Delirium is a common complication in elderly intensive care unit (ICU) patients and is associated with poor clinical outcomes. Circadian rhythm disruption is considered an important contributing factor in delirium development. Stellate ganglion block (SGB) may modulate autonomic nervous system activity and improve circadian rhythm regulation.
This prospective randomized placebo-controlled trial aims to evaluate the effects of ultrasound-guided stellate ganglion block on delirium incidence and circadian rhythm in ICU patients aged 65 years and older. Delirium will be assessed using validated clinical scales, and circadian rhythm will be evaluated through serial measurements of serum melatonin and plasma cortisol levels
Patients aged 65 years or older expected to remain in the intensive care unit for more than 48 hours
RASS score > -4
History of neurodegenerative disease (e.g., Alzheimer's disease, dementia, vascular dementia)
Uncontrolled psychiatric disorders
Alcohol use disorder and/or substance abuse
History of traumatic brain injury or ischemic/hemorrhagic cerebrovascular event
Parallel
stellate ganglion block with 0.5% bupivacaine
Procedure/SurgeryUltrasound-guided stellate ganglion block will be performed in the supine position using 5 mL of 0.5% bupivacaine administered by an experienced anesthesiologist.
Placebo Injection
Procedure/SurgeryUltrasound-guided sham procedure will be performed, consisting of 2 mL normal saline administered as an intramuscular injection into the anterolateral cervical region, without targeting the stellate ganglion.
Incidence of delirium
Delirium incidence will be assessed in patients receiving stellate ganglion block and in patients not receiving stellate ganglion block using a standardized two-step evaluation process. Patients will first be assessed with the Richmond Agitation-Sedation Scale (RASS), which ranges from -5 (unarousable) to +4 (combative). Only patients with a RASS score greater than -4 will undergo delirium assessment using the Confusion Assessment Method for the Intensive Care Unit (CAM-ICU), a validated diagnostic instrument for delirium. Delirium will be recorded as present or absent according to CAM-ICU findings. Higher RASS scores indicate increased agitation, whereas lower scores indicate deeper sedation. Minimum and maximum scores are not applicable to CAM-ICU because it is used as a binary diagnostic tool rather than a numerical scale.
Serum melatonin circadian pattern
Serum melatonin levels will be measured at predefined time points to assess circadian rhythm pattern. Blood samples will be obtained at 03:00, 08:00, and 16:00. Results will be reported in pg/mL. Circadian rhythm assessment will be based on whether the temporal profile of melatonin secretion across these predefined sampling times is consistent with the expected physiological circadian pattern, rather than on isolated measurements alone.
Plasma cortisol circadian pattern
Plasma cortisol levels will be measured at predefined time points to assess circadian rhythm pattern. Blood samples will be obtained at 03:00, 08:00, and 16:00. Results will be reported in µg/dL. Circadian rhythm assessment will be based on whether the temporal profile of cortisol secretion across these predefined sampling times is consistent with the expected physiological circadian pattern, rather than on isolated measurements alone.
Delirium severity (Delirium Rating Scale-Revised-98 score)
Delirium severity will be assessed using the Delirium Rating Scale-Revised-98 (DRS-R-98), which ranges from 0 to 46. Higher scores indicate more severe delirium. The scale will be applied only in patients diagnosed with delirium according to CAM-ICU.
Delirium motor subtype distribution
Delirium motor subtypes will be classified as hyperactive, hypoactive, or mixed based on the Richmond Agitation-Sedation Scale (RASS) scores in patients diagnosed with delirium using CAM-ICU. Hyperactive delirium will be defined as RASS \> 0, hypoactive delirium as RASS \< 0, and mixed delirium as fluctuation between positive and negative RASS scores during the assessment period. The outcome will be reported as the distribution of delirium subtypes across study groups.
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