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To assess the impact of short time hypnosis for retro-bulbar anesthesia on ventilation in patients undergoing ophthalmic surgery of the anterior eye chamber. In all patients, a combined continuous transcutaneous carbon dioxide tension (PtcCO 2 ) and partial oxygen saturation (SpO 2 ) measurement was applied in addition to routine monitoring. To enable unconscious application of retro-bulbar anesthesia, intravenous thiopental was given in one to multiple bolus doses. Transient breathing support included chin lift, Esmarch maneuver and manual hand-bag ventilation via face mask. Main endpoints were apnea time, recovery time according to the Richmond Agitation Sedation Scale, as well as SpO 2 and PtcCO 2 readings at predefined time points. Fifty-two patients with a mean age of 68 ± 13 years were included. Average thiopental dose was 2.7 ± 0.6 mg/kg. In seven (13.5%) patients repeated doses of thiopental were necessary to a total of 3.3 ± 1.1 mg/kg. Except one patient, no severe, significant or clinical relevant hypercapnia or desaturation periods were observed, and the occurring elevation of PtcCO 2 values did not correlate with the application of repeated doses of thiopental or the need for the Esmarch maneuver. Higher PtcCO 2 values were associated with the presence of hypertension and smoking. Apnea (p < 0.001) and recovery (p = 0.003) time were significantly prolonged in the patients needing the Esmarch maneuver. Short term anesthesia with thiopental in ophthalmic surgery is associated with a mild but not clinically relevant hypercapnia.

The Masimo Radical-7 Pulse CO-Oximeter (Masimo Corp., USA) non-invasively computes hemoglobin concentration (SpHb). SpHb was compared to Co-Oximeter readings (CoOxHb) of arterial samples in surgery patients of the emergency department. Forty-six patients were enrolled. The Masimo R1 25L (revision F and G) adult adhesive sensor was attached to the ring finger of the arterially cannulated hand. Before start, every 30 min during surgery and in the case of severe bleeding SpHb and CoOxHb values were documented. SpHb and post hoc adjusted SpHb (AdSpHb) values were analyzed. Linear regression analysis and Bland-Altman plot for agreement were performed. The detection failure rate of SpHb was 24.5 %. CoOxHb and SpHb showed a strong correlation (r = +0.81), but agreement was moderate [bias (LOA) of -0.6 (-3.0; +1.9)] g/dl. Positive and negative predicted value was 0.49 and 0.69. Exclusion of changes of CoOxHb values ≤1 g/dl resulted in a positive and negative predictive value of 0.66 and 1.00. Post hoc adjustment of the SpHb (AdSpHb) improved linear correlation of CoOxHb and AdSpHb [r = +0.90 (p < 0.001)] but less the agreement [bias (LOA) of CoOxHb and AdSpHb = -0.1 (-2.1/+1.9) g/dl]. SpHb agreed only moderately with CoOxHb values and predicted decreases of CoOxHb only if changes of SpHb ≤ 1.0 g/dl were excluded. The detection failure rate of SpHb was high. At present, additional refinements of the current technology are necessary to further improve performance of non-invasive hemoglobin measurement in the clinical setting.

We studied the impact of transcutaneous continuous carbon dioxide tension (PtcCO2) monitoring on ventilation and oxygenation during monitored anaesthesia care (MAC) in patients scheduled for shoulder surgery with continuous interscalene block. 50 patients were randomised either to the intervention (I-group) or the control (C-group) group. In both groups MAC was performed using target controlled infusion of propofol and remifentanil. MAC regimen was adapted to PtcCO2 values in the I-group, whereas the C-group was blinded for these values. Primary outcome was the incidence, degree and duration of hypoventilation stages. In the I-group and the C-group the mean ± SD [range] of PtcCO2 and PaCO2 was 5.79 ± 0.84 [4.37] and 5.44 ± 0.59 [2.78] kPa, as well as 6.41 ± 1.17 [6.29] and 6.01 ± 0.96 [7.15] kPa. Periods of PtcCO2/PaCO2 > 6.5 kPa were 21.0 ± 35.7/1.2 ± 4.2 min in the I-group and 45.6 ± 40.0/18.6 ± 26.8 min in the C-group. Severe hypercapnia (PtcCO2 and/or PaCO2 > 7.5 kPa) was dected in 3/0 patients of the I-group and in 10/3 patients of the C-group. PtcCO2 and PaCO2 showed a strong correlation (r = 0.78), but only moderate agreement with a mean bias (LOA) of -0.37 (-1.69; +0.95) kPa showing an overestimation of the PaCO2. Sensitivity and specificity of PtcCO2 to detect changes of PaCO2 was 0.94 and 0.56, respectively. In no patient SpO2 or SaO2 values lower than 90% were measured. Despite a moderate agreement between PaCO2 and PtcCO2 the PtcCO2 monitoring significantly reduced incidence, degree and duration of hypercapnia in shoulder surgery patients with MAC.