The exercise pressor reflex - a pressure-raising mechanism with a limited role in regulating leg perfusion during locomotion in young healthy men.

We investigated the role of the exercise pressor reflex (EPR) in regulating the haemodynamic response to locomotor exercise. Eight healthy participants (23 ± 3 years, V ̇ O 2 max ${\dot V_{{{\mathrm{O}}_{\mathrm{2}}}{\mathrm{max}}}}$ : 49 ± 6 ml/kg/min) performed constant-load cycling exercise (∼36/43/52/98% V ̇ O 2 max ${\dot V_{{{\mathrm{O}}_{\mathrm{2}}}{\mathrm{max}}}}$ ; 4 min each) without (CTRL) and with (FENT) lumbar intrathecal fentanyl attenuating group III/IV locomotor muscle afferent feedback and, thus, the EPR. To avoid different respiratory muscle metaboreflex and arterial chemoreflex activation during FENT, subjects mimicked the ventilatory response recorded during CTRL. Arterial and leg perfusion pressure (femoral arterial and venous catheters), femoral blood flow (Doppler-ultrasound), microvascular quadriceps blood flow index (indocyanine green), cardiac output (inert gas breathing), and systemic and leg vascular conductance were quantified during exercise. There were no cardiovascular and ventilatory differences between conditions at rest. Pulmonary ventilation, arterial blood gases and oxyhaemoglobin saturation were not different during exercise. Furthermore, cardiac output (-2% to -12%), arterial pressure (-7% to -15%) and leg perfusion pressure (-8% to -22%) were lower, and systemic (up to 16%) and leg (up to 27%) vascular conductance were higher during FENT compared to CTRL. Leg blood flow, microvascular quadriceps blood flow index, and leg O2 -transport and utilization were not different between conditions (P > 0.5). These findings reflect a critical role of the EPR in the autonomic control of the heart, vasculature and, ultimately, arterial pressure during locomotor exercise. However, the lack of a net effect of the EPR on leg blood flow challenges the idea of this cardiovascular reflex as a key determinant of leg O2 -transport during locomotor exercise in healthy, young individuals. KEY POINTS: The role of the exercise pressor reflex (EPR) in regulating leg O2 -transport during human locomotion remains uncertain. We investigated the influence of the EPR on the cardiovascular response to cycling exercise. Lumbar intrathecal fentanyl was used to block group III/IV leg muscle afferents and debilitate the EPR at intensities ranging from 30% to 100% V ̇ O 2 max ${\dot V_{{{\mathrm{O}}_{\mathrm{2}}}{\mathrm{max}}}}$ . To avoid different respiratory muscle metaboreflex and arterial chemoreflex activation during exercise with blocked leg muscle afferents, subjects mimicked the ventilatory response recorded during control exercise. Afferent blockade increased leg and systemic vascular conductance, but reduced cardiac output and arterial-pressure, with no net effect on leg blood flow. The EPR influenced the cardiovascular response to cycling exercise by contributing to the autonomic control of the heart and vasculature, but did not affect leg blood flow. These findings challenge the idea of the EPR as a key determinant of leg O2 -transport during locomotor exercise in healthy, young individuals.

On the haemodynamic consequence of the chemoreflex and muscle mechanoreflex interaction in women and men: two tales, one story.

The cardiovascular response resulting from the individual activation of the muscle mechanoreflex (MMR) or the chemoreflex (CR) is different between men and women. Whether the haemodynamic consequence resulting from the interaction of these sympathoexcitatory reflexes is also sex-dependent remains unknown. MMR and CR were activated by passive leg movement (LM) and exposure to hypoxia (O2 -CR) or hypercapnia (CO2 -CR), respectively. Twelve young men and 12 young women completed two experimental protocols: (1) resting in normoxia (PET O2 : ∼83 mmHg, PET CO2 : ∼34 mmHg), normocapnic hypoxia (PET O2 : ∼48 mmHg, PET CO2 : ∼34 mmHg) and hyperoxic hypercapnia (PET O2 : ∼524 mmHg, PET CO2 : ∼44 mmHg); (2) LM under the same gas conditions. During the MMR:O2 -CR coactivation, in men, the observed mean arterial pressure (MAP) and cardiac output (CO) were not different (additive effect), while the observed leg blood flow (LBF) and vascular conductance (LVC) were significantly lower (hypo-additive), compared with the sum of the responses elicited by each reflex alone. In women, the observed MAP was not different (additive) while the observed CO, LBF and LVC were significantly greater (hyper-additive), compared with the summated responses. During the MMR:CO2 -CR coactivation, in men, the observed MAP, CO and LBF were not different (additive), while the observed LVC was significantly lower (hypo-additive), compared with the summated responses. In women, the observed MAP was significantly higher (hyper-additive), while the observed CO, LBF and LVC were not different (additive), compared with the summated responses. The interaction of the MMR and CR has a pronounced influence on the autonomic cardiovascular control, with the haemodynamic consequences differing between men and women. KEY POINTS: The cardiovascular response resulting from the activation of the muscle mechanoreflex (MMR) or the chemoreflex (CR) was previously shown to be different between women and men; this study focused on the haemodynamic consequence of the interaction of these two sympathoexcitatory reflexes. MMR and CR were activated by passive leg movement and exposure to hypoxia (O2 -CR) or hypercapnia (CO2 -CR), respectively. Individual and interactive reflex effects on central and peripheral haemodynamics were quantified in healthy young women and men. In men, the MMR:O2 -CR and MMR:CO2 -CR interactions restricted peripheral haemodynamics, likely by potentiating sympathetic vasoconstriction. In women, the MMR:O2 -CR interaction facilitated central and peripheral haemodynamics, likely by potentiating sympathetic vasodilatation; however, the MMR:CO2 -CR interaction was simply additive for the central and peripheral haemodynamics. The interaction between the MMR and the CR exerts a profound influence on the autonomic control of cardiovascular function in humans, with the haemodynamic consequences differing between women and men.

Regional Versus Global Measurements of Right Ventricular Strain Performed in the Operating Room With Transesophageal Echocardiography.

OBJECTIVE: To compare regional and global measures of right ventricular (RV) strain in patients undergoing intraoperative transesophageal echocardiography (TEE). DESIGN: Prospective, nonrandomized, observational study. SETTING: Single tertiary-level, university hospital. PARTICIPANTS: The study comprised 48 patients undergoing intraoperative TEE. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: A global RV strain measurement (termed RV 5-wall strain [RV 5WS]) was calculated by averaging the longitudinal strain calculated from multiple TEE views. This global strain measurement was compared with the more standard regional strain measurements obtained in a single 4-chamber view (RV free-wall strain [RV FWS] and RV global longitudinal strain [RV GLS]) and with traditional measures of RV function. Regional and global strain measurements were feasible in the operating room. RV FWS and RV GLS strongly correlated with RV 5WS (r = 0.86 and 0.87, respectively) with no significant bias and limits of agreement of approximately -5% to 5%. RV FWS and RV GLS were even more closely correlated with each other (r = 0.99) with no significant bias and limits of agreement less than -2% to 2%. Both regional and global RV strain measurements showed a high sensitivity (RV FWS 94%; RV GLS 94%; RV 5WS 89%) and moderate specificity (RV FWS 70%; RV GLS 67%; RV 5WS 63%) for RV dysfunction based on a reference standard of 3-dimensional RV ejection fraction. CONCLUSIONS: Both regional and global RV strain measurements are feasible in the operating room with TEE. Regional and global measures of RV function correlate well and are sensitive indicators of RV dysfunction.

A Comparison of Left- and Right-Sided Strain Software for the Assessment of Intraoperative Right Ventricular Function.

OBJECTIVE: To compare intraoperative right ventricular (RV) strain measurements made with left ventricular (LV) strain software commonly found on the echocardiography machine (Philips QLAB chamber motion quantification, version 10.7, Philips, Amsterdam, The Netherlands), with offline analysis using the dedicated RV strain software (EchoInsight, version 2.2.6.2230, Epsilon Imaging, Ann Arbor, MI). DESIGN: Prospective, nonrandomized, observational study. SETTING: Single tertiary level, university-affiliated hospital. PARTICIPANTS: The study comprised 48 patients undergoing transesophageal echocardiography for cardiac or noncardiac surgery. INTERVENTIONS: Two-dimensional (2D) and 3-dimensional (3D) images of the right ventricle were obtained. Intraoperative 2D images were analyzed in real time for RV free wall strain (FWS) and global longitudinal strain (GLS) using QLAB chamber motion quantification (CMQ) LV strain software on the echocardiography machine. Two dimensional images were then analyzed offline to determine the RV FWS and GLS using EchoInsight RV-specific strain software. Three-dimensional images were then analyzed offline to detemine the 3D RV ejection fraction (3D RV EF) using TomTec 4D RV function (Unterschleissheim, Germany). Spearman's correlation and Bland-Altman analyses were used to characterize the relationship between RV strain measurements. Both types of strain measurements were compared to a reference standard of 3D RV EF. MEASUREMENTS AND MAIN RESULTS: Intraoperative RV strain measurements using LV-specific strain software correlated with offline RV strain measurements using the RV-specific strain software (FWS rho = 0.85; GLS rho = 0.81). The bias and limits of agreement were 0.75% (- 6.66 to 8.17) for FWS and -4.53% (-11.55 to 2.50) for GLS. The sensitivity and specificity for RV dysfunction for the intraoperative LV-specific software were 94% (95% confidence interval [CI] 73-100) and 70% (95% CI 51-85), respectively, for RV FWS and 94% (95% CI 73-100) and 67% (95% CI 47-83), respectively, for RV GLS. The sensitivity and specificity for RV dysfunction for the offline RV-specific software were 89% (95% CI 65-99) and 73% (95% CI 54-88), respectively, for RV FWS and 94% (95% CI 73-100) and 30% (95% CI 15-49), respectively, for RV GLS. CONCLUSION: Intraoperative RV strain measurements using LV-specific strain software commonly available on the echocardiography machine (QLAB CMQ) correlate with offline RV strain measurements using RV-specific strain software (EchoInsight). The bias and limits of agreement for these left- and right-sided strain software suggest that these 2 measures of RV function cannot be used interchangeably. Both, however, were sensitive measures of RV dysfunction and therefore are likely clinically relevant.

Intraoperative Transesophageal Echocardiography and Right Ventricular Failure After Left Ventricular Assist Device Implantation.

OBJECTIVE: To determine whether intraoperative measures of right ventricular (RV) function using transesophageal echocardiography are associated with subsequent RV failure after left ventricular assist device (LVAD) implantation. DESIGN: Retrospective, nonrandomized, observational study. SETTING: Single tertiary-level, university-affiliated hospital. PARTICIPANTS: The study comprised 100 patients with systolic heart failure undergoing elective LVAD implantation. INTERVENTIONS: Transesophageal echocardiographic images before and after cardiopulmonary bypass were analyzed to quantify RV function using tricuspid annular plane systolic excursion (TAPSE), tricuspid annular systolic velocity (S'), fractional area change (FAC), RV global longitudinal strain, and RV free wall strain. A chart review was performed to determine which patients subsequently developed RV failure (right ventricular assist device placement or prolonged inotrope requirement ≥14 days). MEASUREMENTS AND MAIN RESULTS: Nineteen patients (19%) subsequently developed RV failure. Postbypass FAC was the only measure of RV function that distinguished between the RV failure and non-RV failure groups (21.2% v 26.5%; p = 0.04). The sensitivity, specificity, and area under the curve of an abnormal RV FAC (<35%) for RV failure after LVAD implantation were 84%, 20%, and 0.52, respectively. No other intraoperative measure of RV function was associated with subsequent RV failure. RV failure increased ventilator time, intensive care unit and hospital length of stay, and mortality. CONCLUSION: Intraoperative measures of RV function such as tricuspid annular plane systolic excursion, tricuspid annular systolic velocity, and RV strain were not associated with RV failure after LVAD implantation. Decreased postbypass FAC was significantly associated with RV failure but showed poor discrimination.

Excessive Surgical Adhesive Mimicking Aortic Root Abscess: A Case Report.

Aortic root abscess is a complication of aortic valve endocarditis that is associated with a high morbidity and mortality. The diagnosis usually is made with transesophageal echocardiography, which is highly sensitive and specific for the disease. We present a case of suspected aortic root abscess 1 week after mechanical aortic valve replacement for native valve endocarditis. The diagnosis was made by the use of transesophageal echocardiography but surgical inspection revealed that the paravalvular fluid collection was excessive surgical adhesive. We discuss the clinical significance and differential diagnosis of aortic root abscess in the setting of infective endocarditis.

Measuring briefing and checklist compliance in surgery: a tool for quality improvement.

Operating room briefings improve patient outcomes; however, implementation and methods to measure are lacking. A briefing audit tool was developed with 4 domains: briefing logistics, briefing basics, specific briefing content, and briefing participation. The tool evaluated preoperative briefings across surgical services at an academic medical center. Sixty-three preoperative briefings were observed. Introduction by name and role occurred in 15% of cases. There was a wide variation in discussion of the critical goals of the surgical procedure among services D (100%), A (26%), B (19%), and C (0%). Participation in the briefing was variable among stakeholders and between services. Verbal contributions were variable across all roles ranging from 65% (surgeons) to 11% (trainees and surgical technologist). Preoperative briefing compliance is variable. Deficiencies varied between service lines, possibly highlighting the need for service-specific customization of the briefing tool in surgery. This tool is a practical method for the study of briefing implementation.