The Gut Microbiota and Chronic Pain

PURPOSE OF REVIEW

To examine the effects and interactions between gut microbia and chronic pain.

RECENT FINDINGS

The gut microbiome has been an area of interest in both the scientific and general audience due to a growing body of evidence suggesting its influence in a variety of health and disease states. Communication between the central nervous system (CNS) and gut microbiome is said to be bidirectional, in what is referred to as the gut-brain axis. Chronic pain is a prevalent costly personal and public health burden and so, there is a vested interest in devising safe and efficacious treatments. Numerous studies, many of which are animal studies, have been conducted to examine the gut microbiome's role in the pathophysiology of chronic pain states, such as neuropathy, inflammation, visceral pain, etc. As the understanding of this relationship grows, so does the potential for therapeutic targeting of the gut microbiome in chronic pain.

Autonomic Nerve Blocks

Chronic pain disorders present with different etiologies and consequently their signals are carried by different classifications of nerve fibers. Syndromes and disorders that present with sympathetically based pain are therefore treated differently than those with more musculoskeletal based etiologies. Autonomic nerve blockade primarily targeting sympathetic nerve ganglia can be used to provide significant pain relief in certain chronic pain disorders, most notably complex regional pain syndrome. Commonly targeted sympathetic ganglia include the stellate, celiac, and lumbar sympathetic chains. The purpose of this chapter is to provide recommendations on how to best perform these blocks as well as describe their indications, possible complications, and relevant surrounding anatomy.

Peripheral Nerve Blocks (Head)

Regional anesthesia for procedures involving the head can be easily achieved through the careful application of peripheral nerve blockade. Because the head has predictable surface and bony landmarks, the blocks can easily be placed pre- and intraoperatively to provide both regional anesthesia and postoperative analgesia with minimal complications. The peripheral blockade of nerves involving the head can provide perioperative anesthesia as well as management of both perioperative pain and chronic pain. The purpose of this chapter is to provide information and recommendations on how to best perform these blocks as well as describe their indications, complications, and relevant surrounding anatomy.

Peripheral Nerve Blocks (Neck)

To facilitate awake endotracheal intubation, a blockade of the glossopharyngeal, superior laryngeal, and recurrent laryngeal nerves can be utilized. The peripheral blockade of nerves in the neck is most often used to facilitate awake endotracheal intubation for the patient with a difficult airway. Although topicalization with minimal-to-moderate sedation is often sufficient to perform an awake intubation, one should be knowledgeable of all the alternative methods should the need arise. This chapter focuses on the indications, relevant anatomy, and complications of these blocks. Also described is blockade of the cervical plexus, which is useful in facilitating surgery on more superficial neck structures.

The efficacy and safety of once-daily nifedipine: the coat-core formulation compared with the gastrointestinal therapeutic system formulation in patients with mild-to-moderate diastolic hypertension. Nifedipine Study Group

The efficacy and safety of two sustained-release formulations of nifedipine, the coat-core system (NIF CC) and the gastrointestinal therapeutic system (NIF GITS), were examined in 228 patients with mild-to-moderate essential hypertension in this 16-week, multicenter, randomized, double-blind study. The coadministration of food affects the nifedipine pharmacokinetics with differing magnitudes for the two formulations. To evaluate drug safety under the most rigorous circumstances, all medication was given with food. After a 4-week placebo lead-in period, eligible patients were randomized to a parallel-group treatment period of either NIF CC or NIF GITS. 30 mg daily with food for 4 weeks, followed by forced titration to nifedipine 60 mg daily for an additional 4 weeks. For the final 4-week period, half of the patients receiving each formulation were switched to the alternate formulation at a dose of 60 mg daily. Within treatment groups, all four blood pressure variables (systolic and diastolic measurements for both trough and 24-hour periods) demonstrated significant reductions (P < 0.05) from baseline (established after the placebo lead-in period) for both formulations at every subsequent visit and end point. When comparing the two formulations, the mean change from baseline in 24-hour systolic and diastolic blood pressure measurements, determined by using ambulatory monitoring, was not statistically different for both doses (P > 0.05). The mean change in trough blood pressure from baseline during the parallel-group treatment period was statistically significant in favor of NIF GITS for both the 30-mg and 60-mg doses (P < 0.05). The treatment-emergent adverse-event rates for both formulations were similar during the parallel-group period, with the exception of dizziness, which was higher for patients receiving NIF CC. Both formulations were well tolerated and reduced blood pressure over the 24-hour dosing interval even when coadministered with food. When half of the patients receiving NIF GITS 60 mg daily were randomly crossed over to NIF CC 60 mg daily, there were no significant changes in either the trough or 24-hour mean blood pressure measurements (P > 0.05), adverse events, or dropout rates. When patients receiving NIF CC 60 mg were crossed over to NIF GITS 60 mg daily, they exhibited no significant change in diastolic blood pressure (P > 0.05). This study demonstrated that when given with food, both NIF CC and NIF GITS reduce 24-hour mean blood pressure measurements similarly.(ABSTRACT TRUNCATED AT 400 WORDS)