Maintenance Phase Of Anesthesia Research Articles

ADVANTAGES OF USING DEXMEDETOMIDINE AS AN ADJUVANT IN LAPAROSCOPIC BARIATRIC SURGERIES

The global rise in obesity rates has necessitated an increased frequency of bariatric surgeries, posing intricate challenges in anesthesia management. Dexmedetomidine, an α2-adrenergic receptor agonist, has emerged as a potential adjunct to general anesthesia in this context. This study aimed to evaluate the efficacy and safety of dexmedetomidine in 1306 adult patients undergoing elective bariatric surgery between January 2017 and September 2023, comparing outcomes with a placebo group.Dexmedetomidine was administered during both the maintenance phase of anesthesia. Key parameters including intraoperative and postoperative complications, analgesic requirements, hemodynamics, and recovery profiles were meticulously monitored and analyzed. Dexmedetomidine demonstrated sedative and analgesic-sparing effects, coupled with cardiovascular stabilization and preservation of respiratory function. Notably, it significantly reduced the utilization of anesthetic drugs, postoperative opioids, and propofol during the surgical procedure. Furthermore, dexmedetomidine exhibited efficacy in attenuating propofol injection pain, mitigating stress responses during the critical phase of extubation, and diminishing postoperative pain along with associated analgesic requirements. However, a nuanced approach to dosage was imperative, as higher doses correlated with delayed respiratory recovery and an increased incidence of bradycardia.To summarize, dexmedetomidine as an adjuvant to general anesthesia in bariatric surgery presents notable advantages in enhancing recovery profiles, mitigating complications, and improving patient comfort. Optimal dosing strategies are paramount to harnessing its benefits while mitigating potential adverse effects, thereby optimizing perioperative care in this patient population.

A study of the relationship between Bispectral index and age-adjusted minimum alveolar concentration during the maintenance phase of general anesthesia in elective surgery

Abstract Background and Aims: Bispectral index (BIS) and minimum alveolar concentration (MAC) are commonly used to monitor the depth of anesthesia. The objective was to study the correlation between BIS and age-adjusted minimum alveolar concentration (aaMAC) during the maintenance phase of anesthesia. The influence of variables affecting BIS and or aaMAC was studied to determine an equation between BIS and aaMAC. Material and Methods: This prospective observational study was carried out after institutional ethical approval in adult patients 18–60 years of either sex, ASA I and II posted for elective surgery under general anesthesia. Five minutes after airway management, BIS values and aaMAC equivalents were noted during the maintenance phase of anesthesia. aaMAC and corresponding BIS values were recorded every minute for periods, where the anesthetic agent concentration had remained the same during preceding 5 minutes till the switching off of the anesthetic agent. Age, sex, ASA status, use of nitrous oxide, inhalational agent, dose of midazolam, and opioid used were also recorded. Results: BIS/aaMAC showed an inverse correlation. Increasing age, ASA II status, morphine equivalent >5, and use of nitrous oxide, sevoflurane, or isoflurane were associated with a higher BIS at equivalent aaMAC. Using the exchangeable correlation structure, a generalized estimation equation was obtained as the best predictor. Conclusion: Factors affecting both aaMAC and BIS affect the relationship between the two, and although there are wide variations, BIS and aaMAC can be equated and values of either can be calculated if one is known using a generalized estimates equation.

Effect of Use of Entropy Monitoring on Consumption of Sevoflurane Inhalational Agent in Patients Undergoing Off-Pump Coronary Artery Bypass Graft Surgery: A Randomized, Double Blinded, Controlled Study

Background: Monitoring the depth of Anesthesia using Entropy modality is essential and resourceful as it allows for more accurate hypnotic drug administration and decreased anesthetic drug consumption and shortens the recovery time. This study was performed to evaluate the effect of entropy monitoring on Sevoflurane consumption in patients undergoing Off Pump Coronary Artery Bypass Graft Surgery.
 Methods: A total of 60 patients of ages between 40 – 70 years and of either sex with American Society of Anesthesiologist (ASA) grade 2 and 3, planned for Off Pump Coronary Artery Bypass Graft Surgery were randomly allocated to two groups in this Randomized Controlled Trial. In the control group i.e. Group B, Sevoflurane was titrated according to changes in clinical parameters (Heart Rate (HR) and Blood Pressure (BP) changes within 20% of baseline values) and in the study group i.e. Group A, Sevoflurane was titrated to maintain State Entropy (SE) values between 40-60 accordingly. Response Entropy (RE) and State Entropy (SE) values were continuously recorded in both the groups but were displayed on the monitor only in the study group and were not displayed to the anesthesiologist in the control group. The entropy values, Sevoflurane Consumption and recovery times were compared amongst the two groups. Patients in both the groups were ventilated on Volume Control Mode of ventilator with 100% oxygen @ 2L/min.
 Results: There were no significant results in terms of age, sex, ASA Grade and NYHA Grade amongst the two groups. Sevoflurane consumption and time of recovery were significantly reduced in the study group i.e. Group A than the Control group i.e. Group B (p value <0.001; Sevoflurane consumption: 7.03±0.67 ml/hr vs 12.42±0.68 ml/hr; Recovery Time 6.47±0.65 hr vs 12.05±1.11 hr). Response and State Entropy values were lower in the control group than the study group (p < 0.001) during the maintenance phase of anesthesia. Systolic Blood Pressure values during skin incision, sternotomy and at the time of completion of all grafts were significantly lower in study group as compared to the control group.
 Conclusion: Monitoring the Depth of Anesthesia using Entropy Monitoring leads to significant reduction in Sevoflurane consumption and significant faster recovery rate from surgery.

Feasibility of intelligent drug control in the maintenance phase of general anesthesia based on convolutional neural network

BackgroundThe growth and aging process of the human population has accelerated the increase in surgical procedures. Yet, the demand for increasing operations can be hardly met since the training of anesthesiologists is usually a long-term process. Closed-loop artificial intelligence (AI) model provides the possibility to solve intelligent decision-making for anesthesia auxiliary control and, as such, has allowed breakthroughs in closed-loop control of clinical practices in intensive care units (ICUs). However, applying an open-loop artificial intelligence algorithm to build up personalized medication for anesthesia still needs to be further explored. Currently, anesthesiologists have selected doses of intravenously pumped anesthetic drugs mainly based on the blood pressure and bispectral index (BIS), which can express the depth of anesthesia. Unfortunately, BIS cannot be monitored at some medical centers or operational procedures and only be regulated by blood pressure. As a result, here we aim to inaugurally explore the feasibility of a basic intelligent control system applied to drug delivery in the maintenance phase of general anesthesia, based on a convolutional neural network model with open-loop design, according to AI learning of existing anesthesia protocols. MethodsA convolutional neural network, combined with both sliding window sampling method and residual learning module, was utilized to establish an "AI anesthesiologist" model for intraoperative dosing of personalized anesthetic drugs (propofol and remifentanil). The fitting degree and difference in pumping dose decision, between the AI anesthesiologist and the clinical anesthesiologist, for these personalized anesthetic drugs were examined during the maintenance phase of anesthesia. ResultsThe medication level established by the “AI anesthesiologist” was comparable to that obtained by the clinical anesthesiologist during the maintenance phase of anesthesia. ConclusionThe application of an open-loop decision-making plan by convolutional neural network showed that intelligent anesthesia control is consistent with the actual anesthesia control, thus providing possibility for further evolution and optimization of auxiliary intelligent control of depth of anesthesia.

Supralabial Site: An Alternative Site for Bispectral Index Monitoring: A Cross-sectional Study

Abstract Background Bi-spectral index (BIS) has been traditionally used to monitor the depth of anesthesia, with the forehead being the usual site for electrode placement. When the manufacturer-recommended site is itself an operative field or the placement interferes with the surgery, the search for an alternative position of electrode placement is warranted. In our endeavor to do so, we conducted this study to compare BIS scores derived from frontal and supralabial electrode placement. Methods A cross-sectional study was conducted on a group of 50 patients using two BIS Quatro sensors attached to the frontal and supralabial regions of each patient and connected to two different sets of monitors. BIS values, electromyography (EMG) values, and signal quality index (SQI) were noted from both sites every 15 min during the maintenance phase of anesthesia. Collected data were analyzed using the Bland–Altman analysis. Results Data analysis of BIS values showed negative bias at most time points with a minimum negative bias of 0.2 with a limit of agreement of −3.67/3.27 and a maximum negative bias of 1.14 with a limit of agreement of −7.61/5.33. The overall 95% limit of agreement for pooled BIS data ranged from −6.63 to 6.1. Conclusion BIS sensor placement at the supralabial site can be used as an alternative to the frontal placement in scenarios where the frontal position is the surgical site or is inaccessible during the maintenance of general anesthesia as in neurosurgery with particular emphasis on skin preparation and proper positioning of BIS electrodes to improve the signal quality.

Adpative Neuro-Fuzzy Inference System Estimation Propofol dose in the induction phase during anesthesia; case study

In this study, the anesthetic drug dose estimation due to the physiological patients' parameters is considered. The most critical anesthetic drug, propofol, is considered in this modeling. Among the intravenous anesthetic drugs, propofol is one of the most widely used during surgery in the induction and maintenance phase of anesthesia. The effect of propofol as an intravenous anesthetic agent is as well as sedate in/outside the operation theatres. In this work, the adaptive neuro-fuzzy inference system estimation model is applied to calculate the drug dose to administrate anesthesia safety. The model estimates the propofol dose during the induction phase based on the physiological parameters (age, weight, height, gender), blood pressure, heart rate, and the depth of anesthesia of real patients. The sensitivity analysis was applied to evaluate the validity of the estimation model, so the appropriate agreement is obtained. In the end, the proposed estimation model's performance is compared to the classical model and the actual data obtained from patients undergoing surgery. The results show that the ANFIS estimation model by 0.999 accuracies reduces the total amount of propofol dose. The proposed model not only controls the patient's depth of anesthesia accurately but also obtained outcomes in practice successfully.

Mortality and morbidity in equine anaesthesia

SummaryEquine peri‐anaesthetic mortality and morbidity are of interest to anaesthetists, practitioners, horse owners and insurance companies. The largest prospective study, ‘The Confidential Enquiry into Perioperative Equine Fatalities’ (CEPEF) was conducted more than 20 years ago. It included over 40,000 horses from multiple centres and reported mortality to be 1.9% that decreased to 0.9% when only elective cases were considered. This is in stark contrast to mortality rates in small animal (dogs: 0.17%, cats: 0.24%) and human anaesthesia (0.04–7/10,000). In spite of developments in understanding the pathophysiology of equine anaesthesia mortality has not decreased in the intervening years. The main contributors to peri‐anaesthetic equine mortality are cardiac arrest, fractures and myopathy or neuropathy. Spinal cord myelopathy and cerebral necrosis are less common. Malignant hyperthermia and hyperkalaemic periodic paralysis are diseases associated with genetic mutations that can be triggered during general anaesthesia and may be fatal if not recognised and treated immediately. Morbidities are reported less frequently, presumably because often they do not cause permanent harm and may resolve within a short period of time. Complications in equine anaesthesia are numerous and include injuries at induction and recovery, damage to the airway associated with orotracheal or nasotracheal intubation, post‐anaesthetic myopathy or neuropathy, regurgitation and aspiration of stomach contents, ocular injuries and complications associated with intravascular cannulation. Hypotension, hypoventilation, hypoxaemia, hypothermia and dysrhythmias may occur both during the maintenance phase of anaesthesia but also in recovery. Airway obstruction during recovery has repeatedly been reported over the years as causing pulmonary oedema, which is often fatal if the airway is not restored extremely quickly. This review summarises the literature on the risk of mortality and morbidity. Information has been gathered from single case reports as well as larger research studies.

Observational study of anaesthesia workflow to evaluate physical workspace design and layout

BackgroundThe safety and efficiency of anaesthesia care depend on the design of the physical workspace. However, little is known about the influence that workspace design has on the ability to perform complex operating theatre (OT) work. The aim of this study was to observe the relationship between task switching and physical layout, and then use the data collected to design and assess different anaesthesia workspace layouts. MethodsIn this observational study, six videos of anaesthesia providers were analysed from a single centre in the United States. A task analysis of workflow during the maintenance phase of anaesthesia was performed by categorising tasks. The data supported evaluations of alternative workspace designs. ResultsAn anaesthesia provider's time was occupied primarily by three tasks: patient (mean: 30.0% of total maintenance duration), electronic medical record (26.6%), and visual display tasks (18.6%). The mean time between task switches was 6.39 s. With the current workspace layout, the anaesthesia provider was centred toward the patient for approximately half of the maintenance duration. Evaluating the alternative layout designs showed how equipment arrangements could improve task switching and increase the provider's focus towards the patient and visual displays. ConclusionsOur study showed that current operating theatre layouts do not fit work demands. We report a simple method that facilitates a quick layout design assessment and showed that the anaesthesia workspace can be improved to better suit workflow and patient care. Overall, this arrangement could reduce anaesthesia workload while improving task flow efficiency and potentially the safety of care.

USNS COMFORT (T-AH 20) Surgical Services Response to the COVID-19 Pandemic in New York City.

USNS COMFORT (T-AH 20) Surgical Services Response to the COVID-19 Pandemic in New York City.

Perioperative anaphylaxis and investigations: a local study in Hong Kong

Data on local intraoperative anaphylaxis in Hong Kong is scarce, with few reviews available. We aimed to study the characteristics, presentations and workup results of cases referred to a local allergy clinic. A retrospective review was performed of patient referrals and workup results for suspected intraoperative anaphylaxis at Queen Mary Hospital drug allergy clinic in 2012-2016. Tryptase was checked in only 81.7% (49/60) of the cases, most of which showed elevation (71.4%, 35/49). Among the 59 patients who received a workup, 47 (79.7%) showed positive findings, with a particularly high yield in the tryptase-positive subgroup (88.6%, 31/35). Among the 54 patients who consented to skin tests (the most sensitive investigation), 43 (79.6%) cases were positive. Overall, neuromuscular blockers were the commonest cause (25.0%, 15/60) of intraoperative anaphylaxis, while antibiotics ranked second (23.3%, 14/60). The timing of reactions was an important indication of potential allergens. For example, the majority of the neuromuscular blocker allergies occurred during the induction phase, while all gelofusine allergic events were in the maintenance phase of anaesthesia. 13 (21.7%) out of 60 cases received subsequent general anaesthesia procedures, with no recurrence of allergic reactions. Proper workup after an intraoperative anaphylactic event has a fairly good chance of identifying the causative allergen. These results are useful for patient management and the planning of subsequent anaesthetic procedures.

Predicting cost of inhalational anesthesia at low fresh gas flows: impact of a new generation carbon dioxide absorbent.

It is well known that low fresh gas flows result in lower cost of inhalational agents. A new generation of carbon dioxide absorbents allows low flow anesthesia with all anesthetics but these new compounds are more expensive. This study examines the cost of inhalational anesthesia at different fresh gas flows combined with the cost of absorbent. The cost of sevoflurane and desflurane is lower at low fresh gas flows. Paradoxically the cost of isoflurane is cheaper at 2 L/min than at lower fresh gas flows due to increased cost of carbon dioxide absorbent. Therefore low fresh gas flows should be used when feasible with sevoflurane and desflurane, but higher fresh gas flows up to 2 L/min may be more economical with isoflurane during maintenance phase of anesthesia.

Intravenous Magnesium Sulfate for Multimodal Analgesia

Purpose Statement Magnesium Sulfate has been used as a multimodal approach for analgesia as it may reduce opioid consumption in the first 24 hours after surgery and decrease post-operative pain scores. Introduction The use of intraoperative opioids for analgesia is associated with postoperative side effects such as respiratory depression, ileus, nausea, and vomiting. The side effects from opioids can prolong hospital stay and cause patient dissatisfaction. Magnesium acts as a N-methyl-D-aspartate (NMDA) receptor antagonist resulting in an analgesic effect, which can be used as an alternative or adjunct to opioids for pain control. Literature Review Magnesium sulfate may be beneficial for multimodal pain management as it reduces opioid requirements and postoperative pain. Targeting various receptors in the pain pathway can optimize analgesia and reduce side effects. Magnesium antagonizes the NMDA receptor and blocks calcium channels to modulate pain and inflammatory responses. Perioperative magnesium administration should be considered as a strategy to reduce postoperative pain in patients undergoing surgical procedures. Description of the Case A 67-year-old female presented for a bilateral breast revision, bilateral blepharoplasty of upper lids, neck rhytidectomy, and fat graft injection surgery. The patient had a history of postoperative nausea and vomiting. During the maintenance phase of anesthesia, fentanyl 50 mcg was given as needed for signs of pain, rocuronium was re-dosed to maintain paralysis, and ephedrine and phenylephrine were administered to maintain blood pressure. Intravenous magnesium sulfate 2 g was administered as a multimodal approach to analgesia to decrease post-operative opioid consumption and to prevent post-operative nausea and vomiting. The following day the patient tolerated a regular diet, pain was well controlled, and was hemodynamically stable. The patient was discharged home without complications. Discussion and Conclusion Magnesium sulfate may be beneficial for multimodal pain management as it reduces opioid requirements and postoperative pain. Magnesium antagonizes the NMDA receptor and blocks calcium channels to modulate pain and inflammatory responses. It is unclear which mode of magnesium administration provides an advantage to the analgesic effects. The differences in age and gender-related responses to magnesium for analgesia is undetermined. Further research is necessary to examine the use of intravenous magnesium sulfate for postoperative pain in different patient populations, safe and effective dosing ranges, and the effects of analgesia in various surgeries. Intravenous magnesium sulfate should be considered in multimodal analgesic treatment as an adjunct for postoperative analgesia.

Modulation of frontal EEG alpha oscillations during maintenance and emergence phases of general anaesthesia to improve early neurocognitive recovery in older patients: protocol for a randomised controlled trial

BackgroundPostoperative delirium may manifest in the immediate post-anaesthesia care period. Such episodes appear to be predictive of further episodes of inpatient delirium and associated adverse outcomes. Frontal electroencephalogram (EEG) findings of suppression patterns and low proprietary index values have been associated with postoperative delirium and poor outcomes. However, the efficacy of titrating anaesthesia to proprietary index targets for preventing delirium remains contentious. We aim to assess the efficacy of two strategies which we hypothesise could prevent post-anaesthesia care unit (PACU) delirium by maximising the alpha oscillation observed in frontal EEG channels during the maintenance and emergence phases of anaesthesia.MethodsThis is a 2 × 2 factorial, double-blind, stratified, randomised control trial of 600 patients. Eligible patients are those aged 60 years or over who are undergoing non-cardiac, non-intracranial, volatile-based anaesthesia of expected duration of more than 2 h. Patients will be stratified by pre-operative cognitive status, surgery type and site. For the maintenance phase of anaesthesia, patients will be randomised (1:1) to an alpha power-maximisation anaesthesia titration strategy versus standard care avoiding suppression patterns in the EEG. For the emergence phase of anaesthesia, patients will be randomised (1:1) to early cessation of volatile anaesthesia and emergence from an intravenous infusion of propofol versus standard emergence from volatile anaesthesia only. The primary study outcomes are the power of the frontal alpha oscillation during the maintenance and emergence phases of anaesthesia. Our main clinical outcome of interest is PACU delirium.DiscussionThis is a largely exploratory study; the extent to which EEG signatures can be modified by titration of pharmacological agents is not known. The underlying concept is maximisation of anaesthetic efficacy by individualised drug titration to a clearly defined EEG feature. The interventions are already clinically used strategies in anaesthetic practice, but have not been formally evaluated. The addition of propofol during the emergence phase of volatile-based general anaesthesia is known to reduce emergence delirium in children; however, the efficacy of this strategy in older patients is not known.Trial registrationAustralian and New Zealand Clinical Trial Registry, ID: 12617001354370. Registered on 27/09/2017.

Adaptive smith predictor controller for total intravenous anesthesia automation.

Anesthetic agent propofol needs to be administered at an appropriate rate to prevent hypotension and postoperative adverse reactions. To comprehend more suitable anesthetic drug rate during surgery is a crucial aspect. The main objective of this proposal is to design robust automated control system that work efficiently in most of the patients with smooth BIS and minimum variations of propofol during surgery to avoid adverse post reactions and instability of anesthetic parameters. And also, to design advanced computer control system that improves the health of patient with short recovery time and less clinical expenditures. Unlike existing research work, this system administrates propofol as a hypnotic drug to regulate BIS, with fast bolus infusion in induction phase and slow continuous infusion in maintenance phase of anesthesia. The novelty of the paper lies in possibility to simplifythe drug sensitivity-based adaption with infusion delay approach to achieve closed-loop control of hypnosis during surgery. Proposed work uses a brain concentration as a feedback signal in place of the BIS signal. Regression model based estimated sensitivity parameters are used for adaption to avoid BIS signal based frequent adaption procedure and large offset error. Adaptive smith predictor with lead-lag filter approach is applied on 22 different patients' model identified by actual clinical data. The actual BIS and propofol infusion signals recorded during clinical trials were used to estimate patient's sensitivity parameters EC 50 and λ. Simulation results indicate that patient's drug sensitivity parameters based adaptive strategy facilitates optimal controller performance in most of the patients. Results are obtained with proposed scheme having less settling time, BIS oscillations and small offset error leads to adequate depth of anesthesia. A comparison with manual control mode and previously reported system shows that proposed system achieves reduction in the total variations of the propofol dose. Proposed adaptive scheme provides better performance with less oscillation in spite of computation delay, surgical stimulations and patient variability. Proposed scheme also provides improvement in robustness and may be suitable for clinical practices.

Investigating Intraoperative and Intraprofessional Handoffs in Anesthesia

Handoffs occur frequently in healthcare systems, and miscommunications and critical omissions within handoffs have been linked to serious medical errors. Handoff quality is a priority of patient safety initiatives across several international organizations. The majority of previous research in handoffs have focused on postoperative handoffs; yet, there is a need to specifically investigate intraoperative handoffs, especially within individual professions or subspecialties. Each subspecialty within a surgical team may approach handoffs differently. The anesthesia team is especially unique as they take a team-based approach to patient care where multiple anesthesia providers may be involved in one surgical case. We describe an observational study of intraoperative and intraprofessional handoffs in anesthesia. Temporary and permanent handoffs were investigated as well as the contextual elements that influenced handoff procedures. In a sample of 35 video recorded surgeries, a total of 16 handoffs were identified for the maintenance phase of surgery. These handoffs ranged between 33 seconds and 7.42 minutes in duration. Our study revealed variability in intraoperative handoffs during the maintenance phase of anesthesia and emphasizes that intraoperative and intraprofessional handoffs warrant more in-depth examination in order to develop effective strategies or tools for high quality handoffs in anesthesia.

Bispectral-Index-measured sevoflurane requirement might be decreased in individuals with major depressive disorder.

GABA (γ-aminobutyric acid) is the primary inhibitory neurotransmitter in the CNS and well-known target for general anesthetics. In addition, the dysregulation of GABA could be involved in the etiology of major depressive disorder (MDD). In this study, we aimed to determine whether MDD has any effect on anesthetic requirement measured by Bispectral Index (BIS). This study was designed as a prospective, observational study, registered ANZCTR (ACTRN 12616001295437), with institutional review board approval and written informed consent. Inpatients who were planned to undergo laparoscopic cholecystectomy as an elective surgery, were enrolled in this study. Patients were divided into two groups, based on the results of the Beck Depression Inventory (BDI) which was assessed the 21-item self-administered scale measuring various symptoms of depression. If the BDI score was under 10, it was accepted as control group. Patients were consulted to the psychiatrist if the BDI score was 17 or more. Patients who were diagnosed as MDD by the psychiatrist, were classified as MDD group. Anesthesia was standardized, and delivered sevoflurane concentration was adjusted according to BIS value in both groups. Parameters of the study were heart rate, non-invasive arterial blood pressure, arterial oxygen saturation, BIS, end-tidal carbon dioxide, and end-tidal concentration of sevoflurane at 5-minute intervals during the operation. End-tidal concentration of sevoflurane was found to be lower in MDD group during the maintenance phase of anesthesia. Mean end-tidal concentration of sevoflurane were significantly lower in MDD group (1.28±0.15) than control group (1.52±0.22) (P<0.0001). BIS values were lower at 5- and 10-minute intervals in MDD group in comparison with control group. BIS values were similar at other time intervals in both groups during surgery. MDD might result in decreased end-tidal concentration of sevoflurane. Further study is required to identify the relationship between MDD and anesthetics.

Premedication considerations for dogs undergoing general anaesthesia

The selection of appropriate pre-anaesthetic drugs prior to general anaesthesia will provide a smoother induction and maintenance phase of anaesthesia. Catecholamine release will be reduced, subsequently reducing anxiety and problems associated with catecholamine release such as cardiac arrhythmias. Intravenous catheter placement and pre-oxygenation can prove less challenging. Analgesia can be provided pre-emptively, which is especially helpful in dogs with chronic pain, reducing the risks of central sensitisation. An ideal pre-anaesthetic medication provides sedation, has minimal effects on the cardiovascular and respiratory systems, provides analgesia and is reversible. Unfortunately, no single drug has all of these properties, therefore a multi-modal approach is required to fulfil a patient's needs. There are several drugs from different pharmacological groups that are commonly used when premedicating dogs in veterinary practice including: opioids, phenothiazines, alpha-2-adrenoreceptor agonists, benzodiazepines and anaesthetic agents. Understanding the mode of action, dose ranges, contraindications, effects and side effects of these drugs allows selection of the most appropriate premedication drug combination for individual patients. It also allows provision of the safest anaesthetic environment possible for the patient and enables veterinary professionals to be prepared for potential complications. Anaesthetic complications cannot be entirely avoided but their risk can be reduced dramatically by understanding fully the drugs that are being used.

The effect of intravenous lidocaine infusion on bispectral index during major abdominal surgery.

Intraoperative lidocaine infusion has become widely accepted as an adjunct to general anesthesia where its use has been associated with opioid-sparing and enhanced recovery. The aims of this study were to determine whether or not intravenous (IV) lidocaine infusion (a) has an anesthetic sparing effect during major colorectal procedures and (b) if it also affects level of hypnosis as measured by bispectral index (BIS). Twenty-five patients undergoing laparotomy for resection of colorectal tumours were randomized to receive either IV lidocaine (1.5mg kg-1 bolus then 1mg kg-1 per hour) or an equivalent volume of normal saline commenced after intravenous induction of general anesthesia. Anesthesia was maintained with volatile anesthetic agent combined with intermittent IV fentanyl titrated to hemodynamic stability. Minimum alveolar concentration (MAC) of volatile was calculated using an age-adjusted algorithm (corrected MAC). BIS values were recorded throughout; however, treating anesthesiologists were blinded to BIS values and hence they were not used to guide depth of anesthesia. No other regional anesthesia techniques were used. During the maintenance phase of anesthesia, corrected MAC of volatile agent was lower (1.0 versus 1.1, p = 0.003); whereas BIS values were higher (45 versus 39, p < 0.001) in patients who received lidocaine versus placebo. No differences in mean arterial pressure (80 versus 80mmHg, p = 0.796) or total fentanyl dose (538 versus 444 mcg, p = 0.24) were observed between the two groups. Heart rate was slightly higher in patients who received lidocaine versus placebo (67 versus 64bpm, p = 0.001). Lidocaine infusion resulted in mean plasma levels of 1.7 mcg ml-1 (1.3-2.0 mcg ml-1, 95% CI). Our results support an anesthetic sparing effect of lidocaine infusion indicated by lower MAC requirements. Higher BIS values in the lidocaine versus placebo group may indicate that levels of hypnosis were not equivalent. Alternatively, BIS may not be a sensitive indicator of synergistic interactions between local anesthetic and volatile agent. Our results advocate a cautious approach to titration of general anesthesia when combined with lidocaine infusion.

Efficacy and safety of ultra rapid iron polymaltose infusion during general anaesthesia.

To assess the efficacy and safety of ultra rapid (15 minute) infusion of iron polymaltose to iron deficient patients during general anaesthesia, we performed a prospective, interventional non-randomised study on 99 adult patients with iron deficiency with or without anaemia presenting for surgery under general anaesthesia. Over 15 minutes during the maintenance phase of anaesthesia, patients were given iron polymaltose, 500 mg if not anaemic, or 1,000 mg if anaemic. Haemodynamic stability, immediate or delayed iron-related side-effects and efficacy at six weeks were assessed. The incidence of significant hypotension or the requirement for vasopressor was not different before, during or after the iron infusion. There were no serious intraoperative events (allergic reactions or skin staining). Mean (standard deviation, SD) haemoglobin rose from 121 (14) g/l preoperatively to 131 (12) g/l at six weeks (P <0.001). Mean (SD) ferritin rose from 17 (12) μg/l to 110 (83) μg/l by six weeks (P <0.001). At six weeks only four out of 64 contactable patients (6.25%) had a ferritin of <30 μg/l. The incidence of immediate or delayed side-effects was similar to patients undergoing outpatient iron polymaltose infusions and reflective of a post-surgical population. We conclude that up to 1,000 mg of iron polymaltose can be given over 15 minutes without significant haemodynamic compromise to selected patients undergoing general anaesthesia. Iron polymaltose administered in this way appears efficacious in treating iron deficiency.

A survey of the dose of inhalational agents used to maintain anaesthesia in infants.

Various animal studies suggest that currently used anaesthetics are toxic to the developing brain. Many reviews advise that the total anaesthetic drug exposure should be reduced but the dose usually used in clinical practice has not been clearly elucidated. To provide an overview of the dose ranges currently used in clinical practice during the maintenance phase of anaesthesia in infants undergoing anaesthesia for noncardiac surgery and diagnostic procedures. A two-centre mixed prospective (London) and retrospective (Utrecht) observational cohort study. Two independent tertiary paediatric referral centres in March and November 2013; Great Ormond Street Hospital (GOSH), London, United Kingdom and Wilhelmina Children's Hospital, University Medical Center Utrecht (UMCU), The Netherlands. A total of 76 infants were included in the analysis, 38 infants from each hospital. Patients from GOSH were matched by procedure, age and weight with patients from the UMCU. The end-tidal concentrations of the inhalational agents were investigated from anaesthetic charts during the maintenance phase and corrected for the age-specific minimal alveolar concentration (MAC), expressed as a percentage from the MAC (%MAC). Three different types of inhalational anaesthetics were used: sevoflurane, desflurane, isoflurane. The mean %MAC was 0.85. No significant differences in %MAC were found between GOSH and the UMCU (P = 0.329); the mean %MAC in GOSH was 0.87 and in the UMCU was 0.82. There was a significant increase in the %MAC in relation to age (slope = 0.036 MAC month, P < 0.001). Of all patients, 75% had an end-tidal concentration lower than 1 MAC. There was no significant effect of the use of analgesia on the end-tidal concentration of inhalational anaesthetics (P = 0.366). The concentration of inhalational anaesthetics in %MAC increased with age and was lowest in neonates. Most young infants received inhalational anaesthetics at a concentration below 1 MAC, which accords with current guidance to minimise anaesthetic drug exposure but may have unintended consequences.