Transcranial doppler assessment of cerebral perfusion in critically ill septic patients: a pilot study

BACKGROUND The aim of this study is to evaluate the feasibility and efficacy of Transcranial Doppler (TCD) in assessing cerebral perfusion changes in septic patients. METHODS Using TCD, we measured the mean velocity in the middle cerebral artery (VmMCA, cm/sec) and calculated the pulsatility index (PI), resistance index (RI) and cerebral blood flow index (CBFi = 10*MAP/1.47(PI)) on the first day of patients' admission or on the first day of sepsis development; measurements were repeated on the second day. Sepsis was defined according to standard criteria. RESULTS Forty-one patients without any known neurologic deficit treated in our 24-bed Critical Care Unit were assessed (Sepsis Group = 20, Control Group = 21). Examination was feasible in 91% of septic and 85% of non-septic patients (p = 0.89). No difference was found between the two groups in mean age, mean arterial pressure (MAP) or APACHE II score. The pCO2 values were higher in septic patients (46 ± 12 vs. 39 ± 4 mmHg p < 0.01). No statistically significant higher values of VmMCA were found in septic patients (110 ± 34 cm/sec vs. 99 ± 28 cm/sec p = 0.17). Higher values of PI and RI were found in septic patients (1.15 ± 0.25 vs. 0.98 ± 0.16 p < 0.01, 0.64 ± 0.08 vs. 0.59 ± 0.06 p < 0.01, respectively). No statistically significant lower values of CBFi were found in septic patients (497 ± 116 vs. 548 ± 110 p = 0.06). CONCLUSIONS Our results suggest cerebral vasoconstriction in septic compared to non-septic patients. TCD is an efficient and feasible exam to evaluate changes in cerebral perfusion during sepsis.