Anesthesia and analgesia
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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 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 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.
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Anesthesia and analgesia · Nov 1999
Randomized Controlled Trial Clinical TrialModified continuous femoral three-in-one block for postoperative pain after total knee arthroplasty.
We prospectively studied the continuous "modified" femoral three-in-one block for postoperative pain after total knee arthroplasty. Sixty-two patients undergoing elective knee arthroplasty under spinal anesthesia with bupivacaine (B) and fentanyl were randomized to receive 0.2% B, 0.1% B, or placebo at 10 mL/h for 48 h after an initial bolus of 30 mL of the same solution via the femoral block catheter. The catheters were inserted under the fascia iliaca using a "double pop" technique and a peripheral nerve stimulator and were advanced 15-20 cm cranially. Venous plasma levels of B, desbutylbupivacaine, and 4-hydroxy B were measured daily for 3 days. All patients received patient-controlled analgesia with morphine and indomethacin suppositories for 48 h. Using computed tomography, we evaluated the catheter location for 20 patients. The catheter tips, located superior to the upper third of the sacroiliac joint in the psoas sheath, were labeled as ideally located. The group receiving 0.2% B had a larger block success rate, smaller morphine consumption in the immediate postoperative period (15 vs 22 mg) and during the first postoperative day (9 vs 18 mg), and achieved a greater range of motion in the immediate postoperative period (91 degrees +/- 10 degrees vs 80 degrees + 13 degrees ). Visual analog scores for pain during both rest and activity were low but similar between the groups. Forty percent of the catheters evaluated were ideally located. Ideal location and use of 0.2% B resulted in 100% success of blockade of all three nerves. The S1 root was blocked in up to 76% of patients. The plasma levels of B, 4-hydroxy B, and desbutylbupivacaine were below the toxic range during the infusion. We conclude that continuous fascia iliaca block with 0.2% B results in opioid-sparing and improved range of motion during the immediate postoperative period. Larger doses of bupivacaine may safely be used in the immediate postoperative period if needed. ⋯ Continuous fascia iliaca block with 0.2% bupivacaine reduces opioid requirements and improves range of motion in the immediate postoperative period compared with a placebo and 0.1% bupivacaine. Plasma levels are below the toxic range with this dose. Only 40% of the catheters are positioned in the ideal location. With the smaller dose of bupivacaine, the success rate with this block is small.