Effect of dobutamine on renal resistive index in septic shock patients

Introduction:

Septic shock is defined as “subset of sepsis with circulatory and cellular/metabolic dysfunction associated with higher risk of mortality.†After appropriate resuscitation if MAP does not improve to about 65 mm Hg it is recommended that vasopressors be initiated. Norepinephrine is recommended as the initial vasopressor as per Surviving Sepsis campaign recommendations. It is recommended to use second vasopressor to reduce the dose of first considering side effects of high dose of norepinephrine. Second choice is always so far based on clinical judgement and arbitrary between epinephrine, vasopressin and dobutamine. However none of the above vasopressors were proven to be strongly beneficial after Nor-Epinephrine and no definitive strong recommendations were made regarding the second choice of vasopressor. Renal Resistive Index (RRI) is a sonographic measurement of resistance to flow in intrarenal arcuate or interlobar arteries. An inverse relationship between MAP and RRI has been strongly demonstrated. Owing to thelacunae in the second choice vasopressor, this study aims at using Doppler RRIas a surrogate marker and early index of hypoperfusion and assist the choice ofvasopressor in septic shock. The secondary aim is to assess the relationship ofRRI to AKI and lactate in septic shock.

 Aim of Study:

Primary objective:

To evaluatethe effect of dobutamine on Renal Resistive Index in patients with septic shock.

Secondary objective:

1. To assessthe relationship of RRI with lactate in septic shock.

2. To assessthe relationship of RRI with AKI in septic shock.

Study Protocol: All patients of septic shock in ICUincluded in the study will be resuscitated according to SSC guidelines.Patients with septic shock will initially be resuscitated with crystalloids tomaintain a MAP ≥65 mm Hg. The adequacy of fluidresuscitation is monitored by CVP (8-12 mm Hg), PPV (<13%) and PLR test. Following adequate resuscitation, if the MAP still remains less than 65 mm Hgthen nor- epinephrine will be used as the first line vasopressor.Nor-epinephrineinfusion will be started at a dose of 0.05μg/kg/min and gradually increased to0.2μg/kg/min.  Once the meanarterial pressure (MAP) is >65 mm Hg will be started on dobutamine at a doseof 3μg/kg/min.In case if MAP falls below 65 mm Hg despite theabove ionotropic support, vasopressin will be added as rescue drug in a doseupto 0.03U/min.

The responseto vasopressors / ionotropes and resuscitation will be monitored by vitalparameters such as heart rate, MAP, CVP, ejection fraction (EF), ScvO2 andurine output. Lactate and RRI will be measured at admission, 1-hr, 6-hrs,12-hrs, 24-hr and 48-hrs following start of ionotropes. S.Creatinine ismeasured every day for 72 hours. SOFA score will be measured everyday.

Clinical Significance: This will guide the effect of dubutamine in septic shock patients by using RRI as a monitoring tool for organ perfusion.

Keywords: Septic shock, Renal Resistive Index, Dobutamine