Effects of metoclopramide and tropisetron on aldosterone secretion possibly due to agonism and antagonism at the 5-HT4 receptor

Effect of naloxone on intravenous fentanyl patient-controlled analgesia after laparoscopic cholecystectomy

This study aims to evaluate the effect of naloxone on intravenous fentanyl patient-controlled analgesia after laparoscopic cholecystectomy under total intravenous anesthesia.A total of 90 patients, who underwent intravenous fentanyl patient-controlled analgesia after laparoscopic cholecystectomy under total intravenous anesthesia, were included into this study. All patients were randomly divided into 3 groups (each group, n=30): naloxone group (naloxone+fentanyl), tropisetron group (tropisetron+fentanyl), and fentanyl group (fentanyl). Patients in each group were given a corresponding dose of naloxone. Postoperative analgesia effect and the incidence of side effects such as nausea and vomiting were observed.Small doses of naloxone or tropisetron combined with fentanyl used for intravenous patient-controlled analgesia can significantly reduce the incidence of nausea and vomiting. Six hours after surgery, visual analogue scale (VAS) scores were significantly lower in patients that underwent intravenous patient-controlled analgesia using low-dose naloxone combined with fentanyl compared with patients who received fentanyl alone; however, the postoperative analgesic effect of tropisetron was not observed. Compared with the combination of tropisetron and fentanyl, low-dose naloxone combined with fentanyl can obviously reduce the incidence of nausea and vomiting in patients who underwent intravenous patient-controlled analgesia after laparoscopic cholecystectomy, and enhance the analgesic effect of fentanyl 6 hours after surgery.Low-dose naloxone can reduce the incidence of nausea and vomiting in patients who underwent laparoscopic cholecystectomy under total intravenous anesthesia, and exhibits a certain synergic analgesic effect.

5-Hydroxytryptamine receptors in the human cardiovascular system

The human cardiovascular system is exposed to plasma 5-hydroxytryptamine (5-HT, serotonin), usually released from platelets. 5-HT can produce harmful acute and chronic effects. The acute cardiac effects of 5-HT consist of tachycardia (preceded on occasion by a brief reflex bradycardia), increased atrial contractility and production of atrial arrhythmias. Acute inotropic, lusitropic and arrhythmic effects of 5-HT on human ventricle become conspicuous after inhibition of phosphodiesterase (PDE) activity. Human cardiostimulation is mediated through 5-HT4 receptors. Atrial and ventricular PDE3 activity exerts a protective role against potentially harmful cardiostimulation. Chronic exposure to high levels of 5-HT (from metastatic carcinoid tumours), the anorectic drug fenfluramine and its metabolites, as well as the ecstasy drug 3,4-methylenedioxymethamphetamine (MDMA) and its metabolite 3,4-methylenedioxyamphetamine (MDA) are associated with proliferative disease and thickening of cardiac valves, mediated through 5-HT2B receptors. 5-HT2B receptors have an obligatory physiological role in murine cardiac embryology but whether this happens in humans requires research. Congenital heart block (CHB) is, on occasion, associated with autoantibodies against 5-HT4 receptors. Acute vascular constriction by 5-HT is usually shared by 5-HT1B and 5-HT2A receptors, except in intracranial arteries which constrict only through 5-HT1B receptors. Both 5-HT1B and 5-HT2A receptors can mediate coronary artery spasm but only 5-HT1B receptors appear involved in coronary spasm of patients treated with triptans or with Prinzmetal angina. 5-HT2A receptors constrict the portal venous system including oesophageal collaterals in cirrhosis. Chronic exposure to 5-HT can contribute to pulmonary hypertension through activation of constrictor 5-HT1B receptors and proliferative 5-HT2B receptors, and possibly through direct intracellular effects.

Intra-arterial injection of metoclopramide, midazolam, propofol and pethidine

A case is reported in which metoclopramide, midazolam, propofol, and pethidine were injected arterially during the course of anaesthesia, resulting in oedema and discolouration of the hand initially, but no long-term sequelae. An AVI 470 pump (3M Corporation) was used to control the infusion, andprevented backflow through a cannula which was unintentionally sited in an artery rather than a vein. Few anaesthetic drugs have their effects well documented when given arterially, and in particular, there were no previous reported cases involving metoclopramide in this context. The pharmacology of metoclopramide is discussed with reference to the drug's known effects on vascular beds and platelet function.