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October 18, 2010
9:00:00 AM - 11:00:00 AM
Room Hall B1-Area B
TSE "Mask" Prevents Severe O2 Desaturation in Obese Patients at No Cost during Retrobulbar Block
  **   Sylviana Barsoum, M.D., Shaul Cohen, M.D., Jorge Mendez, M.D., Christine W. Hunter, M.D., James Tse, Ph.D., M.D.
Anesthesia, UMDNJ-Robert Wood Johnson Medical School, New Brunswick, New Jersey
INTRODUCTION: Patients undergoing vitrectomy or scleral buckle routinely receive pre-oxygenation with nasal cannula (NC) and iv propofol during retrobulbar block. Deep sedation is often required to avoid patient movement during injection of local anesthetics. However, it may cause respiratory depression and/or airway obstruction, especially in obese patients. Severe desaturation (Desat) may occur while the needle is in retrobulbar area. A plastic sheet has been shown to convert a NC to a face tent (TSE "Mask") in 10 sec at no cost.1-3 It improves oxygenation and reduces severe Desat in patients during upper endoscopy.3 This technique has been used in "Eye Room". We wish to confirm its effectiveness in preventing Desat in obese patients

METHODS: This retrospective review of patients undergoing vitrectomy or scleral buckle identified 2 groups. Group 1 (NC, n=66) received only NC O2. Group 2 (TM, n=76) received NC O2 and a TSE "Mask" using a NC plastic bag to cover patient's nose and mouth.1-2 It was removed prior to sterile preparation to avoid the possibility of causing airway obstruction or suffocation during the case. Patients received NC O2 (3-5 l/min, or higher) and iv propofol. Data collected included age, weight, height, O2 saturation (Sat), propofol dose, assisted ventilation and FiO2. Student t-test and Chi Square test were used for analysis. A p value <0.05 was considered as significant. (Mean±S.D.)

RESULTS: Among non-obese patients (BMI <30), there were no differences in age (NC: 68±15; TM: 68±15), BMI (NC: 24.6±3.0; TM: 25.1±2.7), ASA Physical status (NC: 2.1±0.7; TM: 2.2±1), room air (RA) O2 Sat (NC: 99±2%; TM: 98±2%), the highest O2 flow (NC: 5.2±2.5 l/min; TM: 4.1±0.7), O2 Sat after 5 min with O2 (NC: 99±1%; TM: 100±1%) and assisted ventilation (NC: 3/49; TM: 0/54) between NC (n=49) and TM (n=54) groups. There were significant differences in the lowest O2 Sat (NC: 93±6%; TM: 99±2%), severe Desat (O2 Sat ≤85%) (NC: 5/49; TM: 0/54) and propofol dose (1.2±0.5 mg/kg; TM: 1.4±0.3).[figure1]Among obese patients, there were no differences in BMI (NC: 34.5±4.4; TM: 33.9±2.9), ASA Physical status (NC: 2.0±0.7; TM: 2.4±0.7), RA O2 Sat (NC: 99±1%; TM: 98±2%), the highest O2 flow (NC: 5.4±2.6 l/min; TM: 4.4±1.0), propofol dose (1.1±0.3 mg/kg; TM: 1.1±0.4), and assisted ventilation (NC: 2/17; TM: 0/22) between NC (n=17) and TM (n=22). There were significant differences in age (NC: 61±15 yrs; TM: 71±14), O2 Sat after 5 min with O2 (NC:99±1%; TM:100±0%), the lowest O2 Sat (NC: 89±6%; TM: 96±6%) and severe Desat (O2 Sat ≤85%) (NC: 5/17; TM: 1/22).Sedation had the greatest respiratory depressive effect on obese NC patients. FiO2 was measured in 7 NC and 51 TM patients (NC:0.23±0.01; TM: 0.52±0.13).

DISCUSSION: The data show that pre-oxygenation for retrobulbar block with a TSE "Mask" improves oxygenation and prevents severe Desat in deeply-sedated patients, especially in obese patients. This face tent is easy to prepare and may improve patient safety at no cost.

REF: 1. Anesth 102:484, 2005; 2.; 3. Anesth 107:A922, 2007.

From Proceedings of the 2010 Annual Meeting of the American Society Anesthesiologists.
Figure 1