Prognostic value of venoarterial carbon dioxide gradient in patients with severe sepsis and septic shock

Blood gas analysis as a surrogate for microhemodynamic monitoring in sepsis

BACKGROUND

Emergency patients with sepsis or septic shock are at high risk of death. Despite increasing attention to microhemodynamics, the clinical use of advanced microcirculatory assessment is limited due to its shortcomings. Since blood gas analysis is a widely used technique reflecting global oxygen supply and consumption, it may serve as a surrogate for microcirculation monitoring in septic treatment.

METHODS

We performed a search using PubMed, Web of Science, and Google scholar. The studies and reviews that were most relevant to septic microcirculatory dysfunctions and blood gas parameters were identified and included.

RESULTS

Based on the pathophysiology of oxygen metabolism, the included articles provided a general overview of employing blood gas analysis and its derived set of indicators for microhemodynamic monitoring in septic care. Notwithstanding flaws, several parameters are linked to changes in the microcirculation. A comprehensive interpretation of blood gas parameters can be used in order to achieve hemodynamic optimization in septic patients.

CONCLUSION

Blood gas analysis in combination with clinical performance is a reliable alternative for microcirculatory assessments. A deep understanding of oxygen metabolism in septic settings may help emergency physicians to better use blood gas analysis in the evaluation and treatment of sepsis and septic shock.

Mystery of PCO2 Gap in Sepsis

How to cite this article: Patil VP. Mystery of PCO2 Gap in Sepsis. Indian J Crit Care Med 2019;23(10):443-444.

Interpretation of venous-to-arterial carbon dioxide difference in the resuscitation of septic shock patients

The venous-to-arterial carbon dioxide difference [P(v-a)CO2] was calculated from the difference of venous CO2 and arterial CO2, which has been used to reflect the global flow in the circulatory shock. Moreover, recent clinical studies found the P(v-a)CO2 was related to the sublingual microcirculation perfusion in the sepsis. However, it is still controversial that whether P(v-a)CO2 could be used to assess the microcirculatory flow in septic patients. Moreover, the related influent factors should be taken into account when interpreting P(v-a)CO2 in clinical practice. This paper reviews the relevant experimental and clinical scenarios of P(v-a)CO2 with the aim to help intensivists to use this parameter in the resuscitation of septic shock patients. Furthermore, we propose a conceptual framework to manage a high P(v-a)CO2 value in the resuscitation of septic shock. The triggers of correcting an elevated P(v-a)CO2 should take into consideration the other tissue perfusion parameters. Additionally, more evidence is required to validate that a decreasing in P(v-a)CO2 by increasing cardiac output would result in improvement of microcirculation. Further investigations are necessary to clarify the relationship between P(v-a)CO2 and microcirculation.

The validity of central venous to arterial carbon dioxide difference to predict adequate fluid management during living donor liver transplantation. A prospective observational study

BACKGROUND

To assess the validity of central and pulmonary veno-arterial CO₂ gradients to predict fluid responsiveness and to guide fluid management during liver transplantation.

METHODS

In adult recipients (ASA III to IV) scheduled for liver transplantation, intraoperative fluid management was guided by pulse pressure variations (PPV). PPV of ≥15% (Fluid Responding Status-FRS) indicated fluid resuscitation with 250 ml albumin 5% boluses repeated as required to restore PPV to < 15% (Fluid non-Responding Status-FnRS). Simultaneous blood samples from central venous and pulmonary artery catheters (PAC) were sent to calculate central venous to arterial CO₂ gap [C(v-a) CO2 gap] and pulmonary venous to arterial CO₂ gap [Pulm(p-a) CO2 gap]. CO and lactate were also measured.

RESULTS

Sixty seven data points were recorded (20 FRS and 47 FnRS). The discriminative ability of central and pulmonary CO₂ gaps between the two states (FRS and FnRS) was poor with AUC of ROC of 0.698 and 0.570 respectively. Central CO₂ gap was significantly higher in FRS than FnRS (P = 0.016), with no difference in the pulmonary CO₂ gap between both states. The central and Pulmonary CO₂ gaps are weakly correlated to PPV [r = 0.291, (P = 0.017) and r = 0.367, (P = 0.002) respectively]. There was no correlation between both CO₂ gaps and both CO and lactate.

CONCLUSION

Central and the Pulmonary CO₂ gaps cannot be used as valid tools to predict fluid responsiveness or to guide fluid management during liver transplantation. CO₂ gaps also do not correlate well with the changes in PPV or CO.

TRIAL REGISTRATION

Clinicaltrials.gov Identifier: NCT03123172 . Registered on 31-march-2017.

Acute bag-valve breathing maneuvers plus manual chest compression is safe during stable septic shock: a randomized clinical trial

Objective

To evaluate the effects of bag-valve breathing maneuvers combined with standard manual chest compression techniques on safety, hemodynamics and oxygenation in stable septic shock patients.

Design

A parallel, assessor-blinded, randomized trial of two groups. A computer-generated list of random numbers was prepared by an independent researcher to allocate treatments.

Setting

The Intensive Care Unit at Hospital São Lucas, Pontifícia Universidade Católica do Rio Grande do Sul.

Participants

Fifty-two subjects were assessed for eligibility, and 32 were included. All included subjects (n = 32) received the allocated intervention (n = 19 for the Experimental Group and n = 13 for the Control Group).

Intervention

Twenty minutes of bag-valve breathing maneuvers combined with manual chest compression techniques (Experimental Group) or chest compression, as routinely used at our intensive care unit (Control Group). Follow-up was performed immediately after and at 30 minutes after the intervention.

Main outcome measure

Mean artery pressure.

Results

All included subjects completed the trial (N = 32). We found no relevant effects on mean artery pressure (p = 0.17), heart rate (p = 0.50) or mean pulmonary artery pressure (p = 0.89) after adjusting for subject age and weight. Both groups were identical regarding oxygen consumption after the data adjustment (p = 0.84). Peripheral oxygen saturation tended to increase over time in both groups (p = 0.05), and there was no significant association between cardiac output and venous oxygen saturation (p = 0.813). No clinical deterioration was observed.

Conclusion

A single session of bag-valve breathing maneuvers combined with manual chest compression is hemodynamically safe for stable septic-shocked subjects over the short-term.

Central Venous to Arterial CO2 Difference After Cardiac Surgery in Infants and Neonates

OBJECTIVES

Venous to arterial CO2 difference correlates with cardiac output in critically ill adults, but its utility in pediatric patients is unclear. We sought to correlate venous to arterial CO2 difference with other cardiac output surrogates (arteriovenous oxygen saturation difference, central venous oxygen saturation, and lactate) and investigate its capacity to predict poor outcomes associated with low cardiac output (low cardiac output syndrome) in infants after cardiac surgery with cardiopulmonary bypass.

DESIGN

Retrospective chart review. Poor outcome was defined as any inotrope score greater than 15; death, cardiac arrest, extracorporeal membrane oxygenation; and unplanned surgical reintervention.

SETTING

Pediatric cardiovascular ICU.

PATIENTS

One hundred thirty-nine infants less than 90 days who underwent cardiopulmonary bypass, from October 2012 to May 2015.

INTERVENTION

None.

MEASUREMENTS AND MAIN RESULTS

Two hundred ninety-six arterial and venous blood gas pairs from admission (n = 139), 6 (n = 62), 12 (n = 73), and 24 hours (n = 22) were included in analysis. For all pairs, venous to arterial CO2 difference was moderately correlated with arteriovenous oxygen saturation difference (R = 0.53; p < 0.01) and central venous oxygen saturation (R = -0.43; p < 0.01), but not lactate. At admission, venous to arterial CO2 difference was also moderately correlated with central venous oxygen saturation (R = -0.40; p < 0.01) and arteriovenous oxygen saturation difference (R = 0.55; p < 0.01), but not lactate. Thirty-four of 139 neonates (24.5%) had poor outcome. Median admission venous to arterial CO2 difference was 5.9 mm Hg (3.8-9.2 mm Hg). Patients with poor outcome had median admission venous to arterial CO2 difference 8.3 (5.6-14.9) versus 5.4 mm Hg (3.0-8.4 mm Hg) in those without poor outcome. Venous to arterial CO2 difference (area under the curve = 0.69; p < 0.01), serum lactate (area under the curve = 0.64; p = 0.02), and central venous oxygen saturation (area under the curve = 0.74; p < 0.01) were predictive of poor outcome. After controlling for covariates, admission venous to arterial CO2 difference remained significantly associated with poor outcome (odds ratio, 1.3; 95% CI, 1.1-1.45), including independent association with mortality (odds ratio, 1.2; 95% CI, 1.07-1.31).

CONCLUSIONS

Venous to arterial CO2 difference is correlated with important surrogates of cardiac output, and is associated with poor outcome and mortality related to low cardiac output syndrome after cardiac surgery in infants. Prospective validation of these findings, including confirmation that venous to arterial CO2 difference can identify low cardiac output syndrome in real time, is warranted.

Prognostic Value of Venous to Arterial Carbon Dioxide Difference during Early Resuscitation in Critically Ill Patients with Septic Shock

Context:

The partial pressure of venous to arterial carbon dioxide gradient (PCO₂ gap) is considered as an alternative marker of tissue hypoperfusion and has been used to guide treatment for shock.

Aims:

The aim of this study was to investigate the prognostic value of venous-to-arterial carbon dioxide difference during early resuscitation of patients with septic shock and compared it with that of lactate clearance and Acute Physiology and Chronic Health Evaluation II (APACHE-II) score.

Settings and Design:

Forty patients admitted to one Intensive Care Unit were enrolled.

Subjects and Methods:

APACHE-II score was calculated on admission. An arterial blood gas, central venous, and lactate samples were obtained on admission and after 6 h, and lactate clearance was calculated. Patients were classified retrospectively into Group I (survivors) and Group II (nonsurvivors). Pv-aCO₂ difference in the two groups was evaluated.

Statistical Analysis Used:

Data were fed to the computer and analyzed using IBM SPSS software package version 20.0.

Results:

At T0, Group II showed high PCO₂ gap (8.37 ± 1.36 mmHg) than Group I (7.55 ± 0.95 mmHg) with statistically significant difference (P = 0.030). While at T6, Group II showed higher PCO₂ gap (9.48 ± 1.47 mmHg) with statistically significant difference (P < 0.001) and higher mean lactate values (62.71 ± 23.66 mg/dl) with statistically significant difference (P < 0.001) than Group I where PCO₂ gap and mean lactate values became much lower, 5.91 ± 1.12 mmHg and 33.61 ± 5.80 mg mg/dl, respectively. Group I showed higher lactate clearance (25.42 ± 6.79%) with statistically significant difference (P < 0.001) than Group II (−69.40–15.46%).

Conclusions:

High PCO₂ gap >7.8 mmHg after 6 h from resuscitation of septic shock patients is associated with high mortality.

Prognostic value of gasometric parameters of carbon dioxide in resuscitation of septic patients. A bibliography review

The anaerobic metabolism is the cornerstone in physiopathology of septic shock. Nowadays we have both the central or mixed venous oxygen saturation and lactate levels to monitoring the metabolism in septic patients. Some studies have shown that normalization of systemic hemodynamic and oxygen metabolism variables not prevent progression to multiorgan damage and death. Recently has been proposed the venous-to-arterial carbon dioxide difference (ΔpvaCO2) as an alternative marker of tissue hypoperfusion, like Cardiac Index. High ΔpvaCO2 predicts adverse outcomes. Also has been proposed both, the ratio between the ΔpvaCO2 and arterial-to-venous oxygen content difference (ΔCavO2): ΔpvaCO2/ΔCavO2; and, the ratio between venous-to-arterial carbon dioxide difference (ΔCvaCO2) and ΔCavO2: ΔCvaCO2/ΔCavO2, as markers of anaerobic metabolism. Both of high ratios are related to high levels of lactate and worse prognosis. Therefore in patients with sepsis the combination of markers of resuscitation could be important to improve the outcomes.