Transfusion increased skin blood flow when initially low in volume-resuscitated patients without acute bleeding.

Background: Alterations in skin blood flow is a marker of inadequate tissue perfusion in critically ill patients after initial resuscitation. The effects of red blood cell transfusions (RBCT) on skin perfusion are not described in this setting. We evaluated the effects of red blood cell transfusions on skin tissue perfusion in critically ill patients without acute bleeding after initial resuscitation. Methods: A prospective observational study included 175 non-bleeding adult patients after fluid resuscitation requiring red blood cell transfusions. Using laser Doppler, we measured finger skin blood flow (SBF) at skin basal temperature (SBFBT), together with mean arterial pressure (MAP), heart rate (HR), hemoglobin (Hb), central venous pressure (CVP), lactate, and central or mixed venous oxygen saturation before and 1 h after RBCT. SBF responders were those with a 20% increase in SBFBT after RBCT. Results: Overall, SBFBT did not significantly change after RBCT [from 79.8 (4.3-479.4) to 83.4 (4.9-561.6); p = 0.67]. A relative increase equal to or more than 20% in SBFBT after RBCT (SBF responders) was observed in 77/175 of RBCT (44%). SBF responders had significantly lower SBFBT [41.3 (4.3-279.3) vs. 136.3 (6.5-479.4) perfusion units; p < 0.01], mixed or central venous oxygen saturation (62.5 ± 9.2 vs. 67.3% ± 12.0%; p < 0.01) and CVP (8.3 ± 5.1 vs. 10.3 ± 5.6 mmHg; p = 0.03) at baseline than non-responders. SBFBT increased in responders [from 41.3 (4.3-279.3) to 93.1 (9.8-561.6) perfusion units; p < 0.01], and decreased in the non-responders [from 136.3 (6.5-479.4) to 80.0 (4.9-540.8) perfusion units; p < 0.01] after RBCT. Pre-transfusion SBFBT was independently associated with a 20% increase in SBFBT after RBCT. Baseline SBFBT had an area under receiver operator characteristic of 0.73 (95% CI, 0.68-0.83) to predict SBFBT increase; A SBFBT of 73.0 perfusion units (PU) had a sensitivity of 71.4% and a specificity of 70.4% to predict SBFBT increase after RBCT. No significant differences in SBFBT were observed after RBCT in different subgroup analyses. Conclusion: The skin blood flow is globally unaltered by red blood cell transfusions in non-bleeding critically ill patients after initial resuscitation. However, a lower SBFBT at baseline was associated with a relative increase in skin tissue perfusion after RBCT.

Correlation between heart rate variability and cerebral autoregulation in septic patients.

BACKGROUND: Heart rate variability (HRV) may provide an estimation of the autonomous nervous system (ANS) integrity in critically ill patients. Disturbances of cerebral autoregulation (CAR) may share common pathways of ANS dysfunction. AIM: To explore whether changes in HRV and CAR index correlate in critically ill septic patients. METHODS: Prospectively collected data on septic adult (> 18 years) patients admitted into a mixed Intensive Care between February 2016 and August 2019 with a recorded transcranial doppler CAR assessment. CAR was assessed calculating the Pearson's correlation coefficient (i.e. mean flow index, Mxa) between the left middle cerebral artery flow velocity (FV), insonated with a 2-MHz probe, and invasive blood pressure (BP) signal, both recorded simultaneously through a Doppler Box (DWL, Germany). MATLAB software was used for CAR assessment using a validated script; a Mxa >0.3 was considered as impaired CAR. HRV was assessed during the same time period using a specific software (Kubios HRV 3.2.0) and analyzed in both time-domain and frequency domain methods. Correlation between HRV-derived variables and Mxa were assessed using the Spearman's coefficient. RESULTS: A total of 141 septic patients was studied; median Mxa was 0.35 [0.13-0.60], with 77 (54.6 %) patients having an impaired CAR. Mxa had a significant although weak correlation with HRV time domain (SDNN, r = 0.17, p = 0.04; RMSSD, r = 0.18, p = 0.03; NN50, r = 0.23, p = 0.006; pNN50, r = 0.23, p = 0.007), frequency domain (FFT-HF, r = 0.21; p = 0.01; AR-HF, r = 0.19; p = 0.02), and non-linear domain (SD1, r = 0.18, p = 0.03) parameters. Impaired CAR patients had also all of these HRV-derived parameters higher than those with intact CAR. CONCLUSIONS: In this exploratory study, a potential association of ANS dysfunction and impaired CAR during sepsis was observed.

Monitoring skin blood flow to rapidly identify alterations in tissue perfusion during fluid removal using continuous veno-venous hemofiltration in patients with circulatory shock.

BACKGROUND: Continuous veno-venous hemofiltration (CVVH) can be used to reduce fluid overload and tissue edema, but excessive fluid removal may impair tissue perfusion. Skin blood flow (SBF) alters rapidly in shock, so its measurement may be useful to help monitor tissue perfusion. METHODS: In a prospective, observational study in a 35-bed department of intensive care, all patients with shock who required fluid removal with CVVH were considered for inclusion. SBF was measured on the index finger using skin laser Doppler (Periflux 5000, Perimed, Järfälla, Sweden) for 3 min at baseline (before starting fluid removal, T0), and 1, 3 and 6 h after starting fluid removal. The same fluid removal rate was maintained throughout the study period. Patients were grouped according to absence (Group A) or presence (Group B) of altered tissue perfusion, defined as a 10% increase in blood lactate from T0 to T6 with the T6 lactate ≥ 1.5 mmol/l. Receiver operating characteristic curves were constructed and areas under the curve (AUROC) calculated to identify variables predictive of altered tissue perfusion. Data are reported as medians [25th-75th percentiles]. RESULTS: We studied 42 patients (31 septic shock, 11 cardiogenic shock); median SOFA score at inclusion was 9 [8-12]. At T0, there were no significant differences in hemodynamic variables, norepinephrine dose, lactate concentration, ScvO2 or ultrafiltration rate between groups A and B. Cardiac index and MAP did not change over time, but SBF decreased in both groups (p < 0.05) throughout the study period. The baseline SBF was lower (58[35-118] vs 119[57-178] perfusion units [PU], p = 0.03) and the decrease in SBF from T0 to T1 (ΔSBF%) higher (53[39-63] vs 21[12-24]%, p = 0.01) in group B than in group A. Baseline SBF and ΔSBF% predicted altered tissue perfusion with AUROCs of 0.83 and 0.96, respectively, with cut-offs for SBF of ≤ 57 PU (sensitivity 78%, specificity 87%) and ∆SBF% of ≥ 45% (sensitivity 92%, specificity 99%). CONCLUSION: Baseline SBF and its early reduction after initiation of fluid removal using CVVH can predict worsened tissue perfusion, reflected by an increase in blood lactate levels.

How have red blood transfusion practices changed in critically ill patients? A comparison of the ICON and ABC studies conducted 13 years apart.

BACKGROUND: Optimal transfusion practice remains a matter of ongoing debate despite several large clinical studies. STUDY DESIGN AND METHODS: Databases from two observational studies-the Anemia and Blood Transfusion in Critically ill patients (ABC) conducted in 1999 and The Intensive Care Over Nations (ICON) audit conducted in 2012-were compared to evaluate changes in transfusion practice and outcomes over a 13-year period. RESULTS: A total of 3534 patients from the ABC study and 4125 from the ICON study were included in this analysis. ICON patients were more severely ill, with higher APACHE II and sequential organ failure assessment (SOFA) scores on admission than ABC patients; however, ICU mortality rates were similar (13.5% vs 13.8%, P = .745). The ICU transfusion rate was significantly lower in the ICON study (24% vs 37%, P < .001). APACHE II and SOFA scores were significantly higher in transfused patients in the ICON study than those in the ABC study (APACHE II: 22.0 ± 8.1 vs 16.5 ± 7.9, P < .001; SOFA: 8.4 ± 4.0 vs 6.6 ± 3.7, P < .001), but mortality rates were similar. Twenty-eight day mortality rates for patients who received more than 4 RBC units were lower in the ICON study (33.6% vs 44.8%, P = .006). CONCLUSION: The transfusion rate in ICU patients decreased during the 13-year period, despite patients being more severely ill in the more recent study; ICU mortality rates remained relatively stable. In patients who received more than 4 units of blood, the mortality rate was significantly lower in the more recent database.