Biomedical subjects
D Benhamou
Publications and source records attributed to D Benhamou.
Axillary plexus block using multiple nerve stimulation: a European view.
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Hemodynamic effects of continuous spinal anesthesia: a comparative study between low and high doses of bupivacaine.
BACKGROUND AND OBJECTIVE: Arterial hypotension is a major side effect of spinal anesthesia. Continuous spinal anesthesia may allow titration of the amount of local anesthetic to obtain a level that is appropriate for the surgical procedure. METHODS: This study compared the hemodynamic effects and the quality of analgesia of spinal anesthesia performed with 3 ml of either 0.125% (n = 12) or 0.5% (n = 13) plain bupivacaine in 25 elderly patients undergoing orthopedic surgery. RESULTS: The initial dose's duration of action (time elapsed between the end of injection and the first patient's complaint of pain during surgery) was shorter in the group receiving 3 ml of 0.125% plain bupivacaine than in the group receiving 0.5% plain bupivacaine: 80 +/- 31 minutes versus 114 +/- 37 minutes, respectively (mean +/- SD; p less than 0.05). In 6 (50%) of 12 patients of the 0.125% group and in 2 (15%) of 13 of the 0.5% group, analgesia became insufficient during the surgical procedure, necessitating injection of an additional 1 ml (top-up) of the previous solution. All subjects obtained good anesthesia for the entire procedure. The mean dose of bupivacaine necessary for the procedure was significantly lower in the 0.125% group (4.8 +/- 1.3 mg) compared with the 0.5% group (16.1 +/- 3 mg). For a similar maximal upper level of analgesia (T4-T12 in the 0.125% group versus T2-T10 in the 0.5% group), the decrease in systolic arterial pressure was more pronounced in the 0.5% group than in the 0.125% group during the period 15-40 minutes after induction of spinal anesthesia (p less than 0.05%). The mean dose of ephedrine was threefold larger in the 0.5% group than in the 0.125% group. CONCLUSION: Continuous spinal anesthesia with small amounts of 0.125% plain bupivacaine produces effective anesthesia for orthopedic procedures in elderly patients with minimal hemodynamic changes.
Temperature monitoring during epidural anesthesia for cesarean delivery.
Tympanic, rectal, and axillary temperatures were measured and compared in 12 ASA Physical Status I and II parturients during epidural anesthesia for cesarean delivery. Measurements were performed before (T0) and at 15 (T1), 30 (T2), 45 (T3), and 60 (T4) minutes after epidural anesthesia. At birth, rectal neonatal and maternal temperatures were measured. Before anesthesia, maternal tympanic and rectal temperatures were statistically not different but higher than axillary temperature (difference, 0.5 degrees C). During anesthesia, all three maternal temperatures decreased. There was no difference for the first 45 minutes between rectal and tympanic membrane temperatures and no difference between tympanic and axillary temperatures after 30 minutes. The difference between rectal and tympanic temperatures became significant at T4. During the same period, the difference between axillary and tympanic temperatures became nonsignificant at T3 and T4. At birth, both maternal and newborn rectal temperatures were similar at 36.0 +/- 0.2 degrees C. The relative hypothermia observed in the newborns at birth after regional anesthesia was well correlated with the decrease in maternal temperature. A decrease in tympanic temperature of 1.4 degrees C developed during the course of epidural anesthesia for cesarean delivery. This decrease was underestimated by the measurement of rectal and axillary temperatures.
Alkalinization of 0.5% lidocaine for intravenous regional anesthesia.
Although remaining a controversial issue, alkalinization of lidocaine or bupivacaine may shorten the time to onset and increase the duration of the sensory block. The aim of this study was to evaluate the effect of pH adjustment on the sensory and motor blocks during intravenous regional anesthesia (IVRA) with lidocaine. Thirty-one patients scheduled for minor hand surgery performed under IVRA were randomized into two groups: Group 1 (n = 14): 1% lidocaine, 3 mg/kg, diluted with the same volume of physiological saline solution (pH = 6.63 +/- 0.05), and Group 2 (n = 17): 1% lidocaine, 3 mg/kg, diluted with the same volume of 1.4% sodium bicarbonate (pH = 7.34 +/- 0.05). final concentration of lidocaine was thus 0.5% in both groups. Sensory block was assessed by pinprick every 2 minutes in areas corresponding to six terminal nerves: ulnar, median, radial, musculocutaneous, medial cutaneous nerve of arm and intercostobrachial, and medial cutaneous nerve of forearm. The time between release of tourniquet (at the end of surgery) and appearance of pain was recorded. Motor blockade was evaluated by asking the patient to squeeze strongly a blood pressure cuff previously inflated to 40 mmHg. This maneuver was performed before and every 2 minutes after injection. No statistical differences were found between the two groups whatever the parameter studied. In conclusion, there is no advantage (over plain solutions) to using pH-adjusted lidocaine during IVRA for hand surgery.
Alkalinization of epidural 0.5% bupivacaine for cesarean section.
Controversial results have been published in the literature concerning the efficacy of alkalinization of solutions of local anesthetics to shorten the time to onset of sensory block. Fifty-two parturients scheduled for cesarean section at term under epidural anesthesia were randomly allocated to one of four groups: group 1, 0.5% plain bupivacaine (pH = 5.38 +/- 0.05); group 2, 0.5% bupivacaine pH-adjusted with 1.4% sodium bicarbonate (pH = 6.87 +/- 0.01); group 3, 0.5% bupivacaine with 1:200,000 epinephrine (pH = 4.80 +/- 0.04); and group 4, 0.5% bupivacaine pH-adjusted with 1:200,000 epinephrine (pH = 6.68 +/- 0.01). The time to onset of the sensory block was evaluated using a nerve stimulator technique. Motor blockade was assessed using Bromage's scale. No differences in the characteristics of the onset of the sensory block were observed with epinephrine-containing solutions nor with pH-adjusted local anesthetics. The maximal degree of motor blockade was not significantly different in the four groups. We conclude that alkalinization of a 0.5% bupivacaine solution is not an effective way to shorten the latency of epidural block for cesarean section.
Automated measurement of respiratory mechanics in anaesthetized ventilated patients.
The automated multilinear regression analysis method (MLRA) was recently proposed to measure respiratory mechanics in mechanically ventilated subjects [11]. The method is applicable whatever the inspiratory flow pattern and without any assumption as to the value of the parameter characterizing the non linear term of flow resistance. It was compared here in ten mechanically ventilated patients to the constant flow inflation (CFIM) method described by Rossi et al. [15]. The non linear term of flow resistance was lower in intubated patients than in corresponding isolated endotracheal tubes. When derived from the MLRA method, the values for the elastance of the respiratory system were significantly higher (p less than 0.01) than with the CFIM method, and those for the system resistance, significantly lower (p less than 0.01). These differences might be due to the recruitment of lung units in the early part of inflation. When additional resistances were inserted into the respiratory circuit, both methods proved able to determine their values accurately. They therefore appear suitable for respiratory resistance monitoring in anaesthetized ventilated patients.
A computerized method for measuring respiratory mechanics during mechanical ventilation.
In order to monitor respiratory mechanics in anesthetized ventilated subjects, an automated method was developed and tested on a physical model. The model was composed of an endotracheal tube (curvilinear resistance) coupled to a rigid air-filled box (elastance). Theoretical resistance was determined during steady-state flow experiments and theoretical elastance was estimated from the dimensions of the box. The physical model was connected to a volume-cycled ventilator. Pressure (P) and air flow (V) were measured at the outlet of the tube, and the time integral V of V was calculated. Elastance (E) and curvilinear resistance (R + K/V/) were identified by multiple linear regression analysis, for each ventilatory cycle, according to equation P = EV + RV + K/V/V. When linear regression analysis of P on V, V and /V/V was performed over the entire ventilatory cycle, E was found equal to its estimate, whereas R and K appeared different from their theoretical values. In order to improve determination of R and K, resistive pressure (Pr = P - EV) was calculated using the previously obtained value of E, and multiple linear regression of Pr on V and /V/V was performed over different fractions of the ventilatory cycle. When determined over the expiratory phase corresponding to decreasing flows, R and K were found close to their expected values. Such a method to calculate elastance and curvilinear resistance should prove convenient and efficient in measuring respiratory mechanics during mechanical ventilation.
A new approach for saphenous nerve block.
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