Dual-Task Gait Cost and Frontal Lobe Integrity in Poststroke: Results From ONDRI

Dual-task gait performance is a marker of motor-cognitive interactions modulated by the frontal lobes. After a stroke, gait disturbances are more evident, particularly when concurrently completing a mental task and walking, an effect called high dual-task cost (DTC). Following a stroke, the potential association of high-DTC, integrity of the frontal lobes and cognitive functioning is unclear. This study screened 161 participants with stroke history from the Ontario Neurodegenerative Disease Research Initiative (ONDRI)-cerebrovascular disease cohort (69.2±7.41 years of age; 31.7% women). Individuals scoring zero in the National Institute of Health Stroke Scale were analyzed (n=102). DTC was the percentage change in gait speed from the single to dual-task condition. Standardized normal-appearing white matter (NAWM) and grey matter (NAGM) volumes from superior, middle and inferior frontal lobe were compared between DTC quartiles (adjusted for age, sex, and education) using a multivariate model (MANOVA), with total frontal lobe volume as a covariate. Another model compared group performance across 5 adjusted cognitive domains (attention, memory, language, visuospatial performance, and executive functioning). Univariate tests revealed that NAWM volume in the superior frontal lobe (F=4.50; p=0.005; partial eta-squared=0.122) was significantly different across DTC quartiles. Contrast tests suggested that the first quartile had larger NAWM than the second and fourth. DTC quartiles also showed differences in attention (F=2.93; p=0.03; partial eta-squared=0.083) and contrast tests indicated that the first quartile performed significantly better than second and fourth. DTC poststroke may be a proxy for structural integrity of superior frontal lobe regions and attention.

Audit of emergency preoperative resuscitation

A total of 148 patients of mean age 61 years with acute gastrointestinal disease who were assessed as requiring preoperative resuscitation were studied. Overall, the mortality rate was 14.2 per cent and the morbidity rate 50.7 per cent. Resuscitation was associated with a mean(s.e.m.) improvement in predicted mortality rate of 4.2(0.8) per cent and in morbidity rate of 4.3(0.7) per cent. However, there was a group of patients in whom resuscitation was unsuccessful, despite there being no apparent difference in duration or methods of resuscitation from those of the rest of the population studied. A poor response to resuscitation was found in 28 patients; this was commoner in the elderly (P < 0.001) and in women (P < 0.05). Complications were more frequent in patients failing to improve with resuscitation (P < 0.001). In the group deteriorating despite resuscitative (P < 0.001). In the a greater proportion of patients with a perforated viscus (P < 0.001), whereas intestinal obstruction was less common (P < 0.05). This study demonstrates that resuscitation can be audited and quantified. Preoperative resuscitation appears to be beneficial, but there is a group that may benefit from synchronous surgery and resuscitation.

Elevated myocardial calcium and its role in sudden cardiac death

The contribution of intracellular calcium to ventricular fibrillation (VF) was investigated using chronically instrumented dogs with healed myocardial infarctions. A 2-minute coronary occlusion was initiated during the last minute of exercise. Fourteen animals developed ventricular fibrillation (susceptible) whereas the remaining 12 did not (resistant) during this exercise plus ischemia test. The test was then repeated for the susceptible animals after pretreatment with the intracellular calcium chelator BAPTA-AM (1.0 mg/kg). BAPTA-AM significantly reduced left ventricular dp/dt max and prevented VF in 8 of 12 susceptible animals. Conversely, myocardial cytosolic calcium levels were increased in resistant animals using the calcium channel agonist Bay K 8644 (30 micrograms/kg) or phenylephrine (10 micrograms.kg-1.min-1 3-5 min before occlusion). Bay K 8644 induced VF in all 5 resistant animals tested whereas phenylephrine induced VF in 8 of 12 resistant animals. BAPTA-AM pretreatment attenuated the hemodynamic effects of Bay K 8644 or phenylephrine and prevented VF in five of five Bay K 8644- and four of seven phenylephrine-treated animals. Finally, the endogenous level of calcium/calmodulin (Ca-CaM)-dependent phosphorylation of 170- and 55-kDa substrate proteins was measured (as an index of intracellular free calcium concentration). In the susceptible dog heart, the endogenous level of Ca-CaM-dependent phosphorylation was estimated to be two- to threefold higher than that observed in resistant dog heart. Treatment of resistant dog tissue with the calcium ionophore A23187 increased the level of Ca-CaM-dependent phosphorylation of these two proteins to the level observed in susceptible dog heart. These data suggest that elevated cytosolic calcium facilitates development of malignant arrhythmias and that elevated cytosolic calcium levels may be present in animals particularly susceptible to ventricular fibrillation.