Anesthesia and analgesia
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Anesthesia and analgesia · Nov 1999
Randomized Controlled Trial Clinical TrialThe lateral approach to the sciatic nerve at the popliteal fossa: one or two injections?
It has not been proven whether one or multiple nerve stimulations and injections provide a higher rate of complete sensory block in both major sciatic nerve sensory distributions below the knee when a popliteal sciatic nerve block is performed using the lateral approach. This prospective, randomized, single-blinded study compared the success rate of the sciatic nerve block using this approach when one or both major components of this nerve (i.e., tibial nerve and common peroneal nerves) are stimulated in 50 patients undergoing foot or ankle surgery. In Group 1 STIM, 24 patients received a single injection of 20 mL of a mixture of 2% lidocaine and 0.5% bupivacaine with 1:200,000 epinephrine after foot inversion had been elicited. In Group 2 STIM (n = 26), 10 mL of the same solution was injected after stimulation of each sciatic nerve component. For patients with complete sensory motor block, there was no difference in onset between groups. However, Group 2 STIM showed a greater success rate compared with the Group 1 STIM (2 STIM: 88% vs 1 STIM :54%; P = 0.007). When two stimulations were used, the onset time of anesthesia in the cutaneous distribution of the common peroneal nerves was shorter than in the tibial nerve (17.5 vs 30 min; P < 0.0001). We conclude that a two-stimulation technique provides a better success rate than a single-injection technique when a popliteal sciatic nerve block is performed using the lateral approach with 20 mL of local anesthetic. ⋯ A better success rate is achieved with a double stimulation technique than with a single injection for the sciatic nerve block via the lateral approach at the popliteal fossa when 20 mL of local anesthetics is used.
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Anesthesia and analgesia · Nov 1999
Randomized Controlled Trial Clinical TrialTeaching the use of fiberoptic intubation in anesthetized, spontaneously breathing patients.
In patients with difficult airways, the standard of care involves fiberoptic intubation under spontaneous ventilation. However, the safety and feasibility of a fiberoptic intubation teaching program has only been documented in paralyzed and apneic patients, whereas data obtained in patients under spontaneous respiration are limited and conflicting. We evaluated 100 anesthetized patients undergoing orotracheal fiberoptic intubation. Five anesthesia residents with no prior experience in fiberoptic laryngoscopy participated in the study. In a randomized fashion, each participant tracheally intubated 10 spontaneously breathing patients (Group A: sevoflurane anesthesia via an airway endoscopy mask) and 10 paralyzed patients (Group B: total IV anesthesia with propofol, fentanyl, atracurium). Overall rate of success (96%), defined as successful intubation of the trachea within two attempts, was not different between groups. During fiberoptic intubation, Spo2 values remained >95% in Group A, whereas Spo2 decreased to <95% in two patients in Group B. Failure to pass the tube into the trachea over the bronchoscope was encountered in four patients in Group A and in no patient in Group B. Our data suggest that it is safe to teach the use of fiberoptic intubation in anesthetized, spontaneously breathing patients with normal airway anatomy. ⋯ Fiberoptic intubation under spontaneous respiration is a well established technique for management of difficult airways. Our study demonstrates the feasibility and safety of a novice training program for fiberoptic intubation under general anesthesia, not only in paralyzed patients but also in those breathing spontaneously.
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Anesthesia and analgesia · Nov 1999
Randomized Controlled Trial Clinical TrialDose response relationships for isobaric spinal mepivacaine using the combined spinal epidural technique.
Mepivacaine, a local anesthetic with similar physiochemical properties to those of lidocaine, is an adequate alternative for patients undergoing ambulatory procedures, and is associated with a lower incidence of transient neurologic symptoms (TNS) than lidocaine. We studied the dose-response characteristics of isobaric intrathecal mepivacaine using the combined spinal epidural technique for patients undergoing ambulatory arthroscopic surgery of the knee. Seventy-five patients were randomized prospectively to receive one of three doses of isobaric mepivacaine for spinal anesthesia: 30 mg (2 mL 1.5%), 45 mg (3 mL 1.5%), or 60 mg (4 mL 1.5%). An observer, blinded to the dose, recorded sensory level to pinprick and motor response until resolution of the block. In addition, the incidence of TNS was determined. An initial intrathecal dose of 30 mg of isobaric mepivacaine 1.5% produced satisfactory anesthesia in 72% of ambulatory surgical patients undergoing unilateral knee arthroscopy with a significantly shorter duration of sensory (158 +/- 32 min) and motor blockade (116 +/- 38 min) than doses of 45 and 60 mg. An intrathecal dose of 45 mg produced satisfactory anesthesia in all patients with a shorter duration of sensory (182 +/-38 min) and motor blockade (142 +/- 37 min) than 60 mg of mepivacaine 1.5% (203 +/- 36 min and 168 +/- 36 min, respectively). The incidence of TNS was 7.4% overall (1.2%-13.6% confidence intervals), less than the rates previously reported after spinal anesthesia with lidocaine in ambulatory surgical patients undergoing knee arthroscopy. We conclude that mepivacaine can be used as an adequate alternative to lidocaine for ambulatory procedures. ⋯ This study evaluated the postoperative duration of spinal anesthesia after varying doses of isobaric mepivacaine and the incidence of transient radiating back and leg pain. We found that 45 mg of mepivacaine provided adequate anesthesia, a timely discharge, and a lower incidence of back pain than that previously reported after lidocaine spinals.
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Anesthesia and analgesia · Nov 1999
Randomized Controlled Trial Clinical TrialThe influence of different intravascular volume replacement regimens on renal function in the elderly.
Elderly patients are at risk of developing renal dysfunction. Synthetic colloids are often used perioperatively, but they may have detrimental effects on renal function. In a prospective, randomized study, we assessed the influence of different intravascular volume replacement regimens on renal function in elderly (>65 yr) and younger (< 65 yr) patients without preoperative renal dysfunction who were undergoing major abdominal surgery. Either 6% low molecular weight hydroxyethyl starch (HES) solution (mean molecular weight 70,000 D, degree of substitution 0.5; HES 70/0.5) [each group n = 10]), 6% medium-molecular weight HES (molecular weight 200,000 D, degree of substitution 0.5 (HES 200/0.5) [each group n = 10]), or modified gelatin (molecular weight 35,000 D [each group n = 10]) was administered to maintain mean arterial blood pressure >65 mm Hg and central venous pressure between 10 and 14 mm Hg. After the induction of anesthesia (T0); at the end of surgery (T1); 4 h after surgery (T2); and on the first (T3), second (T4), and third postoperative days (T5), alpha1-microglobulin (alpha1-M), N-acetyl-beta-glucosaminidase, fractional sodium clearance, and creatinine clearance (CC) were measured. Colloids (1300-3000 mL) were infused until the first postoperative day. At T0, urine concentrations of alpha1-M were higher in the elderly than in the younger patients in all groups (P < 0.05). alpha1-M remained increased only in the gelatin group. N-acetyl-beta-glucosaminidase and fractional sodium clearance were not affected during the study period in any groups. At baseline, CC was significantly higher in the younger than in the elderly patients, but CC did not decrease in any of the intravascular volume replacement groups. We conclude that intravascular volume therapy with gelatin and two different HES preparations did not adversely affect renal function in elderly patients without preoperative renal malfunction. ⋯ We studied the influence of three different intravascular volume replacement regimens on renal function in elderly patients without renal dysfunction who were undergoing major abdominal surgery. Two hydroxyethyl starch and one gelatin preparation were administered perioperatively to maintain stable hemodynamics. As assessed by sensitive markers of renal function, all three regimens can be used safely for volume replacement without risking significant renal dysfunction.