CBF and CBF/Pco₂ reactivity in childhood strangulation

Four children with self-inflicted strangulation injuries had cerebral blood flow determined by stable xenon computed tomography (XeCTCBF) within 24 hours of admission. All had suffered a severe hypoxic-ischemic cerebral injury; 3 initially had fixed pupils, all were apneic with varying bradyarrhythmias, and the initial mean arterial pH was 7.26 (± 0.18). The initial blood glucose values were > 300 mg/dl (334 and 351 mg/dl) in the 2 patients who died compared to the 2 who survived (104 and 295 mg/dl). The cardiac index was depressed during the first several days of hospitalization in the 2 patients who died (< 2.0 L/min/m²) compared to the 2 who survived. Total CBF was normal (63 ± 8 ml/min/100 gm) and local variations in CBF were present. Pco₂ reactivity was determined by hyperventilating the 4 patients for 20 min from an end tidal Pco₂ of 39 ± 3 torr to 29 ± 1 torr and then repeating the XeCTCBF study. Marked regional variability in the CBF/Pco₂ response was observed, ranging from 0.5-5.5 ml/min/100 gm/torr Pco₂. In the 2 patients who died, the CBF/Pco₂ was decreased (1.2 ml/min/100 gm/torr Pco₂) compared to the 2 patients who survived (2.1 ml/min/100 gm/torr Pco₂). Although CBF was normal in these 4 children, the hyperventilation response was depressed, variable, and even paradoxical which may be important in the evolution of further brain injury and is a critical factor in deciding whether hyperventilation may be of clinical benefit. Three factors correlated with poor outcome and ultimately death in 2 patients: initial blood glucose > 300 mg/dl; CBF/Pco₂ response < 2.0 ml/min/100 gm/torr Pco₂; and cardiac index < 2.0 L/min/m² for longer than 12-24 hours.