Increased cortical cerebral blood flow by continuous infusion of adrenaline (epinephrine) during experimental cardiopulmonary resuscitation

Blood-brain barrier permeability for the first 24 hours in hypoxic-ischemic brain injury following cardiac arrest

BACKGROUND

This study aimed to explore the changes in blood-brain barrier (BBB) permeability and intracranial pressure (ICP) for the first 24 h after the return of spontaneous circulation (ROSC) and their association with injury severity of cardiac arrest.

METHODS

This prospective study analysed the BBB permeability assessed using the albumin quotient (Qa) and ICP every 2 h for the first 24 h after ROSC. The injury severity of cardiac arrest was assessed using Pittsburgh Cardiac Arrest Category (PCAC) scores. The primary outcome was the time course of changes in the BBB permeability and ICP for the first 24 h after ROSC and their association with injury severity (PCAC scores of 1-4).

RESULTS

Qa and ICP were measured 274 and 197 times, respectively, in 32 enrolled patients. Overall, the BBB permeability increased progressively over time after ROSC, and then it increased significantly at 18 h after ROSC compared with the baseline. In contrast, the ICP revealed non-significant changes for the first 24 h after ROSC. The Qa in the PCAC 2 group was < 0.01, indicating normal or mild BBB disruption at all time points, whereas the PCAC 3 and 4 groups showed a significant increase in BBB permeability at 14 and 22 h, and 12 and 14 h after ROSC, respectively.

CONCLUSION

BBB permeability increased progressively over time for the first 24 h after ROSC despite post-resuscitation care, whereas ICP did not change over time. BBB permeability has an individual pattern when stratified by injury severity.

Effect of first epinephrine administration time on cerebral perfusion pressure and cortical cerebral blood flow in a porcine cardiac arrest model

OBJECTIVE

The optimal time for epinephrine administration and its effects on cerebral blood flow (CBF) and microcirculation remain controversial. This study aimed to assess the effect of the first administration of epinephrine on cerebral perfusion pressure (CePP) and cortical CBF in porcine cardiac arrest model.

METHODS

After 4 min of untreated ventricular fibrillation, eight of 24 swine were randomly assigned to the early, intermediate, and late groups. In each group, epinephrine was administered intravenously at 5, 10, and 15 min after cardiac arrest induction. CePP was calculated as the difference between the mean arterial pressure and intracranial pressure. Cortical CBF was measured using a laser Doppler flow probe. The outcomes were CePP and cortical CBF measured continuously during cardiopulmonary resuscitation (CPR). Mean CePP and cortical CBF were compared using analysis of variance and a linear mixed model.

RESULTS

The mean CePP was significantly different between the groups at 6-11 min after cardiac arrest induction. The mean CePP in the early group was significantly higher than that in the intermediate group at 8-10 min and that in the late group at 6-9 min and 10-11 min. The mean cortical CBF was significantly different between the groups at 9-11 min. The mean cortical CBF was significantly higher in the early group than in the intermediate and late group at 9-10 min.

CONCLUSION

Early administration of epinephrine was associated with improved CePP and cortical CBF compared to intermediate or late administration during the early period of CPR.

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.

Mildly Reduced Doses of Adrenaline Do Not Affect Key Hemodynamic Parameters during Cardio-Pulmonary Resuscitation in a Pig Model of Cardiac Arrest

Adrenaline is recommended for cardiac arrest resuscitation, but its effectiveness has been questioned recently. Achieving return of spontaneous circulation (ROSC) is essential and is obtained by increasing coronary perfusion pressure (CPP) after adrenaline injection. A threshold as high as 35 mmHg of CPP may be necessary to obtain ROSC, but increasing doses of adrenaline might be harmful to the brain. Our study aimed to compare the increase in CPP with reduced doses of adrenaline to the recommended 1 mg dose in a pig model of cardiac arrest. Fifteen domestic pigs were randomized into three groups according to the adrenaline doses: 1 mg, 0.5 mg, or 0.25 mg administered every 5 min. Cardiac arrest was induced by ventricular fibrillation; after 5 min of no-flow, mechanical chest compression was resumed. The Wilcoxon test and Kruskal-Wallis exact test were used for the comparison of groups. Fisher's exact test was used to compare categorical variables. CPP, EtCO2 level, cerebral, and tissue near-infrared spectroscopy (NIRS) were measured. CPP was significantly lower in the 0.25 mg group 90 s after the first adrenaline injection: 28.9 (21.2; 35.4) vs. 53.8 (37.8; 58.2) in the 1 mg group (p = 0.008), while there was no significant difference with 0.5 mg 39.6 (32.7; 52.5) (p = 0.056). Overall, 0.25 mg did not achieve the threshold of 35 mmHg. EtCO2 levels were higher at T12 and T14 in the 0.5 mg than in the standard group: 32 (23; 35) vs. 19 (16; 26) and 26 (20; 34) vs. 19 (12; 22) (p < 0.05). Cerebral and tissue NIRS did not show a significant difference between the three groups. CPP after 0.5 mg boluses of adrenaline was not significantly different from the recommended 1 mg in our model of cardiac arrest.

Intramuscular adrenaline for out-of-hospital cardiac arrest is associated with faster drug delivery: A feasibility study

BACKGROUND

Early adrenaline administration is associated with return of spontaneous circulation (ROSC) and survival in out-of-hospital cardiac arrest (OHCA). Animal data demonstrate a similar rate of ROSC when early intramuscular (IM) adrenaline is given compared to early intravenous (IV) adrenaline.

AIM

To evaluate the feasibility of protocolized first-dose IM adrenaline in OHCA and it's effect on time from Public Safety Access Point (PSAP) call receipt to adrenaline administration when compared to IO and IV administration.

METHODS

This is a before-and-after feasibility study of adult OHCAs in a single EMS service following adoption of a protocol for first-dose IM adrenaline. Time from PSAP call to administration and outcomes were compared to 674 historical controls (from January 1, 2013-February 8, 2021) who received at least one dose of adrenaline by IV or IO routes.

RESULTS

During the study period, first-dose IM adrenaline was administered to 99 patients (December 1, 2019-February 8, 2021). IM adrenaline was given a median of 12.2 min (95% CI 11.4-13.1 min) after the PSAP call receipt compared to 15.3 min for the IV route (95% CI 14.6-16.0 min) and 15.3 min for the IO route (95% CI 14.9-15.7 min) with a time savings of 3 min (95% CI 2-4 min). Rates of survival to hospital discharge appeared similar between groups: 10% for IM, 8% for IV and 7% for IO. However, results related to survival were underpowered for statistical comparison.

CONCLUSIONS

Within the limitations of a small sample size and before-and-after design, first-dose IM adrenaline was feasible and reduced the time to adrenaline administration.

Premenopausal-aged females have no neurological outcome advantage after out-of-hospital cardiac arrest: A multilevel analysis of North American populations

AIM

We investigated the impact of premenopausal age on neurological function at hospital discharge in patients with out-of-hospital cardiac arrest (OHCA). We hypothesized that premenopausal-aged females (18-47 years of age) with OHCA would have a higher probability of survival with favourable neurological function at hospital discharge compared with males of the same age group, older males, and older females (>53 years of age).

METHODS

Retrospective analyses of data from the Resuscitation Outcomes Consortium multi-center randomized controlled trial (June 2011-May 2015). We included adults with non-traumatic OHCA treated by emergency medical service. We stratified the cohort into four groups by age and sex: premenopausal-aged females (18-47 years of age), older females (≥53 years old), younger males (18-47 years of age), and older male. We used multilevel logistic regression to examine the association between age-sex and favourable neurological outcomes (modified Rankin Scale ≤ 3).

RESULTS

In total, 23,725 patients were included: 1050 (4.5%) premenopausal females; 1930 (8.1%) younger males; 7569 (31.9%) older females; and 13,176 (55.5%) older males. The multilevel analysis showed no difference in neurological outcome between younger males and younger females (OR 0.95, 95% CI 0.69-1.32, p = 0.75). Both older females (OR 0.36, 95% CI 0. 0.26-0.48, p < 0.001) and older males (OR 0.52, 95% CI 0.39-0.69, p < 0.001) had a significantly lower odds of favourable neurological outcome than younger females. Among all groups, older females had the worst outcomes.

CONCLUSIONS

We did not detect an association between premenopausal age and survival with good neurological outcome, suggesting females sex hormones do not impact OHCA outcomes. Our findings are not in line with results from other studies. Studies that rigorously evaluate menopausal status are required to definitively assess the impact of female sex hormones on outcomes.

Wide-field polygon-scanning photoacoustic microscopy of oxygen saturation at 1-MHz A-line rate

We report wide-field polygon-scanning functional OR-PAM that for the first time achieves 1-MHz A-line rate of oxygen saturation in vivo. We address two technical challenges. The first is a 1-MHz dual-wavelength pulsed laser that has sufficient pulse energy and ultrafast wavelength switching. The second is a polygon-scanning imaging probe that has a fast scanning speed, a large field of view, and great sensitivity. The OR-PAM system offers a B-scan rate of 477.5 Hz in a 12-mm range and a volumetric imaging rate of ∼1 Hz over a 12 × 5 mm2 scanning area. We image microvasculature and blood oxygen saturation in a 12 × 12 mm2 scanning area in 5 s. Dynamic imaging of oxygen saturation in the mouse ear is demonstrated to monitor fast response to epinephrine injection. The new wide-field fast functional imaging ability broadens the biomedical application of OR-PAM.

Epinephrine's effects on cerebrovascular and systemic hemodynamics during cardiopulmonary resuscitation

BACKGROUND

Despite controversies, epinephrine remains a mainstay of cardiopulmonary resuscitation (CPR). Recent animal studies have suggested that epinephrine may decrease cerebral blood flow (CBF) and cerebral oxygenation, possibly potentiating neurological injury during CPR. We investigated the cerebrovascular effects of intravenous epinephrine in a swine model of pediatric in-hospital cardiac arrest. The primary objectives of this study were to determine if (1) epinephrine doses have a significant acute effect on CBF and cerebral tissue oxygenation during CPR and (2) if the effect of each subsequent dose of epinephrine differs significantly from that of the first.

METHODS

One-month-old piglets (n = 20) underwent asphyxia for 7 min, ventricular fibrillation, and CPR for 10-20 min. Epinephrine (20 mcg/kg) was administered at 2, 6, 10, 14, and 18 min of CPR. Invasive (laser Doppler, brain tissue oxygen tension [PbtO₂]) and noninvasive (diffuse correlation spectroscopy and diffuse optical spectroscopy) measurements of CBF and cerebral tissue oxygenation were simultaneously recorded. Effects of subsequent epinephrine doses were compared to the first.

RESULTS

With the first epinephrine dose during CPR, CBF and cerebral tissue oxygenation increased by > 10%, as measured by each of the invasive and noninvasive measures (p < 0.001). The effects of epinephrine on CBF and cerebral tissue oxygenation decreased with subsequent doses. By the fifth dose of epinephrine, there were no demonstrable increases in CBF of cerebral tissue oxygenation. Invasive and noninvasive CBF measurements were highly correlated during asphyxia (slope effect 1.3, p < 0.001) and CPR (slope effect 0.20, p < 0.001).

CONCLUSIONS

This model suggests that epinephrine increases CBF and cerebral tissue oxygenation, but that effects wane following the third dose. Noninvasive measurements of neurological health parameters hold promise for developing and directing resuscitation strategies.

Study of the Effects of Epinephrine on Cerebral Oxygenation and Metabolism During Cardiac Arrest and Resuscitation by Hyperspectral Near-Infrared Spectroscopy

OBJECTIVES

Epinephrine is routinely administered to sudden cardiac arrest patients during resuscitation, but the neurologic effects on patients treated with epinephrine are not well understood. This study aims to assess the cerebral oxygenation and metabolism during ventricular fibrillation cardiac arrest, cardiopulmonary resuscitation, and epinephrine administration.

DESIGN

To investigate the effects of equal dosages of IV epinephrine administrated following sudden cardiac arrest as a continuous infusion or successive boluses during cardiopulmonary resuscitation, we monitored cerebral oxygenation and metabolism using hyperspectral near-infrared spectroscopy.

SETTINGS

A randomized laboratory animal study.

SUBJECTS

Nine healthy pigs.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Our study showed that although continuous epinephrine administration had no significant impact on overall cerebral hemodynamics, epinephrine boluses transiently improved cerebral oxygenation (oxygenated hemoglobin) and metabolism (cytochrome c oxidase) by 15% ± 6.7% and 49% ± 18%, respectively (p < 0.05) compared with the baseline (untreated) ventricular fibrillation. Our results suggest that the effects of epinephrine diminish with successive boluses as the impact of the third bolus on brain oxygen metabolism was 24.6% ± 3.8% less than that of the first two boluses.

CONCLUSIONS

Epinephrine administration by bolus resulted in transient improvements in cerebral oxygenation and metabolism, whereas continuous epinephrine infusion did not, compared with placebo. Future studies are needed to evaluate and optimize the use of epinephrine in cardiac arrest resuscitation, particularly the dose, timing, and mode of administration.

The role of adrenaline in cardiopulmonary resuscitation

Adrenaline has been used in the treatment of cardiac arrest for many years. It increases the likelihood of return of spontaneous circulation (ROSC), but some studies have shown that it impairs cerebral microcirculatory flow. It is possible that better short-term survival comes at the cost of worse long-term outcomes. This narrative review summarises the rationale for using adrenaline, significant studies to date, and ongoing research.

Optic nerve sheath diameter measured using early unenhanced brain computed tomography shows no correlation with neurological outcomes in patients undergoing targeted temperature management after cardiac arrest

AIM

Previous studies indicated that the optic nerve sheath diameter (ONSD) measured using brain computed tomography (CT) is a prognostic factor for poor neurological outcome after cardiac arrest. However, these studies were retrospective or included a small sample size. We performed a prospective multi-centre observational study to investigate the correlation between the ONSD on early brain CT and neurological outcomes in patients undergoing targeted temperature management (TTM).

METHODS

This study used data from the Korean Hypothermia Network prospective registry between November 2015 and October 2016. Out-of-cardiac arrest patients who underwent brain CT within 2 h after return of spontaneous circulation (ROSC) were included. The primary endpoint was neurological outcomes at 6 months (cerebral performance category; CPC); the secondary outcome was hospital mortality. The ONSD was measured using unenhanced brain CT images.

RESULTS

In total, 374 patients were included from 18 hospitals, and 329 underwent CT within 2 h after ROSC. Six months after cardiac arrest, good (CPC 1-2) and poor (CPC 3-5) neurological outcomes were observed in 99 (30.09%) and 230 (69.91%) patients, respectively. There was no significant difference in the ONSD between groups (good outcome group: 5.61 ± 0.59 mm, poor outcome group: 5.69 ± 0.79 mm; p = 0.275), nor between discharged patients who survived and those with hospital mortality (5.63 ± 0.64 mm and 5.70 ± 0.67 mm, respectively, p = 0.399).

CONCLUSION

The ONSD on initial brain CT after ROSC was not correlated with neurological outcome at 6 months in patients who underwent TTM.

Physiologic effect of repeated adrenaline (epinephrine) doses during cardiopulmonary resuscitation in the cath lab setting: A randomised porcine study

BACKGROUND

This porcine study was designed to explore the effects of repetitive intravenous adrenaline doses on physiologic parameters during CPR.

METHODS

Thirty-six adult pigs were randomised to four injections of: adrenaline 0.02 mg(kgdose)(-1), adrenaline 0.03 mg(kgdose)(-1) or saline control. The effect on systolic, diastolic and mean arterial blood pressure, cerebral perfusion pressure (CePP), end tidal carbon dioxide (ETCO2), arterial oxygen saturation via pulse oximetry (SpO2), cerebral tissue oximetry (SctO2), were analysed immediately prior to each injection and at peak arterial systolic pressure and arterial blood gases were analysed at baseline and after 15 min.

RESULT

In the group given 0.02 mg(kgdose)(-1), there were increases in all arterial blood pressures at all 4 pressure peaks but CePP only increased significantly after peak 1. A decrease in ETCO2 following peak 1 and 2 was observed. SctO2 and SpO2 were lowered following injection 2 and beyond. In the group given a 0.03 mg(kgdose)(-1), all ABP's increased at the first 4 pressure peaks but CePP only following 3 pressure peaks. Lower ETCO2, SctO2 and SpO2 were seen at peak 1 and beyond. In the two adrenaline groups, pH and Base Excess were lower and lactate levels higher compared to baseline as well as compared to the control.

CONCLUSION

Repetitive intravenous adrenaline doses increased ABP's and to some extent also CePP, but significantly decreased organ and brain perfusion. The institutional protocol number: Malmö/Lund Committee for Animal Experiment Ethics, approval reference number: M 192-10.

Neural injury after use of vasopressin and adrenaline during porcine cardiopulmonary resuscitation

BACKGROUND

Our aim was to investigate cerebral and cardiac tissue injury subsequent to use of vasopressin and adrenaline in combination compared with vasopressin alone during cardiopulmonary resuscitation (CPR).

METHODS

In a randomized, prospective, laboratory animal study 28 anesthetized piglets were subject to a 12-min untreated cardiac arrest and subsequent CPR. After 1 min of CPR, 10 of the piglets received 0.4 U/kg of arg(8)-vasopressin (V group), and 10 piglets received 0.4 U/kg of arg(8)-vasopressin, 1 min later followed by 20 µg/kg body weight of adrenaline, and another 1 min later continuous administration (10 µg/kg/min) of adrenaline (VA group). After 8 min of CPR, the piglets were defibrillated and monitored for another 3 h. Then they were killed and the brain immediately removed pending histological analysis.

RESULTS

During CPR, the VA group had higher mean blood pressure and cerebral cortical blood flow (CCBF) but similar coronary perfusion pressure. After restoration of spontaneous circulation there was no difference in the pressure variables, but CCBF tended to be (36% ± 16%) higher in the V group. Neuronal injury and signs of a disrupted blood-brain barrier (BBB) were greater, 20% ± 4% and 21% ± 4%, respectively, in the VA group. In a background study of repeated single doses of adrenaline every third minute after 5 min arrest but otherwise the same protocol, histological measurements showed even worse neural injury and disruption of the BBB.

CONCLUSION

Combined use of vasopressin and adrenaline caused greater signs of cerebral and cardiac injury than use of vasopressin alone during experimental cardiopulmonary resuscitation.

Towards cardiopulmonary resuscitation without vasoactive drugs

PURPOSE OF REVIEW

Whereas there is clear evidence for improved survival with cardiopulmonary resuscitation (CPR) and defibrillation during cardiac arrest management, there is today lacking evidence that any of the recommended and used drugs lead to any long-term benefit for the patients. In this review, we try to discuss our current view on why advanced life support (ALS) today can be performed without the use of drugs, and instead gain all focus on improving the tasks we know improve survival: CPR and defibrillation.

RECENT FINDINGS

Previous and recent cardiac arrest drug studies have been reviewed. These are mostly consisting of retrospective register data, some experimental data and a few new randomized trials. The alternative drug-free ALS concept is also discussed with relevant studies.

SUMMARY

There is currently no evidence to support any specific drugs during cardiac arrest. Good-quality CPR, early defibrillation and goal-directed postresuscitation care is more important. Healthcare systems should not prioritize implementation of unproven drugs before good quality of care can be documented. More drug studies are indeed required, and future research needs to incorporate better diagnostic tools to test more specific and tailored therapies that account for underlying causes and individual responsiveness.

Feasibility of optic nerve sheath diameter measured on initial brain computed tomography as an early neurologic outcome predictor after cardiac arrest

OBJECTIVES

Few parameters are available to predict neurologic outcome of post-cardiac arrest patients in the early stage of treatment. Optic nerve sheath diameter (ONSD) has been used to indirectly assess intracranial pressure. This study evaluated whether ONSD, an additional parameter in initial brain computed tomography (CT) scans, can be an early predictor of neurologic outcome in post-cardiac arrest patients.

METHODS

A total of 112 cardiac arrest patients between November 2012 and October 2013 were identified. Ninety-eight comatose cardiac arrest patients were evaluated with brain CT. Of these patients, after exclusion of patients whose brain CT scans were done too late or with poor baseline neurology (Cerebral Performance Category [CPC] ≥ 3), 91 patients were included for this study. The parameters of initial brain CT, i.e., gray matter-to-white matter ratio (GWR) and ONSD, were measured after clinical care as part of a retrospective reanalysis of images. ONSD on brain CT was bilaterally measured 3 mm behind the eyeball at fixed window width and level and averaged to yield the mean value. The performance of ONSD to predict poor neurologic outcome (CPC = 3 to 5) was analyzed using multiple logistic regression analysis, receiver operating characteristic (ROC) curve analysis, and cross-tabulations.

RESULTS

Twenty-three patients showed good neurologic outcomes at hospital discharge. Mean (±SD) ONSD was 5.6 (±0.3) mm in the good outcome group versus 6.3 (±0.5) mm in the poor outcome group (p < 0.001). After basic clinical covariates were controlled for, i.e., age, Glasgow Coma Scale (GCS) score (3 vs. 4-15), and time from collapse to return of spontaneous circulation (ROSC), ONSD (odds ratio [OR] = 2.1; 95% confidence interval [CI] = 1.1 to 3.9) and GWR (OR = 0.6; 95% CI = 0.4 to 0.9) were found to be significant factors for predicting poor neurologic outcome. ROC curve analysis showed that ONSD and GWR had areas under the ROC curve of 0.931 (95% CI = 0.87 to 0.98) and 0.922 (95% CI = 0.86 to 0.97), respectively. Combining the cutoff values of ONSD (6.21 mm, sensitivity = 56%; 95% CI = 43% to 68%) and GWR (1.23, sensitivity = 84%; 95% CI = 73% to 92%) to have 100% specificities, the sensitivity was improved to 92% (95% CI = 84% to 98%). Intrarater and interrater intraclass correlation coefficients between the investigators measuring ONSD were 0.888 and 0.833, respectively.

CONCLUSIONS

Optic nerve sheath diameter on initial brain CT correlated closely with the neurologic outcome of hypoxic ischemic encephalopathy and had good reliability. Additional prospective work may be justified evaluating the standardization and diagnostic performance in real time use as a predictive tool for neurologic outcome following cardiac arrest.

Analysis of Some Biogenic Amines by Micellar Liquid Chromatography

Micellar liquid chromatography (MLC) with the use of high performance liquid chromatography (HPLC) was used to determine some physicochemical parameters of six biogenic amines: adrenaline, dopamine, octopamine, histamine, 2-phenylethylamine, and tyramine. In this paper, an influence of surfactant’s concentration and pH of the micellar mobile phase on the retention of the tested substances was examined. To determine the influence of surfactant’s concentration on the retention of the tested amines, buffered solutions (at pH 7.4) of ionic surfactant—sodium dodecyl sulfate SDS (at different concentrations) with acetonitrile as an organic modifier (0.8/0.2 v/v) were used as the micellar mobile phases. To determine the influence of pH of the micellar mobile phase on the retention, mobile phases contained buffered solutions (at different pH values) of sodium dodecyl sulfate SDS (at 0.1 M) with acetonitrile (0.8/0.2 v/v). The inverse of value of retention factor () versus concentration of micelles () relationships were examined. Other physicochemical parameters of solutes such as an association constant analyte—micelle ()—and partition coefficient of analyte between stationary phase and water (hydrophobicity descriptor) () were determined by the use of Foley’s equation.

Brain death induced by cerebral haemorrhage - a new porcine model evaluated by CT angiography

BACKGROUND

Brain death and complications to brain death affects the function of organs in the potential donor. Previous animal models of brain death have not been able to fully elucidate the mechanisms behind this organ dysfunction, and none of the available animal models mimic the most common insult prior to brain death: intracerebral haemorrhage. The objective of this study was to develop a large animal model of brain death based on a controlled intracerebral haemorrhage and verified by computerised tomographic angiography (CTA).

METHODS

Twenty pigs (range: 26.6-31.2 kg) were randomised to brain death or control. Brain death was induced by infusion of blood through a stereotaxically placed needle in the internal capsule. Brain death was confirmed by the measured intracranial pressure (ICP), lack of corneal and pupillary light reflexes, and atropine test. CTA was performed 120-180 min after brain death. The pigs were observed for 8 h after brain death.

RESULTS

Brain death was declared when the ICP exceeded mean arterial pressure after a median of 36 min (range: 28-51 min). Significant increases in heart rate, and mean arterial pressure (MAP) were followed by a steep decrease. With fluid therapy, the animals demonstrated haemodynamic stability. Reflexes disappeared, and atropine did not induce an increase in heart rate in the brain dead animals. CTA confirmed loss of cerebral circulation.

CONCLUSION

This study offers a standardised, clinically relevant porcine model of brain death induced by a haemorrhagic attack. Brain death was verified by the disappearance of corneal and pupil reflex, atropine test, and CTA.

Propofol mitigates systemic oxidative injury during experimental cardiopulmonary cerebral resuscitation

Effects of propofol, an intravenous anesthetic agent that exerts potent antioxidant properties, were investigated in an experimental model of cardiac arrest and cardiopulmonary resuscitation. An extended cardiac arrest with 15 randomized piglets was studied to assess the effect of propofol or its solvent intralipid as the control group. Oxidative stress (as measured by a major F(2)-isoprostane) and inflammation (a major metabolite of PGF(2α)) were evaluated in addition to the hemodynamic evaluation, protein S-100β and in situ tissue brain damage by immunochemistry at sacrifice after 3h of reperfusion following cardiac arrest and restoration of spontaneous circulation (ROSC). ROSC increased jugular bulb plasma levels of F(2)-isoprostane and PGF(2α) metabolite significantly more in controls than in the propofol-treated group. In situ tissue damage after ischemia-reperfusion was variable among the pigs at sacrifice, but tended to be greater in the control than the propofol-treated group. Propofol significantly reduced an ROSC-mediated oxidative stress in the brain.

Intracerebral monitoring in comatose patients treated with hypothermia after a cardiac arrest

BACKGROUND

Induced mild hypothermia (32-34 degrees C) has proven to reduce ischemic brain injury and improve outcome after a cardiac arrest (CA). The aim of this investigation was to study the occurrence of increased intracranial pressure (ICP) and neurochemical metabolic changes indicating cerebral ischemia, after CA and cardiopulmonary resuscitation (CPR), when induced hypothermia was applied.

METHODS

ICP, brain chemistry and brain temperature were monitored during induced hypothermia and re-warming in four adult unconscious patients with restoration of spontaneous circulation after CA and CPR.

RESULTS

ICP was occasionally above 20 mmHg. Neurochemical changes indicating cerebral ischemia (increased lactate/pyruvate ratio) and excitoxicity (increased glutamate) were found after CA, and signs of ischemia were also observed during the re-warming phase. A biphasic increase in glycerol was seen, which may have been a result of both membrane degradation and overspill from the general circulation.

CONCLUSIONS

Intracerebral microdialysis and ICP monitoring may be used in selected patients not requiring anticoagulants and PCI to obtain information regarding the common disturbances of intracranial dynamics after CA. The results of this study underline the importance of inducing hypothermia quickly after CA and emphasize the need for developing tools for guidance of the re-warming.

A PET study of regional cerebral blood flow after experimental cardiopulmonary resuscitation

Cerebral blood flow (CBF) during cardiopulmonary resuscitation and after restoration of spontaneous circulation (ROSC) from cardiac arrest has previously been measured with the microspheres and laser Doppler techniques. We used positron emission tomography (PET) with [15O]--water to map the haemodynamic changes after ROSC in nine young pigs. After the baseline PET recording, ventricular fibrillation of 5 min duration was induced, followed by closed-chest cardiopulmonary resuscitation (CPR) in conjunction with IV administration of three bolus doses of adrenaline (epinephrine). After CPR, external defibrillatory shocks were applied to achieve ROSC. CBF was measured at intervals during 4h after ROSC. Relative to the mean global CBF at baseline (32+/-5 ml hg(-1)min(-1)), there was a substantial global increase in CBF at 10 min, especially in the diencephalon. This was followed by an interval of cortical hypoperfusion and a subsequent gradual return to baseline values.

Novel cyclooxygenase-catalyzed bioactive prostaglandin F2alpha from physiology to new principles in inflammation

Prostaglandin F2alpha (PGF2alpha), a foremost stable vasoactive cyclooxygenase (COX)-catalyzed prostaglandin, regulates a number of key physiological functions such as luteolysis, ovarian function, luteal maintenance of pregnancy, and parturition as a constitutive part of ongoing reproductive processes of the body. It has recently been implicated in the regulation of intricate pathophysiological processes, such as acute and chronic inflammation, cardiovascular and rheumatic diseases. Since the discovery of a second isoform of COXs, it has been shown that PGF2alpha can be formed in vivo from arachidonic acid through both isoforms of COXs, namely cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2). Being synthesized in various parts of the body, it metabolizes instantly to a number of rather inactive metabolites mainly in the lungs, liver, kidney, and efficiently excretes into the urine. 15-Keto-dihydro-PGF2alpha, a major stable metabolite of PGF2alpha that reflects in vivo PGF2alpha biosynthesis, is found in larger quantities than its parent compound in the circulation and urine in basal physiological conditions, with short-lived pulses during luteolysis, induced termination of pregnancy and parturition, and is increased in tissues and various body fluids during acute, sub-chronic, and severe chronic inflammation. Further, the close relationship of PGF2alpha with a number of risk factors for atherosclerosis indicates its major role in inflammation pathology. This review addresses multiple aspects of PGF2alpha in addition to its emerging role in physiology to inflammation.

Drug administration in animal studies of cardiac arrest does not reflect human clinical experience

INTRODUCTION

To date, there is no evidence showing a benefit from any advanced cardiac life support (ACLS) medication in out-of-hospital cardiac arrest (OOHCA), despite animal data to the contrary. One explanation may be a difference in the time to first drug administration. Our previous work has shown the mean time to first drug administration in clinical trials is 19.4min. We hypothesized that the average time to drug administration in large animal experiments occurs earlier than in OOHCA clinical trials.

METHODS

We conducted a literature review between 1990 and 2006 in MEDLINE using the following MeSH headings: swine, dogs, resuscitation, heart arrest, EMS, EMT, ambulance, ventricular fibrillation, drug therapy, epinephrine, vasopressin, amiodarone, lidocaine, magnesium, and sodium bicarbonate. We reviewed the abstracts of 331 studies and 197 full manuscripts. Exclusion criteria included: non-peer reviewed, all without primary animal data, and traumatic models. From these, we identified 119 papers that contained unique information on time to medication administration. The data are reported as mean, ranges, and 95% confidence intervals. Mean time to first drug administration in animal laboratory studies and clinical trials was compared with a t-test. Regression analysis was performed to determine if time to drug predicted ROSC.

RESULTS

Mean time to first drug administration in 2378 animals was 9.5min (range 3.0-28.0; 95% CI around mean 2.78, 16.22). This is less than the time reported in clinical trials (19.4min, p<0.001). Time to drug predicted ROSC (odds ratio 0.844; 95% CI 0.738, 0.966).

CONCLUSION

Shorter drug delivery time in animal models of cardiac arrest may be one reason for the failure of animal studies to translate successfully into the clinical arena.

Haemodynamic effects of adrenaline (epinephrine) depend on chest compression quality during cardiopulmonary resuscitation in pigs

BACKGROUND

Adrenaline (epinephrine) is used during cardiopulmonary resuscitation (CPR) based on animal experiments without supportive clinical data. Clinically CPR was reported recently to have much poorer quality than expected from international guidelines and what is generally done in laboratory experiments. We have studied the haemodynamic effects of adrenaline during CPR with good laboratory quality and with quality simulating clinical findings and the feasibility of monitoring these effects through VF waveform analysis.

METHODS AND RESULTS

After 4 min of cardiac arrest, followed by 4 min of basic life support, 14 pigs were randomised to ClinicalCPR (intermittent manual chest compressions, compression-to-ventilation ratio 15:2, compression depth 30-38 mm) or LabCPR (continuous mechanical chest compressions, 12 ventilations/min, compression depth 45 mm). Adrenaline 0.02 mg/kg was administered 30 s thereafter. Plasma adrenaline concentration peaked earlier with LabCPR than with ClinicalCPR, median (range), 90 (30, 150) versus 150 (90, 270) s (p = 0.007), respectively. Coronary perfusion pressure (CPP) and cortical cerebral blood flow (CCBF) increased and femoral blood flow (FBF) decreased after adrenaline during LabCPR (mean differences (95% CI) CPP 17 (6, 29) mmHg (p = 0.01), FBF -5.0 (-8.8, -1.2) ml min(-1) (p = 0.02) and median difference CCBF 12% of baseline (p = 0.04)). There were no significant effects during ClinicalCPR (mean differences (95% CI) CPP 4.7 (-3.2, 13) mmHg (p = 0.2), FBF -0.2 (-4.6, 4.2) ml min(-1)(p = 0.9) and CCBF 3.6 (-1.8, 9.0)% of baseline (p = 0.15)). Slope VF waveform analysis reflected changes in CPP.

CONCLUSION

Adrenaline improved haemodynamics during laboratory quality CPR in pigs, but not with quality simulating clinically reported CPR performance.

Increased cortical cerebral blood flow with LUCAS; a new device for mechanical chest compressions compared to standard external compressions during experimental cardiopulmonary resuscitation

OBJECTIVE

LUCAS is a new device for mechanical compression and decompression of the chest during cardiopulmonary resuscitation (CPR). The aim of this study was to compare the efficacy of this new device with standard manual external chest compressions using cerebral cortical blood flow, cerebral oxygen extraction, and end-tidal CO2 for indirect measurement of cardiac output. Drug therapy, with adrenaline (epinephrine) was eliminated in order to evaluate the effects of chest compressions alone.

METHODS

Ventricular fibrillation (VF) was induced in 14 anaesthetized pigs. After 8 min non-intervention interval, the animals were randomized into two groups. One group received external chest compressions using a new mechanical device, LUCAS. The other group received standard manual external chest compressions. The compression rate was 100 min(-1) and mechanical ventilation was resumed with 100% oxygen during CPR in both groups. No adrenaline was given. After 15 min of CPR, external defibrillatory shocks were applied to achieve restoration of spontaneous circulation (ROSC). Cortical cerebral blood flow was measured continuously using Laser-Doppler flowmetry. End-tidal CO2 was measured using mainstream capnography.

RESULTS

During CPR, the cortical cerebral blood flow was significantly higher in the group treated with LUCAS (p = 0.041). There was no difference in oxygen extraction between the groups. End-tidal CO2, an indirect measurement of the achieved cardiac output during CPR, was significantly higher in the group treated with the LUCAS device (p = 0.009). Restoration of spontaneous circulation was achieved in two animals, one from each group.

CONCLUSIONS

Chest compressions with the LUCAS device during experimental cardiopulmonary resuscitation resulted in higher cerebral blood flow and cardiac output than standard manual external chest compressions. These results strongly support prospective randomised studies in patients to evaluate this new device.

Adrenaline administration during cardiopulmonary resuscitation: poor adherence to clinical guidelines

BACKGROUND

Adrenaline does not appear to improve the outcome after cardiac arrest in clinical trials in spite of beneficial effects in experimental studies. The objective of this study was to determine whether adrenaline was administered in accordance with advanced cardiac life support (ACLS) guidelines during adult cardiopulmonary resuscitation (CPR).

METHODS

From 15 January to 31 December 2000, all patients at Uppsala University Hospital in whom CPR was attempted were registered prospectively. The duration of CPR was documented in the register and the total dose of adrenaline was retrieved retrospectively from patient records. From these data the average interval between adrenaline doses was calculated.

RESULTS

Data for evaluation of the between-dose interval of adrenaline was available in 53 of 107 registered cardiac arrests. In 68% (36/53) the average between-dose interval was longer than the 3-5 min recommended in the guidelines, and 8% (4/53) received no adrenaline. The median interval between adrenaline doses during CPR was 6.5 min (25th-75th percentile: 5.1-10.4). Adherence to guidelines was lower in out-of-hospital cardiac arrest than in in-hospital cardiac arrest (P = 0.01).

CONCLUSIONS

In the majority of cases adrenaline did not appear to be administered according to current ACLS guidelines.

Oxygen delivery and return of spontaneous circulation with ventilation:compression ratio 2:30 versus chest compressions only CPR in pigs

The need for rescue breathing during the initial management of sudden cardiac arrest is currently being debated and reevaluated. The present study was designed to compare cerebral oxygen delivery during basic life support (BLS) by chest compressions only with chest compressions plus ventilation in pigs with an obstructed airway mimicked by a valve hindering passive inhalation. Resuscitability was then studied during the subsequent advanced life support (ALS) period. After 3 min of untreated ventricular fibrillation (VF) BLS was started. The animals were randomised into two groups. One group received chest compressions only. The other group received ventilations and chest compressions with a ratio of 2:30. A gas mixture of 17% oxygen and 4% carbon dioxide was used for ventilation during BLS. After 10 min of BLS, ALS was provided. All six pigs ventilated during BLS attained a return of spontaneous circulation (ROSC) within the first 2 min of advanced cardiopulmonary resuscitation (CPR) compared with only one of six compressions-only pigs. While all except one compressions-only animal achieved ROSC before the experiment was terminated, the median time to ROSC was shorter in the ventilated group. With a ventilation:compression ratio of 2:30 the arterial oxygen content stayed at 2/3 of normal, but with compressions-only, the arterial blood was virtually desaturated with no arterio-venous oxygen difference within 1.5-2 min. Haemodynamic data did not differ between the groups. In this model of very ideal BLS, ventilation improved arterial oxygenation and the median time to ROSC was shorter. We believe that in cardiac arrest with an obstructed airway, pulmonary ventilation should still be strongly recommended.

Vasopressin versus continuous adrenaline during experimental cardiopulmonary resuscitation

OBJECTIVE

To evaluate the effects of a bolus dose of vasopressin compared to continuous adrenaline (epinephrine) infusion on vital organ blood flow during cardiopulmonary resuscitation (CPR).

METHODS

Ventricular fibrillation was induced in 24 anaesthetised pigs. After a 5-min non-intervention interval, CPR was started. After 2 min of CPR the animals were randomly assigned to receive either vasopressin (0.4 U/kg) or adrenaline (bolus of 20 microg/kg followed by continuous infusion of 10 microg/(kg min)). Defibrillation was attempted after 9 min of CPR.

RESULTS

Vasopressin generated higher cortical cerebral blood flow (P < 0.001) and lower cerebral oxygen extraction (P < 0.001) during CPR compared to continuous adrenaline. Coronary perfusion pressure during CPR was higher in vasopressin-treated pigs (P < 0.001) and successful resuscitation was achieved in 12/12 in the vasopressin group versus 5/12 in the adrenaline group (P = 0.005).

CONCLUSIONS

In this experimental model, vasopressin caused a greater increase in cortical cerebral blood flow and lower cerebral oxygen extraction during CPR compared to continuous adrenaline. Furthermore, vasopressin generated higher coronary perfusion pressure and increased the likelihood of restoring spontaneous circulation.