Peripheral perfusion index predicting prolonged ICU stay earlier and better than lactate in surgical patients: an observational study

BACKGROUND: Peripheral perfusion index (PPI) is an indicator reflecting perfusion. Patients undergoing long time surgeries are more prone to hypoperfusion and increased lactate. Few studies focusing on investigating the association between PPI and surgical patients’ prognoses. We performed this study to find it out. METHODS: From January 2019 to September 2019, we retrospected all surgical patients who were transferred to ICU, Xinyang Central hospital, Henan province, China. Inclusive criteria: age ≥ 18 years old; surgical length ≥ 120 min. Exclusive criteria: died in ICU; discharging against medical advice; existing diseases affecting blood flow of upper limbs, for example, vascular thrombus in arms; severe liver dysfunction. We defined “prolonged ICU stay” as patients with their length of ICU stay longer than 48 h. According to the definition, patients were divided into two groups: “prolonged group” (PG) and “non-prolong group” (nPG). Baseline characteristics, surgical and therapeutic information, ICU LOS, SOFA and APACHE II were collected. Besides we gathered data of following parameters at 3 time points (T0: ICU admission; T1: 6 h after admission; T2: 12 h after admission): mean artery pressure (MAP), lactate, heart rate (HR), PPI and body temperature. Data were compared between the 2 groups. Multivariable binary logistic regression and ROC (receiver operating characteristic) curves were performed to find the association between perfusion indictors and ICU LOS. RESULTS: Eventually, 168 patients were included, 65 in PG and 103 in nPG. Compared to nPG, patients in PG had higher blood lactate and lower PPI. PPI showed significant difference between two groups earlier than lactate (T(0) vs T(1)). The value of PPI at two time points was lower in PG than nPG(T0: 1.09 ± 0.33 vs 1.41 ± 0.45, p = 0.001; T1: 1.08 ± 0.37 vs 1.49 ± 0.41, p < 0.001). Increased lactate(T1)(OR 3.216; 95% CI 1.253–8.254, P = 0.015) and decreased PPI(T1) (OR 0.070; 95% CI 0.016–0.307, P < 0.001) were independently associated with prolonged ICU stay. The area under ROC of the PPI(T1) for predicting ICU stay> 48 h was 0.772, and the cutoff value for PPI(T1) was 1.35, with 83.3% sensitivity and 73.8% specificity. CONCLUSIONS: PPI and blood lactate at T(1)(6 h after ICU admission) are associated with ICU LOS in surgical patient. Compared to lactate, PPI indicates hypoperfusion earlier and more accurate in predicting prolonged ICU stay.