Michael A. Frölich

Opioid Overdose in a Patient Using a Fentanyl Patch During Treatment with a Warming Blanket

IMPLICATIONS This case describes the narcotic overdose associated with the use of a fentanyl transdermal patch in a patient being rewarmed with an external warming blanket during surgery. The clinical manifestation and the presumed pharmacokinetic mechanism responsible for the fentanyl overdose are discussed.

Baseline heart rate may predict hypotension after spinal anesthesia in prehydrated obstetrical patients.

PurposeHypotension is the most frequent complication of spinal anesthesia in pregnant patients. This study was designed to identify patients at risk for postspinal hypotension based on preoperative vital signs before and after an orthostatic challenge.MethodsForty healthy women scheduled for elective Cesarean section were enrolled in this prospective trial. Blood pressure (BP) and heart rate (HR) were recorded with the patient in the lateral supine position and after standing up. After a bupivacaine spinal anesthetic, BP was obtained every two minutes for 30 min. Ephedrine treatment was administered based on the degree of hypotension observed. Hemodynamic parameters were correlated to ephedrine requirements (Spearman’s rank order correlation).ResultsThere was a significant correlation in baseline maternal HR and ephedrine requirements (P = 0.005). The degree of orthostatic changes in mean arterial BP and HR did not correlate with postspinal hypotension.ConclusionsBaseline HR may be predictive of obstetric spinal hypotension. Higher baseline HR, possibly reflecting a higher sympathetic tone, may be a useful parameter to predict postspinal hypotension.RésuméObjectifChez les femmes enceintes, l’hypotension est la plus fréquente complication de la rachianesthésie. Notre étude veut identifier les patientes à risque d’hypotension postsrachidienne en notant les signes vitaux d’avant et après la provocation orthostatique.MéthodeQuarante femmes en bonne santé, devant subir une césarienne, ont participé à cet essai prospectif. La tension artérielle (TA) et la fréquence cardiaque (FC) ont été notées alors que la patiente est en décubitus latéral, puis en station debout. La TA a été enregistrée toutes les deux minutes pendant 30 min à la suite de l’administration rachidienne de bupivacaïne. De l’éphédrine a été donnée en fonction du degré d’hypotension observée. On a mis en corrélation les paramètres hémodynamiques et les besoins d’éphédrine (corrélation des rangs de Spearman).RésultatsUne corrélation significative a été notée entre la FC de base et les besoins d’éphédrine (P = 0,005). Il n’y a pas eu de corrélation entre le degré des modifcations orthostatiques de la TA et de la FC moyennes et l’hypotension postrachidienne.ConclusionLa FC initiale peut être prédictive d’hypotension rachidienne en obstétrique. Une FC initiale élevée, pouvant exprimer un tonus sympathique plus important, peut être un paramètre prédictif intéressant d’hypotension postrachidienne.

The effect of propofol on thermal pain perception

We studied the effect of propofol, a widely used sedative-hypnotic drug, on pain perception. Eighteen subjects received propofol in two sedative concentrations that were balanced and randomized in order. Painful (45°C, 47°C, and 49°C) stimulation temperatures were presented in random order, and nonpainful 31°C stimuli were presented on alternate trials. We used a target-controlled infusion and chose effect site concentrations of 0.5 &mgr;g/mL for mild sedation and 1.0 &mgr;g/mL for moderate sedation. Using a visual analog scale, subjects rated both pain intensity and unpleasantness higher when sedated with propofol. The average pain intensity was 28/100 for placebo, 35/100 for mild, and 40/100 for moderate sedation. Pain unpleasantness was 23/100 for placebo, 29/100 for mild, and 33/100 for moderate sedation. This effect was unexpected and may be explained by a difference of subjective pain experience by a patient and the perceived level of analgesia by a health care provider in sedated patients. This finding calls further attention to the need for adequate analgesia in patients sedated with propofol.

Pioneers in Epidural Needle Design

IMPLICATIONS In this article we discuss the development of epidural needles and the historical factors leading to their invention. The most popular needles are described and their inventors acknowledged.

Anesthesia for childbirth: Controversy and change☆☆☆

First introduced to medical practice in 1847, anesthesia for childbirth has undergone constant changes. Current practice reflects evolving social values as well as new discoveries in science and medicine.

Effect of sedation on pain perception.

Background:Sedation or anesthesia is used to facilitate many cases of an estimated 45 million diagnostic and therapeutic medical procedures in the United States. Preclinical studies have called attention to the possibility that sedative–hypnotic drugs can increase pain perception, but whether this observation holds true in humans and whether pain-modulating effects are agent-specific or characteristic of IV sedation in general remain unclear. Methods:To study this important clinical question, the authors recruited 86 healthy volunteers and randomly assigned them to receive one of three sedative drugs: midazolam, propofol, or dexmedetomidine. The authors asked participants to rate their pain in response to four experimental pain tasks (i.e., cold, heat, ischemic, or electrical pain) before and during moderate sedation. Results:Midazolam increased cold, heat, and electrical pain perception significantly (10-point pain rating scale change, 0.82 ± 0.29, mean ± SEM). Propofol reduced ischemic pain and dexmedetomidine reduced both cold and ischemic pain significantly (−1.58 ± 0.28, mean ± SEM). The authors observed a gender-by-race interaction for dexmedetomidine. In addition to these drug-specific effects, the authors observed gender effects on pain perception; female subjects rated identical experimental pain stimuli higher than male subjects. The authors also noted race–drug interaction effects for dexmedetomidine, with higher doses of drug needed to sedate Caucasians compared with African Americans. Conclusions:The results of the authors’ study call attention to the fact that IV sedatives may increase pain perception. The effect of sedation on pain perception is agent- and pain type-specific. Knowledge of these effects provides a rational basis for analgesia and sedation to facilitate medical procedures.

What factors affect intrapartum maternal temperature? A prospective cohort study: maternal intrapartum temperature.

Background: In recent years, several reports have indicated that maternal temperature elevations during labor may also be observed in the absence of an infection. Presumed noninfectious causes of maternal temperature elevations include epidural analgesia, endogenous heat production generated by the contracting uterus, and delivery in an overheated room. To investigate the potential causes of noninfectious maternal temperature changes during labor, we conducted a prospective cohort study in women scheduled for labor induction. Methods: We recorded hourly oral temperatures from admission to delivery. We calculated whether temperature changed during labor in 81 women. We then determined if body mass index, and duration of labor, or time from rupture of amniotic sac to delivery, or oxytocin dose, would affect maternal temperature. To evaluate the possible role of epidural analgesia, we compared the temperature slope before and after starting epidural analgesia. Results: We observed an overall significant linear trend of temperature over time with an estimated temperature slope of +0.017°C/h (P = 0.0093). Patients with a positive temperature trend had also a significantly longer time from rupture of membranes to delivery (P = 0.0077) and a higher body mass index (P = 0.0067). Epidural analgesia had no effect on the temperature trend. Conclusions: In our cohort of patients, there was an overall significant linear trend of temperature over time after correcting for heterogeneity among patients. Temperature increase was associated with higher body mass index values and longer time from rupture of membranes to delivery. Epidural analgesia had no effect on maternal temperature.

Role of the Atrial Natriuretic Factor in Obstetric Spinal Hypotension

Background In recent years, the concept of prophylactic volume expansion to prevent hypotension caused by spinal anesthesia has been challenged. Investigators have reevaluated the concept of prehydration in the obstetric patient and the physiologic mechanisms involved. This article addresses whether the hypotensive effects attributed to the atrial natriuretic factor are the reason for the apparent failure of prehydration. Methods Atrial natriuretic factor was measured before (baseline) and 10 min after spinal anesthetic drug injection (control) in 48 healthy pregnant patients scheduled for elective cesarean section. Sixteen patients received hydration with 15 ml/kg crystalloid immediately before spinal anesthesia, 16 patients received the same volume starting with the spinal anesthetic injection, and the remaining 16 patients received no prehydration (control). Blood pressure, heart rate, ephedrine requirements, infused fluids, and urine output were measured. Results Atrial natriuretic factor concentrations increased significantly in prehydrated patients but not in the control group. There was a significant correlation in the change in atrial natriuretic factor concentrations and urine output but no correlation in the control atrial natriuretic factor concentrations and blood pressure or ephedrine requirements. Ephedrine requirements and blood pressure did not differ significantly among study groups. Conclusions Atrial natriuretic factor is a potent endogenous diuretic in the pregnant patient but does not appear to be involved in short-term cardiovascular homeostasis after spinal anesthesia. Prehydration appears to prevent hypotension after spinal anesthesia in the obstetric patient.

Mandibular Osteoma: A Case of Impossible Rigid Laryngoscopy

THE airway management of a surgical patient is one of the anesthesiologists primary concerns. The combination of several parameters seems to predict difficult laryngoscopy and intubation: short thyro-mental distance, protruding incisors, micrognathia, small mouth opening, acromegalic features, short neck, morbid obesity, and others. This case report describes another rare and frequently unrecognized physical feature associated with difficult intubation: a mandibular osteoma.

Intravenous lidocaine reduces ischemic pain in healthy volunteers.

Background and Objectives: Lidocaine, a local anesthetic and antiarrhythmic drug that alters depolarization in neurons by blocking the fast voltage-gated sodium (Na+) channels in the cell membrane, is used for regional anesthesia, as antiarrhythmic drug, and as analgesic for various painful conditions. It is unclear whether monotherapy with intravenous lidocaine has an analgesic effect in healthy individuals. To address this important question, we studied pain perception before, during, and after the administration of intravenous lidocaine in 16 human volunteers. Our hypothesis was that lidocaine, administered as a short intravenous infusion, does not have an analgesic effect in healthy volunteers. Methods: Sixteen healthy human volunteers received systemic lidocaine at plasma concentration 2 mg/mL using a computer-assisted infusion. Participants underwent a series of sensory tests-thermal, electrical, and ischemic pain and normal pinprick sensation-at baseline, during, and 30 mins after administration of a 20-min lidocaine infusion at a 2 mg/mL effect site concentration. Results: We found a sustained decrease in ischemic pain ratings and a limited analgesic effect for electrical pain, whereas thermal pain and normal sensation did not change. Conclusions: The observed sustained analgesic effect of systemic lidocaine in the ischemic pain model suggests that lidocaine may be used to treat acute pain.