Mean perfusion pressure deficit during the initial management of shock--an observational cohort study

Determinants of acute kidney injury during high-power mechanical ventilation: secondary analysis from experimental data

BACKGROUND

The individual components of mechanical ventilation may have distinct effects on kidney perfusion and on the risk of developing acute kidney injury; we aimed to explore ventilatory predictors of acute kidney failure and the hemodynamic changes consequent to experimental high-power mechanical ventilation.

METHODS

Secondary analysis of two animal studies focused on the outcomes of different mechanical power settings, including 78 pigs mechanically ventilated with high mechanical power for 48 h. The animals were categorized in four groups in accordance with the RIFLE criteria for acute kidney injury (AKI), using the end-experimental creatinine: (1) NO AKI: no increase in creatinine; (2) RIFLE 1-Risk: increase of creatinine of > 50%; (3) RIFLE 2-Injury: two-fold increase of creatinine; (4) RIFLE 3-Failure: three-fold increase of creatinine; RESULTS: The main ventilatory parameter associated with AKI was the positive end-expiratory pressure (PEEP) component of mechanical power. At 30 min from the initiation of high mechanical power ventilation, the heart rate and the pulmonary artery pressure progressively increased from group NO AKI to group RIFLE 3. At 48 h, the hemodynamic variables associated with AKI were the heart rate, cardiac output, mean perfusion pressure (the difference between mean arterial and central venous pressures) and central venous pressure. Linear regression and receiving operator characteristic analyses showed that PEEP-induced changes in mean perfusion pressure (mainly due to an increase in CVP) had the strongest association with AKI.

CONCLUSIONS

In an experimental setting of ventilation with high mechanical power, higher PEEP had the strongest association with AKI. The most likely physiological determinant of AKI was an increase of pleural pressure and CVP with reduced mean perfusion pressure. These changes resulted from PEEP per se and from increase in fluid administration to compensate for hemodynamic impairment consequent to high PEEP.

Assessment of Individualized Mean Perfusion Pressure Targets for the Prevention of Cardiac Surgery-Associated Acute Kidney Injury-The PrevHemAKI Randomized Controlled Trial

BACKGROUND

Retrospective studies support that mean perfusion pressure (MPP) deficit in cardiac surgery patients is associated with a higher incidence of acute kidney injury (CS-AKI). The aim of our study was to apply an algorithm based on MPP in the postoperative period to determine whether management with an individualized target reduces the incidence of CS-AKI.

METHODS

Randomized controlled trial of patients undergoing cardiac surgery with extracorporeal circulation. Adult patients submitted to valve replacement and/or bypass surgery with a high risk of CS-AKI evaluated by a Leicester score >30 were randomized to follow a target MPP of >75% of the calculated baseline or a standard hemodynamic management during the first postoperative 24 h.

RESULTS

Ninety-eight patients with an eGFR of 54 mL/min were included. There were no differences in MAP and MPP in the first 24 h between the randomized groups, although a higher use of noradrenaline was found in the intervention arm (38.78 vs. 63.27, p = 0.026). The percentage of time with MPP < 75% of measured baseline was similar in both groups (10 vs. 12.7%, p = 0.811). MAP during surgery was higher in the intervention group (73 vs. 77 mmHg, p = 0.008). The global incidence of CS-AKI was 36.7%, being 38.6% in the intervention group and 34.6% in the control group (p = 0.40). There were no differences in extrarenal complications between groups as well.

CONCLUSION

An individualized hemodynamic management based on MPP compared to standard treatment in cardiac surgery patients was safe but did not reduce the incidence of CS-AKI in our study.

Severe fluctuation in mean perfusion pressure is associated with increased risk of in-hospital mortality in critically ill patients with central venous pressure monitoring: A retrospective observational study

BACKGROUND

The mean perfusion pressure (MPP) was recently proposed to personalize tissue perfusion pressure management in critically ill patients. Severe fluctuation in MPP may be associated with adverse outcomes. We sought to determine if higher MPP variability was correlated with increased mortality in critically ill patients with CVP monitoring.

METHODS

We designed a retrospective observational study and analyzed data stored in the eICU Collaborative Research Database. Validation test was conducted in MIMIC-III database. The exposure was the coefficient of variation (CV) of MPP in the primary analyses, using the first 24 hours MPP data recorded within 72 hours in the first ICU stay. Primary endpoint was in-hospital mortality.

RESULTS

A total of 6,111 patients were included. The in-hospital mortality of 17.6% and the median MPP-CV was 12.3%. Non-survivors had significantly higher MPP-CV than survivors (13.0% vs 12.2%, p<0.001). After accounting for confounders, the highest MPP-CV in decile (CV > 19.2%) were associated with increased risk of hospital mortality compared with those in the fifth and sixth decile (adjusted OR: 1.38, 95% Cl: 1.07-1.78). These relationships remained remarkable in the multiple sensitivity analyses. The validation test with 4,153 individuals also confirmed the results when MPP-CV > 21.3% (adjusted OR: 1.46, 95% Cl: 1.05-2.03).

CONCLUSIONS

Severe fluctuation in MPP was associated with increased short-term mortality in critically ill patients with CVP monitoring.

Critical Care Management of Acute-on-Chronic Liver Failure: Certainties and Unknowns

Intensive care unit (ICU) admission is frequently required in patients with decompensated cirrhosis for organ support. This entity, known as acute-on-chronic liver failure (ACLF), is associated with high short-term mortality. ICU management of ACLF is complex, as these patients are prone to develop new organ failures and infectious or bleeding complications. Poor nutritional status, lack of effective liver support systems, and shortage of liver donors are also factors that contribute to increase their mortality. ICU therapy parallels that applied in the general ICU population in some complications but has differential characteristics in others. This review describes the current knowledge on critical care management of patients with ACLF including organ support, prognostic assessment, early liver transplantation, and futility rules. Certainties and knowledge gaps in this area are also discussed.

Comprehensive Management of Blood Pressure in Patients with Septic AKI

Acute kidney injury (AKI) is one of the serious complications of sepsis in clinical practice, and is an important cause of prolonged hospitalization, death, increased medical costs, and a huge medical burden to society. The pathogenesis of AKI associated with sepsis is relatively complex and includes hemodynamic abnormalities due to inflammatory response, oxidative stress, and shock, which subsequently cause a decrease in renal perfusion pressure and eventually lead to ischemia and hypoxia in renal tissue. Active clinical correction of hypotension can effectively improve renal microcirculatory disorders and promote the recovery of renal function. Furthermore, it has been found that in patients with a previous history of hypertension, small changes in blood pressure may be even more deleterious for kidney function. Therefore, the management of blood pressure in patients with sepsis-related AKI will directly affect the short-term and long-term renal function prognosis. This review summarizes the pathophysiological mechanisms of microcirculatory disorders affecting renal function, fluid management, vasopressor, the clinical blood pressure target, and kidney replacement therapy to provide a reference for the clinical management of sepsis-related AKI, thereby promoting the recovery of renal function for the purpose of improving patient prognosis.

Standard care versus individualized blood pressure targets among critically ill patients with shock: A multicenter feasibility and preliminary efficacy study

PURPOSE

Emerging evidence suggests that minimizing mean perfusion pressure (MPP) deficit during vasopressor therapy for shock can potentially reduce adverse kidney-related outcomes in ICU. We assessed feasibility and preliminary efficacy of individualizing MPP targets based on patients' own pre-illness basal-MPP among vasopressor-treated patients with shock.

MATERIAL AND METHODS

In this prospective before-and-after trial, 31 patients during the 'before'/observational phase and 31 patients during the 'after'/intervention phase were enrolled at two tertiary-level Australian ICUs. Feasibility endpoint was time-weighted average MPP-deficit during vasopressor therapy. Preliminary efficacy outcomes were new significant AKI, major adverse kidney events within 14 days (MAKE-14), and 90-day mortality.

RESULTS

Patients in the after group had lower MPP-deficit (median 18%, [interquartile range [IQR]: 11-23] vs. 4%, [IQR: 2-9], p < 0.001) and lower incidence of new significant AKI (8/31 [26%] vs. 1/31 [3%], p = 0.01) than the before group. The between-group differences in MAKE-14 (9/31 [29%] vs. 4/31 [13%], p = 0.12) and 90-day mortality (6/31 [19%] vs. 2/31 [6%], p = 0.13) were not statistically significant.

CONCLUSIONS

An individualized blood pressure target strategy during vasopressor therapy in ICU was feasible and appeared to be efficacious in this preliminary study. Testing this strategy in a larger randomized controlled trial is warranted.

STUDY REGISTRATION

ACTRN12617001459314.

The impact of relative hypotension on acute kidney injury progression after cardiac surgery: a multicenter retrospective cohort study

BACKGROUND

Cardiac surgery is performed worldwide, and acute kidney injury (AKI) following cardiac surgery is a risk factor for mortality. However, the optimal blood pressure target to prevent AKI after cardiac surgery remains unclear. We aimed to investigate whether relative hypotension and other hemodynamic parameters after cardiac surgery are associated with subsequent AKI progression.

METHODS

We retrospectively enrolled adult patients admitted to 14 intensive care units after elective cardiac surgery between January and December 2018. We defined mean perfusion pressure (MPP) as the difference between mean arterial pressure (MAP) and central venous pressure (CVP). The main exposure variables were time-weighted-average MPP-deficit (i.e., the percentage difference between preoperative and postoperative MPP) and time spent with MPP-deficit > 20% within the first 24 h. We defined other pressure-related hemodynamic parameters during the initial 24 h as exploratory exposure variables. The primary outcome was AKI progression, defined as one or more AKI stages using Kidney Disease: Improving Global Outcomes' creatinine and urine output criteria between 24 and 72 h. We used multivariable logistic regression analyses to assess the association between the exposure variables and AKI progression.

RESULTS

Among the 746 patients enrolled, the median time-weighted-average MPP-deficit was 20% [interquartile range (IQR): 10-27%], and the median duration with MPP-deficit > 20% was 12 h (IQR: 3-20 h). One-hundred-and-twenty patients (16.1%) experienced AKI progression. In the multivariable analyses, time-weighted-average MPP-deficit or time spent with MPP-deficit > 20% was not associated with AKI progression [odds ratio (OR): 1.01, 95% confidence interval (95% CI): 0.99-1.03]. Likewise, time spent with MPP-deficit > 20% was not associated with AKI progression (OR: 1.01, 95% CI 0.99-1.04). Among exploratory exposure variables, time-weighted-average CVP, time-weighted-average MPP, and time spent with MPP < 60 mmHg were associated with AKI progression (OR: 1.12, 95% CI 1.05-1.20; OR: 0.97, 95% CI 0.94-0.99; OR: 1.03, 95% CI 1.00-1.06, respectively).

CONCLUSIONS

Although higher CVP and lower MPP were associated with AKI progression, relative hypotension was not associated with AKI progression in patients after cardiac surgery. However, these findings were based on exploratory investigation, and further studies for validating them are required. Trial Registration UMIN-CTR, https://www.umin.ac.jp/ctr/index-j.htm , UMIN000037074.

The Association between Daily Fluid Balance and Mean Perfusion Pressure as a Critical Sign in the Intensive Care Unit of Adam Malik Central Hospital, Medan

BACKGROUND: The patient mortality rate in intensive care unit (ICU) is still high. However, we still lack measures to reduce this high mortality rate. Fluid balance is known as a marker for mortality in ICU. If the balance of fluid becomes more positive, the mortality rate consequently becomes higher. Positive fluid balance elevates central venous pressure (CVP), while this elevation increases the risk of renal failure and mortality. Mean perfusion pressure (MPP) is the difference between mean arterial pressure and CVP. AIM: We propose that the MPP value can be used as an alternative indicator to monitor excessive fluid balance since its measurement is faster and more accurate than the manual 24 h record of fluid balance. PATIENTS AND METHODS: It is expected that we can prevent excessive fluid accumulation and the subsequent mortality risk by monitoring MPP in the ICU. To investigate the association between MPP and daily fluid balance in the ICU, a prospective study was conducted from March 2016 to August 2018 in the ICU of Adam Malik Hospital, Medan. During the study period, 76 patients were admitted. Sixty-point 5% were male, with the mean age of 48.3 ± 16.5 years old. RESULTS: The overall mortality of 76 patients was 10.5%, and there was a significant negative correlation found between MPP and fluid balance (r = −0.204; p = 0.048), where a lower MPP value was associated with a more positive fluid balance. CONCLUSIONS: We conclude that there is a negative correlation between MPP and fluid balance, where a more positive fluid balance is associated with a lower MPP value. The positive fluid balance had been previously associated with increased mortality risk in the ICU.

Relative Hypotension and Adverse Kidney-related Outcomes among Critically Ill Patients with Shock. A Multicenter, Prospective Cohort Study

Rationale: There are no prospective observational studies exploring the relationship between relative hypotension and adverse kidney-related outcomes among critically ill patients with shock.Objectives: To investigate the magnitude of relative hypotension during vasopressor support among critically ill patients with shock and to determine whether such relative hypotension is associated with new significant acute kidney injury (AKI) or major adverse kidney events (MAKE) within 14 days of vasopressor initiation.Methods: At seven multidisciplinary ICUs, 302 patients, aged ≥40 years and requiring ≥4 hours of vasopressor support for nonhemorrhagic shock, were prospectively enrolled. We assessed the time-weighted average of the mean perfusion pressure (MPP) deficit (i.e., the percentage difference between patients' preillness basal MPP and achieved MPP) during vasopressor support and the percentage of time points with an MPP deficit > 20% as key exposure variables. New significant AKI was defined as an AKI-stage increase of two or more (Kidney Disease: Improving Global Outcome creatinine-based criteria).Measurements and Main Results: The median MPP deficit was 19% (interquartile range, 13-25), and 54% (interquartile range, 19-82) of time points were spent with an MPP deficit > 20%. Seventy-three (24%) patients developed new significant AKI; 86 (29%) patients developed MAKE. For every percentage increase in the time-weighted average MPP deficit, multivariable-adjusted odds of developing new significant AKI and MAKE increased by 5.6% (95% confidence interval, 2.2-9.1; P = 0.001) and 5.9% (95% confidence interval, 2.2-9.8; P = 0.002), respectively. Likewise, for every one-unit increase in the percentage of time points with an MPP deficit > 20%, multivariable-adjusted odds of developing new significant AKI and MAKE increased by 1.2% (0.3-2.2; P = 0.008) and 1.4% (0.4-2.4; P = 0.004), respectively.Conclusions: Vasopressor-treated patients with shock are often exposed to a significant degree and duration of relative hypotension, which is associated with new-onset, adverse kidney-related outcomes.Study registered with Australian New Zealand Clinical Trial Registry (ACTRN 12613001368729).

Comparison of the Hemodynamic and Temperature Effects of a 500-mL Bolus of 4% Albumin at Room Versus Body Temperature in Cardiac Surgery Patients

OBJECTIVE

To compare the hemodynamic effect of room temperature (cold) 4% albumin fluid bolus therapy (FBT) with body temperature (warm) albumin FBT.

DESIGN

Prospective, before-after trial.

SETTING

A tertiary intensive care unit (ICU).

PARTICIPANTS

Sixty ventilated, post-cardiac surgery patients prescribed with 4% albumin FBT.

INTERVENTION

Cold or warm 4% albumin 500 ml FBT.

MEASUREMENTS AND MAIN RESULTS

We recorded hemodynamic parameters before and for 30 minutes after FBT. Cardiac index (CI) and mean arterial pressure (MAP) responses were defined by a CI increase >15% and a MAP increase >10%, respectively. Immediately after FBT, median [interquartile range] core temperature changed by -0.3 [-0.4; -0.3] °C with cold albumin vs. 0.0 [0.0; 0.1]°C with warm albumin (P<0.001). The median CI increase was 0.3 [0.0; 0.5] L/min/m2 with 14 CI-responders (47%) in both groups (P>0.99). The median immediate MAP increase was 9 [3; 15] mmHg with cold albumin vs. 11 [5; 13] mmHg with warm albumin (P=0.79), with a MAP-response in 16 vs. 17 patients (P=0.99). There was an interaction between group and time for MAP (P=0.002), mean pulmonary artery pressure (PAP) (P=0.002) and core temperature (P<0.001). In the cold albumin group, after the initial response, MAP and mean PAP decreased more slowly than with warm albumin and, after the initial fall, core temperature increased toward baseline.

CONCLUSION

In postoperative cardiac surgery patients, warm albumin FBT prevents the decrease in core temperature and, after an initial similar increase, is associated with a faster return of MAP and mean PAP toward baseline.

Decreased mean perfusion pressure as an independent predictor of acute kidney injury after cardiac surgery

Acute kidney injury after cardiac surgery (AKICS) is common. Previous studies examining the role that mean arterial pressure (MAP) during cardiopulmonary bypass (CPB) may have on AKICS have not taken into account how baseline central venous pressure (CVP) and mean perfusion pressure (MPP) (i.e. MAP − CVP) can influence its evolution. To assess whether the change in MPP to the kidneys (i.e. delta MPP or DMPP) during CPB compared to baseline is an independent predictor of AKICS. After ethical approval, a retrospective observational study was performed on all patients undergoing CPB between October 2013 and June 2015 at a university-affiliated hospital. Known risk factors for the development of AKICS were recorded, as were the MPP values at baseline and during CPB. From this, statistical modelling was performed to identify predictors of postoperative AKICS. 664 patients were identified. Analysis was performed on 513 patients after exclusion. On logistic regression, significant and independent predictors of AKICS included: d20DMPP (cumulative duration of MPP values during CPB that were 20% below baseline and exceeded three consecutive minutes) (P = 0.010); baseline CVP; age; pre-operative creatinine level; and left ventricular (LV) dysfunction (ejection fraction (EF) < 45%). On alternative modelling, the cumulative number of MPP values during CPB that were 10% below baseline was also independently associated with AKICS (P = 0.003). Modelling without taking into account CVP also supported this association. The duration of differences in perfusion pressure to the kidneys during CPB compared to baseline is an independent predictor of AKICS.

Postoperative diastolic perfusion pressure is associated with the development of acute kidney injury in patients after cardiac surgery: a retrospective analysis

Background

We aimed to investigate the relationship between the perioperative hemodynamic parameters and the occurrence of cardiac surgery-associated acute kidney injury.

Methods

A retrospective study was performed in patients who underwent cardiac surgery at a tertiary referral teaching hospital. Acute kidney injury was determined according to the KDIGO criteria. We investigated the association between the perioperative hemodynamic parameters and cardiac surgery-associated acute kidney injury to identify the independent hemodynamic predictors for acute kidney injury. Subgroup analysis was further performed in patients with chronic hypertension.

Results

Among 300 patients, 29.3% developed acute kidney injury during postoperative intensive care unit period. Multivariate logistic analysis showed the postoperative nadir diastolic perfusion pressure, but not mean arterial pressure, central venous pressure and mean perfusion pressure, was independently linked to the development of acute kidney injury after cardiac surgery (odds ratio 0.945, P = 0.045). Subgroup analyses in hypertensive subjects (n = 91) showed the postoperative nadir diastolic perfusion pressure and peak central venous pressure were both independently related to the development of acute kidney injury (nadir diastolic perfusion pressure, odds ratio 0.886, P = 0.033; peak central venous pressure, odds ratio 1.328, P = 0.010, respectively).

Conclusions

Postoperative nadir diastolic perfusion pressure was independently associated with the development of cardiac surgery-associated acute kidney injury. Furthermore, central venous pressure should be considered as a potential hemodynamic target for hypertensive patients undergoing cardiac surgery.

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.

The Negative Effect of Mean Perfusion Pressure on the Development of Acute Kidney Injury after Transcatheter Aortic Valve Implantation

Objective

To evaluate the predictive value of mean perfusion pressure (mPP) in the development of acute kidney injury (AKIN) after transcatheter aortic valve implantation (TAVI).

Methods

One hundred and forty seven consecutive patients with aortic stenosis (AS) were evaluated for this study and 133 of them were included. Mean arterial pressure (mAP) and central venous pressure (CVP) were used to calculate mPP before TAVI procedure (mPP = mAP-CVP). The occurrence of AKIN was evaluated with AKIN classification according to the Valve Academic Research Consortium-2 recommendations. The patients were divided into two groups according to the receiver operating characteristic (ROC) analysis of their mPP levels (high-risk group and low-risk group).

Results

The AKIN prevalence was 22.6% in this study population. Baseline serum creatinine level, glomerular filtration rate, amount of contrast medium, and the level of mPP were determined as predictive factors for the development of AKIN.

Conclusion

The occurrence of AKIN is associated with increased morbidity and mortality rates in patients with TAVI. In addition to the amount of contrast medium and basal kidney functions, our study showed that lower mPP was strongly associated with development of AKIN after TAVI.

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.

[Causal relationships in stroke and kidney injury]

AIM

To assess the frequency, severity, and causes of acute kidney injury (AKI) in patients with stroke.

SUBJECTS AND METHODS

272 patients (143 men and 129 women) (mean age, 66.7±11.6 years) with stroke were examined. The 2008 European Stroke Organization (ESO) guidelines were used to diagnose stroke, to determine indications for and contraindications to thrombolytic therapy, and to evaluate its efficiency. Hemorrhagic and ischemic strokes (HS and IS) were diagnosed in 52 (19%) and 220 (81%) patients, respectively. AKI was diagnosed and classified according to the 2012 Kidney Disease: Improving Global Outcomes (KDIGO) guidelines.

RESULTS

AKI was diagnosed in 89 (33%) patients: 19 (36.5%) with HS and 70 (31.8%) with IS. The relative risk of death in patients with AKI-associated stroke was 2.6 (95% confidence interval (CI) 1.6-4.0). A poor outcome (the combined endpoint of death or Rankin scale scores of 4-5) was noted in 56 (62.9%) patients with AKI and in 70 (38.2 %) without AKI (χ2=14.6; p=0.0002). The relative risk of a poor outcome in patients with AKI-associated with stroke was 1.64 (95% CI 1.3-2.0). Forty-five (50.6%) patients with stroke developed AKI in the prehospital period.

CONCLUSION

AKI complicates stroke in every three patients and increases death rates. 50% of cases develop AKI in the prehospital period due to the common causes of stroke and AKI.

Validity of a protocol to estimate patients' pre-morbid basal blood pressure

PURPOSE

The pre-illness basal mean arterial BP (MAP) is an important reference point to gauge the degree of relative hypotension among unwell patients. We aimed to assess mean bias, correlation, and agreement between basal MAP measured during nighttime ambulatory BP monitoring (ABPM) and basal MAP estimated using a standardized protocol.

MATERIALS AND METHODS

For a cohort of 137 consecutive patients, aged ≥40 years, who recently underwent ABPM, a blinded investigator estimated basal MAP from up to five most recent clinic BP measurements. Both basal MAP values, measured and estimated, were compared pairwise for each participant.

RESULTS

We traced a median of 4 [interquartile range 3-5] previous BP measurements per patient over a median period of 132 [interquartile range 55-277] days up until the ABPM test. The estimated basal MAP (mean 88 ± 8 mmHg) was linearly related (Pearson's r = 0.41, p = 0.0001) to the measured basal MAP (mean 88 ± 12 mmHg). Bland-Altman plot revealed a mean bias of 0.3 mmHg with agreement limits of ±22 mmHg.

CONCLUSIONS

The mean bias between estimated and measured values for basal MAP was insignificant and modest. When a recent nighttime ABPM is unavailable, a protocol based on recent clinic BP readings can be used to estimate patient's basal MAP.

STUDY REGISTRATION

Australian New Zealand Clinical Trials Registry ACTRN12613001382763.

Blood pressure deficits in acute kidney injury: not all about the mean arterial pressure?

Acute kidney injury (AKI) is associated with increased morbidity and mortality. Although there are many causes of AKI, it is known that patients undergoing high-risk surgery are known to be at significant risk. Although much effort has centred on the minimum arterial pressure needed to maintain renal perfusion, this tends to be based on relatively crude measures such as the mean arterial pressure (MAP), which is widely used as an index for the optimal blood pressure. The rationale behind maintaining MAP is to provide adequate organ perfusion, although this is difficult to assess other than by applying crude end-points. Recent studies have examined the progression of AKI as defined by the KDIGO criteria in terms of time-weighted average values for premorbid and within-ICU haemodynamic pressure-related parameters. Although principally performed on patients who had undergone cardiovascular surgery and who were on vasopressor support, some interesting results were obtained suggesting that crude MAP may not be an adequate target in AKI. In patients with AKI progression, greater observed deficits in mean perfusion pressure, diastolic arterial perfusion, and diastolic perfusion pressures were observed. This study may highlight potential modifiable risk factors for the prevention of progression of AKI, and hopefully translate into improved outcomes.

Low mean perfusion pressure is a risk factor for progression of acute kidney injury in critically ill patients - A retrospective analysis

Background

The aim was to investigate whether mean perfusion pressure (MPP) calculated as the difference between mean arterial pressure (MAP) and central venous pressure (CVP) was associated with risk of progression from AKI I to AKI III in critically ill patients.

Methods

Retrospective analysis of adult patients admitted to a multi-disciplinary adult intensive care unit (ICU) between July 2007 and June 2009 who developed AKI I and in whom advanced haemodynamic monitoring was initiated within 12 h of diagnosis of AKI I. We compared patients with a MPP above and below the median value in the first 12 h of diagnosis of AKI. Multivariable logistic regression analyses were performed to identify independent risk factors for progression to AKI III, to explore the impact of MAP and CVP separately, and to investigate the impact of MPP in pre-defined sub-groups.

Results

Among 2118 ICU patients, 790 patients (37%) developed AKI I of whom 205 underwent advanced haemodynamic monitoring within 12 h of AKI stage I. Their median MPP was 59 mmHg. AKI I patients with a MPP ≤59 mmHg had a significantly higher risk of progressing to AKI stage III (48.6% versus 34%, respectively; p = 0.0034). This association was stronger in patients with ischemic heart disease, congestive cardiac failure or without pre-existing hypertension and in patients with a MAP <65 mmHg for >1 h. As individual components, a raised CVP was independently associated with progression to AKI stage III but MAP alone was not an independent risk factor for AKI progression.

Conclusion

MPP <60 mmHg was independently associated with AKI progression. CVP was the key component of MPP.

Minor Postoperative Increases of Creatinine Are Associated with Higher Mortality and Longer Hospital Length of Stay in Surgical Patients

BACKGROUND

Surgical patients frequently experience postoperative increases in creatinine levels. The authors hypothesized that even small increases in postoperative creatinine levels are associated with adverse outcomes.

METHODS

The authors examined the association of postoperative changes from preoperative baseline creatinine with all-cause in-hospital mortality and hospital length of stay (HLOS) in a retrospective analysis of surgical patients at a single tertiary care center between January 2006 and June 2012.

RESULTS

The data of 39,369 surgical patients (noncardiac surgery n = 37,345; cardiac surgery n = 2,024) were analyzed. Acute kidney injury (AKI)-by definition of the Kidney Disease: Improving Global Outcome group-was associated with a five-fold higher mortality (odds ratio [OR], 4.8; 95% CI, 4.1 to 5.7; P < 0.001) and a longer HLOS of 5 days (P < 0.001) after adjusting for age, sex, comorbidities, congestive heart failure, preoperative hemoglobin, preoperative creatinine, exposure to radiocontrast agent, type of surgery, and surgical AKI risk factors. Importantly, even minor creatinine increases (Δcreatinine 25 to 49% above baseline but < 0.3 mg/dl) not meeting AKI criteria were associated with a two-fold increased risk of death (OR, 1.7; 95% CI, 1.3 to 2.4; P < 0.001) and 2 days longer HLOS (P < 0.001). This was more pronounced in noncardiac surgery patients. Patients with minor creatinine increases had a five-fold risk of death (OR, 5.4; 95% CI, 1.5 to 20.3; P < 0.05) and a 3-day longer HLOS (P < 0.01) when undergoing noncardiac surgery.

CONCLUSIONS

Even minor postoperative increases in creatinine levels are associated with adverse outcomes. These results emphasize the importance to find effective therapeutic approaches to prevent or treat even mild forms of postoperative kidney dysfunction to improve surgical outcomes.

Postoperative blood pressure deficit and acute kidney injury progression in vasopressor-dependent cardiovascular surgery patients

Background

In vasopressor-dependent patients who had undergone cardiovascular surgery, we examined whether those with progression of acute kidney injury (AKI) had a greater difference (deficit) between premorbid and within-ICU hemodynamic pressure-related parameters compared to those without AKI progression.

Methods

We assessed consecutive adults who underwent cardiovascular surgery and who stayed in our ICU for at least 48 hours and received vasopressor support for more than 4 hours. We obtained premorbid and vasopressor-associated, time-weighted average values for hemodynamic pressure-related parameters (systolic [SAP], diastolic [DAP], and mean arterial pressure [MAP]; central venous pressure [CVP], mean perfusion pressure [MPP], and diastolic perfusion pressure [DPP]) and calculated deficits in those values. We defined AKI progression as an increase of at least one Kidney Disease: Improving Global Outcomes stage.

Results

We screened 159 patients who satisfied the inclusion criteria and identified 76 eligible patients. Thirty-six patients (47 %) had AKI progression. All achieved pressure-related values were similar between patients with or without AKI progression. However, deficits in DAP (P = 0.027), MPP (P = 0.023), and DPP (P = 0.002) were significantly greater in patients with AKI progression.

Conclusions

Patients with AKI progression had greater DAP, MPP, and DPP deficits compared to patients without AKI progression. Such deficits might be modifiable risk factors for the prevention of AKI progression.

Higher versus lower blood pressure targets for vasopressor therapy in shock: a multicentre pilot randomized controlled trial

PURPOSE

In shock, hypotension may contribute to inadequate oxygen delivery, organ failure and death. We conducted the Optimal Vasopressor Titration (OVATION) pilot trial to inform the design of a larger trial examining the effect of lower versus higher mean arterial pressure (MAP) targets for vasopressor therapy in shock.

METHODS

We randomly assigned critically ill patients who were presumed to suffer from vasodilatory shock regardless of admission diagnosis to a lower (60-65 mmHg) versus a higher (75-80 mmHg) MAP target. The primary objective was to measure the separation in MAP between groups. We also recorded days with protocol deviations, enrolment rate, cardiac arrhythmias and mortality for prespecified subgroups.

RESULTS

A total of 118 patients were enrolled from 11 centres (2.3 patients/site/month of screening). The between-group separation in MAP was 9 mmHg (95% CI 7-11). In the lower and higher MAP groups, we observed deviations on 12 versus 8% of all days on vasopressors (p = 0.059). Risks of cardiac arrhythmias (20 versus 36%, p = 0.07) and hospital mortality (30 versus 33%, p = 0.84) were not different between lower and higher MAP arms. Among patients aged 75 years or older, a lower MAP target was associated with reduced hospital mortality (13 versus 60%, p = 0.03) but not in younger patients.

CONCLUSIONS

This pilot study supports the feasibility of a large trial comparing lower versus higher MAP targets for shock. Further research may help delineate the reasons for vasopressor dosing in excess of prescribed targets and how individual patient characteristics modify the response to vasopressor therapy.

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.

Prediction model for critically ill patients with acute respiratory distress syndrome

BACKGROUND AND OBJECTIVES

Acute respiratory distress syndrome (ARDS) is a major cause respiratory failure in intensive care unit (ICU). Early recognition of patients at high risk of death is of vital importance in managing them. The aim of the study was to establish a prediction model by using variables that were readily available in routine clinical practice.

METHODS

The study was a secondary analysis of data obtained from the NHLBI Biologic Specimen and Data Repository Information Coordinating Center. Patients were enrolled between August 2007 and July 2008 from 33 hospitals. Demographics and laboratory findings were extracted from dataset. Univariate analyses were performed to screen variables with p<0.3. Then these variables were subject to automatic stepwise forward selection with significance level of 0.1. Interaction terms and fractional polynomials were examined for variables in the main effect model. Multiple imputations and bootstraps procedures were used to obtain estimations of coefficients with better external validation. Overall model fit and logistic regression diagnostics were explored.

MAIN RESULT

A total of 282 ARDS patients were included for model development. The final model included eight variables without interaction terms and non-linear functions. Because the variable coefficients changed substantially after exclusion of most poorly fitted and influential subjects, we estimated the coefficient after exclusion of these outliers. The equation for the fitted model was: g(Χ)=0.06×age(in years)+2.23(if on vasopressor)+1.37×potassium (mmol/l)-0.007×platelet count (×109)+0.03×heart rate (/min)-0.29×Hb(g/dl)-0.67×T(°C)+0.01×PaO_2+13, and the probability of death π(Χ)=eg(Χ)/(1+eg(Χ)).

CONCLUSION

The study established a prediction model for ARDS patients requiring mechanical ventilation. The model was examined with rigorous methodology and can be used for risk stratification in ARDS patients.

Early management of severe sepsis: concepts and controversies

Sepsis is among the most common reasons for admission to ICUs throughout the world, and it is believed to be the third most common cause of death in the United States. The pathogenetic mechanism and physiologic changes associated with sepsis are exceedingly complex, but our understanding is evolving rapidly. The major pathophysiologic changes in patients with septic shock include vasoplegic shock (distributive shock), myocardial depression, altered microvascular flow, and a diffuse endothelial injury. These pathophysiologic changes play a central role in the management of sepsis. The early management of patients with severe sepsis and septic shock centers on the administration of antibiotics, IV fluids, and vasoactive agents, followed by source control. However, the specific approach to the resuscitation of patients with septic shock remains highly controversial. This review provides a practical and physiologic-based approach to the early management of sepsis and explores the controversies surrounding the management of this complex condition.