Subcutaneous oxygen and carbon dioxide tensions during head-up tilt-induced central hypovolaemia in humans

Abstract

The effect of hypovolaemic shock on subcutaneous oxygen and carbon dioxide tensions was studied in man. Subcutaneous oxygen (Psc,O2) and carbon dioxide (Psc,CO2) tensions were monitored, during 50 degrees head-up tilt (anti-Trendelenburg's position)-induced central hypovolaemia, in two females and eight males, using a silicone tonometer on the lateral upper aspect of the right arm. All cardiovascular variables remained stable at rest. Incremental tilting to 50 degrees increased heart rate (HR) and mean arterial pressure (MAP) (p < 0.01), while stroke volume (SV), cardiac output (CO) and central venous saturation (SvO2) decreased (p < 0.05). Presyncopal symptoms appeared after 28 (8-48) min (mean and range) as HR decreased from 82 (63-108) to 52 (36-70) beats min-1 (p < 0.05), MAP from 88 (61-106) to 46 (37-54) mmHg and SvO2 from 0.68 (0.56-0.76) to 0.58 (0.39-0.70) (p < 0.01). On return of the tilt table to the horizontal position HR, MAP, SV, CO and SvO2 immediately re-established resting values. The Psc,O2 was 83 (72-102) mmHg at rest and during tilting it increased to 89 (82-111) mmHg followed by a decrease to 72 (58-97) mmHg (p < 0.01) at the appearance of presyncopal symptoms. Psc,O2 returned to the pretilt level over 45 (30-60) min of recovery. Arterial oxygen, carbon dioxide and Psc,CO2 did not change significantly. Subcutaneous oxygen tension decreases during marked central hypovolaemia and it returns slowly to the resting level during recovery. Psc,O2 is a more sensitive marker of impaired tissue oxygenation than arterial oxygen pressure.

Well‐being and cerebral oxygen saturation during acute heart failure in humans

“…To reflect cerebral oxygenation, the inter‐optode distance needs to be at least 2·5 cm ( van der Zee et al ., 1992 ), and with the applied device using two receiving optodes with distances to the emitter of 3·0 and 4·0 cm, respectively, the signal is weighted towards the cerebrum although an influence of scalp ischaemia by tourniquet is noted ( Owen‐Reece et al ., 1996 ). In this study, contribution from extra‐cranial tissue to the ScO 2 signal was small: thus, the ScO 2 was stable during repeated normotensive head‐up tilts that do not affect cerebral perfusion but lower skin and subcutaneous blood flow ( Larsen et al ., 1996 ). In line with a more stable cerebral perfusion than muscle perfusion, the coefficient of variation for ScO 2 was smaller than that for SmO 2 .…”

“…To re¯ect cerebral oxygenation, the inter-optode distance needs to be at least 2á5 cm (van der Zee et al, 1992), and with the applied device using two receiving optodes with distances to the emitter of 3á0 and 4á0 cm, respectively, the signal is weighted towards the cerebrum although an in¯uence of scalp ischaemia by tourniquet is noted (Owen-Reece et al, 1996). In this Cerebral oxygenation during heart failure P. L. Madsen et al ............................................................................................................................................................................................................................................................................................................................ study, contribution from extra-cranial tissue to the ScO 2 signal was small: thus, the ScO 2 was stable during repeated normotensive head-up tilts that do not affect cerebral perfusion but lower skin and subcutaneous blood¯ow (Larsen et al, 1996). In line with a more stable cerebral perfusion than muscle perfusion, the coef®cient of variation for ScO 2 was smaller than that for SmO 2 .…”

Monitoring of peri‐operative fluid administration by individualized goal‐directed therapy

“…Although microdialysis and equilibrium dialysis are intriguing concepts, and are useful in the perception of pathophysiological mechanisms (67, 68), these monitors are unsuitable for clinical use as they require either subcutaneous placement of a cannula or placement of a probe in the rectal lumen. Moreover, the time required for the detection of deviations, as shown in CBV manipulation on a tilt table (69), limits the ability for immediate intervention. In summary, the dialysis techniques are not feasible for goal‐directed therapy.…”

The Cardiovascular System in Space: Focus on In Vivo and In Vitro Studies

“…The increase in intravascular pressure induces vasodilatation and footward fluid shift when posture is changed from a supine or recumbent position to an upright position [ 97 ]. Consequently, footward blood shift may decrease the venous return to the heart and thus decrease the SV and CO [ 123 ]. AP is the product of CO and total peripheral resistance (TPR).…”