Silvia R Cottini

Noninvasive cardiac output and blood pressure monitoring cannot replace an invasive monitoring system in critically ill patients

BackgroundMonitoring of cardiac output and blood pressure are standard procedures in critical care medicine. Traditionally, invasive techniques like pulmonary artery catheter (PAC) and arterial catheters are widely used. Invasiveness bears many risks of deleterious complications. Therefore, a noninvasive reliable cardiac output (CO) and blood pressure monitoring system could improve the safety of cardiac monitoring. The aim of the present study was to compare a noninvasive versus a standard invasive cardiovascular monitoring system.MethodsNexfin HD is a continuous noninvasive blood pressure and cardiac output monitor system and is based on the development of the pulsatile unloading of the finger arterial walls using an inflatable finger cuff. During continuous BP measurement CO is calculated. We included 10 patients with standard invasive cardiac monitoring system (pulmonary artery catheter and arterial catheter) comparing invasively obtained data to the data collected noninvasively using the Nexfin HD.ResultsCorrelation between mean arterial pressure measured with the standard arterial monitoring system and the Nexfin HD was r2 = 0.67 with a bias of -2 mmHg and two standard deviations of ± 16 mmHg. Correlation between CO derived from PAC and the Nexfin HD was r2 = 0.83 with a bias of 0.23 l/min and two standard deviations of ± 2.1 l/min; the percentage error was 29%.ConclusionAlthough the noninvasive CO measurement appears promising, the noninvasive blood pressure assessment is clearly less reliable than the invasively measured blood pressure. Therefore, according to the present data application of the Nexfin HD monitoring system in the ICU cannot be recommended generally. Whether such a tool might be reliable in certain critically ill patients remains to be determined.

Differential influence of arterial blood glucose on cerebral metabolism following severe traumatic brain injury

IntroductionMaintaining arterial blood glucose within tight limits is beneficial in critically ill patients. Upper and lower limits of detrimental blood glucose levels must be determined.MethodsIn 69 patients with severe traumatic brain injury (TBI), cerebral metabolism was monitored by assessing changes in arterial and jugular venous blood at normocarbia (partial arterial pressure of carbon dioxide (paCO2) 4.4 to 5.6 kPa), normoxia (partial arterial pressure of oxygen (paO2) 9 to 20 kPa), stable haematocrit (27 to 36%), brain temperature 35 to 38°C, and cerebral perfusion pressure (CPP) 70 to 90 mmHg. This resulted in a total of 43,896 values for glucose uptake, lactate release, oxygen extraction ratio (OER), carbon dioxide (CO2) and bicarbonate (HCO3) production, jugular venous oxygen saturation (SjvO2), oxygen-glucose index (OGI), lactate-glucose index (LGI) and lactate-oxygen index (LOI). Arterial blood glucose concentration-dependent influence was determined retrospectively by assessing changes in these parameters within pre-defined blood glucose clusters, ranging from less than 4 to more than 9 mmol/l.ResultsArterial blood glucose significantly influenced signs of cerebral metabolism reflected by increased cerebral glucose uptake, decreased cerebral lactate production, reduced oxygen consumption, negative LGI and decreased cerebral CO2/HCO3 production at arterial blood glucose levels above 6 to 7 mmol/l compared with lower arterial blood glucose concentrations. At blood glucose levels more than 8 mmol/l signs of increased anaerobic glycolysis (OGI less than 6) supervened.ConclusionsMaintaining arterial blood glucose levels between 6 and 8 mmol/l appears superior compared with lower and higher blood glucose concentrations in terms of stabilised cerebral metabolism. It appears that arterial blood glucose values below 6 and above 8 mmol/l should be avoided. Prospective analysis is required to determine the optimal arterial blood glucose target in patients suffering from severe TBI.

Increasing hematocrit above 28% during early resuscitative phase is not associated with decreased mortality following severe traumatic brain injury

BackgroundTo prevent iatrogenic damage, transfusions of red blood cells should be avoided. For this, specific and reliable transfusion triggers must be defined. To date, the optimal hematocrit during the initial operating room (OR) phase is still unclear in patients with severe traumatic brain injury (TBI). We hypothesized that hematocrit values exceeding 28%, the local hematocrit target reached by the end of the initial OR phase, resulted in more complications, increased mortality, and impaired recovery compared to patients in whom hematocrit levels did not exceed 28%.MethodsImpact of hematocrit (independent variable) reached by the end of the OR phase on mortality and morbidity determined by the extended Glasgow outcome scale (eGOS; dependent variables) was investigated retrospectively in 139 TBI patients. In addition, multiple logistic regression analysis was performed to identify additional important variables.FindingsFollowing severe TBI, mortality and morbidity were neither aggravated by hematocrit above 28% reached by the end of the OR phase nor worsened by the required transfusions. Upon multiple logistic regression analysis, eGOS was significantly influenced by the highest intracranial pressure and the lowest cerebral perfusion pressure values during the initial OR phase.ConclusionsBased on this retrospective observational analysis, increasing hematocrit above 28% during the initial OR phase following severe TBI was not associated with improved or worsened outcome. This questions the need for aggressive transfusion management. Prospective analysis is required to determine the lowest acceptable hematocrit value during the OR phase which neither increases mortality nor impairs recovery. For this, a larger caseload and early monitoring of cerebral metabolism and oxygenation are indispensable.

Association of intraoperative transfusion of blood products with mortality in lung transplant recipients.

BackgroundThe impact of intraoperative transfusion on postoperative mortality in lung transplant recipients is still elusive.MethodsUnivariate and multivariate analysis were performed to investigate the influence of red blood cells (RBCs) and fresh frozen plasma (FFP) on mortality in 134 consecutive lung transplants recipients from September 2003 until December 2008.ResultsIntraoperative transfusion of RBCs and FFP was associated with a significant increase in mortality with odds ratios (ORs) of 1.10 (1.03 to 1.16, P = 0.02) and 1.09 (1.02 to 1.15, P = 0.03), respectively. For more than four intraoperatively transfused RBCs multivariate analysis showed a hazard ratio for mortality of 3.8 (1.40 to 10.31, P = 0.003). Furthermore, non-survivors showed a significant increase in renal replacement therapy (RRT) (36.6% versus 6.9%, P <0.0001), primary graft dysfunction (PGD) (39.3% versus 5.9%, P <0.0001), postoperative need of extracorporeal membrane oxygenation (ECMO) (26.9% versus 3.1%, P = 0.0019), sepsis (24.2% versus 4.0%, P = 0.0004), multiple organ dysfunction syndrome (MODS) (26.9% versus 3.1%, P <0.0001), infections (18.1% versus 0.9%, P = 0.0004), retransplantation (12.1% versus 6.9%, P = 0.039) and readmission to the ICU (33.3% versus 12.8%, P = 0.024).ConclusionsIntraoperative transfusion is associated with a strong negative influence on outcome in lung transplant recipients.

The relationship between preoperative creatinine clearance and outcomes for patients undergoing liver transplantation: a retrospective observational study

BackgroundRenal failure with following continuous renal replacement therapy is a major clinical problem in liver transplant recipients, with reported incidences of 3% to 20%. Little is known about the significance of postoperative acute renal failure or acute-on-chronic renal failure to postoperative outcome in liver transplant recipients.MethodsIn this post hoc analysis we compared the mortality rates of 135 consecutive liver transplant recipients over 6 years in our center subject to their renal baseline conditions and postoperative RRT. We classified the patients into 4 groups, according to their preoperative calculated Cockcroft formula and the incidence of postoperative renal replacement therapy. Data then were analyzed in regard to mortality rates and in addition to pre- and peritransplant risk factors.ResultsThere was a significant difference in ICU mortality (p=.008), hospital mortality (p=.002) and cumulative survival (p<.0001) between the groups. The highest mortality rate occurred in the group with RRT and normal baseline kidney function (20% ICU mortality, 26.6% hospital mortality and 50% cumulative 1-year mortality, respectively). The hazard ratio in this group was 9.6 (CI 3.2-28.6, p=.0001).ConclusionThis study shows that in liver transplant recipient’s acute renal failure with postoperative RRT is associated with mortality and the mortality rate is higher than in patients with acute-on-chronic renal failure and postoperative renal replacement therapy.

Two different hematocrit detection methods: Different methods, different results?

BackgroundLess is known about the influence of hematocrit detection methodology on transfusion triggers. Therefore, the aim of the present study was to compare two different hematocrit-assessing methods. In a total of 50 critically ill patients hematocrit was analyzed using (1) blood gas analyzer (ABLflex 800) and (2) the central laboratory method (ADVIA® 2120) and compared.FindingsBland-Altman analysis for repeated measurements showed a good correlation with a bias of +1.39% and 2 SD of ± 3.12%. The 24%-hematocrit-group showed a correlation of r2 = 0.87. With a kappa of 0.56, 22.7% of the cases would have been transfused differently. In the-28%-hematocrit group with a similar correlation (r2 = 0.8) and a kappa of 0.58, 21% of the cases would have been transfused differently.ConclusionsDespite a good agreement between the two methods used to determine hematocrit in clinical routine, the calculated difference of 1.4% might substantially influence transfusion triggers depending on the employed method.

Pretransplant dyslipidaemia determines outcome in lung transplant recipients

BackgroundThere is little knowledge about the effect of dyslipidaemia on the outcome after lung transplantation. Thus, the aim of this retrospective single centre study was to analyse the impact of the plasma lipid profile on mortality in lung transplant recipients. From January 2000 to December 2008 the charts of 172 consecutive lung transplantation recipients were analysed. At baseline and after one year lipid profiles were routinely collected. During the follow-up major cardiovascular events (MCE; beginning of dialysis, cerebrovascular insult or myocardial infarction) were recorded. The follow-up period ended December 2010.FindingsOver all total cholesterol (4.3 ± 1.6 vs. 5.4 ± 1.3 mmol/l, p < 0.0001), triglycerides (1.2 ± 0.7 vs. 2.4 ± 1.3 mmol/l, p < 0.0001), HDL (1.5 ± 0.6 vs. 1.7 ± 0.6 mmol/l, p = 0.003) and TC/HDL ratio (3.0 ± 1.0 vs. 3.6 ± 1.2, p = 0.002) increased significantly after 1 year.During the observational period 6.9% (10 patients) suffered a major cardiac event. In univariate analysis MCE was associated with baseline TC: on average the event-group had a 33% higher baseline TC (5.6 vs. 4.2 mmol/l, OR 1.6, CI 1.1 – 2.2, p = 0.02). The total mortality in the observational period was 25% (36 patients overall). In univariate analysis mortality was associated with increased TC/HDL ratio. The non-survivors had on average a 22% higher baseline TC/HDL ratio (3.6 vs. 2.8, HR 2.8, CI 1.2 – 3.5, p = 0.001). There was no association between mortality and TC (p = 0.33), triglycerides (p = 0.34), HDL (p = 0.78) and creatinine (p = 0.73). In a multivariate model the hazard ratio was 1.5 (1.2 – 1.9, p = 0.001) per increase of 0.4 TC/HDL ratio.ConclusionsThis study shows that the total cholesterol before transplantation is associated with the incidence of MCE and the cholesterol/HDL ratio with mortality in lung transplanted recipients.

Echocardiography accurately predicts pulmonary hypertension in patients with advanced lung disease

Pulmonary hypertension (PH) may be observed in many different conditions, including advanced heart or lung disease [1]. PH is defined as elevation of the mean pulmonary arterial pressure (mPAP) ≥25 mmHg, measured by right heart catheterization (RHC). Since procedure-related risks and costs are not negligible, RHC is not routinely performed in patients with advanced lung disease during initial assessment and follow-up. Echocardiography is commonly used as screening tool for the presence of PH, but might be of limited diagnostic value, in particular in patients with lung disease [2]. Empirical formulas were proposed to calculate the mPAP starting from systolic pulmonary arterial pressure (sPAP) as assessed by echocardiography [3, 4]. It has been suggested that both the Chemla formula (mPAP = sPAP × 0.61 + 2 mmHg) and the Syyed formula (mPAP = sPAP × 0.65 + 0.55 mmHg) might accurately estimate the mPAP [5]. The aim of our study was to assess the accuracy of these echocardiography-based formulas to estimate the invasively measured mPAP in a cohort of patients with advanced lung disease. Estimation of sPAP by echocardiography was performed according to current recommendation by adding to the right ventricular/right atrial pressure gradient (based on Doppler-measured tricuspid regurgitation velocity) the estimated right atrial pressure (based on inferior vena cava diameter and collapsibility). A total of 96 consecutive patients undergoing lung transplant evaluation between 03/2000 and 10/2015 were included. Data from RHC and echocardiography performed the same day were available for the whole cohort. Spearman’s rank-order correlation was run to assess the relationship between RHC-measured mPAP and calculated mPAP. There was a strong positive correlation between both RHC-mPAP and ChemlamPAP (rs = 0.909, p < 0.001; Fig. 1a) and between RHC-mPAP and Syyed-mPAP (rs = 0.904, p < 0.001; Fig. 1b). Inspection of both diagrams suggests that the correlation between echocardiographic data and invasive pulmonary hemodynamics is of particular strength in patients with moderate elevation of pulmonary pressure. Whether echocardiography-based formulas are of similar accuracy to estimate pulmonary pressure of PH in patients with severe PH remains unclear. However, this might be of minor relevance since, as shown in our cohort, only a minority of patients with advanced lung disease present with a mPAP >50 mmHg. In these patients, further invasive assessment of pulmonary hemodynamics may be indicated. For all other patients our data emphasize that echocardiography is an accurate tool to estimate pulmonary pressure in patients with advanced lung disease.

Pretransplant dyslipidaemia influences primary graft dysfunction after lung transplantation

OBJECTIVES Primary graft dysfunction (PGD) is a major cause of mortality within the first year following lung transplantation. Pulmonary hypertension, elevated body mass index (BMI), prolonged ischaemic time of the graft, intraoperative blood transfusions >1000 ml and the use of cardiopulmonary bypass or extracorporeal membrane oxygenation increase the risk for PGD. We aimed to evaluate whether dyslipidaemia is an additional risk factor for the development of PGD. METHODS We retrospectively analysed demographic and clinical data of 264 patients who received their first bilateral lung transplantation between March 2000 and October 2013 at our institution. The endpoint was PGD grade 3 at any time, defined according to the International Society for Heart and Lung Transplantation (ISHLT) criteria. Fasting lipid profiles at listing time or just before transplantation (baseline) were documented and dyslipidaemia was defined as any of the parameters being out of range. Comparisons of continuous variables between patients with PGD grade 3 and patients without were performed with the Mann-Whitney U-test, whereas proportions were compared with the χ(2) test. Continuous variables were presented as arithmetic means with standard deviation for ease of comparison, but levels of statistical significance were computed using the appropriate non-parametric statistical test. To identify PGD risk factors, a forward stepwise logistic regression model was used. RESULTS PGD occurred in 63 recipients (24%). Pretransplant dyslipidaemia was documented in 153 recipients (58%) and was significantly more prevalent among recipients developing PGD (45 vs 108, P < 0.013). Despite various underlying pulmonary pathologies, higher triglyceride (TG) levels (1.41 ± 0.78 vs 1.16 ± 0.78, P < 0.012), lower high-density lipoprotein-cholesterol (HDL-C) concentrations (1.24 ± 0.55 vs 1.57 ± 0.71, P < 0.0005) and higher cholesterol/HDL-C values (3.80 ± 2.02 vs 3.00 ± 0.92, P < 0.0005) were associated with a lower incidence of PGD. Patients with PGD had significantly longer ischaemic time (350 ± 89 vs 322 ± 91, P = 0.017) and higher BMI (23 ± 5 vs 21 ± 4.4, P < 0.007). CONCLUSIONS Dyslipidaemia seems to be an independent risk factor for PGD after lung transplantation: low circulating levels of HDL-C and hypertriglyceridaemia increase the incidence of PGD. Even if HDL-C levels are difficult to alter today, triglyceride and cholesterol levels can be addressed therapeutically and may have a positive influence on the development of PGD.

Pulmonary hypertension is not a risk factor for grade 3 primary graft dysfunction after lung transplantation

Grade 3 primary graft dysfunction (PGD3) represents the most important risk factor for patient mortality during the first year after lung transplantation (LTX). We investigated whether pretransplant pulmonary hypertension (PH) is a risk factor for the development of PGD3. This retrospective, single‐center cohort study included 96 candidates undergoing right heart catheterization (RHC) prior to being listed for LTX between March 2000 and October 2015. Based on their mean pulmonary artery pressure (mPAP) levels, the patients were classified into 3 groups: (1) <25 mm Hg, (2) 25‐34 mm Hg and (3) ≥35 mm Hg. Forty‐seven patients were classified in group 1, 31 in group 2, and 18 in group 3. Fifteen recipients (16%, 95%‐CI 8‐23) developed PGD3. In the univariate analysis, the diagnosis of interstitial lung disease (ILD) compared to COPD (OR: 7.06, P = .005), blood transfusion >1000 mL during surgery (OR: 5.25, P = .005), the need for intra‐operative cardio‐pulmonary bypass (CPB) or extra‐corporeal membrane oxygenation (ECMO) (OR: 4, P = .027), mPAP (OR 1.06, P = .007) and serum high density lipoprotein‐cholesterol (HDL‐C) (OR 0.09, P = .005) were associated with PGD3. In the multivariable logistic regression analysis, only HDL‐C (OR 0.10, P = .016) was associated with PGD3 based on our single‐center cohort data analysis.