| Introduction |
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| Medical
students, house officers, and attending physicians encounter patients who
complain of symptoms, have signs uncovered during physical examination,
or have abnormal laboratory values identified by diagnostic tests. Patients
with such complaints have certain expectations: an explanation of the complaint's
underlying cause and if at all possible, a resolution or cure. Unfortunately,
the knowledge gained by medical students from medical school curricula
is better suited for patients who present with diagnoses already made and
expect to be told what their complaints should be. Students are better
prepared to consider "I have a myocardial infarction, tell me my symptoms,
signs, and enzyme levels", than "I have chest pain, what is wrong with
me?" . Realizing this, learners spend their early clinical years relearning
and reorganizing medical knowledge into information packets which are more
effective for the resolution of the patient problems they will encounter.
This medical education series is intended to assist learners organize their
knowledge in such a manner. |
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are three factors which influence learning and retrieval of medical knowledge
from memory: meaning, encoding specificity (the context and sequence for
learning), and practice on the task of remembering . Of the three, the
strongest influence is the degree of meaning which can be imposed on information.
To achieve success, experts organize and "chunk" information into meaningful
configurations, thereby reducing the memory load. These meaningful configurations
or systematically arranged networks of connected facts are termed schemata.
As new information becomes available, it is integrated into 'schemes' already
in existence, thus permitting learning to take place. Accordingly, one
function of schemes is the promotion of learning. In addition, the
organization and availability of medical knowledge stored in memory has
proven to be the prime determinant for diagnostic problem solving. Support
for the relationship between organization of knowledge and problem solving
led to the recommendation that for learners, an organizational scheme be
introduced to serve as a scaffold for new information and to provide a
basis for problem solving. Thus, a second function of schemes is the
advancement of problem solving. |
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| Schemes
or strategies to aid learning and problem solving have always been part
of medical education. The attribute common to all these processes is the
capacity to aid retrieval of information from memory. The techniques usually
encountered range from general memory aids applicable to virtually all
situations (congenital, acquired, neoplastic, inflammatory, etc.) to specific
ones restricted to narrow domains; they vary from mnemonics or acronyms
(e.g.MUDPILES: Methanol, Uremia, Diabetic ketoacidosis,
Paraldehyde, Isoniazid, Lactic acidosis, Ethylene
glycol, Salicylate for causes of high anion gap metabolic acidosis)
to complex, sophisticated concept maps. However, not all approaches are
equivalent in their capacity to aid learning, assist retrieval of information
from memory, and advance problem solving. Observation of expert diagnosticians
offers interesting insights into the diagnostic process. Although experts
have more basic science information than novices, it is only used when
confronted with complex problems; for routine problems, pattern recognition
is used. Pattern Recognition (meaning an awareness of similar problems
previously resolved) is the strategy selected whenever possible, but it
is possible with experience, not learning. Once the problem is recognized,
the previous solution is remembered. Basic science information is not required.
Some consider pattern recognition a cognitive process different from problem
solving because it represents remembering solutions rather than solving
problems. |
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| When
the 'pattern' is not recognized, and the alternative of an organized scheme
is not available, the universal fall-back position is a problem-solving
method termed hypothetico-deductive reasoning. This is a process
of sequential steps: early hypothesis generation, acquisition of data by
"search and scan" (based on preformed hypotheses), interpretation of data,
refinement and evaluation of hypotheses, and finally confirmation or exclusion
of hypotheses. This sequential process, termed by some the 'scientific
method' of clinical medicine, is applicable to all medical problems, but
is inefficient and prone to mistakes. It is used by the majority of practicing
physicians because it is taught in medical school, indoctrinated during
post-graduate residency training, and rewarded by examination practices.
Medical educators appear to ignore the reality that experts faced by complex
problems within their area of expertise utilize organizational schemes,
not hypothetico-deductive reasoning. For this reason, it is important for
learners to develop approaches to as many clinical presentations likely
to be encountered in their practice as possible, and use hypothetico-deductive
reasoning only if the other two strategies cannot be exploited. |
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| Schemes
organized with basic science underpinnings have benefits other than their
value for learning and their utility for problem solving. The transition
to post-graduate clinical training, and thereafter to the practice of medicine
is facilitated, whereas the need to reorganize knowledge and relearn basic
sciences disappears. The structures, if created early, are revisited in
clerkship, in residency, and again with each new patient encounter in practice.
As necessary, the schemes are altered to accommodate new concepts, new
information is inserted into existing scaffolding, and schemes are continuously
improved to serve the needs of the lifelong learner during changing situations
and environments. The schemes employed for learning are adapted for problem
solving, so that practice of the problem solving process reinforces retention
of knowledge relevant to the specific problem. Using schemes for learning
as well as problem solving provides the advantage of combining the creation
of a knowledge structure and of a search and retrieval strategy into a
single operation. |
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| This
medical education series attempts to reflect these pedagogic realities.
A finite number of clinical presentations (127) representing all the human
body's responses to an infinite number of injuries has been identified,
thus defining a comprehensive knowledge domain. A given medical discipline
reflects a portion of that domain. For example, the domain knowledge for
Nephrology is represented by 16 clinical presentations. An organizational
scheme for each presentation was designed with two purposes in mind: enhance
the meaning of the clinical information by means of basic science explanations
and provide an approach for problem solving within that domain. In the
context of the clinical presentations here, 'schemes' are defined as a
mental categorization of knowledge that includes a particular organized
way of understanding and responding to a complex situation. Successful
problem solving, as already stated, primarily depends on mastery of domain
content. Mastery in turn depends not on information quantity, but its organization.
Therefore knowledge organized into schemes (basic science and clinical
information integrated into meaningful networks of concepts and facts)
is useful for both information storage and retrieval. To become excellent
in diagnosis, it is necessary to practice retrieving from memory information
necessary for problem resolution, thus facilitating an organized approach
to problem solving (scheme-driven problem solving). Since there
is no generic problem solving process, THE OUTCOME EXPECTED IS A CLINICAL
REASONING PROCESS WHICH IS SPECIFIC AND HIGHLY TAILORED TO THE COMPLEXITY
OF EACH PROBLEM. |
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In
summary, if a scheme is to be useful, the answers to the next five questions
should be positive:
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Is it
simple and easy to remember? (Does it reduce memory load by "chunking"
information into categories and subcategories?)
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Does it
provide an organizational scaffolding that is easy to alter?
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Does the
organizing principle of the scheme enhance the meaning of the information?
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Does the
organizing principle of the scheme mirror encoding specificity (both context
specificity and process specificity)?
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Does the
scheme aid problem solving? (e.g. does it differentiate between large categories
initially, and subsequently progressively smaller ones, until a single
diagnosis is reached?)
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is no single "right" way to approach any given clinical presentation.
Each of the schemes provided represents one approach which proved to be
useful and meaningful to one experienced, expert author. Your own personalized
scheme may be better than someone else's scheme. Alter the schemes in any
way which makes them better for you. However, any scheme is better than
no scheme, lest one is compelled to regress to hypothetico-deductive reasoning. |
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| How
to use Schemes for Problem Solving |
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| Each
clinical presentation represents a common or important way in which a patient,
group of patients, community, or population presents to a physician and
expects the physician to recommend a method for managing the situation.
In order to achieve this end, physicians must establish the reason for
the visit or the nature of the concern. For a given presentation, the number
of possible reasons or diagnoses may be sufficiently large that it is not
possible to consider them all at once, or even remember all the possibilities.
Experts seldom attempt to achieve a diagnosis in such a manner, and almost
never will they conduct a 'complete history and physical examination' without
first determining where they are going. They question, examine, and investigate
patients with a pre-determined search strategy. Successful inquiries move
from general categories to more specific categories until a solution is
uncovered. The inquiries are based on pre-existing schemes which are stored
in memory and retrieved when needed. Originally, these schemes may have
been created to make sense of a problem domain, or to understand and organize
information. Later, these same schemes were altered and improved in order
to serve the need to solve problems. Finally, schemes or algorithms have
been developed for use in management and therapeutics. In this medical
education series the emphasis will be on diagnostic problem solving.
Approaches to management will be described, and special care will be devoted
to explanations (where possible) of the underlying patho-physiology for
the therapeutic approach recommended. |
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| The
schemes presented in this book include categories in enclosed spaces (encircled
or in boxes) connected by arrows. The reason for categories
and connecting arrows being organized in a certain manner is enhancement
of meaning and reduction of memory load. It is essential that the meaning
of the scheme be logical and transparent. The categories are progressively
more specific, and finally a diagnostic list is given below a category
box. The lists are not exhaustive. The reader may wish to expand these
lists as required. |
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| The
arrows are numbered, and these numbers correspond to text.
The text describes how choices may be made between alternative paths.
The "CLINICAL FEATURES" section suggests appropriate questions
to ask during history taking and areas on which to focus during
physical examination. The "INVESTIGATION" section suggests diagnostic
studies which may be indicated. Usually the choices for alternative
paths recommended are based on more than a single symptom, sign, or laboratory
value. On occasion the choice may be difficult, and errors are to be expected.
By backtracking, reviewing the basic science explanations, and taking alternative
paths, the eventual correct solution should be attainable. The "BASIC
CONCEPTS" section provides basic science explanations and/or rationale
for some of the recommendations. The more common disease categories
are enclosed by thick walls to indicate greater frequency or
importance. Additional information is included as notes. |
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