Renal arterial resistance in septic shock: effects of increasing mean arterial pressure with norepinephrine on the renal resistive index assessed with Doppler ultrasonography

Kidney Doppler ultrasonography in critical care nephrology

Color pulsed-wave Doppler ultrasound (CPWD-US) emerges as a pivotal tool in intensive care units (ICUs) for diagnosing acute kidney injury (AKI) swiftly and non-invasively. Its bedside accessibility allows for rapid assessments, making it a primary imaging modality for AKI characterization. Furthermore, CPWD-US serves as a guiding instrument for key diagnostic-interventional procedures such as renal needle biopsy and percutaneous nephrostomy, while also facilitating therapy response monitoring and AKI progression tracking. This review shifts focus towards the integration of renal ultrasound into ICU workflows, offering contemporary insights into its utilization through a diagnostic standard-oriented approach. By presenting a flow chart, this review aims to provide practical guidance on the appropriate use of point-of-care ultrasound in critical care scenarios, enhancing diagnostic precision, patient management and safety, albeit amidst a backdrop of limited evidence regarding long-term outcomes.

Linear Correlation Between Mean Arterial Pressure and Urine Output in Critically Ill Patients

OBJECTIVE

Mean arterial pressure (MAP) plays a significant role in regulating tissue perfusion and urine output (UO). The optimal MAP target in critically ill patients remains a subject of debate. We aimed to explore the relationship between MAP and UO.

DESIGN

A retrospective observational study.

SETTING

A general ICU in a tertiary medical center.

PATIENTS

All critically ill patients admitted to the ICU for more than 10 hours.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

MAP values and hourly UO were collected in 5,207 patients. MAP levels were categorized into 10 groups of 5 mm Hg (from MAP < 60 mm Hg to MAP > 100 mg Hg), and 656,423 coupled hourly mean MAP and UO measurements were analyzed. Additionally, we compared the UO of individual patients in each MAP group with or without norepinephrine (NE) support or diuretics, as well as in patients with acute kidney injury (AKI).Hourly UO rose incrementally between MAP values of 65-100 mm Hg. Among 2,226 patients treated with NE infusion, mean UO was significantly lower in the MAP less than 60 mm Hg group (53.4 mL/hr; 95% CI, 49.3-57.5) compared with all other groups (p < 0.001), but no differences were found between groups of 75 less than or equal to MAP. Among 2500 patients with AKI, there was a linear increase in average UO from the MAP less than 60 mm Hg group (57.1 mL/hr; 95% CI, 54.2-60.0) to the group with MAP greater than or equal to 100 mm Hg (89.4 mL/hr; 95% CI, 85.7-93.1). When MAP was greater than or equal to 65 mm Hg, we observed a statistically significant trend of increased UO in periods without NE infusion.

CONCLUSIONS

Our analysis revealed a linear correlation between MAP and UO within the range of 65-100 mm Hg, also observed in the subgroup of patients treated with NE or diuretics and in those with AKI. These findings highlight the importance of tissue perfusion to the maintenance of diuresis and achieving adequate fluid balance in critically ill patients.

Renal and Genitourinary Ultrasound Evaluation in Emergency and Critical Care: An Overview

Renal and genitourinary ultrasound are fundamental resources employed by emergency and critical care healthcare providers to make prompt diagnoses and perform ultrasound-guided procedures. At the bedside, ultrasound can aid in the diagnosis of relevant pathologies, such as post-renal obstruction or kidney stones, and life-threatening conditions such as aortic dissection or hemoperitoneum. A narrative overview was performed, providing an updated review of renal and genitourinary ultrasound for emergency and critical care healthcare providers, emphasizing its advantages and the latest advances in the field. A thorough summary that can be utilized as a guide for emergency and critical care healthcare providers is presented. The daily hemodynamic management of critically ill patients involves the implementation of new protocols, such as VexUS or the evaluation of the renal resistance index. The role of ultrasound in managing acute nephropathy and genitourinary issues is increasingly crucial given its bedside availability, thus this imaging modality not only facilitates the initiation of therapeutic interventions but also provides swift prognostic insights that are vital to provide tailored patient care. As further advances in ultrasound will arise, it is important for healthcare providers to foster the use of these technologies capable of improving patient outcomes.

Acute kidney injury in children undergoing cardiac surgery: predictive value of kidney arterial Doppler-based variables

BACKGROUND

Acute kidney injury (AKI) is a common condition in critically ill children and is associated with increased morbidity and mortality. This study aimed to assess the performance of point-of-care ultrasonography to predict AKI in children undergoing cardiac surgery.

METHODS

In this prospective study, consecutive children underwent kidney Doppler ultrasound examination within 24 h following cardiac surgery, and an experienced operator obtained both renal resistive index (RRI) and renal pulsatility index (RPI). AKI was defined by the Kidney Disease Improving Global Outcome (KDIGO) criteria. The primary outcome was the diagnosis of severe AKI (KDIGO stage 2 or 3) on day 3.

RESULTS

A total of 58 patients were included. Median age and weight were 12.9 months (IQR 6.0-37.9) and 7.36 kg (IQR 5.19-11.40), respectively. On day 3, 13 patients were classified as having AKI, of which 11 were severe. RRI could effectively predict AKI (area under the ROC curve [AUC] 0.83, 95% CI 0.71-0.92; p < 0.001) as well as RPI (AUC 0.81, 95% CI 0.69-0.90; p < 0.001). The optimal cutoff value for RRI was 0.85 (sensitivity, 73%; specificity, 83%; positive predictive value [PPV], 50%; and negative predictive value [NPV], 93%), while for RPI was 1.95 (sensitivity, 73%; specificity, 78%; PPV, 44%; and NPV, 92%). Similar results were found in the analysis for prediction on day 5. Significant correlations were found between Doppler-based variables and estimated GFR and furosemide dose on day 3.

CONCLUSIONS

Kidney Doppler ultrasound may be a promising tool for predicting AKI in children undergoing cardiac surgery.

Impact of Norepinephrine and Dopamine Infusion on Renal Arterial Resistive Index during Pre-Emptive Living Donor Kidney Transplantation: Propensity Score Matching Analysis

Background: Living donor kidney transplantation (LDKT) is a crucial treatment for end-stage renal disease, with pre-emptive LDKT (transplantation before dialysis initiation) offering significant benefits in graft function and patient survival. The selection of a vasopressor during LDKT, particularly between norepinephrine and dopamine, and its impact on renal arterial hemodynamics measured using the renal arterial resistive index (RARI) is poorly understood. Methods: This retrospective observational cohort study enrolled 347 eligible pre-emptive LDKT recipients from the Seoul St. Mary's Hospital between January 2019 and June 2023. Utilizing propensity score matching (PSM), the patients were categorized into dopamine and norepinephrine groups to compare the effects of these vasopressors on the intraoperative RARI, postoperative estimated glomerular filtration rate (eGFR), and hourly urine output. The RARI was measured via the Doppler ultrasonography of the renal hilum and parenchyma post-graft vascular and ureteral anastomoses. Results: The preoperative differences in the recipients' and donors' characteristics were mitigated following PSM. The dopamine group exhibited higher intraoperative RARI values at the renal hilum (0.77 ± 0.11 vs. 0.66 ± 0.13, p < 0.001) and parenchyma (0.71 ± 0.1 vs. 0.6 ± 0.1, p < 0.001) compared to those of the norepinephrine group. However, these differences were not statistically significant on postoperative day 7. The norepinephrine infusion adjusted for the propensity scores was associated with significantly lower odds of an RARI > 0.8 (hilum: OR = 0.214, 95% CI = 0.12-0.382, p < 0.001; parenchyma: OR = 0.1, 95% CI = 0.029-0.348, p < 0.001). The early postoperative outcomes showed a higher eGFR (day 1: 30.0 ± 13.3 vs. 25.1 ± 17.4 mL/min/1.73 m2, p = 0.004) and hourly urine output (day 1: 41.8 ± 16.9 vs. 36.5 ± 14.4 mL/kg/h, p = 0.002) in the norepinephrine group. Furthermore, the long-term outcomes were comparable between the groups. Conclusions: Norepinephrine infusion during pre-emptive LDKT is associated with more favorable intraoperative renal arterial hemodynamics, as evidenced by a lower RARI and improved early postoperative renal function compared to those of dopamine. These findings suggest a potential preferential role for norepinephrine in optimizing perioperative management and early graft functions in LDKT recipients. Given the retrospective nature of this study, further prospective studies are needed to confirm these observations. Additionally, the study limitations include the potential for unmeasured confounding factors and the inability to determine causality due to its observational design.

Transcending boundaries: Unleashing the potential of multi-organ point-of-care ultrasound in acute kidney injury

Acute kidney injury (AKI) is a clinical syndrome characterized by a rapid increase in serum creatinine levels or a decrease in urine output or both. In spite of thorough history-taking, physical examination, and laboratory analysis, there are limitations in the diagnostic process and clinical monitoring of AKI. Point-of-care ultrasonography (POCUS), a limited ultrasound study performed by clinicians at the bedside, has emerged as a valuable tool in different clinical settings. In this discussion, we explore the potential of POCUS performed by nephrologists to address specific questions encountered in the diagnosis and management of AKI patients. POCUS not only aids in excluding hydronephrosis but also provides real-time insights into hemodynamics, enabling formulation of individualized treatment plans. Further studies are required to assess the impact of multi-organ POCUS on pragmatic patient outcomes related to AKI, as well as its potential in risk stratification and identification of different levels of AKI severity and pathophysiological signatures.

Norepinephrine alleviates cyclosporin A-induced nephrotoxicity by enhancing the expression of SFRP1

Norepinephrine (NE) has a certain effect on the improvement of renal function. However, whether NE can alleviate cyclosporin A (CsA)-induced nephrotoxicity needs further study. The effect of CsA (1.25, 2.5, 5, and 10 μM) on the human renal epithelial cell vitality, lactate dehydrogenase (LDH) activity, apoptosis, and secreted frizzled-related protein 1 (SFRP1) level was examined by cell counting kit-8, enzyme-linked immunosorbent assay, flow cytometer, and western blot. The effect of NE on the LDH activity, apoptosis, and SFRP1 level of human renal epithelial cells induced by CsA was examined again. After silencing of SFRP1 in human renal epithelial cells, the SFRP1 level, cell vitality, and apoptosis were examined again. CsA (1.25, 2.5, 5, and 10 μM) attenuated the cell vitality and SFRP1 level but enhanced the LDH activity and apoptosis in human renal epithelial cells, while the above effects were reversed by NE. Moreover, SFRP1 silencing reversed the regulation of NE on the SFRP1 level, cell vitality, and apoptosis in human renal epithelial cells induced by CsA. In conclusion, NE relieved CsA-induced nephrotoxicity via enhancing the expression of SFRP1.

Influence of arterial blood gases on the renal arterial resistive index in intensive care unit

BACKGROUND

Renal artery Doppler sonography with resistive index (RI) determination is a noninvasive, fast, and reliable diagnostic tool increasingly used in the intensive care unit (ICU) to predict and assess the reversibility of acute kidney injury (AKI). However, interpreting the RI can be challenging due to numerous influencing factors. While some studies have explored various confounding factors, arterial blood gases have received limited attention. Therefore, our study aims to evaluate the impact of arterial blood gases on the RI in the ICU setting.

METHODS

This prospective observational study enrolled ICU patients who required blood gas analysis and had not experienced significant hemodynamic changes recently. The RI was measured using standardized Doppler ultrasound within an hour of the arterial blood gases sampling and analysis.

RESULTS

A total of sixty-four patients were included in the analysis. Univariate analysis revealed a correlation between the RI and several variables, including PaCO2 (R = 0.270, p = 0.03), age (R = 0.574, p < 0.0001), diastolic arterial pressure (DAP) (R = - 0.368, p = 0.0028), and SaO2 (R = - 0.284, p = 0.0231). Multivariate analysis confirmed that age > 58 years and PaCO2 were significant factors influencing the RI, with respective odds ratios of 18.67 (p = 0.0003) and 1.132 (p = 0.0267).

CONCLUSION

The interpretation of renal arterial RI should take into account thresholds for PaCO2, age, and diastolic arterial pressure. Further studies are needed to develop a comprehensive scoring system that incorporates all these cofactors for a reliable analysis of RI levels. Trial registration This observational study, registered under number 70-0914, received approval from local Ethical Committee of Toulouse University Hospital.

Renal arterial resistive index, monocyte chemotactic protein 1 and neutrophil gelatinase-associated lipocalin, for predicting acute kidney injury in critically ill cancer patients

PURPOSE

We evaluated the renal arterial resistive index (RRI), urine monocyte chemotactic protein 1 (uMCP-1), and urine neutrophil gelatinase-associated lipocalin (uNGAL) to predict acute kidney injury (AKI) in critically ill cancer patients.

METHODS

In this prospective study, we included patients without AKI. We compared the area under the curve (AUC) of RRI, uMCP-1, and uNGAL to predict any stage of AKI and stage-3 AKI with the DeLong method, and we established cutoff points with the Youden index.

RESULTS

We included 64 patients, and 43 (67.2%) developed AKI. The AUC to predict AKI were: 0.714 (95% CI 0.587-0.820) for the RRI, 0.656 (95% CI 0.526-0.770) for uMCP-1, and 0.677 (95% CI 0.549-0.789) for uNGAL. The AUC to predict stage-3 AKI were: 0.740 (95% CI 0.615-0.842) for the RRI, 0.757 (95% CI 0.633-0.855) for uMCP-1, and 0.817 (95% CI 0.701-0.903) for uNGAL, without statistical differences among them. For stage 3 AKI prediction, the sensitivity and specificity were: 56.3% and 87.5% for a RRI > 0.705; 70% and 79.2% for an uMCP-1 > 2169 ng/mL; and 87.5% and 70.8% for a uNGAL > 200 ng/mL. The RRI was significantly correlated to age (r = 0.280), estimated glomerular filtration rate (r = - 0.259), mean arterial pressure (r = - 0.357), and serum lactate (r = 0.276).

CONCLUSION

The RRI, uMCP-1, and uNGAL have a similar ability to predict AKI. The RRI is more specific, while urine biomarkers are more sensitive to predict stage 3 AKI. The RRI correlates with hemodynamic variables. The novel uMCP-1 could be a useful biomarker that needs to be extensively studied.

A plea for personalization of the hemodynamic management of septic shock

Although guidelines provide excellent expert guidance for managing patients with septic shock, they leave room for personalization according to patients' condition. Hemodynamic monitoring depends on the evolution phase: salvage, optimization, stabilization, and de-escalation. Initially during the salvage phase, monitoring to identify shock etiology and severity should include arterial pressure and lactate measurements together with clinical examination, particularly skin mottling and capillary refill time. Low diastolic blood pressure may trigger vasopressor initiation. At this stage, echocardiography may be useful to identify significant cardiac dysfunction. During the optimization phase, echocardiographic monitoring should be pursued and completed by the assessment of tissue perfusion through central or mixed-venous oxygen saturation, lactate, and carbon dioxide veno-arterial gradient. Transpulmonary thermodilution and the pulmonary artery catheter should be considered in the most severe patients. Fluid therapy also depends on shock phases. While administered liberally during the resuscitation phase, fluid responsiveness should be assessed during the optimization phase. During stabilization, fluid infusion should be minimized. In the de-escalation phase, safe fluid withdrawal could be achieved by ensuring tissue perfusion is preserved. Norepinephrine is recommended as first-line vasopressor therapy, while vasopressin may be preferred in some patients. Essential questions remain regarding optimal vasopressor selection, combination therapy, and the most effective and safest escalation. Serum renin and the angiotensin I/II ratio may identify patients who benefit most from angiotensin II. The optimal therapeutic strategy for shock requiring high-dose vasopressors is scant. In all cases, vasopressor therapy should be individualized, based on clinical evaluation and blood flow measurements to avoid excessive vasoconstriction. Inotropes should be considered in patients with decreased cardiac contractility associated with impaired tissue perfusion. Based on pharmacologic properties, we suggest as the first test a limited dose of dobutamine, to add enoximone or milrinone in the second line and substitute or add levosimendan if inefficient. Regarding adjunctive therapies, while hydrocortisone is nowadays advised in patients receiving high doses of vasopressors, patients responding to corticosteroids may be identified in the future by the analysis of selected cytokines or specific transcriptomic endotypes. To conclude, although some general rules apply for shock management, a personalized approach should be considered for hemodynamic monitoring and support.

Effects of changes in position, positive end-expiratory pressure and mean arterial pressure on renal, portal and hepatic Doppler ultrasound perfusion indices: a randomized crossover study in cardiac surgery patients

Point-of-care ultrasound perfusion indices can be used for detection of AKI and venous congestion. Patients in the postoperative- and intensive care units are frequently exposed to alternating treatment and loading conditions. We aimed to study the effects of changes in preload (patient positioning), positive end-expiratory pressure (PEEP) and afterload (phenylephrine) on renal, portal and hepatic ultrasound indices. We hypothesized that renal resistive index was not influenced by changes in PEEP and patient positioning. This was a single-site, randomized, crossover study. Patients above 18 years scheduled for elective open-heart surgery at Aarhus University Hospital, Denmark, were available for inclusion. Patients were randomized to a sequence of six combinations of PEEP and position in addition to an increase in mean arterial pressure by phenylephrine. Thirty-one patients participated in the study. Resistive index was influenced by positional change (P = 0.007), but not by change in PEEP (P = 0.50) (Table 1). Renal venous stasis index and portal pulsatility fraction increased in the raised legs position (P ≤ 0.019), but not with increases in PEEP. Renal venous flow pattern and hepatic venous flow pattern were affected by position (P ≤ 0.019), but not by PEEP. None of the ultrasound indices were significantly changed by infusion of phenylephrine. Doppler perfusion indices were significantly affected by changes in preload, but not by changes in PEEP or afterload. Although the changes in the Doppler ultrasound indices were significant, they were small in absolute numbers. Therefore, from a clinical perspective, the ultrasound indices were robust.Trial registration Registered at clinicaltrials.com, first posted online June 5th 2020, identifier: NCT04419662.

Doppler ultrasound in the assessment of renal perfusion before and during continuous kidney replacement therapy in the pediatric intensive care unit

BACKGROUND

This study aimed to assess observer variability and describe renal resistive index (RRI) and pulsatility index (PI) before and after onset of continuous kidney replacement therapy (CKRT). A secondary objective was to correlate Doppler ultrasound findings with those from direct measurement of renal blood flow (RBF).

METHODS

This is a prospective observational study in hemodynamically stable Maryland piglets with and without acute kidney injury (AKI) and in hemodynamically unstable critically ill children requiring CKRT. Doppler-based RRI and PI were assessed for each subject. Measurements were made by two different operators (pediatric intensivists) before and after CKRT onset.

RESULTS

Observer variability assessment in the measurement of RRI and PI rendered a moderate correlation for both RRI (ICC 0.65, IQR 0.51-0.76) and PI (ICC 0.63, IQR 0.47-0.75). RRI and PI showed no correlation with RBF or urine output. Baseline RRI and PI were normal in control piglets [RRI 0.68 (SD 0.02), PI 1.25 (SD 0.09)] and those with AKI [RRI 0.68 (SD 0.03), PI 1.20 (SD 0.13)]. Baseline RRI and PI were elevated in critically ill children (RRI 0.85, PI 2.0). PI and RRI did not change with CKRT in any study group.

CONCLUSIONS

Observer variability between inexperienced pediatric intensivists was comparable with that between senior and junior operators. Doppler-based calculations did not correlate with invasive measurements of RBF. RRI and PI were normal in hemodynamically stable piglets with and without AKI. RRI and PI were high in hemodynamically unstable patients requiring CKRT. RRI and PI did not change after CKRT onset, despite changes in hemodynamic status. A higher resolution version of the Graphical abstract is available as Supplementary information.

Intrarenal Doppler approaches in hemodynamics: A major application in critical care

The treatment of severe cases usually requires multimodality hemodynamic monitoring approaches, particularly for tissue and organ perfusion tracking. Currently, only a few studies have investigated renal perfusion status at the bedside. Ultrasound has become increasingly utilized to guide the hemodynamic management of severe patients. Similarly, intrarenal Doppler (IRD) is widely used to assess renal perfusion from both the intrarenal artery and vein perspectives. The renal resistive index (RRI), which reflects the renal arterial blood flow profile, is often applied to predict the reversibility of renal dysfunction and to titrate hemodynamic support. Intrarenal venous flow (IRVF) patterns and the renal venous stasis index (RVSI), which reflects the intrarenal vein blood flow profile, are now being used to assess intravenous congestion. They may also be useful in predicting the risk of acute kidney injury and avoiding fluid overload. IRD can provide diverse and supplemental information on renal perfusion and may help to establish the early diagnosis in severe patients. This review focused on the specific operational methods, influencing factors, and applications of IRD in hemodynamics.

Intraoperative evaluation of renal resistive index with transesophageal echocardiography for the assessment of acute renal injury in patients undergoing coronary artery bypass grafting surgery: A prospective observational study

Background

Acute kidney injury (AKI) is a common complication after on pump coronary artery bypass grafting (CABG) surgery and is associated with a poor prognosis. Postoperative AKI is associated with morbidity, mortality, and increase in length of intensive care unit (ICU) stay and increases the financial burden. Identifying individuals at risk for developing AKI in postoperative period is extremely important to optimize outcomes. The aim of the study is to evaluate the association between the intraoperative transesophageal echocardiography (TEE) derived renal resistive index (RRI) and AKI in patients undergoing on-pump CABG surgery.

Methods

This prospective observational study was conducted in patients more than 18 years of age undergoing elective on pump CABG surgery between July 1, 2018, and December 31, 2019, at a tertiary care center. All preoperative, intraoperative, and postoperative parameters were recorded. TEE measurement was performed in hemodynamically stable patients before the sternum was opened. Postoperative AKI was diagnosed based on the serial measurement of serum creatinine and the monitoring of urine output.

Results

A total of 115 patients were included in our study. Thirty-nine (33.91%) patients had RRI >0.7 while remaining seventy-six (66.08%) patients had RRI <0.7. AKI was diagnosed in 26% (30/115) patients. AKI rates were significantly higher in patients with RRI values exceeding 0.7 with 46.15% (18/39) compared to 15.75% (12/76) in RRI values of less than 0.7. Multivariate analysis revealed that AKI was associated with an increase in RRI and diabetes mellitus. The RRI assessed by receiver operating characteristic (ROC) curve and the area under the curve (AUC) to distinguish between non-AKI and AKI groups were 0.705 (95% CI: 0.588-0.826) for preoperative RRI. The most accurate cut-off value to distinguish non-AKI and AKI groups was a preoperative RRI of 0.68 with a sensitivity of 70% and specificity of 67%.

Conclusions

An increased intraoperative RRI is an independent predictor of AKI in the postoperative period in patients undergoing CABG surgery. The cutoff value of TEE-derived RRI in the intraoperative period should be >0.68 to predict AKI in the postoperative period.

Meeting report: 3rd workshop of the peptide ADME discussion group

Challenges and opportunities within peptide ADME (absorption, distribution, metabolism and elimination) were presented and discussed at the 3rd online workshop of the Peptide ADME Discussion Group (3rd of February 2021). This article summarises the presentations and discussions from this workshop.The following topics were covered:Peptide drug-drug interactionsImpact of septic shock on PK and PD of the peptide selepressinMS processing software for metabolite identification of peptidesProfiling of peptides in preclinical drug developmentStrategy for immunogenicity testing of peptidesIn vitro stability testing of peptides for inhalation and automated LC-MS.

Effects of Mean Artery Pressure and Blood pH on Survival Rate of Patients with Acute Kidney Injury Combined with Acute Hypoxic Respiratory Failure: A Retrospective Study

Background and Objectives: In the intensive care unit (ICU), renal failure and respiratory failure are two of the most common organ failures in patients with systemic inflammatory response syndrome (SIRS). These clinical symptoms usually result from sepsis, trauma, hypermetabolism or shock. If this syndrome is caused by septic shock, the Surviving Sepsis Campaign Bundle suggests that vasopressin be given to maintain mean arterial pressure (MAP) > 65 mmHg if the patient is hypotensive after fluid resuscitation. Nevertheless, it is important to note that some studies found an effect of various mean arterial pressures on organ function; for example, a MAP of less than 75 mmHg was associated with the risk of acute kidney injury (AKI). However, no published study has evaluated the risk factors of mortality in the subgroup of acute kidney injury with respiratory failure, and little is known of the impact of general risk factors that may increase the mortality rate. Materials and Methods: The objective of this study was to determine the risk factors that might directly affect survival in critically ill patients with multiple organ failure in this subgroup. We retrospectively constructed a cohort study of patients who were admitted to the ICUs, including medical, surgical, and neurological, over 24 months (2015.1 to 2016.12) at Chiayi Chang Gung Memorial Hospital. We only considered patients who met the criteria of acute renal injury according to the Acute Kidney Injury Network (AKIN) and were undergoing mechanical ventilator support due to acute respiratory failure at admission. Results: Data showed that the overall ICU and hospital mortality rate was 63.5%. The most common cause of ICU admission in this cohort study was cardiovascular disease (31.7%) followed by respiratory disease (28.6%). Most patients (73%) suffered sepsis during their ICU admission and the mean length of hospital stay was 24.32 ± 25.73 days. In general, the factors independently associated with in-hospital mortality were lactate > 51.8 mg/dL, MAP ≤ 77.16 mmHg, and pH ≤ 7.22. The risk of in-patient mortality was analyzed using a multivariable Cox regression survival model. Adjusting for other covariates, MAP ≤ 77.16 mmHg was associated with higher probability of in-hospital death [OR = 3.06 (1.374–6.853), p = 0.006]. The other independent outcome predictor of mortality was pH ≤ 7.22 [OR = 2.40 (1.122–5.147), p = 0.024]. Kaplan-Meier survival curves were calculated and the log rank statistic was highly significant. Conclusions: Acute kidney injury combined with respiratory failure is associated with high mortality. High mean arterial pressure and normal blood pH might improve these outcomes. Therefore, the acid–base status and MAP should be considered when attempting to predict outcome. Moreover, the blood pressure targets for acute kidney injury in critical care should not be similar to those recommended for the general population and might prevent mortality.

High mean arterial pressure target to improve sepsis-associated acute kidney injury in patients with prior hypertension: a feasibility study

BACKGROUND

The optimal mean arterial pressure (MAP) in cases of septic shock is still a matter of debate in patients with prior hypertension. An MAP between 75 and 85 mmHg can improve glomerular filtration rate (GFR) but its effect on tubular function is unknown. We assessed the effects of high MAP level on glomerular and tubular renal function in two intensive care units of a teaching hospital. Inclusion criteria were patients with a history of chronic hypertension and developing AKI in the first 24 h of septic shock. Data were collected during two 6 h periods of MAP regimen administered consecutively after haemodynamic stabilisation in an order depending on the patient's admission unit: a high-target period (80-85 mmHg) and a low-target period (65-70 mmHg). The primary endpoint was the creatinine clearance (CrCl) calculated from urine and serum samples at the end of each MAP period by the UV/P formula.

RESULTS

26 patients were included. Higher urine output (+0.2 (95%:0, 0.4) mL/kg/h; P = 0.04), urine sodium (+6 (95% CI 0.2, 13) mmol/L; P = 0.04) and lower serum creatinine (- 10 (95% CI - 17, - 3) µmol/L; P = 0.03) were observed during the high-MAP period as compared to the low-MAP period, resulting in a higher CrCl (+25 (95% CI 11, 39) mL/mn; P = 0.002). The urine creatinine, urine-plasma creatinine ratio, urine osmolality, fractional excretion of sodium and urea showed no significant variation. The KDIGO stage at inclusion only interacted with serum creatinine variation and low level of sodium excretion at inclusion did not interact with these results.

CONCLUSIONS

In the early stage of sepsis-associated AKI, a high-MAP target in patients with a history of hypertension was associated with a higher CrCl, but did not affect the kidneys' ability to concentrate urine, which may reflect no effect on tubular function.

Risk factors for acute kidney injury in critically ill patients with torso injury: A retrospective observational single-center study

Acute kidney injury (AKI) is common in trauma patients and associated with poor outcomes. Identifying AKI risk factors in trauma patients is important for risk stratification and provision of optimal intensive care unit (ICU) treatment. This study identified AKI risk factors in patients admitted to critical care after sustaining torso injuries.We performed a retrospective chart review involving 380 patients who sustained torso injuries from January 2016 to December 2019. Patients were included if they were aged >15 years, admitted to an ICU, survived for >48 hours, and had thoracic and/or abdominal injuries and no end-stage renal disease. AKI was defined according to the Kidney Disease Improving Global Outcomes definition and staging system. Clinical and laboratory variables were compared between the AKI and non-AKI groups (n = 72 and 308, respectively). AKI risk factors were assessed using multivariate logistic regression analysis.AKI occurred in 72 (18.9%) patients and was associated with higher mortality than non-AKI patients (26% vs 4%, P < .001). Multivariate logistic regression analysis identified bowel injury, cumulative fluid balance >2.5 L for 24 hours, lactate levels, and vasopressor use (adjusted odds ratio: 2.953, 2.058, 1.170, and 2.910; 95% confidence interval: 1.410-6.181, 1.017-4.164, 1.019-1.343, and 1.414-5.987; P = .004, .045, .026, and .004, respectively) as independent risk factors for AKI.AKI in patients admitted to the ICU with torso injury had a substantial mortality. Recognizing risk factors at an early stage could aid risk stratification and provision of optimal ICU care.

Renal Resistive Index: Not Only for Kidney Clinics

Renal Resistive Index (RRI) is a measurement of the resistance of the renal blood flow. A value higher than 0.70 is a marker of increased resistance and is correlated with kidney injury and its severity. Additionally, it may be associated with the mortality rate in the post-surgery population. In COVID-19 subjects, we found that high RRI has been associated with high levels of serum C-reactive protein, a marker of systemic inflammatory reaction syndrome. Finally, we propose RRI not only as a marker of kidney injury, but also as a tool to evaluate the course of critical illness.

New strategies to optimize renal haemodynamics

PURPOSE OF REVIEW

This review discusses the macrocirculatory and microcirculatory aspects of renal perfusion, as well as novel methods by which to measure renal blood flow. Finally, therapeutic options are briefly discussed, including renal-specific microcirculatory effects.

RECENT FINDINGS

The optimal mean arterial pressure (MAP) needed for preservation of renal function has been debated but is most likely a MAP of 60-80 mmHg. In addition, attention should be paid to renal outflow pressure, typically central venous pressure. Heterogeneity in microcirculation can exist and may be mitigated through appropriate use of vasopressors with unique microcirculatory effects. Excessive catecholamines have been shown to be harmful and should be avoided. Both angiotensin II and vasopressin may improve glomerular flow through a number of mechanisms. Macrocirculatory and microcirculatory blood flow can be measured through a number of bedside ultrasound modalities, sublingual microscopy and urinary oxygen measurement, SUMMARY: Acute kidney injury (AKI) is a common manifestation of organ failure in shock, and avoidance of hemodynamic instability can mitigate this risk. Measurement of renal haemodynamics is not routinely performed but may help to guide therapeutic goals. A thorough understanding of pathophysiology, measurement techniques and therapeutic options may allow for a personalized approach to blood pressure management in patients with septic shock and may ultimately mitigate AKI.

Modeling the Steady-State Effects of Mean Arterial Pressure on the Kidneys

Goal: We describe the relationship between mean arterial pressure (MAP) and glomerular filtration rate (GFR) since therapies affecting MAP can have large effects on kidney function. Methods: We developed a closed-loop, steady-state mechanistic model of the human kidney with a reduced parameter set estimated from measurements. Results: The model was first validated against literature models. Further, GFR was validated against intensive care patient data (root mean squared error (RMSE) 13.5 mL/min) and against hypertensive patients receiving sodium nitroprusside (SNP) (RMSE less than 5 mL/min). A sensitivity analysis of the model reinforced the fact that vascular resistance is inversely related to GFR and showed that changes to either vascular resistance or renal autoregulation cause a significant change in sodium concentration in the descending limb of Henle. Conclusions: This model can be used to determine the impact of MAP on GFR and overall kidney health. The modeling framework lends itself to personalization of the model to a specific human.

Renal Resistive Index: Response to Shock and its Determinants in Critically Ill Patients

Introduction:

Shock is characterized by micro- and macrovascular flow impairment contributing to acute kidney injury (AKI). Routine monitoring of the circulation regards the macrocirculation but not the renal circulation which can be assessed with Doppler ultrasound as renal resistive index (RRI). RRI reflects resistance to flow. High RRI predicts persistent AKI. Study aims were to determine whether RRI is elevated in shock and to identify determinants of RRI.

Materials and Methods:

This prospective observational cohort study included two cohorts of patients, with and without shock less than 24-h after intensive care admission. Apart from routine monitoring, three study measurements were performed simultaneously: RRI, sublingual microcirculation, and bioelectral impedance analysis.

Results:

A total of 92 patients were included (40 shock, 52 nonshock), median age was 69 [60–76] vs. 67 [59–76], P = 0.541; APACHE III was 87 [65–119] vs. 57 [45–69], P < 0.001. Shock patients had higher RRI than patients without shock (0.751 [0.692–0.788] vs. 0.654 [0.610–0.686], P < 0.001). Overall, high age, APACHE III score, lactate, vasopressor support, pulse pressure index (PPI), central venous pressure (CVP), fluid balance, and low preadmission estimated glomerular filtration rate, mean arterial pressure (MAP), creatinine clearance, and reactance/m were associated with high RRI at univariable regression (P < 0.01). Microcirculatory markers were not. At multivariable regression, vasopressor support, CVP, PPI and MAP, reactance/m, and preadmission eGFR were independent determinants of RRI (n = 92, adj. R² = 0.587).

Conclusions:

Patients with shock have a higher RRI than patients without shock. Independent determinants of high RRI were pressure indices of the systemic circulation, low membrane capacitance, and preadmission renal dysfunction. Markers of the sublingual microcirculation were not.

Renal resistive index as a predictor of postoperative complications in liver resection surgery. Observational study

Mortality after liver surgery reduced during the last three decades to less than 2%, but post-operative morbidity occurs in 20-50% of cases. Patients are often considered eligible for post-operative intensive-care unit (ICU) admission. Predicting which patients that are at higher risk could lead to a more precise perioperative management. We investigated whether renal resistive index (RRI), alone or along with other items, can predict post-operative complication after hepatic resection. All consecutive patients undergoing hepatectomy for primary or metastatic neoplasm at our Institution between February 2015 and March 2017 were enrolled. They received RRI measurement before entering in operative room and after awakening from general anesthesia. 183 Patients were enrolled. High surgical invasiveness, surgery time > 360 min, pre-operative RRI and postoperative serum lactate clearance <  - 6%, showed to be associated with postoperative complications. Pre-operative RRI, complex liver resection, long-lasting surgery and poor lactate clearance (cLac) close to awakening from general anesthesia, all together may permit to classify the risk of post-operative adverse outcome after hepatic resection surgery.

Early Recognition of Persistent Acute Kidney Injury

Despite the vast amount of literature dedicated to acute kidney injury (AKI) and its clinical consequences, short-term renal recovery has been relatively neglected. Recent studies have suggested that timing of renal recovery is associated with longer-term risk of death, residual renal function, and end-stage renal failure risk. In addition, longer AKI duration is associated with an increased requirement for renal replacement therapy. Comorbidities, especially renal and cardiovascular, severity of AKI, criteria to reach AKI diagnosis, as well as severity of critical illness have been associated with longer AKI duration, and, more specifically, risk of persistent renal dysfunction. Because predicting short-term renal recovery is clinically relevant, several tests, imaging, and biomarkers have been tested in a way to predict the course of AKI and chances for early renal recovery. In this review, the definition of recovery, consequences of persistent AKI, and tools proposed to predict recovery are described. The performance of these tools and their limits are discussed.

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.

Regional perfusion monitoring in shock

PURPOSE OF REVIEW

Despite restoration of adequate systemic blood flow in patients with shock, single organs may remain hypoperfused. In this review, we summarize the results of a literature research on methods to monitor single organ perfusion in shock. We focused on methods to measure heart, brain, kidney, and/or visceral organ perfusion. Furthermore, only methods that can be used in real-time and at the bedside were included.

RECENT FINDINGS

We identified studies on physical examination techniques, electrocardiography, echocardiography, contrast-enhanced ultrasound, near-infrared spectroscopy, and Doppler sonography to assess single organ perfusion.

SUMMARY

Physical examination techniques have a reasonable negative predictive value to exclude single organ hypoperfusion but are nonspecific to detect it. Technical methods to indirectly measure myocardial perfusion include ECG and echocardiography. Contrast-enhanced ultrasound can quantify myocardial perfusion but has so far only been used to detect regional myocardial hypoperfusion. Near-infrared spectroscopy and transcranial Doppler sonography can be used to assess cerebral perfusion and determine autoregulation thresholds of the brain. Both Doppler and contrast-enhanced ultrasound techniques are novel methods to evaluate renal and visceral organ perfusion. A key limitation of most techniques is the inability to determine adequacy of organ blood flow to meet the organs' metabolic demands.

Effect of Increasing Blood Pressure With Noradrenaline on the Microcirculation of Patients With Septic Shock and Previous Arterial Hypertension

OBJECTIVES

To assess whether an increase in mean arterial pressure in patients with septic shock and previous systemic arterial hypertension changes microcirculatory and systemic hemodynamic variables compared with patients without arterial hypertension (control).

DESIGN

Prospective, nonblinded, interventional study.

SETTING

Three ICUs in two teaching hospitals.

PATIENTS

After informed consent, we included patients older than 18 years with septic shock for at least 6 hours, sedated, and under mechanical ventilation. We paired patients with and without arterial hypertension by age.

INTERVENTIONS

After obtaining systemic and microcirculation baseline hemodynamic variables (time 0), we increased noradrenaline dose to elevate mean arterial pressure up to 85-90 mm Hg before collecting a new set of measurements (time 1).

MEASUREMENTS AND MAIN RESULTS

We included 40 patients (20 in each group). There was no significant difference in age between the groups. After the rise in mean arterial pressure, there was a significant increase in cardiac index and a slight but significant reduction in lactate in both groups. We observed a significant improvement in the proportion of perfused vessels (control: 57.2 ± 14% to 66 ± 14.8%; arterial hypertension: 61.4 ± 12.3% to 70.8 ± 7.1%; groups: p = 0.29; T0 and T1: p < 0.001; group and time interaction: p = 0.85); perfused vessels density (control: 15.6 ± 4 mm/mm to 18.6 ± 4.5 mm/mm; arterial hypertension: 16.4 ± 3.5 mm/mm to 19.1 ± 3 mm/mm; groups: p = 0.51; T0 and T1: p < 0.001; group and time interaction: p = 0.70), and microcirculatory flow index (control: 2.1 ± 0.6 to 2.4 ± 0.6; arterial hypertension: 2.1 ± 0.5 to 2.6 ± 0.2; groups: p = 0.71; T0 and T1: p = 0.002; group and time interaction: p = 0.45) in both groups.

CONCLUSIONS

Increasing mean arterial pressure with noradrenaline in septic shock patients improves density and flow in small vessels of sublingual microcirculation. However, this improvement occurs both in patients with previous arterial hypertension and in those without arterial hypertension.

[Diagnosing acute organ ischemia : A practical guide for the emergency and intensive care physician]

Ischemia refers to a reduction or interruption of the blood flow to one or more organs. Early recognition of shock, a global ischemic state of the body, is of key importance in emergency and intensive care medicine. The physical examination and point-of-care laboratory diagnostics (i.e. lactate, base deficit, central/mixed venous oxygen saturation, venous-arterial carbon dioxide partial tension) are the methods of choice to diagnose shock in clinical practice. Importantly, a state of shock can also be present in patients with normo- or hypertensive arterial blood pressures. In shock, hypoperfusion of vital and visceral organs occurs. In the second part of this article, physical examination techniques, laboratory and diagnostic methods to detect shock-related hypoperfusion of the brain, heart, kidney and gastrointestinal tract are reviewed.

Value of early diagnosis of sepsis complicated with acute kidney injury by renal contrast-enhanced ultrasound

BACKGROUND

The incidence of acute kidney injury (AKI) in patients with sepsis is high, and the prognosis of patients with septic AKI is poor. The early diagnosis and treatment of septic AKI is of great significance in improving the prognosis of patients with sepsis.

AIM

To explore the value of contrast-enhanced ultrasound (CEUS), serum creatinine (Scr), and other indicators in the early diagnosis of septic AKI.

METHODS

Ninety patients with sepsis during hospitalization at Tongji Hospital of Tongji University were recruited as subjects. Each patient was recorded with relevant basic data, clinical indicators, and CEUS results. The patients were divided into AKI group and non-AKI group according to the results of renal function diagnosis after 48 h. On the 7th day, the renal function of the non-AKI group was re-evaluated and the patients were further divided into AKI subgroup and non-AKI subgroup. The differences of the indicators in different groups were compared, and the diagnostic value of each indicator and their combination for septic AKI was analyzed.

RESULTS

Systemic inflammatory response score (2.58 ± 0.75), blood lactic acid (3.01 ± 1.33 mmol/L), Scr (141.82 ± 27.19 μmol/L), blood urea nitrogen (4.41 ± 0.81mmol/L), and rise time (10.23 ± 2.63 s) in the AKI group were higher than those in the non-AKI group. Peak intensity (PI) (10.78 ± 3.98 dB) and wash in slope (WIS) (1.07 ± 0.53 dB/s) were lower than those in the non-AKI group. The differences were statistically significant (P < 0.05). The PI (12.83 ± 3.77 dB) and WIS (1.22 ± 0.68 dB/s) in the AKI subgroup were lower than those in the non-AKI subgroup, and the differences were statistically significant (P < 0.05). The area under curve (AUC) of Scr for the diagnosis of septic AKI was 0.825 with a sensitivity of 56.76% and a specificity of 100%. The AUCs of WIS and PI (0.928 and 0.912) were higher than those of Scr. Their sensitivities were 100%, but the specificities were 71.70% and 75.47%. The AUC of the combination of three indicators for the diagnosis of septic AKI was 0.943, which was significantly higher than the AUC diagnosed by each single indicator. The sensitivity was 94.59%, and the specificity was 81.13%.

CONCLUSION

The combination of Scr, PI, and WIS can improve the diagnostic accuracy of septic AKI. PI and WIS are expected to predict the occurrence of early septic AKI.

Renal resistive index: a new reversible tool for the early diagnosis and evaluation of organ perfusion in critically ill patients: a case report

BACKGROUND

We reported a case of early detection of peripheral hypoperfusion trough the evaluation of a new index in intensive care: Renal Doppler Resistive Index (RRI).

CASE PRESENTATION

We admitted a 76-year-old man who underwent ileostomy and hernioplasty because of an intestinal occlusion due to obstructive strangulated right inguinal hernia. The post-operative period was characterised by hemodynamic instability and he needed an invasive hemodynamic monitoring, administration of vasopressors and continuous renal replacement therapy (CRRT). Then, hemodynamic stability was obtained and vasopressors interrupted. RRI was lower than 0.7. In the eleventh post-operative day, despite stable macrocirculatory parameters, we found increased values of RRI. An abdomen ultrasound first and then a CT scan revealed the presence of bleeding from the previous ileostomy. Hence, the patient immediately underwent another surgical operation.

CONCLUSIONS

RRI modification appears to be more precocious than any other hemodynamic, microcirculatory and metabolic parameter routinely used. RRI has been widely used to assess renal function in critically ill patients; now, we presume that RRI could represent a common and useful tool to manage target therapy in critical condition.

Minimizing catecholamines and optimizing perfusion

Catecholamines are used to increase cardiac output and blood pressure, aiming ultimately at restoring/improving tissue perfusion. While intuitive in its concept, this approach nevertheless implies to be effective that regional organ perfusion would increase in parallel to cardiac output or perfusion pressure and that the catecholamine does not have negative effects on the microcirculation. Inotropic agents may be considered in some conditions, but it requires prior optimization of cardiac preload. Alternative approaches would be either to minimize exposure to vasopressors, tolerating hypotension and trying to prioritize perfusion but this may be valid as long as perfusion of the organ is preserved, or to combine moderate doses of vasopressors to vasodilatory agents, especially if these are predominantly acting on the microcirculation. In this review, we will discuss the pros and cons of the use of catecholamines and alternative agents for improving tissue perfusion in septic shock.

Determinants of Doppler-based renal resistive index in patients with septic shock: impact of hemodynamic parameters, acute kidney injury and predisposing factors

BACKGROUND

Increased renal resistive index (RI) measured by Doppler ultrasonography has been shown to be associated with acute kidney injury (AKI) in septic patients. However, its clinical use is limited by poor sensitivity and specificity which may be explained by its numerous determinants [in particular mean arterial pressure (MAP)]. We measured, in patients with septic shock, RI at different MAP levels over a short period of time on the admission day to ICU (D1) and every 3 days until day 10 (D10) to define the determinants of RI and study specifically the relationship between RI and MAP.

RESULTS

Consecutive patients with septic shock without preexisting chronic renal dysfunction were included in this prospective cohort study in two ICUs. Sixty-five patients were included in the study. Thirty-three (50.8%) and 15 (23.1%) patients had a history of chronic hypertension or diabetes, respectively. At D3, 35 patients presented AKI with AKIN 2 or 3 criteria (severe AKI, AKIN2-3 group) and 30 presented no AKIN or AKIN 1 criteria (AKIN0-1 group). As previously described, RI at D1 was higher in the AKIN2-3 group than in the AKIN0-1 group (0.73 interquartile range [0.67; 0.78] vs. 0.67 [0.59; 0.72], p = 0.001). A linear mixed model for predicting RI from D1 to D10 showed that an increase in pulse pressure, presence of severe AKI and additional day of ICU hospitalization were associated with an increase in RI. An increase in MAP and recovery from severe AKI were associated with a decrease in RI. In the presence of chronic hypertension or diabetes, an increase in MAP resulted in a lower decrease in RI, than in the absence of such factors. Presence of AKI at D3 did not impact the relationship between MAP and RI.

CONCLUSIONS

Severe AKI was associated with a reversible increase in RI without significant interaction with the relationship between MAP and RI. Conversely, the presence of chronic hypertension and/or diabetes interacted with this relationship.

Factors associated with renal Doppler resistive index in critically ill patients: a prospective cohort study

Background

The renal Doppler resistive index (renal RI) is a noninvasive tool that has been used to assess renal perfusion in the intensive care unit (ICU) setting. However, many parameters have been described as influential on the values of renal RI. Therefore, we proposed this study to evaluate the variables that could impact renal RI in critically ill patients.

Methods

A prospective observational study was performed in a 14-bed medical–surgical adult ICU. All consecutive patients admitted to the ICU during the study period were evaluated for eligibility. Renal RI was performed daily until the third day after ICU admission, death, or renal replacement therapy (RRT) requirement. Clinical and blood test data were collected throughout this period. Acute kidney injury (AKI) reversibility was categorized as transient (normalization of renal function within 3 days of AKI onset) or persistent (non-resolution of AKI within 3 days of onset or need for RRT). A linear mixed model was applied to evaluate the factors that could influence renal RI.

Results

Eighty-three consecutive patients were included. Of these, 65% were male and 50.6% were medical admissions. Mean SAPS 3 was 47 ± 16. Renal RI was significantly different between no-AKI (0.64 ± 0.06), transient AKI (0.64 ± 0.07), and persistent AKI groups (0.70 ± 0.08, p < 0.01). Variables associated with renal RI variations were mean arterial pressure, lactate, age, and persistent AKI (p < 0.05). No association between serum chloride and renal RI was observed (p = 0.868).

Conclusions

Mean arterial pressure, lactate, age, and type of AKI might influence renal RI in critically ill patients.

Augmented renal clearance in critically ill trauma patients: A pathophysiologic approach using renal vascular index

BACKGROUND

The aim of the present study was to explore the relationship between creatinine clearance (ClCr), cardiac index (CI) and renal vascular index (RVI) in order to assess the potential mechanisms driving ARC in critically ill trauma patient. The secondary objective was to assess the performance of RVI for prediction of ARC.

METHODS

Every trauma patient who underwent cardiac and renal ultrasound measurements during their initial ICU management was retrospectively reviewed over a 3-month period. ARC was defined by a 24-hr measured ClCr ≥ 130 mL/min/1.73m². A mixed effect model was constructed to explore covariates associated with ClCr over time. The performance of RVI for prediction of ARC was assessed by receiver operating characteristic (ROC) curve and compared to the ARCTIC (ARC in trauma intensive care) predictive scoring model.

RESULTS

Thirty patients, contributing for 121 coupled physiologic data, were retrospectively analysed. There was a significant correlation between ClCr values and RVI (r = -0.495; P = 0.005) but not between ClCr and CI values (r = 0.023; P = 0.967) at day 1. Using a mixed effect model, only age remained associated with ClCr variations over time. The area under the ROC curve of RVI for predicting ARC was 0.742 (95% CI: 0.649-0.834; P < 0.0001), with statistical difference when compared to the ROC curve of ARCTIC [0.842 (0.771-0.913); P < 0.0001].

CONCLUSION

Ultrasonic evaluation of CI and RVI did not allow approaching the haemodynamic mechanisms responsible for ARC in patients. RVI was inaccurate and not better than clinical score for predicting ARC.

Renal intraparenchymal resistive index: the ultrasonographic answer to many clinical questions

The use of renal resistive indices (RRIs) for the study of renal microcirculation has in the past been proposed for the identification of renal organ damage or even to specifically identify injury to some areas of the renal parenchyma. Nevertheless, according to the most recent evidences from literature this organ-based conception of RRIs has been proven to be partial and unable to explain the RRIs variations in clinical settings of sepsis or combined organ failure of primitively extrarenal origin or, more generally, the deep connection between RRIs and hemodynamic factors such as compliance and pulsatility of the large vessels. The aim of this review is to explain the physiopathological basis of RRIs determination and the most common interpretative errors in their analysis. Moreover, through a comprehensive vision of these Doppler indices, the traditional and emerging clinical application fields for RRIs are discussed.

Impact of individualized target mean arterial pressure for septic shock resuscitation on the incidence of acute kidney injury: a retrospective cohort study

BACKGROUND

To examine the relationship between delta mean arterial pressure (ΔMAP; MAP change between pre-admission minus post-resuscitation) and acute kidney injury (AKI) among patients with septic shock. In this retrospective, single-center cohort study of adult patients pre-admission MAP is defined as the median MAP recorded from 365 to 7 days before admission. Post-resuscitation MAP was median MAP during the 7th hour after initiating resuscitation.

RESULTS

In our cohort (N = 233; 55% male), the median (interquartile range [IQR]) age was 71 (58-81) years and the median (IQR) acute physiology, age, chronic health evaluation (APACHE) III score was 81 (66-97). Although those in the lowest ΔMAP quartile (-24.5 to 3.9 mmHg) had no demographic differences compared with the rest of the cohort, the odds ratio for AKI was 0.26 (95% CI 0.11-0.57) after adjustment for other known AKI risk factors. Among patients with a history of hypertension, the lowest quartile had an odds ratio for AKI of 0.12 (95% CI 0.04-0.37) after adjusting for risk factors for AKI in this cohort.

CONCLUSIONS

The incidence of AKI was lowest among those whose post-resuscitation MAP was closest to or higher than their pre-admission MAP. Further study regarding the effect of targeting the pre-admission MAP for post-resuscitation on the incidence of AKI is warranted.

The Role of Point-of-Care Ultrasound Monitoring in Cardiac Surgical Patients With Acute Kidney Injury

The approach to the patient with acute kidney injury (AKI) after cardiac surgery involves multiple aspects. These include the rapid recognition of reversible causes, the accurate identification of patients who will progress to severe stages of AKI, and the subsequent management of complications resulting from severe renal dysfunction. Unfortunately, the inherent limitations of physical examination and laboratory parameter results are often responsible for suboptimal clinical management. In this review article, the authors explore how point-of-care ultrasound, including renal and extrarenal ultrasound, can be used to complement all aspects of the care of cardiac surgery patients with AKI, from the initial approach of early AKI to fluid balance management during renal replacement therapy. The current evidence is reviewed, including knowledge gaps and future areas of research.

Hemodynamic support in the early phase of septic shock: a review of challenges and unanswered questions

Background

Improving sepsis support is one of the three pillars of a 2017 resolution according to the World Health Organization (WHO). Septic shock is indeed a burden issue in the intensive care units. Hemodynamic stabilization is a cornerstone element in the bundle of supportive treatments recommended in the Surviving Sepsis Campaign (SSC) consecutive biannual reports.

Main body

The “Pandera’s box” of septic shock hemodynamics is an eternal debate, however, with permanent contentious issues. Fluid resuscitation is a prerequisite intervention for sepsis rescue, but selection, modalities, dosage as well as duration are subject to discussion while too much fluid is associated with worsen outcome, vasopressors often need to be early introduced in addition, and catecholamines have long been recommended first in the management of septic shock. However, not all patients respond positively and controversy surrounding the efficacy-to-safety profile of catecholamines has come out. Preservation of the macrocirculation through a “best” mean arterial pressure target is the actual priority but is still contentious. Microcirculation recruitment is a novel goal to be achieved but is claiming more knowledge and monitoring standardization. Protection of the cardio-renal axis, which is prevalently injured during septic shock, is also an unavoidable objective. Several promising alternative or additive drug supporting avenues are emerging, trending toward catecholamine’s sparing or even “decatecholaminization.” Topics to be specifically addressed in this review are: (1) mean arterial pressure targeting, (2) fluid resuscitation, and (3) hemodynamic drug support.

Conclusion

Improving assessment and means for rescuing hemodynamics in early septic shock is still a work in progress. Indeed, the bigger the unresolved questions, the lower the quality of evidence.

Doppler Renal Resistance Index for the Prediction of Response to Passive Leg-Raising Following Cardiac Surgery

PURPOSE

Doppler-based renal resistance index (RI) can be measured at the bedside of critically ill patients. This study was designed to assess if the RI predicted an increase in cardiac output (CO) following passive leg-raising (PLR) in patients admitted to the intensive care unit after cardiac surgery.

METHODS

During this single center prospective study, Doppler assessment of RI and measurements of CO using the thermodilution method were performed, after surgery, in the intensive care unit before and after PLR. A positive response to PLR was defined as a ≥10% increase in CO.

RESULTS

We included 30 patients. The mean RI was higher before (0.694 ±0.069) than after PLR (0.679 ± 0.069) (P = .02) with a median change of -0.012 (IQR: -0.042;0.000). Following PLR, 9 patients (30%) had a >10% increase in CO. In patients with a positive PLR response, the decrease in the RI during PLR was more pronounced than in patients who did not respond to PLR (PLR ± 0.042 (IQR: -0.051; -0.040) vs PLR ± -0.008 (IQR: -0.032; 0.015) (P = .004). There was a significant negative association between RI change in response to PLR and a 10% increase in CO following PLR (OR: 1.63 (CI:1.07-2.47) (P = .02) per -0.01 change).

CONCLUSION

An increase in CO following PLR was associated with a significant decrease in RI. Variations of RI in response to PLR should be further studied as a tool to predict fluid responsiveness. However, their clinical utility could be limited by the small magnitude of the variations.

Acute kidney injury is associated with a decrease in cortical renal perfusion during septic shock

Background

Renal perfusion status remains poorly studied at the bedside during septic shock. We sought to measure cortical renal perfusion in patients with septic shock during their first 3 days of care using renal contrast enhanced ultrasound (CEUS).

Methods

We prospectively included 20 ICU patients with septic shock and 10 control patients (CL) without septic shock admitted to a surgical ICU. Cortical renal perfusion was evaluated with CEUS during continuous infusion of Sonovue (Milan, Italy) within the first 24 h (day 0), between 24 and 48 h (day 1) and after 72 h (day 3) of care. Each measurement consisted of three destruction replenishment sequences that were recorded for delayed analysis with dedicated software (Vuebox). Renal perfusion was quantified by measuring the mean transit time (mTT) and the perfusion index (PI), which is the ratio of renal blood volume (rBV) to mTT.

Results

Cortical renal perfusion was decreased in septic shock as attested by a lower PI and a higher mTT in patients with septic shock than in patients of the CL group (p = 0.005 and p = 0.03). PI values had wider range in patients with septic shock (median (min-max) of 74 arbitrary units (a.u.) (3–736)) than in patients of the CL group 228 a.u. (67–440)). Renal perfusion improved over the first 3 days with a PI at day 3 higher than the PI at day 0 (74 (22–120) versus 160 (88–245) p = 0.02). mTT was significantly higher in patients with severe acute kidney injury (AKI) (n = 13) compared with patients with no AKI (n = 7) over time (p = 0.005). The PI was not different between patients with septic shock with severe AKI and those with no AKI (p = 0.29).

Conclusions

Although hemodynamic macrovascular parameters were restored, the cortical renal perfusion can be decreased, normal or even increased during septic shock. We observed an average decrease in cortical renal perfusion during septic shock compared to patients without septic shock. The decrease in cortical renal perfusion was associated with severe AKI occurrence. The use of renal CEUS to guide renal perfusion resuscitation needs further investigation.

Effect of fluid challenge on renal resistive index after major orthopaedic surgery: A prospective observational study using Doppler ultrasonography

BACKGROUND

A postoperative renal resistive index (RRI)>0.70 has the best threshold to early predict acute kidney injury (AKI). The response of RRI to a postoperative fluid challenge (FC) is unknown. The aim of our study was to assess the impact of a FC on RRI in suspected hypovolaemia patients after orthopaedic surgery.

DESIGN

In this single-centre observational study, we prospectively screened 156 patients in the recovery room after having undergone a hip or knee replacement.

INTERVENTIONS

Forty-six patients with a RRI>0.70 and requiring FC were included. RRI and cardiac output (CO) were measured before and immediately after a fluid challenge with 500mL of isotonic saline. A decrease in RRI>5% was considered significant (renal responders).

RESULTS

Overall, FC resulted in a consistent decrease in RRI (from 0.74 [0.72-0.79] to 0.70 [0.68-0.73], P<0.01). Thirty-four patients (74%) showed a significant decrease in their RRI (from 0.74 [0.73-0.79] to 0.69 [0.67-0.72], P<0.05, versus non-responders: from 0.73 [0.72-0.75] to 0.72 [0.71-0.79], P=NS). CO increased equally among renal responders and non-responders (P=0.56). No correlation was found between changes in RRI and CO (r²=0.04; P=0.064). AKI was more common in renal non-responders (7/12) than in responders (3/34, P=0.001).

CONCLUSIONS

After major orthopaedic surgery, a FC can decrease RRI in suspected hypovolaemia patients at risk of postoperative AKI, but the changes are not correlated to changes in CO. Decreases in RRI were associated with better renal outcome.

Renal autoregulation and blood pressure management in circulatory shock

The importance of personalized blood pressure management is well recognized. Because renal pressure–flow relationships may vary among patients, understanding how renal autoregulation may influence blood pressure control is essential. However, much remains uncertain regarding the determinants of renal autoregulation in circulatory shock, including the influence of comorbidities and the effects of vasopressor treatment. We review published studies on renal autoregulation relevant to the management of acutely ill patients with shock. We delineate the main signaling pathways of renal autoregulation, discuss how it can be assessed, and describe the renal autoregulatory alterations associated with chronic disease and with shock.

Development of a Physiologically Based Pharmacokinetic Modelling Approach to Predict the Pharmacokinetics of Vancomycin in Critically Ill Septic Patients

BACKGROUND AND OBJECTIVES

Sepsis is characterised by an excessive release of inflammatory mediators substantially affecting body composition and physiology, which can be further affected by intensive care management. Consequently, drug pharmacokinetics can be substantially altered. This study aimed to extend a whole-body physiologically based pharmacokinetic (PBPK) model for healthy adults based on disease-related physiological changes of critically ill septic patients and to evaluate the accuracy of this PBPK model using vancomycin as a clinically relevant drug.

METHODS

The literature was searched for relevant information on physiological changes in critically ill patients with sepsis, severe sepsis and septic shock. Consolidated information was incorporated into a validated PBPK vancomycin model for healthy adults. In addition, the model was further individualised based on patient data from a study including ten septic patients treated with intravenous vancomycin. Models were evaluated comparing predicted concentrations with observed patient concentration-time data.

RESULTS

The literature-based PBPK model correctly predicted pharmacokinetic changes and observed plasma concentrations especially for the distribution phase as a result of a consideration of interstitial water accumulation. Incorporation of disease-related changes improved the model prediction from 55 to 88% within a threshold of 30% variability of predicted vs. observed concentrations. In particular, the consideration of individualised creatinine clearance data, which were highly variable in this patient population, had an influence on model performance.

CONCLUSION

PBPK modelling incorporating literature data and individual patient data is able to correctly predict vancomycin pharmacokinetics in septic patients. This study therefore provides essential key parameters for further development of PBPK models and dose optimisation strategies in critically ill patients with sepsis.