Using a double-blind, randomized, cross-over protocol, we studied the effect of a single dose of oral caffeine on plasma renin activity, catecholamines and cardiovascular control in nine healthy, young, non-coffee drinkers maintained in sodium balance throughout the study period. Caffeine (250 mg) or placebo was administered in a methylxanthine-free beverage to overnight-fasted supine subjects who had had no coffee, tea or cola in the previous three weeks. Caffeine increased plasma renin activity by 57 per cent, plasma norepinephrine by 75 per cent and plasma epinephrine by 207 per cent. Urinary normetanephrine and metanephrine were increased 52 per cent and 100 per cent respectively. Mean blood pressure rose 14/10 mm Hg one hour after caffeine ingestion. There was a slight fall and then a rise in heart rate. Plasma caffeine levels were usually maximal one hour after ingestion but there was considerable individual variation. A 20 per cent increase in respiratory rate correlated well with plasma caffeine levels. Under the conditions of study caffeine was a potent stimulator of plasma renin activity and adrenomedullary secretion. Whether habitual ingestion has similar effects remains to be determined.

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Object Same-level recurrent lumbar stenosis, pseudarthrosis, and adjacent-segment disease (ASD) are potential complications that can occur after index lumbar spine surgery, leading to significant discomfort and radicular pain. While numerous studies have demonstrated excellent results following index lumbar spine surgery in elderly patients (age > 65 years), the effectiveness of revision lumbar surgery in this cohort remains unclear. The aim of this study was to assess the long-term effectiveness of revision lumbar decompression and fusion in the treatment of symptomatic pseudarthrosis, ASD, and same-level recurrent stenosis, using validated patient-reported outcomes. Methods After a review of the institutional database, 69 patients who had undergone revision neural decompression and instrumented fusion for ASD (28 patients), pseudarthrosis (17 patients), or same-level recurrent stenosis (24 patients) were included in this study. Baseline and 2-year scores on the visual analog scale for leg pain (VAS-LP), VAS for back pain (VAS-BP), Oswestry Disability Index (ODI), and Zung Self-Rating Depression Scale (SDS) as well as the time to narcotic independence, time to return to baseline activity level, health state utility (EQ-5D, the EuroQol-5D health survey), and physical and mental component summary scores of the 12-Item Short-Form Health Survey (SF-12 PCS and MCS) were assessed. Results Compared with the preoperative status, VAS-BP was significantly improved 2 years after surgery for ASD (mean ± standard deviation 9 ± 2 vs 4.01 ± 2.56, p = 0.001), pseudarthrosis (7.41 ± 1 vs 5.52 ± 3.08, p = 0.02), and same-level recurrent stenosis (7 ± 2.00 vs 5.00 ± 2.34, p = 0.003). The 2-year ODI was also significantly improved after surgery for ASD (29 ± 9 vs 23.10 ± 10.18, p = 0.001), pseudarthrosis (28.47 ± 5.85 vs 24.41 ± 7.75, p = 0.001), and same-level recurrent stenosis (30.83 ± 5.28 vs 26.29 ± 4.10, p = 0.003). The Zung SDS score and SF-12 MCS did not change appreciably after surgery in any of the cohorts, with an overall mean 2-year change of 1.01 ± 5.32 (p = 0.46) and 2.02 ± 9.25 (p = 0.22), respectively. Conclusions Data in this study suggest that revision lumbar decompression and extension of fusion for symptomatic pseudarthrosis, ASD, and same-level recurrent stenosis provides improvement in low-back pain, disability, and quality of life and should be considered a viable treatment option for elderly patients with persistent or recurrent back and radicular pain. Mental health symptoms may be more refractory to revision surgery.

The roles of glycogenolysis and gluconeogenesis in sustaining glucose production during insulin-induced hypoglycemia were assessed in overnight-fasted conscious dogs. Insulin was infused intraportally for 3 h at 5 mU.kg-1.min-1 in five animals, and glycogenolysis and gluconeogenesis were measured by using a combination of tracer [( 3-3H]glucose and [U-14C]alanine) and hepatic arteriovenous difference techniques. In response to the elevated insulin level (263 +/- 39 microU/ml), plasma glucose level fell (41 +/- 3 mg/dl), and levels of the counterregulatory hormones glucagon, epinephrine, norepinephrine, and cortisol increased (91 +/- 29 to 271 +/- 55 pg/ml, 83 +/- 26 to 2356 +/- 632 pg/ml, 128 +/- 31 to 596 +/- 81 pg/ml, and 1.5 +/- 0.4 to 11.1 +/- 1.0 micrograms/dl, respectively; for all, P less than .05). Glucose production fell initially and then doubled (3.1 +/- 0.3 to 6.1 +/- 0.5 mg.kg-1.min-1; P less than .05) by 60 min. Net hepatic gluconeogenic precursor uptake increased approximately eightfold by the end of the hypoglycemic period. By the same time, the efficiency with which the liver converted the gluconeogenic precursors to glucose rose twofold. Five control experiments in which euglycemia was maintained by glucose infusion during insulin administration (5.0 mU.kg-1.min-1) provided baseline data. Glycogenolysis accounted for 69-88% of glucose production during the 1st h of hypoglycemia, whereas gluconeogenesis accounted for 48-88% of glucose production during the 3rd h of hypoglycemia. These data suggest that gluconeogenesis is the key process for the normal counterregulatory response to prolonged and marked hypoglycemia.