Effect of Mild Hypercapnia on Lung Oxygenation in Sitting Position During Shoulder Arthroscopy Under General Anesthesia

Abstract

BackgroundMild hypercapnia is permitted during surgeries in sitting position under general anesthesia to maintain cerebral regional oxygen saturation (rSO2). However, since hypoventilation may cause gas exchange impairment, we evaluated effects of mild hypercapnia on lung oxygenation during shoulder arthroscopy in sitting position.Material/MethodsForty patients were randomly allocated to a normocapnia group (ETCO2 35 mmHg, n=20) or a hypercapnia group (45 mmHg, n=20). The mean arterial pressure (MAP), heart rate (HR), and rSO2 were measured 5 min after intubation in supine position (T0), and at 2, 4, 6, 8, 10, 20, 30, 40, 50, and 60 min of remaining in sitting position (T1–10). Arterial blood gas was analyzed at T0 and T5. The oxygenation index (PaO2/FiO2) and dead-space ventilation ratio (Vd/Vt) were calculated.ResultsThere were no differences in PaO2/FiO2 at T0 and T5 between the 2 groups. At T5, the Vd/Vt was higher in the normocapnia group than in the hypercapnia group (p=0.04). The Vd/Vt at T5 increased from T0 in the normocapnia group. The incidence of cerebral desaturation in the hypercapnia group (0/20) was lower than in the normocapnia group (5/20) (p=0.047). Among rSO2, MAP, and HR, only changes in rSO2 over time between the 2 groups differed significantly (p=0.048).ConclusionsMild hypercapnia did not decrease lung oxygenation in sitting position, probably due to attenuation of the increase in dead-space ventilation ratio. Since hypercapnia maintained rSO2 without changes in oxygenation index and hemodynamic parameters, mild hypercapnia should be maintained during shoulder arthroscopy in sitting position under general anesthesia.

Prophylactic measures to prevent cerebral oxygen desaturation events in elective beach-chair position shoulder surgeries: a systematic review and meta-analysis

“…Cerebral oxygenation monitoring was performed using INVOS™ 5100 B/C (Medtronic, Ireland) cerebral oximetry monitoring devices [ 7 , 13 , 20 - 27 , 29 ] (near-infrared reflectance spectroscopy) in all included studies in this review, except in a single study [ 28 ] in which the FORE-SIGHT™ device (Edwards Lifesciences, USA) was used. All the studies reported baseline data with respect to rSO 2 including pre- and post-induction values, except for a single study [ 24 ] in which only the mean (SD) maximum fall of cerebral saturation values was reported.…”

“…To simplify, we classified the included heterogeneous studies based on whether the study authors used pharmacological (PPMs) or non-pharmacological prophylactic measures (NPPMs). For the prevention of MAP-dependent cerebral desaturations, PPMs were used in four RCTs (vasoactive agents; vasopressin [ 20 , 21 , 25 ], n = 3 and phenylephrine [ 7 ], n = 1) and NPPMs in eight (preloading with colloid [HES 130/0.4 [ 22 ], n = 1]; SCD use on legs [ 26 ], n = 1; compression stockings [ 13 , 24 ], n = 2; targeted mild hypercarbia [ 27 , 28 ], n = 2; or reduced BCP angle for surgery [ 23 ] [low BCP angle, ≤ 60º, n = 1] or RIPC [ 29 ], n = 1]). However, overlapping prophylactic measures were observed among the study groups.…”

“…Eight study groups [ 13 , 20 , 21 , 24 ] used compression stockings and five used SCDs [ 23 , 24 , 26 ] as a prophylactic measure. Crystalloid loading [ 7 , 21 , 22 , 29 ] and HES preloading [ 22 , 26 , 27 ] were used in 10 and 5 study groups, respectively. Vasoactive agent prophylaxis [ 7 , 20 , 21 , 25 ] was used in seven, whereas targeted mild hypercarbia [ 27 , 28 ] was used in two study groups.…”

“…Crystalloid loading [ 7 , 21 , 22 , 29 ] and HES preloading [ 22 , 26 , 27 ] were used in 10 and 5 study groups, respectively. Vasoactive agent prophylaxis [ 7 , 20 , 21 , 25 ] was used in seven, whereas targeted mild hypercarbia [ 27 , 28 ] was used in two study groups. Similarly, low BCP angle [ 13 , 23 , 24 ] during surgery was used in five study groups.…”

Hypercapnia in the critically ill: insights from the bench to the bedside

“…Permissive HC was induced to 45 mmHg PaCO 2 in patients undergoing surgery in a reclined seated position which commonly results in an impaired haemodynamic stability at baseline. The results of this study demonstrated that mild HC prevented the reduction of cerebral oxygen saturation without changes in oxygenation index and haemodynamic parameters [ 96 ].…”