Effect of phenylephrine on cerebral oxygen saturation and cardiac output in adults when used to treat intraoperative hypotension: a systematic review

Noninvasive assessment of human microvascular function in health and disease using incident dark-field microscopy

Reduced peripheral microvascular reactivity is associated with an increased risk for major adverse cardiac events (MACEs). Tools for noninvasive assessment of peripheral microvascular function are limited, and existing technology is poorly validated in both healthy populations and patients with cardiovascular disease (CVD). Here, we used a handheld incident dark-field imaging tool (CytoCam) to test the hypothesis that, compared with healthy individuals (no risk factors for CVD), subjects formally diagnosed with coronary artery disease (CAD) or those with ≥2 risk factors for CAD (at risk) would exhibit impaired peripheral microvascular reactivity. A total of 17 participants (11 healthy, 6 at risk) were included in this pilot study. CytoCam was used to measure sublingual microvascular total vessel density (TVD), perfused vessel density (PVD), and microvascular flow index (MFI) in response to the topical application of acetylcholine (ACh) and sublingual administration of nitroglycerin (NTG). Baseline MFI and PVD were significantly reduced in the at-risk cohort compared with healthy individuals. Surprisingly, following the application of acetylcholine and nitroglycerin, both groups showed a significant improvement in all three microvascular perfusion parameters. These results suggest that, despite baseline reductions in both microvascular density and perfusion, human in vivo peripheral microvascular reactivity to both endothelial-dependent and -independent vasoactive agents remains intact in individuals with CAD or multiple risk factors for disease.NEW & NOTEWORTHY To our knowledge, this is the first study to comprehensively characterize in vivo sublingual microvascular structure and function (endothelium-dependent and -independent) in healthy patients and those with CVD. Importantly, we used an easy-to-use handheld device that can be easily translated to clinical settings. Our results indicate that baseline microvascular impairments in structure and function can be detected using the CytoCam technology, although reactivity to acetylcholine may be maintained even during disease in the peripheral microcirculation.

Effects of phenylephrine on systemic and cerebral circulations in humans: a systematic review with mechanistic explanations

We conducted a systematic review of the literature reporting phenylephrine-induced changes in blood pressure, cardiac output, cerebral blood flow and cerebral tissue oxygen saturation as measured by near-infrared spectroscopy in humans. We used the proportion change of the group mean values reported by the original studies in our analysis. Phenylephrine elevates blood pressure whilst concurrently inducing a reduction in cardiac output. Furthermore, despite increasing cerebral blood flow, it decreases cerebral tissue oxygen saturation. The extent of phenylephrine's influence on cardiac output (r = -0.54 and p = 0.09 in awake humans; r = -0.55 and p = 0.007 in anaesthetised humans), cerebral blood flow (r = 0.65 and p = 0.002 in awake humans; r = 0.80 and p = 0.003 in anaesthetised humans) and cerebral tissue oxygen saturation (r = -0.72 and p = 0.03 in awake humans; r = -0.24 and p = 0.48 in anaesthetised humans) appears closely linked to the magnitude of phenylephrine-induced blood pressure changes. When comparing the effects of phenylephrine in awake and anaesthetised humans, we found no evidence of a significant difference in cardiac output, cerebral blood flow or cerebral tissue oxygen saturation. There was also no evidence of a significant difference in effect on systemic and cerebral circulations whether phenylephrine was given by bolus or infusion. We explore the underlying mechanisms driving the phenylephrine-induced cardiac output reduction, cerebral blood flow increase and cerebral tissue oxygen saturation decrease. Individualised treatment approaches, close monitoring and consideration of potential risks and benefits remain vital to the safe and effective use of phenylephrine in acute care.

Effects of ephedrine and phenylephrine on cerebral oxygenation: observational prospective study using near-infrared time-resolved spectroscopy

It has been reported that cerebral oxygenation (ScO2) measured by near infrared spectroscopy is maintained or increased by treatment with ephedrine, whereas almost all previous reports demonstrated that phenylephrine reduced ScO2. As the mechanism of the latter, the interference of the extracranial blood flow, that is extracranial contamination, has been suspected. Accordingly, in this prospective observational study, we utilized time-resolved spectroscopy (TRS), in which the effect of extracranial contamination is thought to be minimal, and evaluated whether the same result was obtained. We measured the changes in ScO2 as well as the total cerebral hemoglobin concentration (tHb) after treatment with ephedrine or phenylephrine during laparoscopic surgery by using a tNIRS-1 (Hamamatsu Photonics, Hamamatsu, Japan), which is a commercial instrument utilizing TRS. Based on a mixed-effects model with random intercepts for ScO2 or tHb including mean blood pressure, the mean difference and 95% confidence interval were evaluated as well as the predicted mean difference and its confidence interval using the interquartile range of mean blood pressure. Fifty treatments with ephedrine or phenylephrine were done. The mean differences of ScO2 were less than 0.1% and the predicted mean differences were less than 1.1% for the two drugs. The mean differences of tHb were less than 0.02 μM and the predicted mean differences were less than 0.2 μM for the drugs. The changes in ScO2 and tHb after treatments with ephedrine and phenylephrine were very small and clinically insignificant when measured by TRS. Previous reports about phenylephrine may have been affected by extracranial contamination.

Norepinephrine combined with phenylephrine versus norepinephrine in patients with septic shock: a retrospective cohort study

BACKGROUND

Phenylephrine (PE) and norepinephrine (NE) may be used to maintain adequate blood pressure and tissue perfusion in patients with septic shock, but the effect of NE combined with PE (NE-PE) on mortality remains unclear. We hypothesized that NE-PE would not inferior to NE alone for all-cause hospital mortality in patients with septic shock.

METHODS

This single-center, retrospective cohort study included adult patients with septic shock. According to the infusion type, patients were divided into the NE-PE or NE group. Multivariate logistic regression, propensity score matching and doubly robust estimation were used to analyze the differences between groups. The primary outcome was the all-cause hospital mortality rate after NE-PE or NE infusion.

RESULTS

Among 1, 747 included patients, 1, 055 received NE and 692 received NE-PE. For the primary outcome, the hospital mortality rate was higher in patients who received NE-PE than in those who received NE (49.7% vs. 34.5%, p < 0.001), and NE-PE was independently associated with higher hospital mortality (odds ratio = 1.76, 95% confidence interval = 1.36-2.28, p < 0.001). Regarding secondary outcomes, patients in the NE-PE group had longer lengths of stay in ICU and hospitals. Patients in the NE-PE group also received mechanical ventilation for longer durations.

CONCLUSIONS

NE combined with PE was inferior to NE alone in patients with septic shock, and it was associated with a higher hospital mortality rate.

Perioperative hemodynamic optimization: from guidelines to implementation-an experts' opinion paper

Despite a large body of evidence, the implementation of guidelines on hemodynamic optimization and goal-directed therapy remains limited in daily routine practice. To facilitate/accelerate this implementation, a panel of experts in the field proposes an approach based on six relevant questions/answers that are frequently mentioned by clinicians, using a critical appraisal of the literature and a modified Delphi process. The mean arterial pressure is a major determinant of organ perfusion, so that the authors unanimously recommend not to tolerate absolute values below 65 mmHg during surgery to reduce the risk of postoperative organ dysfunction. Despite well-identified limitations, the authors unanimously propose the use of dynamic indices to rationalize fluid therapy in a large number of patients undergoing non-cardiac surgery, pending the implementation of a “validity criteria checklist” before applying volume expansion. The authors recommend with a good agreement mini- or non-invasive stroke volume/cardiac output monitoring in moderate to high-risk surgical patients to optimize fluid therapy on an individual basis and avoid volume overload. The authors propose to use fluids and vasoconstrictors in combination to achieve optimal blood flow and maintain perfusion pressure above the thresholds considered at risk. Although purchase of disposable sensors and stand-alone monitors will result in additional costs, the authors unanimously acknowledge that there are data strongly suggesting this may be counterbalanced by a sustained reduction in postoperative morbidity and hospital lengths of stay. Beside existing guidelines, knowledge and explicit clinical reasoning tools followed by decision algorithms are mandatory to implement individualized hemodynamic optimization strategies and reduce postoperative morbidity and duration of hospital stay in high-risk surgical patients.