µ-opioid receptor genetic polymorphisms and duration of epidural fentanyl analgesia during early labor.

BACKGROUND: Epidural fentanyl is commonly used for initiation of early labor analgesia. The aim of this prospective study is to test the hypothesis that duration of epidural fentanyl analgesia differs in nulliparous women requesting epidural analgesia in early labor who are variant allele carriers of the OPRM1 SNVs 118A>G rs1799971, IVS2+31G>A rs9479757, and IVS2+691G>C rs2075572. METHODS: Two hundred and twenty parturients who received epidural analgesia with fentanyl were included in the 118A>G analysis, and a 196 sub-cohort was included in the IVS2+31G>A and IVS2+691G>C exploratory analysis. Peripheral blood DNA was genotyped using Taqman allele discrimination assays. RESULTS: One hundred and seventy-four subjects (79%; 95% CI: 74-84) were homozygous for the wild type OPRM1 118A>G SNV (AA), and forty-six subjects (21%; 95% CI: 16-26) were heterozygous AG (N.=40) or homozygous GG (N.=6) for the variant allele. The minor allele frequency (MAF) was hence 12%. The MAFs for the IVS2+31G>A and IVS2+691G>C SNVs in the sub-cohort of 196 participants were 5% and 59% respectively. There was no significant difference in duration of epidural fentanyl analgesia for the three SNVs (161±68 and 143±51 min for wild type and allele carriers of the 118A>G SNV respectively [P=0.08]). Similarly, no significant differences were shown with the visual analog scale scores, side effects, and satisfaction for each of the three SNVs. CONCLUSIONS: OPRM1 SNVs did not affect the duration of epidural fentanyl administered for early labor analgesia in nulliparous women. These results should be confirmed in patients receiving epidural opioids in other clinical settings.

Femoral arterial cannulation performed by residents: a comparison between ultrasound-guided and palpation technique in infants and children undergoing cardiac surgery.

BACKGROUND: Percutaneous cannulation of the femoral artery in the pediatric age group can be technically challenging, especially when performed by residents in training. OBJECTIVE: We examined whether the use of real-time ultrasound guidance is superior to a palpation landmark technique for femoral artery catheterization in children undergoing heart surgery. METHODS: Patients were prospectively randomized into two groups. In the palpation group, the femoral artery was cannulated using the traditional landmark method of palpation of arterial pulse. In the ultrasound group, cannulation was guided by real-time scanning with an ultrasound probe. Ten minutes were set as time limit for the resident's trials during which the time taken for attempted cannulation (primary outcome), number of attempts, number of successful cannulations on first attempt, and success rate were compared between the two groups. Adverse events were monitored on postoperative days 1 and 3. RESULTS: A total of 106 patients were included in the study. The time taken for attempted femoral artery cannulation was shorter (301 ± 234 vs 420 ± 248 s; difference in mean: 119; 95% confidence interval (CI) of difference: 26-212; P = 0.012) and the number of attempts was lower [1 (1-10) vs 2 (1-5); difference in median: 1, 95% CI of difference: 0.28-1.72; P = 0.003] in the ultrasound group compared with the palpation group. The number of successful cannulations on first attempt was higher in the ultrasound group compared with palpation group [24/53 (45%) vs 13/53 (25%); odds ratio (OR): 2.54, 95% CI: 1.11-5.82; P = 0.025]. The number of patients who had successful cannulation was 31 of 55 (58%) in the palpation group and 40 of 53 (75%) in the ultrasound group (OR: 2.18, 95% CI: 0.95-5.01; P = 0.06). None of the patients had adverse events at days 1 and 3. CONCLUSIONS: Ultrasound-guided femoral arterial cannulation in children when performed by anesthesia residents is superior to the palpation technique based on the reduction of the time taken for attempted cannulation and the number of attempts, and improvement in first attempt success.

Fentanyl-induced cough--pathophysiology and prevention.

Many reports have demonstrated that intravenous administration of a bolus of fentanyl at induction of anesthesia can cause coughing with varying degrees. This cough can be benign, but sometimes it causes undesirable side effects including an increase in intraabdominal, intracranial or intraocular pressure. Many studies demonstrated that the incidence and severity of fentanyl-induced cough could be related to age, ethnicity, history of smoking, as well as to the rate, route, dose and concentration of fentanyl administered. This cough was described by several mechanisms including an inhibition of central sympathetic system leading to vagal predominance, reflex bronchonstriction after the stimulation of tracheobronchial tree receptors, or histamine release. The efficacy of several measures to avoid fentanyl-induced cough have been demonstrated, and several anesthetics adjuncts can be given prior to fentanyl administration aiming at decreasing this unwanted side effect.

A randomized controlled trial of variable rate phenylephrine infusion with rescue phenylephrine boluses versus rescue boluses alone on physician interventions during spinal anesthesia for elective cesarean delivery.

BACKGROUND: Phenylephrine infusion is used to reduce hypotension during spinal anesthesia for cesarean delivery. A prophylactic fixed rate infusion regimen may not improve hemodynamic control; a variable rate regimen adjusted in response to changes in arterial blood pressure and heart rate may allow more accurate maintenance of baseline blood pressure. We hypothesized that a combination of crystalloid solution coload with a variable rate phenylephrine infusion and phenylephrine rescue boluses may be associated with fewer physician interventions needed to maintain maternal systolic blood pressure within 20% of baseline and greater hemodynamic stability than crystalloid solution coload with phenylephrine rescue boluses alone. METHODS: In this prospective, double-blind study, 80 patients received a coload with 15 mL/kg lactated Ringer's solution immediately after the initiation of spinal anesthesia. Patients were randomized to receive a prophylactic variable rate phenylephrine infusion starting at 0.75 µg/kg/min (group P) or infusion of normal saline (group S). Maternal systolic blood pressure was maintained within 20% of baseline with rescue phenylephrine boluses using a preset algorithm. During the predelivery period, the number of physician interventions (primary outcome), hemodynamic performance, nausea/vomiting, and umbilical cord blood gas values were compared between the groups. RESULTS: One patient from group S was excluded due to protocol violation. Therefore, group P included 40 patients and group S 39 patients. The median (range) number of physician interventions needed to maintain maternal hemodynamics within the target range (0 [0-6] vs 3 [0-9], difference in median: 3, 95% confidence interval of difference: 2-4) and incidence of hypotension (8/40 [20%] vs 35/39 [90%]) were lower in group P compared with group S (P < 0.001). Group P had a higher incidence of hypertension compared with group S (6/40 [15%] vs 0/39 [0%], P = 0.026). The median performance error was closer to baseline (P < 0.001) with a smaller median absolute performance error (P = 0.001) in group P versus group S. In group P, 4/40 (10%) patients had nausea/vomiting compared with 17/39 (44%) in group S (P = 0.001). The number needed to treat was 1.4 women to prevent 1 case of hypotension, and 3 women to prevent 1 case of nausea/vomiting; the rate of hypertension was 1 case per 6.7 women treated. Neonatal outcomes were not different between the 2 groups. CONCLUSION: Prophylactic variable rate phenylephrine infusion and rescue phenylephrine bolus dosing is more effective than relying on rescue phenylephrine bolus dosing with respect to limiting clinician workload and maternal symptoms during spinal anesthesia for cesarean delivery.

A randomized trial comparing colloid preload to coload during spinal anesthesia for elective cesarean delivery.

BACKGROUND: Hypotension after spinal anesthesia for cesarean delivery is common. Previous studies have demonstrated that a crystalloid fluid "coload" (rapid administration of a fluid bolus starting at the time of intrathecal injection) is superior to the conventional crystalloid preload (fluid administered before the intrathecal injection) for preventing hypotension. Colloid preload provides a sustained increase in central blood volume. We hypothesized that, in contrast to crystalloid, a colloid preload may be more effective than colloid coload for reducing the incidence of spinal anesthesia-induced hypotension. METHODS: In this double-blind study, 178 patients were randomly assigned to receive a preload of 500 mL of hydroxyethyl starch over a period of 15-20 min before initiation of spinal anesthesia (n = 90) or an identical fluid bolus of hydroxyethyl starch starting at the time of identification of cerebrospinal fluid (n = 88). Vasopressors (ephedrine or phenylephrine) were administered if systolic arterial blood pressure decreased less than 80% of the baseline pressure and <100 mm Hg, or with smaller decreases in blood pressure if accompanied by nausea, vomiting, or dizziness. The primary outcome was the incidence of hypotension (defined as the administration of at least one dose of vasopressor). RESULTS: There was no significant difference between the groups in the incidence of hypotension (68% in preload group and 75% in coload group, 95% confidence interval of difference -6%-20%; P = 0.28), doses of ephedrine and phenylephrine, and number of vasopressor unit doses. The incidence of severe hypotension (systolic blood pressure <80 mm Hg) was 16% in the preload group and 22% in the coload group (P = 0.30). There were no differences in the incidence of nausea and/or vomiting, or neonatal outcome between the groups. CONCLUSION: There was no difference in the incidence of hypotension in women who received colloid administration before the initiation of spinal anesthesia compared with at the time of initiation of anesthesia. Both modalities are inefficient as single interventions to prevent hypotension.

Excellent intubating conditions with remifentanil-propofol and either low-dose rocuronium or succinylcholine.

PURPOSE: The shortest time to tracheal intubation, the best intubating conditions, and the shortest duration of muscle paralysis are achieved with succinylcholine. During a lidocaine-remifentanil-propofol induction of anesthesia, we compared intubating conditions 90 s after administering low-dose rocuronium (0.3 mg . kg(-1)) with intubating conditions 60 s after administering succinylcholine 1.5 mg . kg(-1). METHODS: The randomized double-blind study included 184 healthy adult patients scheduled for elective surgery. Anesthesia was induced in all patients with lidocaine 1.5 mg . kg(-1), remifentanil 2 microg . kg(-1), and propofol 2 mg . kg(-1) administered over 30 s. In one group, rocuronium 0.3 mg . kg(-1) was administered before the induction sequence, and in the other group, succinylcholine 1.5 mg . kg(-1) was administered after the induction sequence. Laryngoscopy was attempted 90 s after rocuronium administration and 60 s after succinylcholine administration. Intubating conditions were assessed as excellent, good, or poor on the basis of ease of laryngoscopy, position of the vocal cords, and reaction to insertion of the tracheal tube and cuff inflation. RESULTS: There were 92 patients per group. In the rocuronium group, intubating conditions were excellent in 83 patients (90%), good in 8 (9%), and poor in 1 (1%), not significantly different from the intubating conditions in the succinylcholine group, which were excellent in 88 patients (96%), good in 3 (3%), and poor in 1 (1%) (P = 0.3). CONCLUSION: During a lidocaine-remifentanil-propofol induction of anesthesia, rocuronium 0.3 mg . kg(-1) administered before the induction sequence provides intubating conditions comparable to those achieved with succinylcholine 1.5 mg . kg(-1) administered after the induction sequence.

Preoxygenation by 8 deep breaths in 60 seconds using the Mapleson A (Magill), the circle system, or the Mapleson D system.

STUDY OBJECTIVE: To investigate the efficacy of preoxygenation by eight deep breaths in 60 seconds with the Mapleson A (Magill) system, the circle anesthesia system, or the Mapleson D system at an oxygen flow of 5 L/min or 10 L/min. DESIGN: Randomized, clinical study. SETTING: Operating room of a university hospital. SUBJECTS: 10 healthy volunteers. INTERVENTIONS: Volunteers underwent 6 preoxygenation trials consisting of 8 deep breaths in 60 seconds using the Mapleson A, Mapleson D, and the circle anesthesia systems at an oxygen flow of 5 L/min and 10 L/min. MEASUREMENTS: Fractional end-tidal oxygen concentration (F(ET)O(2)) was measured at 15-second intervals during preoxygenation. RESULTS: At an oxygen flow of 10 L/min, mean F(ET)O(2) values at 60 seconds of preoxygenation were comparable among the Mapleson A, Mapleson D, and the circle anesthesia systems (87 +/- 2.1%, 87 +/- 1.6%, 87 +/- 1.6%, respectively). Using an oxygen flow of 5 L/min, mean F(ET)O(2) values at 60 seconds were similar among the Mapleson A, Mapleson D, and circle anesthesia systems (74 +/- 4.1%, 75 +/- 2.6%, 74 +/- 4.4%, respectively); however, they were significantly lower than the corresponding values achieved at an oxygen flow of 10 L/min. CONCLUSIONS: The 8-deep-breaths in 60 seconds technique at an oxygen flow of 10 L/min can achieve adequate preoxygenation with the Mapleson A (Magill), Mapleson D, and circle anesthesia systems. Suboptimal preoxygenation is obtained with the three systems when the oxygen flow used is 5 L/min.

Does ondansetron or granisetron prevent subarachnoid morphine-induced pruritus after cesarean delivery?

BACKGROUND: We compared the efficacy of granisetron and ondansetron for the prevention of subarachnoid morphine-induced pruritus after cesarean delivery. METHODS: The incidence of pruritus was assessed in parturients who were randomly allocated into Group G (granisetron 3 mg IV, n = 45), Group O (ondansetron 8 mg IV, n = 42), and Group S (saline IV, n = 42). RESULTS: The incidence of pruritus was not significantly different among the 3 groups (86.6% in Group S, 83.3% in Group O, and 88% in the Group G). CONCLUSION: Neither prophylactic ondansetron nor granisetron reduced the incidence of subarachnoid morphine-induced pruritus when compared with the saline group.

The effect of injection of two vs 10 mL saline on the subsequent spread and quality of epidural analgesia in parturients.

OBJECTIVE: To determine whether two vs 10 mL of saline injected into the epidural space affects the subsequent spread and quality of epidural analgesia in parturients. DESIGN: Randomized, double-blinded, placebo-controlled study. SETTING: Delivery room. PATIENTS: 105 ASA physical status I and II parturients requesting epidural analgesia. INTERVENTIONS: After identification of the epidural space by the loss-of-resistance technique using normal saline, two mL of saline was then injected into the epidural space in the 2-mL group (n = 53) and 10 mL in the 10-mL group (n = 52). Five minutes after the test dose, patients received 10 mL of bupivacaine (0.1%) with fentanyl two microg mL(-1). MEASUREMENTS: 25 minutes after the initial bolus of bupivacaine and fentanyl, spread of block, subsequent pain relief, and influence of the volume of the injected saline on the ease of epidural catheter insertion and on the incidence of blood vessel trauma and paresthesia were evaluated. RESULTS: The total number of dermatomes blocked for cold and pinprick sensation in the 10-mL group was significantly more than in the 2-mL group (19 [6-29] vs 15 [4-27] for cold sensation, P = 0.000; and 15 [3-29] vs 11.5 [3-26] for pinprick sensation, P = 0.001). However, the visual analog pain scale and need for supplemental analgesia were similar between the two groups. The epidural catheter was easily inserted in 94.2% of the 2-mL group and 100% of the 10-mL group. The incidence of blood vessel trauma was low and the incidence of paresthesia was high without any significant difference between the two groups. CONCLUSIONS: 10 mL saline was associated with a higher total number of dermatomes blocked for both cold and pinprick sensation than the two mL saline. However, the pain relief was adequate in both groups, and two mL saline was as effective as the 10 mL in the ease of catheter insertion and prevention of intravascular cannulation.

A comparison of sevoflurane-propofol versus sevoflurane or propofol for laryngeal mask airway insertion in adults.

In a prospective, randomized study, we investigated the incidence of successful insertion of laryngeal mask airway (LMA) at the first attempt and the incidence of side effects after LMA insertion using the combination of sevoflurane and propofol as compared with either sevoflurane or propofol alone for induction of anesthesia. Eighty-three unpremedicated ASA physical status I-II patients were anesthetized with a single vital capacity breath (VCB) of sevoflurane 8% supplemented with IV propofol 1.5 mg/kg, a single VCB of sevoflurane 8%, or IV propofol 3 mg/kg. The coinduction technique was associated with the most frequent incidence of successful LMA insertion at the first attempt (93.5%) than either sevoflurane alone (46%) or propofol alone (61.5%) (P < 0.001). Propofol-induced induction of anesthesia allowed the fastest insertion of LMA and was associated with the least frequent incidence of postoperative nausea and vomiting. However, this advantage of propofol was offset by a frequent incidence of pain on injection (69%) and the occurrence of movements during insertion of the LMA (50% in the propofol group versus 19% and 26% in the sevoflurane and sevoflurane-propofol groups, respectively; P < 0.05), as well as a more frequent incidence of apnea (84% in the propofol group versus 7% and 16% in the sevoflurane and sevoflurane-propofol groups, respectively; P < 0.001). The report shows that induction of anesthesia with sevoflurane-propofol combined provides a frequent incidence of successful LMA insertion at the first attempt that is associated with an infrequent incidence of apnea.

Oxygenation using tidal volume breathing after maximal exhalation.

UNLABELLED: We compared, in volunteers, the oxygenation achieved by tidal volume breathing (TVB) over a 3-min period after maximal exhalation with that achieved by TVB alone. Twenty-three healthy volunteers underwent the two breathing techniques in a randomized order. A circle absorber system with an oxygen flow of 10 L/min was used. The end-expiratory oxygen concentration (EEO(2)) was monitored at 15-s intervals up to 3 min. TVB after maximal exhalation produced EEO(2) values of 68% +/- 5%, 75% +/- 5%, and 79% +/- 4% at 30, 45, and 60 s, respectively, which were significantly larger (P < 0.05) than the corresponding values obtained with TVB alone (58% +/- 5%, 66% +/- 6%, and 71% +/- 5%, respectively). In both techniques, the EEO(2) increased exponentially, with time constants of 35 s during TVB after maximal exhalation versus 58 s during TVB without prior maximal exhalation. In conclusion, maximal exhalation before TVB can hasten preoxygenation by decreasing the nitrogen content of the functional residual capacity, with a consequent increase of EEO(2) to approximately 70% in 30 s and 80% in 60 s. IMPLICATIONS: Oxygenation by using maximal exhalation before tidal volume breathing produced a significantly faster increase in end-expiratory oxygen concentration than oxygenation with tidal volume breathing alone.

Alarming hypoxemia during one-lung ventilation in a patient with respiratory bronchiolitis-associated interstitial lung disease.

PURPOSE: To report a patient with respiratory bronchiolitis-associated interstitial lung disease (RB-ILD) who developed severe hypoxemia during one-lung ventilation (OLV). CLINICAL FEATURES: A 27-yr-old female, ex-smoker presented with productive cough and dyspnea of 18-month duration. The chest x-ray revealed diffuse abnormalities involving both lungs consisting of interstitial emphysema with irregular shadowing. Preoperative PaO(2) was 88 mmHg and pulmonary function tests showed moderate obstructive disease. The patient underwent right open lung biopsy. After induction of anesthesia, a left double lumen tube was inserted and its position verified with auscultation and fibreoptic bronchoscopy. Upon initiation of OLV, the patient developed severe hypoxemia and the PaO(2) dropped from 500 mmHg during two-lung ventilation (TLV) to 50 mmHg. Hypoxemia was readily corrected by resuming TLV. CONCLUSION: The severe hypoxemia during OLV in this patient with RB-ILD may be attributed to impaired hypoxic pulmonary vasoconstriction. Other causes were not excluded. Caution is warranted when initiating OLV in these patients.