Frontiers in physiology
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Frontiers in physiology · Jan 2014
O2 supplementation to secure the near-infrared spectroscopy determined brain and muscle oxygenation in vascular surgical patients: a presentation of 100 cases.
This study addresses three questions for securing tissue oxygenation in brain (rScO2) and muscle (SmO2) for 100 patients (age 71 ± 6 years; mean ± SD) undergoing vascular surgery: (i) Does preoxygenation (inhaling 100% oxygen before anesthesia) increase tissue oxygenation, (ii) Does inhalation of 70% oxygen during surgery prevent a critical reduction in rScO2 (<50%), and (iii) is a decrease in rScO2 and/or SmO2 related to reduced blood pressure and/or cardiac output?Intravenous anesthesia was provided to all patients and the intraoperative inspired oxygen fraction was set to 0.70 while tissue oxygenation was determined by INVOS 5100C. Preoxygenation increased rScO2 (from 65 ± 8 to 72 ± 9%; P < 0.05) and SmO2 (from 75 ± 9 to 78 ± 9%; P < 0.05) and during surgery rScO2 and SmO2 were maintained at the baseline level in most patients. Following anesthesia and tracheal intubation an eventual change in rScO2 correlated to cardiac output and cardiac stroke volume (coefficient of contingence = 0.36; P = 0.0003) rather to a change in mean arterial pressure and for five patients rScO2 was reduced to below 50%. We conclude that (i) increased oxygen delivery enhances tissue oxygenation, (ii) oxygen supports tissue oxygenation but does not prevent a critical reduction in cerebral oxygenation sufficiently, and (iii) an eventual decrease in tissue oxygenation seems related to a reduction in cardiac output rather than to hypotension.
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Frontiers in physiology · Jan 2014
Influence of intranasal and carotid cooling on cerebral temperature balance and oxygenation.
The present study evaluated the influence of intranasal cooling with balloon catheters, increased nasal ventilation, or percutaneous cooling of the carotid arteries on cerebral temperature balance and oxygenation in six healthy male subjects. Aortic arch and internal jugular venous blood temperatures were measured to assess the cerebral heat balance and corresponding paired blood samples were obtained to evaluate cerebral metabolism and oxygenation at rest, following 60 min of intranasal cooling, 5 min of nasal ventilation, and 15 min with carotid cooling. ⋯ Calculated cerebral capillary oxygen tension was 43 ± 3 mmHg at rest and remained unchanged during intranasal and carotid cooling, but decreased to 38 ± 2 mmHg (P < 0.05) following increased nasal ventilation. In conclusion, percutaneous cooling of the carotid arteries and intranasal cooling with balloon catheters are insufficient to influence cerebral oxygenation in normothermic subjects as the cooling rate is only 0.3°C per hour and neither intranasal nor carotid cooling is capable of inducing selective brain cooling.