The Effect of Retrobulbar Block for Eye Surgery on Brain Oxygenation and Cognitive Functions in Elderly Patients

The investigators measured changes in cerebral oxygen saturation (rSO2) and MMSE scores after retrobulbar block performed with levobupivacaine and lidocaine in patients undergoing vitreoretinal surgery.A total of 66 patients over the age of 60 undergoing vitreoretinal surgery with a total duration of less than 1 hour were included in this prospective, double-blinded study. The patients were randomly divided into two groups: group L (5ml, 2% lidocaine) and group LB (5ml, 0.5% levobupivacaine). Bilateral rSO2 measurements were recorded before the retrobulbar block and at 1-5 minutes post-block, during the procedure, and at 10-40 minutes post-op. MMSE was performed preoperatively and postoperatively in order to evaluate short term cognitive function. Sensory and motor block durations, pain, akinesia and conjunctival feeling scores, patient-surgeon satisfaction, and complications were also recorded.

A total of 66 patients undergoing vitreoretinal surgery (total duration \< 60 minutes) using retrobulbar block, who were classified as category I-III according to the ASA (American Society of Anesthesiologists) Classification system, who were over the age of 60, and who had no cognitive dysfunction were included in the study. Exclusion criteria were as follows: contraindication for retrobulbar block, preoperative systolic blood pressure of 180 mmHg, diastolic blood pressure of above 100 mmHg, uncontrolled diabetes, body mass index ≥ 30 kg/m2, MMSE ≤ 24, advanced organ failure, or Hb \< 9gr/dl.The patients were randomly divided into two groups using a sealed-envelope method:

Group L: Patients undergoing block with lidocaine (n = 33) Group LB: Patients undergoing block with levobupivacaine (n = 33) The patients did not undergo premedication in order to accommodate the postoperative MMSE evaluation. For intra-operative sedation, remifentanil (UltivaR, GlaxoSmithKline, Berntford, UK) was initiated as an infusion at a dose range of 0.05-0.1 mcg/kg/min. The mean arterial pressure and heart rate values were allowed to vary up to 20% of the preoperative values of the patients. For this purpose, the remifentanil infusion rate was increased or decreased at the determined dose interval.

Retrobulbar block was performed with 5 ml of 2% lidocaine hydrochloride (AritmalR, Osel, Istanbul, Turkey) in Group L patients and 5ml of 0.5% levobupivacaine (ChirocaineR, Abbvie, Chicago, USA) in Group LB patients. The block was performed by the same practitioner (fourth year assistant of Ophthalmology Department) using inferotemporal approach as described by Sanderson using 27 gage disposable needles (Atkinson Retrobulbar NeedleR, Asico, USA).

Sensory and motor block onset and end times and akinesia score were recorded. The mean arterial pressure (MAP), heart rate (HR), and oxygen saturation (SpO2) were recorded in the preoperative period, at minutes 1, 3, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, and 60 intra-operatively, and at 10, 20, 30, and 40 minutes postoperatively in the recovery room.

. The patients were transferred to the operating table for measurement of bilateral rSO2, and preoxygenation was performed for three minutes using 4 L/min 100% oxygen via nasal cannula. The basal oxygenation values were determined by taking the average of the last 30 s measurements. The rSO2 values were recorded at 1, 3, 5, 10, 15, 20, 25, 30th, 35, 40, 45, 50, 55, and 60 minutes after retrobulbar block, and at 10, 20, 30, and 40 minutes after the completion of the procedure.

Cognitive functions were assessed by the same technician using MMSE in the preoperative period, 40 minutes postoperatively and at 7 days after the operation (short term).Surgeon satisfaction was queried at the end of the case and patient satisfaction was questioned at the end of day.

Eligibility Criteria:
Inclusion Criteria:

* Undergoing vitreoretinal surgery (total duration \< 60 minutes)
* The ASA (American Society of Anesthesiologists) Classification I-III
* Over the age of 60
* The patiens who had no cognitive dysfunction

Exclusion Criteria:

* Contraindication for retrobulbar block
* Preoperative systolic blood pressure of 180 mmHg, diastolic blood pressure of above 100 mmHg
* Uncontrolled diabetes
* Body mass index ≥ 30 kg/m2
* MMSE ≤ 24
* Advanced organ failure
* Hb \< 9gr/dl