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

Blood Pressure Goals in Critically Ill Patients

Blood pressure goals in the intensive care unit (ICU) have been extensively investigated in large datasets and have been associated with various harm thresholds at or greater than a mean pressure of 65 mm Hg. While it is difficult to perform interventional randomized trials of blood pressure in the ICU, important evidence does not support defense of a higher pressure, except in retrospective database analyses. Perfusion pressure may be a more important target than mean pressure, even more so in the vulnerable patient population. In the cardiac ICU, blood pressure targets are tailored to specific cardiac pathophysiology and patient characteristics. Generally, the goal is to maintain adequate blood pressure within a certain range to support cardiac function and to ensure end organ perfusion. Individualized targets demand the use of both invasive and noninvasive monitoring modalities and frequent titration of medications and/or mechanical circulatory support where necessary. In this review, we aim to identify appropriate blood pressure targets in the ICU, recognizing special patient populations and outlining the risk factors and predictors of end organ failure.

Postoperative Blood Pressure Deficit and Acute Kidney Injury After Liver Transplant

OBJECTIVES

Acute kidney injury is a common cause of morbidity in liver transplant recipients. In critically ill patients who received an orthotopic liver transplant, we examined whether those with acute kidney injury had a greater deficit between pretransplant and posttransplant hemodynamic pressure-related parameters compared with those without acute kidney injury in the early postoperative period.

MATERIALS AND METHODS

We included patients who underwent an orthotopic liver transplant during the study period. We obtained premorbid and intensive care unit time-weighted average values for hemodynamic pressure-related parameters (systolic, diastolic, and mean arterial pressure; central venous pressure; mean perfusion pressure; and diastolic perfusion pressure) and calculated deficits in those values. We defined acute kidney injury progression as an increase of ≥1 Kidney Disease: Improving Global Outcomes stage.

RESULTS

We included 150 eligible transplantrecipients, with 88 (59%) having acute kidney injury progression. Acute kidney injury was associated with worse clinical outcomes. All achieved pressure-related values were similar between transplant recipients with or without acute kidney injury progression. However, those with acute kidney injury versus those without progression had greater diastolic perfusion pressure deficit at 12 hours (-8.33% vs 1.93%; P = .037) and 24 hours (-7.38% vs 5.11%; P = .002) and increased central venous pressure at 24 hours (46.13% vs 15%; P = .043) and 48 hours (40% vs 20.87%; P = .039).

CONCLUSIONS

Patients with acute kidney injury progression had a greater diastolic perfusion pressure deficit and increased central venous pressure compared with patients without progression. Such deficits might be modifiable risk factors for the prevention of acute kidney injury progression.

Evaluation of blood pressure trajectories and outcome in critically ill children with initial hypertension on admission to Paediatric Intensive Care

OBJECTIVE

Hypertension on paediatric intensive care (PICU) is associated with adverse outcomes. Management is complex; hypertension often represents a physiological adaptive response and exposure to hypertension could lead to altered pressure-flow autoregulation. International treatment consensus is to avoid rapid blood pressure (BP) reduction. Our aim was to examine if the rate and magnitude of BP reduction in hypertensive patients was correlated with harm.

PATIENTS AND METHODS

We performed a single centre, retrospective, observational study in a quaternary PICU analysing the first 24 h post admission high resolution BP profiles of children with admission BP above the 95^th centile. Individual BP profiles were analysed regarding both time spent and magnitude below a threshold; 75% of the admission BP in the first 24 h. Outcomes were organ support-free days at day 28, change in serum creatinine and PICU mortality.

MAIN FINDINGS

Of 3069 admissions in a 36-month period (2016-2018), 21.7% had initial hypertension on admission to PICU. A total of 3,259,111 BP measurements (99.4% invasive) were available. Pre-existing hypertension was documented in 4.9% of patients. Both time spent and magnitude below threshold BP was poorly correlated with duration of required organ support and risk of death after adjusting for PIM score, pre-existing hypertension and raised intracranial pressure. We did find an association with a rise in serum creatinine on both uni- and multivariable analysis.

CONCLUSIONS

The risk of harm due to early and significant reduction of raised blood pressure in critically ill children appears to be limited.

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 critical care literature 2020

Given the dramatic increase in critically ill patients who present to the emergency department for care, along with the persistence of boarding of critically ill patients, it is imperative for the emergency physician to be knowledgeable about recent developments in resuscitation and critical care medicine. This review summarizes important articles published in 2020 that pertain to the resuscitation and care of select critically ill patients. These articles have been selected based on the authors annual review of key critical care, emergency medicine and medicine journals and their opinion of the importance of study findings as it pertains to the care of critically ill ED patients. Several key findings from the studies discussed in this paper include the administration of dexamethasone to patients with COVID-19 infection who require mechanical ventilation or supplemental oxygen, the use of lower levels of positive end-expiratory pressure for patients without acute respiratory distress syndrome, and early initiation of extracorporeal membrane oxygenation for out-of-hospital cardiac arrest patients with refractory ventricular fibrillation if resources are available. Furthermore, the emergency physician should not administer tranexamic acid to patients with acute gastrointestinal bleeding or administer the combination of vitamin C, thiamine, and hydrocortisone for patients with septic shock. Finally, the emergency physician should titrate vasopressor medications to more closely match a patient's chronic perfusion pressure rather than target a mean arterial blood pressure of 65 mmHg for all critically ill patients.

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).