Opioid Sparing General Venous Anesthesia With Magnesium Sulfate

Magnesium sulfate has been shown to be useful in many situations in medicine, such as eclampsia prevention and treatment, pulmonary hypertension, arterial pressure, asthma, cardiac arrhythmias and pheochromocytoma. Recently there has been a growing a big interest in this drug as an useful adjuvant in anesthesia, with analgesic and anesthetic sparing effect, antihyperalgesic property and potentialization of the neuromuscular blocker agent effect. On the other hand there has been a growing concern related to opioid administration, such as hyperalgesia, delayed return of intestinal function and the (still controversial) possibility of facilitating effect on tumor growth and metastases in cancer patients. This project is based on a previous randomized, double blind prospective trial (conducted by one of these authors and not yet published) comparing two groups of patients who received general intravenous total anesthesia with propofol in controlled target infusion. The surgical stress index is obtained by the interaction between the interval between heart beats and the amplitude of the photoplethysmography wave, whose algorithm generates a number related to the hemodynamic result of the increase of the sympathetic tone, which has shown to be the most sensitive resource in detecting the imbalance between the stimulus nociceptive and anti-nociception.