Anesthesia and analgesia
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Anesthesia and analgesia · Jan 2001
Comparative Study Clinical TrialPeripheral venous pressure as a hemodynamic variable in neurosurgical patients.
Neurosurgical patients undergoing either craniotomy or complex spine surgery are subject to wide variations in blood volume and vascular tone. The ratio of these variables yields a pressure that is traditionally measured at the superior vena cava and referred to as "central venous pressure" (CVP). We have investigated an alternative to CVP by measuring peripheral venous pressure (PVP), which, in parallel animal studies, correlates highly with changes in absolute blood volume (r = 0.997). We tested the hypothesis that PVP trends parallel CVP trends and that their relationship is independent of patient position. We also tested and confirmed the hypothesis, during planned circulatory arrest, that PVP approximates mean systemic pressure (circulatory arrest pressure), which reflects volume status independent of cardiac function. PVP was compared with CVP across 1026 paired measurements in 15 patients undergoing either craniotomy (supine, n = 8) or complex spine surgery (prone, n = 7). Repeated-measures analysis of variance indicated a highly significant relationship between PVP and CVP (P < 0.001), with a Pearson correlation coefficient of 0.82. The correlation was best in cases with significant blood loss (estimated blood loss >1000 mL; r = 0.885) or hemodynamic instability (standard deviation of CVP > 2; r = 0.923). ⋯ In patients undergoing either elective craniotomy or complex spine surgery, peripheral venous pressure (PVP) trends correlated with central venous pressure (CVP) trends with a mean offset of 3 mm Hg (PVP > CVP). PVP trends provided equivalent physiological information to CVP trends in this subset of patients, especially during periods of hemodynamic instability. In addition, measurements made during a planned circulatory arrest support the hypothesis that PVP approximates mean systemic pressure (systemic arrest pressure), which is a direct index of patient volume status independent of cardiac or respiratory activity.
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Anesthesia and analgesia · Jan 2001
Randomized Controlled Trial Comparative Study Clinical TrialRemifentanil versus meperidine for monitored anesthesia care: a comparison study in older patients undergoing ambulatory colonoscopy.
Colonoscopy is one of the most frequently performed outpatient procedures in the United States. This study was designed to test the hypothesis that a remifentanil infusion would be superior to boluses of meperidine in older patients undergoing ambulatory colonoscopy. One hundred ASA physical status I-IV patients undergoing colonoscopy were randomized in this double-blinded study to receive either remifentanil infusions (n = 49) or titrated boluses of meperidine (n = 51). Patient tolerance was assessed using physiologic variables and side effects associated with opioid analgesia. Verbal pain/anxiety and patient/operator satisfaction were also assessed. As a group, the physiologic characteristics demonstrated no significant differences in the response to the colonoscopy procedure. Although the patient and operator satisfaction surveys were similar between groups, the incidences of tachycardia, hypotension, and nausea were less and the adjusted verbal pain and anxiety scores were more in the Remifentanil group compared with the Meperidine group. This study demonstrates that remifentanil and meperidine were equally well tolerated in older patients undergoing ambulatory colonoscopy when administered by an anesthesia provider. The differences in the pharmakinetics of remifentanil and meperidine most likely account for the differences noted between the two treatment groups. ⋯ Remifentanil infusions and meperidine boluses are equally well tolerated in older patients undergoing ambulatory colonoscopy when administered by an anesthesia provider.
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Anesthesia and analgesia · Jan 2001
Randomized Controlled Trial Comparative Study Clinical TrialDexamethasone facilitates discharge after outpatient anorectal surgery.
Corticosteroids can decrease pain and postoperative nausea and vomiting after ambulatory surgery. Therefore, we designed a study to evaluate if the routine use of dexamethasone would facilitate the early recovery process after anorectal surgery. A secondary aim of the study was to determine if dexamethasone would increase the incidence of postoperative wound complications. Eighty adult outpatients undergoing anorectal surgery with a standardized monitored anesthesia care technique were randomly assigned to receive either dexamethasone 4 mg IV or an equal volume of saline before the start of surgery. All patients were premedicated with midazolam 2 mg IV and received ketorolac 30 mg IV as a preemptive analgesic. A propofol infusion, 50 microg. kg(-1). min(-1) IV, was initiated and subsequently titrated to maintain an observer's assessment of alertness/sedation score of 2 or 3 (with 5 = awake/alert to 1 = asleep). Fentanyl 25 microg IV was administered 3-5 min before infiltrating the surgical field with a 30-mL local anesthetic mixture containing 15 mL of lidocaine 1% and 15 mL of bupivacaine 0.25% (with epinephrine 1:200,000 and sodium bicarbonate 3 mL). All patients were fast-tracked directly from the operating room to the step-down recovery area. Even though the incidences of postoperative pain and postoperative nausea and vomiting were small in both treatment groups, the time to "home readiness" was significantly shorter in the dexamethasone group. Importantly, there was no increase in the incidence of wound infections (8% vs 12%) or hematoma formation (3% vs 5%) in the dexamethasone (versus saline) group. We conclude that the administration of dexamethasone, 4 mg IV, shortened the time to home readiness without increasing the incidence of postoperative wound infections in a high-risk outpatient population undergoing anorectal surgery. ⋯ A single dose of dexamethasone (4 mg IV) decreased the time to "home readiness" without increasing the incidence of postoperative wound complications in an outpatient population undergoing anorectal surgery.
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Anesthesia and analgesia · Jan 2001
Randomized Controlled Trial Comparative Study Clinical TrialThe analgesic effect of sufentanil combined with ropivacaine 0.2% for labor analgesia: a comparison of three sufentanil doses.
The combination of opioids with local anesthetics is commonly used for epidural labor analgesia. We examined whether increasing sufentanil in doses of 5, 10, and 15 microg prolonged the duration of labor analgesia produced by ropivacaine. One hundred healthy parturients in the first stage of labor who requested epidural analgesia were enrolled. Parturients were randomized to receive 12 mL ropivacaine 0.2% alone or with sufentanil 5 microg, sufentanil 10 microg, or sufentanil 15 microg. The duration of analgesia, pain score, degree of motor blockade (using a four-point Bromage scale), heart rate, blood pressure, respiratory rate, oxygen saturation, and incidence of nausea and pruritus were recorded. The mean duration of epidural analgesia was 96 +/- 32 min for patients without sufentanil, 134 +/- 27 min for Group 5 (p < 0.01 versus control), 135 +/- 33 min for Group 10 (p < 0.01 versus control), 130 +/- 33 min for Group 15 (p < 0.01 versus control) without differences among sufentanil groups. Between 30 and 90 min, the sufentanil groups (5 microg, 10 microg, and 15 microg) had lower pain scores than the control group (p < 0.01 versus control) but there were no differences among the sufentanil groups. No patient in any group had a Bromage score more than 1. No significant difference was found for opioid-related side effects. We conclude that 5-10 or 15 microg sufentanil induced a similar prolongation of analgesia when combined with ropivacaine 0.2% for initiation of labor analgesia. ⋯ We studied the effect of adding one of three possible sufentanil doses to epidural ropivacaine 0.2% for labor analgesia. Adding sufentanil increased the duration of analgesia but there was no advantage in adding more than 5 microg of sufentanil.
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Anesthesia and analgesia · Jan 2001
Randomized Controlled Trial Comparative Study Clinical TrialMinimum local anesthetic volume blocking the femoral nerve in 50% of cases: a double-blinded comparison between 0.5% ropivacaine and 0.5% bupivacaine.
Recent studies demonstrated that ropivacaine was nearly 40% less potent than bupivacaine in the first stage of labor, but contrasting results have been reported. We, therefore, conducted a prospective, randomized, double-blinded study to determine the effects of the ropivacaine/bupivacaine potency ratio on the minimum volume of local anesthetic required to produce effective block of the femoral nerve in 50% of patients. Fifty adults premedicated with IV midazolam, 0.05 mg/kg, undergoing elective knee arthroscopy received femoral nerve blocks with a multiple-injection technique with a nerve stimulator (contractions of vastus medialis, vastus intermedius, and vastus lateralis were elicited with a 0.5-mA stimulating current). Patients randomly received either 0.5% ropivacaine (n = 25) or 0.5% bupivacaine (n = 25). The anesthetic volume was decided according to Dixon's up-and-down method, starting from 12 mL and being equally divided among the three elicited twitches. Successful nerve block was loss of pinprick sensation in the femoral nerve distribution with concomitant block of the quadriceps muscle within 20 min after injection, as assessed by a blinded observer. Positive or negative responses determined a 3-mL decrease or increase for the next patient, respectively. According to the up-and-down sequences, the minimum local anesthetic volume providing successful nerve block in 50% of cases was 14 +/- 2 mL in the ropivacaine group (95% CI: 12-16 mL) and 15 +/- 2 mL (95% CI: 13-17 mL) in the bupivacaine group (P: = 0.155). We conclude that the volume of 0.5% ropivacaine required to produce effective block of the femoral nerve in 50% of patients is similar to that required when using 0.5% bupivacaine. ⋯ Considering the risk for drug-related systemic toxicity, the equipotency ratio between ropivacaine and bupivacaine is crucial for daily practice. Despite the 40% reduction in the analgesic potency of ropivacaine reported during epidural analgesia for labor pain, results of this prospective, randomized, double-blinded study demonstrated that the same volume of 0.5% ropivacaine or 0.5% bupivacaine is required to produce an effective block of the femoral nerve in 50% of cases.