Successful termination of persistent hiccups via combined ultrasound and nerve stimulator-guided singular phrenic nerve block: a case report and literature review

Abstract

Persistent hiccups that occur after abdominal surgery seriously affect postoperative rehabilitation. Phrenic nerve block therapy has been recommended after failure of medication or physical maneuvers. However, the phrenic nerve is often difficult to accurately identify because of its small diameter and anatomic variations. We combined ultrasound with the use of a nerve stimulator to quickly and accurately identify and block the phrenic nerve in a patient with postoperative persistent hiccups. The ongoing hiccups were immediately terminated with no adverse effects. The patient reported no recurrence during the 2-week follow-up period. We conclude that the combined use of real-time ultrasound guidance and a nerve stimulator for singular phrenic nerve block might be an effective intervention for terminating postoperative persistent hiccups, although further studies are needed to evaluate the safety and efficacy of this technique. The findings in this case suggest a potential clinical application for this technique in managing persistent hiccups, thereby contributing to improved patient care and outcomes.

Introduction

Hiccups are not rare in the clinical setting. Any type of stimulation to the diaphragm or phrenic nerve may cause persistent hiccups, which can adversely affect patients’ daily life or postoperative rehabilitation. Hiccups can sometimes be managed with medications, physical maneuvers, or traditional Chinese acupuncture treatment. ¹ If these treatments are ineffective, phrenic nerve block may be attempted in some cases. ² However, the phrenic nerve is often difficult to accurately identify because of its small diameter and anatomic variations. The use of ultrasound alone to localize the phrenic nerve is challenging and time-consuming, and blocking this nerve requires large volumes of local anesthetic. This can lead to various complications, including unexpected brachial plexus blockade, resulting in unnecessary harm and discomfort to the patient. We herein present a case of successful termination of postoperative persistent hiccups via singular phrenic nerve block that was accurately guided by the combined use of ultrasound and a peripheral nerve stimulator with no complications or recurrence.

Case description

This study was approved by the Tongji Hospital Ethics Committee (TJ-IRB20220927), and written consent was obtained from the patient. This manuscript adheres to the CARE guidelines. ³ We obtained the patient’s consent for treatment and have deidentified all patient details. We are committed to promoting transparency and reproducibility in research. All underlying research materials, including data, samples, and models, are available upon request.

A man in his early 50s developed persistent hiccups after laparoscopic total gastrectomy and right hemicolectomy. The persistent hiccups occurred at a frequency of 10 to 20 per minute, thus seriously affecting his daily activities, including eating and sleeping. Postoperative computed tomography (CT) showed localized abdominal effusion and a small amount of gas in front of the duodenum and pancreas. During the subsequent 2 weeks, the patient received medical therapies including chlorpromazine and diazepam, but these were ineffective. He also underwent physical maneuvers and acupuncture, but his hiccups remained unchanged. On postoperative day 14, the pain clinic was consulted and a phrenic nerve block was arranged. The block was performed using combined guidance provided by ultrasound and a nerve stimulator. Because the postoperative abdominal CT scan showed a small amount of effusion under the right diaphragm, we chose to block the right phrenic nerve. The patient was informed of possible discomfort caused by the nerve stimulator before the procedure began.

The patient lay in the supine position with his upper body elevated to 30° and his head turned to the left. During the procedure, the patient’s noninvasive blood pressure, oxygen saturation (SpO₂), and electrocardiogram were monitored. A high-frequency ultrasound probe (model SL2325; Esaote S.p.A., Florence, Italy) was placed on the lateral neck approximately 3 cm above the clavicle to initially display the anterior scalene muscle, the middle scalene muscle, and brachial plexus in the interscalene space. Under ultrasound, the phrenic nerve appeared as a tiny black dot that traveled medially and inferiorly over the surface of the anterior scalene muscle, underneath the sternocleidomastoid muscle, as shown in Figure 1 and Supplementary Video 1. A 22G, 5-cm-long insulated needle (Stimuplex® D; B. Braun, Melsungen, Germany) was inserted through the sternocleidomastoid muscle and advanced directly toward the tiny dot that was suspected be the phrenic nerve using an in-plane approach.

Figure 1.

Ultrasonographic image displaying the approach of a needle toward a small, dot-like, suspected phrenic nerve situated in the space between the sternocleidomastoid muscle and the anterior scalene muscle. The arrow indicates the tiny dot, later confirmed by a nerve stimulator to be the phrenic nerve. The arrowheads indicate the blockade needle PN, phrenic nerve; ASM, anterior scalene muscle; MSM, middle scalene muscle; SCM, sternocleidomastoid muscle; BP, brachial plexus; IJV, internal jugular vein.

The parameters of the nerve stimulator (Stimuplex® HNS 12; B. Braun) were initially set at 1 mA and 2 Hz, and the current was then slowly decreased to 0.3 mA as the needle tip approached the tiny dot. The phrenic nerve was confirmed when rhythmic contractions were observed in the right upper abdomen in response to the nerve stimulator, as demonstrated in Supplementary Video 2. Next, 3 mL of 0.3% ropivacaine was injected around the nerve. The diaphragm muscle immediately stopped twitching after the injection despite the increasing electrical current stimulation. The whole procedure took approximately 5 minutes.

The ongoing hiccups were terminated after the phrenic nerve block. The rate and amplitude of breathing and the SpO₂ were continuously monitored for 1 hour after the block. The SpO₂ slightly decreased from 96% to 94% 10 minutes after the nerve block procedure, then gradually recovered to 96% after 30 minutes without oxygen supplementation. The patient then returned to the ward after a 1-hour stay in the post-anesthesia care unit. He exhibited no respiratory depression or any signs of brachial plexus block. The patient was thereafter able to rest well, sleep well, and participate in postoperative rehabilitation, and he expressed satisfaction with the treatment. During the 2-week follow-up, he reported no recurrence of the hiccups or adverse events related to the phrenic nerve block.

Discussion

In this case, we combined real-time ultrasound guidance with a nerve stimulator to quickly and accurately identify and block the phrenic nerve. This resulted in immediate termination of the ongoing hiccups with no recurrence. This combination technique allows for precise blockade of the tiny phrenic nerve with a small volume of local anesthetic, effectively halting persistent hiccups with no adverse effects. To our knowledge, this is the report to describe this combination technique for phrenic nerve block.

A hiccup is a sudden, involuntary spasm of the diaphragm and intercostal muscles followed by rapid closing of the glottis. ⁴ Hiccups are classified based on their duration. Persistent hiccups are defined as hiccups that persist from 48 hours to 1 month, whereas intractable hiccups last for longer than 1 month. ⁵ Persistent or intractable hiccups are sometimes symptomatic of an underlying disease or injury involving the hiccup reflex arc. This reflex arc includes afferent connections through the vagus, phrenic, and sympathetic nerves, which send signals to the hiccup center located in the midbrain or brainstem. Efferent pathways, specifically those involving the phrenic nerve, then innervate the diaphragm, triggering the hiccup reflex. ⁶ Hiccups can arise from various causes, including continuous irritation off the phrenic nerve or diaphragm due to mediastinal or abdominal inflammation, tumors, ascites, or chemotherapy. Additionally, hiccups can also result from central causes such as stroke, brain tumors, trauma, or multiple sclerosis. ⁷ It is necessary to identify and treat the underlying disease; during this process, symptoms should be controlled because of their negative effects on daily life.

Most hiccups are self-limited. ⁸ However, various modalities and therapies, such as medications (baclofen, chlorpromazine, olanzapine, and promethazine) and physical maneuvers (including breath-holding and induction of emesis), as well as more invasive therapy, have been reported to treat persistent hiccups, each with varying degrees of effectiveness.^9,10 Among these various techniques, ultrasound-guided phrenic nerve blockade usually produces immediate and noticeable results, although a relatively large volume of anesthetic or continuous block through a catheter has been used in several case reports.^11,12

In our case, the patient did not respond to pharmacologic therapies, physical maneuvers, or traditional Chinese acupuncture. His postoperative abdominal CT scan revealed a small fluid collection under the right diaphragm. The surgical injury of his previous gastric procedure or the subdiaphragmatic fluid collection might have been the cause of his persistent hiccups. Therefore, subphrenic drainage was established to remove the fluid collection and thus remove this possible source of irritation to the diaphragm. Furthermore, the right side of the phrenic nerve was blocked to interrupt the pathway of the pathological stimulation.

Ultrasound guidance has recently gained considerable popularity as a commonly used method to guide various nerve blocks during medical procedures. One notable benefit of this technique, apart from being free from ionizing radiation and having no site-specific limitations, is its ability to provide real-time visualization of all three essential components throughout the nerve blocking procedure: the target nerve, the needle, and the local anesthetic. Nevertheless, the current limitations in image resolution make it challenging for ultrasound technology to precisely identify certain small nerves, such as the phrenic nerve, which was found to be monofascicular with an average diameter of merely 0.76 mm in a study involving 23 volunteers. ¹³

Numerous important anatomical structures surround the cervical segment of the phrenic nerve. It is crucial to ensure accurate blocking and avoid using excessive volumes of anesthetic to prevent unintended side effects. If local anesthetics flow into the interscalene space, the brachial plexus may be blocked, leading to unexpected sensory and motor loss in the upper limbs. The presence of Horner’s syndrome indicates sympathetic blockade. Furthermore, blocking the recurrent laryngeal nerve may cause voice changes and potential airway obstruction, whereas blocking the main vagus nerve can result in tachycardia. ¹⁴ Therefore, we recommend utilizing a nerve stimulator as an additional verification method when performing blocks for small-diameter nerves such as the phrenic nerve. Our strategy involves using high-frequency ultrasound to quickly locate the space between the anterior scalene muscle and the sternocleidomastoid muscle at the C6 or C7 level. The space is then searched for a small dot, which is presumed to be the phrenic nerve. A needle is inserted and advanced toward this target dot, and current stimulation is applied to confirm the identity of the phrenic nerve through synchronous contraction of the diaphragm.

The application of phrenic nerve block is not widely practiced, and there is a lack of strong evidence with reliable data to determine the minimum effective concentration and dosage. Most of the available literature consists of individual case reports, some of which have used 0.2% ropivacaine ¹⁵ and others of which have used 0.4%. ¹¹ Therefore, based on a combination of our previous clinical experience of blocking smaller peripheral nerves and the existing literature, we chose an intermediate value of 0.3%. Well-designed clinical research studies are necessary to establish the optimal effective concentration of ropivacaine for phrenic nerve block.

The application of this combination guidance technique can reduce the total amount of local anesthetic used, improve accuracy, minimize damage to surrounding tissues and vital organs, and reduce puncture-related complications. The phrenic nerve is often difficult to directly locate because of the fine nature of the nerve, the relatively low resolution of ultrasound, and the presence of many surrounding structures with a similar appearance on ultrasound. Instead, the nerve is usually recognized by tracking its trajectory in the expected location. Hence, ultrasound may require a longer pre-scanning time and necessitate a larger dose of local anesthesia than a combined technique.

A nerve stimulator serves as an objective verification tool for the effectiveness of the block. Even with the application of a high current after a successful block, there will be no induced contraction of the corresponding diaphragm muscle. Evidence of diaphragmatic paralysis also can be confirmed using M-mode ultrasonography ¹⁶ or evaluated by fluoroscopy. ¹⁴

In conclusion, the combined use of real-time ultrasound guidance and a nerve stimulator for singular phrenic nerve block might be an effective intervention for terminating postoperative persistent hiccups, although further studies are needed to evaluate its safety and efficacy.

Data availability statement

The data that support the findings of this study are available upon reasonable request from the corresponding author (Dr. Hua Zheng: hzheng@hust.edu.cn).