Yong-Ping Wang

Small-dose Propofol sedation attenuates the formation of reactive oxygen species in tourniquet-induced ischemia-reperfusion injury under spinal anesthesia

The release of a tourniquet produces reactive oxygen species (ROS), which can cause ischemia-reperfusion injury. We investigated the effects on ROS production in 22 adult ASA physical status I–II patients sedated with small-dose propofol infusion and IV midazolam undergoing elective total knee replacement under intrathecal anesthesia, allocated randomly to one of two groups. In the Propofol group, sedation was performed with propofol 0.2 mg/kg followed by infusion at a rate of 2 mg · kg−1 · h−1. In the Control group, IV midazolam 5 mg was given. ROS production was measured by lucigenin chemiluminescence analysis. Blood samples were obtained from the radial artery after spinal anesthesia, 1 min before release of the tourniquet and 5 and 20 min after reperfusion. The ischemic time was approximately 70 min. ROS production decreased nonsignificantly before reperfusion in both groups but increased significantly 5 and 20 min after reperfusion in the Midazolam group. In the Propofol group, no significant increase of ROS production was found. We conclude that small-dose propofol infusion attenuates ROS production in tourniquet-induced ischemia-reperfusion injury.

Low dose of intrathecal hyperbaric bupivacaine combined with epidural lidocaine for cesarean section--a balance block technique.

The present study was designed to develop a combined spinal/epidural anesthetic technique for cesarean section. We compared the effects of different doses of intrathecal hyperbaric bupivacaine (0.5%) combined with epidural lidocaine (2%). We attempted to interrupt somatosensory pathways with spinal anesthesia but to avoid acute high thoracic sympathetic block. The visceral afferent pathways were to be blocked relatively slowly with epidural lidocaine. Eighty term parturients were randomly divided into four groups. In Group A, 2.5 mg of bupivacaine intrathecally combined with 22.2 +/- 4.6 mL of lidocaine epidurally provided insufficient muscle relaxation. In Group B, 5 mg of bupivacaine with 10.1 +/- 2.0 mL of lidocaine resulted in satisfactory anesthesia with rapid onset and minimum side effects. Anesthesia in Group C (7.5 mg of bupivacaine) and Group D (10 mg of bupivacaine) was mostly due to spinal block. Complications included hypotension, nausea, and dyspnea. The combined spinal/epidural technique, using 5 mg of bupivacaine and with sufficient epidural lidocaine to reach a T4 level, had the advantages of both spinal and epidural anesthesia with few of the complications of either.

Combination of Low-dose Nalbuphine and Morphine in Patient-controlled Analgesia Decreases Incidence of Opioid-related Side Effects

BACKGROUND/PURPOSE The addition of ultra-low-dose naloxone to patient-controlled analgesia (PCA) with morphine reduces opioid-related side effects. Nalbuphine, a mixed opioid agonist-antagonist, may be able to attenuate opioid-related side effects. The goal of the present study was to investigate the effect of combined low-dose nalbuphine and morphine in PCA for postoperative pain control after gynecological surgery. METHODS This randomized, double-blind, controlled study enrolled 174 female patients who were undergoing total abdominal hysterectomy, myomectomy, or ovarian tumor excision. In the control group, the PCA formula was 1 mg/mL pure morphine. In the study group, the PCA formula was 1 mg/mL morphine and 10 microg/mL nalbuphine (1:100). Numerical rating score, PCA requirement, nausea, vomiting, use of antiemetics, pruritus, use of antipruritics, and opioid-related adverse events were investigated at 1, 2, 4, and 24 hours postoperatively. RESULTS One hundred and sixty-nine patients completed the study: 86 in the control group and 83 in the study group. The incidence of nausea was lower in the study group (41%) than in the control group (65%). The incidence of vomiting, use of antiemetics, pruritus, and use of antipruritics did not differ between the two groups. The numerical rating pain score and PCA requirements were not significantly different between the two groups. CONCLUSION Combination of low-dose nalbuphine and morphine in PCA decreases the incidence of opioid-related nausea, without affecting the analgesia and PCA requirement. This novel combination can improve the quality of PCA used for postoperative pain control after gynecological surgery.

Differential analgesic effect of tenoxicam on the wound pain and uterine cramping pain after cesarean section.

BackgroundNonsteroidal anti-inflammatory drugs (NSAIDs) are widely used to enhance opioid analgesia in the acute pain service. The question, however, of whether NSAIDs produce a similar extent of potentiation among different types of pain, has not been thoroughly investigated. Materials and MethodsA randomized, placebo-controlled, double-blind study was performed to characterize the analgesic effect of tenoxicam, a long-acting NSAID, on resting wound pain, evoked wound pain, and uterine cramping pain after cesarean section. Saline (n = 48) or 20 mg tenoxicam (n = 45) was intravenously injected immediately after clamping the umbilical cord. All patients were instructed to obtain maximal postoperative analgesia by intravenous patient-controlled morphine. ResultsTenoxicam profoundly reduced the intensity of uterine cramping pain (3.6 [2.0–5.6] versus 5.5 [3.4–6.6];p < 0.01) but had no additional effect on wound pain at rest, with movement, changing position, sitting, and walking. Intraoperative injection of 20 mg tenoxicam decreased the demand ratio for patient-controlled analgesia (PCA) and 24-hour morphine consumption by approximately 30%. ConclusionsThe data show that tenoxicam potentiates opioid analgesic effect on the somatic and visceral types of pain to different extents, and they suggest that intraoperative injection of 20 mg tenoxicam is sufficient to enhance intravenous PCA morphine on uterine cramping pain for the first 24 hours after cesarean section.

Propofol Infusion Shortens and Attenuates Oxidative Stress During One Lung Ventilation

BACKGROUND Resuming two lung ventilation (2LV) from one lung ventilation (OLV) has been proven to induce significant oxidative stress, mainly by superoxide release. Although total intravenous anesthesia and inhalational anesthesia are both used in thoracic surgery, different anesthetics may alter the oxidant/antioxidant balance. METHODS Thirty patients undergoing thoracic surgery were randomly allocated to the propofol infusion (intravenous) group or isoflurane (inhalational) group after induction and placement of a double lumen endobronchial tube. Reactive oxygen species (ROS) production and total antioxidant status (TAS) were measured during OLV and 2LV manipulations. Blood samples were taken in the lateral position before OLV (T1), immediately before resuming 2LV (T2), and 5 minutes (T3) and 20 minutes (T4) after resuming 2LV, for measurement of ROS. RESULTS ROS production increased significantly at T3 and T4 in both groups but to a lesser extent in the propofol infusion group. TAS levels increased with time in the propofol group but not in the isoflurane group. CONCLUSION Propofol infusion, compared with isoflurane inhalation, attenuates ROS production and limits it for 20 minutes after resuming 2LV from OLV. Propofol infusion may be beneficial to patients with inadequate antioxidant capacity.

Spontaneous baroreflex measurement in the assessment of cardiac vagal control.

Spontaneous baroreflex sensitivity (SBR) has been suggested to be a measure of tonic parasympathetic cardiac control. The decrease of SBR during vagal inhibition was proven before. In this study, we investigated the response of SBR during vagal activation by administering intravenous atropine and phenylephrine in eight and ten healthy volunteers respectively. Atropine was given at a rate of 0.5 µg/kg/min for 20 minutes and the infusion rate of phenylephrine was adjusted to increase the blood pressure 20 to 30 mmHg above baseline value. We found that SBR at first increased from 16.9 ± 9.5 to 41.5 ± 24.9 ms/mm Hg (p < 0.05) and then decreased to 8.9 ± 6.2 ms/mm Hg (p < 0.05 compared with the peak value) after the initiation of atropine infusion. SBR also increased significantly (27.2 ± 12.5 to 49.6 ± 11.3 ms/mm Hg, p < 0.01) during phenylephrine infusion. The authors propose SBR as a measure of cardiac vagal effect because SBR increases under vagal activation.

Effect of Combining Ultralow-dose Naloxone with Morphine in Intravenous Patient-controlled Analgesia: The Cut-off Ratio of Naloxone to Morphine for Antiemesis After Gynecologic Surgery

BACKGROUND/PURPOSE Admixing an ultralow dose of naloxone with intravenous morphine patient-controlled analgesia (PCA) has been shown to decrease postoperative nausea. However, the cut-off ratio of the naloxone-morphine admixture for antiemetic effects has not been investigated. The purpose of this study was to investigate the cut-off ratio of naloxone-morphine admixture in PCA for antiemesis after gynecologic surgery. METHODS This double-blind study enrolled 120 female patients who were scheduled for gynecologic surgery under general anesthesia. Patients were randomly allocated to one of three groups (n = 40 for each group). The concentration of naloxone and morphine respectively was 0 microg/mL and 1 mg/mL in group 1, 0.1 microg/mL and 1 mg/mL in group 2 (1:10,000), and 1 microg/mL and 1 mg/mL in group 3 (1:1000). Morphine consumption, verbal rating score of wound pain at rest and with exertion, and morphine-related side effects were investigated at 1, 2, 4 and 24 hours postoperatively. RESULTS A total of 112 patients completed the study (37 in group 1, 36 in group 2, 39 in group 3). The incidence of nausea during the postoperative 4-24 hours was significantly lower in group 3 than in group 1 (23.1% vs. 56.8%, p < 0.05). Furthermore, the overall incidence of severe nausea was significantly lower in group 3 than in group 1 (2.6% vs. 24.3%, p < 0.05) as was the rescue antiemetic requirements (5.1% vs. 24.3%, p < 0.05). However, there were no significant differences between groups 2 and 1. The pain scores (at rest and with exertion) and 24-hour morphine consumption were not significantly different among the three groups. CONCLUSION The antiemetic efficacy of ultralow-dose naloxone combined with PCA morphine is limited by a cut-off ratio of naloxone to morphine of 1:10,000.

Arteriovenous concentration differences of propofol during and after a stepdown infusion

To compare the arterial and venous concentration differences of propofol, six healthy adult patients received a propofol infusion by the Bristol three-stage manual stepdown technique. Both the mean arterial and venous concentrations of propofol remained relatively stable during the 40-min infusion. Simultaneous blood sampling from the artery and vein during the infusion period resulted in arterial concentrations significantly higher than venous concentrations. This relationship was reversed after stopping the infusion. The mean ± SD (range) venous to arterial concentration differences were −28.8% ± 18.3% (−71% to 1.7%) during the infusion and 18.9% ± 13.4%(−1.5% to 40.9%)after the infusion. We conclude that venous concentrations were not useful to estimate the arterial value during and after a stepdown propofol infusion. Arterial sampling is more appropriate in pharmacologic studies of propofol. (Anesth Analg 1994;79:1148–50)

Effects of respiratory time ratio on heart rate variability and spontaneous baroreflex sensitivity

Paced breathing is a frequently performed technique for cardiovascular autonomic studies. The relative timing of inspiration and expiration during paced breathing, however, is not consistent. We, therefore, examined whether indexes of heart rate variability and spontaneous baroreflex sensitivity would be affected by the respiratory time ratio that is set. We studied 14 healthy young adults who controlled their breathing rates to either 0.1 or 0.25 Hz in the supine and sitting positions. Four different inspiratory-to-expiratory time ratios (I/E) (uncontrolled, 1:1, 1:2, and 1:3) were examined for each condition in a randomized order. The results showed spectral indexes of heart rate variability and spontaneous baroreflex sensitivity were not influenced by the I/E that was set during paced breathing under supine and sitting positions. Portas and Guziks indexes of heart rate asymmetry were also not different at various I/E during 0.1-Hz breathing, but had larger values at 1:1 during 0.25-Hz breathing, although significant change was found in the sitting position only. At the same time, Portas and Guziks indexes obtained during 0.1-Hz breathing were greater than during 0.25-Hz breathing in both positions. The authors suggest that setting the I/E during paced breathing is not necessary when measuring spectral indexes of heart rate variability and spontaneous baroreflex sensitivity under the conditions used in this study. The necessity of paced breathing for the measurement of heart rate asymmetry, however, requires further investigation.

Lack of intravenous lidocaine effects on HRV changes of tracheal intubation during induction of general anesthesia.

BACKGROUND Intravenous lidocaine has been widely used for suppressing the autonomic activation from tracheal intubation during induction of general anesthesia. Conventionally, researches of its effectiveness through assessment of heart rate and blood pressure changes obtained by common clinical methods result in the conclusions deduced of much controversy. Heart rate variability is a noninvasive measurement of autonomic regulation and is suitable for the study of this subject. METHODS 36 ASA class I-II patients undergoing general anesthesia were divided into 3 groups. Besides induction agents, intravenous lidocaine was given 5 min before tracheal intubation in group A, 3 min before intubation in group B and nothing in group C. HRV spectral powers were measured at awake state, anesthetized state before tracheal intubation and anesthetized state after tracheal intubation by time frequency spectral analysis method and comparison was made between the three groups. RESULTS The HRV spectral power in high frequency (HF) and mid-frequency (MF) power bands and their ratios (MF/HF) were not significantly different among the 3 groups during the 3 observation periods. CONCLUSIONS There was no evidence to indicate the effectiveness of intravenous lidocaine on the autonomic regulation during tracheal intubation under the influence of induction agents used in general anesthesia.