Anesthesia and analgesia
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Anesthesia and analgesia · Jun 2000
Randomized Controlled Trial Clinical TrialThoracic paravertebral block for breast surgery.
Cosmetic and reconstructive breast augmentation is a frequently performed surgical procedure. Despite advances in medical treatment, surgical intervention is often associated with postoperative pain, nausea, and vomiting. Paravertebral nerve block (PVB) has the potential to offer long-lasting pain relief and fewer postoperative side effects when used for breast surgery. We compared thoracic PVB with general anesthesia for cosmetic breast surgery in a single-blinded, prospective, randomized study of 60 women scheduled for unilateral or bilateral breast augmentation or reconstruction. Patients were assigned (n = 30 per group) to receive a standardized general anesthetic (GA) or thoracic PVB (levels T1-7). Procedural data were collected, as well as verbal and visual analog pain and nausea scores. Verbal postoperative pain scores were significantly lower in the PVB group at 30 min (P = 0.0005), 1 h (P = 0.0001), and 24 h (P = 0.04) when compared with GA. Nausea was less severe in the PVB group at 24 h (P = 0.04), but not at 30 min or 1 h. We conclude that PVB is an alternative technique for cosmetic breast surgery that may offer superior pain relief and decreased nausea to GA alone. ⋯ Paravertebral nerve block has the potential to offer long-lasting pain relief and few postoperative side effects when used for breast surgery. We demonstrated that paravertebral nerve block, when compared with general anesthesia, is an alternative technique for breast surgery that may offer pain relief superior to general anesthesia alone.
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Anesthesia and analgesia · Jun 2000
Randomized Controlled Trial Clinical TrialThe assessment of dermatomal level of surgical anesthesia after spinal tetracaine.
Transcutaneous electrical stimulation (TES), a 60-mA, 50-Hz continuous square wave, has been considered equivalent to surgical incision. We examined whether TES at a smaller current (10 mA) can be used to predict surgical anesthesia and compare the results with sensory block to cold, pinprick, and touch after the administration of spinal tetracaine. Two groups of 40 consecutive patients, 17-69 yr old and 70 yr old or older received a subarachnoid injection of 0. 5% tetracaine in 10% glucose or saline according to the type of surgery. Patients undergoing abdominal surgery received glucose solution, and those scheduled for lower extremities surgery received saline solution, and thus, the resultant four groups of patients were studied. Neural block was assessed by the loss of sensation to cold, pinprick, touch, and TES at 10 mA (T10s), and tolerance (i.e., the loss of pain or discomfort) to TES at 10 (T10p) and 60 (T60) mA. Dermatomal levels of sensory block to cold, pinprick, and touch that were cephalad to T60 varied widely. In contrast, dermatomal levels of T10s and T10p cephalad to T60 were less variable, and the difference between T10s and T60 was the smallest among all the differences in any groups. Our results demonstrate that, regardless of patient age and baricity of a local anesthetic solution, T10s is a good predictor of T60 equivalent to the dermatomal level of surgical anesthesia. ⋯ Our results show that the loss of sensation to transcutaneous electrical stimulation at 10 mA, but not cold, pinprick, or touch, is a good predictor of the dermatomal level of block to transcutaneous electrical stimulation at 60 mA, which is considered equivalent to the dermatomal level of surgical anesthesia after the administration of spinal anesthesia.
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Anesthesia and analgesia · Jun 2000
Toast and tea before elective surgery? A national survey on current practice.
A more tolerant approach to preoperative fasting guidelines for healthy adults undergoing elective surgery was recently recommended by a task force appointed by the American Society of Anesthesiologists. This recommendation liberalizes the intake of clear liquids and specifically allows a light breakfast (e.g., toast and tea or coffee) up to 6 h before elective surgery. We conducted a national survey to determine whether anesthesiologists giving anesthesia in an outpatient setting in the United States were currently following these recommendations, and whether institutional policy reflects these new guidelines. The population consisted of the entire active membership of the Society for Ambulatory Anesthesia, providing an initial sample size of 623 subjects. Most conservatively calculated, we had a response rate of 59.6%. A total of 62% of the respondents said they have an institutional policy in place to allow clear liquids orally 2-3 h before the induction of anesthesia. However, only 35% of the respondents said their institutions had a policy in place allowing a light breakfast 6 h before elective surgery. Nevertheless, only 3% of the responders said they would cancel the operation if a patient actually arrived at the facility after consuming a light breakfast, such as toast and tea 6 h before elective surgery, 32% would delay surgery to later that day, and 65% would proceed without delay. We concluded that most anesthesiologists practicing outpatient anesthesia in the United States have already changed their practice pattern to conform to the recent recommendations of the American Society of Anesthesiologists task force on preoperative fasting time. ⋯ Findings of this national survey conducted among active members of the Society for Ambulatory Anesthesia may encourage anesthesiologists throughout the world to take a more liberal attitude toward allowing clear liquids 2-3 h and a light breakfast 6 h before an elective surgery in healthy patients.
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Anesthesia and analgesia · Jun 2000
Propofol inhibits Ca(2+) transients but not contraction in intact beating guinea pig hearts.
We investigated whether propofol inhibits Ca(2+) transients and left ventricular pressure (LVP) in intact beating guinea pig hearts at clinical concentrations and whether an inhibition of Ca(2+) transients by propofol results from an impairment of sarcolemmal or of sarcoplasmic reticulum (SR) function. By using a Langendorff's preparation, transmural left ventricular phasic intracellular Ca(2+) concentration ([Ca(2+)](i)) was measured by the fluorescence ratio of indo-1 emission at 385 nm and 456 nm and was calibrated to Ca(2+) transients (in nM). The Ca(2+) transients during each contraction were defined as available [Ca(2+)](i). Sixty hearts were perfused with modified Krebs-Ringer's solution containing lipid vehicle and propofol (1 and 10 microM) in the absence and presence of ryanodine, thapsigargin, and nifedipine, while developed LVP and available [Ca(2+)](i) were recorded. Propofol (10 microM) decreased available [Ca(2+)](i) by 11.0% +/- 1.3% without decreasing developed LVP (% of control, P < 0.05). Propofol (10 microM) caused a leftward shift in the curve of developed LVP as a function of available [Ca(2+)](i). Propofol (10 microM) with nifedipine (1 microM), but not with ryanodine (1 microM) or thapsigargin (1 microM), decreased available [Ca(2+)](i) by 15.5% +/- 1.7% (P < 0.05). Propofol decreases available [Ca(2+)](i) without decreasing cardiac contraction, and it enhances myofilament Ca(2+) sensitivity in intact beating hearts at clinical concentrations. The inhibition of available [Ca(2+)](i) by propofol may be mainly mediated by an impairment of sarcoplasmic reticulum Ca(2+) handling rather than the sarcolemmal L-type Ca(2+) current. ⋯ This is the first study of the effects of propofol on intracellular Ca(2+) concentration and myofilament Ca(2+) sensitivity under physiologic conditions in intact isolated beating guinea pig hearts.
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Anesthesia and analgesia · Jun 2000
Comparative StudyA comparison of the electrocardiographic cardiotoxic effects of racemic bupivacaine, levobupivacaine, and ropivacaine in anesthetized swine.
We sought, in this observer-blinded study, to determine the lethal dose for each of the local anesthetics levobupivacaine (L), racemic bupivacaine (B), and ropivacaine (R), and to compare their respective effects on the QRS interval of the precordial electrocardiograph after intracoronary injection. Anesthetized swine were instrumented with a left anterior descending artery coronary angiography catheter and injected with increasing doses of L, B, or R according to a randomized protocol. The doses administered were 0. 375, 0.75, 1.5, 3.0, and 4.0 mg, with further doses increasing in 1-mg increments until death occurred. Plotting the mean maximum QRS interval as a function of the log(10) mmol dose allowed the following cardiotoxicity potency ratios to be determined for a doubling of QRS duration-B:L:R = 2.1:1.4:1. The lethal doses in millimoles (median/range) for L and R were (0.028/0.024-0.031) and (0.032/0.013-0.032), respectively, and were significantly higher than for B (0.015/0.012-0.019) - (P < 0.05, n = 7 for all groups). The lethal dose did not differ between R and L. Thus, the cardiotoxicity potency ratios for the three anesthetics based on lethal dose were: 2.1:1.2:1. If the anesthetic potencies for B and L are similar, the latter should have less potential for cardiotoxicity in the clinical situation. ⋯ Animal experiments have shown levobupivacaine and ropivacaine to be less cardiotoxic than racemic bupivacaine. This in vivo study, using a validated swine model, compared the relative direct cardiotoxicities of these three local anesthetics. The lethal dose did not differ between levobupivacaine and ropivacaine, but was lowest for racemic bupivacaine.