Effect of Intravenous Sodium Pentobarbital on Pain and Sensory Abnormalities in Patients with Chronic Non-Cancer Pain: Narrative Literature Review, Research Study, and Illustrative Case Reports.

INTRODUCTION

Sodium pentobarbital (SP), a short- to intermediate-acting barbiturate, has limited information in the existing literature. The objectives of this study are to describe (a) the effect of intravenous (IV) SP infusion on pain and sensory abnormalities, and (b) its utility in the diagnosis and management of patients with chronic pain.

METHODS

A narrative review of barbiturate applications for chronic pain was followed by a pragmatic study of 176 consecutive patients admitted to an inpatient pain unit (2004-2009). We collected demographic information upon admission, diagnoses retrieved from chart review, and pain ratings and sensory abnormalities at baseline and after blinded infusion of normal saline (NS) followed by SP.

RESULTS

The study group consisted of 83 men and 93 women (mean age 41 ± 11 years); the mean NS dose was 7.8 ± 2.3 (range 2-10 ml), the SP dose was 223.8 ± 88 mg (range 40-420), and the numeric rating scale (NRS) baseline pain score was 6.0 ± 2. The mean reduction in NRS reached both statistical and clinical significance in 150 responders to either NS/SP or SP only. Collectively, we found (a) an extremely high rate of response to IV SP irrespective of the underlying pathology, (b) greater response for pain than for sensory abnormalities (sensory gains or deficits), (c) greater response for sensory gain than for sensory deficit, and (d) greater response for allodynia than for pinprick hyperalgesia. Illustrative case reports are also presented.

DISCUSSION

IV SP infusion is a diagnostic tool that assists in elucidating pain generators and the nature of sensory abnormalities (central vs. peripheral), with effects similar to those of IV sodium amytal. The test cannot be viewed as a tell-all diagnostic modality and must be used in conjunction with clinical judgment, investigations, and psychological reports.