We decided to focus our review on the chronic form of singultus, for intractable hiccups are understood as an independent pathology that differs from the acute form in both pathophysiology and mechanisms of generation. Whereas an acute bout of hiccups is generated by a specific afferent impulse leading to an activation of the reflex arc and subsequently limited by the elimination of the trigger, chronic hiccups are characterized by a repeated or continuous overstimulation of the mechanism that may persist independently from a possible causative factor. However, chronic activation of the reflex does not necessarily develop from the acute as caused by a definite incentive event but rather due to a gradual process of irritation. If a stimulus threshold within the reflex arc is exceeded, then the clinical picture of intractable singultus emerges.
We agree that acute hiccups are of greater clinical relevance to the anesthesiologist. Thus, review of the existing literature reveals a multitude of investigations on the therapy of singultus developing during induction or maintenance of general anesthesia. In our experience, instillation of cold substances, eg, lidocaine or ethyl chloride spray into the nostrils, leads to quick alleviation of the symptom.2,3 The fact that the nasal application of ice cold water was equally effective in a study by Ravindran4 suggests a primarily physical effect of this therapeutic strategy. Likewise, a ventilation maneuver similar to pulmonary recruitment as described by Baraka5 seems to be beneficial; in the conscious patient, administration of continuous airway pressure using high-pressure levels (25–30 cm H2O for 5–15 seconds) has also been reported as an effective means to terminate acute hiccups in the perioperative setting.6 We were also able to achieve sufficient results with the method suggested by Orlovich et al, although a risk of oronasopharyngeal injury with conjoined bleeding especially in anticoagulated patients has to be considered.
To us it would be of great interest to investigate transition from acute to chronic singultus with regard to the mechanisms promoting the chronification process. A better understanding of this sequence could be beneficial for a more specific treatment and the early prevention of hiccup chronification.