Discrimination and calibration properties of the hypotension probability indicator during cardiac and vascular surgery.

BACKGROUND: Hypotension during surgery is linked to postoperative complications. Recently, a new hemodynamic algorithm intended to predict hypotensive events (hypotension probability indicator [HPI]) has been developed. The aim of the present study is to test the discrimination and calibration properties of the HPI. METHODS: The intraoperative files of 23 patients undergoing cardiac and major vascular surgery receiving the HPI-based hemodynamic monitoring were retrospectively investigated for prediction of hypotensive events (mean arterial pressure <65 mmHg). The HPI was available at 20 seconds intervals; the values of HPI five to seven minutes before a hypotensive event (HPI5-7) were tested for discrimination and calibration. RESULTS: The HPI5-7 has a fair level of discrimination (area under the curve 0.768) and a poor calibration, due to overestimation of the hypotensive risk. At the observed prevalence, a cut-off value of 85% carries a sensitivity of 62.4% and a specificity of 77.7%, a negative predictive value (NPV) of 97.8% and a positive predictive value (PPV) of 12.6%; a value of 98% has a PPV of 64% and an NPV of 95.3%. CONCLUSIONS: The HPI5-7 may offer some useful insights. Values ≤85% carry a clinically acceptable NPV for hypotensive events at the observed prevalence and may represent a "safe zone" during surgery. Values >85% do not carry enough PPV to trigger hemodynamic interventions, but represent a warning signal. Values >98% are highly suggesting a hypotensive event after 5-7 minutes. Further studies exploring the predictive ability of the HPI at different times are needed.

Acute Normovolemic Hemodilution Reduces Allogeneic Red Blood Cell Transfusion in Cardiac Surgery: A Systematic Review and Meta-analysis of Randomized Trials.

BACKGROUND: To better understand the role of acute normovolemic hemodilution (ANH) in a surgical setting with high risk of bleeding, we analyzed all randomized controlled trials (RCTs) in the setting of cardiac surgery that compared ANH with standard intraoperative care. The aim was to assess the incidence of ANH-related number of allogeneic red blood cell units (RBCu) transfused. Secondary outcomes included the rate of allogeneic blood transfusion and estimated total blood loss. METHODS: Twenty-nine RCTs for a total of 2439 patients (1252 patients in the ANH group and 1187 in the control group) were included in our meta-analysis using PubMed/MEDLINE, Cochrane Controlled Trials Register, and EMBASE. RESULTS: Patients in the ANH group received fewer allogeneic RBCu transfusions (mean difference = -0.79; 95% confidence interval [CI], -1.25 to -0.34; P = .001; I = 95.1%). Patients in the ANH group were overall transfused less with allogeneic blood when compared with controls (356/845 [42.1%] in the ANH group versus 491/876 [56.1%] in controls; risk ratio = 0.74; 95% CI, 0.62 to 0.87; P < .0001; I = 72.5%), and they experienced less postoperative blood loss (388 mL in ANH versus 450 mL in control; mean difference = -0.64; 95% CI, -0.97 to -0.31; P < .0001; I = 91.8%). CONCLUSIONS: ANH reduces the number of allogeneic RBCu transfused in the cardiac surgery setting together with a reduction in the rate of patients transfused with allogeneic blood and with a reduction of bleeding.

Cardiac index assessment by the pressure recording analytic method in critically ill unstable patients after cardiac surgery.

OBJECTIVE: The authors measured cardiac index in unstable patients after cardiac surgery with the Pressure Recording Analytic Method (PRAM) and compared it with the reference method of thermodilution (ThD) with the pulmonary artery catheter; using the hypothesis that there were no significant differences between the 2 methods. DESIGN: A prospective study. SETTING: Cardiac surgery intensive care unit in a teaching hospital. PARTICIPANTS: Ninety-four measurements from 59 patients with ongoing high doses of inotropic drugs and/or an intra-aortic balloon pump for low-cardiac-output syndrome after cardiac surgery were studied. INTERVENTIONS: The pulmonary artery catheter and the radial or femoral arterial catheter for measuring blood pressure were already in place for standard hemodynamic monitoring. MEASUREMENTS AND MAIN RESULTS: The mean of the total CI measurements was 2.94 ± 0.67 L/min/m(2) with PRAM and 2.95 ± 0.63 L/min/m(2) with ThD, with no significant difference according to the linear mixed models analysis. The PRAM and ThD techniques were similar in unstable patients without atrial fibrillation (mean bias 0.047 ± 0.395 L/min/m(2) and a percentage error of 29%), while no agreement between PRAM and ThD was found in unstable patients with atrial fibrillation (mean bias 0.195 ± 0.885 L/min/m(2) and a percentage error of 69%). CONCLUSION: Cardiac index measurements after cardiac surgery performed with PRAM and with ThD showed a good agreement in hemodynamically unstable patients given high doses of inotropes and/or an IABP in patients in sinus rhythm, but not in those with atrial fibrillation.

The effect of isoflurane on survival and myocardial infarction: a meta-analysis of randomized controlled studies.

OBJECTIVE: The aim of this meta-analysis was to investigate the cardioprotective properties of isoflurane versus any comparator in terms of the rate of myocardial infarction and all-cause mortality. DESIGN: Pertinent studies were searched independently in Biomed, Central, PubMed, Embase, and the Cochrane Central Register of clinical trials. The primary endpoint was mortality at the longest follow-up available. SETTING: A hospital. PARTICIPANTS: Randomized controlled trials. INTERVENTION: A meta-analysis of 37 trials. MEASUREMENTS AND MAIN RESULTS: The 37 included trials randomized 3,539 patients in cardiac (16 studies) and in noncardiac surgery (21 studies) with noninhalation comparators in 55% of trials. The overall analysis showed no difference in mortality between the isoflurane and control groups (16/1,602 [1.0%] v 23/1,937 [1.2%], odds ratios (OR) = 0.76 [0.39-1.47], p = 0.4 with 37 studies included) and no difference in the rate of myocardial infarction (3/1,312 [0.2%] v 1/1,532 [0.07%], OR = 2.03 [0.27-15.49], p = 0.5 with 30 studies included). Mortality was reduced in the isoflurane group when only studies with a low risk of bias were included in the analyses (0/540 [0%] v 5/703 [0.7%] in the control arm, OR = 0.13 [0.02-0.76], p = 0.02) with 4 cardiac and 6 noncardiac trials included and 5 noninhalation and 5 inhalation agents as the comparator. A trend was noted when a subanalysis was performed with propofol as a comparator (1/544 [0.2%] v 6/546 [1.1%], p = 0.05, with 16 studies included). CONCLUSIONS: Isoflurane reduced mortality in high-quality studies and showed a trend toward a reduction in mortality when it was compared with propofol. No differences in the rates of overall mortality and myocardial infarction were noted.

Cardiac index assessment by the pressure recording analytic method in unstable patients with atrial fibrillation.

OBJECTIVE: Most-Care (powered by the pressure-recording analytic method [PRAM]; Vytech HealthTM, Padova, Italy) is a minimally invasive cardiac output monitoring. This system already has been studied and validated in cardiac surgery and in children. It already showed a correlation with thermodilution methods in hemodynamically unstable patients. The purpose of this study was to confirm the reliability of cardiac index determinations by Most-Care in unstable patients with atrial fibrillation. DESIGN: A prospective study. SETTING: A teaching hospital. PARTICIPANTS: Forty-nine patients. INTERVENTIONS: Simultaneous cardiac index measurements by bolus thermodilution and by PRAM from a standard arterial access (radial and femoral) were obtained. The thermodilution cardiac index was calculated as the mean of 3 separate measurements. Because PRAM is a beat-to-beat monitoring system, the mean cardiac index of 12 consecutive beats was considered for the analysis. Correlations were calculated and differences compared by Bland-Altman analysis. MEASUREMENTS: Eight patients were excluded because the signal was altered by the arterial catheter resonance so that the study described the remaining 41 patients. The overall estimates of cardiac index measured by PRAM did not show agreement with the reference cardiac index by thermodilution (mean difference = 0.136 L/min/m(2) [0,43 L/min/m(2)-0.15 L/min/m(2)], with an upper limit of agreement of 1.94 L/min/m(2) and a lower limit of agreement of -1.665 L/min/m(2), respectively). The median (interquartile) value of cardiac index assessed by thermodilution was 2.42 L/min/m(2) (2.21-2.98 L/min/m(2)), and by PRAM it was 2.48 L/min/m(2) (1.80-3.00 L/min/m(2), p = 0.6). CONCLUSIONS: The authors concluded that PRAM did not compare well with thermodilution in unstable patients with atrial fibrillation.