Strength of Association between Infarct Volume and Clinical Outcome Depends on the Magnitude of Infarct Size: Results from the ESCAPE-NA1 Trial

BACKGROUND AND PURPOSE

Infarct volume is an important predictor of clinical outcome in acute stroke. We hypothesized that the association of infarct volume and clinical outcome changes with the magnitude of infarct size.

MATERIALS AND METHODS

Data were derived from the Safety and Efficacy of Nerinetide in Subjects Undergoing Endovascular Thrombectomy for Stroke (ESCAPE-NA1) trial, in which patients with acute stroke with large-vessel occlusion were randomized to endovascular treatment plus either nerinetide or a placebo. Infarct volume was manually segmented on 24-hour noncontrast CT or DWI. The relationship between infarct volume and good outcome, defined as mRS 0-2 at 90 days, was plotted. Patients were categorized on the basis of visual grouping at the curve shoulders of the infarct volume/outcome plot. The relationship between infarct volume and adjusted probability of good outcome was fitted with linear or polynomial functions as appropriate in each group.

RESULTS

We included 1099 individuals in the study. Median infarct volume at 24 hours was 24.9 mL (interquartile range [IQR] = 6.6-92.2 mL). On the basis of the infarct volume/outcome plot, 4 infarct volume groups were defined (IQR = 0-15 mL, 15.1-70 mL, 70.1-200 mL, >200 mL). Proportions of good outcome in the 4 groups were 359/431 (83.3%), 219/337 (65.0%), 71/201 (35.3%), and 16/130 (12.3%), respectively. In small infarcts (IQR = 0-15 mL), no relationship with outcome was appreciated. In patients with intermediate infarct volume (IQR = 15-200 mL), there was progressive importance of volume as an outcome predictor. In infarcts of > 200 mL, outcomes were overall poor.

CONCLUSIONS

The relationship between infarct volume and clinical outcome varies nonlinearly with the magnitude of infarct size. Infarct volume was linearly associated with decreased chances of achieving good outcome in patients with moderate-to-large infarcts, but not in those with small infarcts. In very large infarcts, a near-deterministic association with poor outcome was seen.

Can increased nutrition raise cereal yields to the rainfall-limited potential in the high rainfall cropping zone of south Western Australia?

Average yield of wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.) in the high rainfall cropping zone (>750 mm) of south Western Australia from 1996 to 2001 was 2.5 t/ha. This is far below the water-limited potential yield (water losses of 110 mm, transpiration efficiency of 20 kg/ha.mm) of 6–8 t/ha. Nutrition of the cereal crops has been regarded as one constraint to reaching the potential yield, although grain yield increases (responses) under conventional management practices (a series of full cultivation operations) have been inconsistent. Three experiments, with a total of five trial sites conducted over two seasons, were carried out to test the response of wheat and barley to fertiliser applications of nitrogen (N), phosphorus (P), potassium (K), sulfur (S) and trace elements (TE). Various combinations of nutrients were applied. These ranged from no fertiliser (nil), to farmer practice (N at rates at 34–82 kg/ha, P at 3–17 kg/ha, K at 0–50 kg/ha and S at 4–11 kg/ha), to nutrients calculated to supply the needs of a 6–8 t/ha cereal crop (N, P, K, S, TE). The aim was to determine whether the supply of non-limiting levels of crop nutrients could raise yields to the potential yield as determined by seasonal rainfall. In the drier seasons experienced in 2001 and 2002 at Arthur River and Cranbrook, with growing season rainfall (May–November) up to about 350 mm, it was possible to raise grain yields to levels at or above the calculated rainfall-limited potential with increased nutrition (4.2 t/ha for barley and 4.5 t/ha for wheat). However, in the wetter environment of Boyup Brook in 2002, where seasonal rainfall was greater than 500 mm, extra nutrition by itself was not sufficient to reach the water-limited potential, even where the yields were increased from 3.5 to 5.2 t/ha for wheat and from 3.9 to 4.5 t/ha for barley. Further experimentation is required to clarify the factors limiting responses to nutrition when the growing season rainfall is greater than 500 mm and thus allow greater confidence in extrapolating these results in the high rainfall cropping zone of Western Australia. In wheat, the highest profits were obtained from the complete fertiliser strategy (N, P, K, S, TE). However, for barley, the greatest profits were not obtained with the highest grain yields and fertiliser strategies due to decreased grain quality.

Cardiac electrophysiology and conduction pathway ablation

Invasive cardiac electrophysiological (EP) testing and transcatheter ablation are new methods available for the diagnosis and treatment of complex dysrhythmias. The purpose of this review is to familiarize anaesthetists with these procedures. The information presented combines a literature review with the authors' experience. This article reviews normal cardiac conduction, tachycardia pathogenesis, principles of cardiac EP study and techniques of conduction pathway ablation. The anaesthetic considerations, including the choice of anaesthetic agent, monitoring problems, drug interactions, special methods of dysrhythmia termination in the EP lab, and complications specific to these procedures, are detailed. Balanced general anaesthesia or monitored anaesthesia care (MAC) sedation with benzodiazepines, propofol and narcotics are acceptable. Several conclusions can be drawn: transcatheter ablation is an effective treatment for many reentry tachycardias; anaesthetic assistance for this procedure will increasingly be needed; anaesthesia can easily be provided without influencing accurate EP testing; overdrive pacing is the method of choice for terminating tachydysrhythmias in the EP lab.