Increasing mean arterial blood pressure in sepsis: effects on fluid balance, vasopressor load and renal function

Time delays between physiological signals in interpreting the body's responses to intermittent hypoxia in obstructive sleep apnea

Objective.Intermittent hypoxia, the primary pathology of obstructive sleep apnea (OSA), causes cardiovascular responses resulting in changes in hemodynamic parameters such as stroke volume (SV), blood pressure (BP), and heart rate (HR). However, previous studies have produced very different conclusions, such as suggesting that SV increases or decreases during apnea. A key reason for drawing contrary conclusions from similar measurements may be due to ignoring the time delay in acquiring response signals. By analyzing the signals collected during hypoxia, we aim to establish criteria for determining the delay time between the onset of apnea and the onset of physiological parameter response.Approach.We monitored oxygen saturation (SpO2), transcutaneous oxygen pressure (TcPO2), and hemodynamic parameters SV, HR, and BP, during sleep in 66 patients with different OSA severity to observe body's response to hypoxia and determine the delay time of above parameters. Data were analyzed using the Kruskal-Wallis test, Quade test, and Spearman test.Main results.We found that simultaneous acquisition of various parameters inevitably involved varying degrees of response delay (7.12-25.60 s). The delay time of hemodynamic parameters was significantly shorter than that of SpO2and TcPO2(p< 0.01). OSA severity affected the response delay of SpO2, TcPO2, SV, mean BP, and HR (p< 0.05). SV delay time was negatively correlated with the apnea-hypopnea index (r= -0.4831,p< 0.0001).Significance.The real body response should be determined after removing the effect of delay time, which is the key to solve the problem of drawing contradictory conclusions from similar studies. The methods and important findings presented in this study provide key information for revealing the true response of the cardiovascular system during hypoxia, indicating the importance of proper signal analysis for correctly interpreting the cardiovascular hemodynamic response phenomena and exploring their physiological and pathophysiological mechanisms.

Dose-related effects of norepinephrine on early-stage endotoxemic shock in a swine model

Background

The benefits of early use of norepinephrine in endotoxemic shock remain unknown. We aimed to elucidate the effects of different doses of norepinephrine in early-stage endotoxemic shock using a clinically relevant large animal model.

Methods

Vasodilatory shock was induced by endotoxin bolus in 30 Bama suckling pigs. Treatment included fluid resuscitation and administration of different doses of norepinephrine, to induce return to baseline mean arterial pressure (MAP). Fluid management, hemodynamic, microcirculation, inflammation, and organ function variables were monitored. All animals were supported for 6 h after endotoxemic shock.

Results

Infused fluid volume decreased with increasing norepinephrine dose. Return to baseline MAP was achieved more frequently with doses of 0.8 µg/kg/min and 1.6 µg/kg/min (P <0.01). At the end of the shock resuscitation period, cardiac index was higher in pigs treated with 0.8 µg/kg/min norepinephrine (P <0.01), while systemic vascular resistance was higher in those receiving 0.4 µg/kg/min (P <0.01). Extravascular lung water level and degree of organ edema were higher in animals administered no or 0.2 µg/kg/min norepinephrine (P <0.01), while the percentage of perfused small vessel density (PSVD) was higher in those receiving 0.8 µg/kg/min (P <0.05) and serum lactate was higher in the groups administered no and 1.6 µg/kg/min norepinephrine (P <0.01).

Conclusions

The impact of norepinephrine on the macro- and micro-circulation in early-stage endotoxemic shock is dose-dependent, with very low and very high doses resulting in detrimental effects. Only an appropriate norepinephrine dose was associated with improved tissue perfusion and organ function.

Predicting the Onset of Sepsis Using Vital Signs Data: A Machine Learning Approach

Sepsis is a major cause of mortality among hospitalized patients. Existing sepsis prediction methods face limitations due to their reliance on laboratory results and Electronic Medical Records (EMRs). This work aimed to develop a sepsis prediction model utilizing continuous vital signs monitoring, offering an innovative approach to sepsis prediction. Data from 48,886 Intensive Care Unit (ICU) patient stays were extracted from the Medical Information Mart for Intensive Care -IV dataset. A machine learning model was developed to predict sepsis onset based solely on vital signs. The model's efficacy was compared with the existing scoring systems of SIRS, qSOFA, and a Logistic Regression model. The machine learning model demonstrated superior performance at 6 hrs prior to sepsis onset, achieving 88.1% sensitivity and 81.3% specificity, surpassing existing scoring systems. This novel approach offers clinicians a timely assessment of patients' likelihood of developing sepsis.

Admission Blood Glucose Is Associated With the 30-Days Mortality in Septic Patients: A Retrospective Cohort Study

Background: Sepsis, as one of the severe diseases, is frequently observed in critically ill patients, especially concurrent with diabetes. Whether admission blood glucose is associated with the prognosis, and outcome of septic patients is still debatable.

Methods: We retrospectively reviewed and analyzed the demographic characteristics of septic patients in the Medical Information Mart for Intensive Care III (MIMIC III, version 1.4) between June 2001 and October 2012. The Chi-square and Fisher's exact tests were used for the comparison of qualitative variables among septic patients with different glucose levels and the 30-day mortality in septic patients with diabetes or not. Univariate and stepwise multivariate Cox regression analyses were used to determine the risk factors for 30-day mortality. Kaplan-Meier analysis was conducted to reveal the different 30-day survival probabilities in each subgroup.

Results: A total of 2,948 septic patients (910 cases with diabetes, 2,038 cases without diabetes) were ultimately included in the study. The 30-day mortality was 32.4% (956/2,948 cases) in the overall population without any difference among diabetic and non-diabetic septic patients (p = 1.000). Admission blood glucose levels <70 mg/dl were only observed to be significantly associated with the 30-day mortality of septic patients without diabetes (hazard ratio (HR) = 2.48, p < 0.001). After adjusting for confounders, age >65 years (HR = 1.53, p = 0.001), the Sequential Organ Failure Assessment (SOFA) score >5 (HR = 2.26, p < 0.001), lactic acid >2 mmol/L (Lac, HR = 1.35, p = 0.024), and platelet abnormality (<100 k/ul: HR = 1.49; >300 k/ul: HR = 1.36, p < 0.001) were the independent risk factors for 30-day mortality in septic patients with diabetes. In non-diabetes population, age >65 years (HR = 1.53, p < 0.001), non-White or non-Black patients (HR = 1.30, p = 0.004), SOFA score >5 (HR = 1.56, p < 0.001), blood glucose <70 mg/dl (HR = 1.91, p = 0.003), anion gap (AG) >2 mmol/L (HR = 1.60, p < 0.001), Lac (HR = 1.61, p < 0.001), urea nitrogen >21 mg/dl (HR = 1.45, p = 0.001), alanine aminotransferase (ALT, HR = 1.31, p = 0.009), total bilirubin >1.2 mg/dl (HR = 1.20, p = 0.033), and low hemoglobin (HR = 1.34, p = 0.001) were the independent risk factors for 30-day mortality.

Conclusions: Our results indicate admission blood glucose, especially in terms of <70 mg/dl, is the key signaling in predicting the worse 30-day survival probability of septic patients without diabetes, which could help clinicians to make a more suitable and precise treatment modality in dealing with septic patients.

Invasive Blood Pressure Measurement and In-hospital Mortality in Critically Ill Patients With Hypertension

Background: Invasive blood pressure (IBP) measurement is common in the intensive care unit, although its association with in-hospital mortality in critically ill patients with hypertension is poorly understood.

Methods and Results: A total of 11,732 critically ill patients with hypertension from the eICU-Collaborative Research Database (eICU-CRD) were enrolled. Patients were divided into 2 groups according to whether they received IBP. The primary outcome in this study was in-hospital mortality. Propensity score matching (PSM) and inverse probability of treatment weighing (IPTW) models were used to balance the confounding covariates. Multivariable logistic regression was used to evaluate the association between IBP measurement and hospital mortality. The IBP group had a higher in-hospital mortality rate than the no IBP group in the primary cohort [238 (8.7%) vs. 581 (6.5%), p < 0.001]. In the PSM cohort, the IBP group had a lower in-hospital mortality rate than the no IBP group [187 (8.0%) vs. 241 (10.3%), p = 0.006]. IBP measurement was associated with lower in-hospital mortality in the PSM cohort (odds ratio, 0.73, 95% confidence interval, 0.59–0.92) and in the IPTW cohort (odds ratio, 0.81, 95% confidence interval, 0.67–0.99). Sensitivity analyses showed similar results in the subgroups with high body mass index and no sepsis.

Conclusions: In conclusion, IBP measurement was associated with lower in-hospital mortality in critically ill patients with hypertension, highlighting the importance of IBP measurement in the intensive care unit.

Use of Organ Dysfunction as a Primary Outcome Variable Following Cecal Ligation and Puncture: Recommendations for Future Studies

Outcomes variables for research on sepsis have centered on mortality and changes in the host immune response. However, a recent task force (Sepsis-3) revised the definition of sepsis to "life-threatening organ dysfunction caused by a dysregulated host response to infection." This new definition suggests that human studies should focus on organ dysfunction. The appropriate criteria for organ dysfunction in either human sepsis or animal models are, however, poorly delineated, limiting the potential for translation. Further, in many systems, the difference between "dysfunction" and "injury" may not be clear. In this review, we identify criteria for organ dysfunction and/or injury in human sepsis and in rodents subjected to cecal ligation and puncture (CLP), the most commonly used animal model of sepsis. We further examine instances where overlap between human sepsis and CLP is sufficient to identify translational endpoints. Additional verification may demonstrate that these endpoints are applicable to other animals and to other sepsis models, for example, pneumonia. We believe that the use of these proposed measures of organ dysfunction will facilitate mechanistic studies on the pathobiology of sepsis and enhance our ability to develop animal model platforms to evaluate therapeutic approaches to human sepsis.

Effects of impaired microvascular flow regulation on metabolism-perfusion matching and organ function

Impaired tissue oxygen delivery is a major cause of organ damage and failure in critically ill patients, which can occur even when systemic parameters, including cardiac output and arterial hemoglobin saturation, are close to normal. This review addresses oxygen transport mechanisms at the microcirculatory scale, and how hypoxia may occur in spite of adequate convective oxygen supply. The structure of the microcirculation is intrinsically heterogeneous, with wide variations in vessel diameters and flow pathway lengths, and consequently also in blood flow rates and oxygen levels. The dynamic processes of structural adaptation and flow regulation continually adjust microvessel diameters to compensate for heterogeneity, redistributing flow according to metabolic needs to ensure adequate tissue oxygenation. A key role in flow regulation is played by conducted responses, which are generated and propagated by endothelial cells and signal upstream arterioles to dilate in response to local hypoxia. Several pathophysiological conditions can impair local flow regulation, causing hypoxia and tissue damage leading to organ failure. Therapeutic measures targeted to systemic parameters may not address or may even worsen tissue oxygenation at the microvascular level. Restoration of tissue oxygenation in critically ill patients may depend on restoration of endothelial cell function, including conducted responses.

Defense mechanisms to increasing back pressure for hepatic oxygen transport and venous return in porcine fecal peritonitis

High central venous pressure (CVP) acutely decreases venous return. How this affects hepatic oxygen transport in sepsis remains unclear. The aim of this study was to evaluate the effects of repeated increases in CVP via standard nursing procedures (NPs) on hepato-splanchnic and renal oxygen transport in a prolonged porcine sepsis model. Twenty anesthetized and mechanically ventilated pigs with regional hemodynamics monitored were randomized to fecal peritonitis or controls (n = 10 pigs/group). Resuscitation was started after 8 h of observation and continued for 3 days. NPs were performed at baseline and 8 h, 32 h, 56 h, and 72 h after resuscitation started. NPs increased CVP by 4-7 mmHg in both groups. In controls, this was associated with less decrease in hepatic arterial (Q_ha; 62 ± 70 mL/min) than portal venous flow (Q_pv; 364 ± 151 mL/min). Portal venous oxygen content and hepatic O₂ delivery (Do₂) and consumption (V̇o₂) decreased by 11 ± 6 mL/dL and 0.9 ± 0.3 and 0.4 ± 0.3 mL·min^-1·kg^-1, respectively. In septic animals, hepatic Do₂ decreased more in response to increasing CVP (1.5 ± 0.9 mL·min^-1·kg^-1), which was attributable to a larger fall in both Q_ha (88 ± 66 ml/min) and portal O₂ content (14 ± 10 mL/dL, all P < 0.05). This resulted in numerically lower hepatic V̇o₂ since O₂ extraction did not increase significantly. In control conditions, a smaller decrease in Q_ha compared with Q_pv helped to limit the reduction in hepatic V̇o₂ in response to acute CVP increase. In sepsis, the contribution of Q_ha to maintain hepatic Do₂ was reduced, which jeopardized hepatic V̇o₂ further. Renal arterial flow was similarly affected by CVP increase as Q_ha.NEW & NOTEWORTHY Sepsis impairs intrinsic mechanisms to attenuate effects of increasing back pressure on hepatic oxygen transport.

Impaired angiotensin II type 1 receptor signaling contributes to sepsis-induced acute kidney injury

In sepsis-induced acute kidney injury, kidney blood flow may increase despite decreased glomerular filtration. Normally, angiotensin-II reduces kidney blood flow to maintain filtration. We hypothesized that sepsis reduces angiotensin type-1 receptor (AT1R) expression to account for this observation and tested this hypothesis in a patient case-control study and studies in mice. Seventy-three mice underwent cecal ligation and puncture (a sepsis model) or sham operation. Additionally, 94 septic mice received losartan (selective AT1R antagonist), angiotensin II without or with losartan, or vehicle. Cumulative urine output, kidney blood flow, blood urea nitrogen, and creatinine were measured. AT1R expression was assessed using ELISA, qPCR, and immunofluorescence. A blinded pathologist evaluated tissue for ischemic injury. AT1R expression was compared in autopsy tissue from seven patients with sepsis to that of the non-involved portion of kidney from ten individuals with kidney cancer and three non-infected but critically ill patients. By six hours post ligation/puncture, kidney blood flow doubled, blood urea nitrogen rose, and urine output fell. Concurrently, AT1R expression significantly fell 2-fold in arterioles and the macula densa. Creatinine significantly rose by 24 hours and sham operation did not alter measurements. Losartan significantly exacerbated ligation/puncture-induced changes in kidney blood flow, blood urea nitrogen, creatinine, and urine output. There was no histologic evidence of cortical ischemia. Significantly, angiotensin II prevented changes in kidney blood flow, creatinine, and urine output compared to vehicle. Co-administering losartan with angiotensin-II reversed this protection. Relative to both controls, patients with sepsis had low AT1R expression in arterioles and macula densa. Thus, murine cecal ligation/puncture and clinical sepsis decrease renal AT1R expression. Angiotensin II prevents functional changes while AT1R-blockade exacerbates them independent of ischemia in mice.

The antisecretory peptide AF-16 may modulate tissue edema but not inflammation in experimental peritonitis induced sepsis

Sepsis is a life-threatening condition due to a dysregulated immunological response to infection. Apart from source control and broad-spectrum antibiotics, management is based on fluid resuscitation and vasoactive drugs. Fluid resuscitation implicates the risk of volume overload, which in turn is associated with longer stay in intensive care, prolonged use of mechanical ventilation and increased mortality. Antisecretory factor (AF), an endogenous protein, is detectable in most tissues and in plasma. The biologically active site of the protein is located in an 8-peptide sequence, contained in a synthetic 16-peptide fragment, named AF-16. The protein as well as the peptide AF-16 has multiple modulatory effects on abnormal fluid transport and edema formation/resolution as well as in a variety of inflammatory conditions. Apart from its' anti-secretory and anti-inflammatory characteristics, AF is an inhibitor of capillary leakage in intestine. It is not known whether the protein AF or the peptide AF-16 can ameliorate symptoms in sepsis. We hypothesized that AF-16 decreases the degree of hemodynamic instability, the need of fluid resuscitation, vasopressor dose and tissue edema in fecal peritonitis. To test the hypothesis, we induced peritonitis and sepsis by injecting autologous fecal solution into abdominal cavity of anesthetized pigs, and randomized (in a blind manner) the animals to intervention (AF-16, n = 8) or control (saline, n = 8) group. After the onset of hemodynamic instability (defined as mean arterial pressure < 60 mmHg maintained for > 5 minutes), intervention with AF-16 (20 mg/kg (50 mg/ml) in 0.9% saline) intravenously (only the vehicle in the control group) and a protocolized resuscitation was started. We recorded respiratory and hemodynamic parameters hourly for twenty hours or until the animal died and collected post mortem tissue samples at the end of the experiment. No differences between the groups were observed regarding hemodynamics, overall fluid balance, lung mechanics, gas exchange or histology. However, liver wet-to-dry ratio remained lower in AF-16 treated animals as compared to controls, 3.1 ± 0.4, (2.7-3.5, 95% CI, n = 8) vs 4.0 ± 0.6 (3.4-4.5, 95% CI, n = 8), p = 0.006, respectively. Bearing in mind the limited sample size, this experimental pilot study suggests that AF-16 may inhibit sepsis induced liver edema in peritonitis-sepsis.

Clinical evaluation of arterial blood pressure in anesthetized dogs by use of a veterinary-specific multiparameter monitor

OBJECTIVE

To compare noninvasive blood pressure (NIBP) measurements with invasive blood pressure (IBP) measurements of arterial blood pressure (ABP) in anesthetized dogs as obtained with a veterinary-specific multiparameter monitor.

ANIMALS

21 client-owned healthy female dogs anesthetized for routine ovariohysterectomy.

PROCEDURES

ABP measurements were obtained with a single veterinary-specific multiparameter monitor via a pneumatic cuff placed over the medial dorsal metatarsal artery (NIBP) and a transducer connected to a catheter placed in the contralateral artery (IBP). The 224 paired ABP measurements (complete data set) were categorized into 3 subsets-hypotension, normotension, and hypertension-on the basis of invasive measurements of mean arterial blood pressure (MAP). The NIBP and IBP measurements of systolic and diastolic arterial blood pressure (SAP and DAP, respectively) and MAP were compared.

RESULTS

NIBP measurements were frequently lower than IBP measurements. The greatest underestimation was for the hypertension subset of NIBP measurements, with biases for SAP of 15.7 mm Hg, DAP of 14.1 mm Hg, and MAP of 12.0 mm Hg. Considering the complete data set, precision was acceptable (SD of the differences between paired measurements ≤ 15 mm Hg for DAP [9.0 mm Hg] and MAP [12.1 mm Hg]); however, precision was not acceptable for SAP (SD, 18.6 mm Hg).

CONCLUSIONS AND CLINICAL RELEVANCE

NIBP measurements with the studied veterinary-specific multiparameter monitor generally agreed with IBP measurements during hypotensive and normotensive periods for anesthetized healthy female dogs undergoing routine ovariohysterectomy. However, inaccuracies, frequently underestimations, were observed during periods of hypertension, and therefore, NIBP measurements should be interpreted cautiously.

Vasopressor Therapy and Blood Pressure Management in the Setting of Acute Kidney Injury

Acute kidney injury (AKI) is common in the setting of shock. Hemodynamic instability is a risk factor for the development of AKI, and pathophysiological mechanisms include loss of renal perfusion pressure and impaired microcirculation. Although restoration of mean arterial pressure (MAP) may mitigate the risk of AKI to some extent, evidence on this is conflicting. Also debatable is the optimal blood pressure needed to minimize the risk of kidney injury. A MAP of 65 mm Hg traditionally has been considered adequate to maintain renal perfusion pressure, and studies have failed to consistently show improved outcomes at higher levels of MAP. Therapeutic options to support renal perfusion consist of catecholamines, vasopressin, and angiotensin II. Although catecholamines are the most studied, they are associated with adverse events at higher doses, including AKI. Vasopressin and angiotensin II are noncatecholamine options to support blood pressure and may improve microcirculatory hemodynamics through unique mechanisms, including differential vasoconstriction of efferent and afferent arterioles within the nephron. Future areas of study include methods by which clinicians can measure renal blood flow in a macrocirculatory and microcirculatory way, a personalized approach to blood pressure management in septic shock using patient-specific measures of perfusion adequacy, and novel agents that may improve the microcirculation within the kidneys without causing adverse microcirculatory effects in other organs.

Optimal Mean Arterial Pressure Within 24 Hours of Admission for Patients With Intermediate-Risk and High-Risk Pulmonary Embolism

We aimed to determine whether the average mean arterial pressure (aMAP) in the first 24 hours of hospital admission is useful in predicting short-term outcomes of patients with intermediate- and high-risk pulmonary embolism (PE). We conducted a single-center retrospective study. From May 2012 to April 2019, 122 patients with intermediate- and high-risk PE were included. The primary outcome was in-hospital mortality. The secondary outcome was adverse events. Receiver operating characteristic (ROC) curves and cutoff values for aMAP predicting in-hospital death were computed. According to cutoff values, we categorized 5 groups defined as follows: group 1: aMAP < 70 mm Hg; group 2: 70 mm Hg ≤ aMAP < 80 mm Hg; group 3: 80 mm Hg ≤ aMAP < 90 mm Hg; group 4: 90 mm Hg ≤ aMAP <100 mm Hg; and group 5: aMAP ≥ 100 mm Hg. Cox regression models were calculated to investigate associations between aMAP and in-hospital death. In the study group of 122 patients, 15 (12.30%) patients died in the hospital due to PE. The ROC analysis for MAP predicting in-hospital death revealed an area under the curve of 0.729 with a cutoff value of 79.4 mm Hg. Cox regression models showed a significant association between in-hospital death and aMAP group 1 (ref), aMAP group 2 (odds ratio [OR] = 1.680, 95% CI: 0.020-140.335), aMAP group 3 (OR = 0.003, 95% CI: 0.0001-0.343), aMAP group 4 (OR = 0.006, 95% CI: 0.0001-1.671), and aMAP group 5 (OR = 0.003, 95% CI: 0.0001-9.744). In particular, those with an aMAP of 80 to 90 mm Hg had minimum adverse events. The optimal range of MAP for patients with intermediate- and high-risk PE may be 80 to 90 mm Hg.

Is dynamic arterial elastance a predictor of an increase in blood pressure after fluid administration in pediatric patients with hypotension? Reanalysis of prospective observational studies

BACKGROUND

Dynamic arterial elastance (Ea_dyn ) has been proposed to predict an increase in mean arterial pressure (MAP) after volume expansion in hypotensive adults. We aimed to evaluate the clinical usefulness of Ea_dyn as a predictor of arterial pressure response after fluid loading in pediatric patients with hypotension.

METHODS

We re-analyzed data of 63 hypotensive children (age, ≤5 years), collected from three previous prospective observational studies about fluid responsiveness. Pulse pressure variation (PPV), stroke volume variation (SVV), and respiratory variation in aortic blood flow velocity (ΔVpeak) were used to calculate Ea_dyn (PPV/SVV) and modified Ea_dyn (PPV/ΔVpeak). Preload-dependent patients were defined as those with ΔVpeak ≥12% before fluid loading. Patients were classified as pressure responders, if their MAP increased ≥15% after fluid administration.

RESULTS

Mean Ea_dyn (SD) was 1.06 (0.47) in pressure responders (n=39) and 0.99 (0.48) in nonresponders (n = 24) (mean difference, 0.08; 95% confidence interval [CI], -0.19-0.34; P = .567). Additionally, mean modified Ea_dyn was 1.27 (0.64) in responders and 1.11 (0.43) in nonresponders (mean difference, 0.17; 95% CI, -0.13-0.46; P = 0.269). Both Ea_dyn (AUC 0.506; 95% confidence interval [CI], 0.337 to 0.675; P = 0.948) and modified Ea_dyn (AUC 0.498; 95% CI, 0.328-0.669; P = 0.983), as well as other dynamic variables, could not predict pressure responsiveness in children. Sub-group analysis revealed similar findings in both in 39 preload-dependent and hypotensive patients (26 pressure responders and 13 nonpressure responders).

CONCLUSION

Both Ea_dyn and modified Ea_dyn cannot predict whether blood pressure increases with fluid administration in pediatric patients with hypotension.

Portal hyperperfusion after major liver resection and associated sinusoidal damage is a therapeutic target to protect the remnant liver

Extended liver resection results in loss of a large fraction of the hepatic vascular bed, thereby causing abrupt alterations in perfusion of the remnant liver. Mechanisms of hemodynamic adaptation and associated changes in oxygen metabolism after liver resection and the effect of mechanical portal blood flow reduction were assessed. A pig model (n = 16) of extended partial hepatectomy was established that included continuous observation for 24 h under general anesthesia. Pigs were randomly separated into two groups, one with a portal flow reduction of 70% compared with preoperative values, and the other as a control (n = 8, each). In controls, portal flow [mean (SD)] increased from 74 (8) mL·min^-1·100 g^-1 preoperatively to 240 (48) mL·min^-1·100 g^-1 at 6 h after resection (P < 0.001). Hepatic arterial buffer response was abolished after resection. Oxygen uptake per unit liver mass increased from 4.0 (1.1) mL·min^-1·100 g^-1 preoperatively to 7.7 (1.7) mL·min^-1·100 g^-1 8 h after resection (P = 0.004). Despite this increase in relative oxygen uptake, total hepatic oxygen consumption (V̇o₂) was not maintained, and markers of hypoxia and anaerobic metabolism were significantly increased in hepatocytes after resection. Reduced postoperative portal flow was associated with significantly decreased levels of aspartate aminotransferase and bilirubin and increased hepatic clearance of indocyanine green. In conclusion, major liver resection was associated with persistent portal hyperperfusion, loss of the hepatic arterial buffer response, decreased total hepatic V̇o₂ and with increased anaerobic metabolism. Portal flow modulation by partial portal vein occlusion attenuated liver injury after extended liver resection.NEW & NOTEWORTHY Because of continuous monitoring, the experiments allow precise observation of the influence of liver resection on systemic and local abdominal hemodynamic alterations and oxygen metabolism. Major liver resection is associated with significant and persistent portal hyperperfusion and loss of hepatic arterial buffer response. The correlation of portal hyperperfusion and parameters of liver injury and dysfunction offers a novel therapeutic option to attenuate liver injury after extended liver resection.

Effects of fluid and norepinephrine resuscitation in a sheep model of endotoxin shock and acute kidney injury

The pathophysiology of renal failure in septic shock is complex. Although microvascular dysfunction has been proposed as a mechanism, there are controversial findings about the characteristics of microvascular redistribution and the effects of resuscitation. Our hypothesis was that the normalization of systemic hemodynamics with fluids and norepinephrine fails to improve acute kidney injury. To test this hypothesis, we assessed systemic and renal hemodynamics and oxygen metabolism in 24 anesthetized and mechanically ventilated sheep. Renal cortical microcirculation was evaluated by SDF-videomicroscopy. Shock ( n = 12) was induced by intravenous administration of endotoxin. After 60 min of shock, 30 mL/kg of saline solution was infused and norepinephrine was titrated to reach a mean blood pressure of 70 mmHg for 2 h. These animals were compared with a sham group ( n = 12). After endotoxin administration, mean blood pressure, cardiac index, and systemic O2 transport and consumption decreased ( P < 0.05 for all). Resuscitation improved these variables. Endotoxin shock also reduced renal blood flow and O2 transport and consumption (205[157–293] vs. 131 [99–185], 28.4[19.0–38.2] vs. 15.8[13.5–23.2], and 5.4[4.0–8.8] vs. 3.7[3.3–4.5] mL·min−1·100 g−1, respectively); cortical perfused capillary density (23.8[23.5–25.9] vs. 17.5[15.1–19.0] mm/mm2); and creatinine clearance (62.4[39.2–99.4] vs. 10.7[4.4–23.5] mL/min). After 2 h of resuscitation, these variables did not improve (174[91–186], 20.5[10.8–22.7], and 3.8[1.9–4.8] mL·min−1·100 g−1, 19.9[18.6–22.1] mm/mm2, and 5.9[1.0–11.9] mL/min). In conclusion, endotoxin shock induced severe renal failure associated with decreased renal flow, O2 transport and consumption, and cortical microcirculation. Normalization of systemic hemodynamics with fluids and norepinephrine failed to improve renal perfusion, oxygenation, and function.

NEW & NOTEWORTHY This experimental model of endotoxin shock induced severe renal failure, which was associated with abnormalities in renal regional blood flow, microcirculation, and oxygenation. Derangements included the compromise of peritubular microvascular perfusion. Improvements in systemic hemodynamics through fluids and norepinephrine were unable to correct these abnormalities.

The tidal volume challenge improves the reliability of dynamic preload indices during robot-assisted laparoscopic surgery in the Trendelenburg position with lung-protective ventilation

Background

The reliability of pulse pressure variation (PPV) and stroke volume variation (SVV) is controversial under pneumoperitoneum. In addition, the usefulness of these indices is being called into question with the increasing adoption of lung-protective ventilation using low tidal volume (V_T) in surgical patients. A recent study indicated that changes in PPV or SVV obtained by transiently increasing V_T (V_T challenge) accurately predicted fluid responsiveness even in critically ill patients receiving low V_T. We evaluated whether the changes in PPV and SVV induced by a V_T challenge predicted fluid responsiveness during pneumoperitoneum.

Methods

We performed an interventional prospective study in patients undergoing robot-assisted laparoscopic surgery in the Trendelenburg position under lung-protective ventilation. PPV, SVV, and the stroke volume index (SVI) were measured at a V_T of 6 mL/kg and 3 min after increasing the V_T to 8 mL/kg. The V_T was reduced to 6 mL/kg, and measurements were performed before and 5 min after volume expansion (infusing 6% hydroxyethyl starch 6 ml/kg over 10 min). Fluid responsiveness was defined as ≥15% increase in the SVI.

Results

Twenty-four of the 38 patients enrolled in the study were responders. In the receiver operating characteristic curve analysis, an increase in PPV > 1% after the V_T challenge showed excellent predictive capability for fluid responsiveness, with an area under the curve (AUC) of 0.95 [95% confidence interval (CI), 0.83–0.99, P < 0.0001; sensitivity 92%, specificity 86%]. An increase in SVV > 2% after the V_T challenge predicted fluid responsiveness, but showed only fair predictive capability, with an AUC of 0.76 (95% CI, 0.60–0.89, P < 0.0006; sensitivity 46%, specificity 100%). The augmented values of PPV and SVV following V_T challenge also showed the improved predictability of fluid responsiveness compared to PPV and SVV values (as measured by V_T) of 6 ml/kg.

Conclusions

The change in PPV following the V_T challenge has excellent reliability in predicting fluid responsiveness in our surgical population. The change in SVV and augmented values of PPV and SVV following this test are also reliable.

Trial registration

This trial was registered with Clinicaltrials.gov, NCT03467711, 10th March 2018.

Untreated Relative Hypotension Measured as Perfusion Pressure Deficit During Management of Shock and New-Onset Acute Kidney Injury-A Literature Review

Maintaining an optimal blood pressure (BP) during shock is a fundamental tenet of critical care. Optimal BP targets may be different for different patients. In current practice, too often, uniform BP targets are pursued which may result in inadvertently accepting a degree of untreated relative hypotension, i.e., the deficit between patients' usual premorbid basal BP and the achieved BP, during vasopressor support. Relative hypotension is a common but an under-recognized and an under-treated sign among patients with potential shock state. From a physiological perspective, any relative reduction in the net perfusion pressure across an organ (e.g., renal) vasculature has a potential to overwhelm autoregulatory mechanisms, which are already under stress during shock. Such perfusion pressure deficit may consequently impact organs' ability to function or recover from an injured state. This review discusses such pathophysiologic mechanisms in detail with a particular focus on the risk of new-onset acute kidney injury (AKI). To review current literature, databases of Medline, Embase, and Google scholar were searched to retrieve articles that either adjusted BP targets based on patients' premorbid BP levels or considered relative hypotension as an exposure endpoint and assessed its association with clinical outcomes among acutely ill patients. There were no randomized controlled trials. Only seven studies could be identified and these were reviewed in detail. These studies indicated a significant association between the degree of relative hypotension that was inadvertently accepted in real-world practice and new-onset organ dysfunction or subsequent AKI. However, this is not a high-quality evidence. Therefore, well-designed randomized controlled trials are needed to evaluate whether adoption of individualized BP targets, which are initially guided by patient's premorbid basal BP and then tailored according to clinical response, is superior to conventional BP targets for vasopressor therapy, particularly among patients with vasodilatory shock states.

Mean arterial pressure during targeted temperature management and renal function after out-of-hospital cardiac arrest

PURPOSE

This study investigates the association between mean arterial pressure (MAP) and renal function after out-of-hospital cardiac arrest (OHCA).

MATERIALS AND METHODS

Post-hoc analysis of 851 comatose OHCA-patients surviving >48 h included in the targeted temperature management (TTM)-trial.

RESULTS

Patients were stratified by mean MAP during TTM in the following groups; <70 mmHg (22%), 70-80 mmHg (43%), and > 80 mmHg (35%). Median (interquartile range) eGFR (ml/min/1.73 m²) 48 h after OHCA was inversely associated with MAP-group (70 (47-102), 84 (56-113), 94 (61-124), p < .001, for the <70-group, 70-80-group and > 80-group respectively). After adjusting for potential confounders, in a mixed model including eGFR after 1, 2 and 3 days this association remained significant (p_{group_adjusted} = 0.0002). Higher mean MAP was independently associated with lower odds of renal replacement therapy (odds ratio_adjusted = 0.77 [95% confidence interval, 0.65-0.91] per 5 mmHg increase; p = .002]).

CONCLUSIONS

Low mean MAP during TTM was independently associated with decreased renal function and need of renal replacement therapy in a large cohort of comatose OHCA-patients. Increasing MAP above the recommended 65 mmHg could potentially be renal-protective. This hypothesis should be investigated in prospective trials.

Comparison of mortality prediction models in acute respiratory distress syndrome undergoing extracorporeal membrane oxygenation and development of a novel prediction score: the PREdiction of Survival on ECMO Therapy-Score (PRESET-Score)

Background

Extracorporeal membrane oxygenation (ECMO) is a life-saving therapy in acute respiratory distress syndrome (ARDS) patients but is associated with complications and costs. Here, we validate various scores supposed to predict mortality and develop an optimized categorical model.

Methods

In a derivation cohort, 108 ARDS patients (2010–2015) on veno-venous ECMO were retrospectively analysed to assess four established risk scores (ECMOnet-Score, RESP-Score, PRESERVE-Score, Roch-Score) for mortality prediction (receiver operating characteristic analysis) and to identify by multivariable logistic regression analysis independent variables for mortality to yield the new PRESET-Score (PREdiction of Survival on ECMO Therapy-Score). This new score was then validated both in independent internal (n = 82) and external (n = 59) cohorts.

Results

The median (25%; 75% quartile) Sequential Organ Failure Assessment score was 14 (12; 16), Simplified Acute Physiology Score II was 62.5 (57; 72.8), median intensive care unit stay was 17 days (range 1–124), and mortality was 62%. Only the ECMOnet-Score (area under curve (AUC) 0.69) and the RESP-Score (AUC 0.64) discriminated survivors and non-survivors. Admission pH_a, mean arterial pressure, lactate, platelet concentrations, and pre-ECMO hospital stay were independent predictors of death and were used to build the PRESET-Score. The score’s internal (AUC 0.845; 95% CI 0.76–0.93; p < 0.001) and external (AUC 0.70; 95% CI 0.56–0.84; p = 0.008) validation revealed excellent discrimination.

Conclusions

While our data confirm that both the ECMOnet-Score and the RESP-Score predict mortality in ECMO-treated ARDS patients, we propose a novel model also incorporating extrapulmonary variables, the PRESET-Score. This score predicts mortality much better than previous scores and therefore is a more precise choice for decision support in ARDS patients to be placed on ECMO.

Muscle membrane properties in A pig sepsis model: Effect of norepinephrine

INTRODUCTION

Sepsis-induced myopathy and critical illness myopathy are common causes of muscle weakness in intensive care patients. This study investigated the effect of different mean arterial blood pressure (MAP) levels on muscle membrane properties following experimental sepsis.

METHODS

Sepsis was induced with fecal peritonitis in 12 of 18 anesthetized and mechanically ventilated pigs. Seven were treated with a high (75-85 mmHg) and 5 were treated with a low (≥60 mmHg) MAP target for resuscitation. In septic animals, resuscitation was started 12 h after peritonitis induction, and muscle velocity recovery cycles were recorded 30 h later.

RESULTS

Muscles in the sepsis/high MAP group showed an increased relative refractory period and reduced early supernormality compared with the remaining septic animals and the control group, indicating membrane depolarization and/or sodium channel inactivation. The membrane abnormalities correlated positively with norepinephrine dose.

DISCUSSION

Norepinephrine may contribute to sepsis-induced abnormalities in muscle by impairing microcirculation. Muscle Nerve 57: 808-813, 2018.

Heart-rate variability depression in porcine peritonitis-induced sepsis without organ failure

Depression of heart-rate variability (HRV) in conditions of systemic inflammation has been shown in both patients and experimental animal models and HRV has been suggested as an early indicator of sepsis. The sensitivity of HRV-derived parameters to the severity of sepsis, however, remains unclear. In this study we modified the clinically relevant porcine model of peritonitis-induced sepsis in order to avoid the development of organ failure and to test the sensitivity of HRV to such non-severe conditions. In 11 anesthetized, mechanically ventilated and instrumented domestic pigs of both sexes, sepsis was induced by fecal peritonitis. The dose of feces was adjusted and antibiotic therapy was administered to avoid multiorgan failure. Experimental subjects were screened for 40 h from the induction of sepsis. In all septic animals, sepsis with hyperdynamic circulation and increased plasma levels of inflammatory mediators developed within 12 h from the induction of peritonitis. The sepsis did not progress to multiorgan failure and there was no spontaneous death during the experiment despite a modest requirement for vasopressor therapy in most animals (9/11). A pronounced reduction of HRV and elevation of heart rate developed quickly (within 5 h, time constant of 1.97 ± 0.80 h for HRV parameter TINN) upon the induction of sepsis and were maintained throughout the experiment. The frequency domain analysis revealed a decrease in the high-frequency component. The reduction of HRV parameters and elevation of heart rate preceded sepsis-associated hemodynamic changes by several hours (time constant of 11.28 ± 2.07 h for systemic vascular resistance decline). A pronounced and fast reduction of HRV occurred in the setting of a moderate experimental porcine sepsis without organ failure. Inhibition of parasympathetic cardiac signaling probably represents the main mechanism of HRV reduction in sepsis. The sensitivity of HRV to systemic inflammation may allow early detection of a moderate sepsis without organ failure. Impact statement A pronounced and fast reduction of heart-rate variability occurred in the setting of a moderate experimental porcine sepsis without organ failure. Dominant reduction of heart-rate variability was found in the high-frequency band indicating inhibition of parasympathetic cardiac signaling as the main mechanism of heart-rate variability reduction. The sensitivity of heart-rate variability to systemic inflammation may contribute to an early detection of moderate sepsis without organ failure.

Mitochondrial and endoplasmic reticulum dysfunction and related defense mechanisms in critical illness-induced multiple organ failure

Patients with critical illness-induced multiple organ failure suffer from a very high morbidity and mortality, despite major progress in intensive care. The pathogenesis of this condition is complex and incompletely understood. Inadequate tissue perfusion and an overwhelming inflammatory response with pronounced cellular damage have been suggested to play an important role, but interventions targeting these disturbances largely failed to improve patient outcome. Hence, new therapeutic perspectives are urgently needed. Cellular dysfunction, hallmarked by mitochondrial dysfunction and endoplasmic reticulum stress, is increasingly recognized as an important contributor to the development of organ failure in critical illness. Several cellular defense mechanisms are normally activated when the cell is in distress, but may fail or respond insufficiently to critical illness. This insight may open new therapeutic options by stimulating these cellular defense mechanisms. This review summarizes the current understanding of the role of mitochondrial dysfunction and endoplasmic reticulum stress in critical illness-induced multiple organ failure and gives an overview of the corresponding cellular defense mechanisms. Therapeutic perspectives based on these cellular defense mechanisms are discussed. This article is part of a Special Issue entitled: Immune and Metabolic Alterations in Trauma and Sepsis edited by Dr. Raghavan Raju.

Demonstrating Value: A Case Study of Enhanced Recovery

An enhanced recovery after surgery strategy will be increasingly adopted in the era of value-based care. The various elements in each enhanced recovery after surgery protocol are likely to add value to the overall patient surgical journey. Although the evidence varies considerably based on type of surgery and patient group, the team-based approach of care should be universally applied to patient care. This article provides an overview of up-to-date techniques and methodology for enhanced recovery, including an overview of value-based care, delivery, and the evidence base supporting enhanced recovery after surgery.

Current concepts on hemodynamic support and therapy in septic shock

Severe sepsis and septic shock represent a major healthcare challenge. Much of the improvement in mortality associated with septic shock is related to early recognition combined with timely fluid resuscitation and adequate antibiotics administration. The main goals of septic shock resuscitation include intravascular replenishment, maintenance of adequate perfusion pressure and oxygen delivery to tissues. To achieve those goals, fluid responsiveness evaluation and complementary interventions - i.e. vasopressors, inotropes and blood transfusion - may be necessary. This article is a literature review of the available evidence on the initial hemodynamic support of the septic shock patients presenting to the emergency room or to the intensive care unit and the main interventions available to reach those targets, focusing on fluid and vasopressor therapy, blood transfusion and inotrope administration.

Arterial blood pressure targets in septic shock: is it time to move to an individualized approach?

Xu and colleagues evaluated the impact of increasing mean arterial blood pressure levels through norepinephrine administration on systemic hemodynamics, tissue perfusion, and sublingual microcirculation of septic shock patients with chronic hypertension. The authors concluded that, although increasing arterial blood pressure improved sublingual microcirculation parameters, no concomitant improvement in systemic tissue perfusion indicators was found. Here, we discuss why resuscitation targets may need to be individualized, taking into account the patient’s baseline condition, and present directions for future research in this field.

Endotoxemic myocardial dysfunction: subendocardial collagen deposition related to coronary driving pressure

Sepsis impairs the autoregulation of myocardial microcirculatory blood flow, but whether this impairment is correlated with myocardial remodeling is unknown. This study investigated the role of coronary driving pressure (CDP) as a determinant of microcirculatory blood flow and myocardial fibrosis in endotoxemia and sepsis. The study is composed of two parts: a prospective experimental study and an observational clinical study. The experimental study was performed on male Wistar rats weighing 300 to 320 g. Endotoxemia was induced in rats by lipopolysaccharide (LPS) injection (10 mg·kg intraperitoneally). Hemodynamic evaluation was performed 1.5 to 24 h after LPS injection by measuring the mean arterial pressure, CDP, left ventricular end-diastolic pressure, dP/dtmax, and dP/dtmin. Microspheres were also infused into the left ventricle to measure myocardial blood flow, and myocardial tissue was histologically assessed to analyze collagen deposition. The CDP, mean arterial pressure, and myocardial blood flow were reduced by 55%, 30%, and 70%, respectively, in rats 1.5 h after LPS injection compared with phosphate buffer saline injection (P < 0.05). The CDP was significantly correlated with subendocardial blood flow (r = 0.73) and fibrosis (r = 0.8). Left ventricular function was significantly impaired in the LPS-treated rats, as demonstrated by dP/dtmax (6,155 ± 455 vs. 3,746 ± 406 mmHg·s, baseline vs. LPS; P < 0.05) and dP/dtmin (-5,858 ± 236 vs. -3,516 ± 436 mmHg·s, baseline vs. LPS; P < 0.05). The clinical study was performed on 28 patients with septic shock analyzed for CDP. The CDP data and histological slices were collected from septic patients. In addition, the clinical data demonstrated fibrosis and 45% CDP reduction in nonsurvivors compared with survivors. In conclusion, the left ventricular subendocardial blood flow was positively correlated with CDP, and higher CDP was negatively correlated with myocardial collagen deposition. Thus, early reductions in myocardial blood flow and CDP facilitate late myocardial fibrosis in rats and likely in humans.

Mean arterial pressure and mean perfusion pressure deficit in septic acute kidney injury

BACKGROUND

Changes in mean perfusion pressure (MPP) from premorbid resting values may contribute to the progression of septic acute kidney injury (AKI).

OBJECTIVES

In patients with septic shock, we aimed to investigate the association of changes from premorbid values with AKI severity and progression.

METHODS

We obtained premorbid resting mean arterial pressure (MAP), central venous pressure (CVP), and MPP, and then recorded data from intensive care unit admission 2 hourly for the first 24 hours to calculate hemodynamic deficits. We recorded 4-hourly creatinine measurements for 96 hours. The association of hemodynamic variables with progression of AKI by Kidney Disease: Improving Global Outcomes ≥2 stages was explored by multivariate logistic regression.

RESULTS

Of 107 patients, 55 (51.4%) had severe AKI. Median MAP deficit was similar for patients with or without severe AKI. Median MPP deficit was 29% in patients with severe AKI and 24% in those without (P = .04), a difference determined by greater CVP levels. Central venous pressure was independently associated with worsening AKI (odds ratio, 1.26 [95% confidence interval, 1.01-1.58]; P = .04).

CONCLUSIONS

Mean arterial pressure and MPP deficits were substantial in septic shock patients, with patients with severe AKI having a greater MPP deficit. However, only CVP was independently associated with AKI progression. These findings suggest a possible role for venous congestion in septic AKI.

Effects of early hemodynamic resuscitation on left ventricular performance and microcirculatory function during endotoxic shock

Background

Microcirculation and macrohemodynamics are severely compromised during septic shock. However, the relationship between these two compartments needs to be further investigated. We hypothesized that early resuscitation restores left ventricular (LV) performance and microcirculatory function but fails to prevent metabolic disorders. We studied the effects of an early resuscitation protocol (ERP) on LV pressure/volume loops-derived parameters, sublingual microcirculation, and metabolic alterations during endotoxic shock.

Methods

Twenty-five pigs were randomized into three groups: LPS group: Escherichia coli lipopolysaccharide (LPS); ERP group: LPS + ERP based on volume expansion, dobutamine, and noradrenaline infusion; Sham group. LV pressure/volume-derived parameters, systemic hemodynamics, sublingual microcirculation, and metabolic profile were assessed at baseline and after completing the resuscitation protocol.

Results

LPS significantly decreased LV end-diastolic volume, myocardial contractility, stroke work, and cardiac index (CI). Early resuscitation preserved preload, and myocardial contractility, increased CI and heart rate (p < .05). LPS severely diminished sublingual microvascular flow index (MFI), perfused vascular density (PVD), and the proportion of perfused vessels (PPV), while increased the heterogeneity flow index (HFI) (p < .05). Despite MFI was relatively preserved, MVD, PVD, and HFI were significantly impaired after resuscitation (p < .05). The macro- and microcirculatory changes were associated with increased lactic acidosis and mixed venous O₂ saturation when compared to baseline values (p < .05). The scatter plot between mean arterial pressure (MAP) and MFI showed a biphasic relationship, suggesting that the values were within the limits of microvascular autoregulation when MAP was above 71 ± 6 mm Hg (R² = 0.63).

Conclusions

Early hemodynamic resuscitation was effective to restore macrohemodynamia and myocardial contractility. Despite MAP and MFI were relatively preserved, the persistent microvascular dysfunction could explain metabolic disorders. The relationship between micro- and systemic hemodynamia and their impact on cellular function and metabolism needs to be further studied during endotoxic shock.

Electronic supplementary material

The online version of this article (doi:10.1186/s40635-015-0049-y) contains supplementary material, which is available to authorized users.

A high mean arterial pressure target is associated with improved microcirculation in septic shock patients with previous hypertension: a prospective open label study

Introduction

The effect of mean arterial pressure titration to a higher level on microcirculation in septic shock patients with previous hypertension remains unknown. Our goal is to assess the effect of mean arterial pressure titration to a higher level on microcirculation in hypertensive septic shock patients.

Methods

This is a single-center, open-label study. Hypertensive patients with septic shock for less than 24 hours after adequate fluid resuscitation and requiring norepinephrine to maintain a mean arterial pressure of 65 mmHg were enrolled. Mean arterial pressure was then titrated by norepinephrine from 65 mmHg to the normal level of the patient. In addition to hemodynamic variables, sublingual microcirculation was evaluated by sidestream dark field imaging.

Results

Nineteen patients were enrolled in the study. Increasing mean arterial pressure from 65 mmHg to normal levels was associated with increased central venous pressure (from 11 ± 4 to 13 ± 4 mmHg, P = 0.002), cardiac output (from 5.4 ± 1.4 to 6.4 ± 2.1 l/minute, P = 0.001), and central venous oxygen saturation (from 81 ± 7 to 83 ± 7%, P = 0.001). There were significant increases in small perfused vessel density (from 10.96 ± 2.98 to 11.99 ± 2.55 vessels/mm², P = 0.009), proportion of small perfused vessels (from 85 ± 18 to 92 ± 14%, P = 0.002), and small microvascular flow index (from 2.45 ± 0.61 to 2.80 ± 0.68, P = 0.009) when compared with a mean arterial pressure of 65 mmHg.

Conclusions

Increasing mean arterial pressure from 65 mmHg to normal levels is associated with improved microcirculation in hypertensive septic shock patients.

Trial registration

Clinicaltrials.gov: NCT01443494; registered 28 September 2011.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-015-0866-0) contains supplementary material, which is available to authorized users.

Optimizing mean arterial pressure in septic shock: a critical reappraisal of the literature

Guidelines recommend that a mean arterial pressure (MAP) value greater than 65 mm Hg should be the initial blood pressure target in septic shock, but what evidence is there to support this statement? We searched Pubmed and Google Scholar by using the key words 'arterial pressure', 'septic shock', and 'norepinephrine' and retrieved human studies published between 1 January 2000 and 31 July 2014. We identified seven comparative studies: two randomized clinical trials and five observational studies. The results of the literature review suggest that a MAP target of 65 mm Hg is usually sufficient in patients with septic shock. However, a MAP of around 75 to 85 mm Hg may reduce the development of acute kidney injury in patients with chronic arterial hypertension. Because of the high prevalence of chronic arterial hypertension in patients who develop septic shock, this finding is of considerable importance. Future studies should assess interactions between time, fluid volumes administered, and doses of vasopressors.

Increased cardiac index attenuates septic acute kidney injury: a prospective observational study

Background

The relationship between cardiac output and septic acute kidney injury (AKI) remains unclear. The purpose of this study was to assess the association between the cardiac index (CI) and the renal outcomes in patients with septic shock.

Methods

A one-year prospective cohort study was performed in the surgical and medical ICU of a teaching hospital in Nanjing, China. Twenty-nine septic shock patients who required early goal-directed fluid resuscitation were consecutively included. Pulse indicator continuous cardiac output (PiCCO) device was used to measure hemodynamic parameters before and after early goal-directed therapy (EGDT). Based on CI changes after EGDT, patients were assign to the CI increased group or the CI constant group, respectively. The incidence of poor renal outcome, which was defined as AKI on admission without recovery in following three days or new onset AKI within 28 days, was recorded. We investigated whether an increased CI was associated with a better renal outcome.

Results

After EGDT, there were 16 patients in the CI increased group and 13 patients in the CI constant group. The incidence of poor renal outcome was lower in CI increased group than in the CI constant group (6% vs. 62%; P = 0.003) with a relative risk of 0.10. The logistic regression showed that the CI percent change was associated with renal outcome, with an odd ratio of 0.003 (P = 0.056) after adjustment of possible confounding factors. The CI percent change would predict a good renal outcome (AU ROC 0.739, P = 0.012) with moderate accuracy (sensitivity 75% and specificity 89%) when using a 10% cut-off value from Youden index. The CI percent change was also positively correlated with creatinine clearance (CCr) after EGDT (ρ = 0.548; P = 0.002).

Conclusions

The increased CI after EGDT was a protective factor for kidney in patients with septic shock. A CI increased above 10% could be potentially used to predict development and reversibility of AKI in septic shock patients.

Trial registration

Clinicaltrials.gov:NCT01862588 (May 13, 2013).

The duration of hypotension determines the evolution of bacteremia-induced acute kidney injury in the intensive care unit

Background

Exploration of the impact of severe hypotension on the evolution of acute kidney injury in septic patients.

Methods and Results

We reviewed the hemodynamic parameters of 137 adults with septic shock and proven blood stream infection in the ICU. Severe hypotension was defined as a mean arterial blood pressure (MAP) ≤65 mmHg. The influence of the duration of severe hypotension on the evolution of acute kidney injury was evaluated according to the RIFLE classification, with day 0 defined as the day of a positive blood stream infection. After bloodstream infection, the probability for a patient to be in Failure was significantly higher than before blood stream infection (OR = 1.94, p = 0.0276). Patients have a significantly higher risk of evolving to Failure if the duration of severe hypotension is longer (OR = 1.02 for each 10 minutes increase in duration of a MAP <65 mmHg, p = 0.0472). A cut-off of at least 51 minutes of severe hypotension (<65 mmHg) or at least 5.5 periods of severe hypotension within 1 day identified patients with increased risk to evolve to Failure.

Conclusions

There is a significant influence of both the duration and the number of periods of severe hypotension on the evolution to Failure. Blood stream infection has a significantly negative effect on the relationship between severe hypotension and Failure.

Adenosine, lidocaine and Mg2+ improves cardiac and pulmonary function, induces reversible hypotension and exerts anti-inflammatory effects in an endotoxemic porcine model

Introduction

The combination of Adenosine (A), lidocaine (L) and Mg²⁺ (M) (ALM) has demonstrated cardioprotective and resuscitative properties in models of cardiac arrest and hemorrhagic shock. This study evaluates whether ALM also demonstrates organ protective properties in an endotoxemic porcine model.

Methods

Pigs (37 to 42 kg) were randomized into: 1) Control (n = 8) or 2) ALM (n = 8) followed by lipopolysaccharide infusion (1 μg∙kg^-1∙h^-1) for five hours. ALM treatment consisted of 1) a high dose bolus (A (0.82 mg/kg), L (1.76 mg/kg), M (0.92 mg/kg)), 2) one hour continuous infusion (A (300 μg∙kg^-1 ∙min^-1), L (600 μg∙kg^-1 ∙min^-1), M (336 μg∙kg^-1 ∙min^-1)) and three hours at a lower dose (A (240∙kg^-1∙min^-1), L (480 μg∙kg^-1∙min^-1), M (268 μg∙kg^-1 ∙min^-1)); controls received normal saline. Hemodynamic, cardiac, pulmonary, metabolic and renal functions were evaluated.

Results

ALM lowered mean arterial pressure (Mean value during infusion period: ALM: 47 (95% confidence interval (CI): 44 to 50) mmHg versus control: 79 (95% CI: 75 to 85) mmHg, P <0.0001). After cessation of ALM, mean arterial pressure immediately increased (end of study: ALM: 88 (95% CI: 81 to 96) mmHg versus control: 86 (95% CI: 79 to 94) mmHg, P = 0.72). Whole body oxygen consumption was significantly reduced during ALM infusion (ALM: 205 (95% CI: 192 to 217) ml oxygen/min versus control: 231 (95% CI: 219 to 243) ml oxygen/min, P = 0.016). ALM treatment reduced pulmonary injury evaluated by PaO₂/FiO₂ ratio (ALM: 388 (95% CI: 349 to 427) versus control: 260 (95% CI: 221 to 299), P = 0.0005). ALM infusion led to an increase in heart rate while preserving preload recruitable stroke work. Creatinine clearance was significantly lower during ALM infusion but reversed after cessation of infusion. ALM reduced tumor necrosis factor-α peak levels (ALM 7121 (95% CI: 5069 to 10004) pg/ml versus control 11596 (95% CI: 9083 to 14805) pg/ml, P = 0.02).

Conclusion

ALM infusion induces a reversible hypotensive and hypometabolic state, attenuates tumor necrosis factor-α levels and improves cardiac and pulmonary function, and led to a transient drop in renal function that was reversed after the treatment was stopped.

A multicenter study of the point prevalence of drug-induced hypotension in the ICU

OBJECTIVE

To determine the point prevalence of drug-induced hypotension episodes in critically ill patients, to assess the episodes resulting from error, and to describe how episodes are treated.

DESIGN

Multicenter observational, 24-hour snapshot study.

SETTING

Forty-seven ICUs in 27 institutions located in the United States, Canada, and Singapore.

PATIENTS

A total of 688 ICU patients were evaluated.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Patients were included in the study if they had an episode of hypotension in the 24 hours prior to the clinical pharmacists' evaluation. The definition for a hypotensive episode is either a systolic blood pressure less than 90 mm Hg or a decrease in systolic blood pressure of 30 mm Hg over a 2-hour period. Each episode of unintentional hypotension was assessed for suspected drug-related causes. When a drug-related cause was suspected, an objective assessment tool, the modified Kramer, was used to determine causality. A score of at least "possible" was considered drug induced, referred to as a "drug-related hazardous condition." A drug-related hazardous condition is the temporal gap (intermediate stage) between the identification of an adverse drug reaction and the subsequent onset of drug-induced injury, known as an "adverse drug event." Drug-induced episodes were evaluated for medication errors and treatment. One hundred fifty-eight patients experienced 204 hypotensive episodes that were considered unintentional and drug related. Common drugs implicated included propofol, fentanyl, metoprolol, lorazepam, hydralazine, and furosemide. A total of 54 episodes (26.5%) resulted from medication errors. Common error types were improper dose/quantity (46%) and prescribing (25%). A total of 56.9% episodes were treated.

CONCLUSIONS

Many hypotensive episodes in the ICU are drug related and require treatment. A substantial portion of these episodes result from errors and are therefore preventable. This presents opportunities to improve prescribing including optimizing drug dosing to avoid possible patient harm from drug-induced hypotension.

Association of kidney function and albuminuria with prevalent and incident hypertension: the Atherosclerosis Risk in Communities (ARIC) study

BACKGROUND

Decreased kidney function and kidney damage may predate hypertension, but only a few studies have investigated both types of markers simultaneously, and these studies have obtained conflicting results.

STUDY DESIGN

Cross-sectional for prevalent and prospective observational study for incident hypertension.

SETTING & PARTICIPANTS

9,593 participants from the ARIC (Atherosclerosis Risk in Communities) Study, aged 53-75 years in 1996-1998.

PREDICTORS

Several markers of kidney function (estimated glomerular filtration rate using serum creatinine and/or cystatin C and 2 novel markers [β-trace protein and β2-microglobulin]) and 1 marker of kidney damage (urinary albumin-creatinine ratio [ACR]). Every kidney marker was categorized by its quintiles (top quintile as a reference for estimated glomerular filtration rates and bottom quintile for the rest).

OUTCOMES

Prevalent and incident hypertension.

MEASUREMENTS

Prevalence ratios and HRs of hypertension based on modified Poisson regression and Cox proportional hazards models, respectively.

RESULTS

There were 4,378 participants (45.6%) with prevalent hypertension at baseline and 2,175 incident hypertension cases during a median follow-up of 9.8 years. Although all 5 kidney function markers were associated significantly with prevalent hypertension, prevalent hypertension was associated most notably with higher ACR (adjusted prevalence ratio, 1.60 [95% CI, 1.50-1.71] for the highest vs lowest ACR quintile). Similarly, ACR was associated consistently with incident hypertension in all models tested (adjusted HR, 1.28 [95% CI, 1.10-1.49] for top quintile), while kidney function markers demonstrated significant associations in some, but not all, models. Even mildly increased ACR (9.14-14.0mg/g) was associated significantly with incident hypertension.

LIMITATIONS

Self-reported use of antihypertensive medication for defining incident hypertension, single assessment of kidney markers, and relatively narrow age range.

CONCLUSIONS

Although all kidney markers were associated with prevalent hypertension, only elevated albuminuria was associated consistently with incident hypertension, suggesting that kidney damage is related more closely to hypertension than moderate reduction in overall kidney function.

Sepsis-related hypertensive response: friend or foe?

In daily practice acute arterial hypertension may occur during acute sepsis. No management guidelines concerning this issue figured in the latest sepsis campaign guidelines. Arterial hypertension occurring during sepsis could be an overlooked condition despite its potential haemodynamic harmful consequences. In this paper, a clinical study of acute hypertensive response related to sepsis is detailed. It shows that arterial hypertension, renal salt wasting and glomerular hyperfiltration can occur simultaneously during sepsis. Mechanisms and management options of sepsis-related arterial hypertensive response are also discussed.

Hemodynamic variables and progression of acute kidney injury in critically ill patients with severe sepsis: data from the prospective observational FINNAKI study

Introduction

Knowledge of the association of hemodynamics with progression of septic acute kidney injury (AKI) is limited. However, some recent data suggest that mean arterial pressure (MAP) exceeding current guidelines (60–65 mmHg) may be needed to prevent AKI. We hypothesized that higher MAP during the first 24 hours in the intensive care unit (ICU), would be associated with a lower risk of progression of AKI in patients with severe sepsis.

Methods

We identified 423 patients with severe sepsis and electronically recorded continuous hemodynamic data in the prospective observational FINNAKI study. The primary endpoint was progression of AKI within the first 5 days of ICU admission defined as new onset or worsening of AKI by the Kidney Disease: Improving Global Outcomes (KDIGO) criteria. We evaluated the association of hemodynamic variables with this endpoint. We included 53724 10-minute medians of MAP in the analysis. We analysed the ability of time-adjusted MAP to predict progression of AKI by receiver operating characteristic (ROC) analysis.

Results

Of 423 patients, 153 (36.2%) had progression of AKI. Patients with progression of AKI had significantly lower time-adjusted MAP, 74.4 mmHg [68.3-80.8], than those without progression, 78.6 mmHg [72.9-85.4], P < 0.001. A cut-off value of 73 mmHg for time-adjusted MAP best predicted the progression of AKI. Chronic kidney disease, higher lactate, higher dose of furosemide, use of dobutamine and time-adjusted MAP below 73 mmHg were independent predictors of progression of AKI.

Conclusions

The findings of this large prospective multicenter observational study suggest that hypotensive episodes (MAP under 73 mmHg) are associated with progression of AKI in critically ill patients with severe sepsis.

Association between systemic hemodynamics and septic acute kidney injury in critically ill patients: a retrospective observational study

INTRODUCTION

The role of systemic hemodynamics in the pathogenesis of septic acute kidney injury (AKI) has received little attention. The purpose of this study was to investigate the association between systemic hemodynamics and new or persistent of AKI in severe sepsis.

METHODS

A retrospective study between 2006 and 2010 was performed in a surgical ICU in a teaching hospital. AKI was defined as development (new AKI) or persistent AKI during the five days following admission based on the Acute Kidney Injury Network (AKIN) criteria. We studied the association between the following hemodynamic targets within 24 hours of admission and AKI: central venous pressure (CVP), cardiac output (CO), mean arterial pressure (MAP), diastolic arterial pressure (DAP), central venous oxygen saturation (ScvO2) or mixed venous oxygen saturation (SvO2).

RESULTS

This study included 137 ICU septic patients. Of these, 69 had new or persistent AKI. AKI patients had a higher Simplified Acute Physiology Score (SAPS II) (57 (46 to 67) vs. 45 (33 to 52), P < 0.001) and higher mortality (38% vs. 15%, P = 0.003) than those with no AKI or improving AKI. MAP, ScvO2 and CO were not significantly different between groups. Patients with AKI had lower DAP and higher CVP (P = 0.0003). The CVP value was associated with the risk of developing new or persistent AKI even after adjustment for fluid balance and positive end-expiratory pressure (PEEP) level (OR = 1.22 (1.08 to 1.39), P = 0.002). A linear relationship between CVP and the risk of new or persistent AKI was observed.

CONCLUSIONS

We observed no association between most systemic hemodynamic parameters and AKI in septic patients. Association between elevated CVP and AKI suggests a role of venous congestion in the development of AKI. The paradigm that targeting high CVP may reduce occurrence of AKI should probably be revised. Furthermore, DAP should be considered as a potential important hemodynamic target for the kidney.