Denis L. Bourke

Improved postoperative analgesia with morphine added to axillary block solution

STUDY OBJECTIVE To determine whether the addition of morphine to the axillary block local anesthetic solution provides improved or prolonged postoperative analgesia. DESIGN Prospective, randomized, double-blind clinical trial with 24-hour follow-up. SETTING Ambulatory unit of a large academic referral center. PATIENTS Consecutive healthy volunteers scheduled for elective upper extremity surgery. INTERVENTIONS Patients in the treatment group (AX) were given intravenous (IV) saline and had morphine 0.1 mg/kg added to their axillary block solution. Control subjects (CT) received morphine 0.1 mg/kg IV and had saline added to their axillary block solution. All axillary blocks were performed using 0.55 ml/kg of 1.5% lidocaine with epinephrine 1:200,000. MEASUREMENTS AND MAIN RESULTS During the first 24 hours after surgery, visual analog scale (VAS) scores, supplementary analgesic (oxycodone 5 mg with acetaminophen 500 mg) use, and complications were recorded. Both groups had similar VAS scores throughout the study. In the 24-hour postoperative study period, AX patients required approximately half as many doses (median, 2 doses; range, 0 to 7 doses of supplemental analgesic as CT patients (median, 4 doses; range, 0 to 12 doses). There were no major complications in either group. CONCLUSIONS The addition of morphine 0.1 mg/kg to the local anesthetic axillary block solution provided improved postoperative analgesia without an increased frequency of side effects or major complications.

Time course of sympathetic blockade during epidural anesthesia : laser Doppler flowmetry studies of regional skin perfusion

&NA; We studied the time course of sensory and sympathetic blockade in response to epidural local anesthetic test and bolus doses in 11 patients. Sympathetic activity was measured by monitoring cutaneous perfusion in the foot and the reflex vasoconstrictive response to deep inspiration (IGVR) using laser Doppler flowmetry. Sensory tests included the detection of touch, cold and painful stimuli. Following the 3‐mL test dose perfusion increased to 192 ± 38% (mean ± SEM) of baseline (P < 0.05) in the patients with successful epidural anesthesia (9 of 11). In 8 of these patients, IGVR decreased to 73 ± 10% of baseline (P < 0.05) within 6 min of the test dose, and preceded changes in sensation to cold, pin‐prick, and light touch by 3.8 ± 3.5 min (P < 0.2), 9.6 ± 3.1 min (P < 0.01), and 11.6 ± 2.7 min (P < 0.01), respectively. Five control patients who received only 60 mg of lidocaine intravenously and the two patients with failed epidurals did not show any perfusion or IGVR changes. This study confirms that sympathetic block precedes sensory block in sacral dermatomes after epidural anesthesia. Perfusion and IGVR changes are sensitive measures of sympathetic blockade and may predict successful epidural catheter placement. (Anesth Analg 1993;76:289‐94)

Epidural opioids during laminectomy surgery for postoperative pain.

STUDY OBJECTIVE To determine whether morphine applied directly to the dura during laminectomy surgery provides superior postoperative analgesia during the first 24 hours. DESIGN Randomized, double-blind study. SETTING A university-affiliated hospital. PATIENTS Twenty ASA physical status I and II patients ages 18 to 60 years. INTERVENTIONS Simultaneous topical dural application and intramuscular (IM) injection of unknown solutions of saline and morphine 3 mg. MEASUREMENTS AND MAIN RESULTS Postoperative analgesia was assessed using the visual analog scale (VAS), a modified McGill-Melzack pain questionnaire, subjective nursing evaluations, and the amount of supplemental analgesic medication used. Patients were observed for complications and side effects. Compared with the patients who received epidural saline and IM morphine, the patients who received epidural morphine and IM saline had less postoperative pain as determined by VAS scores, nursing evaluations, and amount of supplemental opioid analgesic doses (1.6 +/- 1.2 vs. 4.1 +/- 1.2 analgesic doses per patient; p less than 0.05) required in the first 24 hours. Minor side effects were similar for the two groups. No patient developed respiratory depression. CONCLUSIONS Morphine 3 mg applied topically to the dura at the end of laminectomy surgery is a simple, safe, and effective way of providing improved postoperative analgesia.

The safety of intravenous phentolamine administration in patients with neuropathic pain.

The safety of intravenous (i.v.) infusion of large doses of phentolamine as an outpatient diagnostic tool for sympathetically maintained pain was studied retrospectively in 100 consecutive patients (73 females and 27 males) with chronic pain. All patients were pretreated with i.v. fluids followed, in most cases, by propranolol, 1-2 mg i.v. (n = 95). Ten minutes later the phentolamine infusion commenced, lasting for 20 min. In 90 patients, the dose of phentolamine was 35 mg. Two patients received 25 mg, and 8 patients received larger doses of 50-75 mg. No major complications occurred during or after the test, and only small changes in arterial blood pressure or heart rate were observed. All patients developed mild nasal stuffiness, but no decline in oxygen saturation was observed. Five patients developed one of the following minor complications for a brief duration, that resolved spontaneously: sinus tachycardia, premature ventricular beats, dizziness, or wheezing. We conclude that i.v. phentolamine administration is safe in patients with neuropathic pain.

Capacity to Give Surgical Consent Does Not Imply Capacity to Give Anesthesia Consent: Implications for Anesthesiologists

There is precedent in medicine for recognizing and accepting intact decisional capacity and the subsequent ability to provide valid consent in one treatment domain, while simultaneously recognizing that the patient lacks decisional capacity in other domains. As such, obtaining consent for anesthesia for a surgical procedure is a separate entity from obtaining consent for the surgery itself. Anesthesia for surgery and the surgical procedure itself are separate treatment domains and as such require separate consents. Anesthesiologists should understand the independence of these functionally linked consent processes and be vigilant with respect to the informed consent process. The cases reported in this article show that capacity for surgical consent may be inadequate for consent to anesthesia because anesthesia involves more abstract concepts requiring a higher cognitive state than surgery, thus requiring a higher state of cognitive capacity for understanding.

Quantitative testing of sympathetic function with laser Doppler flowmetry

Objective. The objective of this study was to develop an indirect technique for evaluating dynamic changes in sympathetic function in humans.Methods. We used laser Doppler to monitor sympathetic mediated vasoconstrictive responses (VRs) produced by 3 different provocative stimuli: 4-second inspiratory gasp (IG), ice-water immersion (Ice), and a spring-loaded pin prick (Pin). Skin perfusion on the thenar eminence was continuously monitored in 10 normal subjects (aged 25 to 36 years) using laser Doppler. Ten trials of the 3 stimuli were presented to each subject at 1-minute intervals. We determined the VR, the percent decrease in perfusion produced by each stimulus, and the 2 standard deviation variation in perfusion.Results. No subject found the IG maneuver uncomfortable. In contrast, the Pin and Ice stimuli were reported to be uncomfortable by 8 and 10 subjects, respectively. Five subjects found Pin and Ice stimuli overtly painful. Vasoconstrictive response was 54.1 ± 2.3% (mean ± SEM) with IG, 49.2 ± 2.0% with Ice, and 24.0 ± 1.8% with Pin. Baseline variation was approximately 15% in all trials.Conclusion. Inspiratory gasp vasoconstrictive response (IGVR) is a sensitive indirect technique for evaluating sympathetic efferent function. We observed that the magnitude of the VR elicited by the IG stimuli was similar to that induced by cold water. Unlike the VR induced by Pin or Ice, IGVR is not dependent on noxious input via somatic afferents; therefore, it can be used in patients with diseases that produce a peripheral neuropathy, such as diabetes mellitus. Present uses of this technique and speculation on future uses are presented.RésuméObjectif. L’objectif de cette étude est de développer une technique indirecte d’éevaluation des modifications dynamiques de la fonction sympathique chez Thomme.Méthodes. Nous avons utilisé un Doppler laser pour mesurer la reponse vasoconstrictrice sympathique (RVS) à trois stimuli differents: effort inspiratoire prolongé de 4 secondes (El), im mersion dans l’eau froide (EF), et piqûre par aiguille montée sur ressort (PIQ). La perfusion cutanee de l’éminence thénar a été monitorée chez 10 sujets normaux (âgés de 25 à 36 ans) en utilisant un Doppler laser. 10 applications des trois stimuli ont été réalisées chez chaque patient á 1 minute d’intervalle. Nous avons déterminé la RVS c’est-à-dire le pourcentage de décroissance de la perfusion produite par chaque stimulus et l’intervalle de variation de perfusion à deux écarts-type.Résultats. Aucun sujet n’a trouvé le stimulus El inconfortable. Par contre, les stimuli EF et PIQ furent jugés inconfortables respectivement par 8 et 10 sujets, 5 sujets ont trouvé les stimuli EF et PIQ manifestement douloureux. La réponse vasoconstrictrice fut de 54,1 ± 2,3% (moyenne ± écart-type) avec IG, 49,2% ± 2,0% avec EF, et 24,0 ± 1,8% avec PIQ. La variation de ligne de base a été approximativement de 15% durant l’etude.Conclusion, La réponse vasoconstrictrice liée un effort inspiratoire prolongé (RVEI) est une technique indirecte sensible d’evaluation des efférences sympathiques. Nous avons observe que l’amplitude de la RV induite par le stimulus El est semblable à celle induite par l’eau froide. Au contraire de la RV induite par PIQ ou EF, RVEI n’est pas dépendant de la production nociceptive via les afférences somatiques. Par conséquent, elle pourrait être utilisée chez les patients présentant une maladie à l’origine d’une neuropathie périphérique telle que le diabéte sucré. L’utilisation actuelle de cette technique et l’extrapolation à des utilisations futures sont présentées.KurzfassungZiel. Das Ziel dieser Untersuchung war die Entwicklung einer indirekten Technik zur Beurteilung dynamischer Veränderungen der sympathischen Funktion des Menschen.Methoden. Wir verwendeten das Laser-Doppler-Verfahren zur Überwachung sympathisch vermittelter vasokonstriktiver Reaktionen (VR), die von drei unterschiedlichen anregenden Reizen ausgelost wurden: 4-Sekunden inspiratorische Atemunterbrechung (IG), Eiswasser-Immersion (Eis) und Stiche einer federgespannten Nadel (Nadel). Die Hautperfusion am Daumenballen wurde bei 10 normalen Personen (zwischen 25 und 36 Jahren) mit Laser Doppler ständig über-wacht. Jede Person wurde im Abstand von 1 Minute je 10 Versuchen der 3 Reize ausgesetzt. Wir bestimmten die VR, die prozentuale Abnahme der Perfusion, die von jedem Reiz erzeugt wurde, und die Variation der Perfusion um 2 Standardabweichungen.Ergebnisse. Das IG-Verfahren war keiner Person unangenehm. Im Gegensatz dazu wurden die Reize durch Nadel und Eis von 8 bzw. 10 Personen als unangenehm bezeichnet. 5 Personen empfanden die Reize durch Nadel und Eis als offenkundig schmerzlich. Die vasokonstriktive Reaktion betrug 54,1% ± 2,3% (Mittel ± SEM) mit IG, 49,2% +- 2,0% mit Eis und 24,0% ± 1,8% mit Nadel. Die Abweichungen vom Mittelwert betrug in alien Versuchen etwa 15%.Schlußfolgerung. Die vasokonstriktive Reaktion auf inspiratorische Atemunterbrechung (IGVR) ist eine empfindliche indirekte Technik zur Bewertung sympathischer efferenter Funktionen. Wir beobachteten, daß die Größen der durch den IG-Stimulus und durch kaltes Wasser ausgelösten VRs ähnlich waren. Anders als die durch Nadel oder Eis ausgelöste VR, ist die IGVR nicht von schädlicher Gabe somatischer Beeinflussung abhangig; sie kann daher bei Patienten mit Krankheiten, die eine periphere Neuropathie wie Diabetes Mellitus erzeugen, angewendet werden. Es werden derzeitige Anwendungen dieser Technik und Vermutungen über zukünftige Anwendungen vorgestellt.ResumenObjetivo. El objetivo de este estudio fue desarrollar una técnica indirecta para evaluar cambios dinámicos de la función simpática en humanos.Métodos. Usamos laser Doppler para monitorizar respuestas vasoconstrictoras mediadas por el sistema simpático, producidas por tres estímulos provocantes distintos: Inspiración máxima mantenida de 4 segundos, inmersión en agua helada, y pinchazo con un alfiler activado por resorte. La perfusión cutánea de la eminencia tenar fue monitorizada en forma permanente en 10 sujetos normales, cuyas edades fluctuaban entre 25 y 36 años, mediante laser Doppler. Diez series de cada uno de los tres estímulos fueron presentados a cada sujeto con intervalos de un minuto. Determinamos la respuesta vasoconstrictora, el porcentaje de disminución de la perfusión cutanea producido por cada estímulo, y las dos desviaciones standard en la perfusión.Resultados. Ningún sujeto considero desagradable la estimulación por inspiración máxima mantenida. Por el contrario, el estímulo por hielo y por pinchazo fueron considerados desagradables por 8 y 10 sujetos, respectivamente; cinco consideraron al hielo y al pinchazo como francamente dolorosos. La respuesta vasoconstrictora fue 54.1 ± 2.3% (promedio ± ES) con inspiración máxima mantenida, 49.2 ± 2% con hielo, y 24.0 ± 1.8% con pinchazo. La variación basal fue aproximadamente 15% en todas las series.Conclusión. La respuesta vasoconstrictora a la inspiración maxima mantenida es una técnica indirecta sensible para evaluar funcion simpatica eferente. Observamos que la magnitud de la vasoconstricción evocada por la inspiración mantenida fue similar a la producida por agua con hielo. A diferencia de la vasoconstricción inducida por hielo o pinchazo, la inducida por inspiración máxima mantenida no dependió de aferencia nociceptiva por via somática; por lo tanto, puede ser usada en pacientes portadores de enfermedades que producen neuropatía periférica, tales como diabetes mellitus. Se presentan usos actuales de esta técnica y se especula respecto a usos futuros.