CO2 retention: The key to stopping hiccups

Preliminary experimental outcomes of induced hypercapnia in treatment of obstinate singultus

Background

Our team found that abolishing the venous-arterial CO₂ gradient can cease singultus (hiccups), in which the CO₂ pressure in blood reaches no less than 50 mmHg. In order to precisely investigate the target level as a preliminary study, we made a combination gas consisting of 10% CO₂ and 90% O₂ to generate the conditions instantly and safely.

Methods

Thirty-five cases consisting of 26 patients with long-term chronic singultus were treated using the gas. The group consisted of 21 males and 5 females with mean singultus duration of 8.0±13.1 years. A standard oxygen mask was used for delivery of the gas to the patients, and patients breathed in the gas until they felt relief. The duration of the procedure was measured from the beginning to the point at which singultus ceased. A blood test was performed to measure the partial pressure of CO₂ in venous blood at the point at which singultus ceased.

Results

Singultus ceased in all patients in a mean time of 5.3±1.5 minutes, with complete recurrence observed in two cases. The mean partial pressure of CO₂ in the venous blood at the point the singultus stopped was 60.8±6.8 mmHg. No life-threatening complications were found in any patient.

Conclusions

One of the definitive conditions for ceasing singultus is acute CO₂ retention in the body, the target of which is around 60 mmHg of CO₂ in venous blood. We believe that targeting acute hypercapnia can always stop singultus, although further neuroscientific investigation is necessary to reveal the physiological mechanism.

Chronic Hiccups

PURPOSE OF REVIEW

Nearly 4000 patients will be admitted to hospital in the US this year for hiccups. Hiccups are controlled by a complex reflex arc between peripheral receptors and the brainstem. Any disruption along this pathway may produce hiccups. Typically, hiccups resolve spontaneously but in certain pathologies symptoms may persist. Persistent hiccups may be considered a sign of underlying pathology. The most common cause involves GERD.

RECENT FINDINGS

Based on etiologies, studies have shown that first-line therapy should use a proton pump inhibitor (PPI) and involve appropriate gastrointestinal consultation. If symptoms persist, other etiologies such as central causes need to be explored.

SUMMARY

We review the pathophysiology of hiccups including multiple causes and the appropriate work up for each. We review several studies examining new treatments, both pharmacological and interventional, that may help patients. Initial therapy should still involve a PPI but several new therapies may be beneficial.

Intraoperative Laryngeal Mask Airway-Related Hiccup: An Overview

Hiccup is an involuntary contraction of the diaphragm and intercostal muscles resulting in sudden inspiration and closure of the glottis. The presence of hiccup in the perioperative period can be a challenging problem. Sudden movements of the patient from hiccups can interfere preoperative diagnostic procedures, intraoperative hiccup may delay the beginning of surgery, interfere with the surgical process, and affect intraoperative monitoring, and postoperative hiccup may affect would healing and hemodynamic stability. Hiccup can lead to have increased aspiration risk. Hiccup are is an incompletely understood phenomenon with multiple etiologies. Intraoperative hiccup related to laryngeal mask airway placement has been reported, and it presents unique challenges in diagnosis and management. Both pharmacological and non-pharmacological interventions have been utilized with various level of success. All treatment strategies are primarily aimed at interrupting the hiccup reflex arc.

Medullar impairment resolves hiccups

Background

In a previous article we reported the time that hiccups stop as the instant when CO₂ levels in both expiratory gas (EtCO₂) and inspiratory gas (InspCO₂) reach approximately 50 mmHg. To support our findings, in this article we aim to clarify the precise values of the CO₂ level in arterial blood (PaCO₂) and venous blood (PvCO₂) during plastic bag rebreathing.

Methods

A healthy male volunteer was asked to perform a rebreathing experiment using a 20 L air-filled plastic bag. During the experiment, his blood oxygen saturation level (SpO₂), EtCO₂ and InspCO₂ were measured until the volunteer gave up. PaCO₂ and PvCO₂ were measured at the following four points: P₀, when the rebreathing started; P₁, when both EtCO₂ and InspCO₂ indicated the same value; P₂, when both reached 50 mmHg; and P₃, when SpO₂ dropped to 90%.

Results

InspCO₂ increased from the beginning and showed the same value as EtCO₂ at P₁. PaCO₂ at P₁ was almost the same value as both InspCO₂ and EtCO₂. After P₁, InspCO₂, EtCO₂ and PaCO₂ increased at the same rate, and at P₂, they reached the level of PvCO₂. After P₂, all four markers continued to show the same value as they gradually increased.

Conclusions

Creating conditions inside the body in which PaCO₂ increases to the same level as PvCO₂ will stop hiccups consistently. Although other physiological pathways to stop hiccups may exist, for a successful outcome it is important that the balance of power between the cerebellum and the medulla is drastically altered.