Correlating autonomic physiology with symptoms of autonomic dysreflexia after spinal cord injury.
Jennifer Dens Higano, Kathryn Burns, Geoffrey Smith and 1 others
PMID 39817508WHAT IT FOUND
Heart-rate slowing and blood-pressure response did not track with reported autonomic dysreflexia symptoms in people with SCI, even though those measures differed from controls.
Key findings
01In the 14 participants with SCI, autonomic dysreflexia symptom scores did not meaningfully correlate with baroreflex sensitivity (R2=0.09) or MAP AUC (R2=0.008).
02Participants with SCI had lower baroreflex sensitivity than controls (15.0 ± 8.3 vs 23.7 ± 9.3 ms/mmHg, p=0.01).
03Participants with SCI had larger blood-pressure response to phenylephrine (0.26 ± 0.19 vs 0.06 ± 0.06 mmHg·s/kg·μg, p=0.002) and greater lower-extremity vascular resistance increase (24 ± 18.7% vs 6 ± 11.3%, p=0.007).
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
The study was small, with only 14 participants with SCI and 17 controls, so it cannot support subgroup conclusions about injury level or severity. The participants with SCI had a wide range of injury levels and AIS grades, and the sample was too small to analyze these groups separately. Phenylephrine was used to raise blood pressure in the lab, and the authors note this may not fully reproduce the neurotransmitter effects of an actual autonomic dysreflexia episode. Symptoms were measured with a survey, and objective AD episodes can be silent, so past symptom burden may not match what happened during the lab tests. Because baseline lower-extremity vascular resistance differed between groups, the analysis relied on percent change rather than raw resistance.
Declared interests
The supplied text lists NIH extramural research support as a publication type. No author conflicts of interest are stated.
The easy way to misread this
Do not use these lab measurements to predict a patient's autonomic dysreflexia symptoms. In the 14 participants with SCI, heart-rate slowing and blood-pressure response did not meaningfully relate to symptom scores, and the study was too small to make this a bedside rule.