Adequate Depth Of Anesthesia Research Articles

Performance of TCI Propofol Using the Schnider Model for Cardiac Surgery on Cardiopulmonary Bypass–A Pilot Study

This pilot study aimed to evaluate the performance of target-controlled infusion (TCI) of propofol using the Schnider pharmacokinetic model in patients undergoing cardiac surgery requiring cardiopulmonary bypass. This was a prospective pharmacokinetic study. A tertiary care hospital. This study is comprised of 10 patients, aged between 46 and 81, who underwent elective cardiac surgery requiring the use of cardiopulmonary bypass. Anesthetic technique was standardized. Hypnosis was maintained using TCI of propofol, titrated to achieve a bispectral index of 30 to 60. Calculated plasma propofol concentrations were recorded at 5 time points in total, before, during, and after cardiopulmonary bypass. Blood propofol concentration was measured at each of these time points. The prediction errors and absolute prediction errors were calculated for each sample. From these, the median prediction error (MDPE) and its absolute value (MDAPE) were derived. Agreement between predicted and measured propofol concentrations was assessed using a Bland-Altman plot. Mean prediction errors were also compared pre-, on, and post-bypass using the generalized linear latent and mixed model. The MDPE and MDAPE were both found to be 45%, indicating significant bias toward under-prediction in the Schnider pharmacokinetic model. This bias was increased at an average propofol concentration of 4.5 μg/mL and above. A significant decrease in mean prediction error was noted while on bypass (45.6%, 95% confidence intervals 9.2-82.1). The performance of the Schnider pharmacokinetic model for TCI propofol was poor, with a tendency toward under-prediction of blood propofol concentration, especially at higher average concentrations of propofol. While mitigating the risk of awareness, the risk of other adverse effects like hypotension and cardiorespiratory depression is increased. Patients should therefore be adequately monitored, and predicted plasma propofol concentrations taken in context with other patient parameters. A lower target concentration of propofol is probably sufficient to maintain an adequate depth of anesthesia as measured by BIS.

Anesthesia Management During Cardiopulmonary Bypass: Volatile vs. Intravenous Drugs

Anesthetic management during cardiopulmonary bypass (CPB) is challenging in many aspects. Evidence of mortality reduction due to the use of volatile agents during cardiac surgery has led to their increased use in CPB. Partly because of the difficulty to administer volatile agents during CPB, total intravenous anesthesia (TIVA) has become the most popular technique used by cardiac anesthetists throughout this critical period. The aim of this review is to provide an overview of volatile agents’ administration to ensure maintenance of adequate depth of anesthesia during CPB and weighting risks and benefits of this technique compared to TIVA.

Immobilization of Asiatic Black Bears (Ursus thibetanus) with Medetomidine-Zolazepam-Tiletamine in South Korea

The Asiatic black bear ( Ursus thibetanus ; ABB) is a globally endangered species for which a restoration program has been ongoing in South Korea since 2001. However, there is little information on immobilization protocols for ABBs. We evaluated the use of medetomidine-zolazepam-tiletamine for their immobilization. During 2005-13, we anesthetized 60 ABBs (32 males, 28 females; 7 mo to 12 yr old) with medetomidine 0.03-0.045 mg/kg and zolazepam-tiletamine 1.54-2.3 mg/kg; reversal of anesthesia was done with atipamezole 0.15-0.225 mg/kg administered intravenously alone or intravenously and intramuscularly (50:50). Mean (and SD) for physiologic collected for 373 immobilizations of at least 60 min were: time to sedation, 7.8 (5.4) min; anesthesia induction time, 13.7 (8.1) min; complete recovery time, 14.8 (12.4) min; respiratory rate, 14 (7) breaths/min; heart rate, 51 (16) beats/min; rectal temperature, 37.3 (1.3) C; and hemoglobin oxygen saturation, 88% (6%). Few cardiopulmonary side effects occurred during immobilization and adequate depth of anesthesia was maintained for >60 min without need for supplementation. The dosage and drug combination used was effective for immobilization of ABBs with minimal adverse effects on vital signs and can be recommended in most clinical applications.

Effects of thiopentone, propofol and alfaxalone on laryngeal motion during oral laryngoscopy in healthy dogs

ObjectiveTo compare the effects of thiopentone, propofol and alfaxalone on arytenoid cartilage motion and establish the dose rates to achieve a consistent oral laryngoscopy examination. Study designRandomised crossover study. AnimalsSix healthy adult Beagle dogs. MethodsEach dog was randomly administered three induction agents with a 1-week washout period between treatments. Thiopentone (7.5 mg kg−1), propofol (3 mg kg−1) or alfaxalone (1.5 mg kg−1) was administered over 1 minute for induction of anaesthesia. If the dog was deemed inadequately anaesthetised, then supplemental boluses of 1.8, 0.75 and 0.4 mg kg−1 were administered, respectively. Continual examination of the larynx, using a laryngoscope, commenced once an adequate anaesthetic depth was reached until examination end point. The number of arytenoid motions and vital breaths were counted during three time periods and compared over time and among treatments. Data were analysed using Friedman and Mann–Whitney U tests, Spearman rho and a linear mixed model with post hoc pairwise comparison with Tukey correction. ResultsThe median (range) induction and examination times were 2.8 (2.0–3.0), 2.7 (2.0–3.3) and 2.5 (1.7–3.3) minutes (p = 0.727); and 14.1 (8.0–41.8), 5.4 (3.3–14.8) and 8.5 (3.8–31.6) minutes (p = 0.016) for thiopentone, propofol and alfaxalone, respectively. The median dose rates required to achieve an adequate anaesthetic depth were 6.3 (6.0–6.6), 2.4 (2.4–2.4) and 1.2 (1.2–1.2) mg kg−1 minute−1, respectively. There was no significant difference for the total number of arytenoid motions (p = 0.662) or vital breaths (p = 0.789) among induction agents. Conclusion and clinical relevanceThe number of arytenoid motions were similar among the induction agents. However, at the dose rates used in this study, propofol provided adequate conditions for evaluation of the larynx with a shorter examination time which may be advantageous during laryngoscopy in dogs.

Drug anesthesia for children undergoing magnetic resonance imaging: A review

Abstract Children who are scheduled for magnetic resonance imaging (MRI) are usually required to take anesthesia to ensure a satisfactory conclusion of the scan. An adequate depth of anesthesia makes sure that the child is immobilized during the scan and erases the anxiety and auditory stimulation that result from being in the scanner core. Several IV anesthetic regimens are been used in children to prevent movements during scans, they including ketamine, propofol (with and without remifentanil), dexmedetomidine amongst others. Inhaled anesthetics for MRI scans have also been made possible by the use of MRI-compatible anesthetic workstations. In this review we focus on drug anesthesia for children undergoing magnetic resonance imaging (MRI). We first provide a brief commentary on the administration of anesthesia in MRI, next we discuss the prevalent anesthetic agents, then a short examination of the risks and adverse effects.

Anesthetic Considerations in Microlaryngoscopy and Direct Laryngoscopy

ABSTRACTPatients for microlaryngoscopy (ML Scopy) and direct laryngoscopy (DL Scopy) may present to the anesthesiologist from all ages, including pediatric, adult, and geriatric age groups. Proper preoperative evaluation, adequate intraoperative care, monitoring, and postoperative monitoring will provide successful outcome in these patients. These procedures are daycare procedures. The aim of anesthesiologist while dealing with such patients is maintaining adequate depth of anesthesia, maintaining adequate ventilation to the patients while giving enough time to the surgeon to diagnose and evaluate the definitive cause of airway disease. Anesthesiologists need to share the airway or maintain the ventilation in such a way as to give the surgeon proper and good visualization of the patient's airway. Use of shortacting and potent anesthetic agents will provide adequate intraoperative depth of anesthesia and speed up awakening and hence the postoperative recovery of the patient.How to cite this articleNirgude A, Hemantkumar I. Anesthetic Considerations in Microlaryngoscopy and Direct Laryngoscopy. Int J Otorhinolaryngol Clin 2017;9(1):10-14.

Cognitive Dysfunction after Surgery: An Emergent Problem

Postoperative cognitive dysfunction (POCD) results as a large problem that causes a reduction in the quality of life and increases morbidity and mortality especially in elderly patients. The increased age of patients undergoing surgery has made evident the problem and several studies evaluated pathogenesis and implemented a targeted therapy. This review analyses POCD, delirium and mild cognitive impairment (MCI) definition, risk factors and physiopathology with an analysis on anaesthesia technique influence. Unlike the postoperative delirium, POCD is more difficult to diagnose because of several tests that must be administered in the pre and postoperative period, even at a distance of time. Furthermore adequate depth of anaesthesia, monitored with Bispectral Index (BIS) or Electroencephalography (EEG), reduces the cognitive dysfunction incidence. Currently the pathogenesis is not well understood although neuro inflammation plays a central role while the importance of anaesthesia techniques has not established.

Factors that affect the onset of action of non-depolarizing neuromuscular blocking agents.

Neuromuscular blockade plays an important role in the safe management of patient airways, surgical field improvement, and respiratory care. Rapid-sequence induction of anesthesia is indispensable to emergency surgery and obstetric anesthesia, and its purpose is to obtain a stable airway, adequate depth of anesthesia, and appropriate respiration within a short period of time without causing irritation or damage to the patient. There has been a continued search for new neuromuscular blocking drugs (NMBDs) with a rapid onset of action. Factors that affect the onset time include the potency of the NMBDs, the rate of NMBDs reaching the effect site, the onset time by dose control, metabolism and elimination of NMBDs, buffered diffusion to the effect site, nicotinic acetylcholine receptor subunit affinity, drugs that affect acetylcholine (ACh) production and release at the neuromuscular junction, drugs that inhibit plasma cholinesterase, presynaptic receptors responsible for ACh release at the neuromuscular junction, anesthetics or drugs that affect muscle contractility, site and methods for monitoring neuromuscular function, individual variability, and coexisting disease. NMBDs with rapid onset without major adverse events are expected in the next few years, and the development of lower potency NMBDs will continue. Anesthesiologists should be aware of the use of NMBDs in the management of anesthesia. The choice of NMBD and determination of the appropriate dosage to modulate neuromuscular blockade characteristics such as onset time and duration of neuromuscular blockade should be considered along with factors that affect the effects of the NMBDs. In this review, we discuss the factors that affect the onset time of NMBDs.

Erratum: Factors that affect the onset of action of non-depolarizing neuromuscular blocking agents.

[This corrects the article on p. 500 in vol. 70, PMID: 29046769.].

Ventilation of Nonparalyzed Patients Under Anesthesia with Laryngeal Mask Airway, Comparison of Three Modes of Ventilation: Volume Controlled Ventilation, Pressure Controlled Ventilation, and Pressure Controlled Ventilation-volume Guarantee.

Background:Pressure controlled ventilation (PCV) is the preferable mode of ventilation of nonparalyzed patients undergoing anesthesia with laryngeal mask airway (LMA) as compared to volume controlled ventilation (VCV) and spontaneously breathing patient. In this study, we compared the PC–volume guarantee (PC-VG) mode of ventilation with VCV and PCV modes.Materials and Methods:A total of 30 patients, American Society of Anesthesiologists (ASA) physical status Classes I and II, scheduled for elective surgery under general anesthesia with a classic LMA were ventilated, subsequently, with the three modes of ventilation: VCV, PCV, and PC-VG for 10 min each mode. Tidal volume set for all patients was 8 ml/kg of ideal body weight. Parameters measured with modes of ventilation include peak inspiratory pressure (PIP), compliance, measured tidal volume, O2 saturation, end-tidal CO2, and presence of an oropharyngeal leak.Results:The PIP was significantly higher with the application of VCV mode of ventilation than PCV and PC-VG modes. The compliance was significantly lower when using the mode of ventilation VCV than PCV and PC-VG. The PIP and the compliance were not statistically different between the PCV and PC-VG modes of ventilation.Conclusions:Ventilation of nonparalyzed patients with LMA under anesthesia with PC-VG is advantageous over VCV in reducing PIP and increasing lung compliance. No difference was noted between PCV and PC-VG in ASA Classes I or II under the adequate depth of anesthesia in patients with normal pulmonary function.

Spontaneous Respiration with Dexmedetomidine for Removal of Subglottic Airway Foreign Body in an Infant: A Case Report

Anesthesia risks for surgery of airway foreign body removal are very high. A safe way to anaesthetize the patients is important. This report presented a case of an infant with a foreign body in the subglottic area, which was ultimately removed by rigid laryngoscopy under spontaneous respiratory using dexmedetomidine (DEX). A loading dose of DEX 4 μg&middotkg-1 and sevoflurane 2 MAC could provide adequate depth of anesthesia during inserting the rigid bronchoscopy, and DEX 3 μg&middotkg-1&middoth-1 was suitable for the maintance of anethesia with spontaneous respiratory. We considered that the maintenance of spontaneous respiration is one of the key points.

Our clinical experiences in ultra-sound guided peripheral nerve blocks: a retrospective evaluation

Peripheral nerve blocks are commonly used in extremity surgeries for anesthetic and/or postoperative analgesic purposes with general anesthesia. Ultra-sound (US) guided peripheral nerve blocks that have been used in recent years provide many superiorities in comparison with other conventional methods. The objective of this retrospective study was to carry out a retrospective evaluation of our experiences regarding 400 patients on whom US guided peripheral nerve was applied at the Inonu University Faculty of Medicine, Department of Anesthesiology and Reanimation during June 2012-March 2016. Demographic data of the patients, block type, purpose of block (for surgical or analgesic), type and volume of the local anesthetic, type of US probe, needle length, block success, toxicity finding and complications were all recorded. Blocks were performed for analgesia in 16% of the patients and for anesthesia in 84%. Lidocaine+bupivacaine combination, bupivacaine+prilocaine combination and bupivacaine were used on 82%, 13% and 5% of the patients as local anesthetic agent, respectively. Linear US probe (6-13 MHz) was used for all patients. In conclusion, US guided peripheral nerve blocks provide adequate depth of anesthesia and analgesia. It was found to be safe and useful and may be a good alternative to general anesthesia.

Evaluation of total intravenous anesthesia with propofol-guaifenesin-medetomidine and alfaxalone-guaifenesin-medetomidine in Thoroughbred horses undergoing castration.

Anesthetic and cardiorespiratory effects of total intravenous anesthesia (TIVA) technique using propofol-guaifenesin-medetomidine (PGM) and alfaxalone-guaifenesin-medetomidine (AGM) were preliminarily evaluated in Thoroughbred horses undergoing castration. Twelve male Thoroughbred horses were assigned randomly into two groups. After premedication with intravenous (IV) administrations of medetomidine (5.0 µg/kg) and butorphanol (0.02 mg/kg), anesthesia was induced with guaifenesin (10 mg/kg IV), followed by either propofol (2.0 mg/kg IV) (group PGM: n=6) or alfaxalone (1.0 mg/kg IV) (group AGM: n=6). Surgical anesthesia was maintained for 60 min at a constant infusion of either propofol (3.0 mg/kg/hr) (group PGM) or alfaxalone (1.5 mg/kg/hr) (group AGM), in combination with guaifenesin (80 mg/kg/hr) and medetomidine (3.0 µg/kg/hr). Responses to surgical stimuli, cardiorespiratory values, and induction and recovery characteristics were recorded throughout anesthesia. During anesthesia induction, one horse paddled in group PGM. All horses from group AGM were maintained at adequate anesthetic depth for castration. In group PGM, 3 horses showed increased cremaster muscle tension and one showed slight movement requiring additional IV propofol to maintain surgical anesthesia. No horse exhibited apnea, although arterial oxygen tension decreased in group AGM to less than 60 mmHg. Recovery quality was good to excellent in both groups. In conclusion, TIVA using PGM and AGM infusion was available for 60 min anesthesia in Thoroughbred horses. TIVA techniques using PGM and AGM infusion provided clinically acceptable general anesthesia with mild cardiorespiratory depression. However, inspired air should be supplemented with oxygen to prevent hypoxemia during anesthesia.

Chemical restraint of captive Kinkajous Potos flavus (Schreber, 1774) (Carnivora: Procyonidae) using a ketamine, xylazine and midazolam combination and reversal with yohimbine

Detailed information on the anaesthetic and cardiorespiratory effects of drug combinations used for the chemical immobilization of Kinkajous (Potos flavus) is scarce. This study assessed the effects of ketamine (2.5mg/kg), xylazine (1mg/kg) and midazolam (0.5mg/kg) combination in P. flavus. Five clinically healthy adult Kinkajous of both sexes were included. Heart rate, respiratory rate, oxygen saturation, blood pressure and body temperature were recorded at five-minute intervals for 25 minutes. Then, animals received 0.125mg/kg of yohimbine by intramuscular injection. Anaesthetic depth was assessed based on stimulus response and muscle tone. Induction, immobilization, and recovery periods were recorded and qualitatively assessed based on the absence of adverse effects. The durations of the induction, immobilization, and recovery periods were 9.42±1.73, 33.33±2.16, and 31.37±5.82 minutes. All periods showed good quality and adequate anaesthetic depth was achieved. Mean heart and respiratory rates were 99±20 beats/minute and 44±9 breaths/minute. Both parameters decreased over the duration of the anaesthesia but they did not reach levels suggesting either bradycardia or bradypnea. Mean body temperature was 37.1±1.5 0C and it also showed a decreasing trend over the duration of the anaesthesia. Mean oxygen saturation was 92±6% and it showed a mildly increasing trend over the duration of the anesthesia. Mean blood pressure was 129±23 mmHg and mild to moderate hypertension was observed. No mortality occurred and no adverse effects were observed in any of the individuals during the three months following immobilization. The assessed anaesthetic combination effectively immobilized the P. flavus individuals, provided good quality and acceptable duration of both induction and recovery periods. It should, however, not be used in Kinkajous with either known hypertension record or pre-existing target organ disease (e.g., renal failure, retinopathy).

Anaesthetic management of a patient with glucose-6-phosphate dehydrogenase deficiency undergoing robotic-assisted laparoscopic radical prostatectomy

Glucose-6-phosphate dehydrogenase deficient patients may develop acute haemolysis after exposure to the oxidative stress of surgery, and certain anaesthetic or analgesic agents. The steep Trendelenburg position, pneumoperitoneum, and associated extreme hemodynamic changes in robotic surgery add on to oxidative stress. Here, we present a 68-year-old Glucose-6-phosphate dehydrogenase deficient patient who uneventfully underwent robotic-assisted laparoscopic radical prostatectomy focussing on avoidance of drugs predisposing haemolysis, minimising surgical stress, providing adequate anxiolysis, analgesia, stable haemodynamics and depth of anaesthesia that is unique to robotic surgery.

Principles of total intravenous anaesthesia: practical aspects of using total intravenous anaesthesia

### Key points Advanced pharmacokinetic models for target-controlled infusion (TCI) have facilitated an increasing use of total i.v. anaesthesia (TIVA) in various clinical settings. The technical complexity and labour-intensive methodology of TIVA can deter clinicians and lead to default use of a volatile agent. In theory, any combination of i.v. hypnotic(s) and opioid(s) can be used and opioid-free techniques are described. In practice, the synergy between TCI infusions of propofol and remifentanil proves highly effective at obtunding response to noxious stimuli1 and for this article constitutes ‘ideal’ TIVA. This drug combination achieves equilibrium between adequate depth of anaesthesia and rapid recovery. Intermittent boluses of agents or manually controlled infusions may produce an inadequate effect.2 The specific indications for TIVA are given in Table 1. TIVA is applicable to nearly all types of surgery but has particular value in clinical scenarios where a stress-free awake extubation free of laryngospasm is required. TIVA confers many advantages over a conventional volatile technique, particularly a better recovery profile with reduced risk of postoperative nausea and vomiting, and can facilitate intraoperative wake-up while retaining amnesia. The use of TIVA for cases requiring a rapid intubation sequence is controversial but is safely practiced. View this table: Table 1 Specific indications for …

Efficiency of Bilateral Subcostal Transversus Abdominis Plane Block to Complement General Anaesthesia in Laparoscopic Cholecystectomy

Introduction: Laparoscopic Cholecystectomy is presently a commonly performed surgical procedure. It is needed in both the young and the old; healthy as well as the severely co-morbid. During the surgery, pain is generated at the port site and also from the viscera. Bilateral Subcostal (Upper Quadrant) Transversus Abdominis Plain Block can block the pain from the parietal port sites. This study is to assess the efficiency of Bilateral Subcostal Transversus Abdominis Plane Block as a mode of multi-modal analgesia in the General Anaesthesia administered for Laparoscopic Cholecystectomy. Material and Methods: One hundred patients of ASA 1 or 2 categories in the age group 20 to 60 years from both sex posted for elective Laparoscopic Cholecystectomy was included in the study. Fifty patients each was randomly assigned to two groups ‘A’ and ‘B’. Group A was the control group and did not receive any blocks. The surgery was done solely under General Anaesthesia. In the group ‘B’, Bilateral Subcostal TAP block with 30 ml of 0.25% Ropivacaine was administered from the Block Room. General Anaesthesia in a standardised protocol for the study was administered by a different Anaesthetist who was blinded about the blocks. The extra amount of Fentanyl required per hour to maintain adequate anaesthesia was noted in every patient. Minimum concentration of Sevoflurane demanded by individual patients is also noted. Systolic BP value range of ‘Control BP to an additional 15mm of Hg’ is targeted as adequate anaesthetic depth in this study. Post Operative Analgesia also had a standard protocol for all the patients. The additional dose Inj. Tramadol to control the pain in the 8 post operative hours is also noted. Results: The study demonstrated a statistically significant decrease in the intra operative inhalational anaesthetic and narcotic analgesic demand, in the Group B in which Bilateral Subcostal TAP Block was administered. The decrease in the 8 hour post operative analgesic demand in the Group B was found to be statistically significant.

Effect of Oral Clonidine Premedication on Propofol Consumption for Patient Undergoing Laparoscopic Cholecystectomy

Background: Various goals of premedication includes anxiolysis, sedation, amnesia, analgesia, attenuation of autonomic reflexes, and reduction of anaesthetic dose requirement. Preanaesthetic oral clonidine has been shown to produce anxiolysis, sedation and attenuation of hemodynamic stress response to tracheal intubation.Objective: To investigate the clinical efficacy of oral clonidine on propofol consumption in patients undergoing laparoscopic cholecystectomy.Methods: This was a prospective, randomized, double-blind placebo controlled study conducted in ninety consecutive patients randomly divided into three equal groups (placebo, tab. clonidine 150 mcg and tab. clonidine 300 mcg) meeting inclusion and exclusion criteria who underwent laparoscopic cholecystectomy. Study drug was given 60 minutes before induction of anaesthesia. Anaesthesia was induced with intravenous pethidine 1mg/kg followed by propofol . The dose of propofol for loss of verbal command was recorded. Anaesthesia was maintained with propofol at the rate of 10 mg/kg/h for 10 minutes then to 8 mg/kg/h for 10 minutes and ultimately decreased to 6 mg/kg/h after tracheal intubation. The rate of propofol infusion was adjusted by 2mg/kg/h to obtain adequate depth of anaesthesia (maintaining hemodynamic parameters within 20% of baseline).Results: The propofol induction dose was less in clonidine 150 mcg (1.2±0.2 mg/kg) and clonidine 300 mcg (1.08±0.24 mg/ kg) groups as compared to placebo group ( 1.4±0.3 mg/kg) (p=˂0.001). The rate of propofol infusion in mg/kg/h and in mcg/kg/h was lower in clonidine 150 mcg (6.7±1.6 and 121.3±11.37) and clonidine 300 mcg (7±1.4 and 120.0±9.8) groups as compared to placebo (10±3.2 and 148.0±32.53) group (p =˂ 0.001).Conclusion: oral clonidine premedication reduces propofol requirement for induction and maintenance of anaesthesiain patients undergoing laparoscopic cholecystectomy.Health Renaissance 2014;12(3): 204-208

Total intravenous anaesthesia using propofol and sufentanil allows controlled long-term ventilation in rabbits without neuromuscular blocking agents.

The aim of this study was to evaluate a total intravenous anaesthesia (TIVA) protocol using propofol and sufentanil without neuromuscular blocking agents (NBAs) for a non-recovery lung pathology study in rabbits including 10 h of pressure-controlled ventilation. TIVA was started with 20 mg/kg/h propofol and 0.5 µg/kg/h sufentanil. The depth of anaesthesia was assessed by reflex testing and monitoring of spontaneous movements or respiratory efforts. Vital parameters were monitored to assess the effects of the TIVA protocol. The infusion rates were increased whenever reflex testing indicated inadequate depth of anaesthesia, and were reduced when vital parameters indicated unnecessarily deep levels. Median infusion rates of 35 mg/kg/h propofol and 2.0 µg/kg/h sufentanil were needed to ensure an adequate depth of anaesthesia. This protocol suppressed spontaneous movements, breathing and palpebral reflexes, but was unable to suppress corneal and pedal withdrawal reflexes. Since significant drops in arterial blood pressure (ABP) were observed and the animals were not exposed to painful procedures, positive corneal and pedal withdrawal reflexes were tolerated. In conclusion, propofol and sufentanil is a suitable combination for long-term anaesthesia in non-recovery lung pathology models in rabbits without painful procedures. ABP must be monitored carefully because of the circulatory side-effects, but it is an inappropriate surrogate marker for depth of anaesthesia. Due to the lack of neuromuscular blockade this TIVA protocol allows the adjustment of infusion rates based on reflex testing. The resulting decreased risk of unnoticed awareness is a decisive refinement in anaesthesia for similar studies including long-term mechanical ventilation in rabbits.

Of Penguins, Pinnipeds, and Poisons: Anesthesia on Elephant Island.

Although Ernest Shackleton's Endurance Antarctic expedition of 1914 to 1916 is a famous epic of survival, the medical achievements of the two expedition doctors have received little formal examination. Marooned on Elephant Island after the expedition ship sank, Drs. Macklin and McIlroy administered a chloroform anesthetic to crew member Perce Blackborow to amputate his frostbitten toes. As the saturated vapor pressure of chloroform at 0°C is 71.5 mmHg and the minimum alveolar concentration is 0.5% of sea-level atmospheric pressure (3.8 mmHg), it would have been feasible to induce anesthesia at a low temperature. However, given the potentially lethal hazards of a light chloroform anesthetic, an adequate and constant depth of anesthesia was essential. The pharmacokinetics of the volatile anesthetic, administered via the open-drop technique in the frigid environment, would have been unfamiliar to the occasional anesthetist. To facilitate vaporization of the chloroform, the team burned penguin skins and seal blubber under overturned lifeboats to increase the ambient temperature from -0.5° to 26.6°C. Chloroform degrades with heat to chlorine and phosgene, but buildup of these poisonous gases did not occur due to venting of the confined space by the stove chimney. The anesthetic went well, and the patient-and all the ship's crew-survived to return home.