Cerebral Blood Flow Evaluation With Trancranial Doppler After Interscalene Nerve Block

Study Results

Results pending

The study team has not published outcome measurements, participant flow, or safety data for this trial yet. Check back later for updates.

Basic Information

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Recruitment Status

TERMINATED

Total Enrollment

10 participants

Study Classification

OBSERVATIONAL

Study Start Date

2021-03-04

Study Completion Date

2021-07-30

Brief Summary

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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.

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Detailed Description

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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).

Conditions

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Regional Anesthesia Horner Syndrome Cerebral Blood Flow

Study Design

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Observational Model Type

COHORT

Study Time Perspective

PROSPECTIVE

Study Groups

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Treatment Arm

Patients ages 18-85 years old presenting with orthopedic shoulder surgery with indication to receive preoperative insertion of interscalene nerve block.

TCD Measurement

Intervention Type DEVICE

CBFV measurements will be acquired continuously with the patient supine and the head neutral. Analysis of CBFV measurements will be undertaken at 3 timepoints:

1. Patient awake and supine in the holding area
2. After sedation
3. After interscalene nerve block

Interventions

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TCD Measurement

CBFV measurements will be acquired continuously with the patient supine and the head neutral. Analysis of CBFV measurements will be undertaken at 3 timepoints:

1. Patient awake and supine in the holding area
2. After sedation
3. After interscalene nerve block

Intervention Type DEVICE

Eligibility Criteria

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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