Mottling in Septic shock: Ethnicity and skin colour matter.

Abstract Background: Skin mottling as a clinical perfusion marker in septic shock is correlated well with severity and outcome in white skinned population and its validity as a clinical sign in dark skinned population is not known. Objectives of this study were to evaluate mottling in septic shock in the Indian ethnic population who has different skin colour as compared to white skinned population and compare mottling as an outcome predictor with Capillary Refill Time(CRT) and other biochemical parameters which are the established clinical markers of perfusion in septic shock. Methods: We conducted a prospective observational study of patients with skin colour category 21 to 34 on von Luschan scale or Fitzpatrick type IV and V who had septic shock needing high dose of norepinephrine ≥ 0.2 mcg/kg/min after fluid optimisation. The study was conducted in a mixed medical - surgical ICU over a period of 12 months. Two blinded experts (Dermatologist and a Cosmetic surgeon) independently classified the skin type, validated the occurrence of mottling and scored mottling in our patients. We recorded the demographics, hemodynamic variables, mottling score and observed for the incidence of mottling and its correlation with predictors of severity of septic shock. We also compared CRT, Arterial lactate, central venous oxygen saturation and venoarterial PCO2 gap with mottling as predictor of outcome in septic shock patients. Results: We included 108 patients with age 61±16 years. Mean SOFA and APACHE II scores at enrolment were 10.3 and 21.9 respectively. Incidence of mottling was 20.3 % (22/ 108). CRT > 3 seconds was observed in 50.9% (55/108) Development of mottling significantly correlated with mortality; 20/22(90.9%) patients died in mottling group versus 58/86(65.1%) in non-mottling group ( p =0.028). Independent t test of mottling score vs death showed that higher the mottling score, ( score> 3) (p= 0.008) more the certainty of death . (p= 0.008. CRT > 3 seconds did not corelate with mortality; 40/55(72.7%) patients with CRT > 3 seconds died versus 32/53(74.4%) patients died in CRT≤ 3seconds group. Occurrence of mottling could independently predict mortality ; Positive predictive value of 90.9 % which was comparable to positive predictive value of lactate levels > 4mmol/lit, i.e. 94.1% . CRT > 3 seconds did not corelate with mortality; positive predictive value was 72.7 % Conclusion: Incidence of mottling in septic shock is much less in patients of Indian ethnicity with brown skin colour as compared to that in White skinned population. Occurrence of mottling and not ­­­delayed CRT, is a better predictor of outcome in this setting.