Internal carotid artery blood flow is enhanced by elevating blood pressure during combined propofol-remifentanil and thoracic epidural anaesthesia: A randomised cross-over trial

Noradrenaline-induced changes in cerebral blood flow in health, traumatic brain injury and critical illness: a systematic review with meta-analysis

BACKGROUND

Noradrenaline is a standard treatment for hypotension in acute care. The precise effects of noradrenaline on cerebral blood flow in health and disease remain unclear.

METHODS

We systematically reviewed and synthesised data from studies examining changes in cerebral blood flow in healthy participants and patients with traumatic brain injury and critical illness.

RESULTS

Twenty-eight eligible studies were included. In healthy subjects and patients without critical illness or traumatic brain injury, noradrenaline did not significantly change cerebral blood flow velocity (-1.7%, 95%CI -4.7-1.3%) despite a 24.1% (95%CI 19.4-28.7%) increase in mean arterial pressure. In patients with traumatic brain injury, noradrenaline significantly increased cerebral blood flow velocity (21.5%, 95%CI 11.0-32.0%), along with a 33.8% (95%CI 14.7-52.9%) increase in mean arterial pressure. In patients who were critically ill, noradrenaline significantly increased cerebral blood flow velocity (20.0%, 95%CI 9.7-30.3%), along with a 32.4% (95%CI 25.0-39.9%) increase in mean arterial pressure. Our analyses suggest intact cerebral autoregulation in healthy subjects and patients without critical illness or traumatic brain injury., and impaired cerebral autoregulation in patients with traumatic brain injury and who were critically ill. The extent of mean arterial pressure changes and the pre-treatment blood pressure levels may affect the magnitude of cerebral blood flow changes. Studies assessing cerebral blood flow using non-transcranial Doppler methods were inadequate and heterogeneous in enabling meaningful meta-analysis.

CONCLUSIONS

Noradrenaline significantly increases cerebral blood flow in humans with impaired, not intact, cerebral autoregulation, with the extent of changes related to the severity of functional impairment, the extent of mean arterial pressure changes and pre-treatment blood pressure levels.

Cerebral Blood Flow Assessed with Phase-contrast Magnetic Resonance Imaging during Blood Pressure Changes with Noradrenaline and Labetalol: A Trial in Healthy Volunteers

BACKGROUND

Adequate cerebral perfusion is central during general anesthesia. However, perfusion is not readily measured bedside. Clinicians currently rely mainly on mean arterial pressure (MAP) as a surrogate, even though the relationship between blood pressure and cerebral blood flow is not well understood. The aim of this study was to apply phase-contrast magnetic resonance imaging to characterize blood flow responses in healthy volunteers to commonly used pharmacologic agents that increase or decrease arterial blood pressure.

METHODS

Eighteen healthy volunteers aged 30 to 50 yr were investigated with phase-contrast magnetic resonance imaging. Intra-arterial blood pressure monitoring was used. First, intravenous noradrenaline was administered to a target MAP of 20% above baseline. After a wash-out period, intravenous labetalol was given to a target MAP of 15% below baseline. Cerebral blood flow was measured using phase-contrast magnetic resonance imaging and defined as the sum of flow in the internal carotid arteries and vertebral arteries. Cardiac output (CO) was defined as the flow in the ascending aorta.

RESULTS

Baseline median cerebral blood flow was 772 ml/min (interquartile range, 674 to 871), and CO was 5,874 ml/min (5,199 to 6,355). The median dose of noradrenaline was 0.17 µg · kg-1 · h-1 (0.14 to 0.22). During noradrenaline infusion, cerebral blood flow decreased to 705 ml/min (606 to 748; P = 0.001), and CO decreased to 4,995 ml/min (4,705 to 5,635; P = 0.01). A median dose of labetalol was 120 mg (118 to 150). After labetalol boluses, cerebral blood flow was unchanged at 769 ml/min (734 to 900; P = 0.68). CO increased to 6,413 ml/min (6,056 to 7,464; P = 0.03).

CONCLUSIONS

In healthy, awake subjects, increasing MAP using intravenous noradrenaline decreased cerebral blood flow and CO. These data do not support inducing hypertension with noradrenaline to increase cerebral blood flow. Cerebral blood flow was unchanged when decreasing MAP using labetalol.

EDITOR’S PERSPECTIVE

Effect of pneumoperitoneum and Trendelenburg position on internal carotid artery blood flow measured by ultrasound during robotic prostatectomy

INTRODUCTION

Robotic prostatectomy requires pneumoperitoneum and a steep Trendelenburg position; however, this condition may compromise cerebral blood flow. Here, we evaluated the effect of pneumoperitoneum and the steep Trendelenburg position on internal carotid artery (ICA) blood flow measured by Doppler ultrasound during robotic prostatectomy.

METHODS

Patients who underwent robotic prostatectomy were prospectively recruited. The ICA blood flow was measured at the following five time-points: with the patient awake and in the supine position (Ta), 10 min after anaesthetic induction in the supine position (T1), 10 (T2) and 30 (T3) min after pneumoperitoneum in the steep Trendelenburg position, and at the end of surgery in the supine position after desufflation of the pneumoperitoneum (T4). Hemodynamic and cerebrovascular variables were measured at each time-point.

RESULTS

A total of 28 patients were evaluated. The ICA blood flows were significantly lower at T2 and T3 than at T1 (162.3±44.7 [T2] vs. 188.0±49.6 mL/min [T1], P=0.002; 163.1±39.9 [T3] vs. 188.0±49.6 mL/min [T1], P=0.009). The ICA blood flow also differed significantly between Ta and T1 (236.8±58.3 vs. 188.0±49.6 mL/min, P<0.001). Heart rates, cardiac indexes, peak systolic velocity, and end-diastolic velocity were significantly lower at T2 and T3 than at T1. However, ICA diameter, mean blood pressure, and end-tidal carbon dioxide partial pressure did not differ significantly at all time-points.

CONCLUSION

Pneumoperitoneum and the steep Trendelenburg position caused decreased ICA blood flow, suggesting that they should be carefully performed during robotic prostatectomy, especially in patients at risk of postoperative cerebrovascular accident. This article is protected by copyright. All rights reserved.

Longitudinal assessment of preoperative dexamethasone administration on cognitive function after cardiac surgery: a 4-year follow-up of a randomized controlled trial

Background

The pathogenesis of postoperative cognitive decline (POCD) is still poorly understood; however, the inflammatory response to surgical procedures seems likely to be involved. In addition, our recent randomized controlled trial showed that perioperative corticosteroid treatment may ameliorate early POCD after cardiac surgery. To assess the long-term effect of dexamethasone administration on cognitive function, we conducted a 4-year follow-up.

Methods

The patients were randomized to receive a single intravenous bolus of 0.1 mg kg^− 1 dexamethasone or placebo 10 h before elective cardiac surgery. The endpoint in both groups was POCD incidence on the 6th day and four years postoperatively.

Results

Of the 161 patients analyzed previously, the current follow-up included 116 patients. Compared to the 62 patients in the placebo group, the 54 patients in the dexamethasone group showed a lower incidence of POCD on the 6th day (relative risk (RR), 0.510; 95 % confidence interval (CI), 0.241 to 1.079; p = 0.067, time interval also analyzed previously) and four years (RR, 0.459; 95 % CI, 0.192 to 1.100; p = 0.068) after cardiac surgery. The change in cognitive status between the two postoperative measurements was not significant (p = 0.010) among the patients in the dexamethasone group, in contrast to patients in the placebo group (p = 0.673).

Conclusions

Although statistical significance was not reached in the current study, the prophylactic administration of dexamethasone seems to be useful to prevent POCD development following cardiac surgery. However, further large multicenter research is needed to confirm these directions.

Trial registration

ClinicalTrials.gov identifier: NCT02767713 (10/05/2016).

Supplementary Information

The online version contains supplementary material available at 10.1186/s12871-021-01348-z.

Effect of low vs high haemoglobin transfusion trigger on cardiac output in patients undergoing elective vascular surgery: Post-hoc analysis of a randomized trial

BACKGROUND

During vascular surgery, restricted red-cell transfusion reduces frontal lobe oxygen (ScO₂ ) saturation as determined by near-infrared spectroscopy. We evaluated whether inadequate increase in cardiac output (CO) following haemodilution explains reduction in ScO₂ .

METHODS

This is a post-hoc analysis of data from the Transfusion in Vascular surgery (TV) Trial where patients were randomized on haemoglobin drop below 9.7 g/dL to red-cell transfusion at haemoglobin below 8.0 (low-trigger) vs 9.7 g/dL (high-trigger). Fluid administration was guided by optimizing stroke volume. We compared mean intraoperative levels of CO, haemoglobin, oxygen delivery, and CO at nadir ScO₂ with linear regression adjusted for age, operation type and baseline. Data for 46 patients randomized before end of surgery were included for analysis.

RESULTS

The low-trigger resulted in a 7.1% lower mean intraoperative haemoglobin level (mean difference, -0.74 g/dL; P < .001) and reduced volume of red-cell transfused (median [inter-quartile range], 0 [0-300] vs 450 mL [300-675]; P < .001) compared with the high-trigger group. Mean CO during surgery was numerically 7.3% higher in the low-trigger compared with the high-trigger group (mean difference, 0.36 L/min; 95% confidence interval (CI.95), -0.05 to 0.78; P = .092; n = 42). At the nadir ScO₂ -level, CO was 11.9% higher in the low-trigger group (mean difference, 0.58 L/min; CI.95, 0.10-1.07; P = .024). No difference in oxygen delivery was detected between trial groups (MD, 1.39 dL_O2 /min; CI.95, -6.16 to 8.93; P = .721).

CONCLUSION

Vascular surgical patients exposed to restrictive RBC transfusion elicit the expected increase in CO making it unlikely that their potentially limited cardiac capacity explains the associated ScO₂ decrease.