Naloxone in moderate dose does not aggravate chronic tension headache

Pain Experience and Tolerance of Awake In-Office Upper Airway Procedures: Influencing Factors

OBJECTIVES/HYPOTHESIS

Awake, unsedated in-office upper airway procedures are performed frequently and have high completion rates, yet less is known about the patients' pain experience and potentially influencing factors. It is also unclear if patients' pain experiences become worse with repeated procedures. We identified procedure- and patient-related factors that might influence procedural completion and pain scores.

STUDY DESIGN

Retrospective chart review.

METHODS

Pre-, intra-, and post-procedure pain scores were collected prospectively for awake unsedated upper airway procedures performed at a single institution over a 5-year period. Patient factors reviewed were demographics, body mass index, psychiatric and/or pain diagnosis, and related medications. Procedure factors reviewed were procedure type, route, side, and performance of the same procedure multiple times. Patients reported their pain level before, during, and after the procedure using a standard 0 to 10 scale. Maximum pain score change (PΔmax), or the difference between highest and lowest reported pain levels, was calculated. Descriptive and multivariate analyses were performed.

RESULTS

Procedure completion was 98.7% for 609 first time patients and 99.0% in 60 patients undergoing 292 repeat procedures. PΔmax did not covary with age, gender, or BMI. PΔmax covaried with pain and psychiatric conditions and associated medications. PΔmax was highest for injection medialization and lowest for tracheoscopy. PΔmax decreased over time for those undergoing multiple identical procedures.

CONCLUSIONS

Procedures were performed with a very high completion rate and low pain scores. Age, sex, and BMI did not affect pain experience. A combination of pain and psychiatric conditions did. Injection medialization had the highest PΔmax and tracheoscopy the lowest.

LEVEL OF EVIDENCE

4 Laryngoscope, 131:E1580-E1588, 2021.

Altered cardiovascular/pain regulatory relationships in chronic pain

In healthy individuals, there is an inverse relationship between resting blood pressure (BP) and pain sensitivity. This study examined possible dysregulation of this adaptive relation in chronic pain patients, and tested whether the extent of this dysregulation is a function of pain duration. Continuous resting BP's were assessed for 5 min after a 5-min rest period in 121 chronic benign pain patients. Unlike the inverse relationship observed previously in normals, mean resting diastolic. BPs during the assessment period were correlated positively with ratings of pain severity. A Pain Duration x Systolic BP interaction emerged (p < .05) such that the magnitude of the BP-pain relation was greatest in patients with the longest duration of pain, r(38) = .50, p < .001. A hypothesized progressive alteration in endogenous pain regulatory systems in chronic pain patients was supported. A possible role of endogenous opioid dysfunction in accounting for these alterations is discussed.

Naloxone increases pain induced by topical capsaicin in healthy human volunteers

Opioid receptors occur in locations of strategic importance within the central nervous system for modulation of pain. Is pain reduced by ongoing inhibition mediated by activation of these receptors? Experiments to date in which the opioid-receptor antagonist, naloxone, is administered during a painful event have yielded unclear results. Topically applied capsaicin can be used to induce tonic pain of moderate to severe intensity without tissue injury and is an ideal stimulus for studying acute pain modulation. We therefore conducted a placebo-controlled double-blind crossover study to investigate the effects of naloxone on capsaicin-induced pain (five men, four women, aged 29 +/- 5 years). Capsaicin (10%) was applied topically and subjects rated pain every 2 min. The subjects were told that any drug given to them could increase, decrease, or not change their pain sensation. Pain plateaued after 20 min. At 26 min subjects received either naloxone or placebo in double-blind fashion. At 56 min subjects received the alternative (placebo or naloxone). In a second session the order of presentation was reversed. The naloxone induced a significant increase in pain compared both to baseline (P < 0.01) and placebo (P < 0.01). The peak effect, reached at 12-20 min after naloxone delivery, was 59% greater than placebo. This experiment suggests that acute pain is actively suppressed by endogenous opioid-receptor activation.

Theoretical review: altered pain regulatory systems in chronic pain

This review synthesizes the existing literature regarding the relationship between resting blood pressure and pain sensitivity, and the literature indicating possible endogenous opioid dysfunction in chronic pain. Adaptive interactions between the cardiovascular and pain regulatory systems occur in healthy individuals, with greater blood pressure associated with decreased acute pain sensitivity. Endogenous opioids appear necessary for full expression of this relationship. There is ample evidence indicating diminished endogenous opioid CSF/plasma levels in chronic pain patients, yet little is known about the functional effects of these opioid changes. A theoretical model is proposed based upon the literature reviewed suggesting progressive dysfunction in endogenous opioid systems with increasing chronic pain duration. This dysfunction is hypothesized to result in dysregulation of normally adaptive relationships between the cardiovascular and pain regulatory systems, resulting in increased chronic pain intensity and increased acute pain sensitivity among chronic pain patients. Preliminary data are consistent with the hypothesis of progressive opioid changes resulting in dysfunctional alterations in the adaptive blood pressure-pain relationship. Clinical implications of this theory are discussed.

Acute pain threshold in subjects with chronic pain following spinal cord injury

Studies of pain perception in patients with chronic pain have yielded contradictory results. While several studies found that acute pain threshold is raised in chronic pain subjects, others showed that these subjects exhibit a decreased pain threshold compared to pain free subjects. The aim of this study was to further examine this topic by studying pain perception in subjects with chronic pain following partial or complete spinal cord injury (SCI). We found a significant elevation of heat-pain threshold (measured above the level of lesion) in complete SCI subjects with chronic pain (CSCIP) as opposed to complete SCI subjects without pain, incomplete SCI subjects with (ISCIP) and without chronic pain and normal controls. This elevation of pain threshold was completely reversed following a complete relief of the chronic pain by DREZ lesion. Moreover, the CSCIP exhibited significantly higher scores in the McGill pain questionnaire compared to ISCIP, indicative of a more intense chronic pain perceived by these subjects. In addition, the chronic pain below the level of spinal lesion, reported by CSCIP originated from a significantly larger body area than that of ISCIP. These results indicate that a critical level of chronic pain must be perceived in order to induce an elevation in acute pain threshold.

Plasma and cerebrospinal fluid beta-endorphin in chronic tension-type headache

Previous studies have provided evidence of an increased sensitivity to pain, a decreased hypothalamic opioid tone, and decreased cerebrospinal fluid (CSF) beta-endorphin (beta-EP) concentration in patients with primary chronic headache. We applied separate specific radioimmunoassays for beta-EP in CSF and plasma on samples from age-matched controls and a group of 50 patients with chronic tension-type headache (CTH) fulfilling the diagnostic criteria set by the International Headache Society. Median CSF beta-EP concentrations (95% confidence limits) were 12.8 pmol/l (11.0-14.5) in CTH patients and 11.9 pmol/l (10.9-14.2) in the control group, which is not significantly different (P = 0.28). Plasma beta-EP concentrations did not differ either, being 3.1 pmol/l (2.4-3.7) and 3.3 pmol/l (1.8-4.0) in the patients with CTH and in controls, respectively (P = 0.88). Plasma and CSF beta-EP concentrations did not correlate. Reversed-phase high performance liquid chromatography (HPLC) of CSF pools from the headache patients and controls revealed similar profiles of beta-EP-immunoreactivity both when C-terminally and N-terminally directed antisera were used, suggesting a normal post-translational processing of the pro-opiomelanocortin gene in patients with CTH. beta-EP is not involved in the pathogenesis of CTH, or such a role is not reflected in CSF or plasma concentrations of the neuropeptide.

Chronic back pain, acute postoperative pain and the activation of diffuse noxious inhibitory controls (DNIC)

The effect of the presence of either chronic or acute clinical pain on pain threshold and on the nociceptive flexion reflex (RIII) threshold was studied. The experimental pain sensation and the flexion reflex were evoked by trains of short electrical pulses. It was hypothesized that both kinds of clinical pain would be able to induce 'diffuse noxious inhibitory controls' (DNIC) and thereby raise the 2 experimental thresholds. Patients with chronic low back pain, patients with postoperative pain from oral surgery, and pain-free subjects were tested in 3 conditions: during baseline, after i.v. administration of a placebo, and after i.v. administration of naloxone. In comparison with 2 pain-free control groups, the 2 pain groups had a significantly higher pain threshold in all conditions. However, the RIII threshold was not significantly elevated in chronic or acute pain patients compared to controls. Naloxone had no effect on the RIII or pain threshold in any of the groups. It is concluded that the increased pain threshold which is frequently found in chronic pain patients, and which could be confirmed in the present study, does not result from a DNIC effect. The adaptation level theory offers an alternative explanation. Also, the acute postoperative pain in this study did not seem to induce DNIC. Because other forms of acute pain have been found to be effective in activating DNIC, future research should establish which pains are and which pains are not effective.

Physiological relevance and time course of a tonic endogenous opioid modulation of nociceptive messages, based on the effects of naloxone in a rat model of localized hyperalgesic inflammation

In a rat model of localized hyperalgesic inflammation induced by intraplantar injection of carrageenin, the effect of a relatively high dose of naloxone (1 mg/kg i.v.) was investigated using the measure of the vocalization threshold as a nociceptive test, on both the inflamed and non-inflamed paws. The effects of the drug were determined at two different periods after the intraplantar injection of carrageenin, in the same group of rats. We showed that 4 h after carrageenin (a few hours after the onset of the inflammatory process), naloxone induced a significant further decrease in the vocalization threshold induced by pressure on either paw, suggesting that naloxone had reduced a tonically active inhibitory system involving endogenous opioid peptides. Twenty-four hours after carrageenin, a consistent hyperalgesic effect of naloxone was observable only in rats which had recovered from their carrageenin-induced hyperalgesia. A significant negative correlation between the behavioral effect of naloxone and the degree of hyperalgesia determined for each animal was observed. This suggests that the tonic inhibition exerted by the endogenous opioids was particularly effective in rats which recovered from their initial hyperalgesia. By contrast, these opioid controls could have been weaker in those rats which remained hyperalgesic.

Cephalic and extracephalic pressure pain thresholds in chronic tension-type headache

Pressure pain thresholds were assessed with an algometer (Somedic Inc.), over the forehead, temple and suboccipital region as well as over the Achilles tendon. A group of 32 patients suffering from chronic tension-type headache was compared to 20 healthy controls and to 10 migraineurs without aura. Although individual values were widely scattered, pressure pain thresholds were on average significantly lower in chronic tension-type headache, not only at pericranial sites but also over the Achilles tendon. Only 50% of these patients had one or more pericranial thresholds 1.5 S.D. below the mean of controls. After muscular biofeedback therapy, all pain thresholds were on average increased. Along with results obtained previously, the present data support the hypothesis that diffuse disruption of central pain-modulating systems, possibly due to a modified limbic input to the brain-stem, is pivotal in the pathophysiology of chronic tension-type headache.

Clinical and pathophysiological observations in migraine and tension-type headache explained by integration of vascular, supraspinal and myofascial inputs

A vascular-supraspinal-myogenic (VSM) model for pain in migraine based on our previous clinical and pathophysiological observations is proposed. According to the model, perceived pain (headache) intensity is determined by the sum of nociception from cephalic arteries and pericranial myofascial tissues converging upon the same neurons and integrated with supraspinal effects (usually facilitating). Vascular input predominates over myofascial input in migraine, whereas significance of supraspinal facilitation is difficult to estimate. The importance of these 3 effects may vary between patients and in the same individual with time. The model is in accordance with recent experimental studies showing convergence of somatovisceral afferents upon n. caudalis neurons. Also, long term potentiation due to nociceptive activation and sensitization of neurons to input from wider areas and non-nociceptive stimuli are relevant to our model. In tension-type headache, nociception is primarily myofascial, but vascular input cannot be disregarded. Supraspinal facilitation probably plays a large, sometimes dominant role (the MSV model). The model explains much of the complexity of the clinical picture of these disorders as well as their tendency to overlap and to change into one another. Also, a number of pathophysiological observations such as why muscles are tender during migraine, why trigger-point injection may cure migraine attacks and why chronic tension-type headache is often associated with episodes of pulsating pain, can be explained. The model gives a rational explanation of empirically developed, internationally accepted, multimodal treatment strategies for migraine and tension-type headache. It may thus serve a useful purpose in explaining the disorder to patients. Finally, the model points to several avenues of future research in animals and man.

Endogenous opiates: 1989

This paper is the twelfth installment of our annual review of the research published during 1989 involving the behavioral, nonanalgesic, effects of the endogenous opiate peptides. The specific topics this year include stress; tolerance and dependence; eating; drinking; gastrointestinal and renal functions; mental illness; learning, memory, and reward; cardiovascular responses; respiration and thermoregulation; seizures and other neurological disorders; electrical-related activity; locomotor activity; sex, development, pregnancy, and aging; immunological responses; and other behavior.