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While the effects of phenylephrine (PE) and ephedrine (E) on cerebral oxygen saturation (rS c O 2 ) already has been studied, the effect on paraspinal oxygen saturation (rS ps O 2 ) is still unexplored. This study aims to assess the effect of PE and E on rS c O 2 and rS ps O 2 , measured with near-infrared spectroscopy. A randomized 4-treatment cross-over trial was designed in 28 patients under BIS-titrated anaesthesia with sevoflurane. If MAP decreased more than 20% from baseline, incremental doses of PE and/or E were given according to the randomization (group I: E-PE-E, group II: PE-E-PE, group III: E-E-E, group IV: PE-PE-PE). rS c O 2 and rS ps O 2 on T 3 -T 4 , T 9 -T 10 and L 1 -L 2 were recorded. Differences in rSO 2 (post-pretreatment) within each group were analyzed with paired Student's t test. Differences in effects of PE and E on rS c O 2 and rS ps O 2 were analyzed with linear mixed-modelling. Following PE administration, rS c O 2 decreased significantly (- 2.7% ± 3.5), while it remained stable following E (- 0.6% ± 3.6). Contrastingly, rS ps O 2 at T 3 -T 4 , T 9 -T 10 and L 1 -L 2 slightly increased following PE (0.4% ± 2.5, 0.7% ± 2.0 and - 0.1% ± 1.4, respectively), while it decreased after E administration (- 1.3% ± 3.4%, - 0.7% ± 2.6% and - 1.3% ± 2.7%, respectively). Compared to E, PE administration was associated with a significant decrease in rS c O 2 (- 2.1%, 95% CI [- 3.1%, - 1.2%], p < 0.001). In contrast, compared to PE, E was associated with a significant decrease in rS ps O 2 at T 3 -T 4 , T 9 -T 10 and L 1 -L 2 (- 2.0%, 95% CI [- 2.8, - 1.1], p < 0.001; - 1.4%, 95% CI [- 2.4%, - 0.4%], p = 0.006; and - 1.5%, 95% CI [- 2.3%, - 0.8%], p < 0.001, respectively). An opposite effect on rS c O 2 and rS ps O 2 was observed after bolus administration of PE and E.

Background: Previous work has demonstrated paradoxical increases in cerebral oxygen saturation (ScO2) as blood pressure decreases and paradoxical decreases in ScO2 as blood pressure increases. It has been suggested that these paradoxical responses indicate a functional cerebral autoregulation mechanism. Accordingly, the authors hypothesized that if this suggestion is correct, paradoxical responses will occur exclusively in patients with intact cerebral autoregulation., Methods: Thirty-four patients undergoing elective cardiac surgery were included. Cerebral autoregulation was assessed with the near-infrared spectroscopy-derived cerebral oximetry index (COx), computed by calculating the Spearman correlation coefficient between mean arterial pressure and ScO2. COx less than 0.30 was previously defined as functional autoregulation. During cardiopulmonary bypass, 20% change in blood pressure was accomplished with the use of nitroprusside for decreasing pressure and phenylephrine for increasing pressure. Effects on COx were assessed. Data were analyzed using two-way ANOVA, Kruskal-Wallis test, and Wilcoxon and Mann-Whitney U test., Results: Sixty-five percent of patients had a baseline COx less than 0.30, indicating functional baseline autoregulation. In 50% of these patients (n = 10), COx became highly negative after vasoactive drug administration (from -0.04 [-0.25 to 0.16] to -0.63 [-0.83 to -0.26] after administration of phenylephrine, and from -0.05 [-0.19 to 0.17] to -0.55 [-0.94 to -0.35] after administration of nitroprusside). A negative COx implies a decrease in ScO2 with increase in pressure and, conversely, an increase in ScO2 with decrease in pressure., Conclusions: In this study, paradoxical changes in ScO2 after pharmacological-induced pressure changes occurred exclusively in patients with intact cerebral autoregulation, corroborating the hypothesis that these paradoxical responses might be attributable to a functional cerebral autoregulation.

Objective: To compare an arterial pressure-derived cardiac output (APCO) (Vigileo software version 1.07; Edwards Lifesciences, Irvine, CA) and a thermodilution cardiac output (CCO) as methods for measuring cardiac output under different pathologic and experimental conditions that induce changes in arterial waveform morphology. Design: A prospective study. Setting: A university hospital, single institutional. Participants: Fifty-two patients undergoing elective cardiac surgery. Interventions: Simultaneous APCO and CCO were compared in low-risk patients undergoing elective coronary artery surgery (without valvular disease) (control, n = 20), patients with aortic stenosis (AS, n = 10), aortic insufficiency (AI, n = 10), and intra-aortic balloon pump (IABP, n = 12). In the control group, additional data were registered before and after median sternotomy and phenylephrine administration. Measurements and Main Results: In the control group, Bland-Altman showed a bias of −3% (95% limits of agreement: −59% to +53%) before cardiopulmonary bypass (CPB) and of −1% (95% limits of agreement: −51% to +50%) after CPB. In the AS group, the bias was −5% (95% limits of agreement: −34% to +24%) before CPB and 1% (95% limits of agreement: −28 to +30%) after CPB. In the AI group bias was +32% (95% limits of agreement: −4% to +68%) before CPB and −2% (95% limits of agreement: −35% to +32%) after CPB. Median sternotomy decreased CCO by 10% ± 10%, whereas it increased APCO by 56% ± 28%. Phenylephrine administration decreased CCO by 11% ± 16%, whereas it increased APCO by 55% ± 34%. Conclusions: Cardiac output measurement based on uncalibrated pulse contour analysis is able to reflect cardiac output measured with the continuous thermodilution method in patients undergoing uncomplicated coronary artery surgery. However, in situations in which the arterial pressure waveform is changed, agreement between techniques may be altered and data obtained with uncalibrated pulse contour analysis may become less reliable. [Copyright &y& Elsevier]