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Following successful resuscitation, a significantly impaired microcirculation has been identified. The severity of the impairment of microcirculation is closely related to that of vital organ dysfunction. Sublingual microcirculation is a traditional site for the measurement of tissue perfusion. In the present study, we investigated the bulbar conjunctival microcirculatory alterations following CPR and its relationship with the changes of sublingual microcirculation in a rat model of cardiac arrest.Male Sprague-Dawley rats (450-550 g) were utilized. Ventricular fibrillation was induced and untreated for 8 min followed by 8 min of CPR. Sublingual and bulbar conjunctival microcirculatory blood flow was visualized by a sidestream dark-field imaging device at baseline, 30 min, 1, 2, 4, and 8 h post-resuscitation. Both perfused vessel density (PVD) and microcirculatory flow index (MFI) were recorded.The post-resuscitation PVD and MFI were significantly decreased in both sublingual and bulbar conjunctival sites. Sublingual PVD decreased from baseline of 5.9 ± 0.3 to 3.1 ± 0.4 n/mm at 30 min post-resuscitation and MFI from 3.0 ± 0.0 to 1.5 ± 0.3 (both P < 0.05 vs. baseline). Bulbar conjunctival PVD was significantly reduced from baseline of 6.5 ± 0.6 to 3.9 ± 0.5 n/mm at 30 min post-resuscitation and MFI from 3.0 ± 0.0 to 1.2 ± 0.4 (both P < 0.05 vs. baseline). PVD, MFI, and cardiac function did not change significantly from the 30-min measurements in the surviving rats throughout the remainder of the study (both P > 0.05 vs. 30-min post-resuscitation). The decreases in sublingual microcirculatory blood flow were closely correlated with the reductions of bulbar conjunctival microcirculatory blood flow (PVD: r = 0.87, P < 0.05; MFI: r = 0.92, P < 0.05). Myocardial function was significantly impaired in all animals after resuscitation when compared with baseline values (P < 0.05). The impairments of both sublingual and bulbar conjunctival microcirculation were significantly correlated with the impairment of myocardial function.In the rat model of cardiac arrest, the changes in sublingual microcirculatory blood flow are closely correlated with that of bulbar conjunctival microcirculatory blood flow after successful resuscitation. The changes are correlated with the severity of post-resuscitation myocardial dysfunction. Our study testified sublingual site could be substituted by bulbar conjunctival at least in the rat model of cardiac arrest. The measurement of conjunctival microcirculation may provide an accessible and convenient option as sublingual site for monitoring microcirculation in humans.

Objective: Lipid peroxidation induced by free-radical species plays a prominent role in myocardial injury following ischemia and reperfusion. However, there is a lack of data in different oxygen concentrations on myocardial lipid peroxidation during the early phase of reperfusion. In this study, we investigated whether ventilation with medium or normal concentration of oxygen would decrease the severity of myocardial lipid peroxidation and postresuscitation myocardial dysfunction., Design: Prospective, randomized, controlled experimental study., Setting: University-affiliated animal research institution., Subjects: Sixty-three healthy male Sprague-Dawley rats., Interventions: Animals were randomized into three groups: 1) 100% group, 2) 50% group, and 3) 21% group. Ventricular fibrillation was induced and untreated for 8 minutes, and defibrillation was attempted after 8 minutes of cardiopulmonary resuscitation. Ventilation with 100%, 50%, or 21% oxygen was initiated in all groups during cardiopulmonary resuscitation and 1 hour following the return of spontaneous circulation. Normoxic ventilation was maintained thereafter., Measurements and Main Results: Myocardial function, including ejection fraction and myocardial performance index, were measured at baseline, 4, or 72 hours after resuscitation. Blood samples were drawn at baseline, 15 minutes, 1, 4, or 72 hours after resuscitation for the measurements of blood gas or biomarkers. Significantly better myocardial function and longer duration of survival were observed in the 50% group. Compared with the 21% and 100% groups, a mild hyperoxia and greater oxygen extraction with lower 8-iso-prostaglandin F2α were observed in the 50% group. Pearson correlation analysis confirmed that 8-iso-prostaglandin F2α was positively correlated with myocardial performance index at 4 hours postresuscitation., Conclusions: In a rat model of cardiac arrest and resuscitation, ventilation with 50% inspired oxygen during early postischemic reperfusion phase contributed to a decreased lipid peroxidation and a better myocardial function and duration of survival.

Severe hemorrhagic shock and resuscitation is a state of global body ischemia and reperfusion that causes myocardial and cerebral dysfunction. We investigated whether remote ischemic preconditioning (RIPC) would reduce myocardial and cerebral ischemia and reperfusion injuries after hemorrhagic shock as the result of the K(ATP) channel activation. Twenty-one male rats were randomized into three groups: RIPC, RIPC with K(ATP) channel blocker, and control. Remote ischemic preconditioning was induced by four cycles of 5 min of limb ischemia followed by reperfusion for 5 min. Hemorrhagic shock was induced by removing 50% of the estimated total blood volume during an interval of 1 h. Thirty minutes after the completion of bleeding, the animals were reinfused with shed blood during the ensuing 30 min. The animals were monitored for 2 h and observed for an additional 72 h. Myocardial function was measured by echocardiography, and sublingual microcirculation was measured by a sidestream dark-field imaging device at baseline, 1 h after bleeding, 30 min after the completion of bleeding, 30 min after reinfusion, and hourly intervals thereafter. The survival and neurological function were evaluated at 12, 24, 48, and 72 h after reinfusion. At 2 h after reinfusion, ejection fraction and myocardial performance index were significantly better in the RIPC group than in the control group (P < 0.01). The sublingual microvascular flow index and perfused vessel density were significantly greater after reinfusion in the RIPC group than that in the control group (P < 0.01). The duration of survival was significantly longer, and neurological deficit score was significantly better in the RIPC group than the control animals (P < 0.01). Pretreatment with the K(ATP) channel blocker (glibenclamide) completely abolished the myocardial and cerebral protective effects of RIPC. We demonstrate, for the first time, that after severe hemorrhagic shock and resuscitation, RIPC mitigated myocardial and neurological dysfunction with improved survival by activation of the K(ATP) channel.