Controversies in anaesthesia for noncardiac surgery in older adults.

As the population of the world is rapidly ageing, the amount of surgery being performed in older patients is also increasing. Special attention is required for the anaesthetic and perioperative management of these patients. The clinical and non-clinical issues specific to older surgical patients are reviewed, with a special emphasis on areas of debate related to anaesthesia care in this group. These issues include the role of frailty and disability in preoperative assessment, choice of anaesthesia technique for hip fracture, postoperative delirium, and approaches to shared decision-making before surgical procedures.

Intrathecal low-dose bupivacaine versus lidocaine for in vitro fertilization procedures.

BACKGROUND AND OBJECTIVES: Recent controversy with the use of intrathecal lidocaine has prompted the search for suitable ambulatory surgery alternatives. The purpose of our study was to evaluate the clinical utility of intrathecal low-dose bupivacaine for outpatient transvaginal oocyte retrieval. METHODS: Forty women enrolled and completed our prospective, randomized, double-blinded study of intrathecal hyperbaric bupivacaine 3.75 mg (0.5 mL of 0.75%) with fentanyl 25 microg versus hyperbaric lidocaine 30 mg (2.0 mL of 1.5%) with fentanyl 25 microg. Onset and level of sensory and motor block; time to ambulation, urination, and discharge; and intra- and postoperative complications (hypotension, pruritus, nausea, emesis, postdural puncture headache, post spinal pain syndrome [PSPS]) were recorded. Data were evaluated using analysis of variance, chi-squared, and Mann-Whitney U tests, with P <.05 considered significant. RESULTS: In demographically similar groups, no differences were noted in times to onset and recovery of sensory and motor function, or complications; however, times to voiding and discharge were significantly longer in the bupivacaine group. Four and 2 patients in the bupivacaine and lidocaine groups, respectively, required intravenous analgesic supplementation. One patient in the lidocaine group experienced PSPS. CONCLUSIONS: Although prolongation to voiding and discharge was observed, intrathecal hyperbaric bupivacaine 3.75 mg with fentanyl 25 microg is a viable anesthetic for oocyte retrieval.

Transcutaneous electrical nerve stimulation does not augment epidural labor analgesia.

STUDY OBJECTIVE: To evaluate whether transcutaneous electrical nerve stimulation (TENS) can increase the quality and duration of an initiation dose of bupivacaine used for the establishment of epidural labor analgesia. DESIGN: Randomized, double-blind study. SETTING: Tertiary-care academic medical center. PATIENTS: 40 ASA physical status I and II parturients in early, active spontaneous labor with a singleton, vertex term fetus, and requesting analgesia. INTERVENTIONS: A standardized epidural technique with either an active or inactive TENS unit was performed. Before epidural placement, TENS intensity thresholds were determined with electrodes placed over the paraspinus muscles at T(10)-L(1), and S(2)-S(4); TENS settings for mode, cycle, and pulse width were standardized. MEASUREMENTS: Data were collected at timed intervals on pain as measured by visual analog scale (VAS), sensory level (pinprick), motor blockade (Bromage score), cervical dilation, and duration of analgesia. MAIN RESULTS: The duration of analgesia produced by the initial dose of epidural bupivacaine did not differ between groups (TENS turned off 82.3 +/- 26 [mean +/- SD] vs. TENS activated 80.7 +/- 40 min, p = 0.88). Kaplan-Meier survival analysis and Mantel-Cox log rank analysis showed no difference between the two treatments (p = 0.75). No difference in the quality of analgesia was observed between the two groups. CONCLUSIONS: In healthy laboring parturients, the application of a TENS unit did not alter the quality or duration of an initiation dose of bupivacaine utilized for the establishment of epidural labor analgesia.

Hemodynamic effects of simultaneous administration of intravenous ephedrine and spinal anesthesia for cesarean delivery.

STUDY OBJECTIVE: To evaluate the hemodynamic effects of an intravenous (IV) ephedrine bolus given simultaneously with spinal anesthesia for cesarean delivery. DESIGN: Randomized, prospective, double-blind study. SETTING: Tertiary-care academic medical center. PATIENTS: 40 ASA physical status I and II nonlaboring women undergoing elective cesarean delivery of term, uncomplicated, singleton pregnancies. INTERVENTIONS: After a 10 mL/kg IV lactated Ringers bolus given over 15 minutes, patients simultaneously received an IV dose of 2 mL (10 mg) ephedrine or 2 mL saline, and an intrathecal dose of 12 mg (1.6 mL 0.75%) bupivacaine with 10 microg of fentanyl. Hypotension, defined as a 20% decrease in mean arterial pressure (MAP), was treated with 10-mg IV doses of ephedrine. MEASUREMENTS: Hemodynamic (heart rate and MAP) and non-invasive thoracic impedance (cardiac index, stroke index, and systemic vascular resistance index) measurements at baseline and at 1-minute intervals until the time of delivery. Total fluid, supplemental ephedrine, and Apgar scores were recorded. Data were evaluated using analysis of variance (ANOVA), ANOVA for repeated measures, and Mann-Whitney U-tests where appropriate, with p < 0.05 considered significant. MAIN RESULTS: Significant changes from baseline in MAP, systemic vascular resistance index, heart rate, and cardiac index were observed in both groups after spinal anesthesia. However, there were no differences between the ephedrine and saline groups in the incidence and severity of change from the baseline. The overall incidence of hypotension was 70% in both groups. No difference in total fluid or supplemental ephedrine use was observed. CONCLUSIONS: 10 mg of IV ephedrine given at the time of spinal anesthesia, and after a 10 mL/kg lactated Ringers fluid bolus, does not diminish the incidence or severity of hypotension in parturients undergoing cesarean delivery.

Alternative medicine use in presurgical patients.

BACKGROUND: A dramatic increase in the use of complementary and alternative medicines has been observed. The use of such remedies in the presurgical population has implications for the anesthesiologist because of the potential for drug interactions, side effects, and medical liability. This study was undertaken to quantify the use of herbal remedies and vitamins in the presurgical population of a large tertiary care center. METHODS: A one-page questionnaire was distributed to all patients presenting for evaluation in the preoperative clinic over an 11-week period. Patients answered questions regarding use of prescription and nonprescription medications, herbal remedies, and vitamins. RESULTS: Twenty-two percent of presurgical patients reported the use of herbal remedies, and 51% used vitamins. Women and patients aged 40-60 yr were more likely to use herbal medicines. Over-the-counter medication use was strongly associated with herbal preparation use. The most commonly used compounds, from highest to lowest, included echinacea, gingko biloba, St. John's wort, garlic, and ginseng. CONCLUSIONS: Alternative medicine use is common in the preoperative period.

Transcutaneous electrical nerve stimulation does not augment combined spinal epidural labour analgesia.

PURPOSE: The spinal portion of the combined spinal epidural technique (CSE) provides dramatic but limited labour analgesia. Transcutaneous Electrical Nerve Stimulation (TENS) has been noted to modulate pain, in part by the frequency of stimulation chosen. Because nerve action potentials are blocked by local anesthetics in a frequency dependent manner, we speculated that a TENS unit could increase the quality and duration of the spinal portion of a CSE. METHODS: Forty parturients in active spontaneous labour, with a singleton, vertex, term fetus, requesting analgesia were enrolled in a randomized, double blind fashion to receive a standardized CSE with either an active or inactive TENS unit. Prior to CSE placement, TENS intensity thresholds were determined with electrodes placed on the paraspinus muscles at T10-L1, and S2-4; TENS settings for mode, cycle, and pulse width were standardized. Data were collected at timed intervals on pain (VAS), sensory level (pinprick), motor blockade (Bromage), cervical dilatation, and duration of analgesia, and at delivery on fetal and neonatal outcome. RESULTS: The duration of the spinal portion of the CSE did not differ between groups (TENS off 91.1+/-33 [mean +/- SD] vs. TENS on 83.1+/-28 min, P = .42). Kaplan-Meier survival analysis and Mantel-Cox log rank analysis showed no difference between the two treatments (P = .28). Analgesia was comparable throughout the first hour of spinal analgesia. CONCLUSION: In healthy labouring parturients, the application of a TENS unit did not alter the quality or duration of labour analgesia provided by the spinal portion of CSE analgesia.

Measurements of maternal protein binding of bupivacaine throughout pregnancy.

UNLABELLED: Pregnancy-related decreases in protein binding may contribute to altered effects of local anesthetics in the parturient. Previous studies have measured protein binding of bupivacaine in term parturients; the current study defines the ratio of bound-to-free bupivacaine throughout gestation at both therapeutic and toxic systemic concentrations of bupivacaine. Venous samples were obtained from 81 women, including 70 parturients, ranging from 7 to 42 wk of gestation and 11 nonpregnant controls. The percent bound bupivacaine at a fixed concentration was determined for each sample at both therapeutic (1 microg/mL) and toxic (5 microg/mL) concentrations using an ultrafiltration technique. Albumin and alpha-1-glycoprotein levels were also measured. Linear regression analysis showed a significant increase in concentration of free bupivacaine throughout gestation at the 5-microg/mL concentration, corresponding to a decrease demonstrated in both albumin and alpha-1-glycoprotein levels. A similar correlation was not found at the 1-microg/mL concentration. Although the relative magnitude of these changes is small, the relative change in free drug throughout gestation is large. Protein binding is only one of several mechanisms that may influence the susceptibility to local anesthetic toxicity in the parturient; however, its relative importance remains unclear. IMPLICATIONS: When venous samples taken from pregnant women were mixed with 5 microg/ml bupivacaine and analyzed, an increase in the free fraction of drug was seen with increasing gestational age, corresponding to decreases in alpha-1-glycoprotein and albumin.

Clinical effects and maternal and fetal plasma concentrations of 0.5% epidural levobupivacaine versus bupivacaine for cesarean delivery.

BACKGROUND: Bupivacaine exists as a mixture of two enantiomers, levobupivacaine and dexbupivacaine. Data suggest that levobupivacaine has equal local anesthetic potency, with reduced potential for central nervous system and cardiovascular toxicity. The present study compares the efficacy of 0.5% levobupivacaine with 0.5% bupivacaine for epidural anesthesia in parturients undergoing elective cesarean delivery. METHODS: Sixty healthy obstetric patients undergoing elective cesarean delivery with epidural anesthesia completed the study. Patients were randomized to receive 30 ml of either 0.5% levobupivacaine or 0.5% bupivacaine in a double-blind fashion. The efficacy endpoint measures included onset, offset, and quality of anesthesia. Neonatal blood gas analyses, Apgar score determinations, and neurobehavioral examinations were performed. Venous samples for pharmacokinetic studies and serial electrocardiograms were obtained in 10 patients in each group. RESULTS: Levels of sensory block, motor block, muscle relaxation, and overall quality of anesthesia did not differ between groups. The frequency of hypotension was 84.4% in the levobupivacaine group and 100% for the bupivacaine group (P < or = 0.053). No significant difference in observed maximum concentration of drug after dosing or area under the plasma drug concentration versus time curve were seen. The maximum concentrations were 1.017 and 1.053 microg/ml, and the areas were 4.082 and 3.765 h(microg/ml) for the levobupivacaine and bupivacaine groups, respectively. Umbilical vein-to-maternal vein ratios were 0.303 for the levobupivacaine group and 0.254 for the bupivacaine group. CONCLUSIONS: The use of epidural 0.5% levobupivacaine for cesarean delivery results in equally efficacious anesthesia compared with 0.5% bupivacaine. Pharmacokinetic parameters were similar in the two groups.

Etiology and prevention of pulmonary complications following beta-mimetic mediated tocolysis.

OBJECTIVES: This study documents biological (haematocrit variations) and therapeutic parameters (salbutamol doses, volumes perfused) in two groups tocolysed with salbutamol, one with and the other without APO in order to define the risk factors linked to APO and to establish a standard protocol of management. STUDY DESIGN: This retrospective study includes data from 68 intravenous salbutamol tocolysis with four resulting APOs, carried out between January 1st, 1993 and December 31st, 1995. RESULTS: There was an excessive level of salbutamol administered over 48 h in the complicated APO-group (122.5+/-52 mg) opposed to the non-APO group (44.9 21 mg) as well as an overload of perfused solute (3.1+/-1.11) versus (1.9+/-1.11). Blood hemodilution was demonstrated in the APO group with a decrease of haematocrit by over 10% between the admission and the control value. No other risk factor was found. CONCLUSION: Tocolysis should be administered at the lowest possible perfusion rate with incremental doses as long as the heart rate stays under 120 beats/min and stopped after 48 h. Administration of maximal 11 of solute perfused/day is recommended. For the patient's follow-up we estimate daily input and output fluid to avoid hydric overload, and a daily control of haematocrit whose variation must be less than 10%.

Plasma active renin, angiotensin I, and angiotensin II during pregnancy and in preeclampsia.

OBJECTIVE: To evaluate the activity of the renin-angiotensin-aldosterone system in the circulation during the three trimesters of normal pregnancy and in women with preeclampsia. METHODS: Normal pregnant volunteers (n = 7) were studied throughout pregnancy, and women with preeclampsia (n = 8) were studied in the third trimester. Plasma active renin and aldosterone were measured by radioimmunoassay. Angiotensin I and angiotensin II were determined by radioimmunoassay after separation of the peptides by high-performance liquid chromatography. RESULTS: Active renin concentration increased in the first trimester of normal pregnancy, whereas angiotensin I, angiotensin II, and aldosterone remained at a level comparable to the postpartum values. Highest activity of the renin-angiotensin-aldosterone system was observed during the third trimester with increased levels of angiotensin I, angiotensin II, and aldosterone. In contrast, in patients with preeclampsia, despite a slight increase of active renin levels, the other parameters of the renin-angiotensin-aldosterone system were low compared with the third trimester of normal pregnancy and were comparable to postpartum data. CONCLUSION: Our results suggest that during the first trimester of normal pregnancy, active renin concentration in the plasma is increased and that renin is not the factor that limits angiotensin II synthesis. These results also confirm decreased activity of the renin-angiotensin-aldosterone system in preeclampsia. This could contribute to the diminished hemodynamic control observed in pregnant women developing preeclampsia.

Estrogen-induced changes in protein binding of bupivacaine during in vitro fertilization.

BACKGROUND: Patients having in vitro fertilization (IVF) procedures that use gonadotropin-releasing hormone agonist down-regulation undergo hormonal manipulation of estrogen concentrations to induce oocyte maturation. After achieving minimal estrogen concentrations (baseline), stimulation increases estrogen concentrations to supraphysiologic levels, leading to egg retrieval. The isolated effect of estrogen on protein binding has not previously been reported. This study was conducted to measure the effect of estrogen concentrations on protein binding of two concentrations of bupivacaine, 1 microg/ml and 5 microg/ml, corresponding, respectively, to systemic concentrations expected after administration of epidural anesthesia and associated with bupivacaine toxicity. Serum proteins were measured to address the mechanism. METHODS: Twenty-nine healthy women undergoing IVF procedures were enrolled and venous samples were drawn at times of minimal and maximal estrogen concentrations. The percentage of free bupivacaine was determined at fixed concentrations of 1 and 5 microg/ml. Serum albumin and alpha1-acid glycoprotein concentrations were measured at baseline and at retrieval in a group of 24 women. RESULTS: The percentage of free bupivacaine increased between times of minimal and maximal serum estrogen concentrations, corresponding to decreased protein binding. Concentrations of serum albumin and alpha1-acid glycoprotein decreased between baseline and retrieval times. CONCLUSIONS: Patients undergoing IVF procedures demonstrate a decrease in protein binding of bupivacaine from baseline concentrations. These changes may be explained by a decrease in albumin and alpha1-acid glycoprotein. During anesthesia for egg retrieval, clinicians should consider the implications of increased free fraction of drug, especially for highly protein-bound agents.

Hemodynamic effects of intrathecal sufentanil compared with epidural bupivacaine in laboring parturients.

STUDY OBJECTIVES: To provide information on the central hemodynamic effects of intrathecal sufentanil after a standard intravenous preload using thoracic bioimpedance monitoring to obtain noninvasive measurements of cardiac index (CI), stroke index (SI), and systemic vascular resistance (SVR). To compare hemodynamic parameters after intrathecal sufentanil labor analgesia to those after a standard dose of epidural bupivacaine in laboring parturients. DESIGN: Randomized, double-blind study. SETTING: Labor and delivery unit in a university hospital. STUDY DESIGN: 40 ASA status I parturients were randomized into two groups receiving analgesia with combined spinal-epidural technique. Group SUF received 10 micrograms of intrathecal sufentanil followed by 12 ml of saline through an epidural catheter; Group BUP received 2 ml of intrathecal saline followed by 12 ml of 0.25% epidural bupivacaine. Heart rate (HR), blood pressure (BP), and thoracic bioimpedance monitoring were recorded. Pain scores, fetal HR, and side effects were noted. MEASUREMENTS AND MAIN RESULTS: No significant changes from baseline were seen in CI, SI, or SVR index. Mean arterial pressure was lower in Group BUP at 10 and 20 minutes after induction of analgesia. Mean HR was lower in Group SUF at 20 and 30 minutes after induction. Two patients in Group SUF and four patients in Group BUP experienced hypotension requiring ephedrine. Pain scores were lower in Group SUF at 10 minutes after induction of analgesia; subsequent pain scores and duration of analgesia were similar. Fourteen patients in Group SUF experienced itching. CONCLUSIONS: No significant differences in CI, SI, or SVR index were seen after either method of analgesia. A few patients in both groups experienced hypotension requiring treatment with ephedrine. Both techniques of labor analgesia appear to provide effective pain relief but care must be taken with either method to monitor maternal BP.

The effects of varying volumes of crystalloid administration before cesarean delivery on maternal hemodynamics and colloid osmotic pressure.

The value of intravenous crystalloid administration in preventing spinal-induced hypotension in the parturient has recently been questioned. Also, the association between increasing crystalloid volume and decreasing postpartum colloid osmotic pressure (COP) raises concern regarding the risk of maternal and fetal pulmonary edema. To study the dose-response effect of varying amounts of crystalloid volume prior to spinal anesthesia, we measured maternal hemodynamic variables and maternal and fetal COP in three groups of healthy parturients receiving spinal anesthesia for elective cesarean delivery. Fifty-five parturients were randomized in a double-blind fashion to receive one of 10, 20, or 30 mL/kg of crystalloid volumes prior to induction of spinal anesthesia. Measurements included mean arterial blood pressure (MAP), cardiac index (CI), and systemic vascular resistance index (SVRI) recorded using noninvasive thoracic impedance monitoring until delivery. Maternal and neonatal COP were measured. All groups showed declines in MAP and SVRI from baseline at 5 min after spinal anesthesia, but the amount of decline did not differ among groups. Total ephedrine and additional intravenous (i.v.) fluid administered did not differ among groups. The 20- and 30- mL/kg groups showed a larger decline in maternal COP than the 10-mL/kg group; no differences in neonatal COP were seen with varying preload. We conclude that increasing the amount of i.v. crystalloid administered to 30 mL/kg in the healthy parturient does not significantly alter maternal hemodynamics or ephedrine requirements after spinal anesthesia and has no apparent benefit.

Pulmonary function changes during epidural anesthesia for cesarean delivery.

Although changes in pulmonary function in parturients are documented, little is known about effects of regional anesthesia on these changes. This study was undertaken to determine if two local anesthetics, often used for epidural anesthesia for cesarean delivery, have different effects on pulmonary function testing. Nineteen ASA physical status I parturients undergoing elective cesarean delivery with epidural anesthesia were randomly assigned in double-blind fashion to receive either 0.5% bupivacaine or 2% lidocaine with epinephrine (1/200,000). Pulmonary function tests were measured using a calibrated spirometer with computer-recorded flow volume loops. Peak inspiratory pressure and peak inspiratory flow rate, peak expiratory pressure (PEP) and peak expiratory flow rate, forced vital capacity (FVC), and forced expiratory volume in 1 s (FEV1) were measured. Measurements were taken prior to epidural placement and at T-10 and T-4 levels. Peak inspiratory pressure, FEV1/FVC, FEV1, FVC, peak expiratory flow rate, and peak inspiratory flow rate did not differ from baseline in either group. Patients receiving lidocaine showed a significantly greater decrease in PEP at both T-10 and T-4 levels. Pep is largely dependent on abdominal musculature. If a denser motor block is provided by 2% lidocaine with epinephrine than by 0.5% bupivacaine, these muscles would be more affected, resulting in a greater decrease in PEP. These results may have implications regarding choice of local anesthetic for epidural anesthesia in parturients with some degree of respiratory compromise undergoing cesarean delivery.

Maternal and neonatal fentanyl and bupivacaine concentrations after epidural infusion during labor.

Labor analgesia using continuous epidural infusions of low-dose bupivacaine and fentanyl may be maintained for many hours. We examined the potential for drug accumulation in both mother and neonate after these long-term infusions. Pregnant women receiving a 10-mL/h continuous infusion of labor analgesia with 0.125% bupivacaine and 2 micrograms/mL of fentanyl were evaluated. Maternal venous and umbilical venous drug concentrations were measured at delivery. Umbilical artery blood gases were obtained. Scanlon neurobehavioral testing was performed on all infants. Length of infusion times varied from 1 to 15 h. Maternal and neonatal drug concentrations remained relatively constant throughout the infusion period. All umbilical blood gas values and neurobehavioral scores were within normal limits. In conclusion, even when maintained for many hours, continuous infusion labor analgesia does not appear to result in significant fetal drug accumulation. No adverse neonatal effects were seen.

Prospective study on fetal weight estimation using limb circumferences obtained by three-dimensional ultrasound.

The aim of this prospective study was to evaluate the usefulness of fetal weight estimation in a prospective study, based on formulae derived from a previous retrospective study, using forward stepwise multiple regression analysis. Three-dimensional ultrasound was used to make reproducible measurement of limb circumferences, which formed the basis of our models. A total of 213 women with singleton pregnancies were scanned in the week prior to delivery and the following variables were measured: biparietal diameter, head circumference, transverse abdominal diameter, abdominal circumference, femur length, thigh circumference and arm circumference. The whole population was divided into three subgroups according to the abdominal circumference (< 10th centile, 10-90th centile, and > 90th centile). We demonstrated the need for only two models for accurate fetal weight estimation, one for the small-for-dates fetuses and a second for the others. The most accurate results were obtained for the macrosomic fetuses with a standard deviation of 8.8%. Our data confirm the usefulness of measurement of fetal thigh circumference for the the small-for-dates-fetuses and arm circumference for the other groups. We concluded that the use of three-dimensional ultrasound could facilitate the accurate prediction of fetal weight.

Measurements of protein binding of lidocaine throughout pregnancy.

Pregnancy-related anatomic and physiologic changes result in altered pharmacologic and toxicologic responses to local anesthetics. Reductions in serum protein binding have been implicated in enhanced toxic effects. Previous studies have demonstrated these reductions in protein binding only in the term parturient. The present study defines the pattern of protein binding changes of lidocaine throughout gestation. Venous samples were obtained from pregnant patients of varying gestational age, as well as from nonpregnant control patients. The percent free drug at a fixed concentration (2 micrograms/mL) was determined for each sample using an ultrafiltration technique. The free concentration of lidocaine increased significantly throughout gestation, reflecting a corresponding decrease in protein binding. However, these changes were small compared to those in the nonparturient, which suggests that toxicity to lidocaine should not vary during pregnancy.