Yang Hoon Chung

Anesthetic management of awake craniotomy with laryngeal mask airway and dexmedetomidine in risky patients

Awake craniotomy is the technique of choice for the patients with lesions on eloquent cortical areas. It is still challenging for anesthesiologists, especially in cases where the patient’s general condition is poor or with a relatively inexperienced surgeon. Occasionally the inability to control airway can lead to complications such as airway obstruction or hypercarbia, which can lead to brain bulging. Different anesthetic combinations have been reported for awake craniotomy. Nevertheless, there is still no consensus about the optimal regimen for awake craniotomy [1]. We experienced six patients with fronto-temporal lesion who needed awake surgery to preserve eloquent areas. Two patients had cardiac problems and one patient had chronic depression (Table 1). All patients received scalp nerve block with 0.75% ropivacaine and 1 : 200,000 epinephrine. Three of the patients under went “asleep-awake” technique using a laryngeal mask airway (LMA). The other patients received moderate to mild sedation. We used propofol and remifentanil infusion for sedation and two patients received dexmedetomidine infusion as an adjuvant. We did not use muscle relaxants in any cases. Mean operation time was 323 minutes and estimated blood loss was 380 ml. One patient with severe snoring refused sedation at first and stayed fully awake until the end of cortical mapping. This patient displayed marked agitation during the awake period. Therefore, we started low dose propofol-remifentanil infusion after cortical mapping and the patient underwent intermittent apnea and hypercarbia (Patient 1). Most of the patients were maintained in a sedated state during the procedures and responded properly during cortical mapping. Two patients with LMA awakened 20-30 min after stopping infusion (Patients 2 and 3), and one (Patient 3) showed moderate hypercarbia. Other patients awakened within 10 min after stopping infusion. Surgeons were satisfied with patient’s brain condition and response. One patient (Patient 5) with moderate sedation experienced extreme fear during the procedure. Others replied that it was endurable. Awake craniotomy is very stressful surgery to patients. Although it is not always consistent, there is a greater possibility of extreme fear in the patients with prior anxiety history (e.g., Patient 5). Patients with medical problems, especially with cardiovascular diseases, may not tolerate the stressful environment and may lead to hemodynamic instability. In such cases, deep sedation is preferred. According to other references, most painful procedures were head pin fixation, manipulating dura, and closure after operation. Patients can easily get stressed during these procedures despite successful scalp nerve block [2]. Therefore, maintaining deep sedation or general anesthetic status during these procedures would be more helpful for patients’ comfort. The most important problem of deep sedation is respiratory depression, and using airway device such as LMA may be a good choice [3]. But, it can also cause delayed awake and some residual effects with dull response or respiratory depression after extubation (e.g., Patients 2 and 3). Hypercarbia brings increased intracranial pressure in spite of normal oxygen saturation, and it can make the surgery harder. Yet, in practice, LMA re-insertion after neurologic test is very dangerous owing to head fixation posture.

Exposure of isoflurane-treated cells to hyperoxia decreases cell viability and activates the mitochondrial apoptotic pathway

Isoflurane has either neuroprotective or neurotoxic effects. High-dose oxygen is frequently used throughout the perioperative period. We hypothesized that hyperoxia will affect cell viability of rat pheochromocytoma (PC12) cells that were exposed to isoflurane and reactive oxygen species (ROS) may be involved. PC12 cells were exposed to 1.2% or 2.4% isoflurane for 6 or 24h respectively, and cell viability was evaluated. To investigate the effects of hyperoxia, PC12 cells were treated with 21%, 50%, or 95% oxygen and 2.4% isoflurane for 6h, and cell viability, TUNEL staining, ROS production, and expression of B-cell lymphoma 2 (BCL-2), BCL2-associated X protein (BAX), caspase-3 and beta-site APP cleaving enzyme (BACE) were measured. ROS involvement was evaluated using the ROS scavenger 2-mercaptopropiopylglycine (MPG). The viability of cells exposed to 2.4% isoflurane was lower than that of cells exposed to 1.2% isoflurane. Prolonged exposure (6h vs. 24h) to 2.4% isoflurane resulted in a profound reduction in cell viability. Treatment with 95% (but not 50%) oxygen enhanced the decrease in cell viability induced by 2.4% isoflurane alone. Levels of ROS, Bax, caspase-3 and BACE were increased, whereas expression of Bcl-2 was decreased, in cells treated with 95% oxygen plus 2.4% isoflurane compared with the control and 2.4% isoflurane plus air groups. MPG attenuated the effects of oxygen and isoflurane. In conclusion, isoflurane affects cell viability in a dose- and time-dependent manner. This effect is augmented by hyperoxia and may involve ROS, the mitochondrial apoptotic signaling pathway, and β-amyloid protein.

Effects of partial neuromuscular blockade on lateral spread response monitoring during microvascular decompression surgery

OBJECTIVE We evaluated the effect of partial neuromuscular blockade (NMB) and no NMB on successful intraoperative monitoring of the lateral spread response (LSR) during microvascular decompression (MVD) surgery. METHODS Patients were randomly allocated into one of three groups: the TOF group, the NMB was targeted to maintain two counts of train-of-four (TOF); the T1 group, maintain the T1/Tc (T1: amplitude of first twitch, Tc: amplitude of baseline twitch) ratio at 50%; and the N group, no relaxants after tracheal intubation. Successful LSR monitoring was defined as effective baseline establishment and maintenance of the LSR until dural opening. RESULTS The success rate of LSR monitoring was significantly lower in the TOF group. But, there was no significant difference between T1 and N. The detection rate of spontaneous free-run electromyography (EMG) activity was significantly higher in the N group compared with the TOF and T1 groups. CONCLUSIONS Partial NMB with a target of T1/Tc ratio at 50% allows good recording of LSR with same outcome as surgery without NMB, and reduced spontaneous EMG activity. SIGNIFICANCE We suggested the availability of partial NMB for intraoperative LSR monitoring.

Sudden persistent fetal bradycardia after spinal analgesia for labor pain

Neuraxial analgesia has become a popular technique for management of labor pain [1,2]. However, an increase in the incidence of fetal heart rate (FHR) changes after intrathecal analgesia has been reported [1,2]. Although it is known that fetal bradycardia caused by labor analgesia induction does not usually increase the risk of emergent operative deliveries [3], we experienced a case of persistent fetal bradycardia after uneventful spinal analgesia, which led to an emergency cesarean section. A 39-year-old woman (weight 60.9 kg, height 157.4 cm) at 37+1week of gestational age was admitted for induction of labor. She was diagnosed with preeclampsia and intrauterine growth retardation. On the first day, dinoprostone slow release pessary (Propess®, Bukwang Pharma, Seoul, Korea) was inserted into the vagina for seven hours. After removal of the pessary, intravenous infusion of oxytocin was started. After forty-five minutes, the cervix was fully dilated and the patient complained of severe pain (numerical rating scale, NRS; 8). We decided to perform spinal analgesia without epidural catheter insertion due to shortage of time until delivery. The parturient was laid on her left side with her body bent forwards. Spinal analgesia was performed at the L3-4 level with a 25 G Whitacre needle. A mixture of ropivacaine 3.6 mg and fentanyl 20 µg was administered intrathecally. No adverse event occurred during the procedure. One minute after the procedure, the analgesia level reached T12, and NRS score for labor pain decreased from 8 to 3. However, at about two minutes after spinal analgesia, fetal heart rate decreased to 50-70 beats per minute (bpm) (Fig. 1). Maternal blood pressure was 135/70 mmHg when fetal bradycardia developed. Oxytocin infusion was stopped. The parturient was laid in the left lateral decubitus position, and intravenous (IV) hydration was provided; however, fetal bradycardia persisted. Tocolytic agents were not used. Fourteen minutes after spinal analgesia, emergency cesarean section was performed by the attending obstetrician. Fig. 1 Fetal heart rate, and the tocogram at the time of fetal bradycardia. General anesthesia was induced by IV infusion of thiopental sodium (5 mg/kg), and succinylcholine (1 mg/kg). Anesthesia was maintained with O2, N2O and 1-1.5 vol% sevoflurane. A male baby with a body weight of 2.03 kg was delivered. He showed whole body cyanosis and could not establish self respiration at birth with a heart rate below 100 bpm. The Apgarscore was 1/2/2 at 1/5/10 minutes after birth, respectively. After endotracheal intubation, the baby was transferred to the neonatal intensive care unit. Brain computed tomography revealed hemorrhagic infarction in the right middle cerebral artery territory along with hematoma in the right occipital lobe. The baby was discharged from the hospital one month later and regular follow-up of rehabilitation was continued. FHR changes after neuraxial analgesia are not uncommon [1-3]. One possible pathophysiological mechanism is that rapid pain relief causes a short-term imbalance between maternal epinephrine and norepinephrine levels, leading to uterine hyperstimulation [1-3]. But the exact mechanisms are still unknown. The type of neuraxial block could affect the incidence of FHR abnormalities. Abrao et al. [4] reported that combined spinalepidural analgesia (CSE) is associated with a significantly higher incidence of FHR abnormalities than epidural analgesia. They suggested that faster pain relief results in a higher probability of uterine hyperactivity [4]. However, this mechanism has not been clearly demonstrated in a study. Van de Velde et al. [2] demonstrated that spinal analgesia using intrathecal bupivacaine (2.5 mg), sufentanil (1.5 µg) and epinephrine (2.5 µg) provided a equally fast pain relief as that by spinal analgesia using high-dose intrathecal sufentanil (7.5 µg) only. However, FHR changes were more frequent in those who were administered a higher dose of intrathecal sufentanil. Based on this result, it seems that high-dose intrathecal opioid plays a role in causing FHR changes, and the onset of rapid analgesia is not the most important causative factor. In our case, we used 0.2% ropivacaine (3.6 mg) and fentanyl (20 µg) intrathecally without epidural analgesia. Our dose of the intrathecal opioid was not as high as that of intrathecal sufentanil (7.5 µg), which was used by Van de Velde et al. in their study. Recently, a case-control study reported that the difference between pre- and post-analgesia pain scores and a higher sensory block height were the risk factors for fetal bradycardia following CSE analgesia for labor pain [1]. These results do not explain the development of fetal bradycardia in our case, because the sensory analgesia level after spinal analgesia had only reached T12. Fortunately, however, it has been reported that neuraxial analgesia-related FHR changes neither increase the rate of operative deliveries nor affect the maternal and neonatal outcomes [3]. In most cases, FHR changes are temporary and can be managed well with conservative methods such as oxygen supply, use of vasopressors, position change and use of tocolytic agents [3]. But, these conservative methods were ineffective in our case and a cesarean section was inevitable. As fetal distress and cesarean section are relatively common in the delivery room, other causes of FHR abnormalities should be assessed. Holdcroft and Dob [5] suggested that some iatrogenic events during regional analgesia such as an incorrect infusion dose of oxytocin can precipitate fetal distress. The other possible iatrogenic factors should also be excluded because spinal analgesia could be an innocent bystander in such cases. Cheng et al. [1] reported that the mean time between CSE and fetal bradycardia is 24.1 minutes (SD 16.93). In our case, fetal bradycardia developed after spinal analgesia within a shorter time period (2 minutes). This could just be a coincidence. But, there was no evidence of oxytocin overdose and there were no risk factors for fetal bradycardia. It is not clear which factor caused FHR abnormalities in our case. As mentioned above, there is an increased incidence of fetal bradycardia during labor analgesia due to various reasons. The anesthesiologists should remember that there is a possibility of development of fetal heart rate abnormalities after labor analgesia. Hence, careful fetal heart rate monitoring is necessary after labor analgesia.

Thoracic spondylitis induced myelopathy combined with herpetic neuralgia.

Herpetic neuralgia is a significant source of morbidity follow ing reactivation of dormant varicella zoster virus in dorsal root ganglia. Although majorities are uncomplicated, motor neuropathy may develop [1] and it can cause a diagnostic confusion with spondylitis, disc herniation, or spinal tumor. This case em phasizes the importance of careful history, clinical examination, laboratory markers and neuroimaging for diagnosis in patient with uncertain back pain. A 75-year-old, 178 cm, 79 kg male patient was referred to our pain clinic with lower back and left buttock pain (L5 to S1 der matome). He had history of two attacks of herpes zoster at the same site for 5 years and complete recovery with antiviral agent. Two weeks prior, he had undergone appendectomy. After the surgery, pneumonia was developed and treated with antibiotics. A few days later, painful vesicules had developed on left buttock and clinical evaluation by dermatologist confirmed acute herpes zoster. The vesicules resolved with antiviral agent. However, the buttock pain was sustained. In initial examination, herpetic scars were present at left buttock. He suffered from continuous lancinating pain (8 points on a 0 to 10 verbal rating scale; VRS, 0 = no pain, 10 = worst pain imaginable). He felt radicular numbness and tingling on the left leg. The motor strength was normal over both legs and sensation was mildly diminished along the left buttock and lateral upper thigh. The pain was not aggravated by position, and straight leg raise test was normal. There was no percussion tenderness in lower back and left buttock. Vital signs were stable and all laboratory findings were unremarkable, with the exception of erythrocyte sedimentation rate (ESR) level of 23 mm/hr. A diagnosis of recurrent herpes zoster with radiculopathy was made, and he was treated with gabapentin, opioids, tricyclic antidepressants, and caudal block with epidural catheter on the left L5 to S1 root with 0.75% ropivacaine 2 ml and triamcinolone 40 mg, which was diluted in normal saline

The comparison of complications on the endovascular and surgical treatment in elderly cerebral aneurysm patients

BACKGROUND The aim of this study was to compare intraoperative and postoperative complications and clinical outcome of endovascular coiling (EVT) with neurosurgical clipping (NST) under general anesthesia in the cerebral aneurysm patients older than 60 years. METHODS We retrospectively reviewed the charts, operative reports of patients who underwent EVT or NST at our hospital between January 2006 and August 2008. A total of 181 patients (EVT = 78, NST = 103) were included in this study. RESULTS The rate of intraoperative event was higher in EVT than in NST but postoperative complication and Glasgow outcome scale (GOS) at 6 months did not show statically significance in both groups. Preoperative aneurysm rupture, age and the World Federation of Neurological Surgeons grade (WFNS) were the influencing factors for outcome in both groups. Anesthetic agents, body temperature and vasoactive drugs were significantly different between the two groups but the effects of these on the outcome of patients were insignificant. CONCLUSIONS In EVT and NST, the variables related to the postoperative complications were preoperative aneurysm rupture, age and WFNS. When the elderly patients get these procedures, more close care should be considered postoperatively.