Elsevier

Resuscitation

Volume 138, May 2019, Pages 46-52
Resuscitation

Review
Carotid artery and cerebral blood flow during experimental cardiopulmonary resuscitation: A systematic review of the literature

https://doi.org/10.1016/j.resuscitation.2019.02.016Get rights and content

Abstract

Background

The carotid artery blood flow (CABF) or cerebral blood flow (CBF) achieved with current techniques of cardiac compression in humans are unknown. Animal experiments may provide useful information on such flows and on possible techniques to optimize them.

Objectives

To obtain an estimate of carotid and cerebral blood flows during cardiac compression with different techniques.

Methods

We performed a systematic review of all studies in the English literature that measured the CABF and/or CBF during cardiac compression in experimental models of cardiac arrest, expressed as a percentage of baseline (pre-arrest) values. We compared the effect of vasopressor use, thoracic compression technique, pre-arrest infusion and animal model on maximum blood flows using standard statistical methodologies.

Results

Overall, 133 studies were reviewed. Of these, 45 studies provided information only on CABF; 77 only on CBF, and 11 studies on both flows. The overall weighted mean (±SD) CABF was 35.2 ± 27.7% of baseline. Porcine studies showed lower CABF when vasopressors were used (p = 0.0002). Studies of CBF reported a weighted mean value of 66.5 ± 48.5% of baseline. Adjunctive vasopressor therapy significantly increased CBF (p = 0.007), as did fluid administration (P = 0.049). In studies reporting both CABF and CBF, the median CABF/CBF ratio was 0.67 (range 0.21–1.96).

Conclusions

During experimental cardiac compression, compared to baseline, CABF appears to decrease much more than CBF. However results should be regarded with caution. They are affected by ancillary interventions and measurement methods, variability is marked and, in experiments measuring CABF and CBF simultaneously, their ratios range well outside physiologically plausible values.

Introduction

Cardiac arrest is a critical condition associated with a high morbidity and mortality.1, 2 Cardiopulmonary resuscitation (CPR) aims to provide adequate perfusion to vital organs during cardiac arrest, especially heart and brain. The brain, however, may not receive adequate perfusion despite technically optimal CPR. This notion is supported by the observation that, despite CPR, most resuscitated patients following cardiac arrest have neurological injury and many die because of such injury.3, 4, 5, 6, 7, 8, 9

Such poor neurological outcome is logically explained by inadequate cerebral blood flow (CBF), decreased brain oxygen levels and reduced glucose delivery during CPR, even in the presence of seemingly adequate arterial pressures.8, 9, 10, 11, 12, 13 Unfortunately, CBF cannot be measured in humans during CPR, making it difficult to assess how different approaches to CPR (closed chest thoracic compression with or without machine assistance, open chest thoracic compression) might optimize CBF. Moreover, the relationship between CABF and CBF is highly variable and unclear.14, 15 Thus, estimation of CABF during CPR in humans is unlikely to provide robust information on CBF. Given the near impossibility of measuring CABF or CBF during CPR in man, animal models have been used to estimate how different approaches to CPR may affect CBF or CABF and to estimate what percentage of pre-arrest values might be achieved during CPR. Such experimental data might provide important information on the likely adequacy of standard CPR in man, on what technical aspects of CPR may achieve best cerebral perfusion, and on whether CABF has a robust and reliable association with CBF.

Accordingly, we systematically evaluated all experimental studies of CPR that reported CABF and/or CBF. We aimed to test whether such animal experiments yielded consistent CBF and CABF values across different experiments and species, whether such values were influenced by closed vs. open CPR and whether the relationship between CABF and CBF was consistent and robust across different experiments and species. Specifically, we hypothesized that CABF and CBF during CPR would decrease by a similar amount to <50% of baseline, that open-chest CPR would yield higher CABF and CBF values than closed-chest CPR, and that ancillary interventions (vasopressor therapy, use of machine compression and fluid administration) would be associated with greater CABF and CBF.

Section snippets

Methods

We interrogated the electronic reference libraries of MEDLINE (1950–Oct 2018), EMBASE (1947–Oct 2018) and CINAHL (1987–Oct 2018). At first, we performed the search using the Boolean operator ‘OR’ with the following medical subject heading terms and text words: ‘heart arrest’, ‘cardiac arrest’. Second, we searched studies using the link ‘OR’ with the following additional words: ‘cardiac massage’, ‘heart massage’, ‘cardiopulmonary resuscitation’, ‘cardio-pulmonary resuscitation’, ‘chest

Electronic search

We identified 425 potentially relevant citations between January 1947 and October 2018. Of these, 285 studies were chosen for detailed evaluation because they were considered as having a relevant type of citation. A total of 102 unique abstracts were excluded as these focused on the period after ROSC, not reporting carotid artery or cerebral blood flow data, not focusing on CPR, due to lack of availability of the full text study and not relevant type of article. A total of 183 studies were thus

Key findings

We conducted a systematic review of the experimental literature on CPR and identified experimental studies reporting data on carotid artery blood flow (CABF) and/or cerebral blood flow (CBF) as a percentage of baseline values during CPR. Such studies showed that, during cardiac compression, CABF appears to decrease by two thirds of baseline while CBF appears to decrease by one third. However, results were affected by ancillary interventions and measurement methods, variability was marked and,

Conclusions

Animal experimentation shows that, during cardiac compression, CABF appears to decrease to one third of baseline while CBF appears to decrease to two thirds of baseline. However, results are variably affected by ancillary interventions and measurement methods, overall variability is marked and, in experiments measuring CABF and CBF simultaneously, ratios achieve physiologically impossible values. Our findings suggest that current estimates of CABF and CBF during experimental cardiac arrest are

References (18)

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    In addition, carotid blood flow (CBF) has also been investigated mainly in animal models [13,14]. However, these traditional techniques have several limitations and are difficult to apply in routine clinical practice [3,10,13]. An early animal study revealed a correlation between ROSC and the presence of pupil light reflex (PLR) monitored by traditional penlight during CPR [15].

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    Measurements of cerebral and cardiac blood flows during CPR are not available in human neonates and infants, hence researches have utilized animal cardiac arrest models to measure blood flows for the comparison of the effectiveness of different CPR techniques. Measurement of carotid artery blood flow (CABF) has been utilized as a surrogate for brain blood flow in multiple previous animal studies of cardiac arrest assessing the effectiveness of CPR.9 It is assumed that the improved quality of chest compression by TT technique observed in infant manikin models should result in higher blood flow generation during cardiac arrest, but no previous animal or human studies compared TT vs TF-CPR techniques measuring CABF or cerebral blood flow.

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