Pulse Pressure Respiratory Variation as an Early Marker of Cardiac Output Fall in Experimental Hemorrhagic Shock

Abstract

Pulse pressure (DeltaPp) and systolic pressure (DeltaPs) variations have been recommended as predictors of fluid responsiveness in critically ill patients. We hypothesized that changes in DeltaPp and DeltaPs parallel alterations in stroke volume (SV) and cardiac output (CO) during hemorrhage, shock, and resuscitation. In anesthetized and mechanically ventilated mongrel dogs, a graded hemorrhage (20 mL/min) was induced to a target mean arterial pressure (MAP) of 40 mm Hg, which was maintained for additional 30 min. Total shed-blood volume was then retransfused at a 40 mL/min rate. CO, SV, right atrial pressure (RAP), pulmonary artery occlusion pressure (PAOP), and continuous mixed venous oxygen saturation (SvO(2)) were assessed. Both DeltaPp and DeltaPs were calculated from direct arterial pressure waveform. Removal of about 9% of estimated blood volume promoted a reduction in SV (14.8 +/- 2.2 to 10.6 +/- 1.3 mL, P < 0.05). At approximately 18% blood volume removal, significant changes in CO (2.4 +/- 0.2 to 1.5 +/- 0.2 mL/min, P < 0.05), DeltaPp (12.6 +/- 1.4 to 15.8 +/- 2.0%, P < 0.05), and SvO(2) (82 +/- 1.4 to 73 +/- 1.7%, P < 0.05) were observed. Alterations in MAP, RAP, PAOP, and DeltaPs could be detected only after each animal had lost over 36% of estimated initial blood volume. There was correlation between blood volume loss and SV, CO, and SvO(2), as well as between blood loss and MAP, DeltaPp, and DeltaPs. Blood volume loss showed no correlation with cardiac filling pressures. DeltaPp is a useful, early marker of SV and CO for the assessment of cardiac preload changes in hemorrhagic shock, while cardiac filling pressures are not.

Intraoperative fluid management in open gastrointestinal surgery: goal-directed versus restrictive

“…Lahner et al (20) demonstrated that SVV may not be a reliable predictor of fluid responsiveness in the setting of major abdominal surgery. PPV is considered to be more reliable than SVV and can be used to recognize volume contraction earlier than other indicators (21,22); however, amplified PPV does not represent the hypovolemic status, such as anesthesia or inflammation-induced vasodilation (10). Therefore, restrictive fluid infusion with vasopressor administration during abdominal surgery has been advocated to prevent fluid retention after the anesthetic effects have subsided.…”

Artificial Organs 2007: A Year in Review

“…Glauco Westphal et al. (17) of the University of São Paulo (São Paulo, Brazil) evaluated if changes in pulse pressure (DeltaPp) and systolic pressure (DeltaPs) parallel alterations in stroke volume (SV) and CO during hemorrhage, shock, and resuscitation. In anesthetized and mechanically ventilated mongrel dogs, a graded hemorrhage (20 mL/min) was induced to a target mean arterial pressure (MAP) of 40 mm Hg, maintained for an additional 30 min.…”

Vasodilation increases pulse pressure variation, mimicking hypovolemic status in rabbits

“…The former method is also more reliable than other dynamic parameters, such as systolic pressure respiratory variation (SPV) or stroke volume respiratory variation (SVV), and it can recognize volume contraction earlier than the others 9,10,13. Hence, PPV has become largely recommended to guide volume expansion in patients with hemodynamic instability 9–12…”

“…Patients with low PPV are insensitive to cyclic changes in preload induced by mechanical ventilation, and they operate on the flat portion of the Frank-Starling curve (non-responders). On the other hand, when PPV is high, patients are operating on the steep portion of the Frank-Starling curve and can respond with an increase in SV after fluid infusion (responders) 9,13,15,16…”