General anesthetics (Adverse effects)

Post-operative nausea and vomiting is a common port-operative complication in a surgical and anesthetic environment, affecting 25 - 30% of the low risk patients and up to 70 - 80% of the high risk patients. In addition to the discomfort that it generates in the patients, it determines a greater post-operative morbility from hydroelectrolytic alterations and bronchial aspiration risk. Likewise, a Valsalva phenomeon increases the tension on the line of sutures, favoring hematoma formation and dehiscence.

On the other hand, the rise generated by health care costs is also important since 76 - 78% of outpatients consider nausea and vomiting, respectively, an important post-operatory factor to be eliminated.

There are few studies that show the association of risk factors separate from post-operative nausea and vomiting episodes; however, among the most named are gender, being a smoker, kinetosis (motion sickness), type and length of the surgery, anesthesia drugs used and pre- and post-operatory pain treatment.

Anatomic and physiologic aspects and definitions:

Although they are frequently present at the same time, nausea, retching and vomiting are not synonyms:

  • Nausea: subjective sensation, unpleasant, wavelike sensation experienced in the back of the throat and/or the epigastrium that may culminate in vomiting (emesis)
  • Retching: rhythmic contraction of the respiratory muscles, including the diaphragm and abdominal muscles without the expulsion of gastric content
  • Vomiting: forced expulsion of the gastric contents through the mouth

The act of vomiting is controlled by the vomiting center of the brain located in the reticular formation of the spinal cord; this center receives the afferent stimulus from the superior cortical centers, the optic, olfactory, vagus and glossopharyngeal nerves as well as from the somatic structures, the gastrointestinal tract, the mediastinum, testicles, pharynx and heart. The efferent impulses form the vomiting center travel via the vagus, phrenic and spinal nerves to the abdominal muscles.

The richly vascularized chemoreceptor zone, located in the area postrema is another important source of afferent stimuli that crossed the blood-brain barrier, making it vulnerable to be activated by direct chemical stimulation through the cerebrospinal fluid or the blood.

The vomiting process starts with a deep inhalation, anti- peristaltic movements and increased salivation. The glottis closes to protect the airways and the gastro-esophagus sphincter relaxes, the muscles of the thorax and abdominal wall contract, the diaphragm descends, increasing the intra-abdominal pressure and the gastric contents are expulsed to the esophagus and out through the mouth.

Currently, more than 40 neurotransmitters implicated in the act of vomiting are recognized. The central structures involved in this process are rich in dopaminergic, histaminergic, serotonergic, muscarinic and opiate receptors that antiemetic drugs will inhibit.

Gene or region studied

  • ANKK1
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