Cardiac index vs oxygen-derived parameters for rational use of dobutamine in patients with congestive heart failure

Primary intra-aortic balloon support versus inotropes for decompensated heart failure and low output: a randomised trial

AIMS

The haemodynamic effects of primary implantation of an intra-aortic balloon pump (IABP) versus inotropes in decompensated heart failure and low output (DHF-LO), but without an acute coronary syndrome, have not been investigated. We therefore aimed to investigate the effect of primary IABP implantation as compared to inotropes on haemodynamics in DHF-LO with no acute ischaemia.

METHODS AND RESULTS

Patients (n=32) with DHF-LO despite IV diuretics were randomised to primary 50 mL IABP or inotropes (INO: enoximone or dobutamine). The primary endpoint was the improvement of organ perfusion assessed by ∆ mixed-venous oxygen saturation (SvO2) at 3 hours; secondary endpoints included ∆ cardiac power output (CPO), NT-proBNP proportional change, cumulative fluid balance and ∆ dyspnoea severity score, all at 48 hours. Data are presented as median (IQR). Patients were 60 (48-69) years old and 72% were male. Baseline SvO2 was 44 (39-53)%. ∆SvO2 was higher in the IABP group (+17 [+9; +24] vs. +5 [+2; +9]%, p<0.05). IABP patients had a higher ∆CPO, a greater relative reduction in NT-proBNP, a more negative cumulative fluid balance, and a greater reduction in dyspnoea severity score. There were no IABP-related serious adverse events (SAEs). Thirty-day mortality was 23% (IABP) vs. 44% (INO).

CONCLUSIONS

Primary circulatory support by IABP showed a significant increase in improved organ perfusion assessed by SvO2.

Intravenous ivabradine versus placebo in patients with low cardiac output syndrome treated by dobutamine after elective coronary artery bypass surgery: a phase 2 exploratory randomized controlled trial

BACKGROUND

Low cardiac output syndrome (LCOS) is a severe condition which can occur after cardiac surgery, especially among patients with pre-existing left ventricular dysfunction. Dobutamine, its first-line treatment, is associated with sinus tachycardia. This study aims to assess the ability of intravenous ivabradine to decrease sinus tachycardia associated with dobutamine infused for LCOS after coronary artery bypass graft (CABG) surgery.

METHODS

In a phase 2, multi-center, single-blind, randomized controlled trial, patients with left ventricular ejection fraction below 40% presenting sinus tachycardia of at least 100 beats per minute (bpm) following dobutamine infusion for LCOS after CABG surgery received either intravenous ivabradine or placebo (three ivabradine for one placebo). Treatment lasted until dobutamine weaning or up to 48 h. The primary endpoint was the proportion of patients achieving a heart rate (HR) in the 80- to 90-bpm range. Secondary endpoints were invasive and non-invasive hemodynamic parameters and arrhythmia events.

RESULTS

Nineteen patients were included. More patients reached the primary endpoint in the ivabradine than in the placebo group (13 (93%) versus 2 (40%); P = 0.04). Median times to reach target HR were 1.0 h in the ivabradine group and 5.7 h in the placebo group. Ivabradine decreased HR (112 to 86 bpm, P <0.001) while increasing cardiac index (P = 0.02), stroke volume (P <0.001), and systolic blood pressure (P = 0.03). In the placebo group, these parameters remained unchanged from baseline. In the ivabradine group, five patients (36%) developed atrial fibrillation (AF) and one (7%) was discontinued for sustained AF; two (14%) were discontinued for bradycardia.

CONCLUSION

Intravenous ivabradine achieved effective and rapid correction of sinus tachycardia in patients who received dobutamine for LCOS after CABG surgery. Simultaneously, stroke volume and systolic blood pressure increased, suggesting a beneficial effect of this treatment on tissue perfusion.

TRIAL REGISTRATION

European Clinical Trials Database: EudraCT 2009-018175-14 . Registered February 2, 2010.

Hemodynamic effects of Ivabradine in addition to dobutamine in patients with severe systolic dysfunction

BACKGROUND

Dobutamine induced tachycardia increases myocardial oxygen consumption and impairs ventricular filling. We hypothesized that Ivabradine may be efficient to control dobutamine induced tachycardia.

METHODS

We assessed the effects of Ivabradine in addition to dobutamine in stable heart failure (HF) patients (LVEF < 35%, n = 22, test population) and validated its effects in refractory cardiogenic shock patients (n = 9, validation population) with contraindication to cardiac assistance or transplant. In the test population (62 ± 17 years, LVEF = 24 ± 8%), systolic and diastolic function were assessed at rest and under dobutamine [10 γ/min], before and after Ivabradine [5mg per os]. In the validation population (54 ± 11 years, LVEF = 22 ± 7%), Ivabradine [5mg twice a day] was added to the dobutamine infusion.

RESULTS

In the test population, Ivabradine decreased heart rate [HR] at rest and during dobutamine echocardiography (-9 ± 8 bpm, P = 0.0004). The decrease in HR was associated with a decrease in cardiac power output and an increase in diastolic duration at rest (+ 74 ± 67 ms, P = 0.0002), and during dobutamine infusion (+ 75 ± 67 ms, P < 0.0001). Change in LVEF during dobutamine was greater after Ivabradine treatment than before (+ 7.2 ± 4.7% vs. + 3.6 ± 4.2%, P = 0.002). In the validation population, Ivabradine decreased HR (-18 ± 11 bpm, P = 0.008) and improved diastolic filling time (+ 67 ± 42 ms, P = 0.012) without decreasing cardiac output. At 24h, Ivabradine improved systolic blood pressure (+ 9 ± 5 mmHg, P = 0.007), daily urine output (+ 0.7 ± 0.5L, P = 0.008), oxygen balance (ΔScv02 = + 13 ± 15%, P = 0.010), and NT-pro BNP (-2270 ± 1912 pg/mL, P = 0.017). Finally, only 2/9 (22%) patients died whereas expected mortality determined from a historical cohort was 78% (P = 0.017).

CONCLUSION

This pilot study demonstrates the safety and potential benefit of a HR lowering agent in cardiogenic shock.

Time course of central venous-to-arterial carbon dioxide tension difference in septic shock patients receiving incremental doses of dobutamine

PURPOSE

To assess the time course of the central venous-arterial carbon dioxide tension difference (∆PCO2)-as an index of the carbon dioxide production (VCO2)/cardiac index (CI) ratio-in stable septic shock patients receiving incremental doses of dobutamine.

METHODS

Twenty-two hemodynamically stable septic shock patients with no signs of global tissue hypoxia, as testified by normal blood lactate levels, were prospectively included. A dobutamine infusion was administered at a dose of up to 15 μg/kg/min in increments of 5 μg/kg/min every 30 min. Complete hemodynamic and gas measurements were obtained at baseline, and at each dose of dobutamine.

RESULTS

Dobutamine induced a significant dose-dependent increase of CI from 0 to 15 μg/kg/min (P < 0.001). Oxygen consumption (VO2) and VCO2 were progressively increased by dobutamine. These increases were more marked between 10 and 15 μg/kg/min (8.3 and 8.6 %, respectively) than between the lower doses. ∆PCO2 and oxygen extraction (EO2) significantly decreased between 0 (8.0 ± 2.0 mmHg and 43.8 ± 13.4 %, respectively) and 10 μg/kg/min of dobutamine (4.2 ± 1.6 mmHg and 28.9 ± 7.9 %, respectively), but remained unchanged from 10 to 15 μg/kg/min (5.4 ± 2.4 mmHg and 29.5 ± 8.2 %, respectively). The central venous oxygen saturation significantly (ScvO2) increased from 0 to 10 μg/kg/min and remained unchanged from 10 to 15 μg/kg/min. Time courses of ∆PCO2, ScvO2, and EO2 were linked therefore to the biphasic changes of VO2 and VCO2.

CONCLUSION

∆PCO2 is a good indicator of the change of VCO2 induced by dobutamine. Measurement of ∆PCO2, along with ScvO2 and EO2, may be presented as a useful tool to assess the adequacy of oxygen supply versus metabolic and oxygen demand.

Cardiac resynchronization therapy and AV optimization increase myocardial oxygen consumption, but increase cardiac function more than proportionally

BACKGROUND

The mechanoenergetic effects of atrioventricular delay optimization during biventricular pacing ("cardiac resynchronization therapy", CRT) are unknown.

METHODS

Eleven patients with heart failure and left bundle branch block (LBBB) underwent invasive measurements of left ventricular (LV) developed pressure, aortic flow velocity-time-integral (VTI) and myocardial oxygen consumption (MVO2) at 4 pacing states: biventricular pacing (with VV 0 ms) at AVD 40 ms (AV-40), AVD 120 ms (AV-120, a common nominal AV delay), at their pre-identified individualised haemodynamic optimum (AV-Opt); and intrinsic conduction (LBBB).

RESULTS

AV-120, relative to LBBB, increased LV developed pressure by a mean of 11(SEM 2)%, p=0.001, and aortic VTI by 11(SEM 3)%, p=0.002, but also increased MVO2 by 11(SEM 5)%, p=0.04. AV-Opt further increased LV developed pressure by a mean of 2(SEM 1)%, p=0.035 and aortic VTI by 4(SEM 1)%, p=0.017. MVO2 trended further up by 7(SEM 5)%, p=0.22. Mechanoenergetics at AV-40 were no different from LBBB. The 4 states lay on a straight line for Δexternal work (ΔLV developed pressure × Δaortic VTI) against ΔMVO2, with slope 1.80, significantly >1 (p=0.02).

CONCLUSIONS

Biventricular pacing and atrioventricular delay optimization increased external cardiac work done but also myocardial oxygen consumption. Nevertheless, the increase in cardiac work was ~80% greater than the increase in oxygen consumption, signifying an improvement in cardiac mechanoenergetics. Finally, the incremental effect of optimization on external work was approximately one-third beyond that of nominal AV pacing, along the same favourable efficiency trajectory, suggesting that AV delay dominates the biventricular pacing effect - which may therefore not be mainly "resynchronization".

Lactate and venoarterial carbon dioxide difference/arterial-venous oxygen difference ratio, but not central venous oxygen saturation, predict increase in oxygen consumption in fluid responders

OBJECTIVES

During circulatory failure, the ultimate goal of treatments that increase cardiac output is to reduce tissue hypoxia. This can only occur if oxygen consumption depends on oxygen delivery. We compared the ability of central venous oxygen saturation and markers of anaerobic metabolism to predict whether a fluid-induced increase in oxygen delivery results in an increase in oxygen consumption.

DESIGN

Prospective study.

SETTING

ICU.

PATIENTS

Fifty-one patients with an acute circulatory failure (78% of septic origin).

MEASUREMENTS

Before and after a volume expansion (500 mL of saline), we measured cardiac index, o2- and Co2-derived variables and lactate.

MAIN RESULTS

Volume expansion increased cardiac index ≥ 15% in 49% of patients ("volume-responders"). Oxygen delivery significantly increased in these 25 patients (+32% ± 16%, p < 0.0001). An increase in oxygen consumption ≥ 15% concomitantly occurred in 56% of these 25 volume-responders (+38% ± 28%). Compared with the volume-responders in whom oxygen consumption did not increase, the volume-responders in whom oxygen consumption increased ≥ 15% were characterized by a higher lactate (2.3 ± 1.1 mmol/L vs. 5.5 ± 4.0 mmol/L, respectively) and a higher ratio of the veno-arterial carbon dioxide tension difference (P(v - a)Co2) over the arteriovenous oxygen content difference (C(a - v)o2). A fluid-induced increase in oxygen consumption greater than or equal to 15% was not predicted by baseline central venous oxygen saturation but by high baseline lactate and (P(v - a)Co2/C(a - v)o2 ratio (areas under the receiving operating characteristics curves: 0.68 ± 0.11, 0.94 ± 0.05, and 0.91 ± 0.06). In volume-nonresponders, volume expansion did not significantly change cardiac index, but the oxygen delivery decreased due to a hemodilution-induced decrease in hematocrit.

CONCLUSIONS

In volume-responders, unlike markers of anaerobic metabolism, central venous oxygen saturation did not allow the prediction of whether a fluid-induced increase in oxygen delivery would result in an increase in oxygen consumption. This suggests that along with indicators of volume-responsiveness, the indicators of anaerobic metabolism should be considered instead of central venous oxygen saturation for starting hemodynamic resuscitation.

Hemodynamic management of cardiovascular failure by using PCO(2) venous-arterial difference

The difference between mixed venous blood carbon dioxide tension (PvCO(2)) and arterial carbon dioxide tension (PaCO(2)), called ∆PCO(2) has been proposed to better characterize the hemodynamic status. It depends on the global carbon dioxide (CO(2)) production, on cardiac output and on the complex relation between CO(2) tension and CO(2) content. The aim of this review is to detail the physiological background allowing adequate interpretation of ∆PCO(2) at the bedside. Clinical and experimental data support the use of ∆PCO(2) as a valuable help in the decision-making process in patients with hemodynamic instability. The difference between central venous CO(2) tension and arterial CO(2) tension, which is easy to obtain can substitute for ∆PCO(2) to assess the adequacy of cardiac output. Differences between local tissue CO(2) tension and arterial CO(2) tension can also be obtained and provide data on the adequacy of local blood flow to the local metabolic conditions.

Optimizing hemodynamic support in septic shock using central and mixed venous oxygen saturation

Global tissue hypoxia is one of the most important factors in the development of multisystem organ dysfunction. In hemodynamically unstable critically ill patients, central venous oxygen saturation (Scvo(2)) and mixed venous oxygen saturation (Svo(2)) monitoring has been shown to be a better indicator of global tissue hypoxia than vital signs and other clinical parameters alone. Svo(2) is probably more representative of global tissue oxygenation, whereas Scvo(2), is less invasive. Svo(2) and Scvo(2) monitoring can have diagnostic and therapeutic uses in understanding the efficacy of interventions in treating critically ill, hemodynamically unstable patients.

Effects of short-term simultaneous infusion of dobutamine and terlipressin in patients with septic shock: the DOBUPRESS study

BACKGROUND

Terlipressin bolus infusion may reduce cardiac output and global oxygen supply. The present study was designed to determine whether dobutamine may counterbalance the terlipressin-induced depression in mixed-venous oxygen saturation (Svo) in patients with catecholamine-dependent septic shock.

METHODS

Prospective, randomized, controlled study performed in a university hospital intensive care unit. Septic shock patients requiring a continuous infusion of norepinephrine (0.9 microg kg(-1) min(-1)) to maintain mean arterial pressure (MAP) at 70 (sd 5) mm Hg were randomly allocated to be treated either with (i) sole norepinephrine infusion (control, n=20), (ii) a single dose of terlipressin 1 mg (n=19), or (iii) a single dose of terlipressin 1 mg followed by dobutamine infusion titrated to reverse the anticipated reduction in Svo2 (n=20). Systemic, pulmonary, and regional haemodynamic variables were obtained at baseline and after 2 and 4 h. Laboratory surrogate markers of organ (dys)function were tested at baseline and after 12 and 24 h.

RESULTS

Terlipressin (with and without dobutamine) infusion preserved MAP at 70 (5) mm Hg, while allowing to reduce norepinephrine requirements to 0.17 (0.2) and 0.2 (0.2) microg kg(-1) min(-1), respectively [vs1.4 (0.3) microg kg(-1) min(-1) in controls at 4 h; each P<0.001]. The terlipressin-linked decrease in Svo2 was reversed by dobutamine at a mean dose of 20 (8) microg kg(-1) min(-1) [Svo2 at 4 h: 59 (11)% vs 69 (12)%, P=0.028].

CONCLUSIONS

In human catecholamine-dependent septic shock, terlipressin (with and without concomitant dobutamine infusion) increases MAP and markedly reduces norepinephrine requirements. Although no adverse events were noticed in the present study, potential benefits of increasing Svo2 after terlipressin bolus infusion need to be weighted against the risk of cardiovascular complications resulting from high-dose dobutamine.

The cardiopulmonary effects of dobutamine and norepinephrine in isoflurane-anesthetized foals

OBJECTIVE

To evaluate the cardiovascular effects of norepinephrine (NE) and dobutamine (DB) in isoflurane-anesthetized foals.

STUDY DESIGN

Prospective laboratory study.

METHODS

Norepinephrine (0.05, 0.10, 0.20, and 0.40 microg kg(-1) minute(-1)) and dobutamine (2.5, 5.0, and 10 microg kg(-1) minute(-1)) were alternately administered to seven healthy, 1- to 2-week-old isoflurane-anesthetized foals. Arterial and pulmonary arterial blood pressure, right atrial pressure, pulmonary artery occlusion pressure, heart rate, body temperature, cardiac output, arterial and mixed venous blood pH, partial pressure of carbon dioxide, partial pressure of oxygen [arterial partial pressure of oxygen (PaO(2)) and mixed venous partial pressure of oxygen (PvO(2))], and packed cell volume were measured. Standard base excess, bicarbonate concentration, systemic and pulmonary vascular resistance, cardiac index (CI), stroke volume, left and right stroke work indices, oxygen delivery (DO(2)), consumption, and extraction were calculated. Results Norepinephrine infusion resulted in significant increases in arterial and pulmonary arterial pressure, systemic and pulmonary vascular resistance indices, and PaO(2); heart rate was decreased. Dobutamine infusion resulted in significant increases in heart rate, stroke volume index, CI, and arterial and pulmonary arterial blood pressure. Systemic and pulmonary vascular resistance indices were decreased while the ventricular stroke work indices increased. The PaO(2) decreased while DO(2) and oxygen consumption increased. Oxygen extraction decreased and PvO(2) increased.

CONCLUSIONS AND CLINICAL RELEVANCE

Norepinephrine primarily augments arterial blood pressure while decreasing CI. Dobutamine primarily augments CI with only modest increases in arterial blood pressure. Both NE and DB could be useful in the hemodynamic management of anesthetized foals.

Changes in regional blood flow and pCO2 gradients during isolated abdominal aortic blood flow reduction

OBJECTIVE

pCO(2) gradients are used for the assessment of splanchnic regional and local mucosal blood flow changes in experimental and clinical research. pCO(2) gradients may not parallel blood flow changes because of concomitant changes in metabolism, hemoglobin, temperature, and the Haldane effect.

DESIGN AND SETTING

A randomized, controlled animal experiment in a university experimental research laboratory.

INTERVENTIONS

An extracorporeal shunt with reservoir and roller pump was inserted between the proximal and the distal abdominal aorta in 16 pigs. In animals randomized to the low-flow group ( n=8) splanchnic perfusion was reduced by running the roller pump. At baseline and after 45 min of stable shunt flow superior mesenteric artery, celiac trunk, spleen artery, and portal vein blood flows and regional venous-arterial and jejunal and gastric mucosal-arterial pCO(2) gradients were measured, and the respective regional O(2) consumption rates (VO(2)) calculated.

MEASUREMENTS AND RESULTS

In the low-flow group all regional blood flows and the associated VO(2) decreased to roughly 50% of baseline values, and hemoglobin decreased from 7.3 (4.4-9.6) g/dl to 5.7 (4.1-8.9) g/dl. Decreasing regional blood flows were consistently associated with increasing regional and mucosal pCO(2) gradients.

CONCLUSIONS

During isolated reduction in abdominal aortic blood flow there is no preferential distribution to any splanchnic vascular bed and changes in regional pCO(2) gradients reflect consistently the associated blood blow changes.

Perioperative optimization and right heart catheterization: what technique in which patient?

Recent years have seen the place of the pulmonary artery catheter in intensive care increasingly challenged, with one recent study reporting no difference in outcome in patients treated with or without a pulmonary artery catheter. However, this study has several methodological flaws and, although pulmonary artery catheterization should not be performed routinely on all patients, when used correctly by trained personnel in selected patients the pulmonary artery catheter continues to provide valuable information.

Left ventricular or biventricular pacing improves cardiac function at diminished energy cost in patients with dilated cardiomyopathy and left bundle-branch block

BACKGROUND

Left ventricular or biventricular pacing/stimulation can acutely improve systolic function in patients with dilated cardiomyopathy (DCM) and intraventricular conduction delay by resynchronizing contraction. Most heart failure therapies directly enhancing systolic function do so while concomitantly increasing myocardial oxygen consumption (MVO(2)). We hypothesized that pacing/stimulation, in contrast, incurs systolic benefits without raising energy demand.

METHODS AND RESULTS

Ten DCM patients with left bundle-branch block (ejection fraction 20+/-3%, QRS duration 179+/-3 ms, mean+/-SEM) underwent cardiac catheterization to measure ventricular and aortic pressure, coronary blood flow, arterial-coronary sinus oxygen difference (DeltaAVO(2)), and MVO(2). Data were measured under sinus rhythm or with left ventricular or biventricular pacing/stimulation at the same heart rate. These results were then contrasted to intravenous dobutamine (n=7) titrated to match systolic changes during LV pacing. Systolic function rose quickly and substantially from LV pacing (18+/-4% rise in arterial pulse pressure, which correlates with cardiac output, and 43+/-6% increase in dP/dt(max); both P<0.01). However, DeltaAVO(2) and MVO(2) declined -4+/-2% and -8+/-6.5%, respectively (both P<0.05). Similar results were obtained with biventricular activation. In contrast, dobutamine raised dP/dt(max) 37+/-6%, accompanied by a 22+/-11% rise in per-beat MVO(2) (P<0.05 versus pacing).

CONCLUSIONS

Ventricular resynchronization by left ventricular or biventricular pacing/stimulation in DCM patients with left bundle-branch block acutely enhances systolic function while modestly lowering energy cost. This should prove valuable for treating DCM patients with basal dyssynchrony.

Value of the venous-arterial PCO2 gradient to reflect the oxygen supply to demand in humans: effects of dobutamine

OBJECTIVE

To test the value of venous-arterial PCO2 gradient (deltaPCO2) measurements to reflect the adequacy of cardiac index (CI) to oxygen demand in patients submitted to rapid changes of CI and oxygen demand.

DESIGN

Prospective, comparative study.

SETTING

Medical intensive care unit of a university hospital.

PATIENTS

Ten patients with congestive heart failure exhibiting low baseline CI (< or =2.5 L/min/m2) but no evidence of global tissue hypoxia, as attested by the absence of clinical signs of shock and by normal blood lactate concentrations.

INTERVENTIONS

Infusion of incremental doses of dobutamine: 0 (D0), 5 (D5), 10 (D10), and 15 (D15) microg/kg/min.

MEASUREMENTS AND MAIN RESULTS

The CI increased by a linear fashion from D0 (1.6+/-0.1 L/min/m2) to D15 (2.4+/-0.2 L/min/m2) (p< .05). The mixed venous oxygen saturation (SVO2) increased from D0 (49+/-2%) to D10 (61+/-2%) (p < .05) and remained unchanged from D10 to D15 (60+/-2%). The oxygen extraction ratio (O2 ER) and the deltaPCO2 decreased from D0 (48+/-2% and 9+/-1 torr [1.2+/-0.3 kPa], respectively) to D10 (36+/-2% and 5+/-1 torr [0.7+/-0.1 kPa], respectively) (p < .05 for both comparisons) and remained unchanged from D10 to D15 (36+/-2% and 6+/-1 torr [0.8+/-0.1 kPa], respectively). The biphasic courses of SVO2, O2 ER, and deltaPCO2 were related to the course of oxygen consumption that remained constant from D0 (113+/-9 mL/min/m2) to D10 (112+/-8 mL/min/m2) and significantly increased from D10 to D15 (127+/-10 mL/min/m2) (p <.05).

CONCLUSIONS

deltaPCO2 can be reliably used at the bedside for informing on the adequacy of CI with respect to a given metabolic condition, and particularly for detecting changes in oxygen demand (e.g., the changes accompanying drug-induced changes in CI). In this regard, deltaPCO2, together with O2 ER and SVO2, can help to assess the adequacy of CI to global oxygen demand.

Comparison between mixed venous oxygen saturation and thermodilution cardiac output in monitoring patients with severe heart failure treated with milrinone and dobutamine

PURPOSE

Although thermodilution cardiac output (COtd) is the accepted method for monitoring patients with heart failure in the intensive care unit, it is particularly inaccurate in low-flow states and in the presence of tricuspid regurgitation; in addition, it does not adequately reflect the interaction between oxygen delivery and tissue oxygen extraction. We were concerned about the underuse of mixed venous oxygen saturation (SvO2) in this setting and hypothesized that it might be a more useful parameter than COtd for evaluating hemodynamic status and monitoring therapy in patients with severe congestive heart failure.

PATIENTS AND METHODS

We determined the correlation coefficients between increasing dose of inotrope and each of the parameters COtd and SvO2 in 18 patients with congestive heart failure who received a 3-day trial of either milrinone or dobutamine during admission to the Veterans Affairs Medical Center in San Diego. In addition, we analyzed reproducibility of repeated COtd and SvO2 measurements taken at a single dose of inotrope.

RESULTS

In patients receiving milrinone the increase in dose correlated much better with SvO2 (average correlation coefficient 0.79) than with COtd; this stronger correlation with SvO2 was seen in 82% of the trials reviewed (p < 0.05). In addition, we found that repeated SvO2 measurements taken at a single dose of milrinone were more reproducible than COtd as indicated by smaller relative 95% confidence intervals. In patients receiving dobutamine no significant trend in correlation coefficients or reproducibility was observed.

CONCLUSION

The knowledge that there is a significant relation between SvO2 and increasing dose of milrinone therapy in patients with severe heart failure and tricuspid regurgitation has practical value for physicians monitoring these patients in the intensive care unit. We believe this study demonstrates the worth of SvO2 in detecting hemodynamic change during trials of milrinone therapy and that this parameter may in fact be more reproducible than traditional thermodilution methods.

Resuscitation of the critically ill in the ED: responses of blood pressure, heart rate, shock index, central venous oxygen saturation, and lactate

To describe the simultaneous responses of systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial blood pressure (MAP), heart rate (HR), shock index (SI = HR/SBP), central venous oxyhemoglobin saturation (ScvO2), and arterial blood lactate concentration (Lact) to resuscitation of critically ill patients in the emergency department (ED), an observational descriptive study was conducted in the ED of an urban teaching hospital. Thirty- six patients admitted from the ED to the medical intensive care unit were studied. Vital signs were measured immediately on arrival to the ED (phase 1). After initial resuscitation and stabilization, ie, HR between 50 and 120 beats/min and MAP between 70 and 110 mm Hg (phase 2), ScvO2 and Lact were measured and additional therapy was given in the ED to increase ScvO2 to > 65% and decrease Lact to < 2 mmol/L, if needed (phase 3). SBP, DBP, MAP, HR. SI, ScvO2, and Lact were measured. Initial resuscitation increased SBP from 103 +/- 39 to 118 +/- 29 mm Hg (P < .05) and MAP from 67 +/- 35 to 82 +/- 22 mm Hg (P < .05) but did not affect DBP (53 +/- 35 to 63 +/- 22 mm Hg, P = NS), HR (110 +/- 26 to 110 +/- 22 beats/min, P = NS) or SI (from 1.3 +/- 0.7 to 1.0 +/- 0.3, P =NS) from phase 1 to phase 2. ScvO2 remained < 65% and/or Lact > 2.0 mmol/L in 31 of 36 patients at phase 2, and additional therapy was required. Lact was decreased (from 4.6 +/- 3.8 to 2.6 +/- 2.5 mmol/L, P < .05) and ScvO2 was increased (from 52 +/- 18 to 65 +/- 13%, P < .05) without significant additional changes in SBP, DBP, MAP, HR, or SI at phase 3. The in-hospital mortality was 14% for this group of patients. It was concluded that additional therapy is required in the majority of critically ill patients to restore adequate systemic oxygenation after initial resuscitation and hemodynamic stabilization in the ED. Additional therapy to increase ScvO2 and decrease Lact may not produce substantial responses in SBP, DBP, MAP, HR, and SI. The measurement of ScvO2 and Lact can be utilized to guide this phase of additional therapy in the ED.

Initial experience with an implantable hemodynamic monitor

BACKGROUND

Measurement of intracardiac hemodynamic parameters has been limited to brief periods in the acute care setting. We developed and evaluated an implantable hemodynamic monitor that is capable of measuring chronic right ventricular oxygen saturation and pulmonary artery pressure.

METHODS AND RESULTS

The device consists of an electronic controller placed subcutaneously and two transvenous leads placed in the right ventricle (reflectance oximeter) and pulmonary artery (variable capacitance pressure sensor). Implantation was performed in 10 patients with severe left ventricular dysfunction. Average implant pulmonary artery pressures were systolic, 52 +/- 16 mm Hg; diastolic, 29 +/- 11 mm Hg; and mean, 40 +/- 12 mm Hg. The mean right ventricular oxygen saturation at implant was 51%. Provocative maneuvers, including postural changes, sublingual nitroglycerin, and bicycle exercise, demonstrated expected changes in measured oxygen saturation and pulmonary artery pressures over time. At follow-up of 0.5 to 15.5 months, there were no significant differences between pulmonary artery pressures or oxygen saturation values transmitted from the device and simultaneous measurement with balloon flotation catheters. Four of the pulmonary artery leads dislodged and three demonstrated sensor drift, whereas two of the oxygen saturation sensors failed. Four patients died and four received transplants. Pathological study did not demonstrate injury to the right ventricular outflow tract or pulmonic valve.

CONCLUSIONS

Chronic measurement of hemodynamic parameters in the outpatient setting with implantable sensor technology appears to be feasible. The devices are well tolerated without significant untoward effects, and the sensors generally function well over time, providing reliable information. Clinical usefulness remains to be established.

Triage of critically ill patients: an overview of interventions

The recognition of tissue hypoxia or cumulative oxygen debt is of fundamental importance for triage and resuscitation of critically ill patients during the ¿golden hour¿ in the emergency department (ED). The measurement of central venous blood oxygen saturation, plasma lactate concentration, cardiac output, systemic oxygen transport and use, and non-vital organ oxygenation and function can enhance the detection of systemic and regional hypoperfusion and tissue hypoxia. Systemic and organ-specific oxygenation indices may guide the choice of therapy to optimize resuscitation of the macrocirculation and microcirculation in critically ill ED patients.

Oxygen uptake/oxygen supply dependency: fact or fiction?

More than a decade ago, observations of co-variance between VO2 and DO2 led to the identification of a condition known as pathological O2 supply dependency. This condition was subsequently observed in critically ill patients with sepsis and acute circulatory failure. More recently, other authors have challenged the existence of this condition, often citing methodologic problems or mathematical coupling to account for spurious observations in the earlier studies. Here, we review the evidence for and against pathological O2 supply dependency. We find that many of the arguments have some validity but only in specific circumstances. We conclude, therefore, that pathological O2 supply dependency is a hallmark of acute circulatory failure and that an effective therapeutic approach should be based on an evaluation of organ system function in each individual case. Parameters such as blood lactate, pHi and veno-arterial PCO2 may be useful in this respect.

Congestive heart failure and pulmonary edema for the emergency physician

Congestive heart failure (CHF) and pulmonary edema are major health problems in the United States as well as across the rest of the developing world. The prevalence of CHF and pulmonary edema in the general population results in a significant number of these patients presenting to Emergency Departments (EDs). Mortality from these disorders is substantial, with a 5-year mortality rate for patients requiring hospitalization of approximately 50%. Understanding of the clinical syndromes of CHF and pulmonary edema requires review of the basic determinants of cardiovascular performance. Preload, afterload, contractility, and heart rate may all be modified by pharmacological or mechanical techniques. Diuretics, vasodilators, cardiac glycosides, and other inotropes all may play a role in the ED management of CHF. In rare instances, mechanical devices for support of the heart and circulation may be indicated.

Patterns of systemic oxygen utilization in cardiac ischemic syndromes: oxygen utilization in cardiac ischemia

Cardiac ischemia can present as distinctive clinical syndromes such as acute myocardial infarction, cardiogenic shock, sudden cardiac arrest or chronic congestive heart failure. All of the clinical syndromes share common pathophysiological events including reduction of cardiac output and systemic oxygen delivery (DO2) and activation of neurohumoral stress response. The balance between systemic DO2 and oxygen consumption (VO2) is maintained by modification of systemic oxygen utilization and demands which are essential for tissue viability and survival in cardiac ischemic syndromes. Low blood flow and the neurohumoral response may influence cellular metabolism (e.g., acute ischemia preconditioning and chronic downregulation of aerobic metabolism) and microcirculatory perfusion patterns to decrease systemic oxygen demands and VO2 in harmony with low cardiac output and systemic DO2. The clinical relevance of these metabolic adaptations and their influence on the outcome in cardiac ischemic syndromes remains unknown.

Characterization of systemic oxygen transport in end-stage chronic congestive heart failure

Chronic congestive heart failure (CHF) is characterized by low cardiac index (CI) and low systemic oxygen delivery (DO2), which frequently are associated with lethal cardiogenic shock after acute myocardial infarction. Nevertheless, patients with severe CHF are able to survive with these low levels of systemic DO2 and CI. It was hypothesized that patients with CHF survive low CI and DO2 by downregulation of global metabolism and resting oxygen consumption (VO2) and a concomitant increase in systemic oxygen extraction ratio (O2ER). Therefore the objective of this study was to characterize the resting pattern of systemic oxygen transport (O2T) and utilization in patients with stable CHF. Seventeen patients with CHF (New York Heart Association functional class III or IV) for > or = 3 months and with left ventricular ejection fraction (EF) < 25% and whose condition was stable with conventional oral therapy were studied. The control group comprised 10 subjects (NYHA class I) who had coronary angiography and who were found to have normal left ventricular function and EF > 60%. Subjects underwent right-heart catheterization for measurement and calculation of hemodynamic and O2T variables (VO2, DO2, and O2ER). There were no significant differences in mean age (67 +/- 6 vs 64 +/- 17 years) or gender ratio (male:female 14:3 vs 7:3) between CHF and control groups, respectively. The cause of CHF was ischemic in 13 and idiopathic in 4 patients. There were 9 patients in NYHA class III and 8 in class IV.(ABSTRACT TRUNCATED AT 250 WORDS)