Psychological preparation and postoperative outcomes for adults undergoing surgery under general anaesthesia

Sources of support Internal sources Manchester Centre for Health Psychology, University of Manchester, UK. An award of £2000 was received to support research assistant costs. External sources British Academy, UK. We received a small research grant of £7480 to support research assistant costs.

Clinical manifestations due to pharmacological interactions in pediatric ophthalmic surgery. Topical drugs and general anaesthesia

Introduction. The authors consider the type and the incidence of the adverse effects due to the interaction between ophthalmic drugs and general anaesthesia in pediatric ophthalmic surgery. Patients and Methods. The experience included 176 general anaesthesia in 100 children aged between 9,2 months and 11,4 years (mean age 4,9 years). Results. In the 100 patients we reported: 4 cases (2.7% general anaesthesias) of sinus tachycardia with heart rhythm varying between 170 and 180 beats per minute (3.6%); 5 cases of sinus bradycardia, varying between 60 and 70 beats per minute (3.3%); 3 cases of bronchospasm (2%); 2 cases of psychomotor agitation/disturbances in pre-convulsive state after anaesthesia (1.3%); 3 cases of arterial hypotension (60-70 mmHg) (2%); 7 cases of skin rush around neck and chest (4.6%); 1 case of prolonged apnoea (0.6%). Conclusions. The clinical manifestations, principally on the cardio-circulatory and nervous system are subjected to critical revision, to foresee the pharmacological interferences and therefore to prepare the necessary measure of medical treatment.

A randomised controlled trial comparing the effect of adjuvant intrathecal 2 mg midazolam to 20 micrograms fentanyl on postoperative pain for patients undergoing lower limb orthopaedic surgery under spinal anaesthesia.

Background: Intrathecal adjuvants are added to local anaesthetics to improve the quality of neuraxial blockade and prolong the duration of analgesia during spinal anaesthesia. Used intrathecally, fentanyl improves the quality of spinal blockade as compared to plain bupivacaine and confers a short duration of post-operative analgesia. Intrathecal midazolam as an adjuvant has been used and shown to improve the quality of spinal anaesthesia and prolong the duration of post-operative analgesia. No studies have been done comparing intrathecal fentanyl with bupivacaine and intrathecal 2 mg midazolam with bupivacaine. Objective: To compare the effect of intrathecal 2 mg midazolam to intrathecal 20 micrograms fentanyl when added to 2.6 ml of 0.5% hyperbaric bupivacaine, on post-operative pain, in patients undergoing lower limb orthopaedic surgery under spinal anaesthesia. Methods: A total of 40 patients undergoing lower limb orthopaedic surgery under spinal anaesthesia were randomized to two groups. Group 1: 2.6mls 0.5% hyperbaric bupivacaine with 0.4mls (20micrograms) fentanyl Group 2: 2.6mls of 0.5% hyperbaric bupivacaine with 0.4mls (2mg) midazolam Results: The duration of effective analgesia was longer in the midazolam group (384.05 minutes) as compared to the fentanyl group (342.6 minutes). There was no significant difference (P 0.4047). The time to onset was significantly longer in midazolam group 17.1 minutes as compared to the fentanyl group 13.2 minutes (P 0.023). The visual analogue score at rescue was significantly lower in the midazolam group (5.55) as compared to the fentanyl group 6.35 (P - 0.043). Conclusion: On the basis of the results of this study, there was no significant difference in the duration of effective analgesia between adjuvant intrathecal 2 mg midazolam as compared to intrathecal 20 micrograms fentanyl for patients undergoing lower limb orthopaedic surgery.

A randomised controlled trial comparing weight adjusted dose versus fixed dose prophylactic phenylephrine infusion on maintaining systolic blood pressure during caesarean section under spinal anaesthesia.

Background: Spinal anaesthesia is the standard of care for elective caesarean delivery. It has advantages over general anaesthesia. However the sympathetic blockade induced by spinal anaesthesia results in an 80 percent incidence of hypotension without prophylactic management. Current evidence supports co-loading with intravenous fluids in conjunction with the use of vasopressors as the most effective way to prevent and treat the hypotension. Phenylephrine is the accepted vasopressor of choice in the parturient. A prophylactic phenylephrine infusion combined with a fluid co-load is proven to be an effective and safe method of maintaining maternal hemodynamic stability. While most published studies have assessed the effectiveness of a prophylactic phenylephrine fixed dose infusion, few studies have assessed the effect of a prophylactic phenylephrine weight adjusted dose infusion on maintaining maternal hemodynamic stability following spinal anesthesia for a cesarean delivery. Objective: To compare the incidence of hypotension between women undergoing elective caesarean section under spinal anaesthesia, receiving prophylactic phenylephrine infusion at a fixed dose of 37.5 micrograms per minute versus a weight adjusted dose of 0.5 micrograms per kilogram per minute. Methods: One hundred and eight patients scheduled for non-urgent caesarean section under spinal anaesthesia were randomized into 2 groups; control group and intervention group using a computer generated table of numbers. Control group; Received prophylactic phenylephrine fixed dose infusion at 37.5 micrograms per minute. Intervention group; Received prophylactic phenylephrine weight adjusted dose infusion at 0.5 micrograms per kilogram per minute Results: The two groups had similar baseline characteristics in terms of ; Age, sex, weight and height. There was a 35.2% incidence of hypotension in the fixed dose group and an 18.6% incidence of hypotension in the weight adjusted dose group. This difference was found to be of borderline statistical significance p-value 0.05, and the difference in the incidence rates between the two groups was found to be statistically significant p= 0.03. The difference in the incidence of reactive hypertension and bradycardia between the two groups was not statistically significant: p-value of 0.19 for reactive hypertension and p-value of 0.42 for the incidence of bradycardia. There was also no statistically significant difference in the use of phenylephrine boluses, use of atropine, intravenous fluid used and the number of times the infusion was stopped. Conclusion: Among this population, the incidence of hypotension was significantly less in the weight adjusted dose group than in the fixed dose group. There was no difference in the number of physician interventions required to keep the blood pressure within 20% of baseline, and no difference in the proportion of reactive hypertension or bradycardia between the two groups. Administering prophylactic phenylephrine infusion at a weight adjusted dose of 0.5 micrograms per kilogram per minute results in a lower incidence of hypotension compared to its administration at a fixed dose of 37.5 micrograms per minute.

Orthopaedic anaesthesia for upper extremity procedures in a Nigerian hospital

Background General anaesthesia and regional anaesthesia have been used successfully for upper extremity orthopaedic procedures. Despite the advantages of regional anaesthesia, there is low utilisation in Nigeria. In this study, we assessed the types of anaesthesia employed for upper extremity surgeries in our centre. Methods After obtaining approval from the institutional ethics committee, all the patients who had upper extremity surgeries from 1 January 2011 to 31 December 2012 were included in this review. Both prospective and retrospective data were gathered. The choice of anaesthesia was at the discretion of the attending anaesthetist. Results A total of 226 patients with a male-to-female ratio of 1.6:1 and median age of 35.0 (range 2 – 89) years, had orthopaedic upper extremity procedures during the study period. Sixty-three cases (27.9%) had general anaesthesia, 5 (2.2%) combined regional and general anaesthesia while 158 (69.9%) had regional blocks. The regional blocks comprised 145 (89%) different approaches to the brachial plexus and 18 (11%) local anaesthetic infiltrations. The arm was the site mostly operated upon; while supraclavicular and axillary brachial plexus blocks were performed in equal amounts. In 14 (6.2%) patients, brachial plexus blocks were performed with spinal anaesthesia because of concomitant iliac crest bone grafts. While the duration of surgery did not differ significantly, regional anaesthesia provided a significantly longer duration of anaesthesia than general anaesthesia (251 ± 70.8 min versus 141.3 ± 65.5 min; p = 0.0000001). Conclusion There is a high use of regional anaesthesia for upper extremity orthopaedic surgeries in our centre, which is a positive development in a resource limited setting.

Pharmacokinetic Profile of Liposome-Encapsulated Ropivacaine after Maxillary Infiltration Anaesthesia

The aim of this study was to determine the pharmacokinetic parameters of liposomal ropivacaine after dental anesthesia in 14 healthy volunteers. In this randomized, double-blind and crossover study, the volunteers received maxillary infiltration of liposome-encapsulated 0.5% ropivacaine and, 0.5% ropivacaine with 1:200,000 epinephrine in two different sessions. Blood samples were collected before and after (from 15 to 1440 min) the administration of either ropivacaine formulation. HPLC with UV detection was used to quantify plasma ropivacaine concentrations. The pharmacokinetic parameters AUC(0-24) (area under the plasma concentration x time curve from baseline to 24 h), AUC(0-infinity) (area under the plasma concentration-time curve from baseline to infinity), C-max (maximum drug concentration), CL (renal clearance), T-max (maximum drug concentration time), t(1/2) (elimination half-life) and Vd (volume of distribution) were analyzed using the Wilcoxon signed-rank test. No differences (p > 0.05) were observed between both formulations for any of the pharmacokinetic parameters evaluated and plasma ropivacaine concentrations, considering each period of time. Both formulations showed similar pharmacokinetic profiles, indicating that the liposomal formulation could be a safer option for use of this local anesthetic, due to the absence of a vasoconstrictor.

Anaesthesia and analgesia in laboratory adult zebrafish: A question of refinement

Anaesthesia is used daily in fish experimental procedures; however, the use of an inadequate anaesthetic protocol can compromise not only the animal’s welfare but also the reliability of results. The use of zebrafish (Danio rerio) in biomedical research has increased in the last decades, highlighting the importance of appropriate anaesthetic regimens for this species. This article reviews the main anaesthetic agents and protocols used in laboratory adult zebrafish, and some of the analgesic methods to be used in this species that still need more research. In addition, a systematized observation of signs is proposed to evaluate adult zebrafish welfare to reduce pain and distress.

Refining animal models in fracture research: Seeking consensus in optimising both animal welfare and scientific validity for appropriate biomedical use

Background In an attempt to establish some consensus on the proper use and design of experimental animal models in musculoskeletal research, AOVET (the veterinary specialty group of the AO Foundation) in concert with the AO Research Institute (ARI), and the European Academy for the Study of Scientific and Technological Advance, convened a group of musculoskeletal researchers, veterinarians, legal experts, and ethicists to discuss, in a frank and open forum, the use of animals in musculoskeletal research. Methods The group narrowed the field to fracture research. The consensus opinion resulting from this workshop can be summarized as follows: Results & Conclusion Anaesthesia and pain management protocols for research animals should follow standard protocols applied in clinical work for the species involved. This will improve morbidity and mortality outcomes. A database should be established to facilitate selection of anaesthesia and pain management protocols for specific experimental surgical procedures and adopted as an International Standard (IS) according to animal species selected. A list of 10 golden rules and requirements for conduction of animal experiments in musculoskeletal research was drawn up comprising 1) Intelligent study designs to receive appropriate answers; 2) Minimal complication rates (5 to max. 10%); 3) Defined end-points for both welfare and scientific outputs analogous to quality assessment (QA) audit of protocols in GLP studies; 4) Sufficient details for materials and methods applied; 5) Potentially confounding variables (genetic background, seasonal, hormonal, size, histological, and biomechanical differences); 6) Post-operative management with emphasis on analgesia and follow-up examinations; 7) Study protocols to satisfy criteria established for a "justified animal study"; 8) Surgical expertise to conduct surgery on animals; 9) Pilot studies as a critical part of model validation and powering of the definitive study design; 10) Criteria for funding agencies to include requirements related to animal experiments as part of the overall scientific proposal review protocols. Such agencies are also encouraged to seriously consider and adopt the recommendations described here when awarding funds for specific projects. Specific new requirements and mandates related both to improving the welfare and scientific rigour of animal-based research models are urgently needed as part of international harmonization of standards.

Oxygen delivery through high-flow nasal cannulae increase end-expiratory lung volume and reduce respiratory rate in post-cardiac surgical patients

Background: High-flow nasal cannulae (HFNC) create positive oropharyngeal airway pressure but it is unclear how their use affects lung volume. Electrical impedance tomography (EIT) allows assessment of changes in lung volume by measuring changes in lung impedance. Primary objectives were to investigate the effects of HFNC on airway pressure (Paw) and end-expiratory lung volume (EELV), and to identify any correlation between the two. Secondary objectives were to investigate the effects of HFNC on respiratory rate (RR), dyspnoea, tidal volume and oxygenation; and the interaction between body mass index (BMI) and EELV. Methods: Twenty patients prescribed HFNC post-cardiac surgery were investigated. Impedance measures, Paw, PaO2/FiO2 ratio, RR and modified Borg scores were recorded first on low flow oxygen (nasal cannula or Hudson face mask) and then on HFNC. Results: A strong and significant correlation existed between Paw and end-expiratory lung impedance (EELI) (r=0.7, p<0.001). Compared with low flow oxygen, HFNC significantly increased EELI by 25.6% (95% CI 24.3, 26.9) and Paw by 3.0 cmH2O (95% CI 2.4, 3.7). RR reduced by 3.4 breaths per minute (95% CI 1.7, 5.2) with HFNC use, tidal impedance variation increased by 10.5% (95% CI 6.1, 18.3) and PaO2/FiO2 ratio improved by 30.6 mmHg (95% CI 17.9, 43.3). HFNC improved subjective dyspnoea scoring (p=0.023). Increases in EELI were significantly influenced by BMI, with larger increases associated with higher BMIs (p<0.001). Conclusions: This study suggests that HFNC improve dyspnoea and oxygenation by increasing both EELV and tidal volume, and are most beneficial in patients with higher BMIs.

Learnability and discriminability of melodic medical equipment alarms

Melodic alarms proposed in the IEC 60601-1-8 standard for medical electrical equipment were tested for learnability and discriminability. Thirty-three non-anaesthetist participants learned the alarms over two sessions of practice, with or without mnemonics suggested in the standard. Fewer than 30% of participants could identify the alarms with 100% accuracy at the end of practice. Confusions persisted between pairs of alarms, especially if mnemonics were used during learning (p = 0.011). Participants responded faster (p < 0.00001) and more accurately (p = 0.002) to medium priority alarms than to high priority alarms, even though they rated the high priority alarms as sounding more urgent (p < 0.00001). Participants with at least 1 year of formal musical training identified the alarms more accurately (p = 0.0002) than musically untrained participants, and found the task easier overall (p < 0.00001). More intensive studies of the IEC 60601-1-8 alarms are needed for their effectiveness to be determined.

Increased sedation requirements in patients receiving extracorporeal membrane oxygenation for respiratory and cardiorespiratory failure

Critically ill patients receiving extracorporeal membrane oxygenation (ECMO) are often noted to have increased sedation requirements. However, data related to sedation in this complex group of patients is limited. The aim of our study was to characterise the sedation requirements in adult patients receiving ECMO for cardiorespiratory failure. A retrospective chart review was performed to collect sedation data for 30 consecutive patients who received venovenous or venoarterial ECMO between April 2009 and March 2011. To test for a difference in doses over time we used a regression model. The dose of midazolam received on ECMO support increased by an average of 18 mg per day (95% confidence interval 8, 29 mg, P=0.001), while the dose of morphine increased by 29 mg per day (95% confidence interval 4, 53 mg, P=0.021) The venovenous group received a daily midazolam dose that was 157 mg higher than the venoarterial group (95% confidence interval 53, 261 mg, P=0.005). We did not observe any significant increase in fentanyl doses over time (95% confidence interval 1269, 4337 µg, P=0.94). There is a significant increase in dose requirement for morphine and midazolam during ECMO. Patients on venovenous ECMO received higher sedative doses as compared to patients on venoarterial ECMO. Future research should focus on mechanisms behind these changes and also identify drugs that are most suitable for sedation during ECMO.