RESUMO
OBJECTIVE: To explore the correlation of tip perfusion index (TPI) with the hemodynamics and catecholamines and to assess the value and meaning of TPI for monitoring stress responses in general anesthesia. METHODS: Twenty patients who were to receive selective neurosurgery underwent induction and maintenance of propofol and remifentanil by target controlled infusion (TCI). A 60 mA-50 Hz-5 s electrostimulus was applied before tracheal intubation and head holder setting respectively. TPI, SBP, diastolic blood pressure (DBP), heart rate (HR), and bispectral index (BIS) were recorded at nine time points: before induction (baseline), before and after electrostimulation, before and after tracheal intubation, before and after electrostimulation, and before and after head holder setting. The changes of parameters (DeltaTPI, DeltaSBP, DeltaDBP, DeltaHR, and DeltaBIS) were calculated after each stimulation. Five out of 20 patients were selected randomly to monitor the plasma concentration of catecholamine at the above time points. The responses to tracheal intubation and head holder setting were defined as the SBP increasing > 15 mm Hg over the baseline value. RESULTS: DeltaTPI was significantly correlated with DeltaSBP and DeltaDBP (r = 0.623 and 0.317, P <0.01 and 0.05). The responses to tracheal intubation and head holder setting were inhibited effectively when the DeltaTPI caused by electrostimulus was less than 10% of the pre-electrostimulus TPI. TPI was significantly negatively correlated with the plasma concentrations of norepinephrine and epinephrine (r = -0.679, and r = -0.364, P < 0.05 and 0.01). CONCLUSION: (1) The TPI change is correlated well with the blood pressure change during stresses, and the TPI change caused by electrostimulus can predict the blood pressure change caused by tracheal intubation and head holder setting. (2) The TPI change reflects the norepinephrine plasma level indirectly.