Mean arterial pressure as an indicator of fluid responsiveness in patients with septic shock

Abstract

To assess the value of mean arterial pressure (MAP) as an indicator for fluid responsiveness in patients with septic shock. A retrospective analysis of clinical data of 68 patients with septic shock receiving volume resuscitation in intensive care unit (ICU) of Drum-tower Hospital Affiliated to Medical School of Nanjing University from June 2011 to February 2012 was conducted. The changes in heart rate (HR), MAP, systolic arterial pressure (SBP), diastolic arterial pressure (DBP), pluse pressure (PP), central venous pressure (CVP) were recorded before and after volume resuscitations. Cardiac index (CI), intrathoracic blood volume index (ITBVI), systemic vessel resistance index (SVRI) and extravascular lung water index (EVLWI) were evaluated by using the thermodilution technique of pulse induced continuous cardiac output (PiCCO). All the patients were divided into two groups, responded group (ΔCI%≥10%) and the unresponded group (ΔCI%<10%), according to the change in CI (ΔCI%). Then the patients were divided into two subgroups, namely low MAP group(LMAP, MAP≤65 mm Hg) and high MAP group(HMAP, MAP>65 mm Hg), according to the initial value of MAP. Then compared the changes in hemodynamic variables before and after volume resuscitation in each subgroup and assess the correlation between the changes in MAP (ΔMAP%) and ΔCI%. Forty-four (64.7%) patients responded to the fluid challenge according to the predetermined criteria, SBP, DBP, MAP, PP, CI, CVP, ITBVI were increased significantly (SBP: 126.5±23.8 mm Hg vs. 110.7±20.2 mm Hg, DBP: 58.1±14.8 mm Hg vs. 52.8±13.5 mm Hg, MAP: 80.3±19.2 mm Hg vs. 70.1±15.8 mm Hg, PP: 68.2±18.7 mm Hg vs. 58.0±15.8 mm Hg, CI: 70.0±21.7 ml×s(-1)×m(-2) vs. 53.3±20.0 ml×s(-1)×m(-2), CVP: 13.0±4.5 mm Hg vs. 10.2±4.4 mm Hg, ITBVI: 909.1±248.7 ml/m(2) vs. 773.5±220.7 ml/m(2), all P<0.01), and SVRI was decreased significantly (130.9±47.7 kPa×s×L(-1)×m(-2) vs. 157.1±59.1 kPa×s×L(-1)×m(-2), P<0.01). HR and EVLWI did not change significantly. There was no significant correlation between ΔMAP% and ΔCI% in all the patients (r=0.266,P=0.054). In the sub-group of LMAP (n=39), ΔMAP% was positively correlated with ΔCI% (r=0.473, P=0.03), the under the receiver operating characteristic curve (ROC curve, AUC) was 0.763, 95% confidence interval (95%CI) 0.554 - 0.973, P=0.231. However, there was no significant correlation between the ΔMAP% and ΔCI% (r=-0.088, P=0.633) in the sub-group of HMAP (n=29). MAP can be used as an indicator of fluid responsiveness when the initial value of MAP was at a relative low level (MAP≤65 mm Hg) in patients with septic shock.