BACKGROUND AND OBJECTIVES: It is commonly thought that pain stimulates respiration. The goal of this study was to determine any effect on ventilation caused by acute pain in patients with upper extremity injuries by measuring CO2-response curves before and after regional anesthesia. METHODS: Four patient volunteers refrained from taking analgesic medications during the study period. Visual analogue scale (VAS) pain scores (10 cm scale), resting ventilation and P(ET)CO2, and steady-state, CO2-response curves (4% and 7% inspired CO2) were determined just before and after axillary block anesthesia. RESULTS: Axillary block anesthesia reduced VAS pain scores from 7.1 +/- 1.1 to 0.7 +/- 0.5 (p < 0.05). Resting ventilation and P(ET)CO2 were unchanged. CO2-response curve slopes decreased from 1.84 +/- 0.54 to 1.40 +/- 0.58 l/min-1.mm Hg-1 (p < 0.05), and the curves were displaced 3.2 +/- 1.2 mm Hg to the right at 25 l/min-1 VE (p < 0.05). CONCLUSIONS: Other causes for the respiratory changes observed are discussed. It is concluded that acute pain stimulates respiration as measured by the steady-state, CO2-response method and that relief of acute pain results in a decrease in CO2-mediated ventilatory drive. More research is needed using both experimental pain models and patients with chronic pain.

Acute Disease↗

PubMedDate not supplied

Effects of epidural test dose volume on skin perfusion, temperature, and reflex vasoconstriction.

BACKGROUND AND OBJECTIVES: The authors sought to define the effects of differing volumes of epidural test dose on skin perfusion, skin temperature, and reflex vasoconstriction to a maximal inspiration (inspiratory gasp vasoconstrictive response, IGVR). METHODS: With informed consent and Institutional Review Board approval, the authors studied 40 patients undergoing epidural anesthesia. Skin perfusion was monitored in glabrous skin on the foot using laser Doppler. Inspiratory gasp vasoconstrictive response and temperature measurements were obtained at 1-minute intervals. After a baseline period, 5 patients received 60 mg intravenous lidocaine HCl; 5 received 5 mL normal saline, via epidural catheter; and 30 patients received 50 mg lidocaine HCl and 20 mcg epinephrine in 2.5, 5.0, or 7.5 mL normal saline (10 patients each). Inspiratory gasp vasoconstrictive response was defined as the percent change in perfusion from baseline produced by an inspiratory gasp. Perfusion was normalized by expressing each patient's value as a percentage of the respective baseline value. RESULTS: Significant increases in perfusion, of up to 169% of baseline, were seen 12 minutes after the test dose. Inspiratory gasp vasoconstrictive response showed significant changes from baseline in all test groups. The temperature change was insignificant. Control groups did not show perfusion or IGVR changes. CONCLUSIONS: Skin perfusion and IGVR changed significantly after epidural test dose; the minimal effect of volume appears to be 5 mL of lidocaine-epinephrine solution; the presence of IGVR or perfusion changes, or both, are positive predictors of successful placement of the catheter into the epidural space; and temperature changes as observed here were not reliable predictors of proper placement of epidural catheters.

Aged↗

PubMedDate not supplied

The dribble speed for spinal anesthesia.

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Anesthesia, Spinal↗