The effects of epidural anesthesia on uterine vascular resistance, plasma arginine vasopressin concentrations, and plasma renin activity during hemorrhage in gravid ewes

[Assessment of anesthesia methods in ophthalmologic surgery by patients, surgeons, and anesthesiologists]

BACKGROUND

The purpose of this study was to evaluate anesthesia methods in ophthalmic surgery in elderly people assessed by patients, surgeon, and anesthesiologist using subjective rating scales.

PATIENTS AND METHODS

In a prospective, randomized study we compared in 52 (26 vs 26) elderly patients (ASA II and III, mean age 78.7+/-8.6 years) undergoing a cataract operation the satisfaction perceived by patients, surgeons, and anesthesiologists in relation to anesthesia methods [intravenous anesthesia (TIVA) vs balanced anesthesia (BA)] based on a score from 1=best to 6=worse.

RESULTS

Patient satisfaction was better in the TIVA group (1.65) than in the patients treated with BA (2.57), p<0.001. Surgeons perceived no difference (BA 1.15/TIVA 1.07). Anesthesiologists preferred TIVA (TIVA 1.5/BA 3.23), p<0.001.

CONCLUSION

In this study patients and anesthesiologists preferred TIVA. There was no difference between TIVA and BA as seen by the surgeon.

Comparison of general and epidural anesthesia in elective cesarean section for placenta previa totalis: maternal hemodynamics, blood loss and neonatal outcome

There are few consistent guidelines in choosing anesthesia for cesarean section for a parturient with placenta previa. This prospective randomized trial was organized to compare the maternal hemodynamics, blood loss and neonatal outcome of general versus epidural anesthesia for cesarean section with the diagnosis of grade 4 placenta previa. After giving informed consent, 12 patients received general anesthesia and 13 received epidural. Intraoperative blood pressures demonstrated a more stable course in the epidural group than in the general group. Blood loss did not differ significantly between the groups (1622 +/- 775 mL vs. 1418 +/- 996 mL). General anesthesia resulted in lower immediate postoperative hematocrit level (28.1 +/- 3.5% vs. 32.5 +/- 5.0%, P < 0.05). The patients in the general group received a significantly larger transfusion than the epidural group (1.08 +/- 1.6 vs. 0.38 +/- 0.9 units, P < 0.05). The Apgar scores at 1 and 5 min were similar in the two groups (8 [4-9] vs. 8 [7-9] and 10 [6-10] vs. 9 [9-10], respectively). We concluded that epidural anesthesia is superior to general anesthesia in elective cesarean section for grade 4 placenta previa with regard to maternal hemodynamics and blood loss. There was no difference in neonatal outcome.

Endogenous endothelin and vasopressin support blood pressure during epidural anesthesia in conscious dogs

We studied whether endogenous endothelin, like endogenous vasopressin, helps to maintain blood pressure during high epidural anesthesia when efferent sympathetic drive is diminished. On different days, six awake dogs underwent each of the following five interventions: blockade of vasopressin V(1a) receptors using [d(CH(2))(5)Tyr(Me(2))]AVP, (40 microg/kg) or endothelin receptors using tezosentan (3 mg/kg followed by 3 mg. kg(-1). h(-1)) with or without epidural anesthesia (1% lidocaine, intraindividual dose did not differ between experiments), and epidural saline (n = 5). The effects of endothelin- or vasopressin-receptor blockade were analyzed (means +/- SEM) and compared by an analysis of variance for repeated measures (paired Student's t-test, alpha-adjusted, P < 0.05). Vasopressin-receptor blockade decreased blood pressure (10 +/- 2 mm Hg) only in the presence of epidural anesthesia, whereas endothelin-receptor blockade reduced blood pressure both in the presence and absence of epidural anesthesia (12 +/- 3 versus 10 +/- 1 mm Hg). During baseline and each intervention, plasma concentrations of vasopressin and big-endothelin were measured and compared by a Wilcoxon's rank sum test; P < 0.05. Vasopressin concentrations increased during epidural anesthesia and after additional endothelin receptor blockade, but big-endothelin concentrations remained unchanged during each intervention. We conclude that vasopressin acts as a reserve system, as it stabilizes blood pressure specifically during epidural anesthesia, whereas the unchanged concentrations of big-endothelin indicate that the endothelin system is not specifically activated to support blood pressure during epidural anesthesia.

IMPLICATIONS

We studied in awake dogs whether endogenous endothelin, like endogenous vasopressin, helps to maintain blood pressure during resting conditions and epidural anesthesia. Only vasopressin was specifically activated to support blood pressure during epidural anesthesia, whereas endothelin supported blood pressure to the same extent during epidural anesthesia and during resting conditions.

A randomized, blind comparison of remifentanil and alfentanil during anesthesia for outpatient surgery

We compared remifentanil, an esterase-metabolized opioid, with alfentanil as part of balanced anesthesia with at least 0.8% isoflurane during outpatient surgery in a randomized, double-blind trial. One hundred two patients received remifentanil, and 99 patients received alfentanil. Patients who received remifentanil experienced significantly fewer stress responses to surgical stimuli (52.9% and 65.7%, P < 0.05); significantly fewer remifentanil patients responded to skin closure (11% and 22%, P < 0.05) than patients who received alfentanil. Significantly more patients in the alfentanil group required extra analgesia compared with the remifentanil group (P < 0.05). Time to respond to verbal command was shorter for alfentanil than remifentanil (median 7 min vs 9 min), and times to spontaneous respiration (median 5 min vs 8 min), adequate respiratory rate (median 6 min vs 9 min), and tracheal extubation (median 6 min vs 9 min) were significantly shorter for alfentanil in comparison with remifentanil (P < 0.05). Remifentanil patients, however, showed significantly better recovery of psychomotor and psychometric function between 30 and 90 min after surgery (P < 0.05). The incidences of hypotension intraoperatively and shivering postoperatively were significantly higher with remifentanil. No unexpected or serious adverse events were recorded with remifentanil; however, one patient who received alfentanil experienced severe recurrent respiratory depression after surgery. The metabolic profile of remifentanil allowed better intraoperative analgesia without compromising recovery.

IMPLICATIONS

The pharmacological profile of remifentanil, a new opioid for use in anesthesia, suggests that rapid recovery will occur after its use. This study of 200 outpatients shows that the differences suggested from kinetic studies are not always borne out in clinical practice, although later recovery variables did, in fact, favor remifentanil.

A multicenter evaluation of total intravenous anesthesia with remifentanil and propofol for elective inpatient surgery

Remifentanil is a mu-opioid receptor agonist with a context sensitive half-time of 3 min and an elimination half-life < or = 10 min. This study sought to evaluate the efficacy of remifentanil and propofol total intravenous anesthesia (TIVA) in 161 patients undergoing inpatient surgery. Remifentanil 1 microgram/kg was given intravenously (i.v.) followed by one of two randomized infusion rates: small dose (0.5 micrograms.kg-1.min-1) or large dose (1 microgram.kg-1.min-1). Propofol (0.5-1.0 mg/kg i.v. bolus and 75 micrograms.kg-1.min-1 infusion) and vecuronium were also given. Remifentanil infusions were decreased by 50% after tracheal intubation. End points included responses (hypertension, tachycardia, and somatic responses) to tracheal intubation and surgery. More patients in the small-dose than in the large-dose group responded to tracheal intubation with hypertension and/or tachycardia (25% vs 6%; P = 0.003) but there were no other differences between groups in intraoperative responses. Recovery from anesthesia was within 3-7 min in both groups. The most frequent adverse events were hypotension (systolic blood pressure [BP] < 80 mm Hg or mean BP < 60 mm Hg) during anesthesia induction (10% small-dose versus 15% large-dose group; P = not significant [NS]) and hypotension (27% small-dose versus 30% large-dose group; P = NS), and bradycardia (7% small-dose versus 19% large-dose group; P = NS) during maintenance. In conclusion, when combined with propofol 75 micrograms.kg-1.min-1, remifentanil 1 microgram/kg i.v. as a bolus followed by an infusion of 1.0 microgram.kg-1.min-1 effectively controls responses to tracheal intubation. After tracheal intubation, remifentanil 0.25-4.0 micrograms.kg-1.min-1 effectively controlled intraoperative responses while allowing for rapid emergence from anesthesia.

Systemic vascular resistance index determined by thoracic electrical bioimpedance predicts the risk for maternal hypotension during regional anesthesia for cesarean delivery

OBJECTIVE

Our purpose was to evaluate the predictive value of the baseline systemic vascular resistance index for the development of maternal hypotension during regional anesthesia for cesarean delivery.

STUDY DESIGN

Patients receiving a standardized spinal or epidural anesthetic for nonemergency cesarean delivery were studied prospectively. Hemodynamic data were obtained noninvasively with an NCCOM-3 cardiac output monitor (Bomed Medical Manufacturing, Irvine, Calif.), which uses thoracic electrical bioimpedance to estimate stroke volume and cardiac output. Measurements obtained were indexed to body surface area. The systemic vascular resistance index was calculated from mean arterial pressure and thoracic electrical bioimpedance-derived cardiac index. Hemodynamic data obtained were analyzed to identify statistically significant predictors of maternal hypotension.

RESULTS

Maternal hypotension occurred in 24 of 42 (57%) patients studied. The incidence of hypotension did not differ between the types of anesthesia: spinal 17 of 274 (62%) versus epidural 7 of 15 (47%, p=0.48). The mean interval to the onset of hypotension was 12.2 minutes (SD 2.2 minutes, range 2 to 24 minutes). Mean (SD) baseline maternal systolic blood pressure was higher in patients who had hypotension (145 torr [4]) than those who did not (129 torr [4], p=0.01). The mean (SD) baseline systemic vascular resistance index was higher in patients who had hypotension (633 [SD 36] dyne . cm . sec-5/m2) than those who did not (454 [SD 29] dyne . cm . sec-5/m2; p =0.001). With receiver-operator characteristic curves, a baseline systemic vascular resistance index of 500 had a sensitivity of 83%, a specificity of 78%, a positive predictive value of 83%, and a negative predictive value of 78% for maternal hypotension (odds ratio 17.5, 95% confidence interval 3.1 to 109.4). A baseline systolic blood pressure of 140 torr had a sensitivity and specificity of 42% and 72%, respectively (odds ratio 1.9, 95% confidence interval 0.4 to 8.8).

CONCLUSIONS

Baseline systemic vascular resistance index obtained by noninvasive cardiac output monitoring with thoracic electrical bioimpedance and systolic blood pressure are useful to predict the risk for maternal hypotension with regional anesthesia. Patients with increased baseline systemic vascular resistance index or systolic blood pressure are at increased risk for hypotension.