Individualized blood pressure targets during postcardiac arrest intensive care:

Association of Postarrest Hypotension Burden With Unfavorable Neurologic Outcome After Pediatric Cardiac Arrest

OBJECTIVE

Quantify hypotension burden using high-resolution continuous arterial blood pressure (ABP) data and determine its association with outcome after pediatric cardiac arrest.

DESIGN

Retrospective observational study.

SETTING

Academic PICU.

PATIENTS

Children 18 years old or younger admitted with in-of-hospital or out-of-hospital cardiac arrest who had invasive ABP monitoring during postcardiac arrest care.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

High-resolution continuous ABP was analyzed up to 24 hours after the return of circulation (ROC). Hypotension burden was the time-normalized integral area between mean arterial pressure (MAP) and fifth percentile MAP for age. The primary outcome was unfavorable neurologic status (pediatric cerebral performance category ≥ 3 with change from baseline) at hospital discharge. Mann-Whitney U tests compared hypotension burden, duration, and magnitude between favorable and unfavorable patients. Multivariable logistic regression determined the association of unfavorable outcomes with hypotension burden, duration, and magnitude at various percentile thresholds from the 5th through 50th percentile for age. Of 140 patients (median age 53 [interquartile range 11-146] mo, 61% male); 63% had unfavorable outcomes. Monitoring duration was 21 (7-24) hours. Using a MAP threshold at the fifth percentile for age, the median hypotension burden was 0.01 (0-0.11) mm Hg-hours per hour, greater for patients with unfavorable compared with favorable outcomes (0 [0-0.02] vs. 0.02 [0-0.27] mm Hg-hr per hour, p < 0.001). Hypotension duration and magnitude were greater for unfavorable compared with favorable patients (0.03 [0-0.77] vs. 0.71 [0-5.01]%, p = 0.003; and 0.16 [0-1.99] vs. 2 [0-4.02] mm Hg, p = 0.001). On logistic regression, a 1-point increase in hypotension burden below the fifth percentile for age (equivalent to 1 mm Hg-hr of burden per hour of recording) was associated with increased odds of unfavorable outcome (adjusted odds ratio [aOR] 14.8; 95% CI, 1.1-200; p = 0.040). At MAP thresholds of 10th-50th percentiles for age, MAP burden below the threshold was greater in unfavorable compared with favorable patients in a dose-dependent manner.

CONCLUSIONS

High-resolution continuous ABP data can be used to quantify hypotension burden after pediatric cardiac arrest. The burden, duration, and magnitude of hypotension are associated with unfavorable neurologic outcomes.

Nurse management of noradrenaline infusions in intensive care units: An observational study

BACKGROUND

Intensive care nurse management of noradrenaline (norepinephrine) infusions is a common and essential clinical competency for patient haemodynamic support. Nurses titrate and wean noradrenaline infusions to a target blood pressure in a dynamic, high-risk, and unpredictable environment. Titration and weaning are complex interventions, and blood pressure goals are often variable.

OBJECTIVES

The aim was to examine how nurses used blood pressure targets when escalating, weaning, and titrating noradrenaline in intensive care patients admitted for haemodynamic management and explore patient blood pressure responses to changes in noradrenaline doses.

METHODS

In this naturalistic observational study, noradrenaline dose changes were classified as escalation, weaning, and titration changes and analysed to explore nursing practice. The study was undertaken in two adult medical/surgical intensive care units in Melbourne, Australia. Participants included intensive care nurses and patients who received noradrenaline infusions for haemodynamic support.

RESULTS

Observations of 14 nurse-patient dyads provided 25 h of blood pressure and noradrenaline dose data. Patient participants received weight-adjusted maximum noradrenaline doses of between 0.06 mcg/kg/min and 0.87 mcg/kg/minute, with those in the escalation group receiving dose increases of up to 5 mcg to achieve blood pressure goals. During weaning, patients maintained or increased their blood pressure as noradrenaline doses were decreased. Nurses consistently maintained blood pressures at higher than target goals, and despite constant fluctuations, they only documented blood pressure readings hourly.

CONCLUSIONS

Intensive care nurses managed noradrenaline to achieve mean arterial pressure targets that were variable and not evidence based. The disconnection between observed blood pressure fluctuations and nurse documentation of patient blood pressures was reflected in titration practices. Discrepancies between documented and actual blood pressures raised issues about data used by nurses and doctors to inform clinical practice on noradrenaline management.

Are NIRS-derived cerebral autoregulation and ABPopt values different between hemispheres in hypoxic-ischemic brain injury patients following cardiac arrest?

PURPOSE

Near-infrared spectroscopy (NIRS) has been suggested as a non-invasive monitoring technique to set cerebral autoregulation (CA) guided ABP targets (ABPopt) in comatose patients with hypoxic-ischemic brain injury (HIBI) following cardiac arrest. We aimed to determine whether NIRS-derived CA and ABPopt values differ between left and right-sided recordings in these patients.

METHODS

Bifrontal regional oxygen saturation (rSO2) was measured using INVOS or Fore-Sight devices. The Cerebral Oximetry index (COx) was determined as a CA measure. ABPopt was calculated using a published algorithm with multi-window weighted approach. A paired Wilcoxon signed rank test and intraclass correlation coefficients (ICC) were used to compare (1) systematic differences and (2) degree of agreement between left and right-sided measurements.

RESULTS

Eleven patients were monitored. In one patient there was malfunctioning of the right-sided optode and in one patient not any ABPopt value was calculated. Comparison of rSO2 and COx was possible in ten patients and ABPopt in nine patients. The average recording time was 26 (IQR, 22-42) hours. The ABPopt values were not significantly different between the bifrontal recordings (80 (95%-CI 76-84) and 82 (95%-CI 75-84) mmHg) for the left and right recordings, p = 1.0). The ICC for ABPopt was high (0.95, 0.78-0.98, p < 0.001). Similar results were obtained for rSO2 and COx.

CONCLUSION

We found no differences between left and right-sided NIRS recordings or CA estimation in comatose and ventilated HIBI patients. This suggests that in these patients without signs of localized pathology unilateral recordings might be sufficient to estimate CA status or provide ABPopt targets.

Extracorporeal cardiopulmonary resuscitation (eCPR) and cerebral perfusion: A narrative review

Extracorporeal cardiopulmonary resuscitation (eCPR) is emerging as an effective, lifesaving resuscitation strategy for select patients with prolonged or refractory cardiac arrest. Currently, a paucity of evidence-based recommendations is available to guide clinical management of eCPR patients. Despite promising results from initial clinical trials, neurological injury remains a significant cause of morbidity and mortality. Neuropathology associated with utilization of an extracorporeal circuit may interact significantly with the consequences of a prolonged low-flow state that typically precedes eCPR. In this narrative review, we explore current gaps in knowledge about cerebral perfusion over the course of cardiac arrest and resuscitation with a focus on patients treated with eCPR. We found no studies which investigated regional cerebral blood flow or cerebral autoregulation in human cohorts specific to eCPR. Studies which assessed cerebral perfusion in clinical eCPR were small and limited to near-infrared spectroscopy. Furthermore, no studies prospectively or retrospectively evaluated the relationship between epinephrine and neurological outcomes in eCPR patients. In summary, the field currently lacks a comprehensive understanding of how regional cerebral perfusion and cerebral autoregulation are temporally modified by factors such as pre-eCPR low-flow duration, vasopressors, and circuit flow rate. Elucidating these critical relationships may inform future strategies aimed at improving neurological outcomes in patients treated with lifesaving eCPR.

Protocol for an individual patient data meta-analysis on blood pressure targets after cardiac arrest

Background

Hypotension is common after cardiac arrest (CA), and current guidelines recommend using vasopressors to target mean arterial blood pressure (MAP) higher than 65 mmHg. Pilot trials have compared higher and lower MAP targets. We will review the evidence on whether higher MAP improves outcome after cardiac arrest.

Methods

This systematic review and meta‐analysis will be conducted based on a systematic search of relevant major medical databases from their inception onwards, including MEDLINE, Embase and the Cochrane Central Register of Controlled Trials (CENTRAL), as well as clinical trial registries.

We will identify randomised controlled trials published in the English language that compare targeting a MAP higher than 65–70 mmHg in CA patients using vasopressors, inotropes and intravenous fluids. The data extraction will be performed separately by two authors (a third author will be involved in case of disagreement), followed by a bias assessment with the Cochrane Risk of Bias tool using an eight‐step procedure for assessing if thresholds for clinical significance are crossed. The outcomes will be all‐cause mortality, functional long‐term outcomes and serious adverse events. We will contact the authors of the identified trials to request individual anonymised patient data to enable individual patient data meta‐analysis, aggregate data meta‐analyses, trial sequential analyses and multivariable regression, controlling for baseline characteristics. The certainty of the evidence will be assessed by the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) system. We will register this systematic review with Prospero and aim to redo it when larger trials are published in the near future.

Conclusions

This protocol defines the performance of a systematic review on whether a higher MAP after cardiac arrest improves patient outcome. Repeating this systematic review including more data likely will allow for more certainty regarding the effect of the intervention and possible sub‐groups differences.

The “Blood pressure and oxygenation targets in post resuscitation care, a randomized clinical trial”: design and statistical analysis plan

Background

Comatose patients admitted after resuscitation from cardiac arrest have a significant risk of poor outcome due to hypoxic brain injury. While numerous studies have investigated and challenged the target temperature as the efficacious part of the guideline endorsed Targeted Temperature Management (TTM) protocols, our knowledge and how the remaining parts of the TTM are optimized remain sparse. The present randomized trial investigated two aspects of the TTM protocol: target blood pressure during the ICU stay and oxygenation during mechanical ventilation. Furthermore, the efficacy of device-based post-TTM fever management is addressed.

Methods

Investigator-initiated, dual-center, randomized clinical trial in comatose OHCA patients admitted to an intensive cardiac care unit. Patients are eligible for inclusion if unconscious, older than 18 years of age, and have return of spontaneous circulation for more than 20 min.

Intervention: allocation 1:1:1:1 into a group defined by (a) blood pressure targets in double-blind intervention targeting a mean arterial blood pressure of 63 or 77 mmHg and (b) restrictive (9–10 kPa) or liberal (13–14 kPa) of arterial oxygen concentration during mechanical ventilation. As a subordinate intervention, device-based active fever management is discontinued after 36 h or 72. Patients will otherwise receive protocolized standard of care according to international guidelines, including targeted temperature management at 36 °C for 24 h, sedation with fentanyl and propofol, and multimodal neuro-prognostication. Primary endpoint: Discharge from hospital in poor neurological status (Cerebral Performance category 3 or 4) or death, whichever comes first. Secondary outcomes: Time to initiation of renal replacement therapy or death, neuron-specific enolase (NSE) level at 48 h, MOCA score at day 90, Modified Ranking Scale (mRS) and CPC at 3 months, NT-pro-BNP at 90 days, eGFR and LVEF at 90 days, daily cumulated vasopressor requirement during ICU stay, and need for a combination of vasopressors and inotropic agents or mechanical circulatory support.

Discussion

We hypothesize that low or high target blood pressure and restrictive and liberal oxygen administration will have an impact on mortality by reducing the risk and degree of hypoxic brain injury. This will be assessment neurological outcome and biochemical and neuropsychological testing after 90 days.

Trial registration

ClinicalTrials.gov NCT03141099. Registered on May 2017 (retrospectively registered)

Postresuscitation care and prognostication

PURPOSE OF REVIEW

Most patients who are successfully resuscitated after cardiac arrest are initially comatose and require mechanical ventilation and other organ support in an ICU. Knowledge about the optimal strategy for treating these patients is evolving rapidly. This review will summarize the evidence on key aspects of postarrest care and prognostication, with a focus on actionable parameters that may impact patient survival and neurologic outcomes.

RECENT FINDINGS

Optimal targets for arterial blood oxygen and carbon dioxide in comatose postcardiac arrest patients remain uncertain. Observational data are conflicting and the few randomized controlled trials to date have failed to show that different ranges of blood oxygen and carbon dioxide values impact on biomarkers of neurological injury. The Targeted Temperature Management 2 (TTM-2) trial has documented no difference in 6-month mortality among comatose postcardiac arrest patients managed at 33 oC versus controlled normothermia. An extensive systematic review of the evidence on prognostication of outcome among comatose postcardiac arrest patients underpins new prognostication guidelines.

SUMMARY

Clinical guidelines for postresuscitation care have recently been updated and incorporate all the available science supporting the treatment of postcardiac arrests. At a minimum, fever should be strictly avoided in comatose postcardiac patients. Prognostication must involve multiple modalities and should not be attempted until assessment confounders have been sufficiently excluded.

Association of deranged cerebrovascular reactivity with brain injury following cardiac arrest: a post-hoc analysis of the COMACARE trial

BACKGROUND

Impaired cerebrovascular reactivity (CVR) is one feature of post cardiac arrest encephalopathy. We studied the incidence and features of CVR by near infrared spectroscopy (NIRS) and associations with outcome and biomarkers of brain injury.

METHODS

A post-hoc analysis of 120 comatose OHCA patients continuously monitored with NIRS and randomised to low- or high-normal oxygen, carbon dioxide and mean arterial blood pressure (MAP) targets for 48 h. The tissue oximetry index (TO_x) generated by the moving correlation coefficient between cerebral tissue oxygenation measured by NIRS and MAP was used as a dynamic index of CVR with TO_x > 0 indicating impaired reactivity and TO_x > 0.3 used to delineate the lower and upper MAP bounds for disrupted CVR. TO_x was analysed in the 0-12, 12-24, 24-48 h time-periods and integrated over 0-48 h. The primary outcome was the association between TO_x and six-month functional outcome dichotomised by the cerebral performance category (CPC1-2 good vs. 3-5 poor). Secondary outcomes included associations with MAP bounds for CVR and biomarkers of brain injury.

RESULTS

In 108 patients with sufficient data to calculate TO_x, 76 patients (70%) had impaired CVR and among these, chronic hypertension was more common (58% vs. 31%, p = 0.002). Integrated TO_x for 0-48 h was higher in patients with poor outcome than in patients with good outcome (0.89 95% CI [- 1.17 to 2.94] vs. - 2.71 95% CI [- 4.16 to - 1.26], p = 0.05). Patients with poor outcomes had a decreased upper MAP bound of CVR over time (p = 0.001), including the high-normal oxygen (p = 0.002), carbon dioxide (p = 0.012) and MAP (p = 0.001) groups. The MAP range of maintained CVR was narrower in all time intervals and intervention groups (p < 0.05). NfL concentrations were higher in patients with impaired CVR compared to those with intact CVR (43 IQR [15-650] vs 20 IQR [13-199] pg/ml, p = 0.042).

CONCLUSION

Impaired CVR over 48 h was more common in patients with chronic hypertension and associated with poor outcome. Decreased upper MAP bound and a narrower MAP range for maintained CVR were associated with poor outcome and more severe brain injury assessed with NfL. Trial registration ClinicalTrials.gov, NCT02698917 .

Adrenaline improves regional cerebral blood flow, cerebral oxygenation and cerebral metabolism during CPR in a porcine cardiac arrest model using low-flow extracorporeal support

BACKGROUND

The effects of adrenaline on cerebral blood vessels during cardiopulmonary resuscitation (CPR) are not well understood. We developed an extracorporeal CPR model that maintains constant low systemic blood flow while allowing adrenaline-associated effects on cerebral vasculature to be assessed at different mean arterial pressure (MAP) levels independently of the effects on systemic blood flow.

METHODS

After eight minutes of cardiac arrest, low-flow extracorporeal life support (ECLS) (30 ml/kg/min) was started in fourteen pigs. After ten minutes, continuous adrenaline administration was started to achieve MAP values of 40 (n = 7) or 60 mmHg (n = 7). Measurements included intracranial pressure (ICP), cerebral perfusion pressure (CePP), laser-Doppler-derived regional cerebral blood flow (CBF), cerebral regional oxygen saturation (rSO₂), brain tissue oxygen tension (P_btO₂) and extracellular cerebral metabolites assessed by cerebral microdialysis.

RESULTS

During ECLS without adrenaline, regional CBF increased by only 5% (25th to 75th percentile: -3 to 14; p=0.2642) and P_btO₂ by 6% (0-15; p=0.0073) despite a significant increase in MAP to 28 mmHg (25-30; p<0.0001) and CePP to 10 mmHg (8-13; p<0.0001). Accordingly, cerebral microdialysis parameters showed a profound hypoxic-ischemic pattern. Adrenaline administration significantly improved regional CBF to 29±14% (p=0.0098) and 61±25% (p<0.001) and P_btO₂ to 15±11% and 130±82% (both p<0.001) of baseline in the MAP 40 mmHg and MAP 60 mmHg groups, respectively. Importantly, MAP of 60 mmHg was associated with metabolic improvement.

CONCLUSION

This study shows that adrenaline administration during constant low systemic blood flow increases CePP, regional CBF, cerebral oxygenation and cerebral metabolism.