Explosive Vomiting Associated with Proximal Colonic Distention during a Difficult Propofol-Assisted Colonoscopy

Figure 1

Sympathetic/parasympathetic neurocircuits of proximal and distal colon: DMN (dorsal motor nucleus), ENS (enteric nervous system), GN (ganglion nodosa), GVA (general visceral afferents), NTS (nucleus tractus solitarius), PSA (parasympathetic afferent), PSE (parasympathetic efferent), SA (sympathetic afferent), SE (sympathetic efferent), VA (vagal afferent), and VE (vagal efferent). Proximal colon: vagal efferent fibers (solid red line) travel from the DMN to the submucosal and muscular layers of the proximal colon where they synapse with the multiple neurons and interneurons of the enteric nervous system. Efferent vagal fibers have the two following components: the cholinergic pathway, which has a stimulating effect, and the nonadrenergic noncholinergic pathway, which is inhibitory to colonic motility and secretion. Vagal afferent fibers (dotted red line) originate from the proximal colonic wall and transmit impulses relating to physiological changes (i.e., stretching and distention) to the NTS after synapsing at the GN. The NTS has dense projections that connect to the DMN and area postrema (AP). Impulses from the NTS also projects to higher CNS nuclei for modulation and integration, which provides feedback to the NTS and DMN for stimulation and inhibition. Sympathetic efferent fibers (solid black line) originate from sympathetic nuclei in the thoracic (T5-T9) spinal cord and travel to the proximal colonic wall after synapsing at the celiac ganglion (CG). They induce inhibitory effects except for sphincters. Sympathetic afferent fibers (dotted black line) carry nociceptive information from the proximal colon. After synapsing in the dorsal horn of the spinal cord, they ascend via the spinothalamic tract to reach the NTS directly and via GVAs to reach higher CNS nuclei. Both sympathetic afferent fibers (dotted red line) and parasympathetic afferent fibers (dotted black line) transmit nociceptive impulses from the distal colon via the spinothalamic tract to join GVAs and reach the NTS and higher CNS nuclei. Modulated/integrated information provides feedback to the sympathetic and parasympathetic nuclei in the spinal cord. Distal Colon: parasympathetic efferent fibers (solid red line) originate from parasympathetic nuclei (S2-S4) and travel to the distal colon to induce stimulating effects except for sphincters. Sympathetic efferent fibers (solid black line) originate from sympathetic nuclei (L2-L5) and travel to the colonic wall after synapsing at the IMG to induce inhibitory effects except for sphincters.