Clinical trial NCT04642612: Cerebral Blood Flow Evaluation With Trancranial Doppler After Interscalene Nerve Block
Official title: Cerebral Blood Flow Evaluation With Trancranial Doppler After Unilateral Interscalene Nerve Block: Observational Prospective Study
Study type: OBSERVATIONAL
Overall status: TERMINATED
Conditions: Regional Anesthesia
Horner Syndrome
Cerebral Blood Flow
Lead sponsor: Stanford University
Sponsor class: OTHER
First posted: 2020-11-24
Enrollment: 10
Sex: ALL
Minimum age (years): 18
Maximum age (years): 85
Standard ages: ADULT
OLDER_ADULT
Accepts healthy volunteers: yes
Observational model: COHORT
Time perspective: PROSPECTIVE
Sampling method: NON_PROBABILITY_SAMPLE
Study population: Patients undergoing orthopedic surgery with an indication for preoperative insertion of interscalene nerve block, aged 18-85 years old, and give consent to participating in study.

Brief summary: The purpose of this study is to assess cerebral blood flow velocity (CBFV) following regional anesthesia for shoulder surgery. The results of this study will help to further understand the physiologic effect of the interscalene nerve block on cerebral blood flow.

Detailed description: Traditionally, cerebral blood flow (CBF) is believed to decline when mean arterial pressure (MAP) is below the lower limit of cerebral autoregulation. Cerebral blood flow autoregulation refers to the capacity of the central nervous system to maintain blood flow within a wide range of mean arterial blood pressure.

The habitual thinking is that the brain is perfused merely dependent by the blood pressure and that above or below the limits of cerebral autoregularion CBF is pressure passive. Despite this notion, there is evidence showing that parameters other than MAP influence cerebral hemodynamics independent of cerebral autoregulation. One of the physiologic processes that contribute to CBF regulation is cardiac output (CO). However, exactly how an alteration in CO, in the face of a stable blood pressure, leads to a change in CBF is not entirely clear.

One of the suggested mechanisms in play is the sympathetic nervous system (SNS)-mediated vasoconstriction of extracranial and proximal intracranial vessels. Cerebral arteries are abundantly innervated by sympathetic nerve fibers originating from the superior cervical ganglion. Studies have shown that CBF reduction is attenuated by pharmacologic blockade or extirpation of the cervical sympathetic chain.

The anesthetic protocol for patients undergoing major shoulder surgery include an interscalene nerve block (ISNB) combined with general anesthesia in the sitting position. The ISNB involves injecting local anesthetic at the level of the cervical spinal roots. One of the most common side effects encountered after ISNB is Horner syndrome, which is characterized by ptosis, myosis, and enopthalmia. Horner's syndrome results from the diffusion of the local anesthetic solution to the ipsilateral sympathetic cervical chain (stellate ganglion). The presence of Horner's syndrome indicates spread of local anesthetic to the sympathetic chain.

Whether this degree of sympatholytic following interscalene block is associated with an observable change in CBF is unknown. Studies in baboon have shown that cervical surgical sympathectomy maintained CBF in the face of hemorrhagic hypotension and CBF did not decrease until MAP was 35% of the baseline value. These results suggest that sympathectomy induced by the block of the sympathetic chain by the local anesthetic injected for the ISNB might alter CBF. Therefore, the aim of our study is to evaluate the effect of unilateral interscalene nerve block on CBF by measuring CBF velocity non-invasively with Transcranial doppler (TCD).

Eligibility criteria: Inclusion Criteria:

* Patients undergoing orthopedic surgery and with an indication for preoperative insertion of interscalene nerve block
* 18-85 years old
* Give consent to participate in study

Exclusion Criteria:

* Cannot give consent
* Patients who are clinically unstable or require urgent/emergent intervention

Primary outcomes:
measure: Cerebral Blood Flow Velocity before and after interscalene nerve block
timeFrame: baseline, after 30 minutes
Secondary outcomes:
measure: Systolic, diastolic, mean blood pressure changes before and after interscalene nerve block
timeFrame: baseline, after 30 minutes
measure: Heart Rate
timeFrame: baseline, after 30 minutes
measure: Respiratory Rate changes before and after interscalene nerve block
timeFrame: baseline, after 30 minutes
measure: EtCO2 changes before and after interscalene nerve block
timeFrame: baseline, after 30 minutes
measure: SpO2 changes before and after interscalene nerve block
timeFrame: baseline, after 30 minutes
measure: Type of local anesthetic
timeFrame: 30 minutes after the nerve block
measure: Position of the needle on the cervical trunk for interscalene nerve block
timeFrame: Baseline
measure: Volume of of local anesthetic
timeFrame: 30 minutes after the nerve block
measure: Concentration of local anesthetic
timeFrame: 30 minutes after the nerve block
Other outcomes:
Locations:
city: Stanford
country: United States
facility: Stanford University School of Medicine
state: California
Study officials:
affiliation: Stanford University
name: Anna Maria Bombardieri, MD, PhD
role: PRINCIPAL_INVESTIGATOR
References:
citation: Meng L, Hou W, Chui J, Han R, Gelb AW. Cardiac Output and Cerebral Blood Flow: The Integrated Regulation of Brain Perfusion in Adult Humans. Anesthesiology. 2015 Nov;123(5):1198-208. doi: 10.1097/ALN.0000000000000872.
citation: Drummond JC. Cardiac Output: The Neglected Stepchild of the Cerebral Blood Flow Physiology Family. J Neurosurg Anesthesiol. 2020 Apr;32(2):93-94. doi: 10.1097/ANA.0000000000000677. No abstract available.
citation: ter Laan M, van Dijk JM, Elting JW, Staal MJ, Absalom AR. Sympathetic regulation of cerebral blood flow in humans: a review. Br J Anaesth. 2013 Sep;111(3):361-7. doi: 10.1093/bja/aet122. Epub 2013 Apr 24.
citation: Fitch W, MacKenzie ET, Harper AM. Effects of decreasing arterial blood pressure on cerebral blood flow in the baboon. Influence of the sympathetic nervous system. Circ Res. 1975 Nov;37(5):550-7. doi: 10.1161/01.res.37.5.550.
citation: Seltzer JL. Hoarseness and Horner's syndrome after interscalene brachial plexus block. Anesth Analg. 1977 Jul-Aug;56(4):585-6. doi: 10.1213/00000539-197707000-00033. No abstract available.