Anesthetic Adjunct Research Articles

Dexmedetomidine as an anaesthetic adjunct for management of difficult airway in a patient with facial injury following bear maul

The management of difficult airway is one of the most challenging tasks for the anaesthesiologist. Life threatening cannot intubate and cannot ventilate situation can be avoided by performing awake-fibreoptic intubation. Although there are many techniques described for fibreoptic intubation but relative merits and demerits of each technique should be considered. The key to successful awakefibreoptic intubation depends upon the meticulous preparation of the patient and the equipments. Many methods of sedation have been described but theirs side effects are the limitations. Dexmedetomidine, a selective alpha2 adrenergic agonist, has unique property of conscious sedation. Besides, dexmedetomidine has additional property of analgesia, reflex blunting and anti-sialogogue, which can further improve the success rate of awake-fibreoptic intubation in cases with difficult airway. We described a case of bear maul of face with anticipated difficult airway successfully conducted awake-fibreoptic intubation with the use of dexmedetomidine.Journal of Society of Anesthesiologists of Nepal 2015; 2(2): 77-79

The cardiopulmonary effects of dexmedetomidine infusions in dogs during isoflurane anesthesia

ObjectiveTo determine the cardiopulmonary changes associated with intravenous (IV) infusions of dexmedetomidine at equipotent isoflurane-dexmedetomidine concentrations compared with isoflurane alone. Study designProspective, randomized, crossover experiment. AnimalsSix adult intact female mixed-breed dogs weighing (mean ± SD [range]) 23.3 ± 3.8 (17.8–29.4) kg. MethodsAnesthesia was induced and maintained with isoflurane in oxygen. Measurements of respiratory rate (fR), heart rate (HR), systemic and pulmonary arterial pressures (SAP, DAP, MAP, MPAP), central venous pressure (CVP), pulmonary arterial occlusion pressure (PAOP), cardiac index (CI), left and right ventricular stroke work index (LVSWI, RVSWI), systemic and pulmonary vascular resistance index (SVRI, PVRI), arteriovenous shunt ( Q˙s/Q˙t), oxygen delivery ( D˙O2), oxygen extraction ratio (O2ER), oxygen consumption, arterial and mixed venous blood gases, and arterial packed cell volume (PCV) were obtained 30 minutes after instrumentation at an end-tidal isoflurane concentration (Fe’Iso) of 1.73 ± 0.02% (1.3 MAC). Dexmedetomidine was administered IV at 0.5 or 3 μg kg−1 over 6 minutes followed by an infusion at 0.5 (LD) or 3 μg kg−1 hour−1 (HD), respectively, with Fe’Iso at 1.41 ± 0.02 (LD) or 0.72 ± 0.09% (HD). Measurements were taken at 10, 30, 60, 90, 120, 150 and 180 minutes after the start of the infusion. ResultsThe low dose produced significant decreases in HR, increases in SAP, DAP, CVP, MPAP, PAOP and LVSWI, but no change in CI. HD produced significant increases in SAP, MAP, DAP, CVP, PAOP, SVRI, LVSWI, O2ER and PCV and significant decreases in CI and D˙O2. There were significant differences between treatments in HR, MAP, DAP, CVP, MPAP, PAOP, CI, SVRI, HCO3-, SBE, D˙O2, O2ER and Q˙s/Q˙t. Conclusions and clinical relevanceCardiopulmonary changes associated with LD were within clinically accepted normal ranges whereas HD produced clinically significant changes. The LD may be useful as an anesthetic adjunct in healthy dogs.

Effectiveness of dexmedetomidine use in general anesthesia to prevent postoperative shivering: a systematic review protocol.

Review question/objective The following question guides the systematic review: In adult patients undergoing general anesthesia, what is the effectiveness of dexmedetomidine, compared to placebo, in preventing shivering in the first two hours after surgery? The objective of this systematic review is to synthesize the best available evidence on the efficacy of dexmedetomidine in preventing the occurrence of postanesthetic shivering. Inclusion Criteria Types of participants This review will consider studies that include adult patients between 18 and 70 years of age receiving general anesthesia for any surgical procedure in any clinical setting. Only studies examining patients with American Society of Anesthesiologist physical status 1 or 2 will be considered. Studies including anesthetic techniques other than general anesthesia will be excluded. Studies including patients less than 18 years of age will also be excluded, as the incidence of postanesthetic shivering in this population is low and the risk to benefit ratio doesn’t warrant prophylactic treatment. Type of intervention This review will evaluate the effectiveness of dexmedetomidine in preventing postanesthetic shivering. Studies that compare preoperative or intraoperative administration of dexmedetomidine to placebo will be considered. Only intravenous administration techniques of dexmedetomidine will be included. Studies to be examined will include dexmedetomidine administration times of 30 minutes prior to induction of general anesthesia and any other intraoperative administration times. Dexmedetomidine boluses and infusions will be completed prior to patient arrival to post-anesthesia care unit. Studies will be excluded if the dexmedetomidine is administered during post-anesthesia care unit stay. Examined studies will include the administration of dexmedetomidine as a one-time bolus, continuous infusion, or a combination of bolus and infusion doses. Only studies evaluating dexmedetomidine as the sole pharmacological agent in the prevention of postanesthetic shivering will be considered. Studies evaluating dexmedetomidine for the treatment of postanesthetic shivering will be excluded. Types of outcomes This review will consider studies that include the following outcome measure: presence of postanesthetic shivering observed in the post-anesthesia care unit during the first hour after the completion of surgery. Intensity of shivering will be measured with variations of a shivering scale validated by Crossley and TRUNCATED AT 350 WORDS

Scientometrics of anesthetic drugs and their techniques of administration, 1984-2013.

The aim of this study was to assess progress in the field of anesthetic drugs over the past 30 years using scientometric indices: popularity indices (general and specific), representing the proportion of articles on a drug relative to all articles in the field of anesthetics (general index) or the subfield of a specific class of anesthetics (specific index); index of change, representing the degree of growth in publications on a topic from one period to the next; index of expectations, representing the ratio of the number of articles on a topic in the top 20 journals relative to the number of articles in all (>5,000) biomedical journals covered by PubMed; and index of ultimate success, representing a publication outcome when a new drug takes the place of a common drug previously used for the same purpose. Publications on 58 topics were assessed during six 5-year periods from 1984 to 2013. Our analysis showed that during 2009–2013, out of seven anesthetics with a high general popularity index (≥2.0), only two were introduced after 1980, ie, the inhaled anesthetic sevoflurane and the local anesthetic ropivacaine; however, only sevoflurane had a high index of expectations (12.1). Among anesthetic adjuncts, in 2009–2013, only one agent, sugammadex, had both an extremely high index of change (>100) and a high index of expectations (25.0), reflecting the novelty of its mechanism of action. The index of ultimate success was positive with three anesthetics, ie, lidocaine, isoflurane, and propofol, all of which were introduced much longer than 30 years ago. For the past 30 years, there were no new anesthetics that have produced changes in scientometric indices indicating real progress.

N-methyl-D-aspartate receptor channel blocker-like discriminative stimulus effects of nitrous oxide gas.

Nitrous oxide (N2O) gas is a widely used anesthetic adjunct in dentistry and medicine that is also commonly abused. Studies have shown that N2O alters the function of the N-methyl-d-aspartate (NMDA), GABAA, opioid, and serotonin receptors among others. However, the receptors systems underlying the abuse-related central nervous system effects of N2O are unclear. The present study explores the receptor systems responsible for producing the discriminative stimulus effects of N2O. B6SJLF1/J male mice trained to discriminate 10 minutes of exposure to 60% N2O + 40% oxygen versus 100% oxygen served as subjects. Both the high-affinity NMDA receptor channel blocker (+)-MK-801 maleate [(5S,10R)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine maleate] and the low-affinity blocker memantine partially mimicked the stimulus effects of N2O. Neither the competitive NMDA antagonist, CGS-19755 (cis-4-[phosphomethyl]-piperidine-2-carboxylic acid), nor the NMDA glycine-site antagonist, L701-324 [7-chloro-4-hydroxy-3-(3-phenoxy)phenyl-2(1H)-quinolinone], produced N2O-like stimulus effects. A range of GABAA agonists and positive modulators, including midazolam, pentobarbital, muscimol, and gaboxadol (4,5,6,7-tetrahydroisoxazolo[4,5-c]pyridine-3-ol), all failed to produce N2O-like stimulus effects. The μ-, κ-, and δ-opioid agonists, as well as 5-hydroxytryptamine (serotonin) 1B/2C (5-HT1B/2C) and 5-HT1A agonists, also failed to produce N2O-like stimulus effects. Ethanol partially substituted for N2O. Both (+)-MK-801 and ethanol but not midazolam pretreatment also significantly enhanced the discriminative stimulus effects of N2O. Our results support the hypothesis that the discriminative stimulus effects of N2O are at least partially mediated by NMDA antagonist effects similar to those produced by channel blockers. However, as none of the drugs tested fully mimicked the stimulus effects of N2O, other mechanisms may also be involved.

Effects of sevoflurane versus other general anaesthesia on emergence agitation in children.

Effects of sevoflurane versus other general anaesthesia on emergence agitation in children.

Systematic review/Meta-analysis Systematic assessment of dexmedetomidine as an anesthetic agent: a meta-analysis of randomized controlled trials

IntroductionHere we aimed to study the effectiveness of dexmedetomidine as an anesthetic adjunct in surgery.Material and methodsA systematic evaluation was performed on published clinical trials. Major databases such as Medline database were employed to search and identify relevant studies and then Rev.Man 5 was used for meta-analysis as well as forest plots. Mean difference (MD) was chosen as the effect size for measurement data, while odds ratio (OR) was calculated for enumeration data.ResultsA total of 18 studies met the inclusion criteria. The postoperative heart rate and mean arterial pressure for the dexmedetomidine group were significantly lower than the control group (combined MDs were –14.12 and –9.96). The incidence rates of postoperative nausea and vomiting, chills, and shivering of the dexmedetomidine group were lower than the control group (pooled ORs were 0.41, 0.21 and 0.14, respectively). However, the occurrence rates of bradycardia and hypotension in the dexmedetomidine group were higher than the control group (pooled ORs were 5.14 and 3.00).ConclusionsDexmedetomidine can stabilize blood pressure and heart rate, and prevent postoperative adverse reactions. However, patients with original hypovolemia or heart block should be cautious. Besides, the quality of such studies should be improved in methodology to evaluate their efficacy and safety comprehensively.

Effects of lidocaine administration via continuous rate infusion on the minimum alveolar concentration of isoflurane in New Zealand White rabbits (Oryctolagus cuniculus)

To evaluate the effect of a continuous rate infusion (CRI) of lidocaine on the minimum alveolar concentration (MAC) of isoflurane in rabbits. Five 12-month-old female New Zealand White rabbits (Oryctolagus cuniculus). Rabbits were anesthetized with isoflurane. Baseline isoflurane MAC was determined by use of the tail clamp technique. A loading dose of lidocaine (2.0 mg/kg, IV) was administered followed by a CRI of lidocaine at 50 μg/kg/min. After 30 minutes, isoflurane MAC was determined. Another loading dose was administered, and the lidocaine CRI then was increased to 100 μg/kg/min. After 30 minutes, isoflurane MAC was determined again. Plasma samples were obtained for lidocaine analysis after each MAC determination. Baseline isoflurane MAC was 2.09%, which was similar to previously reported values in this species. Lidocaine CRI at 50 and 100 μg/kg/min induced significant reductions in MAC. The 50 μg/kg/min CRI resulted in a mean plasma lidocaine concentration of 0.654 μg/mL and reduction of MAC by 10.5%. The 100 μg/kg/min CRI of lidocaine resulted in a mean plasma concentration of 1.578 μg/mL and reduction of MAC by 21.7%. Lidocaine also induced significant decreases in arterial blood pressure and heart rate. All cardiopulmonary variables were within reference ranges for rabbits anesthetized with inhalation anesthetics. No adverse effects were detected; all rabbits had an uncomplicated recovery from anesthesia. Lidocaine administered as a CRI at 50 and 100 μg/kg/min decreased isoflurane MAC in rabbits. The IV administration of lidocaine may be a useful adjunct in anesthesia of rabbits.

Involvement of Protein Kinase B/Akt in Analgesic Effect of Dexmedetomidine on Neuropathic Pain

Involvement of Protein Kinase B/Akt in Analgesic Effect of Dexmedetomidine on Neuropathic Pain

Degree of hypothermia in aortic arch surgery - optimal temperature for cerebral and spinal protection: deep hypothermia remains the gold standard in the absence of randomized data.

Since the pioneering report by Griepp in 1975, the use of deep hypothermia for cerebral and visceral organ protection has ushered in the modern era of safe and effective operation on the aortic arch during circulatory arrest (1). In large part due to advanced circulatory management strategies, the number of proximal aorta and arch replacements have increased each year since 2005, with over 10,000 operations reported to the Society of Thoracic Surgeons National Database in 2009 alone (2). However, despite these advances, neurologic complications remain a sobering limitation of arch repair, with national rates of major neurologic morbidity ranging between 3-5% for elective arch repairs and 9-13% for non-elective repairs (2). In addition, visceral organ injury such as renal failure requiring dialysis occurs in 3-6% of patients (2), highlighting the need for additional investigation into methods for ischemic end-organ protection during circulatory arrest. The concept of using hypothermia to temporarily reduce the oxygen and metabolic requirements of hypoxic tissues is intuitive and supported by decades of laboratory, translational, and clinical science. Nonetheless, the optimal temperature for hypothermic circulatory arrest (HCA) during arch surgery remains unclear and is confounded by a myriad of other clinical variables that are also without consensus, such as location of temperature measurement, cannulation site, perfusion rates, rapidity of cooling and rewarming, anesthetic and pharmacologic adjuncts, selective cerebral perfusion technique, and use of intraoperative electroencephalographic (EEG) neuromonitoring to guide cooling. As a result, HCA strategies vary considerably, even between respected high-volume centers, and are often dictated as much by dogma and tradition as by evidence. Maximal suppression of the cerebral metabolic rate of oxygen consumption occurs at EEG isoelectricity, or electrocerebral inactivity (ECI) (3,4), with modern aortic surgeons traditionally aiming to achieve this level of metabolic suppression through the use of ‘profound’ or ‘deep’ hypothermia. Although cooling below 18 °C was initially thought necessary to achieve ECI (3,4), more recent studies have shown that ECI can occur anywhere between 10 and 27 °C in human subjects (Figure 1) (5-7). As a result, many experienced centers, including our own, employ neurophysiologic intraoperative monitoring with EEG to precisely detect ECI prior to the initiation of circulatory arrest (6,8-10). Cooling to ECI by EEG ensures maximal suppression of cerebral metabolic activity prior to circulatory arrest, while minimizing perfusion time and hypothermic injury by avoiding excessive cooling (5). Figure 1 Cumulative (A) nasopharyngeal temperature and (B) cooling time required to achieve electrocerebral inactivity (ECI) in a series of 325 adult patients who underwent thoracic aortic surgery at Duke University Medical Center with deep hypothermic circulatory ... However, as early as 1983, concerns over the physiologic consequences of profound temperature reductions led some to advocate lesser degrees of hypothermia with circulatory arrest (11). Initial concerns focused primarily on bleeding complications thought to result from hypothermia-induced coagulopathy, as well as increased systemic inflammatory response from the prolonged perfusion times required for cooling and rewarming (11,12). More recently, concerns over subtle neurocognitive deficits caused by hypothermic neuronal injury have been raised (13-15), despite reports documenting complete neurocognitive preservation following deep HCA (16). In light of these theoretic concerns along with the advent of cerebral protection strategies, an increasing number of centers now employ ‘moderate’ or even ‘mild’ degrees of systemic hypothermia coupled with selective antegrade cerebral perfusion (SACP) (12,17-21). Although the benefits of SACP with HCA appear well established (10), there remains a lack of objective data demonstrating the superiority, or even non-inferiority, of moderate hypothermia with SACP in comparison to deep hypothermia with SACP, particularly pertaining to visceral organ and spinal cord protection (9). In the present article, we provide a brief overview of the history and evidence that shapes the current controversy regarding the optimal temperature for central nervous system and visceral organ protection with HCA employed during aortic arch repair. We conclude that, given the limitations of existing retrospective observational data, a multi-center randomized trial is needed to directly compare deep and moderate HCA and provide high-quality evidence-based guidelines for this critically important component of aortic arch repair.

Magnesium: a versatile drug for anesthesiologists

Magnesium sulfate has been used in preeclampsia patients in order to prevent seizure. It is also used for the treatment of arrhythmia and asthma and as an anesthetic adjunct in patients undergoing surgery for pheochromocytoma. However, its potentiating effects on perioperative analgesia and muscle relaxation have drawn attention recently. These characteristics of magnesium (anesthetic- and analgesic-sparing effect) enable anesthesiologists to reduce the use of anesthetics during surgery and the use of analgesics after surgery. Magnesium sulfate has a high therapeutic index and cost-effectiveness. Considering these diverse characteristics useful for anesthesia, appropriate use of magnesium sulfate would improve surgical outcome and patients' satisfaction.

Dexmedetomidine as anesthetic adjunct for fast tracking and pain control in off-pump coronary artery bypass.

Objective:This study was designed to determine the efficacy of dexmedetomidine (a highly selective alpha-2 agonist) in achieving fast tracking and improved postoperative pain control in off-pump coronary artery bypass (OPCAB) patients.Methods:Thirty patients scheduled for elective OPCAB were prospectively randomized into two groups: Group I (15 patients) started dexmedetomidine at 0.5 ug/kg/hour after the induction of anesthesia; this was reduced to 0.3 ug/kg/hour on admission in the cardiac intensive care unit and continued for 12 hours post extubation. Group II (15 patients) received a similar volume and infusion rate of normal saline. Visual analog scale (VAS) of 10-100 was explained thoroughly to the patients during the preoperative visit. Postoperative pain was managed with morphine. The total dose of morphine was recorded. Extubation time and VAS was recorded every two hours for 12 hours post extubation.Results:Extubation time in group I was 72±8 minutes and 186±22 minutes in group II. Mean total use of narcotics in group II was 23.5±20.7 mg compared to 11.4±6.3 mg in group I. VAS median figures were lower at all data points in group I than in group II.Conclusion:Dexmedetomidine showed an effective and safe profile as an anesthetic adjunct in OPCAB, achieving fast tracking of patients and higher quality of pain control with a lower consumption of narcotics.

Dexmedetomidine for Patients Undergoing Diagnostic Cardiac Procedures: A Noninferiority Study

When anesthetizing children with congenital heart disease for diagnostic cardiac catheterization, anesthesiologists and cardiologists seek to use anesthetic regimens that yield minimal hemodynamic changes and allow for spontaneous ventilations. Recently, dexmedetomidine has been used as an anesthesia adjunct because of its sedative and analgesic properties and minimal ventilatory depressive effects. We tested the hypothesis that the combination of sevoflurane and dexmedetomidine is non-inferior to sevoflurane alone as it refers to hemodynamic measurements during diagnostic cardiac catheterization in children with a transplanted heart, one ventricle (Fontan procedure), or normal cardiac physiology. Patients were anesthetized with inhalation of sevoflurane in nitrous oxide/oxygen and, after baseline hemodynamic measurements, successive boluses of dexmedetomidine followed by continuous infusion were administered. In this study, non-inferiority was shown when differences at steady-state (dexmedetomidine + sevoflurane) compared to baseline (sevoflurane alone) and its associated 95% confidence interval fell completely within the range of plus or minus 20%. Forty-one (26 normal physiology, 9 cardiac transplantation, and 6 Fontan) patients were enrolled. Non-inferiority of sevoflurane + dexmedetomidine compared with sevoflurane alone was shown for heart rate, but not for arterial blood pressure in patients with normal and cardiac transplant physiology. In patients with normal cardiac physiology, non-inferiority was demonstrated for bispectral index. Therefore, while the lack of depressive respiratory effects and non-inferiority for heart rate are desirable, the lack of non-inferiority of dexmedetomidine + sevoflurane combination for arterial blood pressure do not justify the routine use of this combination compared with sevoflurane alone for children with congenital heart disease undergoing cardiac catheterization.

Dexmedetomidine in Bariatric Surgery: A Useful Opioid Adjunct? An Evidence-Based Review

Background: According to the Centers for Disease Control, nearly 34% of adults in the United States are obese, and one treatment used is bariatric surgery. However, often these patients require large doses of opioids during the perioperative period, which can result in significant side effects. One agent that can be used as a supplement or in place of opioids is the alpha 2 agonist dexmedetomidine. However, research regarding the use of dexmedetomidine in bariatric surgery is limited. Therefore, the purpose of this evidenced-based review was to examine the effect of dexmedetomidine on anesthetic requirements during bariatric surgery and opioid requirements and recovery in the postoperative period. Methods: An evidenced-based review was completed using MEDLINE with a search of articles published after 2005. The terms obesity and bariatric surgery were linked with dexmedetomidine and scored for research quality. Results: A total of 182 subjects from three randomized controlled trials, one case review, and two case reports were identified as relevant and included in this analysis. It was noted that when dexmedetomidine was used as part of the anesthesia regimen, there was an overall decrease in intraoperative opioid analgesics and inhalational anesthetics, as well as an increased stability in intraoperative hemodynamics. Postoperatively, those patients receiving dexmedetomidine were noted to require less postoperative analgesia and had decreased pain scores with no reported incidences of respiratory depression. Conclusions: Based on this review, it appears that dexmedetomidine is a useful intraoperative anesthetic adjunct in patients undergoing bariatric surgery.

Residual Neuromuscular Blockade in Critical Care

Neuromuscular blockade is a pharmacological adjunct for anesthesia and for surgical interventions. Neuromuscular blockers can facilitate ease of instrumentation and reduce complications associated with intubation. An undesirable sequela of these agents is residual neuromuscular blockade. Residual neuromuscular blockade is linked to aspiration, diminished response to hypoxia, and obstruction of the upper airway that may occur soon after extubation. If an operation is particularly complex or requires a long anesthesia time, residual neuromuscular blockade can contribute to longer stays in the intensive care unit and more hours of mechanical ventilation. Given the risks of this medication class, it is essential to have an understanding of the mechanism of action of, assessment of, and factors affecting blockade and to be able to identify factors that affect pharmacokinetics.

Assessing the Impact of a Regional Anesthesia Workshop on Anesthesiology Residents’ Perceived Comfort in Performing Peripheral Nerve Blocks

Different methods of regional anesthesia education have been described in the literature, but none have proven to be superior. The objective of this study was to evaluate the educational value as perceived by the anesthesia resident of a regional anesthesia workshop. Twenty-eight anesthesia residents participated in a workshop, which reviewed nerve blocks of the upper and lower extremities. Prior to the workshop, each resident completed a survey assessing their confidence in their ability to perform 13 nerve blocks. At the conclusion of the workshop and at 3 months post-workshop, the residents completed similar surveys. Paired sample t-test was used to compare pre- and post-workshop confidence levels. Twenty-eight residents completed the pre-, post-, and 3-month follow-up questionnaires. There was a statistically significant increase in residents' confidence level post-workshop for 11 block s evaluated. This was sustained in 5 blocks at the 3 month follow-up survey. Senior residents had higher baseline confidence scores when compared to junior residents. When all blocks were considered, junior residents demonstrated a statistically signifi cant increase in confidence level in independently performing nerve blocks immediately post workshop and at 3 month follow-up. Senior residents had a statistically significant increase in confidence level immediately post workshop, but not at the 3 month follow-up. 100% of participants found the workshop to be beneficial. Participants with less prior experience showed sustained increase in comfort levels at 3 months post-workshop (p=0.007). Based on self-reported trainee comfort level, the workshop was an effective teaching tool. Future workshops might be most effective when targeted at learners with less baseline regional anesthesia experience. Peripheral nerve block workshops can provide an important adjunct in the regional anesthesia ed ucation of resident anesthesiologists.

Hemodynamic effects of dexmedetomidine in isoflurane-anesthetized cats

ObjectiveTo characterize the hemodynamic effects of dexmedetomidine in isoflurane-anesthetized cats. Study designProspective experimental study. AnimalsSix healthy adult female cats weighing 4.6 ± 0.8 kg. MethodsDexmedetomidine was administered intravenously using target-controlled infusions to maintain nine plasma concentrations between 0 and 20 ng mL−1 in isoflurane-anesthetized cats. The isoflurane concentration was adjusted for each dexmedetomidine concentration to maintain the equivalent of 1.25 times the minimum alveolar concentration, based on a previous study. Heart rate, systemic and pulmonary arterial pressures, central venous pressure, pulmonary artery occlusion pressure, body temperature, and cardiac output were measured at each target plasma dexmedetomidine concentration. Additional variables were calculated. Arterial and mixed-venous blood samples were collected for blood gas, pH, and (on arterial blood only) electrolyte, glucose and lactate analysis. Plasma dexmedetomidine concentration was determined for each target. Pharmacodynamic models were fitted to the data. ResultsHeart rate, arterial pH, arterial bicarbonate concentration, mixed-venous PO2, mixed-venous pH, mixed-venous hemoglobin oxygen saturation, cardiac index, stroke index, and venous admixture decreased following dexmedetomidine administration. Arterial blood pressure, central venous pressure, pulmonary arterial pressure, pulmonary arterial occlusion pressure, packed cell volume, PaO2, PaCO2, arterial hemoglobin concentration, mixed-venous PCO2, mixed-venous hemoglobin concentration, ionized calcium concentration, glucose concentration, rate-pressure product, systemic and pulmonary vascular resistance indices, left ventricular stroke work index, arterial oxygen concentration, and oxygen extraction increased following dexmedetomidine administration. Most variables changed in a dexmedetomidine concentration-dependent manner. Conclusion and clinical relevanceThe use of dexmedetomidine as an anesthetic adjunct is expected to produce greater negative hemodynamic effects than a higher, equipotent concentration of isoflurane alone.

Intravenous regional anesthesia: a review of common local anesthetic options and the use of opioids and muscle relaxants as adjuncts

PurposeTo provide a review of local anesthetic (LA) agents and adjuncts, opioids and muscle relaxants, and their intraoperative effects and postoperative outcomes in intravenous regional anesthesia (IVRA).SourceA search for prospective, double-blind, randomized controlled trials evaluating LA agents, opioids and muscle relaxants as adjuvants for IVRA, was conducted (MEDLINE®, Embase). Intraoperative benefits (onset/recovery of sensory and motor block, intraoperative analgesia, tourniquet pain), postoperative benefits (pain score, analgesic consumption, time to first analgesia), and side effects were recorded. A conclusion for overall benefit was made based on statistical significance and clinical relevance.FindingsThirty-one studies were evaluated, with data collected on 1523 subjects. LA agents evaluated were lidocaine, ropivacaine, and prilocaine. Adjuncts evaluated were opioids ( morphine, fentanyl, meperidine, sufentanil, tramadol) and muscle relaxants (pancuronium, atracurium, mivacurium, cisatacurium). There was good evidence that ropivacaine provided effective IVRA and improved postoperative analgesia. Lidocaine and prilocaine were effective LA agents, however they lacked postoperative benefits. Morphine, fentanyl, and meperidine as sole adjuncts did not demonstrate clinically significant benefits or result in an increased risk of side effects. Sufentanil data was limited, but appeared to provide faster onset of sensory block. Tramadol provided faster onset of sensory block and tourniquet tolerance, however postoperative benefits were not consistent and the risk of minor side effects increased. Muscle relaxants improved the quality of motor block, but at the expense of delayed motor recovery. The combination of fentanyl and muscle relaxants can achieve an equivalent quality of IVRA with 50% reduction in LA dose, but at the expense of a potentially slower onset of sensory block.ConclusionRopivacaine is effective for IVRA and improves postoperative analgesia. Muscle relaxants enhance the motor block and when combined with fentanyl allow for an equivalent quality of IVRA with 50% reduction in LA dose.

Awareness in children: a secondary analysis of five cohort studies

Five recent cohort studies have shown a frequency of awareness in paediatric anaesthesia of between 0.2% and 1.2%, but they were not individually large enough to identify risk factors. This study pooled raw data from these five studies to identify factors associated with awareness in children. The outcome of awareness was taken as the cases judged to be most likely awareness cases in each study. Logistic regression was used to identify awareness-associated factors. A combined sample of 4486 anaesthetics revealed 33 cases of awareness. Unadjusted analysis demonstrated weak evidence that nitrous oxide used as an anaesthetic maintenance adjunct was associated with awareness (OR 2.04 (95% CI 0.97-4.33), p=0.06), and some evidence that use of a tracheal tube was associated with awareness (OR 2.78 (95% CI 1.11-6.94), p=0.03). Multivariable regression analysis revealed that nitrous oxide maintenance and use of a tracheal tube were independently associated with awareness (nitrous oxide, OR 2.4 (95% CI 1.08-5.32), p=0.03; tracheal tube, OR 3.0 (95% CI 1.20-7.56), p=0.02).

General Anesthesia in the Elderly Patient with Cardiovascular Disease

Anesthesiologists are faced with increasing numbers of elderly patients in their practice due to ageing population, especially in Western societies. Ageing is associated with physiologic changes that decrease the ability to respond to surgical and disease-related stress. Moreover, elderly patients suffer from significant co-morbidities including diseases of cardiovascular and pulmonary system. Both of these factors add to the challenges of anesthetic care in this patient population. Lastly, chronological age alone is an inadequate predictor of the response expected in an individual patient (the paradox of the “old” 65 year-old vs. a “young” 85 year -old patient). In our review we discuss the physiologic changes of ageing and write about most frequent or significant co-morbidities of old age and their effects on the anesthetic choice. We further review sedative and anesthetic agents, pain medications and other adjunct medications, which may result in important, potentially detrimental consequences for the elderly patient.