Valproic Acid Combined With Postcardiac Arrest Hypothermic-Targeted Temperature Management Prevents Delayed Seizures and Improves Survival in a Rat Cardiac Arrest Model.

OBJECTIVES: High-dose valproic acid in combination with hypothermic-targeted temperature management has been reported to synergistically improve neurologic outcomes after cardiac arrest. This study investigated the potential synergistic mechanisms. DESIGN: Prospective, randomized, experimental study. SETTING: University research institution. SUBJECTS: Male Long Evans rats. INTERVENTION: Rats resuscitated from asphyxial cardiac arrest were randomized to one of the three groups: normothermic-targeted temperature management (37°C ± 1°C), hypothermic-targeted temperature management (33° ± 1° × 24 hr + placebo infusion), hypothermic-targeted temperature management plus high-dose valproic acid (300 mg/kg IV × 1 initiated 5 min post return of spontaneous circulation and infused over 20 min) (hypothermic-targeted temperature management + valproic acid). MEASUREMENTS AND MAIN RESULTS: Seventy-two-hour survival was significantly greater with hypothermic-targeted temperature management + valproic acid, compared to hypothermic-targeted temperature management and normothermic-targeted temperature management (p < 0.05). Survival with good neurologic function, neurodegeneration, expression of HSP70, phosphorylation of Akt and Erk1/2 were not significantly different between hypothermic-targeted temperature management and hypothermic-targeted temperature management + valproic acid. The prevalence of seizures during the first 72-hour postcardiac arrest was significantly lower with hypothermic-targeted temperature management + valproic acid compared to hypothermic-targeted temperature management and normothermic-targeted temperature management (p = 0.01). CONCLUSIONS: High-dose valproic acid combined with hypothermic-targeted temperature management prevents postcardiac arrest seizures and improves survival. It remains to be determined if the mechanism of seizure prevention is through the antiepileptic effect of valproic acid or direct neuroprotection. Overall, the combination of high-dose valproic acid and hypothermic-targeted temperature management remains a promising strategy to improve cardiac arrest outcomes.

Magnesium depletion in patients treated with therapeutic hypothermia after cardiac arrest.

Magnesium (Mg(2+)) depletion can have detrimental effects in postcardiac arrest patients through multiple potential mechanisms. Therapeutic hypothermia (TH) produces a Mg(2+) diuresis, but the effects of postcardiac arrest TH on serum Mg(2+) levels in patients with postcardiac arrest syndrome (PCAS) are yet to be systematically quantified. We conducted a retrospective chart review of 119 consecutive comatose PCAS patients treated with TH between 2005 and 2010 and compared them to 33 matched historic controls (HCs) seen at the same institution between 2002 and 2005 who were not treated with TH. We abstracted data from the first 96 hours postarrest, including date, time, and value of serum Mg(2+) levels and date, time, and amount of Mg(2+) repletion, along with outcomes at discharge. The median Mg(2+) level of TH patients was 2.0 mg/dL [interquartile range (IQR), 1.9-2.2 mg/dL] (0.82 mmol/L [IQR, 0.78-0.90 mmol/L]) versus 2.2 mg/dL [IQR, 1.9-2.4 mg/dL] (0.90 mmol/L [IQR, 0.82-0.99 mmol/L]) (p=0.2) in HCs. In addition, 42.9% (520/1214) of Mg(2+) levels in TH patients versus 31.9% (43/135) (p=0.014) in HC patients were below 2.0 mg/dL [0.82 mmol/L]. The average number of times the Mg(2+) level was checked in TH patients was 10.2 (range 1-18) versus 4.1 (range 1-10) in HCs. The TH patients were more likely to receive supplemental Mg(2+) than HCs (81.5% [97/119] vs. 27.3% [9/33] [p<0.01]). The mean supplemental Mg(2+) dose was 1.9 g for TH patients versus 0.5 g for HC patients. Mortality in patients treated with TH was 53.1% (60/113) versus 78.6% (22/28) (p=0.014) in HCs. Low serum Mg(2+) levels with subsequent Mg(2+) supplementation were more common in comatose patients with PCAS treated with TH compared to normothermic HC patients. The effect of untreated hypomagnesemia on postcardiac arrest outcomes remains to be determined.

Cross-talk between calpain and caspase proteolytic systems during neuronal apoptosis.

Cross-talk between calpain and caspase proteolytic systems has complicated efforts to determine their distinct roles in apoptotic cell death. This study examined the effect of overexpressing calpastatin, the specific endogenous calpain inhibitor, on the activity of the two proteolytic systems following an apoptotic stimulus. Human SH-SY5Y neuroblastoma cells were stably transfected with full-length human calpastatin cDNA resulting in 20-fold overexpression based on Western blot and 5-fold greater calpain inhibitory activity in cell extracts. Wild type and calpastatin overexpressing (CST1) cells were neuronally differentiated and apoptosis-induced with staurosporine (0.1-1.0 microm). Calpastatin overexpression decreased calpain activation, increased caspase-3-like activity, and accelerated the appearance of apoptotic nuclear morphology. Following 0.1-0.2 microm staurosporine, plasma membrane integrity based on calcein-acetoxymethyl fluorescence was significantly greater at 24 h in differentiated CST1 compared with differentiated wild type cells. However, this protective effect was lost at higher staurosporine doses (0.5-1.0 microm), which resulted in pronounced caspase-mediated degradation of the overexpressed calpastatin. These results suggest a dual role for calpains during neuronal apoptosis. In the early execution phase, calpain down-regulates caspase-3-like activity and slows progression of apoptotic nuclear morphology. Subsequent calpain activity, facilitated by caspase-mediated degradation of calpastatin, contributes to plasma membrane disruption and secondary necrosis.