Severity of airway hyperreactivity associated with laryngeal mask airway removal: correlation with volatile anesthetic choice and depth of anesthesia.

STUDY OBJECTIVE: To compare the influence of anesthetic depth and choice of volatile anesthetic drug on the incidence and severity of airway hyperreactivity associated with Laryngeal Mask Airway (LMA) removal. DESIGN: Randomized observer-blinded study. SETTING: Ambulatory Surgical Center at a University Medical Center. PATIENTS: 123 ASA physical status I and II children undergoing infraumbilical procedures. INTERVENTIONS: Patients were randomly assigned to one of four treatment groups: Group 1 = anesthetic induction with halothane, maintenance with isoflurane, nitrous oxide (N(2)O), and oxygen (O(2)), LMA removed when child awakened; Group 2 =anesthetic induction and maintenance as in Group 1, LMA removed while child anesthetized with age adjusted 2 minimum alveolar concentration (MAC) end-tidal concentration of isoflurane; Group 3 = anesthetic induction and maintenance with sevoflurane, N(2)O, and O(2), LMA removed when child awakened; Group 4 = anesthetic induction and maintenance as in Group 3, but LMA removed while child anesthetized with age-adjusted 2 MAC end-tidal concentration of sevoflurane. MEASUREMENTS AND MAIN RESULTS: Severity of airway hyperreactivity was graded as mild, moderate, or severe. A significant difference was not found amongst the four groups with respect to mild and moderate airway hyperreactivity. Severe airway hyperreactivity leading to a critical event [partial or complete laryngospasm with oxygen saturation (SPO(2)) < 85%] was only encountered in Group 1 patients (incidence 13%). Adverse airway events (SPO(2) < 90%, vomiting and bronchospasm) were also significantly higher in Group 1 (p < 0.05). Isoflurane use was independently associated with significantly higher airway hyperreactivity when compared with sevoflurane (p < 0.05). CONCLUSIONS: Depth of anesthesia during LMA removal does not appear to affect the incidence or severity of airway hyperreactivity when sevoflurane is the maintenance anesthetic. However, awake LMA removal during isoflurane anesthesia results in a higher incidence of adverse airway events and carries the risk of severe airway hyperreactivity.

The anesthetic and recovery profile of two doses (60 and 80 mg) of plain mepivacaine for ambulatory spinal anesthesia.

UNLABELLED: Reports of transient neurological symptoms with the use of subarachnoid lidocaine has generated interest in alternate local anesthetics of intermediate duration, such as mepivacaine. This prospective randomized, double-blinded, dose-response study examined the anesthetic and recovery profiles of 60- and 80-mg doses of preservative-free plain mepivacaine for ambulatory spinal anesthesia. Sixty patients undergoing ambulatory anterior cruciate ligament repair of the knee under spinal anesthesia were randomized into two groups; Group 1 (29 patients) received 4 mL of 1.5% (60-mg dose) and Group 2 (31 patients) received 4 mL of 2% (80-mg dose) of plain mepivacaine. All patients received a combined spinal-epidural anesthetic technique. The epidural catheter was used only in the event the surgery outlasted the duration of surgical anesthesia with subarachnoid mepivacaine. Epidural supplementation was administered in three patients (12%) in Group 1 and one patient (3%) in Group 2 when the sensory block regressed to L-1 with surgery expected to last longer than 15 min. The cephalad dermatome level of the block and degree of motor block was comparable in the two groups. Times to two-segment and T-10 regression were comparable in the two groups (112 +/- 26 min in Group 1 versus 122 +/- 28 min in Group 2). Time to L-1 regression was significantly longer in Group 2 (146 +/- 28 min in Group 1 versus 159 +/- 19 min in Group 2). All of the ambulatory milestones were significantly faster in Group 1. Side effects, such as hypotension and emesis were negligible, severe bradycardia and urinary retention did not occur, and none of the patients in the two groups reported transient neurological symptoms over 24 h. In conclusion, plain mepivacaine in a 60- or 80-mg dose is a suitable local anesthetic choice for ambulatory spinal anesthesia with respect to anesthetic, as well as recovery profiles. IMPLICATIONS: We evaluated the anesthetic and recovery profiles of 60- and 80-mg doses of plain mepivacaine for ambulatory spinal anesthesia. Both doses produced comparable sensory and motor block. Sensory and motor regression and ambulatory milestones were 20-30 min longer with the 80-mg dose. Side effects were negligible and transient neurological symptoms were not reported during a 24-h follow-up.

Is succinylcholine after pretreatment with d-tubocurarine and lidocaine contraindicated for outpatient anesthesia?

UNLABELLED: Because succinylcholine has obvious advantages for facilitating endotracheal intubation in the ambulatory setting (e.g., low cost, fast onset, and no need for reversal of neuromuscular block), it is important to determine whether this muscle relaxant is indeed associated with an increased incidence of postoperative myalgias, compared with alternative but more expensive nondepolarizing muscle relaxants. We studied 119 outpatients undergoing endoscopic nasal sinus surgery or septoplasty. The anesthetic technique consisted of propofol/lidocaine for induction, followed by isoflurane/nitrous oxide/oxygen for maintenance. Oral tracheal intubation was performed by using a fiberscope. Patients were randomly assigned to one of two muscle relaxant groups. Group 1 patients received d-tubocurarine 3 mg followed by succinylcholine 1.5 mg/kg. Group 2 patients received mivacurium 0.2 mg/kg. After recovery from anesthesia, patients were asked whether they had any muscle pain and/or stiffness. Pain was categorized by location and quantified by using a verbal scale (from 0 to 10). Analgesic usage and myalgias limiting ambulation were recorded. After discharge from the ambulatory surgery unit, patients were contacted by telephone on Postoperative Day 1. If patients complained of myalgias, they were contacted by telephone on Days 2 and 3. Only one patient (in the mivacurium-treated group) reported myalgia as a limiting factor in ambulation or resumption of normal activity. There were no differences between groups with respect to the incidence (21% in the succinylcholine-treated group and 18% in the mivacurium-treated group), location, or severity of myalgia. In conclusion, succinylcholine (preceded by pretreatment with d-tubocurarine and lidocaine) is not associated with an increased incidence of myalgias, compared with mivacurium, when used to facilitate tracheal intubation in patients undergoing ambulatory nasal surgery. IMPLICATIONS: The results of this study show that the frequency of muscle pains after surgery in outpatients is approximately 20%, regardless of whether succinylcholine (after precurarization) or mivacurium is used to assist in insertion of the breathing tube.

Propofol versus propofol-ketamine sedation for retrobulbar nerve block: comparison of sedation quality, intraocular pressure changes, and recovery profiles.

UNLABELLED: We compared sedation quality, intraocular pressure (IOP) changes, and recovery profiles in patients who received propofol or propofol-ketamine sedation during placement of the retrobulbar nerve block (RBB). Seventy elderly patients undergoing cataract extraction according to a prospective, randomized, double-blinded protocol were preoperatively evaluated with a Mini-Mental State examination and baseline IOP. A hypnotic dose was provided with either propofol (Group P) or a propofol-ketamine (Group PK) combination. The IOP measurement was repeated, and the surgeon initiated the RBB. Supplemental study drug was given if needed. The level of sedation was considered acceptable if the patient exhibited minimal or no movement and grimacing with needle insertion. Patients were evaluated in terms of quality of sedation, cardiopulmonary stability, and recovery profile. Compared with patients in Group P, patients in Group PK had a significantly faster onset of acceptable sedation (Group P 235 +/- 137 s versus Group PK 164 +/- 67 s) and required significantly less supplemental sedation (Group P 1.1 +/- 1.9 mL versus Group PK 0.15 +/- 0.3 mL). Additionally, none of the Group PK patients required ventilatory assistance, but two patients in Group P required assisted mask ventilation. In conclusion, the addition of ketamine (13.2 +/- 3.3 mg) to propofol (44 +/- 11 mg) decreased the hypnotic requirement and improved the quality of sedation without prolonging recovery. IMPLICATIONS: Anesthesiologists frequently perform retrobulbar blocks while simultaneously providing sedation. Using ketamine to supplement propofol sedation provided a faster onset and improved the quality of sedation during the retrobulbar block procedure.

The effect of preoperative dexamethasone on the immediate and delayed postoperative morbidity in children undergoing adenotonsillectomy.

UNLABELLED: In this prospective, randomized, double-blind, placebo-controlled study, we examined the effect of preoperative dexamethasone on postoperative nausea and vomiting (PONV) and 24-h recovery in children undergoing tonsillectomy. One hundred thirty children, 2-12 yr of age, ASA physical status I or II, completed the study. All children received oral midazolam 0.5-0.6 mg/kg preoperatively. Anesthesia was induced with halothane and nitrous oxide in 60% oxygen and maintained with nitrous oxide and isoflurane. Intubation was facilitated by mivacurium 0.2 mg/kg. Each child received fentanyl 1 microgram/kg i.v. before initiation of surgery, as well as dexamethasone 1 mg/kg (maximal dose 25 mg) (steroid group) or an equal volume of saline (control group). Intraoperative fluids were standardized to 25-30 mL/kg lactated Ringer's solution. All tonsillectomies were performed under the supervision of one attending surgeon using an electrodissection technique. Postoperatively, fentanyl and acetaminophen with codeine elixir were administered as needed for pain. Rescue antiemetics were administered when a child experienced two episodes of retching and/or vomiting. Before home discharge, the incidence of PONV, need for rescue antiemetics, quality or oral intake, and analgesic requirements did not differ between groups. However, during the 24 h after discharge, more patients in the control group experienced PONV (62% vs 24% in the steroid group) and complained of poor oral intake. Additionally, more children in the control group (8% vs 0% in the steroid group) returned to the hospital for the management of PONV and/or poor oral intake. The preoperative administration of dexamethasone significantly decreased the incidence of PONV over the 24 h after home discharge in these children. IMPLICATIONS: In this double blind, placebo-controlled study, we examined the efficacy of a single large dose (1 mg/kg; maximal dose 25 mg) of preoperative dexamethasone on posttonsillectomy postoperative nausea and vomiting (PONV) in children 2-12 yr of age undergoing tonsillectomy. Compared with placebo, dexamethasone significantly decreased the incidence of PONV in the 24 h after discharge, improved oral intake, decreased the frequency of parental phone calls, and resulted in no hospital returns for the management of PONV and/or poor oral intake.

Recovery after propofol with and without intraoperative fentanyl in patients undergoing ambulatory gynecologic laparoscopy.

This prospective, randomized double-blind study was conducted to examine the effect of intraoperative opioid (fentanyl) supplementation on postoperative analgesia, emesis, and recovery in ambulatory patients receiving propofol-nitrous oxide anesthesia. Eighty patients undergoing ambulatory gynecologic laparoscopy participated. Confounding variables that could influence the incidence of postoperative emesis were controlled. Patients received either fentanyl 100 micrograms (Group I) or ketorolac 60 mg (Group II) intravenously (IV) at the time of anesthetic induction. No further analgesic supplements were given intraoperatively. Anesthesia was induced with propofol and maintained with propofol-nitrous oxide. Atracurium was used for muscle relaxation and reversed with neostigmine and glycopyrrolate. Postoperative pain during early recovery was treated with IV fentanyl 25-50 micrograms (Group I) or IV ketorolac 15-30 mg (Group II). Subsequent breakthrough pain in both groups was treated with IV fentanyl 25 micrograms increments as needed (rescue analgesia). Eighty-four percent of patients in Group I required analgesics during early recovery versus 56% of patients in Group II (P < 0.05). Maintenance dose of propofol was significantly lower in Group I (129 +/- 35 micrograms.kg-1.min-1 than in Group II (170 +/- 63 micrograms.kg-1.min-1. Immediate recovery (emergence) in the two groups was comparable, despite different propofol requirements. Although the incidence of emetic sequelae in the postanesthesia care unit was not significantly different between the two treatment groups, a significantly larger number of patients in Group I (fentanyl group) had emetic sequelae that required therapeutic intervention (Group I 29% versus Group II 10%). Patients in Group I also took a significantly longer time to ambulate and meet criteria for home discharge. These results indicate that, in patients undergoing ambulatory gynecologic laparoscopy, the practice of administering a small dose of fentanyl at the time of anesthetic induction reduces maintenance propofol requirement, but fails to provide effective postoperative analgesia. Fentanyl administration at anesthetic induction increased the need for rescue antiemetics. The relative severity of emetic sequelae could have contributed to delay in ambulation and discharge.

Central hemodynamic changes associated with pregnancy in a long-term cardiac transplant recipient.

We present a case of pregnancy in a woman who had undergone cardiac transplantation and was monitored by "surveillance" biopsy at intervals during the entire course of pregnancy and the immediate postpartum period. Exercise reserve remained normal during these periods despite angiographic evidence of coronary disease and episodes of rejection. Central hemodynamic changes were similar to those expected during normal pregnancy. Hemodynamic stability was maintained during epidural anesthesia for labor and subsequent cesarean section.

Tourniquet-induced exsanguination in patients requiring lower limb surgery. An ischemia-reperfusion model of oxidant and antioxidant metabolism.

BACKGROUND: Surgically induced ischemia and reperfusion is frequently accompanied by local and remote organ injury. It was hypothesized that this procedure may produce injurious oxidants such as hydrogen peroxide (H2O2), which, if unscavenged, will generate the highly toxic hydroxyl radical (.OH). Accordingly, it was proposed that tourniquet-induced exsanguination for limb surgery may be a useful ischemia-reperfusion model to investigate the presence of oxidants, particularly H2O2. METHODS: In ten patients undergoing knee surgery, catheters were placed in the femoral vein of the limb operated on for collection of local blood and in a vein of the arm for sampling of systemic blood. Tourniquet-induced limb exsanguination was induced for about 2 h. After tourniquet release (reperfusion), blood samples were collected during a 2-h period for measurement of H2O2, xanthine oxidase activity, xanthine, uric acid (UA), glutathione, and glutathione disulfide. RESULTS: At 30 s of reperfusion, H2O2 concentrations increased (approximately 90%) from 133 +/- 5 to 248 +/- 8 nmol.ml-1 (P < 0.05) in local blood samples, but no change was evident in systemic blood. However, in both local and systemic blood, xanthine oxidase activity increased approximately 90% (1.91 +/- 0.07 to 3.93 +/- 0.41 and 2.19 +/- 0.07 to 3.57 +/- 0.12 nmol UA.ml-1.min-1, respectively) as did glutathione concentrations (1.27 +/- 0.04 to 2.69 +/- 0.14 and 1.27 +/- 0.03 to 2.43 +/- 0.13 mumol.ml-1, respectively). At 5 min reperfusion, in local blood, H2O2 concentrations and xanthine oxidase activity peaked at 796 +/- 38 nmol.ml-1 (approximately 500%) and 11.69 +/- 1.46 nmol UA.ml-1.min-1 (approximately 520%), respectively. In local blood, xanthine and UA increased from 1.49 +/- 0.07 to 8.36 +/- 0.33 nmol.ml-1 and 2.69 +/- 0.16 to 3.90 +/- 0.18 mumol.ml-1, respectively, whereas glutathione and glutathione disulfide increased to 5.13 +/- 0.36 mumol.ml-1 and 0.514 +/- 0.092 nmol.ml-1, respectively. In systemic blood, xanthine oxidase activity peaked at 4.75 +/- 0.20 UA nmol.ml-1.min-1. At 10 min reperfusion, local blood glutathione and UA peaked at 7.08 +/- 0.46 mumol.ml-1 and 4.67 +/- 0.26 mumol.ml-1, respectively, while the other metabolites decreased significantly toward pretourniquet levels. From 20 to 120 min, most metabolites returned to pretourniquet levels; however, local and systemic blood xanthine oxidase activity remained increased 3.76 +/- 0.29 and 3.57 +/- 0.37 nmol UA.ml-1.min-1, respectively. Systemic blood H2O2 was never increased during the study. During the burst period (approximately 5-10 min), local blood H2O2 concentrations and xanthine oxidase activities were highly correlated (r = 0.999). CONCLUSIONS: These studies suggest that tourniquet-induced exsanguination for limb surgery is a significant source for toxic oxygen production in the form of H2O2 and that xanthine oxidase is probably the H2O2-generating enzyme that is formed during the ischemia-reperfusion event. In contrast to the reperfused leg, the absence of H2O2 in arm blood demonstrated a balanced oxidant scavenging in the systemic circulation, despite the persistent increase in systemic xanthine oxidase activity.

Chloral hydrate sedation of children undergoing CT and MR imaging: safety as judged by American Academy of Pediatrics guidelines.

OBJECTIVE: The purpose of this prospective study was to determine the frequency of adverse events associated with supplemented and unsupplemented chloral hydrate sedation in a select group of children undergoing CT or MR imaging using the revised American Academy of Pediatrics (AAP) monitoring and management guidelines for pediatric sedation. The AAP guidelines do not recommend drug selection or dosages but define patient selection, discharge criteria, and monitoring standards for sedating children. SUBJECTS AND METHODS: This prospective study included 410 children 4 years of age or younger who were scheduled for CT and MR imaging as outpatients. Selected children were physical status 1 or 2 as determined by the American Society of Anesthesiologists physical status classification and had no contraindications to sedation per our institutional sedation policy. Children younger than 1 year old received only oral incremental doses of chloral hydrate. Children 1-4 years old received hydroxyzine plus incremental doses of chloral hydrate. Children between 2 and 4 years old who were not satisfactorily sedated 30 min after hydroxyzine plus incremental chloral hydrate were given 2 mg/kg meperidine intramuscularly, with a maximum dose of 50 mg. All children were monitored according to the revised guidelines recommended by the committee on drugs of the AAP. Vital signs and arterial hemoglobin oxygen saturation (SpO2) were monitored continuously by registered nurses trained in pediatric advanced life support from the time of sedative drug administration until the recommended discharge criteria were met. RESULTS: Mild hypoxia (SpO2, 90-95%) that resolved spontaneously without any therapeutic intervention was seen in 9% of the chloral hydrate group and in 5% of the chloral hydrate-hydroxyzine group. One child in the chloral hydrate group had severe hypoxia (SpO2, 85-89%), and one child in the chloral hydrate-hydroxyzine group had moderate hypoxia (SpO2, < 85%). Both required therapeutic intervention. In both cases, the severity of the underlying medical disease was underestimated at the time of presedation medical screening. The success rate of sedation was 100% for all the children having CT. For those having MR imaging, success was 100% for children 1-4 years old and 97% for children less than 1 year old. CONCLUSION: Use of supplemented and unsupplemented chloral hydrate sedation provides effective and safe sedation in children if the AAP guidelines for patient selection, monitoring, and management are followed. Careful medical screening and patient selection by knowledgeable medical personnel is important to exclude patients at high risk for life-threatening hypoxia. Monitoring with AAP guidelines is essential for prompt detection and management of life-threatening hypoxia.

Propofol for ambulatory gynecologic laparoscopy: does omission of nitrous oxide alter postoperative emetic sequelae and recovery?

The role of nitrous oxide in postoperative emesis is controversial. This prospective randomized study was performed to compare the emetic sequelae and quality of recovery between a group of patients anesthetized with propofol alone and a group anesthetized with propofol plus nitrous oxide. Seventy patients, ASA grade I or II, scheduled for ambulatory gynecologic laparoscopy under general anesthesia were included. Most factors which could influence the incidence of postoperative emesis were controlled. The overall incidence of emetic sequelae during the first 24 h postoperatively was 25% in the group anesthetized with propofol alone versus 29% for the group anesthetized with propofol and nitrous oxide. The incidence of emetic sequelae requiring therapeutic intervention was 13% and 6%, respectively. This difference was not statistically significant. The group of patients who received propofol alone required an average propofol dose of 221.5 +/- 71.9 micrograms.kg-1.min-1 to maintain anesthesia compared with 162.5 +/- 43.9 micrograms.kg-1.min-1 for the group receiving propofol plus nitrous oxide (P < 0.001). The time from discontinuation of propofol to eye-opening and orientation was significantly longer in patients anesthetized with propofol alone. Otherwise, the recovery variables were comparable between the two groups. We conclude that supplementing propofol with nitrous oxide in patients undergoing ambulatory laparoscopy reduces the requirements of propofol, expedites immediate recovery (emergence), and does not increase the incidence of postoperative emesis. This tends to confirm that there is no clinical advantage to omitting nitrous oxide.

Lidocaine disposition following intravenous regional anesthesia with different tourniquet deflation technics.

It has been claimed that tourniquet cycling, cyclic deflation and reinflation of the tourniquet at the termination of intravenous regional anesthesia (IVRA), enhances the safety of IVRA by minimizing the peak blood level of local anesthetics. To evaluate the validity of these claims and to determine the optimal cycling technic, peak arterial (Cmax) plasma concentrations of lidocaine were determined as well as the time to reach these peaks (Tmax) utilizing contralateral radial arterial blood samples in three groups of volunteers after 30 minutes of IVRA: In all three groups IVRA was induced with 3 mg/kg of lidocaine and maintained for 30 min. In the first group the tourniquet was then simply deflated once (and not reinflated); in the second group the tourniquet was deflated three times with variable periods of deflation (0, 10 and 30 seconds) separated by 1-minute periods of reinflation; and in the third group the tourniquet was again deflated 3 times but with fixed periods of deflation (10 sec) separated by 1 min periods of reinflation. The results obtained indicate that cycling technics do not appear to significantly reduce Cmax, but they do significantly prolong Tmax. Of the two cycling technics, the 10-second deflation interval technic appeared to be superior, both clinically and pharmacologically, as it was associated with less venous congestion and therefore less discomfort, and it sequentially decreased the arterial plasma concentration of lidocaine with each subsequent deflation-reinflation cycle.

Anesthetic management of the newborn.

Advances in monitoring technology, the availability of special skill, and training has resulted in the improved perioperative care of the newborn. With the coordinated efforts of pediatric anesthesiologists, pediatric surgeons, and neonatologists, safe anesthesia and surgery have become a reality even in a sick 500-gm premature infant. Fortunately for these nonverbal neonates, the personnel involved in this perioperative care are now more sensitive to their analgesic and anesthetic needs. With adequate preoperative preparation and intraoperative monitoring, safe anesthesia at present can be provided to most critically ill neonates, using the guidelines outlined above. In addition, the postoperative period also can be made pain free for them by a judicious selection of analgesic and local anesthetic drugs.

Clinical pharmacokinetics of carbonated local anesthetics. III: Interscalene brachial block model.

To compare serum levels of lidocaine resulting from 1.1% lidocaine carbonate and 1.0% lidocaine hydrochloride, the two salts were administered to ten healthy adult patients undergoing upper extremity surgery under interscalene brachial plexus block. Epinephrine (1:200,000) was added to both the solutions just prior to injection, and, following performance of the blocks, venous blood samples were drawn at 3, 5, 10, 15, 20, 30, 60 and 120 minutes. The concentration of lidocaine tended to rise more rapidly and to achieve higher levels in the first 10 minutes following injection of the carbonated lidocaine. However, no significant differences were found in the parameters of Cmax, Tmax or AUC for the two salts, and the serum levels in both groups at all times were well below the levels known to produce systemic toxicity. Therefore, while previous studies appear to indicate that the carbonate salt enhances diffusion, penetration, and uptake of neural tissues as compared with the hydrochloride salt, the present study indicates that vascular uptake is not similarly affected.