Hiccups, medically known as singultus, are a common, transient physiological event. This phenomenon is defined by a sudden, involuntary spasm of the diaphragm and the intercostal muscles. This spasm is quickly followed by the abrupt closure of the glottis, the space between the vocal cords, producing the characteristic “hic” sound. While usually benign, hiccups occurring in the post-operative period are a recognized medical phenomenon that can complicate patient recovery.
How Common Are Post-Surgical Hiccups?
Post-surgical hiccups are not universal but are common enough to be considered a known side effect of the perioperative process. While the frequency is relatively low for general inpatients, the risk increases significantly for patients undergoing procedures that affect the thoracic or abdominal areas. Hiccups are classified based on their duration, which helps clinicians assess the potential for complications.
Most post-operative hiccups are considered transient, resolving on their own within 48 hours. This short duration suggests they are temporary irritations of the hiccup reflex arc rather than a sign of serious underlying disease. If episodes persist for longer than 48 hours but less than one month, they are termed persistent hiccups. Those lasting longer than a month are categorized as intractable, a rare condition requiring aggressive treatment.
Specific Causes Related to Surgery and Anesthesia
Post-operative hiccups arise from the irritation of the reflex arc that controls the diaphragm. This arc primarily involves the phrenic nerve, the vagus nerve, and the sympathetic nervous system. Since both surgery and anesthesia manipulate the body’s systems, they can easily trigger this reflex.
Anesthesia and Medications
General anesthesia and certain medications administered during and after surgery can directly or indirectly stimulate the hiccup reflex. Sedatives, muscle relaxers, and opioids, for instance, are known to interfere with the central nervous system’s inhibitory control over the hiccup arc. This interruption can lead to a temporary loss of regulation, allowing the reflex to fire erratically.
The use of certain steroids, such as dexamethasone, is also associated with triggering the hiccup reflex. Some anesthetic agents, like propofol, may cause hiccups upon induction, possibly by disturbing the balance of neurotransmitters in the brainstem. These pharmacological effects resolve quickly as the medications are metabolized by the body.
Surgical Irritation
Surgical manipulation is a direct physical trigger, particularly in procedures involving the chest or upper abdomen. Any surgical traction or direct irritation of organs near the diaphragm, such as the stomach or gallbladder, can stimulate the vagus nerve’s sensory fibers. The vagus nerve has extensive distribution, making it sensitive to disturbances in the surgical field.
Procedures that cause a collection of fluid or blood beneath the diaphragm (a subdiaphragmatic collection) can physically press on and irritate the phrenic nerve. The phrenic nerve is the main efferent pathway to the diaphragm, and its irritation directly leads to the uncontrolled spasms seen in hiccups. The presence of air or gas, such as from a pneumoperitoneum used in laparoscopic surgery, can also cause localized pressure on the diaphragm.
Gastric Distention and Reflux
Air trapped in the stomach or intestines following surgery is a common trigger for post-operative hiccups. This gastric distention stretches the stomach wall, which in turn stimulates the gastric branch of the vagus nerve. The sudden influx of air from intubation during surgery can also contribute to this distention, initiating the reflex.
Gastroesophageal reflux disease (GERD) or post-operative stomach acid backing up into the esophagus can also irritate the vagus nerve. The chemical irritation from stomach acid stimulates the afferent arm of the hiccup reflex arc, causing the diaphragm to contract. Addressing this underlying gastrointestinal irritation is often a successful way to stop persistent hiccups.
Treatment Methods and Identifying Complications
Management of post-operative hiccups is approached in a step-wise manner, starting with simple physical maneuvers before moving to pharmacological interventions if symptoms persist. Most transient cases can be resolved by techniques aimed at interrupting the reflex arc.
Management
Simple physical maneuvers are designed to over-stimulate the vagus nerve to reset the central hiccup processing unit. Techniques such as the Valsalva maneuver, which involves attempting to exhale forcefully against a closed airway, work by increasing the pressure within the chest cavity. This pressure change provides a strong stimulus to the vagus nerve. Similarly, sipping cold water or holding one’s breath can stimulate the vagus nerve directly, leading to cessation of the spasms.
If hiccups become persistent, pharmacological therapy may be necessary, targeting the neural pathways that regulate the reflex. Chlorpromazine, the only medication approved by the FDA specifically for intractable hiccups, acts as a dopamine receptor antagonist in the central nervous system. This action helps reduce the central nervous system hyperactivity that perpetuates the spasms.
Pharmacological Alternatives
Alternatives include baclofen, a muscle relaxant that reduces neuronal excitability and interrupts the reflex arc at the brainstem level. Gabapentin, an anti-convulsant that modulates calcium channels, is also used to calm the neural overactivity involved in the reflex.
When to Seek Help
While most post-operative hiccups are temporary, persistence beyond 48 hours warrants communication with the surgical team. Hiccups that continue for an extended period can lead to serious complications that interfere with the recovery process. The physical strain of continuous diaphragmatic spasms can lead to exhaustion, interrupt sleep, and cause difficulties with eating or drinking, potentially resulting in malnutrition and dehydration.
In patients who have undergone abdominal surgery, prolonged, forceful hiccups can increase intra-abdominal pressure. This elevation poses a risk to the healing surgical incision, potentially interfering with wound healing or leading to the separation of the wound edges. Any hiccup episode that is severe, interferes with breathing, or is accompanied by signs of infection (like fever or severe pain) requires immediate medical re-evaluation. This is necessary to rule out a more serious complication, such as a subdiaphragmatic abscess or other internal irritant.