Wolfgang Ummenhofer

Transient Neurologic Symptoms After Spinal Anesthesia

We recently reported several cases consistent with transient radicular irritation after spinal anesthesia with hyperbaric 5% lidocaine.The present prospective, blind, nonrandomized study was performed to determine the incidence of these transient neurologic symptoms and to identify factors that might be associated with their occurrence. We studied 270 patients scheduled for gynecologic or obstetric procedures under spinal anesthesia. For spinal anesthesia, either 5% lidocaine in 7.5% glucose or 0.5% bupivacaine in 8.5% glucose was used. Patients were evaluated on postoperative day 3 by a quality assurance nurse who was unaware of the drug given or details of the anesthetic technique. Transient neurologic symptoms were observed in 37% of patients receiving 5% lidocaine, whereas only one patient receiving 0.5% bupivacaine had transient hypesthesia of the lateral aspect of the right foot. These results suggest that symptoms were the result of a specific drug effect. However, because of the limitations of the study one cannot conclude that lidocaine per se was the cause. (Anesth Analg 1995;81:1148-53)

Comparative spinal distribution and clearance kinetics of intrathecally administered morphine, fentanyl, alfentanil, and sufentanil.

Background: Despite widespread use, little is known about the comparative pharmacokinetics of intrathecally administered opioids. The present study was designed to characterize the rate and extent of opioid distribution within cerebrospinal fluid, spinal cord, epidural space, and systemic circulation after intrathecal injection. Methods: Equal doses of morphine and alfentanil, fentanyl, or sufentanil were administered intrathecally (L3) to anesthetized pigs. Microdialysis probes were used to sample cerebrospinal fluid at L2, T11, T7, T3, and the epidural space at L2 every 5–10 min for 4 h. At the end of the experiment, spinal cord and epidural fat tissue were sampled, and each probe’s recovery was determined in vitro. Using SAAM II pharmacokinetic modeling software (SAAM Institute, University of Washington, Seattle, WA), the data were fit to a 16-compartment model that was divided into four spinal levels, each of which consisted of a caternary arrangement of four compartments representing the spinal cord, cerebrospinal fluid, epidural space, and epidural fat. Results: Model simulations revealed that the integral exposure (area under the curve divided by dose) of the spinal cord (i.e., effect compartment) to the opioids was highest for morphine because of its low spinal cord distribution volume and slow clearance into plasma. The integral exposure of the spinal cord to the other opioids was relatively low, but for different reasons: alfentanil has a high clearance from spinal cord into plasma, fentanyl distributes rapidly into the epidural space and fat, and sufentanil has a high spinal cord volume of distribution. Conclusions: The four opioids studied demonstrate markedly different pharmacokinetic behavior, which correlates well with their pharmacodynamic behavior.

Epidural, cerebrospinal fluid, and plasma pharmacokinetics of epidural opioids (part 1): differences among opioids.

Background The pharmacokinetics of epidurally administered drugs has been the subject of many studies, yet drug concentration in the epidural space has never been measured. This study was undertaken to characterize the epidural, cerebrospinal fluid, and plasma pharmacokinetics of epidurally administered opioids on the basis of measurement of drug concentration in each of these compartments after epidural administration. Methods Morphine plus alfentanil, fentanyl, or sufentanil were administered epidurally in anesthetized pigs. Microdialysis was used to sample the epidural space and the cerebrospinal fluid for measurement of opioid concentration over time. Plasma samples were obtained from the central venous plasma and the epidural venous plasma. These data were used to calculate relevant pharmacokinetic parameters, including mean residence time, elimination half-lives, areas under the concentration versus time curves, clearance, and volume of distribution for each opioid in each compartment. Results Some of the more important findings were that the cerebrospinal fluid and plasma pharmacokinetics of the opioids did not parallel their epidural pharmacokinetics and that their hydrophobic character governed multiple aspects of their lumbar epidural pharmacokinetics. Conclusions The findings indicate that the spinal pharmacokinetics of these drugs are complex and, in some ways, counterintuitive. Also, the bioavailability of opioids in the cerebrospinal fluid and epidural space is determined primarily by their hydrophobicity, with less hydrophobic drugs having greater bioavailability.

Rocuronium versus succinylcholine for rapid sequence induction of anesthesia and endotracheal intubation: a prospective, randomized trial in emergent cases

When anesthesia is induced with propofol in elective cases, endotracheal intubation conditions are not different between succinylcholine and rocuronium approximately 60 s after the injection of the neuromuscular relaxant. In the present study, we investigated whether, in emergent cases, endotracheal intubation conditions obtained at the actual moment of intubation under succinylcholine differ from those obtained 60 s after the injection of rocuronium. One-hundred-eighty adult patients requiring rapid sequence induction of anesthesia for emergent surgery received propofol (1.5 mg/kg) and either rocuronium (0.6 mg/kg; endotracheal intubation 60 s after injection) or succinylcholine (1 mg/kg; endotracheal intubation as soon as possible). The time from beginning of the induction until completion of the intubation was shorter after the administration of succinylcholine than after rocuronium (median time 95 s versus 130 s; P < 0.0001). Endotracheal intubation conditions, rated with a 9-point scale, were better after succinylcholine administration than after rocuronium (8.6 ± 1.1 versus 8.0 ± 1.5; P < 0.001). There was no significant difference in patients with poor intubation conditions (7 versus 12) or in patients with failed first intubation attempt (4 versus 5) between the groups. We conclude that during rapid sequence induction of anesthesia in emergent cases, succinylcholine allows for a more rapid endotracheal intubation sequence and creates superior intubation conditions compared with rocuronium.

The use of Glasgow Coma Scale in injury assessment: a critical review.

Primary objective: Patients with brain injuries are assessed using the Glasgow Coma Scale (GCS). This review evaluates the use of GCS scoring in medical literature and identifies the reasons for inaccuracy. Literature selection and critical appraisal: Pubmed and ISI Web of Knowledge SM were searched using specific keywords. The authors critically appraised the current state of GCS scoring, GCS definitions, the time and frequency of assessment, confounders, GCS reporting and GCS assessment schemes. Main outcome and results: More than 90% of the publications using GCS scoring cite the 14-item GCS rather than the 15-item GCS. The timing of the initial GCS assessment is inconstant. GCS components are seldom utilized, contributing to the loss of information. Confounders are often not reported and, if they are, not in a standardized manner. The order of the GCS components is not consistent. Conclusions: The current inconsistent and inappropriate use of GCS diminishes its reliability in both a clinical and a scientific context. A consensus statement is needed to correct this situation. Citing the correct references, early and repeated GCS assessments at defined intervals, standardized reporting of confounders and GCS component plus sum scores, and the utilization of a uniform assessment scheme are recommended.

Are laboratory values in bone marrow aspirate predictable for venous blood in paediatric patients

In an emergency situation, early laboratory results are important, but often difficult to obtain. If venous access cannot be established, the intraosseous route may be used as an alternative. This study investigated the predictive value of bone marrow aspirate in performing laboratory studies. Thirty children underwent general anaesthesia for bone marrow aspiration (iliac crest) for oncologic or haematologic reasons. The aspirate and a peripheral venous blood sample, which was obtained simultaneously, were subjected to different laboratory tests and the results were compared by means of confidence interval analyses of the individual ratios of venous/bone marrow values. Based on these analyses, a high predictability of bone marrow values were found for haemoglobin, sodium, chloride, glucose, bilirubin, urea, creatinine, pH, and standard bicarbonate. Moderate, but clinically useful predictability was found for haematocrit, potassium, and total protein, while bone marrow values of alkaline phosphatase, aspartate aminotransferase, alanine aminotransferase, PCO2, PO2, thrombocytes and leukocytes were systematically different from values in venous blood. Our data suggest that the intraosseous route is not only an important emergency alternative to intravenous access for administering fluids and drugs but may also serve as a reliable alternative for obtaining initial diagnostic laboratory studies when intravascular access is not obtainable.

Difficult intubation in paediatrics

Optimal oxygenation and ventilation in anaesthetized or critically ill patients are crucial and because of the increased oxygen consumption and decreased oxygen reserve, hypoxaemia occurs more rapidly in infants and children than in adults. Several pathological conditions may lead to problems in airway management and in tracheal intubation, some of which are comparable while others differ markedly from those in adults. In nonobstetric adult surgical patients, the incidence of failed intubation is 12303 (l), whereas in obstetric patients it is as high as 1:300 (2). Difficult intubation occurs at a rate between 1.5 and 13% (3). The incidence of difficult or failed intubation in otherwise healthy children is not known but it is suggested that it is less than the above figures. In patients with rare diseases and syndromes, difficult intubation may occur more frequently.

Epidural, Cerebrospinal Fluid, and Plasma Pharmacokinetics of Epidural Opioids (Part 2)Effect of Epinephrine

Background The ability of epinephrine to improve the efficacy of epidurally administered drugs is assumed to result from local vasoconstriction and a consequent decrease in drug clearance. However, because drug concentration in the epidural space has never been measured, our understanding of the effect of epinephrine on epidural pharmacokinetics is incomplete. This study was designed to characterize the effect of epinephrine on the epidural, cerebrospinal fluid, and plasma pharmacokinetics of epidurally administered opioids. Methods Morphine plus alfentanil, fentanyl, or sufentanil was administered epidurally with and without epinephrine (1:200,000) to pigs. Opioid concentration was subsequently measured in the epidural space, central venous plasma, and epidural venous plasma, and these data were used to calculate relevant pharmacokinetic parameters. Results The pharmacokinetic effects of epinephrine varied by opioid and by sampling site. For example, in the lumbar epidural space, epinephrine increased the mean residence time of morphine but decreased that of fentanyl and sufentanil. Epinephrine had no effect on the terminal elimination half-life of morphine in the epidural space, but it decreased that of fentanyl and sufentanil. In contrast, in the lumbar intrathecal space, epinephrine had no effect on the pharmacokinetics of alfentanil, fentanyl, or sufentanil, but it increased the area under the concentration–time curve of morphine and decreased its elimination half-life. Conclusions The findings indicate that the effects of epinephrine on the spinal pharmacokinetics of these opioids are complex and often antithetical across compartments and opioids. In addition, the data clearly indicate that the pharmacokinetic effects of epinephrine in spinal “compartments” cannot be predicted from measurements of drug concentration in plasma, as has been assumed for decades.

Effects of Ondansetron in the Prevention of Postoperative Nausea and Vomiting in Children

BackgroundPostoperative nausea and vomiting (PONV) is a commonly observed adverse effect of general anesthesia. Recently, ondansetron, a new serotonin3 (5-hydroxytryptamine3) receptor antagonist was shown to be effective in the prophylaxis and prevention of chemotherapy-induced nausea and vomiting in children and adults as well as of PONV in adults. The aim of the current study was to evaluate the capacity of ondansetron to prevent PONV in pediatric patients. MethodsTwo hundred children (132 boys and 68 girls) 2–10 yr of age received general inhalational anesthesia for surgical procedures (the extremities; ear, nose, and throat; inguinal hernia and phimosis; and dentistry) of an expected duration of less than 90 min. This study was divided into two phases: prophylaxis and rescue treatment. For prophylaxis, patients were randomly assigned to two groups: one group received an intravenous injection of 0.1 mg/kg ondansetron, and the other group received a placebo before surgical incision under double-blind conditions. For rescue treatment, only placebo patients were included; as a rescue medication they received an intravenous injection of 0.1 mg/kg ondansetron or 0.02 mg/kg droperidol according to a prestudy randomization under double-blind conditions. Incidence and severity of PONV (PONV score 0 = no nausea and no retching; 1 = complaining of sickness and retching; 2 = vomiting one or two times in 30 min; 3 = vomiting more than two times in 30 min) was recorded over a 4-h period in the postanesthesia care unit. Within 72 h of the procedure, a follow-up nurse interviewed the parents for late-onset nausea in the children. ResultsWith regard to prophylaxis, 10% of patients receiving ondansetron had PONV during the 4-h observation period versus 40% of those receiving placebo (P < 0.001). The incidence of vomiting alone (PONV score ≤ 2) was 5% and 25%, respectively (P < 0.001). There were no significant differences between ondansetron and droperidol in the treatment of PONV. However, at the end of the 4-h period, ondansetron patients were less sedated than were patients who had received droperidol (P < 0.01). Interviews with parents could be performed for 143 of 200 children (76 ondansetron and 67 placebo). Twenty-four children (15 ondansetron and 9 placebo) showed late-onset PONV after the 4-h observation period but within 24 h of the procedure (19.7% vs. 13.4%; P not significant). ConclusionsOndansetron is effective in the prevention of PONV in pediatric patients for the first 4 h after general anesthesia. Lower sedation scores with ondansetron compared with droperidol may be an advantage, especially in ambulatory surgery. However, the incidence of late-onset PONV (>4–24 h) was not influenced by prophylactic treatment with one dose of ondansetron preoperatively.

The airway endoscopy mask: useful device for fibreoptic evaluation and intubation of the paediatric airway

A mask is presented which allows the administration of 100% oxygen, inhalational anaesthetics, continuous positive airway pressure and intermittent positive pressure ventilation during diagnostic airway endoscopy and difficult intubation with a fibreoptic bronchoscope in paediatric patients. The mask is particularly useful in small or critically ill patients. It may also have its place in teaching situations.