Measurement of central venous oxygen saturation in patients with myocarial infarction

Hemodynamic management of cardiogenic shock in the intensive care unit

Hemodynamic derangements are defining features of cardiogenic shock. Randomized clinical trials have examined the efficacy of various therapeutic interventions, from percutaneous coronary intervention to inotropes and mechanical circulatory support (MCS). However, hemodynamic management in cardiogenic shock has not been well-studied. This State-of-the-Art review will provide a framework for hemodynamic management in cardiogenic shock, including a description of the 4 therapeutic phases from initial 'Rescue' to 'Optimization', 'Stabilization' and 'de-Escalation or Exit therapy' (R-O-S-E), phenotyping and phenotype-guided tailoring of pharmacological and MCS support, to achieve hemodynamic and therapeutic goals. Finally, the premises that form the basis for clinical management and the hypotheses for randomized controlled trials will be discussed, with a view to the future direction of cardiogenic shock.

Comparison of Hemodynamic Effects of Dobutamine and Ephedrine Infusions in Isoflurane-Anesthetized Horses

The objective of this study was to compare the hemodynamic effects of dobutamine and ephedrine during the management of anesthesia-related hypotension in healthy horses. Thirteen horses underwent general anesthesia with isoflurane and were randomly divided into two different groups, one of which received a dobutamine constant rate infusion (CRI) (1 µg/kg bwt/min) and the other received an ephedrine CRI (20 µg/kg bwt/min) when hypotension (<60 mmHg) was identified, following up to 15 min after the blood pressure reached 70 mmHg. All horses were equipped with a pulmonary artery catheter and a peripheral artery catheter, and multiparameter monitoring commenced as soon as they were under mechanical ventilation. Hemodynamic parameters were recorded, while tissue perfusion markers (peripheral oxygen saturation, arterial oxygen partial pressure, arterial carbon dioxide partial pressure, arterial pH, arterial plasma bicarbonate concentration, arterial oxygen saturation, mixed venous oxygen saturation, mixed venous oxygen content, arterial oxygen content, arteriovenous oxygen difference, oxygen delivery index, oxygen consumption index, and oxygen extraction ratio), serum lactate concentration, and troponin I concentrations were analyzed before the start of infusions (T0), when the blood pressure reached 70 mmHg (T1), and 15 min after T1 (T2). The time to restore the arterial pressure was similar in both groups (p > 0.05); however, the heart rate was higher in the ephedrine group (p = 0.0098), and sinus bradyarrhythmia occurred in the dobutamine group. Furthermore, both experimental protocols increased cardiac output (p = 0.0012), cardiac index (p = 0.0013), systemic vascular resistance (p = 0.008), systemic vascular resistance index (p < 0.001), and ameliorated perfusion markers. In the dobutamine group, the pulmonary artery wedge pressure (p < 0.001) and systolic index (p = 0.003) were elevated, while the arteriovenous oxygen difference was reduced in the ephedrine group (p = 0.02). Troponin I was used as a myocardial injury indicator, and did not differ between moments or between groups (p > 0.05). We concluded that both drugs were effective and safe to treat anesthetic hypotension under the conditions of this study.

Increased FIO2 influences SvO2 interpretation and accuracy of Fick-based cardiac output assessment in cardiac surgery patients: A prospective randomized study

INTRODUCTION

The study aimed to reveal how the fraction of inspired oxygen (FIO2) affected the value of mixed venous oxygen saturation (SvO2) and the accuracy of Fick-equation-based cardiac output (Fick-CO).

METHODS

Forty two adult patients who underwent elective cardiac surgery were enrolled and randomly divided into 2 groups: FIO2 < 0.7 or >0.85. Under stable general anesthesia, thermodilution-derived cardiac output (TD-CO), SvO2, venous partial pressure of oxygen, hemoglobin, arterial oxygen saturation, arterial partial pressure of oxygen, and blood pH levels were recorded before surgical incision.

RESULTS

Significant differences in FIO2 values were observed between the 2 groups (0.56 ± 0.08 in the <70% group and 0.92 ± 0.03 in the >0.85 group; P < .001). The increasing FIO2 values lead to increases in SvO2, venous partial pressure of oxygen, and arterial partial pressure of oxygen, with little effects on cardiac output and hemoglobin levels. When comparing to TD-CO, the calculated Fick-CO in both groups had moderate Pearson correlations and similar linear regression results. Although the FIO2 <0.7 group presented a less mean bias and a smaller limits of agreement, neither group met the percentage error criteria of <30% in Bland-Altman analysis.

CONCLUSION

Increased FIO2 may influence the interpretation of SvO2 and the exacerbation of Fick-CO estimation, which could affect clinical management.

TRIAL REGISTRATION

ClinicalTrials.gov ID number: NCT04265924, retrospectively registered (Date of registration: February 9, 2020).

Effect of Goal-directed Hemodynamic Therapy in Postcardiac Surgery Patients

Background and aims

Early goal-directed therapy (EGDT) provides preset goals to be achieved by intravenous fluid therapy and inotropic therapy with earliest detection of change in the hemodynamic profile. Improved outcome in cardiac surgery patients has been shown by perioperative volume optimization, while postoperative intensive care unit (ICU) stay can be decreased by improving oxygen delivery. Our aim of this study was to study the outcome of EGDT in patients undergoing elective cardiac surgery.

Materials and methods

This is a prospective single institute study involving a total of 478 patients. Patients were divided into group I, who received standard hospital care, and group II, who received EGDT. Postoperatively, patients were observed in ICU for 72 hours. Hemodynamics, laboratory data, fluid bolus, inotrope score, complication, ventilatory time, and mortality data were collected.

Results

Postoperative ventilatory period (11.12 ± 10.11 vs 9.45 ± 8.87, p = 0.0719) and frequency of change in inotropes (1.900 ± 0.9 vs 1.19 ± 0.61, p = 0.0717) were lower in group II. Frequency of crystalloid boluses (1.33 ± 0.65 vs 1.75 ± 1.09, p = 0.0126), and quantity of packed cell volume (PCV) used (1.63 ± 1.03 vs 2.04 ± 1.42, p = 0.0364) were highly significant in group II. Use of colloids was higher in group II and was statistically significant (1.98 ± 1.99 vs 3.05 ± 2.17, p = 0.0012). The acute kidney injury (AKI) rate was (58 (23.10%) vs 30 (13.21%), p = 0.007) lower and statistically significant (p = 0.007) in group II.

Conclusion

Early goal-directed therapy reduces the postoperative ventilatory period, frequency of changes in inotropes, and incidence of AKI, and decreases ventilation hours, number of times inotropes changed, and AKI.

How to cite this article

Patel H, Parikh N, Shah R, Patel R, Thosani R, Shah P, et al. Effect of Goal-directed Hemodynamic Therapy in Postcardiac Surgery Patients. Indian J Crit Care Med 2020;24(5):321-326.

Perioperative utility of goal-directed therapy in high-risk cardiac patients undergoing coronary artery bypass grafting: "A clinical outcome and biomarker-based study"

Goal-directed therapy (GDT) encompasses guidance of intravenous (IV) fluid and vasopressor/inotropic therapy by cardiac output or similar parameters to help in early recognition and management of high-risk cardiac surgical patients. With the aim of establishing the utility of perioperative GDT using robust clinical and biochemical outcomes, we conducted the present study. This multicenter randomized controlled study included 130 patients of either sex, with European system for cardiac operative risk evaluation ≥3 undergoing coronary artery bypass grafting on cardiopulmonary bypass. The patients were randomly divided into the control and GDT group. All the participants received standardized care; arterial pressure monitored through radial artery, central venous pressure (CVP) through a triple lumen in the right internal jugular vein, electrocardiogram, oxygen saturation, temperature, urine output per hour, and frequent arterial blood gas (ABG) analysis. In addition, cardiac index (CI) monitoring using FloTrac™ and continuous central venous oxygen saturation (ScVO₂) using PreSep™ were used in patients in the GDT group. Our aim was to maintain the CI at 2.5–4.2 L/min/m², stroke volume index 30–65 ml/beat/m², systemic vascular resistance index 1500–2500 dynes/s/cm⁵/m², oxygen delivery index 450–600 ml/min/m², continuous ScVO₂ >70%, and stroke volume variation <10%; in addition to the control group parameters such as CVP 6–8 mmHg, mean arterial pressure 90–105 mmHg, normal ABG values, oxygen saturation, hematocrit value >30%, and urine output >1 ml/kg/h. The aims were achieved by altering the administration of IV fluids and doses of inotropes or vasodilators. The data of sixty patients in each group were analyzed in view of ten exclusions. The average duration of ventilation (19.89 ± 3.96 vs. 18.05 ± 4.53 h, P = 0.025), hospital stay (7.94 ± 1.64 vs. 7.17 ± 1.93 days, P = 0.025), and Intensive Care Unit (ICU) stay (3.74 ± 0.59 vs. 3.41 ± 0.75 days, P = 0.012) was significantly less in the GDT group, compared to the control group. The extra volume added and the number of inotropic dose adjustments were significantly more in the GDT group. The two groups did not differ in duration of inotropic use, mortality, and other complications. The perioperative continuation of GDT affected the early decline in the lactate levels after 6 h in ICU, whereas the control group demonstrated a settling lactate only after 12 h. Similarly, the GDT group had significantly lower levels of brain natriuretic peptide, neutrophil gelatinase-associated lipocalin levels as compared to the control. The study clearly depicts the advantage of GDT for a favorable postoperative outcome in high-risk cardiac surgical patients.

Goal-directed therapy improves the outcome of high-risk cardiac patients undergoing off-pump coronary artery bypass

Background:

There has been a constant emphasis on developing management strategies to improve the outcome of high-risk cardiac patients undergoing surgical revascularization. The performance of coronary artery bypass surgery on an off-pump coronary artery bypass (OPCAB) avoids the risks associated with extra-corporeal circulation. The preliminary results of goal-directed therapy (GDT) for hemodynamic management of high-risk cardiac surgical patients are encouraging. The present study was conducted to study the outcome benefits with the combined use of GDT with OPCAB as compared to the conventional hemodynamic management.

Material and Method:

Patients with the European System for Cardiac Operative Risk Evaluation ≥3 scheduled for OPCAB were randomly divided into two groups; the control and GDT groups. The GDT group included the monitoring and optimization of advanced parameters, including cardiac index (CI), systemic vascular resistance index, oxygen delivery index, stroke volume variation; continuous central venous oxygen saturation (ScVO₂), global end-diastolic volume, and extravascular lung water (EVLW), using FloTrac™, PreSep™, and EV-1000^® monitoring panels, in addition to the conventional hemodynamic management in the control group. The hemodynamic parameters were continuously monitored for 48 h in Intensive Care Unit (ICU) and corrected according to GDT protocol. A total of 163 patients consented for the study.

Result:

Seventy-five patients were assigned to the GDT group and 88 patients were in the control group. In view of 9 exclusions from the GDT group and 12 exclusions from control group, 66 patients in the GDT group and 76 patients in control group completed the study.

Conclusion:

The length of stay in hospital (LOS-H) (7.42 ± 1.48 vs. 5.61 ± 1.11 days, P < 0.001) and ICU stay (4.2 ± 0.82 vs. 2.53 ± 0.56 days, P < 0.001) were significantly lower in the GDT group as compared to control group. The duration of inotropes (3.24 ± 0.73 vs. 2.89 ± 0.68 h, P = 0.005) was also significantly lower in the GDT group. The two groups did not differ in duration of ventilated hours, mortality, and other complications. The parameters such as ScVO₂, CI, and EVLW had a strong negative and positive correlation with the LOS-H with r values of − 0.331, −0.319, and 0.798, respectively. The study elucidates the role of a goal-directed hemodynamic optimization for improved outcome in high-risk cardiac patients undergoing OPCAB.

Systematic review of the association of venous oxygenation and outcome in adult hospitalized patients

BACKGROUND

Adequate tissue oxygenation is necessary to maintain organ function. Low venous oxygen saturation may reflect impaired tissue oxygenation, and may be used as a predictive tool and a therapeutic target to improve the care of critically ill patients. We therefore conducted a systematic review of the existing literature reflecting these aspects.

METHODS

We searched electronic databases in January 2016 for relevant studies on venous oxygen saturation for treatment guidance and patient outcome. We sub-grouped results based on patient groups and setting.

RESULTS

The search resulted in 5590 papers of which 42 studies were deemed relevant. The majority of the studies in cardiac and abdominal surgery patients showed associations between low venous oxygen saturation and increased mortality and morbidity, in particular increased length of intensive care. However, the cut-off level for low venous oxygen saturation varied between < 55 and 70% and all studies had high risk of bias. In patients with septic shock, recent randomized trials showed no benefit of early resuscitation guided by venous oxygen saturation.

CONCLUSION

Low venous oxygen saturation may be associated with increased mortality, morbidity and length of intensive care in patients following cardiac or abdominal surgery. However, the wide range of cut-off levels and low quality of evidence hampers the clinical application. In patients with septic shock, the present evidence does not support goal-directed therapy using venous oxygen saturation during early resuscitation.

Clinical utility of central venous saturation for the calculation of cardiac index in cardiac patients

BACKGROUND

Mixed venous saturation (MVS) obtained from the distal pulmonary artery (PA) during Swan-Ganz catheterization is the criterion standard for calculating cardiac output (CO) and cardiac index (CI) with the use of the Fick method. We think that calculating CI with the use of central venous saturation (CVS) instead of PA-MVS is both feasible and accurate. Earlier studies were small, enrolled heterogeneous patient populations, and resulted in inconsistent findings.

METHODS

All patients undergoing right heart catheterization from January 2011 to January 2012 in our catheterization lab with simultaneous measurements of MVS obtained from the distal PA and CVS obtained from the superior vena cava (SVC) or right atrium (RA) were included. Out of the 902 patients enrolled, we excluded patients (n = 50) who had known cardiac shunt or dialysis fistula, had duplicate medical records, or were septic. We calculated the CI with the use of the assumed Fick method using both MVS (criterion standard) and CVS (SVC or RA saturations) in the remaining 852 patients. We measured the correlation and the agreement between the 2 methods with the use of the Pearson correlation coefficient and Bland-Altman analysis.

RESULTS

Totals of 112 patients with simultaneous PA and RA saturation measurements (group I) and 740 patients with simultaneous PA and SVC saturation measurements (group II) were included. We found an excellent linear correlation between SVC and PA saturation (r = 0.928) and between RA and PA saturation (r = 0.95). There was also an excellent correlation between CI calculated with the use of PA saturation and CI calculated with the use of SVC (r = 0.87) or RA (r = 0.93) saturation. The mean bias of CVS-derived CI compared with MVS-derived CI (criterion standard) was -0.1 (95% limits of agreement [LOA] -1 to +0.77) in the SVC group and -0.006 (LOA -0.68 to +0.69) in the RA group. Patients with low CI had stronger correlation and smaller bias between the 2 methods compared with those with normal or high CI. The presence of baseline hypoxemia, valvular heart disease, or acute coronary syndrome had no significant effect on the correlation or the bias between the 2 methods.

CONCLUSIONS

In cardiac patients, CVS can be used as a surrogate to true MVS in the calculation of CI. This method is readily available in patients who have central venous access, and may aid in early goal-directed treatment when cardiogenic shock is suspected.

Mortality after in-hospital cardiopulmonary resuscitation: multicenter analysis in Korea

PURPOSE

The purpose of this study is to evaluate factors associated with the mortality of patients admitted to intensive care units (ICUs) after in-hospital cardiopulmonary resuscitation (CPR) and the impact of a hospital rapid response system (RRS) on patient mortality in Korea.

MATERIALS AND METHODS

A prospective multicenter cohort study was done in 22 ICUs of 15 centers from July 1, 2010, to January 31, 2011. We only enrolled patients admitted to ICUs after in-hospital CPR and divided eligible patients into 2 groups-survivors and nonsurvivors.

RESULTS

Among 4617 patients, 150 patients were admitted post-CPR, 76 died, and 74 survived. At 24 hours, the Sequential Organ Failure Assessment score, Simplified Acute Physiology Score II, and the best Glasgow Coma Scale were significantly lower in the nonsurvivors than in the survivors. In multivariate analysis, the Simplified Acute Physiology Score II and presence of lower respiratory infection were both independently associated with mortality. At the first hour after admission, lowest serum potassium and highest heart rate were associated with mortality. At 24 hours after admission, lowest mean arterial pressure, HCO3 level, and venous oxygen saturation level; highest heart rate; and use of vasoactive drugs were associated with mortality. The mortality of patients in hospitals with an RRS was not significantly different from that of hospitals without an RRS.

CONCLUSION

Various physiologic and laboratory parameters were associated with the mortality of post-CPR ICU admitted patients, and the presence of an RRS did not reduce mortality of these patients in our study.

Guidelines for maintenance of adult patients with brain death and potential for multiple organ donations: the Task Force of the Brazilian Association of Intensive Medicine the Brazilian Association of Organs Transplantation, and the Transplantation Center of Santa Catarina

INTRODUCTION

The organ shortage for transplantation, the principal factor that increases waiting lists, has become a serious public health problem. In this scenario, the intensivist occupies a prominent position as one of the professionals that first has a chance to identify brain death and to be responsible for the maintenance of the potential deceased donor.

OBJECTIVE

This report attempts to establish guidelines for care and maintenance of adult deceased donor organs guiding and standardizing care provided to patients with brain death.

METHOD

These guidelines were composed by intensivists, transplant coordinators, professionals from various transplant teams, and used transplant center. The formulated questions were forwarded to all members and recommendations were constructed after an extensive literature review selecting articles with the highest degree of evidence.

RESULTS

Guidelines were developed in the form of questions reflecting frequent experiences in clinical intensive care practices. The main questions were: Is there an optimal interval for keeping organs of deceased donors viable? What actions are considered essential for maintaining deceased donors in this period? What are the limits of body temperature? How should the patient be warmed? Which laboratory tests should be performed? What is the collection interval? What are the limits in the laboratory and the capture scenario? What are the limits of blood pressure? When and how should one use catecholamines?

CONCLUSIONS

This pioneer project involved a multidisciplinary team working in organ transplantation seeking to provide treatment guidance to increase the number of viable organs from deceased adult donors.

Near-infrared spectroscopy for evaluation of global and skeletal muscle tissue oxygenation

Non-invasive clinical examination has well-recognized limitations in detecting compensated and uncompensated low flow states and their severity. This paper describes the principles of near-infrared absorption spectroscopy (NIRS) and the basis for its proposed use in heart failure/cardiogenic and septic shock to assess global and regional tissue oxygenation. The vascular occlusion test is explained. Limitations of NIRS, current controversies, and what is necessary in the future to make this technology a part of the initial and ongoing assessment of a patient are also discussed. The ultimate goal of such techniques is to prevent miss-assessment and inadequate resuscitation of patients, two major factors in the development of multisystem organ failure and death.

Femoral-based central venous oxygen saturation is not a reliable substitute for subclavian/internal jugular-based central venous oxygen saturation in patients who are critically ill

BACKGROUND

Central venous oxygen saturation (Scv(O(2))) has been used as a surrogate marker for mixed venous oxygen saturation (Sv(O(2))). Femoral venous oxygen saturation (Sfv(O(2))) is sometimes used as a substitute for Scv(O(2)). The purpose of this study is to test the hypothesis that these values can be used interchangeably in a population of patients who are critically ill.

METHODS

We conducted a survey to assess the frequency of femoral line insertion during the initial treatment of patients who are critically ill. Scv(O(2)) vs Sfv(O(2)) STUDY: Patients with femoral and nonfemoral central venous catheters (CVCs) were included in this prospective study. Two sets of paired blood samples were drawn simultaneously from the femoral and nonfemoral CVCs. Blood samples were analyzed for oxygen saturation and lactate.

RESULTS

One hundred and fifty physicians responded to the survey. More than one-third of the physicians insert a femoral line at least 10% of the time during the initial treatment of patients who were critically ill. Scv(O(2)) vs Sfv(O(2)) STUDY: Thirty-nine patients were enrolled. The mean Scv(O(2)) and Sfv(O(2)) were 73.1% +/- 11.6% and 69.1% +/- 12.9%, respectively (P = .002), with a mean bias of 4.0% +/- 11.2% (95% limits of agreement: -18.4% to 26.4%). The mean serum lactate from the nonfemoral and femoral CVCs was 2.84 +/- 4.0 and 2.72 +/- 3.2, respectively (P = .15).

CONCLUSIONS

This study revealed a significant difference between paired samples of Scv(O(2)) and Sfv(O(2)). More than 50% of Scv(O(2)) and Sfv(O(2)) values diverged by > 5%. Sfv(O(2)) is not always a reliable substitute for Scv(O(2)) and should not routinely be used in protocols to help guide resuscitation.

[Haemodynamic monitoring in the perioperative phase. Available systems, practical application and clinical data]

A regular hydration status and compensated vascular filling are targets of perioperative fluid and volume management and, in parallel, represent precautions for sufficient stroke volume and cardiac output to maintain tissue oxygenation. The physiological and pathophysiological effects of fluid and volume replacement mainly depend on the pharmacological properties of the solutions used, the magnitude of the applied volume as well as the timing of volume replacement during surgery. In the perioperative setting surgical stress induces physiological and hormonal adaptations of the body, which in conjunction with an increased permeability of the vascular endothelial layer influence fluid and volume management. The target of haemodynamic monitoring in the operation room is to collect data on haemodynamics and global oxygen transport, which enable the anaesthetist to estimate the volume status of the vascular system. Particularly in high risk patients this may improve fluid and volume therapy with respect to maintaining cardiac output. A goal-directed volume management aiming at preventing hypovolaemia may improve the outcome after surgery. The objective of this article is to review the monitoring devices that are currently used to assess haemodynamics and filling status in the perioperative setting. Methods and principles for measuring haemodynamic variables, the measured and calculated parameters as well as clinical benefits and shortcomings of each device are described. Furthermore, the results for monitoring devices from clinical studies of goal-directed fluid and volume therapy which have been published will be discussed.

Correlation between central venous oxygen saturation and oxygen delivery changes following fluid therapy

BACKGROUND

The rationale for using central venous oxygen saturation (ScvO(2)) in various clinical scenarios is that it reflects the balance between oxygen delivery (DO(2)) and demands. In this study, we evaluated the correlation between ScvO(2) and DO(2) changes (Delta Do(2), DeltaScvO(2)) in patients receiving fluid therapy following coronary surgery. We also correlated the changes of mean arterial pressure (Delta MAP) and central venous pressure (Delta CVP), with Delta DO(2).

METHODS

Sixty consecutive sedated and mechanically ventilated adult patients, with cardiac index <or=2.3 L/min/m(2) and a pulmonary artery occlusion pressure <or=12 mmHg following coronary surgery, were included. Concomitant hemodynamic parameters, arterial and venous blood gases were measured before (T0) and after (T1) administration of a 500 ml bolus of an isotonic crystalloid solution over 30 min. The correlations between Delta DO(2) and DeltaScvO(2), Delta MAP or Delta CVP were evaluated by linear regression analysis and Pearson test.

RESULTS

Cardiac index (1.9+/-0.2 vs 2.3+/-0.5 ml/min/m(2)), MAP (83+/-11 vs 94+/-13 mm Hg) and CVP (5.7+/-3 vs 7.1+/-3 mmHg) were significantly higher at T1 compared with T0. The correlation of Delta DO(2) with DeltaScvO(2) was positive, significant (r=0.41; P=0.004) and superior to its correlation with Delta MAP (r=0.30; P=0.01) or Delta CVP (r=0.03; P=0.78).

CONCLUSION

A significant correlation between ScvO(2) and DO(2) changes was found in patients receiving fluid therapy following coronary surgery. ScvO(2) could be used as an indicator to track DO(2) and to guide volume loading.

Skeletal muscle oxygen saturation does not estimate mixed venous oxygen saturation in patients with severe left heart failure and additional severe sepsis or septic shock

INTRODUCTION

Low cardiac output states such as left heart failure are characterized by preserved oxygen extraction ratio, which is in contrast to severe sepsis. Near infrared spectroscopy (NIRS) allows noninvasive estimation of skeletal muscle tissue oxygenation (StO2). The aim of the study was to determine the relationship between StO2 and mixed venous oxygen saturation (SvO2) in patients with severe left heart failure with or without additional severe sepsis or septic shock.

METHODS

Sixty-five patients with severe left heart failure due to primary heart disease were divided into two groups: groups A (n = 24) and B (n = 41) included patients without and with additional severe sepsis/septic shock, respectively. Thenar muscle StO2 was measured using NIRS in the patients and in 15 healthy volunteers.

RESULTS

StO2 was lower in group A than in group B and in healthy volunteers (58 +/- 13%, 90 +/- 7% and 84 +/- 4%, respectively; P < 0.001). StO2 was higher in group B than in healthy volunteers (P = 0.02). In group A StO2 correlated with SvO2 (r = 0.689, P = 0.002), although StO2 overestimated SvO2 (bias -2.3%, precision 4.6%). In group A changes in StO2 correlated with changes in SvO2 (r = 0.836, P < 0.001; DeltaSvO2 = 0.84 x DeltaStO2 - 0.67). In group B important differences between these variables were observed. Plasma lactate concentrations correlated negatively with StO2 values only in group A (r = -0.522, P = 0.009; lactate = -0.104 x StO2 + 10.25).

CONCLUSION

Skeletal muscle StO2 does not estimate SvO2 in patients with severe left heart failure and additional severe sepsis or septic shock. However, in patients with severe left heart failure without additional severe sepsis or septic shock, StO2 values could be used to provide rapid, noninvasive estimation of SvO2; furthermore, the trend in StO2 may be considered a surrogate for the trend in SvO2.

Mixed venous oxygen saturation cannot be estimated by central venous oxygen saturation in septic shock

OBJECTIVE

Central venous oxygen saturation (ScvO2) in initial resuscitation is included in the Surviving Sepsis Campaign guidelines. ScvO2 monitoring has also been suggested to be comparable to mixed venous oxygen saturation (SvO2) for clinical purposes. The aim of our study was to assess the correlation and agreement of ScvO2 and SvO2 and compare ScvO2-SvO2 difference to lactate, oxygen-derived and hemodynamic parameters in early septic shock in ICU after initial resuscitation.

DESIGN AND SETTING

Prospective clinical study with 16 patients with septic shock at two university hospital ICUs. A dose of norepinephrine over 0.1 microg/kg/min was required for inclusion.

MEASUREMENTS AND RESULTS

Five paired ScvO2 and SvO2 samples at 6-h intervals, altogether 72 samples, were collected during 24 h. The mean SvO2 was below the mean ScvO2 at all time points. Bias of difference was 4.2% and 95% limits of agreement ranged from -8.1% to 16.5%. The difference correlated significantly to CI and DO2.

CONCLUSIONS

The difference between paired ScvO2 and SvO2 varies highly. Therefore, SvO2 may not be estimated on the basis of ScvO2 in treatment of septic shock after resuscitation period in ICU.

Severe sepsis and septic shock: review of the literature and emergency department management guidelines

Severe sepsis and septic shock are as common and lethal as other acute life-threatening conditions that emergency physicians routinely confront such as acute myocardial infarction, stroke, and trauma. Recent studies have led to a better understanding of the pathogenic mechanisms and the development of new or newly applied therapies. These therapies place early and aggressive management of severe sepsis and septic shock as integral to improving outcome. This independent review of the literature examines the recent pathogenic, diagnostic, and therapeutic advances in severe sepsis and septic shock for adults, with particular relevance to emergency practice. Recommendations are provided for therapies that have been shown to improve outcomes, including early goal-directed therapy, early and appropriate antimicrobials, source control, recombinant human activated protein C, corticosteroids, and low tidal volume mechanical ventilation.

The value of venous oximetry

PURPOSE OF REVIEW

Maintenance of adequate tissue oxygenation is an important task in intensive care units. In this context, venous oximetry by obtaining mixed venous oxygen saturation or central venous oxygen saturation has been discussed as useful monitoring parameters. This review discusses the physiology and clinical application of these parameters.

RECENT FINDINGS

No study has so far demonstrated that venous oxygen saturation monitoring can reduce mortality in critically ill patients although length of stay has been decreased in cardiac surgery patients. Furthermore, pulmonary artery catheter usage does not affect outcome in critically ill patients. In contrast, early goal directed therapy for patients with severe sepsis or septic shock, which includes treatment goals for mean arterial pressure, central venous pressure, and central venous oxygen saturation, was able to increase survival in these patients. There is also evidence that central venous oxygen saturation measurement is beneficial in other types of shock.

SUMMARY

Early goal directed therapy should be implemented in the initial resuscitation of septic patients. Measurement of central venous oxygen saturation can easily be applied in intensive care unit patients and offers a useful indirect indicator for the adequacy of tissue oxygenation.

Continuous central venous and pulmonary artery oxygen saturation monitoring in the critically ill

OBJECTIVE

To compare the course of continuously measured mixed and central venous O(2) saturations in high-risk patients and to evaluate the impact of various factors that might interfere with reflection spectrophotometry.

DESIGN AND SETTING

Prospective, descriptive study in the interdisciplinary ICU of a university hospital.

PATIENTS

32 critically ill patients with triple-lumen central vein catheters, including 29 patients requiring pulmonary artery catheterization.

INTERVENTIONS

The accuracy of fiberoptic measurements was assessed by comparison to reference co-oximeter results at regular intervals. We examined the effect on measurement accuracy of physiological variables including hematocrit, hemoglobin, pH, temperature, and the administration of various solutions via central venous catheter. Continuous parallel measurements of SvO(2) and ScvO(2) were performed in patients with each type of catheters over a total observation time of 1097 h.

RESULTS

ScvO(2) values were more accurate and stable than in vitro oximeter measurements ( r=0.96 from 150 samples, mean difference 0.15%, average drift 0.10%/day) and was not significantly affected by synchronous infusion therapy or by changes in hematocrit, hemoglobin, pH, or temperature. ScvO(2) values closely paralleled SvO(2), whether measured in vitro ( r=0.88 from 150 samples) or in vivo ( r=0.81 from 395,128 samples) but averaged about 7+/-4 saturation percentage higher. ScvO(2) changed in parallel in 90% of the 1,498 instances in which SvO(2) changed more than 5% (over an average of 43 min).

CONCLUSIONS

Continuous fiberoptic measurement of central vein O(2) saturation has potential to be a reliable and convenient tool which could rapidly warn of acute change in the oxygen supply/demand ratio of critically ill patients.

Central venous oxygen saturation monitoring in the critically ill patient

In the initial treatment of a critically ill patient, blood pressure, heart rate, urine output, and central venous pressure guide resuscitative efforts. Despite normalization of these variables, global tissue hypoxia may still persist and has been implicated in the development of multiorgan failure and increased mortality. Definitive management includes intensive care unit admission, pulmonary artery catheterization using mixed venous oxygen saturation (SvO2), and hemodynamic optimization. In the absence of or before definitive management, hemodynamic optimization can be performed using central venous oxygen saturation (ScvO2) as a surrogate. The physiology, technology, clinical uses, and rationale for ScvO2 monitoring are reviewed, including issues regarding physiologic equivalence to SvO2. The clinical use of ScvO2 monitoring, evidence-based outcome implications, and limitations of ScvO2 monitoring will also be examined.

The pulmonary artery catheter: uses and controversies

The pulmonary artery catheter is an invasive hemodynamic monitor that can provide diagnostic information in situations where history and physical examination are inconclusive. Assisting the physician in therapeutic decisions has added to its clinical value. Understanding the information it provides and making thoughtful therapeutic decisions lie at the core of its use. Despite its use, the PA catheter has been the center of great controversy. Clearly the paucity of prospective randomized trials proving its efficacy is alarming. The inability of physicians to interpret the provided data properly is also unacceptable. Although instituting a moratorium on its use may be extreme, limiting its use to approved indications seems more appropriate. In the future, ready availability of other less invasive methods such as echocardiography may allow clinicians to become less reliant on the PA catheter. Until then, clinicians would be served best by comprehending the intricacies and the limitations of this sophisticated instrument.

Undetected cardiogenic shock in patients with congestive heart failure presenting to the emergency department

The purpose of this study was to examine the use of lactic acid levels and continuous central venous oxygen saturation (central venous oximetry) to stratify and treat patients with acutely decompensated end-stage chronic congestive heart failure (CHF) presenting to the emergency department. This prospective, convenience, non-outcome study was performed at an urban tertiary care hospital. Patients with end-stage CHF with an ejection fraction <30% presenting in decompensated CHF were eligible for the study. Patients were assessed using the Killip classification and New York Heart Association criteria. After lactic acid levels were obtained, patients were managed according to a standardized protocol guided by central venous oximetry. The patients were divided into high lactic acid (n = 22), low lactic acid (n = 5), and control groups (stable patients presenting to a cardiology clinic, n = 17) for comparison. There was no statistical difference in vital signs, or Killip and New York Heart Association criteria among the 3 groups. Central venous oxygen saturation was significantly lower in the high lactic acid group (32 +/- 12%) than in the normal lactic acid (51 +/- 13%) and control groups (60 +/- 6%) (p < 0.001). After treatment there was a significant decrease in lactic acid (-3.65 +/- 3.65 mM/L) and an increase in central venous oxygen saturation (32 +/- 13%) in the high lactic acid group compared with the normal lactic acid group (p < 0.001). A significant subset of patients with decompensated end-stage CHF present to the emergency department in occult shock and are clinically indistinguishable from patients with mildly decompensated CHF and stable CHF. Once identified, these patients require aggressive alternative management and disposition. Further study is necessary to identify whether this intervention impacts morbidity, mortality, and health care resource consumption.

The clinical implications of continuous central venous oxygen saturation during human CPR

STUDY OBJECTIVE

The purpose of this study was to observe, measure, and describe the changes in central venous oxygen saturation during CPR and immediately after return of spontaneous circulation. It also was to examine the clinical utility of continuous central venous oxygen saturation monitoring as a indicator of return of spontaneous circulation during CPR in human beings.

DESIGN AND SETTING

Eight-month, prospective, non-outcome, observational, nonrandomized case series in the ED of a large urban hospital. TYPES OF PATIENTS: Adult normothermic, nontraumatic, out-of-hospital cardiopulmonary arrests.

INTERVENTIONS

All patients were managed according to advanced cardiac life support guidelines. A proximal aortic and double-lumen central venous catheter was placed. Central venous oxygen saturation was measured continuously spectrophotometrically with a fiberoptic catheter in the central venous location.

MEASUREMENTS

Aortic blood pressure and central venous oxygen saturation were simultaneously measured throughout each resuscitation. Return of spontaneous circulation was defined as a systolic blood pressure of more than 60 mm Hg for more than five minutes.

RESULTS

One hundred patients who experienced 68 episodes of cardiac arrest were studied. Patients with return of spontaneous circulation had a higher initial and statistically higher mean and maximal central venous oxygen saturation than those without return of spontaneous circulation (P = .23, .0001, and .0001, respectively; P less than .05 is significant). No patient attained return of spontaneous circulation without reaching a central venous oxygen saturation of at least 30%. Only one of 68 episodes of return of spontaneous circulation was attained without reaching a central venous oxygen saturation of at least 40%. A central venous oxygen saturation of greater than 72% was 100% predictive of return of spontaneous circulation.

CONCLUSION

Continuous central venous oxygen saturation monitoring can serve as a reliable indicator of return of spontaneous circulation during CPR in human beings.

Mixed venous oxygen saturation as a guide to tissue oxygenation and prognosis in patients with acute myocardial infarction

The relation of mixed venous oxygen saturation and the cardiac index to tissue oxygenation and prognosis was investigated in 119 patients with acute myocardial infarction. There was a positive correlation between mixed venous oxygen saturation and the cardiac index in 97 survivors and 22 nonsurvivors, but a significantly lower mixed venous oxygen saturation level at the same level of cardiac index was observed in nonsurvivors compared with survivors. Results of multivariate analysis with mixed venous oxygen saturation and the cardiac index indicated that only mixed venous oxygen saturation was significantly related to survival and to hyperlactacidemia. Oxygen delivery to tissues declined significantly in nonsurvivors because of a lower cardiac index and a lower hemoglobin concentration in these patients than in survivors. However, at the same level of oxygen delivery to tissues, nonsurvivors had a significantly higher rate of oxygen consumption leading to a correspondingly greater decrease in mixed venous oxygen saturation, suggesting that a greater increase in oxygen demand was also observed in nonsurvivors than in survivors. Thus mixed venous oxygen saturation after acute myocardial infarction is a better predictor of hyperlactacidemia and survival than the cardiac index, and this may be associated with an increased oxygen demand and an impaired oxygen transport system in seriously ill patients.

Comparison of central-venous to mixed-venous oxygen saturation during changes in oxygen supply/demand

Because central venous O2 saturation (superior vena cava, ScvO2) can be monitored with less patient risk than mixed venous O2 saturation (pulmonary artery, SvO2), we examined the correlations between SvO2 and ScvO2 over a broad range of cardiorespiratory conditions, including hypoxia, hemorrhage, and resuscitation in anesthetized dogs. The correlation coefficient (r) between SvO2 and ScvO2 in 179 simultaneously drawn blood samples from 22 dogs was 0.97. In another nine dogs, the two sites were continuously and simultaneously monitored with fiberoptic catheters; r was 0.96 with a mean difference of 3.7 +/- 2.9 percent (SD) saturation. In each dog the changes in ScvO2 closely paralleled the changes in SvO2. Although absolute values of ScvO2 are not sufficiently identical to SvO2 to calculate O2 uptake or pulmonary shunt precisely, close tracking of changes in the two sites across a wide range of hemodynamic conditions warrant further consideration of ScvO2 for patient monitoring of trends in O2 supply/demand.

Hemodynamic abnormalities in acute myocardial infarction

Great strides have been made in the management of patients with acute myocardial infarction since the advent of coronary care units. However, congestive heart failure continues to be the major cause of in-hospital mortality. The accurate diagnosis and classification of hemodynamic abnormalities allow the application of specific therapies for each patient. Because clinicians can now routinely measure left and right ventricular preload, systemic and pulmonary vascular resistance, cardiac output, and arteriovenous oxygen difference, pharmacologic and surgical interventions can be applied in a scientific manner. In addition, mechanical complications can be promptly recognized and aggressively treated. Although the mortality rate for patients with severe left ventricular dysfunction after myocardial infarction remains high, expert management offers an improved prognosis for many patients.

Continuous venous oximetry in surgical patients

A prospective study was performed to evaluate the efficacy of continuous venous oximetry to supplement traditional hemodynamic monitoring in 39 critically ill surgical patients. There was no statistically significant difference in SvO2 between the continuous in vivo values and in vitro values (0.694 +/- 0.095 vs. 0.698 +/- 0.108). There was no statistically significant correlation between continuously measured SvO2 and PaO2 (r = 0.09, p greater than 0.5), SaO2 (r = 0.08, p greater than 0.5), or oxygen consumption (r = 0.46, p greater than 0.5). There was a slight but statistically significant correlation between continuously measured SvO2 and cardiac output (r = 0.40, p less than 0.025) and oxygen delivery (r = 0.49, p less than 0.005). There was a highly significant correlation between continuously measured SvO2 and oxygen utilization coefficient (r = -0.96, p less than 0.001). Continuously measured SvO2 is a reliable predictor of SvO2 measured intermittently by in vitro methods. In critically ill surgical patients, SvO2 does not correlate highly with the individual determinants of oxygen transport but rather correlates with the oxygen utilization coefficient and therefore reflects the overall balance between oxygen consumption and delivery.

Preoperative assessment of high-risk surgical patients

From the foregoing accounts of preoperative assessment of myocardial performance, as well as preload and afterload status it is clear that the proper anesthesia techniques and agents can be selected. Physiologically optimal adjustments of preload, afterload, and myocardial function can be attained by the appropriate, harmonious selection of anesthesia technique and vasoactive drugs made on the basis of close hemodynamic monitoring preoperatively, intraoperatively, and in the immediate postoperative period.

Continuous monitoring of mixed venous oxygen tension (PvO2) in cardiorespiratory disorders

The development of a miniature polarographic electrode mounted in the tip of a double-lumen plastic catheter has made possible continuous in-vivo monitoring of oxygen tension. Inexpensive catheters of this type have already proved of value as a means of continuously monitoring arterial oxygen tension in the newborn. In 25 patients with acute respiratory failure we found that these catheters could be safely and easily flow-guided into the pulmonary artery. In this way continuous recordings of mixed venous oxygen tension (PvO2) could be made for a period of several days. In our experience a sustained fall of PvO2 below 40 mm Hg proved to be a reliable indicator of respiratory or cardiac deterioration not always obvious by observation. In the patients described, falls of this order were seen after reductions in inspired oxygen concentration, in acute respiratory failure, in accidental underventilation, and in hypovolaemia and cardiac arrythmias. In some very ill patients routine nursing care involving movement of the patient caused pronounced falls of PvO2. Although electrode drift was an occasional problem, this could be checked by intermittent blood-sampling and recalibration if necessary.

The central venous O2 saturation test in acute pulmonary fat embolism

1. The central venous oxygen saturation appears to be a reliable method of assessing the prognosis of patients with pulmonary fat embolism. 2. There was an inverse relationship to the A-a gradient and A-V oxygen difference in this group of patients. Further additional hemodynamic studies concomitantly with central venous oxygen saturation are being investigated. 3. The patients with depressed central venous oxygen saturation should be closely observed and diligently treated earlier, with combined respiratory and pharmacological therapy. 4. Such an approach might prevent the development of pulmonary fat embolism in traumatic patients.

On-line monitoring of mixed venous oxygen saturation after cardiothoracic surgery

On-line monitoring of MVo2 sat. in vivo by means of fibreoptic reflectometry was studied in 19 patients as to its predictive value during the postoperative course after thoracotomy for periods up to 60 hours. In all but one of the 10 patients with MVo2 sat. less than 65% for at least one hour complications occurred. A fall of MVo2 sat. of more than 5% or a value below 60% predicted a period of hypotension in six patients. In two of them this coincided with a period of ventricular arrhythmias. In those with MVo2 sat. greater than 65% no postoperative complications such as arrhythmias, shock, respiratory dysfunction or oliguria took place.