Monitoring the tissue perfusion during hemorrhagic shock and resuscitation: tissue-to-arterial carbon dioxide partial pressure gradient in a pig model

Background Despite much evidence supporting the monitoring of the divergence of transcutaneous partial pressure of carbon dioxide (tcPCO2) from arterial partial pressure carbon dioxide (artPCO2) as an indicator of the shock status, data are limited on the relationships of the gradient between tcPCO2 and artPCO2 (tc-artPCO2) with the systemic oxygen metabolism and hemodynamic parameters. Our study aimed to test the hypothesis that tc-artPCO2 can detect inadequate tissue perfusion during hemorrhagic shock and resuscitation. Methods This prospective animal study was performed using female pigs at a university-based experimental laboratory. Progressive massive hemorrhagic shock was induced in mechanically ventilated pigs by stepwise blood withdrawal. All animals were then resuscitated by transfusing the stored blood in stages. A transcutaneous monitor was attached to their ears to measure tcPCO2. A pulmonary artery catheter (PAC) and pulse index continuous cardiac output (PiCCO) were used to monitor cardiac output (CO) and several hemodynamic parameters. The relationships of tc-artPCO2 with the study parameters and systemic oxygen delivery (DO2) were analyzed. Results Hemorrhage and blood transfusion precisely impacted hemodynamic and laboratory data as expected. The tc-artPCO2 level markedly increased as CO decreased. There were significant correlations of tc-artPCO2 with DO2 and COs (DO2: r = − 0.83, CO by PAC: r = − 0.79; CO by PiCCO: r = − 0.74; all P < 0.0001). The critical level of oxygen delivery (DO2crit) was 11.72 mL/kg/min according to transcutaneous partial pressure of oxygen (threshold of 30 mmHg). Receiver operating characteristic curve analyses revealed that the value of tc-artPCO2 for discrimination of DO2crit was highest with an area under the curve (AUC) of 0.94, followed by shock index (AUC = 0.78; P < 0.04 vs tc-artPCO2), and lactate (AUC = 0.65; P < 0.001 vs tc-artPCO2). Conclusions Our observations suggest the less-invasive tc-artPCO2 monitoring can sensitively detect inadequate systemic oxygen supply during hemorrhagic shock. Further evaluations are required in different forms of shock in other large animal models and in humans to assess its usefulness, safety, and ability to predict outcomes in critical illnesses.

Revisited Hyperoxia Pathophysiology in the Perioperative Setting: A Narrative Review

The widespread use of high-dose oxygen, to avoid perioperative hypoxemia along with WHO-recommended intraoperative hyperoxia to reduce surgical site infections, is an established clinical practice. However, growing pathophysiological evidence has demonstrated that hyperoxia exerts deleterious effects on many organs, mainly mediated by reactive oxygen species. The purpose of this narrative review was to present the pathophysiology of perioperative hyperoxia on surgical wound healing, on systemic macro and microcirculation, on the lungs, heart, brain, kidneys, gut, coagulation, and infections. We reported here that a high systemic oxygen supply could induce oxidative stress with inflammation, vasoconstriction, impaired microcirculation, activation of hemostasis, acute and chronic lung injury, coronary blood flow disturbances, cerebral ischemia, surgical anastomosis impairment, gut dysbiosis, and altered antibiotics susceptibility. Clinical studies have provided rather conflicting results on the definitions and outcomes of hyperoxic patients, often not speculating on the biological basis of their results, while this review highlighted what happens when supranormal PaO2 values are reached in the surgical setting. Based on the assumptions analyzed in this study, we may suggest that the maintenance of PaO2 within physiological ranges, avoiding unnecessary oxygen administration, may be the basis for good clinical practice.

Evaluation of Optimization of Pulmonary and Systemic Blood Flow in Children after Bidirectional Cavapulmonary Anastomosis

In patients after bidirectional cavapulmonary anastomosis, blood flow through the superior vena cava (SVC), providing effective pulmonary blood flow, is the most important factor influencing blood oxygen saturation. Blood flow through the inferior vena cava recirculates into the systemic bloodstream. The study of the ratio of these flows will provide better understanding of the physiology of blood circulation after anastomosis and determine systemic oxygen saturation of blood and optimal time to perform surgery. The aim. To determine volumetric blood flow in the SVC, calculate pulmonary to systemic blood flow ratio in children after bidirectional cavapulmonary anastomosis, and evaluate its contribution to cardiac output and oxygen saturation in systemic blood flow. Materials and methods. In the period from January 2010 to June 2021, 51 patients with congenital heart defects with depleted pulmonary blood flow underwent hemodynamic correction at the National Amosov Institute of Cardiovascular Surgery of the National Academy of Medical Sciences of Ukraine. There were 29 male patients (57%) and 22 female patients (43%). The mean age of the patients at the time of the surgery was 34 ± 18.2 months (2 to 120 months), the mean age of patients at the time of examination was 43.5 ± 28.4 months (12 to 134 months). The main method of diagnosis in determining the defect and assessing the immediate and long-term results was echocardiographic examination and probing of the heart cavities. To evaluate the optimization of pulmonary/systemic blood flow we used equations obtained using the Fick method. Pulmonary to systemic blood flow ratio was calculated separately for 35 patients. Among the examined 35 patients, 18 children were older than 2.5 years, so all the examined patients were conveniently divided into 2 age groups: I group (n = 17) up to 2.5 years, II group (n = 18) older than 2.5 years to assess the contribution of SVC to the systemic circulation depending on age. Results. Pulmonary to systemic blood flow ratio was calculated for 35 patients Qp/Qs = (82% – 66%) / (97% – 66%) = 0.52. The calculated cardiac index according to echocardiography was 4.0 ± 0.85 L/min/m2 which corresponds to the SVC saturation (r = 0.60, p = <0.001). The flow in the superior vena cava = 2.08 L/min/m2. There was a very interesting trend towards decrease in the average rate of systemic saturation in patients after bidirectional cavapulmonary anastomosis depending on age and duration of surgery. Thus, in 17 patients of group I, the calculated Qp/Qs was (84% – 67%) / (97% – 67%) = 0.57. In patients of group II, the average systemic oxygen saturation was 78 ± 2% (from 65% to 81%). Calculated Qp/Qs for 18 patients of group II = (78% – 66%) / (97% – 66%) = 0.39, which indicates a decrease in pulmonary to systemic ratio with the growth of the child. Decreased systemic saturation after bidirectional cavapulmonary anastomosis in patients with increasing age and body surface area is associated with a decrease in the proportional flow from the superior vena cava. Therefore, in our clinical material, we confirmed the phenomenon of change in pulmonary to systemic ratio depending on age, which was described by Salim et al. according to a study conducted on healthy babies. Conclusions. The contribution of SVC flow to total cardiac output after bidirectional cavapulmonary anastomosis is directly associated with the patient’s age and gradually decreases in older patients, as indicated by a decrease in systemic saturation, so the clinical effect of bidirectional cavapulmonary anastomosis may be significantly better when performing surgery in early childhood.

Parametric Investigation of an Injection-Jet Self-Powered Fontan Circulation

Rationale: Approximately 1/2500 babies are born with only one functioning ventricle and the Fontan is the third and, ideally final staged palliative operation for these patients. This altered circulation is prone to failure with survival rates below 50% into adulthood in some series. Chronically elevated inferior vena cava (IVC) pressure is implicated as one cause of the mortality and morbidity in this population.Objective: An injection jet shunt (IJS) drawing blood-flow directly from the aortic arch to significantly lower IVC pressure is proposed.Methods and Results: A computer-generated 3D model of a 2–4 year old patient with a fenestrated Fontan and a cardiac output of 2.3L/min was generated. The detailed 3D pulsatile hemodynamics are resolved in a zero-dimensional lumped parameter network tightly-coupled to a 3D computational fluid dynamics model accounting for non-Newtonian blood rheology and resolving turbulence using large eddy simulation. IVC pressure and systemic oxygen saturation were tracked for various IJS-assisted Fontan configurations, altering design parameters such as shunt and fenestration diameters and locations.A baseline “failing” Fontan with 4mm fenestration was tuned to elevated IVC pressure (\(+17.8mmHg\)). Enlargement of the fenestration to 8mm resulted in a 3mmHg IVC pressure drop but an unacceptable reduction in systemic oxygen saturation below 80%. Addition of an IJS with a 2mm nozzle and minor volume load to the ventricle improved the IVC pressure drop to 3.2mmHg while increasing systemic oxygen saturation above 80%.Conclusions: The salutary effects of the IJS to effectively lower IVC pressure while retaining acceptable levels of oxygen saturation are successfully demonstrated.

EXPRESS: Efficacy and Safety of Pulmonary Vasodilators in the Patients with Eisenmenger Syndrome: A Meta-analysis of Randomized Controlled Trials

Background: Few meta-analyses evaluated the efficacy and safety of pulmonary vasodilators in patients with Eisenmenger syndrome (ES). Recently, some studies have reported conflicting results regarding improvements in exercise capacity. This study evaluated the efficacy and safety of pulmonary vasodilators in patients with ES. Methods and Results: Relevant studies were identified by searching major databases. Pooled outcomes were used to assess the efficacy and safety of pulmonary vasodilators. In total, 5 studies with 508 patients were included. Meta-analysis indicated that the pulmonary vasodilators reduced the mortality (odd risk (OR) = 0.35; 95% CI, 0.13 to 0.95; P = 0.04), slashed the mean pulmonary artery pressure (mean difference (MD) = -4.35 mmHg; 95% CI, -7.19 to -1.50; P = 0.003), decreased pulmonary vascular resistance index (MD = -480.08 dyn·s·cm-5·m2; 95% CI, -753.51 to -206.64; P = 0.0006), increased the 6-minute walk distance (MD = 28.38 m; 95% CI, 2.99 to 53.77; P = 0.03), and elevated the systemic oxygen saturation at rest (MD = 1.00%; 95% CI, 0.12 to 1.88; P = 0.03). Pulmonary vasodilators were generally well tolerated. Conclusions: Pulmonary vasodilators decrease mortality and improve hemodynamics and exercise capacity in patients with ES. Overall, pulmonary vasodilators are well tolerated

Effects of controlled hypotension with restrictive transfusion on intraoperative blood loss and systemic oxygen metabolism in elderly patients who underwent lumbar fusion

Background The effects of restrictive fluid therapy combined with controlled hypotension in the elderly on systemic oxygen metabolism and renal function are clinical concerns. The aim of this study was to evaluate blood loss, oxygen metabolism, and renal function in different levels of controlled hypotension induced by intravenous nitroglycerin, in combination with limited infusion, in elderly patients undergoing posterior lumbar fusion. Methods A total of 40 patients, aged 60–75 with ASA grade II or III, who were planned for posterior lumbar fusion were randomly allocated into two groups: experimental group [target mean arterial pressure 65 mmHg (MAP 65) or control group (MAP 75)]. Indicators for blood loss, hemodynamic, systemic oxygen metabolism, and renal function evaluation index were recorded before operation (T0), 1 h after induced hypotension (T1), 2 h after hypotension (T2), and in recovery (T3). We compared changes in these parameters between groups to evaluate the combined effects of controlled hypotension with restrictive infusion. Results CI, DO2I, and VO2I were lower in both groups at T1–T3 compared with T0 (p < 0.05). DO2I and VO2I in the MAP 65 group were lower than the MAP 75 group after operation. In both groups, SCysC increased at T1, T2, and T3 (p < 0.05) compared with T0. Conclusions Restrictive transfusion and control MAP at 65 mmHg can slightly change in renal function and reduce the risk of insufficient oxygen supply and importantly have no significant effect on blood loss and postoperative complications. Trial registration ChiCTR-INR-16008153. Registered on 25 March 2016.

Atrial Septal Stenting - A Lifesaving Procedure: First Case Report from Bangladesh

Certain congenital heart defects require the creation of an unrestrictive atrial septal defect (ASD) secundum to achieve adequate atrial mixing to improve systemic oxygen saturation by placing septal stent. We reported a case of 7-month-old child who was presented with shock like state with marked desaturation. He was diagnosed as a case of mixed total anomalous pulmonary venous return with restricted closing ASD secundum. We performed atrial septal stenting as a palliative procedure for saving the life. Creation or enlargement of ASD in infants using nonconventional transcatheter techniques is feasible, safe, and effective when usual technique fails or not suitable. After the procedure systemic saturation improved and patient became hemodynamically stable and there after rerouting of pulmonary veins to left atrium with ASD closure and removal of stent done by open heart surgery and send him home safely. Cardiovasc. j. 2020; 13(1): 86-91