Central venous-to-arterial CO2 difference is a poor tool to predict adverse outcomes after cardiac surgery: a retrospective study.

PURPOSE: The venous-to-arterial carbon dioxide partial pressure difference (CO2 gap) has been reported to be a sensitive indicator of cardiac output adequacy. We aimed to assess whether the CO2 gap can predict postoperative adverse outcomes after cardiac surgery. METHODS: A retrospective study was conducted of 5,151 patients from our departmental database who underwent cardiac surgery from 1 January 2008 to 31 December 2018. Lactate level (mmol·L-1), central venous oxygen saturation (ScVO2) (%), and the venous-to-arterial carbon dioxide difference (CO2 gap) were measured at intensive care unit (ICU) admission and on days 1 and 2 after cardiac surgery. The following postoperative adverse outcomes were collected: ICU mortality, hemopericardium or tamponade, resuscitated cardiac arrest, acute kidney injury, major bleeding, acute hepatic failure, mesenteric ischemia, and pneumonia. The primary outcome was the presence of at least one postoperative adverse outcome. Logistic regression was used to assess the association between ScVO2, lactate, and the CO2 gap with adverse outcomes. Their diagnostic performance was compared using a receiver operating characteristic (ROC) curve. RESULTS: There were 1,933 patients (38%) with an adverse outcome. Cardiopulmonary bypass (CPB) parameters were similar between groups. The CO2 gap was slightly higher for the "adverse outcomes" group than for the "no adverse outcomes" group. Arterial lactate at admission, day 1, and day 2 was also slightly higher in patients with adverse outcomes. Central venous oxygen saturation was not significantly different between patients with and without adverse outcomes. The area under the ROC curve to predict outcomes after CPB for the CO2 gap at admission, day 1, and day 2 were 0.52, 0.55, and 0.53, respectively. CONCLUSION: After cardiac surgery with CPB, the CO2 gap at ICU admission, day 1, and day 2 was associated with postoperative adverse outcomes but showed poor diagnostic performance.

RéSUMé: OBJECTIF: La différence de pression partielle de dioxyde de carbone veineux versus artériel (gradient de CO2) a été rapportée comme étant un indicateur sensible d'un débit cardiaque adéquat. Nous avons tenté d'évaluer si le gradient de CO2 pouvait prédire les devenirs postopératoires défavorables après une chirurgie cardiaque. MéTHODE: Une étude rétrospective a été réalisée en se basant sur les dossiers de 5151 patients issus de notre base de données départementale ayant subi une chirurgie cardiaque entre le 1er janvier 2008 et le 31 décembre 2018. Les taux de lactate (mmol·L−1), la saturation en oxygène veineux central (ScVO2) (%), et la différence de dioxyde de carbone veineux versus artériel (gradient de CO2) ont été mesurés lors de l'admission en réanimation (ICU) et aux jours 1 et 2 après la chirurgie cardiaque. Les complications postopératoires suivantes ont été colligées : mortalité en réanimation, hémopéricarde ou tamponnade, arrêt cardiaque récupéré, insuffisance rénale aiguë, saignements majeurs, insuffisance hépatique aiguë, ischémie mésentérique et pneumonie. Le critère d'évaluation principal était la présence d'au moins une complication postopératoire. La régression logistique a été utilisée pour évaluer l'association entre ScVO2, taux de lactate et gradient de CO2 et les complications. Leur performance diagnostique a été comparée à l'aide d'une courbe ROC (receiver operating characteristic). RéSULTATS: Des complications sont survenues chez 1933 patients (38 %). Les paramètres de circulation extracorporelle (CEC) étaient semblables entre les groupes. Le gradient de CO2 était légèrement plus élevé dans le groupe « complications ¼ que dans le groupe « pas de complication ¼. Les taux de lactate artériels à l'admission, au jour 1 et au jour 2 étaient également légèrement plus élevés chez les patients ayant subi des complications. La différence de saturation en oxygène veineux central n'était pas significative entre les patients avec ou sans complications. L'aire sous la courbe ROC pour prédire les devenirs après la CEC pour le gradient de CO2 à l'admission, au jour 1 et au jour 2 était de 0,52, 0,55 et 0,53, respectivement. CONCLUSION: Après une chirurgie cardiaque avec CEC, le gradient de CO2 à l'admission en réanimation, au jour 1 et au jour 2 était associé aux complications postopératoires, mais sa performance diagnostique était médiocre.

Postoperative Vasoplegic Syndrome Is Associated With Impaired Endothelial Vasomotor Response in Cardiac Surgery: A Prospective, Observational Study.

OBJECTIVES: Vasoplegic syndrome (VS) affects up to 30% of cardiac surgery patients. Onset of VS may be associated with overproduction of nitric oxide (NO). The response of the brachial artery to NO can be assessed using flow-mediated vasodilation (FMD). The aim of this study was to assess brachial artery diameter and FMD response immediately after cardiac surgery. DESIGN: Prospective, observational study. SETTING: Single-center study in a tertiary teaching hospital. PATIENTS: Patients older than 18 years undergoing elective cardiac surgery with cardiopulmonary bypass who provided informed consent. INTERVENTIONS: Brachial artery diameter and FMD response were measured before cardiac surgery and just after surgery on admission to the intensive care unit. Patients were screened for VS for the following 48 hours. RESULTS: Eleven (39%) of the 28 patients included in the study developed VS. Brachial artery diameter and FMD differed between VS and non-VS patients. On intensive care unit admission, mean (± standard deviation) brachial artery diameter was greater in VS patients than in non-VS patients (3.9 ± 0.7 mm v 3.0 ± 0.8 mm, respectively; p = 0.002). Similarly, the FMD response after surgery was greater in VS patients than in non-VS patients (42% ± 8% v 31% ± 1%, respectively; p = 0.014). Brachial artery diameter and FMD response after surgery were both predictive of VS, with an area under the curve (95% confidence interval) of 0.850 (0.705-0.995) (p = 0.002) and 0.755 (0.56-0.95) (p = 0.047), respectively. CONCLUSION: Cardiac surgery with cardiopulmonary bypass appears to alter the NO-mediated endothelial vasomotor response.

Portal Vein Pulsatility as a Dynamic Marker of Venous Congestion Following Cardiac Surgery: An Interventional Study Using Positive End-Expiratory Pressure.

We aimed to assess variations in the portal vein pulsatility index (PI) during mechanical ventilation following cardiac surgery. METHOD: After ethical approval, we conducted a prospective monocentric study at Amiens University Hospital. Patients under mechanical ventilation following cardiac surgery were enrolled. Doppler evaluation of the portal vein (PV) was performed by transthoracic echography. The maximum velocity (VMAX) and minimum velocity (VMIN) of the PV were measured in pulsed Doppler mode. The PI was calculated using the following formula (VMAX - VMIN)/(VMax). A positive end-expiratory pressure (PEEP) incremental trial was performed from 0 to 15 cmH2O, with increments of 5 cmH2O. The PI (%) was assessed at baseline and PEEP 5, 10, and 15 cmH2O. Echocardiographic and hemodynamic parameters were recorded. RESULTS: In total, 144 patients were screened from February 2018 to March 2019 and 29 were enrolled. Central venous pressure significantly increased for each PEEP increment. Stroke volumes were significantly lower after PEEP incrementation, with 52 mL (50-55) at PEEP 0 cmH2O and 30 mL (25-45) at PEEP 15 cmH2O, (p < 0.0001). The PI significantly increased with PEEP incrementation, from 9% (5-15) at PEEP 0 cmH2O to 15% (5-22) at PEEP 5 cmH2O, 34% (23-44) at PEEP 10 cmH2O, and 45% (25-49) at PEEP 15 cmH2O (p < 0.001). CONCLUSION: In the present study, PI appears to be a dynamic marker of the interaction between mechanical ventilation and right heart pressure after cardiac surgery. The PI could be a useful noninvasive tool to monitor venous congestion associated with mechanical ventilation.

Hyperoxia during cardiopulmonary bypass does not decrease cardiovascular complications following cardiac surgery: the CARDIOX randomized clinical trial.

PURPOSE: Data on the benefit or or harmful effects of oxygen level on ischemic reperfusion injuries in cardiac surgery are insufficient. We hypothesized that hyperoxia during cardiopulmonary bypass decreases the incidence of postoperative atrial fibrillation (POAF) and ventricular fibrillation, and therefore decreases cardiovascular morbidity (CARDIOX study). METHODS: An open-label, randomized clinical trial including adults undergoing elective cardiac surgery, i.e. cardiopulmonary bypass (CPB) randomized 1:1 to an intervention group or standard group at two French University Hospitals from June 2016 to October 2018. The intervention consisted in delivering of an inspired fraction of oxygen of one to one during CPB. The standard care consisted in delivering oxygen to achieve a partial arterial blood pressure less than 150 mmHg. The primary endpoint was the occurrence of POAF and/or ventricular tachycardia/ventricular fibrillation (VT/VF) within the 15 days following cardiac surgery. The secondary endpoint was the occurrence of major adverse cardiovascular events (MACCE: in-hospital mortality, stroke, cardiac arrest, acute kidney injury, and mesenteric ischemia). RESULTS: 330 patients were randomly assigned to either the intervention group (n = 161) or the standard group (n = 163). Mean PaO2 was 447 ± 98 mmHg and 161 ± 60 mmHg during CPB, for the intervention and standard group (p < 0.0001) respectively. The incidence of POAF or VT/VF were similar in the intervention group and the standard group (30% [49 of 161 patients] and 30% [49 of 163 patients], absolute risk reduction 0.4%; 95% CI, - 9.6-10.4; p = 0.94). MACCE was similar between groups with, an occurrence of 24% and 21% for the intervention group and the standard groups (absolute risk reduction 3.4%; 95% CI, - 5.7-12.5; p = 0.47) respectively. After adjustment, the primary and secondary endpoints remained similar for both groups. CONCLUSION: Hyperoxia did not decrease POAF and cardiovascular morbidity following cardiac surgery with CPB. CLINICALTRIAL. GOV IDENTIFIER: NCT02819739.

Physical work capacity in older adults: implications for the aging worker.

BACKGROUND: In many developed countries, the workforce is rapidly aging. Occupational demands however, have not decreased despite the fact that workers see a decline in physical work capacity with age. The purpose of this review is to examine the physiological adaptations to aging, the impact of aging on performance and the benefits of physical fitness in improving functional work capacity in aging individuals. METHODS: An extensive search of the scientific literature was performed, acquiring published articles which examined the physiological changes associated with age-related decrements in the physical work capacity of healthy aging adults. The databases accessed included AARP Ageline, AccessScience, Annual Reviews, CISTI, Cochrane Library, Clinical Evidence, Digital Dissertations (Proquest), Embase, HealthSTAR, Medline, PubMed, Scopus, and PASCAL and included relevant information sites obtained on the world wide web. RESULTS: While a great deal of variation exists, an average decline of 20% in physical work capacity has been reported between the ages of 40 and 60 years, due to decreases in aerobic and musculoskeletal capacity. These declines can contribute to decreased work capacity, and consequential increases in work-related injuries and illness. However, differences in habitual physical activity will greatly influence the variability seen in individual physical work capacity and its components. Well-organized, management-supported, work-site health interventions encouraging physical activity during work hours could potentially decrease the incidence of age-related injury and illness. CONCLUSIONS: Age-associated functional declines and the accompanying risk of work-related injury can be prevented or at least delayed by the practice of regular physical activity. Older workers could optimally pursue their careers until retirement if they continuously maintain their physical training.

Controlling methicillin resistant Staphyloccocus aureus and Pseudomonas aeruginosa wound infections with a novel biomaterial.

Wound infections, especially those associated with methicillin-resistant Staphylococcus aureus and Pseudomonas aeruginosa, offer considerable challenges for clinicians. Our laboratory has recently developed novel composite biomaterials (DRDC) for wound dressing applications, and demonstrated their in vitro bactericidal efficacy. In the present study, we assessed the proliferation of planktonic and sessile Pseudomonas aeruginosa and methicillin-resistant Staphylococcus aureus in porcine full-thickness wounds covered for up to 48 h with either saline- or mafenide acetate-loaded DRDC puffs and meshes. All biomaterials were applied 4 h following bacterial inoculation of the wounds with methicillin-resistant Staphylococcus aureus and Pseudomonas aeruginosa, to allow colonization of the tissues and initiation of biofilm formation. The drug-loaded biomaterials eradicated both the planktonic and biofilm bacteria in the wounds within 24 h (p <. 05), irrespective of the bacterial strain or architecture of the dressing. While the wound bioburdens increased in the ensuing 24 h, they remained approximately 2 log(10) colony-forming units (CFU) below (p <. 05) their respective baseline values. Similarly, less than 4 log(10) CFU was recovered in the drug-loaded DRDC biomaterials throughout the study. These data show that the DRDC puffs and meshes are effective in delivering certain medications, such as antimicrobial agents, to the wound bed, suggesting considerable value of this material for treating wounds, especially those with irregular shapes, contours, and depths.

Evaluation of a bi-layer wound dressing for burn care I. Cooling and wound healing properties.

Severe burns remain a significant cause of morbidity and mortality despite the availability of numerous therapies. We assessed the wound healing and skin-cooling properties of a DRDC hydrogel/polyurethane wound dressing using different pre-clinical models. Our results show that 85% of partial-thickness, non-contaminated porcine wounds treated with our dressing healed within 6 days. In contrast, 85% of the wounds treated with commercial dressings healed within 8 days. Application of a moist DRDC dressing (to simulate a condition of exudate absorption) on a scald burn covering 25% of the dorsal area in rats reduced skin temperature by 1.70 +/- 0.14 degrees C for 5 min, the skin temperature being comparable to that of control burned rats after 20 min. The application of a moist DRDC dressing did not induce significant differences in body temperatures compared with that of burned animals without dressing coverage throughout the 90-min experiment. While no change in body temperatures were observed when standard dressings (i.e., not pre-moistened) were applied, skin temperature increased gradually. These data show that our dressing is effective in promoting faster healing of the treated wound; and providing a transient, but beneficial cooling effect to the skin contact-site, without the adverse effect of inducing whole-body hypothermia.

In vitro bactericidal efficacy of a new sun- and heat burn gel.

We assessed the in vitro bactericidal efficacy of a new sunburn gel (Rescudermtrade mark; RESC) against planktonic and sessile Pseudomonas aeruginosa (PSEUD) and Staphylococcus epidermidis (STAPH). While PSEUD levels were 4log(10) lower than those of STAPH within 24h of adding RESC to contaminated nutrient broths, all bacterial counts were comparable by 48h. PSEUD and STAPH levels were then measured after applying either a single or three consecutive aliquots of RESC to polyurethane sponges. Gel was removed after 5 or 20min, or left on for 72h. Bacterial counts in placebo-treated sponges had plateaued by 24h to values above 9log(10)CFU/mL. In contrast, six out of seven of the RESC application modalities reduced bacterial levels below 4log(10)CFU/mL for 72h. RESC remained effective against STAPH despite up to a 24h treatment delay, irrespective of the number of applications. Repeated RESC applications were required to maintain PSEUD below 4log(10)CFU/mL when the delay exceeded 7h. These data demonstrate the differential susceptibility of planktonic and sessile bacteria to RescuDermtrade mark. This product might be a good candidate for reducing the opportunity for wound infection, especially in burns.

Evaluation of a bi-layer wound dressing for burn care. II. In vitro and in vivo bactericidal properties.

We have recently designed a medicated bi-layer wound dressing to address the key requirements for treating external, contaminated war wounds. This study assessed the in vitro and in vivo bactericidal efficacies of the DRDC hydrogel/polyurethane wound dressing. Chloramphenicol- and chlorhexidine-loaded DRDC dressings produced significantly larger zones of inhibition against Pseudomonas aeruginosa than the other medicated dressings for 4 d. Chlorhexidine-loaded Allevyn and Hydrasorb remained bactericidal for 48 h only. Chloramphenicol-loaded Hydrasorb and Allevyn remained bactericidal for 1 and 3 d, respectively. Ps. aeruginosa and Staphylococcus epidermidis counts in wounds treated with chlorhexidine- and chloramphenicol-loaded DRDC dressings for 24 h were 1-3-log lower than those of control wounds. While Ps. aeruginosa counts in the wounds on day 4 were comparable following daily changes of either antiseptic-loaded dressings, chlorhexidine showed a 75% greater bactericidal efficacy against Staph. epidermidis than chloramphenicol. Though increasing the frequency of dressing changes led to a greater reduction in the wound bacterial load, the contamination levels of all antiseptic-treated wounds remained below 10(5) CFU/g of wound. Cerium nitrate-loaded dressings did not exert any bactericidal effect, irrespective of the experimental conditions. These data show that the DRDC dressing is effective in delivering medications, such as an antimicrobial agent, to the wound bed.

A Chronic Arterial Cannula for Blood Sampling in Conscious, Unrestrained Rats.

We require repeated blood samples for at least 10 days from conscious, unrestrained rats in our studies investigating the inflammatory response to intra-abdominal infection. Furthermore, we require a means by which other experimental devices (implanted concurrently) can be kept out of reach of the animals for the duration of the study. Under these conditions, previously reported postoperative restraint and cannulation techniques did not allow cannula patency for longer than a few days. We designed a cannula that is constructed from microbore tubing, attached to a modified winged infusion catheter, and sutured over the scapulae of the animal. Our device features a curved, perforated tip to allow its easy insertion into the thoracic aorta via the left carotid artery, and it provides an attachment site for a small, lightweight backpack. This cannula has a small dead-space and accommodates repeated arterial blood sampling for at least 10 days without leading to bacteremia or significant alterations in hematological or immune parameters. With minor modifications, this cannula has potential application in the chronic cannulation of other vessels and ducts in other small animals.

Hydrogel-elastomer composite biomaterials: 4. Experimental optimization of hydrogel-elastomer composite fibers for use as a wound dressing.

We report a novel 3-D cavity wound dressing based on a hydrogel-elastomer Interpenetrating Polymer Network (IPN) fabricated into an open-mesh architecture. IPN fibers used to form the dressing were produced by a wet spinning method and optimized in two steps. A factorial experiment was first conducted to identify key parameters that controlled fiber properties. We observed that gelatin wt% played a major role in determining fiber yield, swelling, strength and stability. Other contributing factors included coagulation solution composition, gelatin type, and pre- and post-UV irradiation time. The key factors were then further evaluated individually to achieve a condition that provided a combination of good swelling, mechanical properties and stability. The concentration of the gelatin/HydroThane extrusion solution significantly affected fiber formation and properties, presumably due to the changes in solution viscosity. The effects of pre-UV irradiation were also ascribed to its impact on the solution viscosity and became negligible at higher concentrations when viscosity is mainly controlled by concentration. The composition of the coagulation bath influenced the fiber swelling and wet stress. These results, taken together with our previous studies, suggest that our biomaterial would provide a combination of mechanical and swelling properties suitable for wound dressing applications.

Hydrogel-elastomer composite biomaterials: 3. Effects of gelatin molecular weight and type on the preparation and physical properties of interpenetrating polymer networks.

To optimize the preparation of a gelatin-HydroThane Interpenetrating Polymer Network (IPN) and obtain optimum physical properties for its use as a wound dressing, we studied IPN films prepared with two types of gelatin having different molecular weights. The effects of the gelatin molecular weight and type on the IPN film's structure, morphology, swelling and mechanical properties were determined. While FTIR did not reveal any noticeable differences between the IPNs prepared using different gelatin, light microscopy showed a lesser phase separation of the film prepared with a high-molecular-weight type A gelatin. Furthermore, these films displayed slightly less swelling, higher strength and lower strain, compared to the IPNs prepared with either low-molecular-weight type A or type B gelatin. The IPN prepared with type B gelatin showed higher swelling in serum-containing medium than those prepared with type A gelatin, because of its ionic charges under the condition. Increases in viscosity were observed with increasing molecular weight, type A being more viscous than type B gelatin despite having a lower bloom number. The viscosity of the high-molecular-weight gelatin was in the same magnitude as that of HydroThane, which might lead to less phase separation. A better understanding of the effects of alterations in the gelatin molecular weight and type on the formation and properties of the gelatin-HydroThane IPN should facilitate the development of promising composite biomaterials for wound dressing applications.

Hydrogel-elastomer composite biomaterials: 1. Preparation of interpenetrating polymer networks and in vitro characterization of swelling stability and mechanical properties.

We prepared interpenetrating polymer networks (IPNs) composed of a gelatin hydrogel and a HydroThane elastomer to combine the advantages of both polymers into one biomaterial. Fourier transform Infrared (FTIR) spectroscopy and Differential Scanning Calorimetry (DSC) confirmed the co-existence of the two polymers in the IPNs. Optical light microscopy confirmed hydrogel domains were interspaced into an elastomer network. Hydration and stability studies in aqueous solution showed that, although the IPN biomaterials exhibited stable swelling for more than 30 days, approximately 10% and 50% loss of the hydrogel component were confirmed at room temperature and 37 degrees C, respectively, using gel permeation chromatography (GPC). The swelling study in the serum-containing medium indicated the biomaterials maintained their swelling stability for different periods, depending on the extent of gelatin methacrylation, photoinitiator concentration and incubation temperature. Lastly, the biomaterials exhibited higher failure stress and lower failure strain in a dry state than in a swollen state, and showed limited changes in both stress and strain at room temperature and at 37 degrees C, in contrast with a decrease at 50 degrees C. No significant effects of gelatin methacrylation on mechanical properties were noticed. The preparation and characterization methods were well established and formed the basis of further developing the biomaterials.

Hydrogel-elastomer composite biomaterials: 2. Effects of aging methacrylated gelatin solutions on the preparation and physical properties of interpenetrating polymer networks.

This study was conducted to understand the effects of aging methacrylated gelatin solutions on the properties of gelatin-HydroThane Interpenetrating Polymer Network (IPN) films. The latter were prepared from methacrylated gelatin solutions that were either freshly made or stored at different concentrations and temperatures for various periods. The morphology, swelling stability and mechanical properties of the IPNs were then accordingly characterized. The IPNs prepared with aged solutions showed a reduced phase separation; changed from a network-like structure to a continuous phase structure; and demonstrated higher swelling stabilities and higher elasticity under optimal aging conditions, compared to the IPN prepared with a fresh methacrylated gelatin solution. An increase in viscosity and a change in phase transition of aged methacrylated gelatin solutions were also observed, presumably due to the physical structuring of methacrylated gelatin chains (e.g., by the formation of a helix structure), thus altering the resulting IPN characteristics. A better understanding of the effects of aging methacrylated gelatin solution on the formation and properties of gelatin-HydroThane IPNs should enable us to further develop our composite biomaterials for different dressing applications.