Using oxygen delivery targets to optimize resuscitation in critically ill patients

A performance comparison of the most commonly used minimally invasive monitors of cardiac output

BACKGROUND

Shock is common in critically ill and injured patients. Survival during shock is highly dependent on rapid restoration of tissue oxygenation with therapeutic goals based on cardiac output (CO) optimization. Despite the clinical availability of numerous minimally invasive monitors of CO, limited supporting performance data are available.

METHODS

Following approval of the University of Saskatchewan Animal Research Ethics Board, we assessed the performance and trending ability of PiCCOplus™, FloTrac™, and CardioQ-ODM™ across a range of CO states in pigs. In addition, we assessed the ability of invasive mean arterial blood pressure (iMAP) to follow changes in CO using a periaortic transit-time flow probe as the reference method. Statistical analysis was performed with function-fail, bias and precision, percent error, and linear regression at all flow, low-flow (> 1 standard deviation [SD] below the mean), and high-flow (> 1 SD above the mean) CO conditions.

RESULTS

We made a total of 116,957 paired CO measurements. The non-invasive CO monitors often failed to provide a CO value (CardioQ-ODM: 40.6% failed measurements; 99% confidence interval [CI], 38.5 to 42.6; FloTrac: 9.6% failed measurements; 99% CI, 8.7 to 10.5; PiCCOplus: 4.7% failed measurements; 99% CI, 4.5 to 4.9; all comparisons, P < 0.001). The invasive mean arterial pressure provided zero failures, failing less often than any of the tested CO monitors (all comparisons, P < 0.001). The PiCCOplus was most interchangeable with the flow probe at all flow states: PiCCOplus (20% error; 99% CI, 19 to 22), CardioQ-ODM (25% error; 99% CI, 23 to 27), FloTrac (34% error; 99% CI, 32 to 38) (all comparisons, P < 0.001). At low-flow states, CardioQ-ODM (43% error; 99% CI, 32 to 63) and Flotrac (45% error; 99% CI, 33 to 70) had similar interchangeability (P = 0.07), both superior to PiCCOplus (48% error; 99% CI, 42 to 60) (P < 0.001). Regarding CO trending, the CardioQ-ODM (correlation coefficient, 0.82; 99% CI, 0.81 to 0.83) was statistically superior to other monitors including iMAP, but at low flows iMAP (correlation coefficient, 0.58; 99% CI, 0.58 to 0.60) was superior to all minimally invasive CO monitors (all comparisons P < 0.001).

CONCLUSIONS

None of the minimally invasive monitors of CO performed well at all tested flows. Invasive mean arterial blood pressure most closely tracked CO change at critical flow states.

Microcirculatory alterations during continuous renal replacement therapy in ICU: A novel view on the 'dialysis trauma' concept

OBJECTIVE

The purpose of this study was to evaluate microcirculation over 24 h renal replacement therapy (CRRT) in critically ill patients.

METHODS

We conducted a single-center, prospective, observational study, measuring microcirculation parameters, monitored by near infrared spectroscopy (NIRS) before hemodiafiltration onset (H0), and at six (H6) and 24 h (H24) during CRRT in critically ill patients. Serum Cystatin C (sCysC) and soluble (s)E-selectin levels were measured at the same time points. Twenty-eight patients [19 men (68%)] were included in the study.

RESULTS

Tissue oxygen saturation (StO2, %) [76.5 ± 12.5 (H0) vs 75 ± 11 (H6) vs 70 ± 16 (H24), p = 0.04], reperfusion rate, indicating endothelial function (EF, %/sec) [2.25 ± 1.44 (H0) vs 2.1 ± 1.8 (H6) vs 1.6 ± 1.4 (H24), p = 0.02] and sCysC (mg/L) [2.7 ± 0.8 (H0) vs 2.2 ± 0.6 (H6) vs 1.8 ± 0.8 (H24), p < 0.0001] significantly decreased within the 24 h CRRT. Change of EF positively correlated with changes of sCysC within 24 h CRRT (r = 0.464, p = 0.013) while in patients with diabetes the change of StO2 correlated with dose (r = − 0.8, p = 0.01). No correlation existed between hemoglobin and temperature changes with the deteriorated microcirculation indices. sE-Selectin levels in serum were elevated; no difference was established over the 24 h CRRT period. A strong correlation existed between the sE-Selectin concentration change at H6 and H24 and the mean arterial pressure change in the same period (r = 0.77, p < 0.001).

CONCLUSIONS

During the first 24 h of CRRT implementation in critically ill patients, deterioration of microcirculation parameters was noted. Microcirculatory alterations correlated with sCysC changes and with dose in patients with diabetes.

Early management of the severely injured major trauma patient

The major trauma team relies on an efficient, communicative team to ensure patients receive the best quality care. This requires a comprehensive handover, rapid systematic review, and early management of life- and limb-threatening injuries. These multiple injured patients often present with complex conditions in a dynamic situation. The importance of team work, communication, senior decision-making, and documentation cannot be underestimated.

Assessment of global tissue perfusion and oxygenation in neonates and infants after open-heart surgery

OBJECTIVES

Monitoring and preserving adequate perfusion and oxygen balance is a primary objective of critical care. This prospective observational study aimed to assess the relationship between global haemodynamic parameters and variables reflecting tissue oxygenation during the early period following corrective cardiac surgery in neonates and infants. The postoperative time course of oxygen delivery and consumption was evaluated. As surrogate markers of oxygen balance, the central venous oxygen saturation (ScvO2) and venoarterial PCO2 difference (PvaCO2) were thoroughly investigated.

METHODS

Thirteen children <1 year of age who underwent open-heart surgery were prospectively enrolled. In addition to conventional postoperative monitoring, transpulmonary thermodilution (TPTD) was used to monitor cardiac output and calculate oxygen delivery and consumption. In parallel with each TPTD measurement, arterial and central venous blood gas values were recorded. Global haemodynamic parameters and oxygenation measurements were compared with weighted linear regression statistics and Pearson's correlation coefficient.

RESULTS

Data from 145 TPTD measurements and 304 blood gas samples were recorded. The early postoperative period was characterized by a supply-dependent oxygen consumption, as demonstrated by the direct correlation between the change in oxygen delivery and consumption (r = 0.62, P < 0.001). Regarding haemodynamic parameters, none of the heart rate, mean arterial pressure or cardiac index correlated with the measured ScvO2. However, the ScvO2 and PvaCO2 were found to correlate significantly (r = -0.49, P < 0.001), and both strongly related to oxygen extraction.

CONCLUSIONS

Both the ScvO2 and PvaCO2 are reliable and comparable parameters in following tissue oxygen balance during the early postoperative course after open-heart surgery in neonates and infants. As part of multiparameter monitoring, our data highlight the importance of regular ScvO2 measurements and PvaCO2 calculations in paediatric intensive care.

Non-invasive cardiac output and oxygen delivery measurement in an infant with critical anemia

OBJECTIVE

To assess the combination of a non-invasive blood oxygen content (CaO(2)) monitor and a non-invasive cardiac output (CO) monitor to continuously measure oxygen delivery (DO(2); DO(2) = CaO(2) × CO).

METHODS

DO(2) was assessed during blood transfusions in an infant with acute hemolytic anemia following admission (~48 h). CaO(2) was measured by Pulse Co-Oximetry, which also provides estimates of hemoglobin (Hgb) concentration and percent oxygen saturation. CO was measured by Electrical Velocimetry, which also provides an estimate of stroke volume (SV). Lactate levels, an indirect measure of adequate DO(2), were assessed during the initial 8 h following admission.

RESULTS

Incremental blood transfusions during the first 36 h increased Hgb from 2.7 to 9.5 g/dL during which time heart rate (HR) normalized from 156 to 115 beats/min. Lactate levels decreased from 20 to 0.8 mmol/L in the first 7 h. Non-invasive Hgb and CaO(2) measurements were well correlated with invasive Hgb and CaO(2) measures (r (2) = 0.88; P = 0.019; r (2) = 0.86; P = 0.0074, respectively). CO decreased from 2.47 ± 0.06 to 1.28 ± 0.02 L/min and SV decreased from 15.9 ± 0.4 to 11.1 ± 0.2 mL/beat. Mean arterial blood pressure was stable throughout the admission with systemic vascular resistance increasing from 407.6 ± 15.2 to 887.7 ± 30.1 dynes-s/cm(5). DO(2) was estimated to increase from 120.2 ± 18.9 to 182.4 ± 5.6 mL O(2)/min.

CONCLUSIONS

Non-invasive continuous CO and CaO(2) monitors are shown in this single case to provide continuous DO(2) measurement. The ability to assess DO(2) may improve hemodynamic monitoring during goal directed therapies.

Double ECMO in severe ARDS: report of an outstanding case and literature review

We report on a 49-year-old male patient who suffered from severe herpes simplex (HSV) pneumonia after a fall-from-height injury, causing a circumscript type B aortic dissection.The subsequent occurrence of ARDS required a veno-venous ECMO circuit that was upgraded to a veno-arterial system due to further oxygenation deficits. Following continued respiratory deterioration, the ECMO system already in place had to be complemented by a second veno-arterial line. After the onset of recovery and because of a developing of a disseminated intravasal coagulation, the double ECMO circuit was replaced by a pumpless extracorporeal lung assist system (PECLA). The patient recovered completely under systemic virostatic therapy.