Review Article - Journal of Anesthetics and Anesthesiology (2017) Volume 1, Issue 1
Fundamental practices of anesthesia that physician can do to permit surgery of a patient
- *Corresponding Author:
- Dr. Sarwar M Nuclear Institute for Food and Agriculture (NIFA) Tarnab, Peshawar, Pakistan Tel: (+92 41) 9201316-20; Ext. 330. Fax: (+92 41) 9201472 E-mail: [email protected]
Accepted date: July 17, 2017
Citation: Sarwar MH, Nadeem A, Nadeem J, et al. Fundamental practices of anesthesia that physician can do to permit surgery of a patient. J Anest Anesthes. 2017;1(1):10-15.
The practice of anaesthesia is fundamental to the field of medicine and it assists in performing the trouble-free medical procedures, which would result an intense or unbearable discomfort to an un-anesthetized patient. In this article, the main components of fundamental practices of anesthesia to permit surgery of a patient are described. A local anesthesia is somewhat procedure to make the nonexistence of feeling in a particular portion of body commonly with the objective of encouraging a limited insensitivity. A general anaesthesia is a state of controlled unconsciousness and drugs specified to make general anaesthesia can be vapours or gases (inhalational anaesthetics), otherwise injections (intravenous anaesthetics or even intramuscular). For organizing a health practice, the medical attention supplier providing anesthesia selects and regulates the dosages of single or more medications to accomplish the nature and amount of anesthesia features suitable for the category of technique of a specific patient. There are both major and minor risks of Anesthesia, but common grievances comprise vomiting and nausea, headache, dental damage, surgical pain, dizziness and drowsiness, sore throat, superficial thrombosis and peripheral nerve injury. However, in latest anaesthesia, severe complications are infrequent and new medications, apparatus, exercises and trainings have organized it a sufficient harmless technique doting current periods. Risk can be removed through awareness during anesthesia, progresses in patient’s intensive care and discomfort managing, and the improvement of innocuous anesthetics agents as well as their ways of provision. Every anaesthesiologist should practice specialized judgement for defining an appropriate sequence of deeds for any patient's circumstances. Rules, regulations and laws of state, and court ideas have identified that health provider professionals should share corresponding practice capacities and accountabilities. For instance, an obligation recognized in a state’s medical practice act or rules might as well, be involved in the practice rules and act leading to nursing.
Anesthesia, Patient satisfaction, Post-operative complications, Surgery.
Anaesthesia is a word derived from the Greek word and meaning 'loss of sensation' with objectives of loss of awareness, reduces movement in response to stimuli and minimize autonomic responses to surgical stimuli. These objectives can be achieved with one drug, but at the expense of side effects and toxicity. Anaesthesia permits disturbing and excruciating processes to be executed with a slight suffering to the patient. A balanced Anesthesia uses a combination of agents, to limit the dose and toxicity of each drug. Especially, in the surgery and dentistry practices of medicine, anaesthesia or Anesthesia is a term induced for loss of feeling or consciousness. It can comprise analgesia (prevention or relief from pain), amnesia (loss of memory), paralysis (muscle relaxation), or insentience. A patient under the possessions of anaesthetic drugs is stated to as being anesthetized. Within both the nursing and medical occupations, Anesthesia is a documented specialty, and fundamentally anaesthesiologist is a doctor and an anaesthetist is a nurse. In other word, the medical specialty is called Anesthesiology and a physician practicing it is designated an anaesthesiologist, while the management carried out is mentioned as Anesthesia or anaesthetics. Anesthesia is not a special training of treatment or medicine, but drops inside the opportunity of practice of both occupations. Anesthesia permits the trouble-free presentation of therapeutic processes that would result harsh otherwise unbearable pain to an un-anesthetized patient. It is practiced in operating rooms, intensive care units, as well as labour and delivery suite [1,2].
The primary efforts at general Anesthesia have been probably by herbal remedies and alcohol is the oldest known sedative. Extracts of more than a few diverse foliage such as opium poppy (Papaver somniferum L.), abstract made from the mandrake fruit and usage of wine with incense have offered Anesthesia for medical dealings. Likewise include bhang (a beverage prepared from the leaves, flowers and buds of the female cannabis plant), extracts of juniper (coniferous plants) and coca plant (Erythroxylum coca) Lam. and cocaine may well have been used as a topical anaesthetic . Three Arab physicians, for instance, Abu al-Qasim al-Zahrawi (936- 1013), Ibn Sīna (980-1037) and Ibn Zuhr (1091-1161), are amongst many experts who accomplished operations under inhaled Anesthesia by usage of aromatics and narcoticsoaked sponges by placing below the nose of a patient during surgery. Throughout the sequence of research, the anaesthetic possessions of nitrous oxide other than its possible advantages in relieving pain during surgery have been revealed. Later on, the earliest intravenous anaesthetic, sodium thiopental has been manufactured and numerous innovative inhalational and intravenous anaesthetics have been established and conveyed into medical usage in the course of the second half of the 20th century [4,5].
Contrasting to the anaesthetists of the past, which utilized a single agent like ether or chloroform alone for anaesthesia, the current day anaesthetists use different drugs for specific effects. This helps them to avoid using large doses (causing dangerous side effects at times) of a single drug that is often required to produce sleep, lack of pain sensation and muscle relaxation simultaneously. The later development of anaesthetics that can be administered through the veins as an injection and machines, is continuously helpful to monitor the patient's vital parameters to pick up changes in the heart, pulse or almost every organ in the body and quickly take remedial steps if required. The digital revolution of the 21st century has fetched new-fangled equipment to the skill and discipline of tracheal intubation. Quite a lot of industrialists have established video laryngoscopes that work as digital expertise, for instance, the complementary metal-oxide semiconductor active pixel sensor (CMOS APS) to create a vision of the glottis, so that the trachea may be intubated. Thus, today, anaesthesia is safe, versatile and indispensable to the patient .
During general Anesthesia drugs are administered to provide hypnosis, ensure analgesia and skeletal muscle relaxation. In this paper, the main components of a newly developed controller for skeletal muscle relaxation are described . The effort of Anesthesia may be refined into three primary goals or end arguments:
1. Hypnosis (a short-term injury of realization and through it a harm of retention. The word hypnosis, in a pharmacological background generally has this practical implication, in divergence to its further acquainted lay or psychological implication of a reformed state of realization not essentially affected by medicines).
2. Analgesia (A nonexistence of impression that too diminishes autonomic reflexes).
3. Muscle relaxation (administration of neuromuscular blocking agents). Muscle relaxants facilitate safe tracheal intubation and led to profound advances in airway management.
About anaesthetic management, published reports suggest that the risk of morbidity and mortality associated with anesthesia is extremely low. These findings provoked discussion and criticism in the scientific community, since several other factors can contribute to mortality during long study periods. In few studies, if the observation period is limited to the time during which patients are hospitalized, this avoids the impact of coincidental factors on morbidity and mortality .
Broad categories of anaesthesia
Pain clinic surgery has been practiced for thousands of years. By applying pressure to major nerve trunks, anesthesia can be produced. But, this compression itself causes pain in patient. One of the ultimate exercises of anaesthesiologists is that of general (wide-ranging) anesthesia, in which a patient is engaged in a medical coma. This practice is executed to perform surgery deprived of the person reacting to discomfort (analgesia) during operation otherwise memorizing the surgery. If the general anesthesia is not compulsory, at that moment regional anesthesia may be implemented to encourage analgesia in a portion of the body. For instance, epidural supervision of a local anaesthetic is generally achieved on the mom during delivery to lessen the ache while allowing the mother to be wakeful and vigorous in labour and delivery (general anesthesia would not allow this) . Generally, there are following three main types of anaesthesia exist:
General anesthesia overwhelms the activity of central nervous system, and consequences in insentience and complete absence of consciousness. In general anaesthesia, the person is anaesthetized, either by usage of intravenous medications, otherwise with gaseous substances, and sometimes through muscles paralyzed, necessitating control of breathing through automatic aeration. A general anaesthetic yields a state of skilful insentience throughout which patient feels nothing. Patient will receive anaesthetic medicines (a gas to breathe and or an injection), like oxygen to inhale and from time to time a medicine to relax muscles. Patient will requisite a respiring tube within throat while is anaesthetised, to create assured that anaesthetic gases and oxygen be able to transfer certainly into lungs. If patient has been provided medicines that relax muscles, she or he will not be able to breathe for himself and a ventilator) (breathing machine will be used). As soon as the process is ended, the anaesthetic is discontinued and person regains consciousness. Its advantages are that the patient will be insensible throughout the process of operation. Of the sideeffects and dangers of general anaesthetics are defined well in the literature. Disadvantages include that a general anaesthetic and no-one else does not deliver discomfort release later the operation. Patient wills requisite type of aching release subsequently. Heavy-duty ache releasing drugs may be used that create people to sense relatively unwell. Or anaesthesiologist may possibly cartel the general anaesthetic with a nerve block, or with wound infiltration to benefit with pain subsequently. These are the further measures that patient may well be presented which should lessen pain and create the entire skill additionally at ease [10,11].
Sedation overwhelms the central nervous system to a slighter amount, deterring equally to anxiety and formation of longstanding reminiscences devoid of resultant in insentience. Sedation is repeatedly practiced with a spinal anaesthetic to create a patient undisturbed and lethargic throughout the operation procedure. Moreover, sedation may be slight or profound, subjected to preferences of patient. Light sedation means patient is relaxed, but awake. Whereas, deep sedation means patient is further probable to be sleeping and to a lesser quantity of possible to remember about anything occurred throughout the operation. However, every person is not appropriate for deep sedation. Sedation may frequently be tailored to patient’s preference and persons who have sedation frequently have more or less reminiscences of being conscious in operation theatre. Patients should talk over the usage of sedation with anaesthetist concerned; so that they recognize anything they would like .
Regional anesthesia and local anesthesia
Both regional Anesthesia and local Anesthesia, break apart the conduction of nerve impulses in the middle of the central nervous system and a targeted portion of the body, resulting in harm of sensation in the targeted part of body. A patient underneath regional or local Anesthesia remnants sensible, except hen general anaesthesia or sedation is managed at the similar period. Two broad classes existing are:
The peripheral blockade hinders sensory sensitivity in an isolated fragment of the body, such as managing a nerve block to inhibit sensation in an entire limb or numbing a tooth for dental work.
The central or neuraxial, blockade manages the anaesthetic in the section of the central nervous system itself by suppressing incoming sensation from outside the area of the block. Its examples comprise epidural anaesthesia and spinal anaesthesia.
Regional anaesthesia can be designated as central where anaesthetic drugs are managed directly in otherwise around the spinal cord, blocking the nerves of the spinal cord (e.g., epidural or spinal anaesthesia). This may be skilled in four different techniques:
1. Nerve block is formed by the inoculation of a local anaesthetic solution in a nerve trunk, or other large nerve branches by blocking of impulses throughout it.
2. Spinal Anesthesia is the inoculation of the solution into the subarachnoid space.
3. Caudal or epidural Anesthesia is the inoculation of the solution through the sacral hiatus and the medicine moves in the spinal canal underneath the Dural sac and reaches the nerves emerging from it. This technique makes Anesthesia in the low pelvic, perineal and anal regions. The chief advantage of this technique is that ventilation is not required (on condition that the block is not as well high). Regional anaesthesia may too be peripheral, for instance, plexus blocks - brachial plexus, nerve blocks - femoral, and intravenous blocks whilst stopping intravenous flow out of the region - Bier's block. In local anaesthesia, the anaesthetic is applied to specific location, generally topically otherwise intravenously.
4. The two customary techniques for generating this influence are:
i. The topical application to mucous membranes of the alkaloidal drug cocaine, otherwise a derivative there-of.
ii. Hypodermic injection of a dilute solution of the nonirritating sodium salt of a synthetic medicine, wherein novocaine (procaine hydrochloride), derivative of benzoic acid, is the utmost frequently used [13,14].
Approaches of administration
Medications specified to make general anaesthesia may be either as vapours or gases (inhalational anaesthetics), otherwise as injections (intravenous anaesthetics or even intramuscular). It is probable to provide anaesthesia merely by injection or inhalation, however utmost generally, the two practices are pooled, such as with an injection set to make anaesthesia and a gas used to continue it.
The drug goes in via the lungs wherein inhalational anaesthetic materials are one or the other volatile liquids or gases, and are generally provided by means of an anaesthesia machine. An anaesthesia machine permits the constituting a mixture of oxygen, anaesthetics and ambient air, supplying it to the patient and observing of patient and machine factors. Liquid anaesthetics are turned to vapours in the machine and entirely of these means stake the things of being hydrophobic (i.e., as liquids, they are not easily miscible or mixable in water, and they dissolve in oils well than in water as gases). Several compounds have been used for inhalation anaesthesia, however, merely a small number are still in an extensive use. Nowadays, desflurane, isoflurane and sevoflurane are the most broadly used volatile anaesthetics and these are regularly joined with nitrous oxide. Earlier, fewer widespread, volatile anaesthetics comprise halothane, enflurane and methoxyflurane. Investigators are as well keenly discovering the usage of xenon as an anaesthetic .
Injectable anaesthetics are used for the initiation and maintenance of the state of insentience. Anaesthetists choose to practice intravenous injections, as these are quicker, usually fewer painful and extra trustworthy than subcutaneous or intramuscular injections. Amongst the most broadly practiced medicines are Propofol, etomidate, barbiturates such as methohexital and thiopentone/thiopental, benzodiazepines such as midazolam (benzodiazepines are sedatives and used in combinations with other general anaesthetics) and Ketamine, which is either used as field anaesthesia, for example, at a highway transportation events otherwise related circumstances where an operation is essential to be conducted at the sight or while there is not sufficient time to transfer to an operating room, while preferring other anaesthetics where situations permit their usage, or it is further commonly used in the operative setting. Agents used to induce anaesthesia work by modifying the function of ligandgated ion channels (also known as ionotropic receptors, are a group of transmembrane ion channel proteins which open to allow ions to pass through the membrane in response to the binding of a chemical messenger) in nerve cell membranes .
On the operation day of a person, the patient should drink or eat nothing by means of mouth (fasting). The clinic should provide perfect directions to patient regarding fasting and these instructions are rightly significant. Whenever, there is any liquid or food in patient’s stomach during anaesthetic, it can turn up into throat and may harm to the lungs. If patients are not having a general anaesthetic, they should be still informed to keep an eye on these directions. This is because a general anaesthetic may be required suddenly, and patient’s requisite to be ready for it. Anaesthetist might come across to patient before operation and her or he will dialog about which sort of anaesthetic is appropriate. In the meantime, this is very near to the time of the operation, it is valuable if patient finds out information about the options by studying of a brochure ahead of time. In preparing for a medical procedure, the health care provider giving Anesthesia chooses and determines the doses of one or more drugs to achieve the types and degree of Anesthesia characteristics appropriate for the type of procedure and the patient. The categories of medicines needed comprise general anaesthetics, sedatives, hypnotics, neuromuscular-blocking drugs, analgesics and narcotic [17,18].
Major and minor risks of anesthesia
For existent Anesthesia, severe complications are infrequent though the risk cannot be eliminated absolutely. But, up-to-date medicines, apparatus and teaching have made anaesthesia an ample harmless technique in current years. Conversely, there are equally main and slight menaces of Anesthesia. Illustrations of foremost hazards comprise pulmonary embolism, heart attack and death, while, slight dangers can comprise vomiting and postoperative nausea, and hospital readmission complications. The possibility of a difficulty arising is relative to the comparative hazard of a diversity of reasons associated to the patient's health, are the complication of the surgery being executed and the kind of anaesthetic. Among these aspects, the health of a person earlier to surgery has the extreme bearing on the chance of a problem arising. Patients normally get up within minutes of an anaesthetic being ended and recapture their intellects within hours. A single exemption is a state so-called long-term post-operative cognitive dysfunction, categorized by insistent misperception enduring for weeks or months that is very common in those persons undertaking cardiac surgery and in the elderly [19,20]. Ordinary and very common sideeffects in general anaesthetics are sickness- cured with antisickness drugs; damage to the lips or tongue, or sore throat; and drowsiness, headache, shivering, blurred vision- can be cured with fluids or medicines. The inhalation may feel difficult at first- patient will be under close observation and this usually improves rapidly. In spinal or epidural anaesthetics, patient will not be able to move legs properly for a while. If pain-relieving medicines are prearranged in spinal or epidural as well as local anaesthetic, patient may give impression as irritated. In all anaesthetics, there is pain around injection sites. Patient cannot be capable to pass water (urine) or may wet the bed. A soft plastic tube may be put in patient’s bladder (a catheter) to drain away the urine for a day or two. This is more common after spinal or epidural anaesthetics . Confusion and memory loss are common in older people, however are typically impermanent. General anaesthetics are further probable to be trailed by a period of misunderstanding, nevertheless some people turn out to be disordered afterwards having a spinal anaesthetic as well. Unusual side-effects and problems in all anaesthetics is heart attack or stroke. In general, anaesthetics, there is damage to teeth, chest infection and awareness (becoming conscious during a general anaesthetic). Occasional or very rare complications in all anaesthetics comprise serious allergic reactions to drugs, damage to nerves and Death. General anaesthetics encompass damage to eyes and vomit getting into patient lungs. An anaesthetist is expert to study wholly these hazards and will indorse an anaesthetic procedure that retains them as little as promising [22,23].
Anaesthetists proceed to take a good deal of precaution to escape all the menaces specified in this section. Anaesthetist is competent to provide a patient with additional information regarding any of these hazards and the safety measures to be taken to escape from these. The improvement of non-dangerous anaesthetic mediators, types of supply and enhancements in patient’s intensive attention and discomfort supervision during the previous some years have rendered into a decrease in anaesthetic threats. Consequently, it is imperative for anaesthesiologists to observe medical consequences and practice the facts gained to expand superiority of carefulness [24,25].
Ethical practice of anesthesia
Anesthetized patients are particularly vulnerable, and anaesthesiologists must strive to care for each patient’s physical and psychological safety, comfort and dignity. Anaesthesiologists should monitor themselves and their colleagues to protect the anesthetized patient from any disrespectful or abusive behaviour. Anaesthesiologists ought to keep confidential patient’s medical and personal information. Anaesthesiologists should provide preoperative evaluation and care and facilitate the process of informed decision-making, especially regarding the choice of aesthetic technique. Anaesthesiologists have a duty to provide for appropriate post-aesthetic care for their patients. Anaesthesiologists should not participate in exploitive financial relationships. Anaesthesiologists ought to share with all physicians the responsibility to provide care for patients irrespective of their ability to pay for their care. Anaesthesiologists have a duty to provide such care with the same diligence and skill as for patients who do pay for their care .
Anaesthesia is a loss of sensation resulting from pharmacologic depression of nerve function or from neurologic dysfunction. Entire practices of anaesthetics are hostile to the patients and for that reason permission should be acquired as for as further processes. Preferably, a patient should be provided a brochure concerning anaesthesia and at that time advised about the projected advantage and menaces of anaesthesia. Patients undergoing emergency, a surgical incision into the abdominal cavity for diagnosis or in preparation for major surgery are at elevated risk of adverse outcomes. Clinical care pathways adapted to the local environment may help to streamline the care of these patients and provide the basis for local service improvement over time. Key elements of care for these patients include repeated risk assessment, early antibiotics and resuscitation, and appropriate timely interventions provided by clinicians with the right level of experience. Within a common exercise background, it may be the obligation of physician who manages the local anaesthesia to ensure good practice and non-coercive consensus is gained. In preparing for a medical procedure, the health care provider giving anesthesia chooses and determines the doses of one or more drugs to achieve the types and degree of anesthesia characteristics appropriate for the type of procedure and the patient. The appropriate level of postoperative care must be decided by discussion between the surgeon, anaesthetist and intensivist. Considering the limits of our education, well-designed prospective randomized trials are needed to better evaluate the impact of deep hypnotic time and determine whether maintaining a lighter state of anesthesia can improve outcome.
The patient-physician relationship involves special obligations for the physician that include placing the patient’s interests foremost, faithfully caring for the patient and being truthful. Anaesthesiologists ought to promote a cooperative and respectful relationship with their professionals that facilitate quality medical care for patients. Anaesthesiologists have a duty to cooperate with colleagues including physicians, medical students, nurses, technicians and assistants to improve the quality, effectiveness and efficiency of medical care. Anaesthesiologists should provide timely medical consultation when requested and seek consultation when appropriate. Finally, the authors assume no obligation otherwise responsibility for somewhat inaccuracy or error rising from usage of any material enclosed in this paper regarding the preparation of Anesthesia.
- McCormick B. Update in anaesthesia: Education for anaesthetists worldwide. J World Federation of Societies of Anaesthesiologists. 2016; 31: 83.
- Charles JC, Jerrold L, Brian A. A practice of anesthesia for infants and children, (5th ed), Saunders-Elsevier, Philadelphia, USA, 2013; 1168.
- Rivera MA, Aufderheide AC, Cartmell LW, et al. Antiquity of coca-leaf chewing in the south-central Andes: A 3,000 years archaeological record of coca-leaf chewing from northern Chile. J Psychoactive Drugs. 2005; 37: 455-458.
- Tonner PH. Xenon: One small step for anaesthesia? (Editorial review). Curr Opin Anaesthesiol. 2009; 19(4): 382-384.
- Igram C, Ajram K. Miracle of islamic science (1st ed.), Knowledge House Publishers, Vernon Hills, IL. 1993; 200.
- Bajwa SJS, Kalra S. Logical empiricism in Anesthesia: A step forward in modern day clinical practice. J Anaesthesiol Clin Pharmacol. 2013; 29: 160-161.
- Stadler KS, Schumacher PM, Hirter S, et al. Control of muscle relaxation during Anesthesia: A novel approach for clinical routine. Trans Biomed Eng. 2003; 53: 387-398.
- Monk TG, Saini V, Weldon BC, et al. Anesthetic management and one-year mortality after noncardiac surgery. Anesth Analg. 2005;100: 4-10.
- Miller RD. Miller's Anesthesia, (7th ed). Erikson, Lars I; Fleisher, Lee A; Wiener-Kronish, Jeanine P. Young, William L, (eds). Churchill Livingstone, Elsevier, Philadelphia, USA. 2009: 3084.
- Saunders DI, Murray D, Pichel AC, et al. Variations in mortality after emergency laparotomy: the first report of the UK Emergency Laparotomy Network. Br J Anaesth. 2012; 109: 368-375.
- Merchant R, Chartrand D, Dain S, et al. Guidelines to the practice of anesthesia- Revised edition 2014. Can J Anaesth. 2014;61: 46-59.
- Honorio TB, James PR, Christopher LW, et al. Raj’s practical management of pain, (4th ed), Mosby Elsevier. Philadelphia. 2008; 44.
- Slinger P, Darling G. Principles and practice of anesthesia for thoracic surgery. Springer-Verlag, New York. 2011; 11-34.
- Jordan S, Evans TW. Predicting the need for intensive care following lung resection. Thorac Surg Clin. 2008; 18: 61-69.
- Franks NP. Molecular targets underlying general anaesthesia. Br J Pharmacol. 2006; 147(1): 72-81.
- Franks NP. General anaesthesia: From molecular targets to neuronal pathways of sleep and arousal. Nature Reviews Neuroscience. 2008; 9: 370-386.
- Kehlet H, Dahl JB. Anaesthesia, surgery, and challenges in postoperative recovery. The Lancet. 2003; 362: 1921-1928.
- Slinger PD, Johnston MR. Preoperative assessment: An anaesthesiologist’s perspective. Thorac Surg Clin. 2005; 15: 11-26.
- Tennant I, Augier R, Crawford-Sykes A, et al. Minor postoperative complications related to anesthesia in elective gynaecological and orthopedic surgical patients at a teaching hospital in Kingston, Jamaica. Rev Bras Anestesiol. 2012; 62(2): 188-198.
- Quemby D, Stocker M. Day surgery development and practice: Key factors for a successful pathway. Continuing Education in Anaesthesia, Crit Care Pain. 2014; 14: 256-261.
- Soumpasis I, Kanakoudis F, Vretzakis G, et al. Deep anaesthesia reduces postoperative analgesic requirements after major urological procedures. Eur J Anaesthesiol. 2010; 27: 801-806.
- Schnaider I, Chung F. Outcome in day surgery. Curr Opin Anaesthesiol. 2006; 19: 622-629.
- Jenkins K, Baker AB. Consent and anesthetic risk. Anaesthesia. 2003; 58: 962-984.
- Domino KB, Posner KL, Caplan RA, et al. Awareness during Anesthesia: A closed claims analysis. Anesthesiology. 1999; 90: 1053-1061.
- Jin F, Chung F. Minimizing perioperative adverse events in the elderly. Br J Anaesth. 2001; 87: 608-624.
- Van Norman GA, Rosenbaum S. Ethical aspects of Anesthesia care. In: Miller RD (ed). Miller’s Anesthesia. (7th ed), Elsevier Churchill Livingstone, Philadelphia. 2010;1: 209-220.