Seonghoon Ko

Magnesium sulfate does not reduce postoperative analgesic requirements

BackgroundBecause magnesium blocks the N-methyl-d-aspartate receptor and its associated ion channels, it can prevent central sensitization caused by peripheral nociceptive stimulation. However, transport of magnesium from blood to cerebrospinal fluid (CSF) across the blood–brain barrier is limited in normal humans. The current study was designed to evaluate whether perioperative intravenous magnesium sulfate infusion affects postoperative pain. MethodsSixty patients undergoing abdominal hysterectomy received 50 mg/kg intravenous magnesium sulfate as a bolus dose followed by a continuous infusion of 15 mg · kg−1 · h−1 for 6 h (magnesium group) or the same volume of isotonic saline (control group). At the end of surgery, serum and CSF magnesium concentration were measured in both groups. The cumulative postoperative analgesic consumption was measured to assess the analgesic effect using a patient-controlled epidural analgesia device. Pain intensities at rest and during forced expiration were evaluated at 6, 24, 48, and 72 h postoperatively. ResultsAt the end of surgery, patients in the magnesium group had significantly greater postoperative serum magnesium concentrations compared with both preoperative and control group values (P < 0.001). Despite significantly higher serum magnesium concentrations in the magnesium group, there was no significant difference in magnesium concentration measured in postoperative CSF. Cumulative postoperative analgesic doses were similar in both groups. However, there was observed an inverse relation between cumulative postoperative analgesic consumption and the CSF magnesium concentration in both groups. Visual analog pain scores at rest and during forced expiration were similar and less than 4 in both groups. ConclusionsPerioperative intravenous administration of magnesium sulfate did not increase CSF magnesium concentration and had no effects on postoperative pain. However, an inverse relation between cumulative postoperative analgesic consumption and the CSF magnesium concentration was observed. These results suggest that perioperative intravenous magnesium infusion may not be useful for preventing postoperative pain.

Propofol attenuates ischemia-reperfusion injury in the isolated rat heart

The purpose of this study was to examine the direct effects of propofol on ischemia-reperfusion injury using an isolated Langendorff rat heart preparation. Hearts were perfused with Krebs-Henseleit (K-H) solution (control); intralipid; or 10, 30, and 100 micro M propofol. Hearts were rendered globally ischemic for 25 min, then reperfusion was begun with K-H solution for 30 min. Treatment with 100 micro M propofol delayed the onset of contracture during ischemia compared with control or intralipid treatments (6.4 +/- 2.1 vs 4.4 +/- 1.4 or 4.1 +/- 0.7 min, respectively; P < 0.05). During reperfusion, 100 micro M propofol increased coronary flow and reduced lactate dehydrogenase release compared with control or intralipid treatments. After 30 min of reperfusion, left ventricular developed pressure (LVDP) returned to 55 and 76 mm Hg in the 30 and 100 micro M propofol-treated groups, respectively, whereas LVDP was 39 mm Hg in the control group. The hearts treated with 100 micro M propofol showed significantly lower left ventricular end-diastolic pressure compared with the control or intralipid groups 30 min after reperfusion (29 +/- 13 vs 48 +/- 5 or 48 +/- 11 mm Hg, respectively; P < 0.05). In histological evaluation, control and intralipid hearts had increased injury severity scores compared with hearts treated with 100 micro M propofol (1.8 +/- 0.9 and 1.7 +/- 0.8 vs 1.0 +/- 0.7, respectively; P < 0.05). In conclusion, we suggest that propofol administered before and during global myocardial ischemia has cardioprotective effects on ischemia-reperfusion injury. Implications: It is important to protect the heart from injury by ischemia and reperfusion. The current study demonstrates that in the isolated rat heart, propofol attenuates mechanical, biochemical, and histological changes causes by ischemia and reperfusion. (Anesth Analg 1997;85:719-24)

Small-dose fentanyl : Optimal time of injection for blunting the circulatory responses to tracheal intubation

This study was designed to examine the optimal time of injection of a small dose of fentanyl during anesthetic induction to attenuate circulatory responses to laryngoscopy and tracheal intubation.One hundred seventy patients were randomly assigned to one of five groups. In Groups II, III, IV, and V, patients received fentanyl (2 [micro sign]g/kg) 1, 3, 5, or 10 min before tracheal intubation, respectively. Group I patients did not receive fentanyl and served as the control group. In Groups III and IV, blood pressures were not increased, except diastolic pressure in Group III, significantly postintubation compared with preinduction values; but Groups I, II, and V showed a significant increase (P < 0.05). The 1-min postintubation values of systolic, diastolic, and mean arterial pressure in Groups III and IV were less than those in the control group (P < 0.05). Increases of heart rate in Group IV were less (P < 0.05) than those in the control group, but significant differences were not observed in Groups II, III, and V. The number of patients with tachycardia and dysrhythmia was significantly smaller in Group IV than in the control group (P < 0.05). We conclude that the most effective time to administer fentanyl to protect circulatory responses to laryngoscopy and tracheal intubation is 5 min before tracheal intubation. Implications: Fentanyl is often used to reduce the hemodynamic response to tracheal intubation. However, large doses may cause unwanted side effects. Administration of fentanyl at the optimal time reduces the dose required. Our results indicate that optimal injection time of fentanyl for intubation is 5 min before intubation. (Anesth Analg 1998;86:658-61)

EPIDURAL MORPHINE PLUS KETAMINE FOR UPPER ABDOMINAL SURGERY: IMPROVED ANALGESIA FROM PREINCISIONAL VERSUS POSTINCISIONAL ADMINISTRATION

Increased postoperative pain may be caused by central nervous system plasticity, which may be related to actions of N-methyl-D-aspartic acid (NMDA) receptors on neurons in the dorsal horn of the spinal cord. Opioids act mainly on presynaptic receptors and reduce neurotransmitter release, while ketamine antagonizes NMDA receptors and prevents wind-up and long-term potentiation. Thus, we postulated that central nervous system sensitization would be prevented more effectively by the preoperative use of these two drugs simultaneously, and the effect of preemptive analgesia would be demonstrated. Ketamine, 60 mg, and morphine, 2 mg, were injected epidurally through an indwelling catheter that was inserted at the T7-8 interspace in 60 ASA physical status class 1-2 patients. The drugs were injected before induction of anesthesia (Group 1; n = 30) or immediately after removal of a surgical specimen (Group 2; n = 30). An additional 2 mg of morphine was injected when the patients complained of resting pain. The analgesic effect was assessed by the time from first analgesic injection to second dose and the number of patients who needed supplemental injections. Complications were also noted. The duration of analgesia was longer (P < 0.01) in Group 1 (31.1 +/- 16.0 h) than in Group 2 (21.1 +/- 12.0 h), and the proportion of patients who needed supplemental injections was decreased (P < 0.05) in Group 1 (56.7%) compared with Group 2 (90.0%). The incidence of adverse effects was not different between the two groups. In conclusion, preoperative administration of morphine and ketamine is more effective in reducing postoperative pain than it is when given during the operation. (Anesth Analg 1997;84:560-3)

Blockade of Myocardial ATP-sensitive Potassium Channels by Ketamine

Background: The adenosine triphosphate (ATP)‐sensitive potassium (K sub ATP) channel underlies the increase in potassium permeability during hypoxia and ischemia. The increased outward potassium current during ischemia may be an endogenous cardioprotective mechanism. This study was designed to determine the effects of ketamine on KATP channel in rat hearts. Methods: Inside‐out and cell‐attached configurations of patch‐clamp techniques and 3 M potassium chloride‐filled conventional microelectrodes were used to investigate the effect of ketamine on KATP channel currents in single rat ventricular myocytes and on the action potential duration of rat papillary muscles, respectively. Results: Ketamine inhibited KATP channel activity in rat ventricular myocytes in a concentration‐dependent manner. In the inside‐out patches, the concentration of ketamine for half‐maximal inhibition and the Hill coefficient were 62.9 micro Meter and 0.54, respectively. In a concentration‐dependent manner, ketamine inhibited pinacidil‐ and 2,4‐dinitrophenol‐activated KATP channels in cell‐attached patches. The application of ketamine to the intracellular side of membrane patches did not affect the conduction of single‐channel currents of KATP channels. Ketamine increased the action potential duration, which was then shortened by pinacidil in a concentration‐dependent manner. Conclusions: Ketamine inhibited KATP channel activity in a concentration‐dependent manner. These results suggest that ketamine may attenuate the cardioprotective effects of the KATP channel during ischemia and reperfusion in the rat myocardium.

Cartoon distraction alleviates anxiety in children during induction of anesthesia.

BACKGROUND:We performed this study to determine the beneficial effects of viewing an animated cartoon and playing with a favorite toy on preoperative anxiety in children aged 3 to 7 years in the operating room before anesthesia induction. METHODS:One hundred thirty children aged 3 to 7 years with ASA physical status I or II were enrolled. Subjects were randomly assigned to 1 of 3 groups: group 1 (control), group 2 (toy), and group 3 (animated cartoon). The children in group 2 were asked to bring their favorite toy and were allowed to play with it until anesthesia induction. The children in group 3 watched their selected animated cartoon until anesthesia induction. Children’s preoperative anxiety was determined by the modified Yale Preoperative Anxiety Scale (mYPAS) and parent-recorded anxiety Visual Analog Scale (VAS) the night before surgery, in the preanesthetic holding room, and just before anesthesia induction. RESULTS:In the preanesthetic holding room, the group 2 mYPAS and parent-recorded anxiety VAS scores were significantly lower than those of groups 1 and 3 (mYPAS: P = 0.007; parent-recorded anxiety VAS: P = 0.02). In the operating room, the children in group 3 had the lowest mYPAS and parent-recorded anxiety VAS scores among the 3 groups (mYPAS: P < 0.001; parent-recorded anxiety VAS: P < 0.001). In group 3, the mYPAS and parent-recorded anxiety VAS scores of only 3 and 5 children were increased in the operating room compared with their scores in the preanesthetic holding room, whereas the anxiety scores of 32 and 34 children in group 1 and 25 and 32 children in group 2 had increased (P < 0.001). The number of children whose scores indicated no anxiety (mYPAS score <30) in the operating room was 3 (7%), 9 (23%), and 18 (43%) in groups 1, 2, and 3, respectively (P < 0.001). CONCLUSIONS:Allowing the viewing of animated cartoons by pediatric surgical patients is a very effective method to alleviate preoperative anxiety. Our study suggests that this intervention is an inexpensive, easy to administer, and comprehensive method for anxiety reduction in the pediatric surgical population.

Epidural verapamil reduces analgesic consumption after lower abdominal surgery

In this double-blind study, we administered lumbar epidural bupivacaine or bupivacaine plus verapamil to investigate the possible role of the calcium channel blocker, verapamil, in postoperative pain. One hundred patients (ASA physical class I or II) scheduled for lower abdominal surgery were randomly assigned to one of four groups. Group 1 received 10 mL of 0.5% epidural bupivacaine injected 15 min before incision, followed by 10 mL of epidural normal saline 30 min after incision. Group 2 received 10 mL of epidural normal saline injected before incision, followed by 10 mL of 0.5% epidural bupivacaine 30 min after incision. Group 3 received 10 mL of 0.5% epidural bupivacaine plus 5 mg of verapamil injected before incision, followed by 10 mL of epidural normal saline 30 min after incision. Group 4 received the same drugs as Group 3, in the reverse order. Pain and mood numeric rating scores, sedation scores, Prince Henry scores, patient-controlled cumulative postoperative analgesic consumption, and the incidence of side effects were assessed 2, 6, 12, 24, and 48 h after the operation in each group. Cumulative postoperative analgesic consumption in Groups 3 and 4 was significantly lower (P < 0.05) than that in Groups 1 and 2 24 and 48 h after surgery. There were no differences in the pain, mood, and sedation scores and the incidence of side effects among the four groups. We conclude that epidural verapamil decreases postoperative pain, possibly by interfering with normal sensory processing and by preventing the establishment of central sensitization. Implications: Calcium plays an important role in pain physiology at the spinal cord level. We examined the effect of bupivacaine plus verapamil (calcium channel blocker) and of bupivacaine alone. We demonstrated that the combination, administered epidurally, resulted in less postoperative analgesic consumption than bupivacaine alone. (Anesth Analg 1998;86:786-90)

Tracheal rupture after endotracheal intubation: A report of three cases

Tracheal rupture is a rare but serious complication that occurs after endotracheal intubation. It usually presents as a linear lesion in the membranous wall of the trachea, and is more prevalent in women and patients older than 50 years. The clinical manifestations of tracheal injury include subcutaneous emphysema and respiratory distress. We report the cases of three female patients of old age presenting tracheal rupture after endotracheal intubation. Two cases received surgical repair without complication and one recovered uneventfully after conservative management. We presume that the tracheal injuries were caused by over-inflation of cuff and sudden movement of the tube by positional change. Therefore, we recommend cuff pressure monitoring during general anesthesia and minimized movement of the head and neck at positional change.

Optimal nasopharyngeal temperature probe placement.

BACKGROUND:Although the nasopharynx is a commonly used temperature-monitoring site during general anesthesia, it is unknown whether the position of nasopharyngeal temperature probes placed blindly by anesthesia practitioners is optimal. The purposes of this study were (1) to determine where the nasopharyngeal mucosa is in closest proximity to the internal carotid artery (ICA) and (2) to evaluate the tip position of nasopharyngeal temperature probes that were placed by anesthesiology residents and nurse anesthetists. METHODS:In the first phase of the study, we reviewed enhanced axial computed tomography images of 100 patients to determine where the nasopharyngeal mucosa was in closest proximity to the left or the right ICA. The distance from this point to the nares was then measured in the sagittal image. In the second phase of the study, nasendoscopy was used to evaluate the positioning of nasopharyngeal temperature probes placed by anesthesiology residents (244 patients) or nurse anesthetists (116 patients). Malpositioned probes were repositioned to an optimal location, and the temperature differences were recorded. RESULTS:In the computed tomography images, the mucosa in closest proximity to the ICA was in the upper, mid-, and lower nasopharynx in 60%, 38%, and 2% of patients, respectively. The average distances between the ICA and the nasopharyngeal mucosa in the upper portion were significantly shorter than those in the lower portion (female: 9.4 vs 16.8 mm, P < 0.001; male: 12.4 vs 18.8 mm, P < 0.001). The average distances (95% prediction interval) from the nares to the upper portion of the nasopharynx through the inferior meatus were 9.1 (8.1–10.2) cm in females and 9.7 (8.6–10.8) cm in males. Temperature probes were correctly positioned in the upper or mid-nasopharynx by residents and nurses in 43% (95% confidence interval [CI], 37%–49%) and 41% (95% CI, 36%–50%), respectively. When the probe was inadvertently placed in the nasal cavity, the median (95% CI) temperature difference from the upper nasopharynx was 0.2°C (0.15°C–0.25°C). CONCLUSIONS:The closest portion of the nasopharyngeal mucosa to the ICA is within the upper or mid-nasopharynx. The depth from the nares to the upper one-third of the nasopharynx is approximately 10 cm. Less than half of nasopharyngeal temperature probes placed blindly by practitioners were optimally positioned.

Effects of intraoperative single bolus fentanyl administration and remifentanil infusion on postoperative nausea and vomiting.

Background Although the use of postoperative opioids is a well-known risk factor for postoperative nausea and vomiting (PONV), few studies have been performed on the effects of intraoperative opioids on PONV. We examined the effects of a single bolus administration of fentanyl during anesthesia induction and the intraoperative infusion of remifentanil on PONV. Methods Two hundred and fifty women, aged 20 to 65 years and scheduled for thyroidectomy, were allocated to a control group (Group C), a single bolus administration of fentanyl 2 µg/kg during anesthesia induction (Group F), or 2 ng/ ml of effect-site concentration-controlled intraoperative infusion of remifentanil (Group R) groups. Anesthesia was maintained with sevoflurane and 50% N2O. The incidence and severity of PONV and use of rescue antiemetics were recorded at 2, 6, and 24 h postoperatively. Results Group F showed higher incidences of nausea (60/82, 73% vs. 38/77, 49%; P = 0.008), vomiting (40/82, 49% vs. 23/77 30%; P = 0.041) and the use of rescue antiemetics (47/82, 57% vs. 29/77, 38%; P = 0.044) compared with Group C at postoperative 24 h. However, there were no significant differences in the incidence of PONV between Groups C and R. The overall incidences of PONV for postoperative 24 h were 49%, 73%, and 59% in Groups C, F, and R, respectively (P = 0.008). Conclusions A single bolus administration of fentanyl 2 µg/kg during anesthesia induction increases the incidence of PONV, but intraoperative remifentanil infusion with 2 ng/ml effect-site concentration did not affect the incidence of PONV.