Standardizing Postoperative Complications—Validating the Clavien-Dindo Complications Classification in Cardiac Surgery

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Transfer across the human blood-brain barrier: Evidence for capillary recruitment and for a paradox glucose permeability increase in hypocapnia

The present study was undertaken to investigate whether there is intermittency of capillary flow in the human brain, i.e., whether more capillaries open up at high blood flow thus increasing the surface for diffusional exchange. Unidirectional transfer across the blood-brain barrier of labeled D-glucose, l-phenylalanine, l-leucine, thiourea, and propranolol was measured using the indicator diffusion method with labeled Na⁺, Cl^?, and chelated In as impermeable reference substances. Forty-three patients needing carotid angiography were studied in different situations, rest, hyperventilation, hypercapnia, hypo/hypertension (within the limits of autoregulation). Some older data on the seizure situation are included. Cerebral blood flow (CBF) was measured concomitantly. In situations with high blood flow, extraction (E) decreased and the permeability surface area product (PS) increased for both the lipophilic substances and for those transferred by carrier mechanism. With low CBF the reverse happened except for an unexpected PS increase for glucose in hyperventilation. Variations of PS in parallel with CBF are evidence of capillary recruitment which constitutes a more efficient way of increasing tissue supply. PS and E remained constant with a constant CBF even when arterial blood pressure was changed, indicating that autoregulatory mechanisms do not affect the diffusional exchange surface and probably take place at the arteriolar level. PS for glucose increased in hyperventilation perhaps as an expression of a pH dependence of its carrier.     

Characteristics of recovery of adrenocortical function after treatment for Cushing's syndrome due to pituitary or adrenal adenomas

OBJECTIVE: Surgical cure of Cushing's syndrome (CS) is followed by adrenocortical insufficiency, which may be long-lasting. The aim was to elucidate recovery of adrenocortical function, defined as a normal cortisol response to ACTH stimulation, and the relation to ACTH in patients cured for CS due to pituitary Cushing's disease (CD) or adrenal (AA) adenomas. DESIGN: A retrospective study including 32 patients considered surgically cured for CS (18 CD, 14 AA). RESULTS: Twelve (67%) patients with CD recovered within median 24 months (range 7 months-4(1)/(2) years) whereas six did not recover within 3-12 years. Plasma ACTH (p-ACTH) at time of recovery was not different from p-ACTH in patients not recovering (P = 0.9). Eleven (79%) patients with AA recovered within 24 months (10 months-4 years) whereas three did not recover within 4-10 years. p-ACTH at time of recovery was higher compared to patients not recovering (P < 0.04). No differences were observed comparing CD and AA patients concerning preoperative 24-h urinary free cortisol (UFC) excretion, postoperative unstimulated s-cortisol or recovery time. By contrast, p-ACTH measured at time of recovery was higher in AA compared to CD (median 12.3 vs. 4.6 pmol/l) (P < 0.001), whereas plasma dehydroepiandrosterone sulfate (p-DHEAS) was lower in AA compared to CD (median 300 vs. 1500 nmol/l) (P = 0.02). CONCLUSION: Recovery of secondary adrenal insufficiency is a slow process in both CD and AA. ACTH measured at time of recovery was significantly higher and DHEAS significantly lower in patients with AA compared to CD, which may suggest different mechanisms of the recovery process and different set points in the glucocorticoid feedback inhibition of ACTH secretion.