic perfusion assessment [ Time Frame: 2.5 h ] [ Designated as safety issue: No ]
  We will measure mixed venous O2 saturation and arterial lactate
  
  

The investigators hypothesize that dobutamine is able to revert negative redistribution of flow by inducing a selective vasodilatory effect on hypoperfused territories, particularly at the sublingual and gastric mucosa, and at the peripheral tissues. Therefore, dobutamine improves microcirculatory alterations and regional perfusion in septic shock, independent of its effects on cardiac output.

The relevance of this concept is that it would support a more rational use of dobutamine in septic shock patients, not only as an inotrope to increase cardiac output, but more important, as a selective vasodilator aimed at restoring perfusion.

Therefore, the investigators designed a randomized, cross-over, placebo-controlled study looking at the acute physiologic effects of 5 mcg/kg/min fixed-dose of dobutamine on cardiac function, microcirculation, gastric mucosal, hepatosplanchnic, and peripheral perfusion in septic shock patients.