Continuous transcutaneous monitoring of peripheral oxygen and carbon dioxide during infant cardiac surgery

Close monitoring of the balance between oxygen demand and supply is of great importance during cardiac cardiopulmonary bypass (CPB) surgery. This study was to compare conventional intermittent venous blood gas monitoring with continuous transcutaneous oxygen and carbon dioxide monitoring in infant patients undergoing cardiac surgery with CPB. According to paired data from 29 infant patients undergoing cardiac surgery we found that a positive correlation existed between the two techniques, with a correlation coefficient 0.9021 and 0.8021 for PO2 and PCO2 respectively. It’s concluded that transcutaneous monitoring and intermittent venous blood sampling had good correlation and transcutaneous monitoring may be used conveniently and safely clinically during CPB.

Does the advantage of transcutaneous oximetry measurements in diabetic foot ulcer apply equally to free flap reconstruction?

BACKGROUND Transcutaneous oxygen pressure(TcpO2)is a precise method for determining oxygen perfusion in wounded tissues.The device uses either electrochemical or optical sensors.AIM To evaluate the usefulness of TcpO2 measurements on free flaps(FFs)in diabetic foot ulcers(DFUs).METHODS TcpO2 was measured in 17 patients with DFUs who underwent anterolateral thigh(ALT)-FF surgery and compared with 30 patients with DFU without FF surgery.RESULTS Significant differences were observed in the ankle-brachial index;duration of diabetes;and haemoglobin,creatinine,and C-reactive protein levels between the two groups.TcpO2 values were similar between two groups except on postoperative days 30 and 60 when the values in the ALT-FF group remained<30 mmHg and did not increase>50 mmHg.CONCLUSION Even if the flap is clinically stable,sympathectomy due to adventitia stripping during anastomosis and arteriovenous shunt progression due to diabetic polyneuropathy could lead to low TcpO2 values in the ALT-FF owing to its thick fat tissues,which is supported by the slow recovery of the sympathetic tone following FF.Therefore,TcpO2 measurements in patients with DFU who underwent FF reconstruction may be less accurate than in those who did not.

Carbon dioxide accumulation during analgosedated colonoscopy: Comparison of propofol and midazolam

AIM: To characterize the profiles of alveolar hypoventilation during colonoscopies performed under sedoanalgesia with a combination of alfentanil and either midazolam or propofol. METHODS: Consecutive patients undergoing routine colonoscopy were randomly assigned to sedation with either propofol or midazolam in an open-labeled design using a titration scheme. All patients received 4 μg/kg per body weight alfentanil for analgesia and 3 L of supplemental oxygen. Oxygen saturation (SpO 2 ) was measured by pulse oximetry (POX), and capnography (PcCO 2 ) was continuously measured using a combined dedicated sensor at the ear lobe. Instances of apnea resulting in measures such as stimulation of the patient, a chin lift, a mask maneuver, or withholding of sedation were recorded. PcCO 2 values (as a parameter of sedation-induced hypoventilation) were compared between groups at the following distinct time points: baseline, maximal rise, termination of the procedure and 5 min after termination of the procedure. The number of patients in both study groups who regained baseline PcCO 2 values (± 1.5 mmHg) five minutes after the procedure was determined.RESULTS: A total of 97 patients entered this study. The data from 14 patients were subsequently excluded for clinical procedure-related reasons or for technical problems. Therefore, 83 patients (mean age 62 ± 13 years) were successfully randomized to receive propofol (n = 42) or midazolam (n = 41) for sedation. Most of the patients were classified as American Society of Anesthesiologists (ASA) Ⅱ [16 (38%) in the midazolam group and 15 (32%) in the propofol group] and ASA Ⅲ [14 (33%) and 13 (32%) in the midazolam and propofol groups, respectively]. A mean dose of 5 (4-7) mg of Ⅳ midazolam and 131 (70-260) mg of Ⅳ propofol was used during the procedure in the corresponding study arms. The mean SpO 2 at baseline (%) was 99 ± 1 for the midazolam group and 99 ± 1 for the propofol group. No cases of hypoxemia (SpO 2 < 85%) or apnea were recorded. However, an increase in PcCO 2 that indicated alveolar hypoventilation occurred in both groups after administration of the first drug and was not detected with pulse oximetry alone. The mean interval between the initiation of sedation and the time when the PcCO 2 value increased to more than 2 mmHg was 2.8 ± 1.3 min for midazolam and 2.8 ± 1.1 min for propofol. The mean maximal rise was similar for both drugs: 8.6 ± 3.7 mmHg for midazolam and 7.4 ± 3.2 mmHg for propofol. Five minutes after the end of the procedure, the mean difference from the baseline values was significantly lower for the propofol treatment compared with midazolam (0.9 ± 3.0 mmHg vs 4.3 ± 3.7 mmHg, P = 0.0000169), and significantly more patients in the propofol group had regained their baseline value ± 1.5 mmHg (32 of 41vs 12 of 42,P = 0.0004). CONCLUSION: A significantly higher number of patients sedated with propofol had normalized PcCO 2 values five minutes after sedation when compared with patients sedated with midazolam.

Effect of mild hypothermia on partial pressure of oxygen in brain tissue and brain temperature in patients with severe head injury

Objective: To study the changes of partial pressure of oxygen in brain tissue ( P btO 2) and brain temperature (BT) in patients in acute phase of severe head injury, and to study the effect of mild hypothermia on P btO 2 and BT. Methods: The P btO 2 and the BT of 18 patients with severe head injury were monitored, and the patients were treated with mild hypothermia within 20 hours after injury. The rectal temperature (RT) of the patients was kept on 31.5- 34.9℃ for 1-7 days ( 57.7 hours± 28.4 hours averagely), simultaneously, the indexes of P btO 2 and BT were monitored for 1-5 days (with an average of 54.8 hours± 27.0 hours). According to Glasgow Outcome Scale (GOS), the prognosis of the patients was evaluated at 6 months after injury. Results: Within 24 hours after severe head injury, the P btO 2 was significantly lower ( 9.6 mm Hg± 6.8 mm Hg, 1 mm Hg= 0.133 kPa) than the normal value (16-40 mm Hg). After treatment of mild hypothermia, the mean P btO 2 increased to 28.7 mm Hg± 8.8 mm Hg during the first 24 hours, and the P btO 2 was still maintained within the range of normal value at 3 days after injury. The BT was higher than the RT in the patients in acute phase of severe head injury, and the difference between the BT and the RT significantly increased after treatment of mild hypothermia. Hyperventilation (the partial pressure of carbon dioxide in artery (P aCO 2)≈25 mm Hg) decreased the high intracranial pressure (ICP) and significantly decreased the P btO 2. Conclusions: This study demonstrates that P ptO 2 and BT monitoring is a safe, reliable and sensitive diagnostic method to follow cerebral oxygenation. It might become an important tool in our treatment regime for patients in the acute phase of severe head injury requiring hypothermia and hyperventilation.

Effect of hyperventilation on brain tissue oxygen pressure, carbon dioxide pressure, pH value and intracranial pressure during intracranial hypertension in pigs

To study the effect of hyperventilation on brain tissue oxygen pressure (P ti O 2) , brain tissue carbon dioxide pressure (P ti CO 2) , pH value and intracranial pressure (ICP) during intracranial hypertension in pigs. Methods: Autologous arterial blood ( 5.5 ml± 0.5 ml) was injected into the left frontal lobe by micropump to establish the model of intracerebral hematoma in pigs. After blood injection, the animals were hyperventilated for 15 minutes to decrease the pressure of carbon dioxide in arterial blood ( P aCO 2 ) to 27.35 mm*!Hg ± 11.97 mm*!Hg (1 mm*!Hg= 0.133 kPa). The mean arterial pressure (MAP), intracranial pressure (ICP), cerebral perfusion pressure (CPP), P ti O 2 , P ti CO 2 , pH value and [HCO 3 -] were continuously monitored and the blood gas was analyzed. Results: After hyperventilation, the ICP significantly decreased (P< 0.01 ), the CPP significantly increased (P< 0.05 ), while the P ti O 2 greatly decreased to the ischemic level ( 8.20 mm*!Hg± 2.50 mm*!Hg) (P< 0.01 ), the P ti CO 2 decreased (P< 0.01 ) and the pH value increased (P< 0.01 ). At the same time, blood gas analysis showed that the P aCO 2 greatly decreased and the pH value increased. Conclusions: Hyperventilation can decrease the ICP and the P ti O 2 significantly. Therefore, hyperventilation should be avoided early after brain injury. The P ti O 2 monitoring will be helpful for detecting cerebral ischemia early.