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Introduction: The contribution of fluid temperature to the effect of crystalloid fluid bolus therapy (FBT) in post-cardiac surgery patients is unknown. We evaluated the hemodynamic effects of FBT with fluid warmed to 40°C (warm FBT) versus room-temperature fluid. Methods: In this single centre prospective before-and-after study, we evaluated the effects of 500 ml of warm versus room-temperature compound sodium lactate administered over <30 minutes, in 50 cardiac surgery patients admitted to ICU. We recorded hemodynamics continuous before and for 30 minutes after the first FBT. We defined CI responsiveness (CI-R) as an CI increase >15% of baseline immediately after FBT and effect dissipation if the CI returned to <5% of baseline and MAP responsiveness as >10% increase and dissipation as return to <3 mmHg of baseline. Results: Hypotension (56%) and low CI (40%) typically triggered FBT. Temperature decreased >0.3°C in 13 (52%) patients after room-temperature FBT versus 0 (0%) after warm FBT (p < 0.01). CI and MAP responsiveness was similar (16 [64%] versus 11 [44%], p = 0.15 and 15 [60%] versus 17 [68%], p = 0.77, respectively). Among CI responders, CI increased more with room-temperature FBT (+0.6 [IQR, 0.5–1.1] versus +0.5 [IQR, 0.4–0.6] L/min/m2, p = 0.01). However, dissipation was more common after room-temperature versus warm FBT (9/16 [56%] versus 1/11 [9%], p = 0.02). Conclusion: In postoperative cardiac surgery patients, warm FBT preserved core temperature and induced smaller but more sustained CI increases among responders. Fluid temperature appears to impact both core temperature and the duration of CI response. [ABSTRACT FROM AUTHOR]

To test whether targeted therapeutic mild hypercapnia (TTMH) would attenuate cerebral oxygen desaturation detected using near-infrared spectroscopy during cardiac surgery requiring cardiopulmonary bypass (CPB). Randomized controlled trials. Operating rooms and intensive care unit of tertiary hospital. The study comprised 30 patients undergoing cardiac surgery with CPB. Patients were randomly assigned to receive either standard carbon dioxide management (normocapnia) or TTMH (target arterial carbon dioxide partial pressure between 50 and 55 mmHg) throughout the intraoperative period and postoperatively until the onset of spontaneous ventilation. Relevant biochemical and hemodynamic variables were measured, and cerebral tissue oxygen saturation (SctO 2) was monitored with near-infrared spectroscopy. Patients were followed-up with neuropsychological testing. Patient demographics between groups were compared using the Fisher exact and Mann-Whitney tests, and SctO 2 between groups was compared using repeated measures analysis of variance. The median patient age was 67 years (interquartile range [IQR] 62-72 y), and the median EuroSCORE II was 1.1. The median CPB time was 106 minutes. The mean intraoperative arterial carbon dioxide partial pressure for each patient was significantly higher with TTMH (52.1 mmHg [IQR 49.9-53.9 mmHg] v 40.8 mmHg [IQR 38.7-41.7 mmHg]; p < 0.001) as was pulmonary artery pressure (23.9 mmHg [IQR 22.4-25.3 mmHg] v 18.5 mmHg [IQR 14.8-20.7 mmHg]; p = 0.004). There was no difference in mean percentage change in SctO 2 during CPB in the control group for both hemispheres (left: –6.7% v –2.3%; p = 0.110; right: –7.9% v –1.0%; p = 0.120). Compliance with neuropsychological test protocols was poor. However, the proportion of patients with drops in test score >20% was similar between groups in all tests. TTMH did not increase SctO 2 appreciably during CPB but increased pulmonary artery pressures before and after CPB. These findings do not support further investigation of TTMH as a means of improving SctO 2 during and after cardiac surgery requiring CPB. [ABSTRACT FROM AUTHOR]

Avoiding hypoxaemia is considered crucial in cardiac surgery patients admitted to the intensive care unit (ICU). However, avoiding hyperoxaemia may also be important. A conservative approach to oxygen therapy may reduce exposure to hyperoxaemia without increasing the risk of hypoxaemia. Using a before-and-after design, we evaluated the introduction of conservative oxygen therapy (target SpO2 88%-92% using the lowest FiO2) for cardiac surgical patients admitted to the ICU. We studied 9041 arterial blood gas (ABG) datasets: 4298 ABGs from 245 'conventional' and 4743 ABGs from 298 'conservative' oxygen therapy patients. During mechanical ventilation (MV) and while in the ICU, compared to the conventional group, conservative group patients had significantly lower FiO2 exposure and PaO2 values ( P < 0.001 for each). Accordingly, using the mean PaO2 during MV, more conservative group patients were classified as normoxaemic (226 versus 62 patients, P < 0.01), fewer as hyperoxaemic (66 versus 178 patients, P < 0.01) and no patient in either group as hypoxaemic or severely hypoxaemic. Moreover, more ABG samples were hyperoxaemic or severely hyperoxaemic during conventional treatment ( P < 0.001). Finally, there was no difference in ICU or hospital length of stay, ICU or hospital mortality or 30-day mortality between the groups. Our findings support the feasibility and physiological safety of conservative oxygen therapy in patients admitted to ICU after cardiac surgery. [ABSTRACT FROM AUTHOR]

Objectives To identify the normal baseline preoperative range of cerebral tissue oxygen saturation (SctO 2 ) derived using near-infrared spectroscopy (NIRS) and the efficacy of perioperative interventions designed to modulate SctO 2 in cardiac surgical patients. Design Systematic review and meta-analysis of relevant randomized controlled trials (RCTs) extracted from the Medline, Embase, and Cochrane Central Register of Controlled Trials databases. Setting Hospitals performing cardiac surgery. Participants The study comprised 953 participants from 11 RCTs. Interventions Interventions included the following: (1) SctO 2 monitoring protocol compared with no monitoring; (2) use of cardiopulmonary bypass (CPB) compared with no CPB; (3) normothermic CPB compared with hypothermic CPB; (4) glyceryl trinitrate during surgery compared with placebo; (5) midazolam during induction of anesthesia compared with propofol; (6) sevoflurane anesthesia compared with total intravenous anesthesia; (7) sevoflurane anesthesia compared with propofol-based anesthesia; and (8) norepinephrine during CPB compared with phenylephrine. Measurements and Main Results Eleven RCTs with 953 participants measured baseline preoperative SctO 2 using NIRS. The pooled mean baseline SctO 2 was 66.4% (95% CI 65.0-67.7), generating a reference range of 51.0% to 81.8%. Four interventions (1, 3, 4, and 6 described in the Interventions section above) increased intraoperative SctO 2 across the majority of reported time points. Postoperative follow-up of SctO 2 occurred in only 1 study, and postoperative cognitive assessment correlating SctO 2 with cognitive function was applied in only 4 studies using variable methodology. Conclusions The authors have established that reference values for baseline NIRS-derived SctO 2 in cardiac surgery patients are varied and have identified interventions that modulate SctO 2 . This information opens the door to standardized research and interventional studies in this field. [ABSTRACT FROM AUTHOR]

Objectives To estimate carotid and brachial artery blood flow with Doppler ultrasound in cardiac surgery patients and relate such estimates to cardiac index, lactate levels, and markers of renal function. Design A prospective observational study. Setting A teaching hospital. Participants Twenty-five elective cardiac surgery patients. Interventions The authors measured bilateral carotid and brachial artery blood flows using Doppler ultrasound and, simultaneously, cardiac index using a pulmonary artery catheter; lactate and serum creatinine levels; and urine output. The relationship between these indices and biomarkers was assessed statistically. Measurements and Main Results Median carotid arterial blood flow was estimated at 0.323 L/min (interquartile ratio [IQR], 0.256-0.429 L/min) on the right and 0.308 L/min (IQR, 0.247–0.376 L/min) on the left at baseline. Median brachial arterial blood flow was estimated at 0.063 L/min (IQR, 0.039–0.115 L/min) on the right and 0.063 L/min (IQR, 0.039–0.081 L/min) on the left at baseline. There was a weak correlation between right- and left-sided flows (brachial: rho = 0.285; carotid: rho = 0.384) and between brachial and carotid flow (right: rho = 0.135, left: rho = 0.225). There also was a weak correlation between cardiac index and brachial flow (right: rho = 0.215; left: rho = 0.320) and carotid flow (left: rho = 0.159) immediately after surgery, and no correlation 1 day after surgery (right brachial: rho = -0.010; left brachial: rho = -0.064; left carotid: rho = –0.060). There were no significant correlations between carotid or brachial flows and lactate and serum creatinine levels or urine output. Conclusions In cardiac surgery patients, Doppler-estimated carotid and brachial arterial blood flows have only a weak correlation with cardiac index and no correlation with lactate or creatinine levels or urine output. Thus, Doppler estimation of these blood flows cannot be used to provide noninvasive estimates of cardiac index in patients after cardiac surgery. [ABSTRACT FROM AUTHOR]

Objectives To determine the ability of urinary neutrophil gelatinase-associated lipocalin (uNGAL) to predict cardiac surgery-associated acute kidney injury (CSA-AKI), continuous renal replacement therapy (CRRT), mortality, and a composite outcome of major adverse kidney events at 365 days (MAKE 365 ), and to investigate the influence of cardiopulmonary bypass (CPB) on NGAL release. Design A prospective observational study. Setting A single-center university hospital. Participants A cohort of 288 adult cardiac surgery patients. Interventions uNGAL was measured at baseline, immediately after surgery, and on days 1 and 2 postoperatively. The authors used the recent Kidney Disease Improving Global Outcomes consensus criteria to define CSA-AKI. Measurements and Main Results CSA-AKI occurred in 36.1% of patients. uNGAL rapidly became significantly higher in patients who developed AKI, with peak value immediately after surgery (349.9 [76.6-1446.6] v 90.1 [20.8-328] ng/mg creatinine; p<0.001). No measure of uNGAL (peak, postsurgery, day 1 or 2 postsurgery) accurately predicted CSA-AKI, CRRT, mortality, or MAKE 365 . However, immediately after surgery, CPB induced greater uNGAL release compared with off-pump surgery (265.5 µmol/L [71-989.6] v 48.7 ng/mg creatinine [17-129.8]; p<0.001). Moreover, such early uNGAL release correlated with CPB duration (r = 0.505; p<0.001) but not with peak serum creatinine values on day 3 or 7 after surgery. Conclusions uNGAL had a limited predictive ability for CSA-AKI or other relevant clinical outcomes after cardiac surgery and appeared to be more closely related to the use and duration of CPB. Thus, its levels may represent the aggregate effect of an inflammatory response to CPB as well as a renal response to cardiac surgery and inflammation. [ABSTRACT FROM AUTHOR]

Theoretically, systemic carbon dioxide (VCO[sub 2]) production should be an alternative means to systemic oxygen uptake (VO[sub 2]) for estimating the global efficacy of cardiopulmonary bypass (CPB). This study compared two methods of estimating VCO : Fick's principle and oxygenator exhaust carbon dioxide (CO[sup 2]) output. Both of these estimates were then compared with VO[sup 2]. Fifty-one patients (39 male and 12 female) undergoing elective cardiac surgery requiring CPB were studied. Blood sampling was performed and measurements recorded during active cooling, environmental cooling/stable hypothermia and during rewarming. Blood samples were measured for CO[sup 2] tension from which content was estimated. VCO[sub 2] was calculated as the product of the arteriovenous difference in CO[sub 2] content and pump flow rate (Fick's principle), or the fresh gas flow rate and concentration of the oxygenator exhaust CO[sub 2] (output technique). Over all measurements, method comparison analysis revealed - alarge mean bias of 41 (95% confidence intervals (CI) 32 50) mL/min with very wide limits of agreement ( - 23, 105 mL/min). Regression analysis found that the bias was also proportional to the size of measurement (β= 0.75 (95% CI 0.55, 0.95)). Although both methods of VCO[sub 2] correlated significantly with VO[sub 2] (p < 0.01), regression analysis found that the coefficients (β) of both techniques had wide CI (Fick's principle: β= 1.37 (95% CI 1.20, 1.54); output technique: β= 0.58 (95%CI 0.44, 0.71)). In conclusion, both techniques of VCO[sub 2] cannot be used interchangeably, and both are imprecisely related to VO[sub 2] as estimated by Fick's principle. [ABSTRACT FROM AUTHOR]