Ratio of Mixed Venous Oxygen Saturation-to-Pulmonary Capillary Wedge Pressure: Insights From the Veterans Affairs Clinical Assessment, Reporting, and Tracking Program

Background: Hemodynamic values from right heart catheterization aid diagnosis and clinical decision-making but may not predict outcomes. Mixed venous oxygen saturation percentage and pulmonary capillary wedge pressure relate to cardiac output and congestion, respectively. We theorized that a novel, simple ratio of these measurements could estimate cardiovascular prognosis. Methods: We queried Veterans Affairs’ databases for clinical, hemodynamic, and outcome data. Using the index right heart catheterization between 2010 and 2016, we calculated the ratio of mixed venous oxygen saturation-to-pulmonary capillary wedge pressure, termed ratio of saturation-to-wedge (RSW). The primary outcome was time to all-cause mortality; secondary outcome was 1-year urgent heart failure presentation. Patients were stratified into quartiles of RSW, Fick cardiac index (CI), thermodilution CI, and pulmonary capillary wedge pressure alone. Kaplan-Meier curves and Cox proportional hazards models related comparators with outcomes. Results: Of 12 019 patients meeting inclusion criteria, 9826 had values to calculate RSW (median 4.00, interquartile range, 2.67–6.05). Kaplan-Meier curves showed early, sustained separation by RSW strata. Cox modeling estimated that increasing RSW by 50% decreases mortality hazard by 19% (estimated hazard ratio, 0.81 [95% CI, 0.79–0.83], P <0.001) and secondary outcome hazard by 28% (hazard ratio, 0.72 [95% CI, 0.70–0.74], P <0.001). Among the 3793 patients with data for all comparators, Cox models showed RSW best associated with outcomes (by both C statistics and Bayes factors). Furthermore, pulmonary capillary wedge pressure was superior to thermodilution CI and Fick CI. Multivariable adjustment attenuated without eliminating the association of RSW with outcomes. Conclusions: In a large national database, RSW was superior to conventional right heart catheterization indices at assessing risk of mortality and urgent heart failure presentation. This simple calculation with routine data may contribute to clinical decision-making in this population.

MRI evaluation of cerebral metabolic rate of oxygen (CMRO2) in obstructive sleep apnea

Patients with obstructive sleep apnea (OSA) are at elevated risk of developing systemic vascular disease and cognitive dysfunction. Here, cerebral oxygen metabolism was assessed in patients with OSA by means of a magnetic resonance-based method involving simultaneous measurements of cerebral blood flow rate and venous oxygen saturation in the superior sagittal sinus for a period of 10 minutes at an effective temporal resolution of 1.3 seconds before, during, and after repeated 24-second breath-holds mimicking spontaneous apneas, yielding, along with pulse oximetry-derived arterial saturation, whole-brain CMRO2 via Fick’s Principle. Enrolled subjects were classified based on their apnea-hypopnea indices into OSA (N = 31) and non-sleep apnea reference subjects (NSA = 21), and further compared with young healthy subjects (YH, N = 10). OSA and NSA subjects were matched for age and body mass index. CMRO2 was lower in OSA than in the YH group during normal breathing (105.6 ± 14.1 versus 123.7 ± 22.8 μmol O2/min/100g, P = 0.01). Further, the fractional change in CMRO2 in response to a breath-hold challenge was larger in OSA than in the YH group (15.2 ± 9.2 versus 8.5 ± 3.4%, P = 0.04). However, there was no significant difference in CMRO2 between OSA and NSA subjects. The data suggest altered brain oxygen metabolism in OSA and possibly in NSA as well.

CONTROL OF INTRAOPERATIVE SHIVERING UNDER SPINAL ANAESTHESIA- A PROSPECTIVE RANDOMIZED COMPARATIVE STUDY OF NALBUPHINE WITH TRAMADOL

spinal anesthesia is a widely used technique for both elective and emergency surgeries. Shivering is one of the most commonly recognized complications of the central neuraxial blockade because of impairment of thermoregulatory control, reported in 40%-70% of the patients undergoing surgery under spinal anaesthesia. Post-anesthetic shivering is defined as an involuntary,spontaneous,rhythmic oscillating muscle hyperactivity that increases metabolic heat production up to 600% after anesthesia. Shivering during neuraxial anesthesia is a common issue that could have possibly adverse impacts, for example, increased oxygen consumption, carbon dioxide production, lung ventilation and cardiac work, as well as causing diminished mixed venous oxygen saturation. Spinal anesthesia impedes the thermoregulatory system by restraining tonic vasoconstriction which assumes significant role in the regulation of temperature

Decoding the Onset of Intraoperative Normal Pressure Perfusion Breakthrough with Near-Infrared Spectroscopy and Jugular Venous Oxygen Saturation Catheter in a Case of Arteriovenous Malformation Surgery

Multimodal monitoring can be a useful tool to design an appropriate anesthesia technique in the intraoperative period during the surgical excision of an intracerebral arteriovenous malformation (AVM). Intraoperatively, hyperperfusion syndrome can be attributed to causes like insufficient blood pressure control, occlusion of venous drainage before complete resection of arterial feeders, or inadequate hemostatic control of distended capillaries receiving arterial flow. We would like to highlight the potential role of near-infrared spectroscopy and jugular venous oxygen saturation catheter in detection of intraoperative normal perfusion pressure breakthrough and take necessary measures to prevent further insult with the help of this case report.

Intraoperative hyperglycemic stress response and tissue perfusion in cardiac surgery

Background and aim of the study Approximately 30% of patients undergoing cardiac surgery have a history of diabetes and 60-80% of patients without diabetes have stress hyperglycemia. We examined patients undergoing cardiac surgery to determine the presence of stress hyperglycemia and its relationship to tissue perfusion. Methods Hemodynamic parameters, central venous oxygen saturation, lactate,oxygen delivery and consumption, oxygen extraction rate were analyzed at four intraoperative time points. Results The stress-induced hyperglycemic response during cardiac surgery was more severe in patients without diabetes. When focusing on the oxygen extraction rate in terms of tissue oxygenation, diabetic patients had 1.22 times higher and significant oxygen extraction rate than non-diabetic patients. Conclusions Although lactate values were slightly higher and central venous oxygen saturation were slightly lower in the diabetic group, considering the fact that oxygen extraction rate reflects the total outcome of small changes in all these parameters, we can emphasize the conclusion that diabetic patients undergoing cardiac surgery have greater tissue oxygen demand/supply imbalance compared to non-diabetic patients. In our study, this tissue oxygenation defect in diabetic patients was not found to be directly correlated with blood glucose levels. Perhaps, even if the disease is under control, the negative effects of diabetes on all systems have accumulated and led to such a result.

Non-invasive capnodynamic mixed venous oxygen saturation during major changes in oxygen delivery

Mixed venous oxygen saturation (SvO2) is an important variable in anesthesia and intensive care but currently requires pulmonary artery catheterization. Recently, non-invasive determination of SvO2 (Capno-SvO2) using capnodynamics has shown good agreement against CO-oximetry in an animal model of modest hemodynamic changes. The purpose of the current study was to validate Capno-SvO2 against CO-oximetry during major alterations in oxygen delivery. Furthermore, evaluating fiberoptic SvO2 for its response to the same challenges. Eleven mechanically ventilated pigs were exposed to oxygen delivery changes: increased inhaled oxygen concentration, hemorrhage, crystalloid and blood transfusion, preload reduction and dobutamine infusion. Capno-SvO2 and fiberoptic SvO2 recordings were made in parallel with CO-oximetry. Respiratory quotient, needed for capnodynamic SvO2, was measured by analysis of mixed expired gases. Agreement of absolute values between CO-oximetry and Capno-SvO2 and fiberoptic SvO2 respectively, was assessed using Bland–Altman plots. Ability of Capno- SvO2 and fiberoptic SvO2 to detect change compared to CO-oximetry was assessed using concordance analysis. The interventions caused significant hemodynamic variations. Bias between Capno-SvO2 and CO-oximetry was + 3% points (95% limits of agreements – 7 to + 13). Bias between fiberoptic SvO2 and CO-oximetry was + 1% point, (95% limits of agreements − 7 to + 9). Concordance rate for Capno-SvO2 and fiberoptic SvO2 vs. CO-oximetry was 98% and 93%, respectively. Capno-SvO2 generates absolute values close to CO-oximetry. The performance of Capno-SvO2 vs. CO-oximetry was comparable to the performance of fiberoptic SvO2 vs. CO-oximetry. Capno-SvO2 appears to be a promising tool for non-invasive SvO2 monitoring.

Changes in central venous-to-arterial carbon dioxide tension induced by fluid bolus in critically ill patients

Background In this prospective observational study, we evaluated the effects of fluid bolus (FB) on venous-to-arterial carbon dioxide tension (PvaCO2) in 42 adult critically ill patients with pre-infusion PvaCO2 > 6 mmHg. Results FB caused a decrease in PvaCO2, from 8.7 [7.6−10.9] mmHg to 6.9 [5.8−8.6] mmHg (p < 0.01). PvaCO2 decreased independently of pre-infusion cardiac index and PvaCO2 changes during FB were not correlated with changes in central venous oxygen saturation (ScvO2) whatever pre-infusion CI. Pre-infusion levels of PvaCO2 were inversely correlated with decreases in PvaCO2 during FB and a pre-infusion PvaCO2 value < 7.7 mmHg could exclude a decrease in PvaCO2 during FB (AUC: 0.79, 95%CI 0.64–0.93; Sensitivity, 91%; Specificity, 55%; p < 0.01). Conclusions Fluid bolus decreased abnormal PvaCO2 levels independently of pre-infusion CI. Low baseline PvaCO2 values suggest that a positive response to FB is unlikely.