Pharmacology For Anaesthesia And Intensive Care Pdf
Tarja Hempton
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Background: Beta-lactam antibiotics (βLA) are the most commonly used antibiotics in the intensive care unit (ICU). ICU patients present many pathophysiological features that cause pharmacokinetic (PK) and pharmacodynamic (PD) specificities, leading to the risk of underdosage. The French Society of Pharmacology and Therapeutics (SFPT) and the French Society of Anaesthesia and Intensive Care Medicine (SFAR) have joined forces to provide guidelines on the optimization of beta-lactam treatment in ICU patients.
Methods: A consensus committee of 18 experts from the two societies had the mission of producing these guidelines. The entire process was conducted independently of any industry funding. A list of questions formulated according to the PICO model (Population, Intervention, Comparison, and Outcomes) was drawn-up by the experts. Then, two bibliographic experts analysed the literature published since January 2000 using predefined keywords according to PRISMA recommendations. The quality of the data identified from the literature was assessed using the GRADE methodology. Due to the lack of powerful studies having used mortality as main judgement criteria, it was decided, before drafting the recommendations, to formulate only "optional" recommendations.
Results: After two rounds of rating and one amendment, a strong agreement was reached by the SFPT-SFAR guideline panel for 21 optional recommendations and a recapitulative algorithm for care covering four areas: (i) pharmacokinetic variability, (ii) PK-PD relationship, (iii) administration modalities, and (iv) therapeutic drug monitoring (TDM). The most important recommendations regarding βLA administration in ICU patients concerned (i) the consideration of the many sources of PK variability in this population; (ii) the definition of free plasma concentration between four and eight times the Minimal Inhibitory Concentration (MIC) of the causative bacteria for 100% of the dosing interval as PK-PD target to maximize bacteriological and clinical responses; (iii) the use of continuous or prolonged administration of βLA in the most severe patients, in case of high MIC bacteria and in case of lower respiratory tract infection to improve clinical cure; and (iv) the use of TDM to improve PK-PD target achievement.
Conclusions: The experts strongly suggest the use of personalized dosing, continuous or prolonged infusion and therapeutic drug monitoring when administering βLA in critically ill patients.
Principle findings: Hypomagnesemia is frequent postoperatively and in the intensive care and needs to be detected and corrected to prevent increased morbidity and mortality. Magnesium reduces catecholamine release and thus allows better control of adrenergic response during intubation or pheochromocytoma surgery. It also decreases the frequency of postoperative rhythm disorders in cardiac surgery as well as convulsive seizures in preeclampsia and their recurrence in eclampsia. The use of adjuvant magnesium during perioperative analgesia may be beneficial for its antagonist effects on N-methyl-D-aspartate receptors. The precise role of magnesium in the treatment of asthmatic attacks and myocardial infarction in emergency conditions needs to be determined.
Conclusions: Magnesium has many known indications in anesthesiology and intensive care, and others have been suggested by recent publications. Because of its interactions with drugs used in anesthesia, anesthesiologists and intensive care specialists need to have a clear understanding of the role of this important cation.
Research in anesthesiology and intensive care at the Department of Physiology and Pharmacology is carried out in connection with Function Perioperative Medicine and Intensive Care at Karolinska University Hospital and Intensive Care at Astrid Lindgren Children's Hospital.
Our research projects are supported by an experimental research unit and a clinical research and outcome unit. This translational environment fosters strong research clusters around key areas of anesthesiology, intensive care and pain management. Experimental anesthesiology and intensive care form an important part of the translational research conducted at our home department.
We teach at both the undergraduate, graduate and postgraduate level. Our teaching is characterized by a combination of basic science and its clinical application, especially in highly specialized perioperative care, intensive care medicine, and pain.
For 25 years Anaesthesia, Intensive Care and Perioperative Medicine A-Z has provided a comprehensive resource of the relevant aspects of pharmacology, physiology, anatomy, physics, statistics, medicine, surgery, general anaesthetic practice, intensive care, equipment, and the history of anaesthesia and intensive care.
Originally prepared as essential reading for candidates for the Fellowship of the Royal College of Anaesthetists and similar exams, this fully updated edition will also prove as invaluable as ever for all anaesthetists and critical care physicians, as well as operating department practitioners and specialist nurses.
The mission of the Department of Anesthesia & Critical Care is to: Provide outstanding compassionate patient care; educate each other and the next generation of physicians and scientists; be leaders in scholarship, discovery and innovation; and to bring out the best in all with whom we work.
Faculty in the Department of Anesthesia and Critical Care are committed to the highest quality training and education. The Department of Anesthesia and Critical Care offers a wide variety of educational experiences for medical students, residents and fellows.
The goal of this department is to provide superior training in clinical anesthesiology and to extend this training to include an in-depth knowledge of the principles, practice and research methods of clinical pharmacology. Which we believe is essential to both the academic and private practice of anesthesia.
The Department of Anesthesia & Critical Care at the University of Chicago is committed to supporting and enhancing a diverse and inclusive environment through education, community outreach and through the mentoring and recruiting of highly motivated, talented individuals into our family.
Remifentanil is a pure μ-opioid receptor agonist. Introduced in the early 1990s, its rapid onset and offset coupled with its synergistic effects with other general anaesthetic agents make it an ideal option for anaesthesia and conscious sedation. Its repertoire is ever growing as anaesthetists and intensivists across the world push the boundaries of its use. This tutorial will cover the basic pharmacology of remifentanil, common and novel uses in clinical practice and key safety considerations.
The structure of remifentanil, like alfentanil and sufentanil, is based on its parent drug fentanyl (Figure 1). The crucial difference is the addition of an ester group (highlighted) allowing it to be rapidly metabolized by non-specific plasma and tissue esterases. This gives rise to its characteristic ultra-fast offset and allows for rapid titration.
Despite being broken down by esterases, remifentanil can be used safely in patients with pseudocholinesterase deficiency1. Its major metabolite, remifentanil acid, undergoes renal excretion and accumulates in patients with reduced renal function1,2. Despite this, the dosing of remifentanil does not need to be adjusted for renal dysfunction as remifentanil acid is almost entirely inactive1,2.
When comparing remifentanil to other short acting opioids (fentanyl, alfentanil and sufentanil), it is associated with deeper anaesthesia and analgesia intra-operatively3. This manifests as a lower blood pressure and heart rate3. Higher doses of remifentanil are associated with an increased risk of hypotension and bradycardia as well as apnoea3. It is prudent to have vasopressors and anticholinergics to hand when using remifentanil.
The pharmacokinetics of remifentanil are more closely associated with lean body weight (LBW) rather than actual body weight (ABW)1. Although obese patients do require a larger dose than their LBW would suggest, it is far less than their ABW dose; this would put them at risk of cardiovascular depression1.
Target controlled infusion (TCI) pumps adjust the rate of a drug infusion to achieve a steady effect site concentration taking into account the known pharmacokinetics of the drug and physical characteristics of the patient. The Minto model, named after one of its developers, Dr. Charles Minto, is a model for predicting the concentration of remifentanil in plasma and the effect site. While more accurate models exist (the Minto model can over-predict by as much as 15%5) its versatility and wider body of experience have led to it being the most widely used model.
The Minto model is a three-compartment model programmed to target either effect site (Cet) or plasma site (Cpt). The Cet rate constant (keo) and loss-of-consciousness effect have been derived from electroencephalogram (EEG) parameters. The initial bolus dose delivered in Cet mode is 3-4x greater when compared to Cpt; this may be associated with a greater incidence of adverse effects (e.g. chest wall rigidity, bradycardia, apnoea). Often this can be attenuated by an incremental dosing approach to the desired Cet and the bradycardia can be managed with prophylactic glycopyrrolate. It is advisable that clinicians unfamiliar with the use of remifentanil TCI use Cpt in preference to Cet.
Due to its potent respiratory depressant effects, achieving spontaneous ventilation with TCI remifentanil can be challenging especially with higher rates. If using a TIVA technique combining remifentanil and propofol it is advisable to use higher propofol rates (Cet 4-6μg.ml-1) with lower remifentanil rates (Cet 2.5ng.ml-1) in order to maintain spontaneous ventilation under general anaesthesia. Once spontaneous breathing is achieved, it may then be possible to titrate up the remifentanil in small increments (i.e. 0.05ng.ml-1) until adequate analgesia is reached. In this instance, monitoring of respiratory rate may help to guide analgesia with rates of 10-15 breaths per minute suggesting adequate analgesic control.
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