Igor Luginbuehl

Transient Neurologic Symptoms after Spinal Anesthesia A Lower Incidence with Prilocaine and Bupivacaine than with Lidocaine

Background Recent evidence suggests that transient neurologic symptoms (TNSs) frequently follow lidocaine spinal anesthesia but are infrequent with bupivacaine. However, identification of a short‐acting local anesthetic to substitute for lidocaine for brief surgical procedures remains an important goal. Prilocaine is an amide local anesthetic with a duration of action similar to that of lidocaine. Accordingly, the present, prospective double‐blind study compares prilocaine with lidocaine and bupivacaine with respect to duration of action and relative risk of TNSs. Methods Ninety patients classified as American Society of Anesthesiologists physical status I or II who were scheduled for short gynecologic procedures under spinal anesthesia were randomly allocated to receive 2.5 ml 2% lidocaine in 7.5% glucose, 2% prilocaine in 7.5% glucose, or 0.5% bupivacaine in 7.5% glucose. All solutions were provided in blinded vials by the hospital pharmacy. Details of spinal puncture, extension and regression of spinal block, and the times to reach discharge criteria were noted. In the evening of postoperative day 1, patients were evaluated for TNSs by a physician unaware of the drug administered and the details of the anesthetic procedure. Results Nine of 30 patients receiving lidocaine experienced TNSs, 1 of 30 patients receiving prilocaine (P = 0.03) had them, and none of 30 patients receiving bupivacaine had TNSs. Times to ambulate and to void were similar after lidocaine and prilocaine (150 vs. 165 min and 238 vs. 253 min, respectively) but prolonged after bupivacaine (200 and 299 min, respectively; P < 0.05). Conclusions Prilocaine may be preferable to lidocaine for short surgical procedures because it has a similar duration of action but a lower incidence of TNSs.

Cerebrovascular carbon dioxide reactivity in children anaesthetized with propofol

Background: Propofol, by virtue of its favourable pharmacokinetic profile, is suitable for maintenance of anaesthesia by continuous infusion during neurosurgical procedures in adults. It is gaining popularity for use in paediatric patients. To determine the effects of propofol on carbon dioxide cerebrovascular reactivity in children, middle cerebral artery blood flow velocity was measured at different levels of endtidal (PECO2) by transcranial Doppler sonography.

Hemodynamic and Respiratory Effects of Pediatric Urological Retroperitoneal Laparoscopic Surgery: A Prospective Study

PURPOSE Our understanding of the effects of retroperitoneal CO(2) insufflation on cardiopulmonary variables in children remains limited. This study was designed to investigate prospectively the effect of CO(2) insufflation in a pediatric population undergoing retroperitoneal laparoscopic surgery. MATERIALS AND METHODS We prospectively evaluated a consecutive series of patients enrolled between July 2003 and August 2004. Anesthesia was administered following a standardized protocol. Data collection included respiratory rate, PAP, O(2) saturation, ETCO(2), HR, MAP, electrocardiogram and insufflation pressure. All variables were recorded before, during and after CO(2) insufflation at regular intervals of 1 to 2 minutes, with up to 23 measurements recorded for each period. RESULTS A total of 18 participants were recruited. Mean +/- SD for age and weight were 79.4 +/- 53.2 months and 26.7 +/- 15.5 kg, respectively. Mean retroperitoneal CO(2) insufflation pressure was kept at 12 mm Hg. Significant differences (p <0.05) in average ETCO(2), PAP and MAP were noted after CO(2) insufflation compared to baseline (pre-pneumoretroperitoneum) values. HR and temperature did not change. At completion of the laparoscopic intervention physiological variables exhibited a trend to return to baseline values. CONCLUSIONS This prospective study documents significant changes in systemic hemodynamic variables that seem to be directly associated with the insufflation of CO(2) during pediatric retroperitoneal laparoscopic surgery. This ongoing evaluation confirms the effect of laparoscopic urological surgery and CO(2) insufflation on cardiopulmonary function in children.

The effect of nitrous oxide on cerebrovascular reactivity to carbon dioxide in children during propofol anesthesia.

Nitrous oxide (N2O) increases cerebral blood flow when used alone and in combination with propofol. We investigated the effects of N2O on cerebrovascular CO2 reactivity (CCO2R) during propofol anesthesia in 10 healthy children undergoing elective urological surgery. Anesthesia consisted of a steady-state propofol infusion and a continuous caudal epidural block. A transcranial Doppler probe was used to measure middle cerebral artery blood flow velocity. Randomization determined the sequence order of N2O (N2O/air or air/N2O) and end-tidal (ET)co2 concentration (25, 35, 45, and 55 mm Hg) using an exogenous source of CO2. At steady state, three sets of measurements of middle cerebral artery blood flow velocity, mean arterial blood pressure, and heart rate were recorded. A linear preservation of CCO2R was observed above 35 mm Hg of ETco2, irrespective of N2O. A decrease in CCO2R to 1.4%–1.9% per millimeters of mercury was seen in the hypocapnic range (ETco2 25–35 mm Hg) with both air and N2O. We conclude that N2O does not affect CCO2R during propofol anesthesia in children. When preservation of CCO2R is required, the combination of N2O with propofol anesthesia in children would seem suitable. The cerebral vasoconstriction caused by propofol would imply that hyperventilation to ETco2 values less than 35 mm Hg may not be required because no further reduction in cerebral blood flow velocity would be achieved.

The effect of nitrous oxide on cerebral blood flow velocity in children anesthetized with propofol.

Background: Propofol for maintenance of anesthesia by continuous infusion is gaining popularity for use in pediatric patients. Nitrous oxide (N2O) has been shown to increase cerebral blood flow velocity (CBFV) in both children and adults. To determine the effects of N2O on middle cerebral artery blood flow velocity (Vmca) during propofol anesthesia in children, Vmca was measured with and without N2O using transcranial Doppler (TCD) sonography.

Impact of anesthetic agents on cerebrovascular physiology in children

The role of the pediatric neuroanesthetist is to provide comprehensive care to children with neurologic pathologies. The cerebral physiology is influenced by the developmental stage of the child. The understanding of the effects of anesthetic agents on the physiology of cerebral vasculature in the pediatric population has significantly increased in the past decade allowing a more rationale decision making in anesthesia management. Although no single anesthetic technique can be recommended, sound knowledge of the principles of cerebral physiology and anesthetic neuropharmacology will facilitate the care of pediatric neurosurgical patients.

The effect of remifentanil on cerebral blood flow velocity in children anesthetized with propofol

Background : Cerebrovascular stability and rapid anesthetic emergence are desirable features of a neuroanesthetic regimen. In this randomized crossover study the effect of a low‐dose remifentanil infusion on cerebral blood flow velocity (CBFV) in children anesthetized with propofol was evaluated.

The cerebrovascular response to hypocapnia in children receiving propofol.

Hypocapnia is used to treat acute increases in intracranial pressure during neurosurgery. Cerebrovascular reactivity to carbon dioxide (CCO2R) is preserved above 35 mm Hg ETco2 in children during propofol anesthesia; however, a plateau effect has been suggested below 35 mm Hg. To further delineate this phenomenon, we measured CCO2R by transcranial Doppler (TCD) sonography over small increments in ETco2 in 27 healthy children. Anesthesia comprised a standardized propofol infusion and a caudal epidural block. A TCD probe was placed to measure middle cerebral artery blood flow velocity (Vmca). ETco2 was adjusted between 24 and 40 mm Hg at 1–2 mm Hg increments using an exogenous source of CO2. There was an exponential relationship between ETco2 and Vmca above an ETco2 value of 30 mm Hg (r = 0.82). However, Vmca did not change with ETco2 less than 30 mm Hg (r = 0.06). There were no significant changes in heart rate or arterial blood pressure. We conclude that when contemplating methods to decrease brain volume and intracranial pressure, hyperventilation to ETco2 values less than 30 mm Hg may not be necessary in children receiving propofol, as no further reduction in cerebral blood flow velocity will be achieved.

Cerebral blood flow velocity in children anaesthetized with desflurane.

Background: Desflurane allows for rapid emergence and changes in depth of anaesthesia which makes it especially suitable for neuroanaesthesia. This study was designed to determine the effects of different desflurane concentrations on cerebral blood flow velocity (CBFV) in healthy children.

Effect of Nitrous Oxide Exposure during Surgery on the Homocysteine Concentrations of Children

Background: Nitrous oxide converts vitamin B12 to its nonmetabolically active form, inhibits methionine synthase, and results in an elevation of plasma total homocysteine (tHcy). The authors investigated the effect of nitrous oxide anesthesia on the plasma tHcy concentrations in children the morning after surgery and whether blood concentrations of folate and vitamins B12 and B6 were associated with any potential increase. Methods: The authors measured plasma tHcy concentrations in 32 children before and 24 h after initial exposure to nitrous oxide (≥2 h). Genotype for methylenetetrahydrofolate reductase C677T and blood concentrations of folate, vitamins B12 and B6, and methylmalonic acid were measured before surgery. Results: The median age of participants was 11 months (3–126 months). The median (first, third quartile) postoperative plasma tHcy concentration was significantly higher than the preoperative concentration (6.4 [4.7, 8.9] vs. 5.1[4.1, 6.4] &mgr;M, P < 0.0001), a 25% (2%, 42%) relative increase. Six of 28 (21%) children with normal, age-appropriate, preexposure plasma tHcy concentrations had postoperative plasma tHcy concentrations greater than the cutoff values. The duration of nitrous oxide exposure was associated positively with the rise in plasma tHcy concentration (R 2 = 0.696, P = < 0.001). Conclusion: Exposure to ≥2 h nitrous oxide is associated with a small, albeit statistically significant, increase in postoperative plasma tHcy concentrations the morning after surgery in young children. The clinical significance of this increase is unknown.