Analgesic duration of interscalene block after outpatient arthroscopic shoulder surgery with intravenous dexamethasone, intravenous dexmedetomidine, or their combination: a randomized-controlled trial.

PURPOSE: Both intravenous dexamethasone and dexmedetomidine prolong the analgesic duration of interscalene blocks (ISB) after arthroscopic shoulder surgery. This study compared their relative effectiveness and the benefit of their use in combination. METHODS: This single-centre, double-blinded, parallel three-group superiority trial randomized 198 adult patients undergoing ambulatory arthroscopic shoulder surgery. Patients received preoperative ISB with 30 mL 0.5% bupivacaine and 50 µg dexmedetomidine or 4 mg dexamethasone or both of these agents as intravenous adjuncts. The primary outcome was analgesic block duration. Secondary outcomes included the quality of recovery 15 score (range: 0-150) on day 1 and postoperative neurologic symptoms in the surgical arm. RESULTS: Block durations (n = 195) with dexamethasone (median [range], 24.5 [2.0-339.5] hr) and both adjuncts (24.0 [1.5-157.0] hr) were prolonged compared with dexmedetomidine (16.0 [1.5-154.0] hr). When analyzed by linear regression after an unplanned log transformation because of right-skewed data, the corresponding prolongations of block duration were 59% (95% confidence interval [CI], 28 to 97) and 46% (95% CI, 18 to 80), respectively (both P < 0.001). The combined adjuncts were not superior to dexamethasone alone (-8%; 95% CI, -26 to 14; P = 0.42). Median [IQR] quality of recovery 15 scores (n = 197) were significantly different only between dexamethasone (126 [79-149]) and dexmedetomidine (118.5 [41-150], P = 0.004), but by an amount less than the 8-point minimum clinically important difference. CONCLUSION: Dexamethasone is superior to dexmedetomidine as an intravenous adjunct for prolongation of bupivacaine-based ISB analgesic duration. There was no additional benefit to using both adjuncts in combination. TRIAL REGISTRATION: www.clinicaltrials.gov (NCT03270033); registered 1 September 2017.

RéSUMé: OBJECTIF: La dexaméthasone et la dexmédétomidine intraveineuses prolongent toutes deux la durée analgésique des blocs interscaléniques (BIS) après une chirurgie arthroscopique de l'épaule. Cette étude a comparé leur efficacité relative et les avantages d'une utilisation des deux agents en combinaison. MéTHODE: Cette étude de supériorité monocentrique en trois groupes parallèles à double insu a randomisé 198 patients adultes subissant une chirurgie arthroscopique de l'épaule en ambulatoire. Les patients ont reçu un BIS préopératoire composé de 30 mL de bupivacaïne 0,5 % avec 50 µg de dexmédétomidine, 4 mg de dexaméthasone, ou la combinaison de ces deux agents comme adjuvants intraveineux. Le critère d'évaluation principal était la durée analgésique du bloc. Les critères d'évaluation secondaires comprenaient le score de qualité de récupération (QoR) 15 (plage : 0-150) au jour 1 et les symptômes neurologiques postopératoires dans le bras opéré. RéSULTATS: Les durées des blocs (n = 195) avec la dexaméthasone (médiane [plage], 24,5 [2,0-339,5] heures) et la combinaison des deux adjuvants (24,0 [1,5-157,0] heures) ont été prolongées par rapport à la dexmédétomidine (16,0 [1,5-154,0] heures). Lorsqu'elles ont été analysées par régression linéaire après une transformation logarithmique non planifiée en raison de données biaisées vers la droite, les prolongations correspondantes de la durée du bloc étaient de 59 % (intervalle de confiance [IC] 95 %, 28 à 97) et de 46 % (IC 95 %, 18 à 80), respectivement (les deux P < 0,001). La combinaison des adjuvants n'était pas supérieure à la dexaméthasone seule (-8 %; IC 95 %, -26 à 14; P = 0,42). Les scores médians [ÉIQ] de qualité de récupération 15 (n = 197) n'étaient significativement différents qu'entre la dexaméthasone (126 [79-149]) et la dexmédétomidine (118,5 [41-150], P = 0,004), mais la différence observée était inférieure à la différence minimale de 8 points nécessaire pour être considérée cliniquement importante. CONCLUSION: La dexaméthasone est supérieure à la dexmédétomidine en tant qu'adjuvant intraveineux pour prolonger la durée analgésique d'un BIS à base de bupivacaïne. Aucun avantage supplémentaire n'a été observé lors de l'utilisation combinée des deux adjuvants. ENREGISTREMENT DE L'éTUDE: www.clinicaltrials.gov (NCT03270033); enregistrée le 1er septembre 2017.

Brain BOLD MRI O2 and CO2 stress testing: implications for perioperative neurocognitive disorder following surgery.

BACKGROUND: Mechanical ventilation to alter and improve respiratory gases is a fundamental feature of critical care and intraoperative anesthesia management. The range of inspired O2 and expired CO2 during patient management can significantly deviate from values in the healthy awake state. It has long been appreciated that hyperoxia can have deleterious effects on organs, especially the lung and retina. Recent work shows intraoperative end-tidal (ET) CO2 management influences the incidence of perioperative neurocognitive disorder (POND). The interaction of O2 and CO2 on cerebral blood flow (CBF) and oxygenation with alterations common in the critical care and operating room environments has not been well studied. METHODS: We examine the effects of controlled alterations in both ET O2 and CO2 on cerebral blood flow (CBF) in awake adults using blood oxygenation level-dependent (BOLD) and pseudo-continuous arterial spin labeling (pCASL) MRI. Twelve healthy adults had BOLD and CBF responses measured to alterations in ET CO2 and O2 in various combinations commonly observed during anesthesia. RESULTS: Dynamic alterations in regional BOLD and CBF were seen in all subjects with expected and inverse brain voxel responses to both stimuli. These effects were incremental and rapid (within seconds). The most dramatic effects were seen with combined hyperoxia and hypocapnia. Inverse responses increased with age suggesting greater risk. CONCLUSIONS: Human CBF responds dramatically to alterations in ET gas tensions commonly seen during anesthesia and in critical care. Such alterations may contribute to delirium following surgery and under certain circumstances in the critical care environment. TRIAL REGISTRATION: ClincialTrials.gov NCT02126215 for some components of the study. First registered April 29, 2014.

The Incidence and Magnitude of Cerebral Desaturation in Traumatic Brain Injury: An Observational Cohort Study.

BACKGROUND: Cerebral ischemia in patients with traumatic brain injury (TBI) may propagate secondary neurological injury. Episodes of cerebral ischemia can be revealed through the use of cerebral oximetry monitoring. The objective of this study was to determine the incidence and severity of regional cerebral oxygen (rSO2) desaturation (rSO2<65%) in patients with severe TBI. Secondary outcomes included changes in other monitoring parameters associated with cerebral desaturation. MATERIALS AND METHODS: In this single-center prospective observational cohort study, cerebral oximetry data were collected continuously for up to 72 hours in 18 adult patients with a diagnosis of severe nonpenetrating TBI who were being mechanically ventilated and undergoing intracranial pressure (ICP) monitoring an in intensive care unit in Canada. Mean arterial pressure (MAP), ICP, and cerebral perfusion pressure were collected at 5-minute intervals during the study period. RESULTS: Twelve of 18 (67%) patients experienced an episode of cerebral desaturation. The median (interquartile range) nadir rSO2 was 57% (51% to 62%). The duration of desaturation was 265 (57 to 1277) minutes or 8.1% (2.6% to 26.0%) of recording time. In all patients, a linear regression analysis of the area under threshold of 65% for rSO2 was moderately correlated with the area above an ICP threshold of 20 mm Hg (R2=0.52; P<0.01). Similarly, there was a modest correlation between rSO2 and MAP (R2=0.41; P<0.01). These relationships also held true for those patients who experienced cerebral desaturation. Patients having episodes of ICP >20 mm Hg were 6 times more likely to have a cerebral desaturation (relative risk: 6.0; 95% confidence interval: 1.3-34.7). CONCLUSIONS: Cerebral desaturations occur frequently in patients with severe TBI, and their duration can be protracted. Episodes of desaturation were moderately correlated with increased ICP and decreased MAP.