Brain energetics of cardiopulmonary cerebral resuscitation

Cerebral tissue oximetry levels during prehospital management of cardiac arrest - A prospective observational study

INTRODUCTION

Near-infrared spectroscopy (NIRS) enables continuous monitoring of regional oximetry (rSO₂). The aim of this study was to describe dynamics of regional cerebral oximetry levels during out of hospital cardiac arrest (OHCA) resuscitation, specifically around the time of restoration of spontaneous circulation (ROSC).

METHODS

This prospective observational study was performed in the prehospital setting during cardio-pulmonary resuscitation (CPR) of OHCA patients. In the three-year study period, two-hundred eighty OHCA's were responded to; rSO₂ was continuously measured throughout CPR and after attaining ROSC.

RESULTS

Final data analysis included 53 patients. Continuous rSO₂dynamics were described and data was compared amongst ROSC (22 cases) and no-ROSC (31 cases) groups. Initial rSO₂levels were below 15% (not detectable) in both groups. With ongoing CPR, rSO₂levels were higher in the ROSC group (median 22% vs. 14% in no-ROSC group, p = 0.030). Until ROSC, rSO₂levels were higher throughout CPR before ROSC (mean maximal value 47% at ROSC vs. 31% no-ROSC, p < 0.01). Furthermore, we found a pattern of significant, rapid and sustained rise in rSO₂levels minutes prior to ROSC and normalization thereafter.

CONCLUSIONS

Initial rSO₂levels during OHCA are generally undetectable by the time EMS teams initiate CPR. With CPR, rSO₂levels rise and are higher during CPR in patients who later achieve ROSC. Patients who achieve ROSC exhibit significant, rapid, and sustained rise in rSO₂minutes prior to attaining ROSC, and normalization of rSO₂ levels thereafter. Persistently low levels of rSO₂ during CPR likely portend poor neurologic outcomes.

Brain tissue oxygen pressure and cerebral metabolism in an animal model of cardiac arrest and cardiopulmonary resuscitation

OBJECTIVE

Direct measurement of brain tissue oxygenation (PbtO2) is established during spontaneous circulation, but values of PbtO2 during and after cardiopulmonary resuscitation (CPR) are unknown. The purpose of this study was to investigate: (1) the time-course of PbtO2 in an established model of CPR, and (2) the changes of cerebral venous lactate and S-100B.

METHODS

In 12 pigs (12-16 weeks, 35-45 kg), ventricular fibrillation (VF) was induced electrically during general anaesthesia. After 4 min of untreated VF, all animals were subjected to CPR (chest compression rate 100/min, FiO2 1.0) with vasopressor therapy after 7, 12, and 17 min (vasopressin 0.4, 0.4, and 0.8 U/kg, respectively). Defibrillation was performed after 22 min of cardiac arrest. After return of spontaneous circulation (ROSC), the pigs were observed for 1h.

RESULTS

After initiation of VF, PbtO2 decreased compared to baseline (mean +/- SEM; 22 +/- 6 versus 2 +/- 1 mmHg after 4 min of VF; P < 0.05). During CPR, PbtO2 increased, and reached maximum values 8 min after start of CPR (25 +/- 7 mmHg; P < 0.05 versus no-flow). No further changes were seen until ROSC. Lactate, and S-100B increased during CPR compared to baseline (16 +/- 2 versus 85 +/- 8 mg/dl, and 0.46 +/- 0.05 versus 2.12 +/- 0.40 microg/l after 13 min of CPR, respectively; P < 0.001); lactate remained elevated, while S-100B returned to baseline after ROSC.

CONCLUSIONS

Though PbtO2 returned to pre-arrest values during CPR, PbtO2 and cerebral lactate were lower than during post-arrest reperfusion with 100% oxygen, which reflected the cerebral low-flow state during CPR. The transient increase of S-100B may indicate a disturbance of the blood-brain-barrier.

Brain metabolism during cardiopulmonary resuscitation assessed with microdialysis

BACKGROUND AND PURPOSE

Microdialysis is an established tool to analyse tissue biochemistry, but the value of this technique to monitor cardiopulmonary resuscitation (CPR) effects on cerebral metabolism is unknown. The purpose of this study was to assess the effects of active-compression-decompression (ACD) CPR in combination with an inspiratory threshold valve (ITV) (=experimental CPR) vs. standard CPR on cerebral metabolism measured with microdialysis.

METHODS

Fourteen domestic pigs were surfaced-cooled to a body core temperature of 26 degrees C and ventricular fibrillation was induced, followed by 10 min of untreated cardiac arrest; and subsequently, standard (n=7) CPR vs. experimental (n=7) CPR. After 8 min of CPR, all animals received 0.4 U/kg vasopressin IV, and CPR was maintained for an additional 10 min in each group; defibrillation was attempted after a total of 28 min of cardiac arrest, including 18 min of CPR.

RESULTS

In the standard CPR group, microdialysis measurements showed a 13-fold increase of the lactate-pyruvate ratio from 7.2+/-1.3 to 95.5+/-15.4 until the end of CPR (P<0.01), followed by a further increase up to 138+/-32 during the postresuscitation period. The experimental group developed a sixfold increase of the lactate-pyruvate ratio from 7.1+/-2.0 to 51.1+/-8.7 (P<0.05), and a continuous decrease after vasopressin. In the standard resuscitated group, but not during experimental CPR, a significant increase of cerebral glucose levels from 0.6+/-0.1 to 2.6+/-0.5 mM was measured (P<0.01).

CONCLUSION

Using the technique of microdialysis we were able to measure changes of brain biochemistry during and after the very special situation of hypothermic cardiopulmonary arrest. Experimental CPR improved the lactate-pyruvate ratio, and glucose metabolism.