Approach to the patient with metabolic acidosis: Newer concepts

Summary: A new classification for patients with metabolic acidosis is provided: a pathophysiological classification. to recognize an overproduction of acids which results in a hydrogen ion (H⁺) gain the number of new anions retained in the body is added to those excreted in the urine when the cation accompanying them was not H⁺ or ammonium (NH₄⁺). the first tools are to recognize new anions that were added during the overproduction of acids. the nature of these anions can be recognized by assessing their fractional excretion. the second set of tools focuses on an assessment of NH₄⁺ in the urine using urine anion and osmolar gaps. the clinical approach suggested focuses on detecting an emergency (severity of H⁺ accumulation, toxic alcohols and/or dyskalaemias). the second step analyzes the expected responses to acidaemia; here the focus is on the P_CO2 in vital organs and the rate of excretion of ammonium. the principles used for diagnosis and treatment of metabolic acidosis are illustrated by a case example.     

The neuroendocrine challenge paradigm in headache research

The neuroendocrine challenge paradigm provides a "window" on central neurotransmitter function in vivo. This strategy is based on the premise that the sensitivity of certain central receptors can be inferred from the magnitude of the hormonal response to specific pharmacologic probes. For example, the serotonin (5HT) receptor agonist m-chlorophenylpiperazine (m-CPP) stimulates the release of cortisol and prolactin and induces migraine-like headaches. We have previously reported that the headache and cortisol responses to m-CPP are highly correlated, which may implicate a disturbance in central serotonergic neurotransmission in the pathogenesis of migraine. As pharmacologic probes with greater specificity for 5HT receptor subtypes become available, we may be able to elucidate these mechanisms with greater precision. The neuroendocrine challenge methodology is also applicable to the study of other neurotransmitter systems and other headache disorders.