Somatosensory Evoked Potentials suppression due to remifentanil during spinal operations; a prospective clinical study

Intra-articular remifentanil on postoperative pain in knee arthroscopic surgery; a double blind randomized clinical trial

BACKGROUND

We aimed to assess the efficacy of intra-articular remifentanil in relieving postoperative pain after knee arthroscopy.

METHODS

We conducted a double-blind randomized clinical trial study on 60 patients. Patients were divided into two equal groups. The control group received 25 ml of intra-articular normal saline, and the intervention group received 200 μg of remifentanil dissolved in 25 ml of saline. We evaluated at rest postoperative pain at 1, 3, 6, 12, 18, and 24 h after the surgery using the Visual Analog Scale (VAS). Patients with VAS scores of 4 or more received meperidine (pethidine). The first time meperidine was requested and the total amount of meperidine consumed was recorded.

RESULTS

Out of 60 patients, 49 were male (81.6%), and the mean age of participants was 32.71 (7.02) years. An hour after the surgery, the control group showed a mean VAS score of 8.66 (1.26), and decreased to 2.53 (1.67) at the end of 24 h. The intervention group started with a mean VAS score of 2.23 (1.81) and ended at 0.10 (0.305). All patients in the control group and 11 (36.7%) patients in the intervention group asked for analgesics during follow-up. The mean total meperidine dose in the control and intervention groups was 108.33 (23.97) mg and 13.33 (19.40) mg, respectively (P < 0.001; 95% confidence interval of the difference 83.72 to 106.27).

CONCLUSIONS

Intra-articular remifentanil may decrease postoperative pain and analgesic requirements in patients undergoing knee arthroscopy.

Anesthesia management of neonates and infants requiring intraoperative neurophysiological monitoring: A concise review

Intraoperative neurophysiological monitoring is currently used to prevent intraoperative spinal cord and nerve injuries during neonatal and infant surgeries. However, its use is associated with some issues in these young children. The developing nervous system of infants and neonates requires higher stimulation voltage than adults to ensure adequate signals, thereby necessitating reduced anesthesia dose to avoid suppressing motor and somatosensory-evoked potentials. Excessive dose reduction, however, increases the risk of unexpected body movement when used without neuromuscular blocking drugs. Most recent guidelines for older children and adults recommend total intravenous anesthesia with propofol and remifentanil. However, the measurement of anesthetic depth is less well understood in infants and neonates. Size factors and physiological maturation cause pharmacokinetics differences compared with adults. These issues make neurophysiological monitoring in this young population a challenge for anesthesiologists. Furthermore, monitoring errors such as false-negative results immediately affect the prognosis of motor and bladder-rectal functions in patients. Therefore, anesthesiologists need to be familiar with the effects of anesthetics and age-specific neurophysiological monitoring challenges. This review provides an update regarding available anesthetic options and their target concentration in neonates and infants requiring intraoperative neurophysiological monitoring.

Perioperative Care of Patients Undergoing Major Complex Spinal Instrumentation Surgery: Clinical Practice Guidelines From the Society for Neuroscience in Anesthesiology and Critical Care

Evidence-based standardization of the perioperative management of patients undergoing complex spine surgery can improve outcomes such as enhanced patient satisfaction, reduced intensive care and hospital length of stay, and reduced costs. The Society for Neuroscience in Anesthesiology and Critical Care (SNACC) tasked an expert group to review existing evidence and generate recommendations for the perioperative management of patients undergoing complex spine surgery, defined as surgery on 2 or more thoracic and/or lumbar spine levels. Institutional clinical management protocols can be constructed based on the elements included in these clinical practice guidelines, and the evidence presented.

Somatosensory evoked potential loss due to intraoperative pulse lavage during spine surgery: case report and review of signal change management

Intraoperative neurophysiologic monitoring (IONM) includes various neurophysiologic tests which assess the functional integrity of the central and peripheral nervous systems during surgical procedures which place these structures at risk for iatrogenic injury. The rational for using IONM is to provide timely feedback of changes in neural function to enable the reversal of such insult before the development of irreversible neural injury. There are various causes of intraoperative loss of neuromonitoring signals and it is important to systematically rule out all possible causes quickly and thoroughly in order to target the cause of signal loss, correct it and take measures to prevent the same in the future. One such rare cause, is targeted and pressurized cold (room temperature) irrigation of the surgical site, which may induce irritation and vasospasm leading to ischemia of the affected portion of the spinal cord, hence leading to signal changes. We present this case to stress the importance of having knowledgeable members of the team who are well acquainted with all aspects of monitoring in close proximity to the operating room, so as to minimize troubleshooting time. Furthermore, we suggest the use of warm (body temperature) saline during irrigation to the surgical site, especially when using pressurized irrigation systems.

Venlafaxine and oxycodone have different effects on spinal and supraspinal activity in man: a somatosensory evoked potential study

AIMS

Opioids and antidepressants that inhibit serotonin and norepinephrine reuptake (SNRI) are recognized as analgesics to treat severe and moderate pain, but their mechanisms of action in humans remain unclear. The present study aimed to explore how oxycodone (an opioid) and venlafaxine (an SNRI) modulate spinal and supraspinal sensory processing.

METHODS

Twenty volunteers were included in a randomized, double-blinded, three-way (placebo, oxycodone, venlafaxine), crossover study. Spinal and full scalp cortical evoked potentials (EPs) to median nerve stimulation were recorded before and after 5 days of treatment. Assessment of the central effects of the three treatments involved: (i) amplitudes and latencies of spinal EPs (spinal level); (ii) amplitudes and latencies of the P14 potential (subcortical level); (iii) amplitudes and latencies of early and late cortical EPs (cortical level); (iv) brain sources underlying early cortical Eps; and (v) brain networks underlying the late cortical EPs.

RESULTS

In the venlafaxine arm, the spinal P11 and the late cortical N60-80 latencies were reduced by 1.8% [95% confidence interval (CI) 1.7%, 1.9%) and 5.7% (95% CI 5.3%, 6.1%), whereas the early cortical P25 amplitude was decreased by 7.1% (95%CI 6.1%, 8.7%). Oxycodone increased the subcortical P14 [+25% (95% CI 22.2%, 28.6%)], early cortical N30 [+12.9% (95% CI 12.5%, 13.2%)] amplitudes and the late cortical N60-80 latency [+2.9% (95% CI 1.9%, 4.0%)]. The brainstem and primary somatosensory cortex source strengths were increased by 66.7% (95% CI 62.5%, 75.0%) and 28.8% (95% CI 27.5%, 29.6%) in the oxycodone arm, whereas the primary somatosensory cortex strength was decreased in the venlafaxine arm by 18.3% (95% CI 12.0%, 28.1%).

CONCLUSIONS

Opioids and SNRI drugs exert different central effects. The present study contributed to the much-needed human models of the mechanisms of action of drugs with effects on the central nervous system.

How to assess prognosis after cardiac arrest and therapeutic hypothermia

The prognosis of patients who are admitted in a comatose state following successful resuscitation after cardiac arrest remains uncertain. Although the introduction of therapeutic hypothermia (TH) and improvements in post-resuscitation care have significantly increased the number of patients who are discharged home with minimal brain damage, short-term assessment of neurological outcome remains a challenge. The need for early and accurate prognostic predictors is crucial, especially since sedation and TH may alter the neurological examination and delay the recovery of motor response for several days. The development of additional tools, including electrophysiological examinations (electroencephalography and somatosensory evoked potentials), neuroimaging and chemical biomarkers, may help to evaluate the extent of brain injury in these patients. Given the extensive literature existing on this topic and the confounding effects of TH on the strength of these tools in outcome prognostication after cardiac arrest, the aim of this narrative review is to provide a practical approach to post-anoxic brain injury when TH is used. We also discuss when and how these tools could be combined with the neurological examination in a multimodal approach to improve outcome prediction in this population.

[Intraoperative electrophysiological monitoring with evoked potentials]

During the last 30 years intraoperative electrophysiological monitoring (IOEM) has gained increasing importance in monitoring the function of neuronal structures and the intraoperative detection of impending new neurological deficits. The use of IOEM could reduce the incidence of postoperative neurological deficits after various surgical procedures. Motor evoked potentials (MEP) seem to be superior to other methods for many indications regarding monitoring of the central nervous system. During the application of IOEM general anesthesia should be provided by total intravenous anesthesia with propofol with an emphasis on a continuous high opioid dosage. When intraoperative MEP or electromyography guidance is planned, muscle relaxation must be either completely omitted or maintained in a titrated dose range in a steady state. The IOEM can be performed by surgeons, neurologists and neurophysiologists or increasingly more by anesthesiologists. However, to guarantee a safe application and interpretation, sufficient knowledge of the effects of the surgical procedure and pharmacological and physiological influences on the neurophysiological findings are indispensable.