Effects on cerebral blood flow of position changes, hyperoxia, CO2 partial pressure variations and the Valsalva manoeuvre: A study in healthy volunteers. Issue 1 (January 2021)

• Record Type: Journal Article
• Authors: Tercero, Javier; Gracia, Isabel; Hurtado, Paola; de Riva, Nicolás; Carrero, Enrique; Garcia-Orellana, Marta; Belda, Isabel; Rios, José; Maldonado, Felipe; Fàbregas, Neus; Valero, Ricard
• Other Names: 2020 Published online 16 October section editor.
• Is Part Of: European journal of anaesthesiology. Volume 38:Issue 1(2021)
• Publication Date: 2021-01
• Subjects: Anesthesiology -- Periodicals; Anesthesiology -- Periodicals; Anesthésiologie -- Périodiques; Anesthesiology; Periodicals; Electronic journals; 617.96
• DOI: 10.1097/EJA.0000000000001356
• Languages: English
• ISSNs: 0265-0215

Abstract

Abstract : BACKGROUND: Maintaining adequate blood pressure to ensure proper cerebral blood flow (CBF) during surgery is challenging. Induced mild hypotension, sitting position or unavoidable intra-operative circumstances such as haemorrhage, added to variations in carbon dioxide and oxygen tensions, may influence perfusion. Several of these circumstances may coincide and it is unclear how these may affect CBF. OBJECTIVE: To describe the variation in transcranial Doppler and regional cerebral oxygen saturation (r S O2 ), as a surrogate of CBF, after cardiac preload and gravitational positional changes. DESIGN: Observational study. SETTING: Operating room at Hospital Clínic de Barcelona. VOLUNTEERS: Ten healthy volunteers, white, both sexes. INTERVENTIONS: Measurements were performed in the supine, sitting and standing positions during hyperoxia, hypocapnia and hypercapnia protocols and after a Valsalva manoeuvre. MAIN OUTCOME MEASURES: Cardiac index (CI), haemodynamic and respiratory variables, maximal and mean velocities ( V max, V mean ) (transcranial Doppler) and r S O2 were acquired. Results were analysed using a generalised estimating equation technique. RESULTS: CI increases more than 16% after a preload challenge were not accompanied by differences in r S O2 or V max − V mean . With positional changes, V mean decreased more than 7% ( P = 0.042) from the supine to the seated position. Hyperoxia induced a cerebral r S O2 increase more than 6% ( P = 0.0001) with decreases in V max, V mean and CI values more than 3% ( P = 0.001, 0.022 and 0.001) in the supine and standing position. During hypocapnia, CI rose more than 20% from supine to seated and standing ( P = 0.0001) with a 4.5% decrease in cerebral r S O2 ( P = 0.001) and a decrease of V max − V mean more than 24% in all positions ( P = 0.001). Hypercapnia increased cerebral r S O2 more than 17% ( P = 0.001), V max − V mean more than 30% ( P = 0.001) with no changes in CI. After a Valsalva manoeuvre, r S O2 decreased more than 3% in the right hemisphere in the upright position ( P = 0.001). V max − V mean decreased more than 10% ( P = 0.001) with no changes in CI. CONCLUSION: CBF changes in response to cerebral vasoconstriction and vasodilatation were detected with r S O2 and transcranial Doppler in healthy volunteers during cardiac preload and in different body positions. Acute hypercapnia had a greater effect on recorded brain parameters than hypocapnia. Abstract : Supplemental Digital Content is available in the text