Po Tong Chui

Real-time ultrasound-guided paramedian epidural access: evaluation of a novel in-plane technique

BACKGROUND Current methods of locating the epidural space rely on surface anatomical landmarks and loss-of-resistance (LOR). We are not aware of any data describing real-time ultrasound (US)-guided epidural access in adults. METHODS We evaluated the feasibility of performing real-time US-guided paramedian epidural access with the epidural needle inserted in the plane of the US beam in 15 adults who were undergoing groin or lower limb surgery under an epidural or combined spinal-epidural anaesthesia. RESULTS The epidural space was successfully identified in 14 of 15 (93.3%) patients in 1 (1-3) attempt using the technique described. There was a failure to locate the epidural space in one elderly man. In 8 of 15 (53.3%) patients, studied neuraxial changes, that is, anterior displacement of the posterior dura and widening of the posterior epidural space, were seen immediately after entry of the Tuohy needle and expulsion of the pressurized saline from the LOR syringe into the epidural space at the level of needle insertion. Compression of the thecal sac was also seen in two of these patients. There were no inadvertent dural punctures or complications directly related to the technique described. Anaesthesia adequate for surgery developed in all patients after the initial spinal or epidural injection and recovery from the epidural or spinal anaesthesia was also uneventful. CONCLUSIONS We have demonstrated the successful use of real-time US guidance in combination with LOR to saline for paramedian epidural access with the epidural needle inserted in the plane of the US beam.

Thoracic paravertebral block for management of pain associated with multiple fractured ribs in patients with concomitant lumbar spinal trauma

Background and Objectives The need for continual neurological assessment in patients with lumbar spinal injury poses a challenge for effective management of pain associated with multiple fractured ribs. Two cases are presented to illustrate the benefits of using thoracic paravertebral block to control the pain of multiple fractured ribs without compromising the ongoing neurological assessment. Case Report Thoracic paravertebral block was used in 2 patients with concomitant multiple fractured ribs and lumbar spinal injury. Case 2 also had a head injury and there was moderate coagulopathy. The thoracic paravertebral catheter was placed in the upper thoracic region and radiological imaging was used to delineate spread before the injection of relatively small volumes (10 to 15 mL) of local anesthetic. In case 1, the thoracic paravertebral block produced ipsilateral segmental thoracic anesthesia, providing excellent pain relief for the fractured ribs. It also spared the lumbar and sacral nerve roots, preserving neurological function in the lower extremities and bladder sensation. In case 2, effective analgesia without systemic sedation and opioids resulted in the patient regaining consciousness, which allowed continuous assessment of central and peripheral neurological function. Conclusion Thoracic paravertebral block is an option for managing pain associated with multiple fractured ribs in the presence of concomitant lumbar spinal injury requiring continual neurological assessment.

The additive interactions between ondansetron and droperidol for preventing postoperative nausea and vomiting

Prophylactic ondansetron or droperidol reduces the incidence of postoperative nausea and vomiting (PONV). Previous studies showed that the combination of these two drugs produced better antiemetic effect than either drug alone. We present a nonparametric method to determine the pharmacologic interaction between ondansetron and droperidol and compared the observed response of the drug combination with that predicted from additivity. This is calculated as the product of the individual drug response, normalized to that of the controls. Five minutes before induction of anesthesia, 400 patients scheduled for laparoscopic gynecologic surgery were randomly assigned to receive 1) saline IV; 2) ondansetron 4 mg IV; 3) droperidol 1.25 mg IV; or 4) a combination of droperiodol 1.25 mg and ondansetron 4 mg IV. A standardized anesthetic technique and postoperative analgesic regimen were used. Patients were reviewed regularly for 48 h. Changes in the heart rate adjusted QT (QTc) interval were measured from electrocardiograms recorded before and 5 min after study drug administration. In a subgroup of 160 patients, QTc intervals were measured again at 2–3 h after surgery. During the first 48 h after the surgery, the proportion of patients experiencing PONV was 68% (95% CI 58–77) in the control group. A single dose of ondansetron or droperidol decreased the incidence of PONV to 30% (95% CI 21–40) and 28% (95% CI 20–38), respectively. The predicted incidence of PONV after drug combination, 11.8% (7.1–11.9), was similar to that observed, 12.1% (6.4–20.2), P = 0.94. The corresponding predicted and observed treatment responses in the combination group were 88.2% and 87.9%, respectively. There was a modest and transient increase in QTc interval after administration of ondansetron, droperidol, or their combination. The changes were however similar among groups. We conclude that the interaction between ondansetron and droperiodol was additive. Both drugs acted independently of each other through their specific mechanisms of action. The incidence of QTc prolongation did not increase with the drug combination.

Possible Interaction Between Sevoflurane and Aloe vera

OBJECTIVE To describe a patient with massive intraoperative bleeding after oral consumption of Aloe vera tablets. Case Summary A 35-year-old woman lost 5 L of blood during surgery as a result of a possible herb—drug interaction between Aloe vera and sevoflurane. DISCUSSION Aloe vera is a common herb used for antiinflammatory and antiarthritic activity, as well as antibacterial, hypoglycemic, and lipid-lowering effects. Compounds contained within Aloe vera can cause a reduction in prostaglandin synthesis, which may inhibit secondary aggregation of platelets. Sevoflurane inhibits thromboxane A2 formation by suppression of cyclooxygenase activity, impairs platelet aggregation, and prolongs bleeding. Although the vascularity and size of the hemangioma were the most important factors for the massive intraoperative blood loss, concomitant use of sevoflurane and Aloe vera played a contributory role. An objective causality assessment revealed that this adverse event was possible as a result of the sevoflurane and Aloe vera interaction. CONCLUSIONS There is a potential herb—drug interaction between Aloe vera and sevoflurane based on the antiplatelet effects of these 2 agents. Herbal medications with antiplatelet potential should be discontinued before anesthesia and surgery.

A prospective survey of patients after cessation of patient-controlled analgesia.

Cessation of IV patient-controlled analgesia (PCA) in the postoperative period is often an arbitrary clinical decision. We conducted a prospective survey of patients 24 h after cessation of IV PCA morphine to determine whether they wished to be restarted on PCA, and to evaluate factors affecting this decision. One hundred and fifteen patients were surveyed over a 3-mo period. Thirty-eight patients (33%) wished to restart PCA. The most common reason was the expectation that IV PCA would be more effective. Age, sex, type of surgery, duration of PCA use, side effects, pain scores, and reasons for cessation of PCA did not affect the decision. The reasons given by those who did not wish to restart PCA were minimal pain (51.9%), inconvenient PCA machine (15.6%), ineffective analgesia by IV PCA (11.7%), side effects during PCA (11.7%), and wishing to tolerate pain (7.8%). PCA morphine consumption in the 24-h period before cessation of PCA (mean [sd]) was larger in patients wishing to restart PCA than in those who did not (21.1 [14.8] mg vs 15.1 [15.1] mg;P < 0.05). In conclusion, the clinical decisions to cease IV PCA do not predict patient acceptance of and satisfaction with the decision and with subsequent pain treatment. Morphine consumption may predict a patient’s acceptance of ceasing PCA. Implications We surveyed patients 24 h after cessation of IV patient-controlled analgesia (PCA). This survey revealed that the usual clinical reasons to stop IV PCA might not be the most appropriate. Patients have different reasons why they wish to restart or not restart IV PCA. The cessation of PCA should be individualized.

Low dose mivacurium is less effective than succinylcholine in electroconvulsive therapy

PurposeTo compare the efficacy of low dose (LD) mivacurium (0.08 mg·kg−1) with LD succinylcholine (0.5 mgmg·kg−1) in modifying seizure activity during electroconvulsive therapy (ECT). Partial muscle relaxation is used in ECT to prevent violent muscle contractions. Current practice is to use LD succinylcholine which has several undesirable side effects.MethodSixteen depressed, but otherwise healthy, patients, aged 27–67 yr were studied. In a randomized, double-blind, cross-over study, either LD mivacurium or LD succinylcholine was given at consecutive ECTs 120 and 30 sec respectively before inducing ECT. Neuromuscular blockade following mivacurium was not reversed. Seizure modification was scored - 0 = no seizure activity, 1 = over-modified, 2 = desired level, 3 = under-modified, 4 = unmodified. Duration of seizures, time to first breath and adequate ventilation, ability to protrude tongue and sustain hand grip for five seconds were recorded. Paired t-tests and Wilcoxon matched pairs test were used to compare data.P < 0.05 was considered significant.ResultsSeizure modification was better (mean (range)) after succinylcholine 2.06(1–3) than after mivacurium 2.56(2–4) (P < 0.05). Mivacurium was unsatisfactory in eight cases compared with two cases after succinylcholine. The study was terminated early because of unsatisfactory seizure control. Clinical assessments of recovery from both relaxants were similar.ConclusionLow dose mivacurium is unsuitable for use in ECTRésuméObjectifComparer l’efficacité d’une faible dose (FD) de mivacurium (0,08 mgmg·kg−1) à celle d’une FD de succinylcholine (0,5 mgmg·kg−1) dans le but de modifier la crise convulsive pendant une sismothérapie par électrochoc (SPE). La relaxation musculaire partielle est utilisée lors de la SPE pour emp⊹her des contractions musculaires violentes. En général, c’est avec une FD de succinylcholine, mais elle présente quelques effets secondaires indésirables.MéthodeSeize patients déprimés, par ailleurs bien portants, âgés de 27 à 67 ans, ont été étudiés. Pendant l’étude randomisée, croisée et en double aveugle, on a administré une FD de mivacurium ou de succinylcholine, 120 et 30 s respectivement avant le début d’électrochocs consécutifs. Le blocage neuromusculaire qui a suivi l’administration de mivacurium n’a pas été renversé. La modification des convulsions a été notée comme suit : 0 = aucune crise convulsive, I = surmodification, 2 = niveau recherché, 3 = sous-modification, 4 = aucune modification. La durée des convulsions, le temps de parvenir à la première respiration et à la ventilation adéquate, l’habileté à tirer la langue et à serrer la main pendant cinq secondes ont été notés. On a utilisé le test t et le test d’appariement de Wilcoxon pour comparer les données.P < 0,05 a été considérée comme significative.RésultatsLa modification des convulsions a été meilleure (moyenne (limites)) après l’administration de succinylcholine 2,06 ( 1–3) qu’après l’administration de mivacurium 2,56 (2–4) (P < 0,05). Le mivacurium n’a pas été satisfaisant dans huit cas, mais la succinylcholine, dans deux cas. Létude a été rapidement abandonnée, puisque le contrôle des convulsions n’était pas satisfaisant. Les évaluations cliniques de la récupération à partir des deux relaxants ont été similaires.ConclusionUne faible dose de mivacurium n’est pas appropriée lors de la SPE.

Single-dose tropisetron for preventing postoperative nausea and vomiting after breast surgery.

In this randomized, double-blind, placebo-controlled study, we compared the efficacy of tropisetron 5 mg with tropisetron 2 mg for the prevention of postoperative nausea and vomiting (PONV) after breast surgery. One hundred forty-eight female patients were randomized to receive either tropisetron 5 mg (n = 49), tropisetron 2 mg (n = 49), or saline (n = 50) before the induction of anesthesia with thiopental and morphine. Anesthesia was maintained with nitrous oxide and isoflurane. Postoperative analgesia was provided by patient-controlled analgesia with IV morphine. The incidence of PONV, the pain score, and the analgesic requirement were recorded for 48 h. There was no difference among groups in patient characteristics, risk factors for PONV, morphine consumption, or side effects. During the first 6 h postoperatively, the incidence of PONV after tropisetron 2 mg and 5 mg were similar and were superior to placebo (P < 0.001). After 6 h, the incidence of PONV increased significantly in patients who had received tropisetron 2 mg (P = 0.01) and was greater than that in patients who had received tropisetron 5 mg (P = 0.001). We conclude that single-dose tropisetron 5 mg is more effective than tropisetron 2 mg in the prevention of PONV after breast surgery. Implications: Breast surgery is associated with a high incidence of postoperative nausea and vomiting. A single dose of IV tropisetron 5 mg is well tolerated and decreases the number of vomiting and nausea episodes after surgery. (Anesth Analg 1998;87:931-5)

Subcutaneous emphysema, pneumomediastinum and pneumothorax complicating laparoscopic vagotomy. Report of two cases.

Two patients developed subcutaneous emphysema and pneumomediastinum during laparoscopic vagotomy. One of the patients also had a pneumothorax which produced a sudden increase in end‐tidal carbon dioxide concentration preceding arterial oxygen desaturation. The pneumothorax was drained with an intercostal cannula. The patient required a twofold increase in minute ventilation to maintain normocarbia, probably because of the additional absorption of carbon dioxide through the pleural cavity. Despite the presence of a peritoneopleural communication, surgery was successfully completed. We believe that gas under tension in the peritoneal cavity dissected along tissue planes around the oesophagus opened up during surgery. Thus pneumomediastinum, subcutaneous emphysema and pneumothorax are definite risks associated with this new procedure.

Performance of an oxygen delivery device for weaning potentially infectious critically ill patients

Oxygen delivery via a heat and moisture exchange filter with an attached T‐shaped reservoir satisfies infection control requirements of high efficiency bacterial and viral filtration and low gas flows. In order to assess the performance of such a device in critically ill patients being weaned from mechanical ventilation, we simulated 16 patients using a human patient simulator, measuring fractional inspired oxygen and carbon dioxide concentrations and work of breathing at three oxygen flow rates. Oxygen concentration was dependent on peak inspiratory flow rate, tidal volume and oxygen flow rate. Rebreathing, as indicated by inspired carbon dioxide concentration, was greatest at high respiratory rates and low tidal volumes. Imposed inspiratory work of breathing was relatively high (mean 0.88 J.l−1[SD 0.30]). We conclude that this method of oxygen delivery is only suitable for patients in whom rapid extubation is anticipated.

Postpartum patients have slightly prolonged neuromuscular block after mivacurium.

Postpartum patients have decreased plasma cholinesterase activity, which may slow the metabolism of mivacurium.We compared the duration of a mivacurium neuromuscular block in 11 women undergoing postpartum tubal ligation 36-99 h after delivery with that in 11 control women undergoing gynecological surgery. Anesthesia was induced with propofol and fentanyl and maintained with propofol and nitrous oxide. Neuromuscular block was monitored by electromyography, and the ulnar nerve was stimulated transcutaneously using a train-of-four pattern. Patients received a bolus dose of mivacurium 0.15 mg/kg. The median (range) duration of neuromuscular block until 25% recovery of the first twitch response was longer in the postpartum group, 19.4 (15.6-25.2) min, compared with the control group, 16.3 (11.0-23.4) min (P = 0.04). The median (range) plasma cholinesterase activity was decreased in the postpartum group, 4.0 (0.1-5.5) kU/L, compared with the control group, 7.1 (6.2-10.0) kU/L (P < 0.001). The duration of neuromuscular block was inversely correlated with cholinesterase activity (Kendall rank correlation tau = -0.43, P = 0.005). The slight prolongation of neuromuscular block should not be significant clinically. Implications: Postpartum patients have decreased amounts of the plasma cholinesterase enzyme. This would slow the metabolism of the muscle relaxant mivacurium. However, the duration of muscle paralysis is only prolonged by approximately 3 min, which would not normally cause any significant problems.