Epidemiology of Perioperative Injury – as an Environmental Perturbation
Is perioperative injury a problem?
Yes! We can see from these statistics, the surgical burden is not only expensive, but also has many life-threatening complications.
The Surgical Burden
- Patients – 33 million patients per year undergo surgery in the United States alone.
- Costs – $450 billion annually, or 40% of the national health care budget.
- Complications – 4% overall, or 1.25 million surgical patients per year have medical complications after surgery (e.g., myocardial infarction, stroke, pulmonary or renal dysfunction), costing an additional $25 billion annually.
- Projection – by 2020 the number of surgeries will increase by 25%, the costs by 50%, and the complications by 100%.
- Practice guidelines – disparate among institutions and individual practitioners.
- Therapies – few developed for high-risk surgical patients, though perioperative stresses are unique, extreme and prolonged – lasting for days to months following discharge, and therefore warrant special attention.
NHLBI Working Group Recommendations
- Perioperative complications are significant and costly, mandating that Perioperative Medicine be included as an integral part of the National agenda.
- Risk profiling deserves further attention, especially for noncardiac, nonvascular surgery and older patients. Implementation of suggested paradigms across specialties merits attention, as do patient education and discharge profiling.
- Perioperative complication assessment and reporting vary markedly among specialties, medical centers and individual clinicians. As a result, no consistent approach to informed consent has emerged, and patients cannot weigh benefit versus risk of surgery. As well, variable methodology has led to confusion regarding perceived significance, practice paradigm design, new drug efficacy, and allotment of resources. Multi-specialty, multi-center, accurate and comprehensive databases are needed.
- A National Perioperative Medicine Initiative should be enacted using government support (financial and otherwise).
- Important research questions exist, can be prioritized and should be pursued by individual groups or consortia. A comprehensive national database should be developed.
Perioperative Adverse Outcomes are Complex Phenotypes Determined by Gene-environment Interactions
Patients arrive to the operating room with a burden of complex diseases resulting from the interaction of environmental perturbations with the genetic background over their lifespan.
They are subjected to the sledge hammer of the OR environment, appropriately called “controlled trauma”, and consisting of a combination of surgical injury, exposure to CPB, anesthesia and pharmacologic interventions, all interacting with the genotypic background to result in normal responses or adverse events.
Characteristics of Perioperative Injury
Since millions of polymorphisms in our DNA have now been characterized, it is possible to look at specific DNA changes in order to predict negative surgical outcomes. It is recognized that responses to initial injurious events contribute to further tissue injury, and appear to be genetically modulated.
As an environmental perturbation, perioperative injury can be characterized as:
- Multifactorial: outcomes are the cumulative result of direct initial operative injury + responses to injury (inflammation, thrombosis, neuroendocrine stress) interacting with a genotypic background
- Quantifiable (e.g. duration of CPB, duration of AXC, volume/type/route of cardioplegia, #of grafts, perioperative medication etc.)
- Temporally Delineated: 1. defined time onset, 2. defined time course relative to common (chronic) complex diseases
Example: Perioperative Myocardial Injury
The degree of perioperative myocardial injury is a result of the balance between injurious and cardioprotective (endogenous and exogenous) biological mechanisms, mediated via a wide array of biochemical pathways with extensive genetic variability.