Clinical trial NCT01983618: Impact of Interscalene Nerve Block on Cerebral Perfusion During Surgery in the Beachchair Position
Official title: Impact of Interscalene Nerve Block on Cerebral Perfusion During Surgery in the Beachchair Position Under General Anesthesia
Study type: INTERVENTIONAL
Overall status: COMPLETED
Phase: NA
Conditions: Cerebral Ischemia
Keywords: Cerebral ischemia
Beachchair position
Interscalene nerve block
Lead sponsor: Centre hospitalier de l'Université de Montréal (CHUM)
Sponsor class: OTHER
First posted: 2013-11-14
Enrollment: 25
Sex: ALL
Minimum age (years): 18
Standard ages: ADULT
OLDER_ADULT
Accepts healthy volunteers: no
Allocation: RANDOMIZED
Intervention model: PARALLEL
Primary purpose: PREVENTION

Brief summary: Beachchair position is used by many orthopaedic surgeons for shoulder surgery. Most patients undergoing surgery in this position have no complications. However, reported cases of postoperative neurological deficits have highlighted the risk of cerebral and spinal cord ischemia. The etiology of such complications remains unclear. The most plausible explanation for these events would be intraoperative hypotension followed by cerebral hypoperfusion.

General anesthesia is commonly used for shoulder surgery in conjunction with interscalene brachial plexus blockade. During the block, local anesthetic's spread is frequently observed leading to a block of sympathetic fibres. Since all nerves located in the head and neck area go through the stellate ganglion, its block will cause a sympathetic denervation and a decrease of the peripheral vascular resistance, thus increasing the circulation in cerebral blood vessels. In normal situations, there is a vasoconstriction of the cerebral blood vessels in response to a sympathetic stimulation and a vasodilation if sympathetic fibres are blocked.

Transcranial Doppler (TCD) is a non-invasive examination that provides a reliable evaluation of intracranial blood flow in real-time. It can help to detect sudden changes in perfusion and identify potential embolic events. Some studies using TCD have shown an increased ipsilateral cerebral blood flow (CBF) secondary to a reduced vascular tone associated with a stellate ganglion block. Others have shown a reduction of contralateral CBF that could theoretically increase the risk of ischemia in the affected area.

This study will assess the role of interscalene nerve blockade in the protection of cerebral ischemia and preservation of cerebral autoregulation. This study will also aim to identify changes in contralateral CBF.

The investigators hypothesize that:

1. Interscalene nerve block will increase CBF
2. Interscalene nerve block will not decrease contralateral CBF
3. Cerebral autoregulation will be preserved under general anesthesia in conjunction with an interscalene nerve block in this setting.

Detailed description: Prior to surgery, each patient will undergo a baseline bilateral TCD examination in supine position. If the Doppler's results are satisfactory, the patient will then be randomized and proceed to the next step. In case of inadequate results, the patient's participation to the study will be terminated.

The interscalene nerve block and the insertion of the interscalene catheter will be performed according to randomization. In the interscalene nerve block and catheter group, the attending anaesthesiologist will assess the success of the block and record the presence or absence of Horner's syndrome. The transcranial Doppler operator will be blinded to these observations. Following the insertion of the interscalene catheter, the patient will undergo a second bilateral TCD in supine position before induction of anesthesia.

The anesthetic technique and monitoring will be standardized. After the induction of anesthesia, a bilateral TCD will be performed with the patient in supine position. Another examination will be performed under general anesthesia immediately after and 30 minutes following the installation of the patient in the beachchair position. A last TCD will be performed after a reduction of end-tidal carbon dioxide at 30 mm Hg.

For each examination, the arterial blood pressure must be stabilized for at least 5 minutes before the Doppler can be initiated. Arterial blood pressure will be measured during each examination. Type, duration of surgery and beachchair position will be recorded. Vasopressor therapy will be noted. Body temperature, end-tidal carbon dioxide and minimum alveolar concentration of desflurane will be collected during each examination performed under general anesthesia.

Eligibility criteria: Inclusion Criteria:

* Scheduled for shoulder surgery in the sitting position
* Surgery of the shoulder and clavicular area, eligible to an interscalene nerve block
* American Society of Anesthesiologists (ASA) physical status 1-3

Exclusion Criteria:

* Carotid artery stenosis
* History of stroke or other significant central nervous system lesion
* Inadequate temporal window to perform transcranial Doppler
* Contraindication to interscalene nerve block
* Patient refusal

Primary outcomes:
measure: Cerebral blood flow in the median cerebral artery
timeFrame: From arrival in the operating theatre until the end of surgery. Patients will be followed for an average of 3 hours.
Secondary outcomes:
measure: Arterial blood pressure
timeFrame: From arrival in the operating theatre until the end of surgery. Patients will be followed for an average of 3 hours.
measure: Body temperature
timeFrame: From induction of anesthesia until the end of surgery. Patients will be followed for an average of 2 hours.
measure: End-tidal carbon dioxide
timeFrame: From induction of anesthesia until the end of surgery. Patients will be followed for an average of 2 hours.
measure: Minimum alveolar concentration (MAC) of Desflurane
timeFrame: From induction of anesthesia until the end of surgery. Patients will be followed for an average of 2 hours.
Other outcomes:
Locations:
city: Montreal
country: Canada
facility: Centre Hospitalier de l'Université de Montréal (CHUM)
state: Quebec
Study officials:
affiliation: Centre hospitalier de l'Université de Montréal (CHUM)
name: Sébastien Garneau, MD, FRCPC
role: PRINCIPAL_INVESTIGATOR
References: