New conventional long-term survival normovolemic cardiac arrest pig model

Establishing a Rodent Model of Ventricular Fibrillation Cardiac Arrest With Graded Histologic and Neurologic Damage With Different Cardiac Arrest Durations

Purpose:

The aim of the study was to establish a ventricular fibrillation (VF) cardiac arrest (CA) resuscitation model with consistent neurologic and neuropathologic damage as potential therapeutic target.

Methods:

Prospectively randomized groups of experiments in two phases. In phase 1 four groups of male Sprague–Dawley rats (n = 5) were resuscitated after 6 min VFCA with 2 and 6 min basic life support durations (BLS) with and without adrenaline. In phase 2 the most promising group regarding return of spontaneous circulation (ROSC) and survival was compared with a group of 8 min CA. Resuscitability, neurologic deficit scores (NDS), and overall performance category (OPC) were assessed daily; histolopathology of the hippocampal CA1 region [hematoxylin and eosin- (viable neurons), Fluoro-Jade- (dying neurons), and Iba-1 immunostaining (microglial activation–semiquantitative)] on day 14.

Results:

Two minutes BLS and with adrenaline as most promising group of phase 1 compared with an 8 min group in phase 2 exhibited ROSC in 8 (80%) vs. 9 (82%) animals and survivors till day 14 in 7 (88%) (all OPC 1, NDS 0 ± 0) vs. 6 (67%) (5 OPC 1, 1 OPC 2, NDS 0.83 ± 2.4) animals. OPC and NDS were only significantly different at day 1 (OPC: P = 0.035; NDS: P = 0.003). Histopathologic results between groups were not significantly different; however, a smaller variance of extent of lesions was found in the 8 min group. Both CA durations caused graded neurologic, overall, such as histopathologic damage.

Conclusions:

This dynamic global ischemia model offers the possibility to evaluate further cognitive and novel neuroprotective therapy testing after CA.

Preserved brain morphology after controlled automated reperfusion of the whole body following normothermic circulatory arrest time of up to 20 minutes

OBJECTIVES

Clinical outcomes following cardiac arrest (CA) and resuscitation remain a cause for concern. The use of Controlled Automated Reperfusion of the whoLe body (CARL) confers superior neurological outcome even after extended periods of CA. We aimed at investigating clinical outcome and brain morphology preservation when employing CARL following CA periods of 20 min.

METHODS

Twenty-eight pigs were allocated to four extracorporeal circulation treatment strategies; seven others served as magnetic resonance imaging (MRI) controls. In prompt cardiopulmonary resuscitation (CPR; n = 6), induced circulatory arrest was followed immediately by open cardiac massage of 15 min, thereafter by CARL for 60 min. In delayed CPR (n = 6), induced CA was maintained for 15 min, after that open cardiac massage of 10 min duration was performed prior to extracorporeal CPR (ECPR) of 60 min. Induced CA times of 15 min in the ECPR 15' group (n = 6) and CA of 20 min in the CARL 20' group (n = 10) were followed by ECPR of 60 min and CARL of 60 min, respectively, without prior CPR. Daily neurological deficit scoring (NDS) up to the seventh day, markers of cellular injury [alanine transaminase (ALT), aspartate transaminase (AST) and neuron-specific enolase (NSE)] and brain MRI were performed.

RESULTS

100% survival and normal NDSs were achieved in all animals in the prompt CPR and ECPR 15' groups. In CARL 20', nine animals survived. In contrast, only one animal in the delayed CPR group survived; three animals died within 24 h with a further two dying on Days 4 and 5, respectively. All markers of cellular injury were elevated in the delayed CPR group, ALT [38 (20.3) to 206 U/l (158.2); P = 0.0095], AST [26 (18.8) to 97 U/l (1965.8); P = 0.0095] and NSE [0.45 (0.25) to 7.95 µg/l (24.03); P = 0.0095]. In the ECPR 15' group, only NSE [0.45 (0.15) to 1.20 µg/l (2.40); P = 0.0065] remained elevated. In the CARL 20' group, differences in ALT [36 (10) to 53 U/l (20); P = 0.0005] and NSE [0.50 (0.40) to 1.5 µg/l (0.40); P < 0.0001] values were evident. T₂-weighted MR images of the cerebellum [454 (28) to 495 mm²/s (55); U = 11; P = 0.0311], caudate nucleus [400 (59) to 467 mm²/s (42); U = 9; P = 0.0156], lentiform nucleus [377 (89) to 416 mm²/s (55); U = 11; P = 0.0311] and hippocampus [421 (109) to 511 mm²/s (58); U = 9; P = 0.0164] in the CARL 20' group showed higher signal intensities compared with controls. In delayed CPR, corresponding regions of interest on early apparent diffusion coefficient images showed a restricted diffusion.

CONCLUSIONS

In our experimental animal model of CA, CARL results in satisfactory survival at CA periods of 20 min despite detected enzyme and morphological changes. These changes did not translate to clinical neurological deficits.

Prolonged therapeutic hypothermia is more effective in attenuating brain apoptosis in a Swine cardiac arrest model

OBJECTIVES

To investigate whether 48 hours of therapeutic hypothermia is more effective to attenuate brain apoptosis than 24 hours and to determine whether the antiapoptotic effects of therapeutic hypothermia are associated with the suppressions of the cleavage of protein kinase C-δ, the cytosolic release of cytochrome c, and the cleavage of caspase 3 in a swine cardiac arrest model.

DESIGN

Prospective laboratory study.

SETTING

University laboratory.

SUBJECTS

Male domestic pigs (n = 24).

INTERVENTIONS

After 6 minutes of no-flow time that was induced by ventricular fibrillation, cardiopulmonary resuscitation was provided, and the return of spontaneous circulation was achieved. The animals were randomly assigned to the following groups: sham, normothermia, 24 hours of therapeutic hypothermia, or 48 hours of therapeutic hypothermia. Therapeutic hypothermia (core temperature, 32-34°C) was maintained for 24 or 48 hours post return of spontaneous circulation, and the animals were rewarmed for 8 hours. At 60 hours post return of spontaneous circulation, the animals were killed, and brain tissues were harvested.

MEASUREMENTS AND MAIN RESULTS

We examined cellular apoptosis and neuronal damage in the brain hippocampal cornu ammonis 1 region. We also measured the cleavage of protein kinase C-δ, the cytosolic release of cytochrome c, and the cleavage of caspase 3 in the hippocampus. The 48 hours of therapeutic hypothermia attenuated cellular apoptosis and neuronal damage when compared with normothermia. There was also a decrease in the cleavage of protein kinase C-δ, the cytosolic release of cytochrome c, and the cleavage of caspase 3. However, 24 hours of therapeutic hypothermia did not significantly attenuate cellular apoptosis or neuronal damage.

CONCLUSIONS

We found that 48 hours of therapeutic hypothermia was more effective in attenuating brain apoptosis than 24 hours of therapeutic hypothermia. We also found that the antiapoptotic effects of therapeutic hypothermia were associated with the suppressions of the cleavage of protein kinase C-δ, the cytosolic release of cytochrome c, and the cleavage of caspase 3.

Experimental cardiac arrest treatment with adrenaline, vasopressin, or placebo

BACKGROUND

The effect of vasoconstrictors in prolonged cardiopulmonary resuscitation (CPR) has not been fully clarified.

OBJECTIVES

To evaluate adrenaline and vasopressin pressure effect, and observe the return of spontaneous circulation (ROSC).

METHODS

A prospective, randomized, blinded, and placebo-controlled study. After seven minutes of untreated ventricular fibrillation, pigs received two minutes cycles of CPR. Defibrillation was attempted (4 J/kg) once at 9 minutes, and after every cycle if a shockable rhythm was present, after what CPR was immediately resumed. At 9 minutes and every five minutes intervals, 0.02 mg/kg (n = 12 pigs) adrenaline, or 0.4 U/kg (n = 12) vasopressin, or 0.2 mL/kg (n = 8) 0.9% saline solution was administered. CPR continued for 30 minutes or until the ROSC.

RESULTS

Coronary perfusion pressure increased to about 20 mmHg in the three groups. Following vasoconstrictors doses, pressure level reached 35 mmHg versus 15 mmHg with placebo (p < 0.001). Vasopressin effect remained at 15-20 mmHg after three doses versus zero with adrenaline or placebo. ROSC rate differed (p = 0.031) among adrenaline (10/12), vasopressin (6/12), and placebo (2/8). Time-to-ROSC did not differ (16 minutes), nor the number of doses previously received (one or two). There was no difference between vasoconstrictors, but against placebo, only adrenaline significantly increased the ROSC rate (p = 0.019).

CONCLUSION

The vasoconstrictors initial pressure effect was equivalent and vasopressin maintained a late effect at prolonged resuscitation. Nevertheless, when compared with placebo, only adrenaline significantly increased the ROSC rate.

Superior neurologic recovery after 15 minutes of normothermic cardiac arrest using an extracorporeal life support system for optimized blood pressure and flow

OBJECTIVE

Sudden cardiac arrest is one of the leading causes of death. Conventional CPR techniques after cardiac arrest provide circulation with reduced and varying blood flow and pressure. We hypothesize that using pressure- and flow-controlled reperfusion of the whole body improves neurological recovery and survival after 15 min of normothermic cardiac arrest.

METHODS

Pigs were randomized in two experimental groups and exposed to 15 min of ventricular fibrillation (VF). After this period, the animals in the control group received conventional CPR with open chest compression (n=6), while circulation in the treatment group (n=6) was established with an extracorporeal life support system (ECLS) to control blood pressure and flow. Follow-up included the assessment of neurological recovery and magnetic resonance imaging (MRI) for up to 7 days.

RESULTS

Five of the six animals in the control group died, one animal was resuscitated successfully. In the treatment group, 1/6 could not be separated from ECLS. Five out of the six pigs survived and were transferred to the animal facility. One animal was unable to walk and had to be sacrificed 30 hours after ECLS. The remaining 4 animals of the treatment group and the surviving pig from the control group showed complete neurological recovery. Brain MRI revealed no pathological changes.

CONCLUSION

We were able to demonstrate a significant improvement in survival after 15 minutes of normothermic cardiac arrest. These results support our hypothesis that using an ECLS for pressure- and flow-controlled circulation after circulatory arrest is superior to conventional CPR.

The effects of adenocaine (adenosine and lidocaine) on early post-resuscitation cardiac and neurological dysfunction in a porcine model of cardiac arrest

AIM

Return of spontaneous circulation (ROSC) elicits ischaemia/reperfusion injury and myocardial dysfunction. The combination of adenosine and lidocaine (AL, adenocaine) has been shown to (1) inhibit neutrophil inflammatory activation and (2) improve left ventricular function after ischaemia. We hypothesized that resuscitation with adenocaine during early moments of cardiopulmonary resuscitation (CPR) attenuates leucocyte oxidant generation and myocardial dysfunction.

METHODS

Pigs were randomized to: (1) sham (n=7), (2) cardiac arrest (CA; n=16), or 3) cardiac arrest+adenocaine (CA+AL; n=12). After 7 min of electrically induced ventricular fibrillation, start of CPR was followed by infusion of saline (CA) or adenocaine (CA+AL) for 6 min. Haemodynamics, cardiodynamics (pressure-volume loops) and leucocyte superoxide anion generation were assessed. Neurological function was evaluated after 24h by histology and neurological deficit score (0=normal; 500=brain dead).

RESULTS

Rate of ROSC was comparable between groups: CA group 11/16 and CA+AL group 7/12 p=0.57). Cardiac index transiently increased after ROSC in both groups. Left ventricular dysfunction demonstrated by a rightward shift of the intercept of end-systolic pressure-volume relations in CA was avoided in the CA+AL group. Leucocyte superoxide anion generation 2h after ROSC was significantly attenuated in the CA+AL group compared to the CA group. Neurological deficit scores [CA: median: 17.5(IQR:0-75) and CA+AL: 35(IQR:15-150)] and histopathological damage were comparable in both groups (p=0.37).

CONCLUSION

Infusion of adenocaine during early resuscitation from CA significantly improved early post-resuscitation cardiac function and attenuated leucocyte superoxide anion generation, without a change in post-ROSC neurological function. (IACUC protocol number 023-2009).

Quantitative assessment of brain microvascular and tissue oxygenation during cardiac arrest and resuscitation in pigs

Cardiac arrest is associated with a very high rate of mortality, in part due to inadequate tissue perfusion during attempts at resuscitation. Parameters such as mean arterial pressure and end-tidal carbon dioxide may not accurately reflect adequacy of tissue perfusion during cardiac resuscitation. We hypothesised that quantitative measurements of tissue oxygen tension would more accurately reflect adequacy of tissue perfusion during experimental cardiac arrest. Using oxygen-dependent quenching of phosphorescence, we made measurements of oxygen in the microcirculation and in the interstitial space of the brain and muscle in a porcine model of ventricular fibrillation and cardiopulmonary resuscitation. Measurements were performed at baseline, during untreated ventricular fibrillation, during resuscitation and after return of spontaneous circulation. After achieving stable baseline brain tissue oxygen tension, as measured using an Oxyphor G4-based phosphorescent microsensor, ventricular fibrillation resulted in an immediate reduction in all measured parameters. During cardiopulmonary resuscitation, brain oxygen tension remained unchanged. After the return of spontaneous circulation, all measured parameters including brain oxygen tension recovered to baseline levels. Muscle tissue oxygen tension followed a similar trend as the brain, but with slower response times. We conclude that measurements of brain tissue oxygen tension, which more accurately reflect adequacy of tissue perfusion during cardiac arrest and resuscitation, may contribute to the development of new strategies to optimise perfusion during cardiac resuscitation and improve patient outcomes after cardiac arrest.