Can (and should) the venous tone be monitored at the bedside?

Determinants of venous return in steady-state physiology and asphyxia-induced circulatory shock and arrest: an experimental study

Background

Mean circulatory filling pressure (Pmcf) provides information on stressed volume and is crucial for maintaining venous return. This study investigated the Pmcf and other determinants of venous return in dysrhythmic and asphyxial circulatory shock and arrest.

Methods

Twenty Landrace/Large-White piglets were allocated into two groups of 10 animals each. In the dysrhythmic group, ventricular fibrillation was induced with a 9 V cadmium battery, while in the asphyxia group, cardiac arrest was induced by stopping and disconnecting the ventilator and clamping the tracheal tube at the end of exhalation. Mean circulatory filling pressure was calculated using the equilibrium mean right atrial pressure at 5–7.5 s after the onset of cardiac arrest and then every 10 s until 1 min post-arrest. Successful resuscitation was defined as return of spontaneous circulation (ROSC) with a MAP of at least 60 mmHg for a minimum of 5 min.

Results

After the onset of asphyxia, a ΔPmca increase of 0.004 mmHg, 0.01 mmHg, and 1.26 mmHg was observed for each mmHg decrease in PaO₂, each mmHg increase in PaCO_2, and each unit decrease in pH, respectively. Mean Pmcf value in the ventricular fibrillation and asphyxia group was 14.81 ± 0.5 mmHg and 16.04 ± 0.6 mmHg (p < 0.001) and decreased by 0.031 mmHg and 0.013 mmHg (p < 0.001), respectively, for every additional second passing after the onset of cardiac arrest. With the exception of the 5–7.5 s time interval, post-cardiac arrest right atrial pressure was significantly higher in the asphyxia group. Mean circulatory filling pressure at 5 to 7.5 s after cardiac arrest predicted ROSC in both groups, with a cut-off value of 16 mmHg (AUC = 0.905, p < 0.001).

Conclusion

Mean circulatory filling pressure was higher in hypoxic hypercapnic conditions and decreased at a lower rate after cardiac arrest compared to normoxemic and normocapnic state. A Pmcf cut-off point of 16 mmHg at 5–7.5 s after cardiac arrest can highly predict ROSC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40635-022-00440-z.

[Haemodynamic monitoring in sepsis and septic shock]

Cardiovascular disturbances associated with sepsis cause hypoperfusion situations, which will negatively impact these patients' prognosis. The aim of haemodynamic monitoring is to guide the detection and correction of this hypoperfusion, and assist in decision making in optimising oxygen transport to tissues, primarily by manipulating cardiac output. This review seeks to summarise the different parameters of haemodynamic monitoring, the objectives of resuscitation, the physiological parameters, and the tools available to us for appropriate cardiac output manipulation.

Measurement of mean systemic filling pressure after severe hemorrhagic shock in swine anesthetized with propofol-based total intravenous anesthesia: implications for vasopressor-free resuscitation

Background

Mean systemic filling pressure (Pmsf) is a quantitative measurement of a patient’s volume status and represents the tone of the venous reservoir. The aim of this study was to estimate Pmsf after severe hemorrhagic shock and cardiac arrest in swine anesthetized with propofol-based total intravenous anesthesia, as well as to evaluate Pmsf’s association with vasopressor-free resuscitation.

Methods

Ten healthy Landrace/Large-White piglets aged 10–12 weeks with average weight 20±1 kg were used in this study. The protocol was divided into four distinct phases: stabilization, hemorrhagic, cardiac arrest, and resuscitation phases. We measured Pmsf at 5–7.5 seconds after the onset of cardiac arrest and then every 10 seconds until 1 minute postcardiac arrest. During resuscitation, lactated Ringers was infused at a rate that aimed for a mean right atrial pressure of ≤4 mm Hg. No vasopressors were used.

Results

The mean volume of blood removed was 860±20 ml (blood loss, ~61%) and the bleeding time was 43.2±2 minutes while all animals developed pulseless electrical activity. Mean Pmsf was 4.09±1.22 mm Hg, and no significant differences in Pmsf were found until 1 minute postcardiac arrest (4.20±0.22 mm Hg at 5–7.5 seconds and 3.72±0.23 mm Hg at 55– 57.5 seconds; P=0.102). All animals achieved return of spontaneous circulation (ROSC), with mean time to ROSC being 6.1±1.7 minutes and mean administered volume being 394±20 ml.

Conclusions

For the first time, Pmsf was estimated after severe hemorrhagic shock. In this study, Pmsf remained stable during the first minute post-arrest. All animals achieved ROSC with goal-directed fluid resuscitation and no vasopressors.

Personalized physiology-guided resuscitation in highly monitored patients with cardiac arrest-the PERSEUS resuscitation protocol

Resuscitation guidelines remain uniform across all cardiac arrest patients, focusing on the delivery of chest compressions to a standardized rate and depth and algorithmic vasopressor dosing. However, individualizing resuscitation to the appropriate hemodynamic and ventilatory goals rather than a standard "one-size-fits-all" treatment seems a promising new therapeutic strategy. In this article, we present a new physiology-guided treatment strategy to titrate the resuscitation efforts to patient's physiologic response after cardiac arrest. This approach can be applied during resuscitation attempts in highly monitored patients, such as those in the operating room or the intensive care unit, and could serve as a method for improving tissue perfusion and oxygenation while decreasing post-resuscitation adverse effects.

Neonatal Hemodynamics: From Developmental Physiology to Comprehensive Monitoring

Maintenance of neonatal circulatory homeostasis is a real challenge, due to the complex physiology during postnatal transition and the inherent immaturity of the cardiovascular system and other relevant organs. It is known that abnormal cardiovascular function during the neonatal period is associated with increased risk of severe morbidity and mortality. Understanding the functional and structural characteristics of the neonatal circulation is, therefore, essential, as therapeutic hemodynamic interventions should be based on the assumed underlying (patho)physiology. The clinical assessment of systemic blood flow (SBF) by indirect parameters, such as blood pressure, capillary refill time, heart rate, urine output, and central-peripheral temperature difference is inaccurate. As blood pressure is no surrogate for SBF, information on cardiac output and systemic vascular resistance should be obtained in combination with an evaluation of end organ perfusion. Accurate and reliable hemodynamic monitoring systems are required to detect inadequate tissue perfusion and oxygenation at an early stage before this result in irreversible damage. Also, the hemodynamic response to the initiated treatment should be re-evaluated regularly as changes in cardiovascular function can occur quickly. New insights in the understanding of neonatal cardiovascular physiology are reviewed and several methods for current and future neonatal hemodynamic monitoring are discussed.

What is the impact of the fluid challenge technique on diagnosis of fluid responsiveness? A systematic review and meta-analysis

Background

The fluid challenge is considered the gold standard for diagnosis of fluid responsiveness. The objective of this study was to describe the fluid challenge techniques reported in fluid responsiveness studies and to assess the difference in the proportion of ‘responders,’ (PR) depending on the type of fluid, volume, duration of infusion and timing of assessment.

Methods

Searches of MEDLINE and Embase were performed for studies using the fluid challenge as a test of cardiac preload with a description of the technique, a reported definition of fluid responsiveness and PR. The primary outcome was the mean PR, depending on volume of fluid, type of fluids, rate of infusion and time of assessment.

Results

A total of 85 studies (3601 patients) were included in the analysis. The PR were 54.4% (95% CI 46.9–62.7) where <500 ml was administered, 57.2% (95% CI 52.9–61.0) where 500 ml was administered and 60.5% (95% CI 35.9–79.2) where >500 ml was administered (p = 0.71). The PR was not affected by type of fluid. The PR was similar among patients administered a fluid challenge for <15 minutes (59.2%, 95% CI 54.2–64.1) and for 15–30 minutes (57.7%, 95% CI 52.4–62.4, p = 1). Where the infusion time was ≥30 minutes, there was a lower PR of 49.9% (95% CI 45.6–54, p = 0.04). Response was assessed at the end of fluid challenge, between 1 and 10 minutes, and >10 minutes after the fluid challenge. The proportions of responders were 53.9%, 57.7% and 52.3%, respectively (p = 0.47).

Conclusions

The PR decreases with a long infusion time. A standard technique for fluid challenge is desirable.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-017-1796-9) contains supplementary material, which is available to authorized users.