Michael G. Irwin|V. K. F. Kong
Quantifying and communicating peri-operative risk
University of Hong Kong|University of Hong Kong
shallow men believe luck strong men believe cause effect risk potential chosen action activity including choice inaction lead specific outcome implies choice influence outcome definitions synonymous possibility adverse event course risk also taken hope favourable outcome particularly investment also personal perspective risk fatalist personality may accepting unconcerned risk whereas pragmatic individuals know modifiable factors involved apply healthcare example even though surgery may necessary patient may pharmaceutical interventions could reduce morbidity almost human endeavour carries risk staying hospital far riskier travelling aeroplane recent study showed onenight stay hospital carries 111 risk nosocomial infection 34 risk adverse drug reaction related human error allergy 04 risk pressure ulcer due immobilisation 1 2007 usa 131 fatal crashes per 100 000 flight hours noncommercial flights 0016 per 100 000 major airlines 2 despite efforts contrary healthcare intrinsically hazardous business anaesthesia medical specialty much focused risk management patient safety consequently mortality risk attributable anaesthesia dropped dramatically years one death 1000 anaesthetic procedures 1940s one 100 000 early 2000s 3 however although anaesthesia relatively safe surgery dangerous 2000 30day mortality risk uk one death 34 emergency operations 29 1177 elective surgery 06 4 european surgical outcomes study observational study data collected 46 539 patients aged 16 years undergoing noncardiac surgery sevenday period 498 hospitals across 28 european nations 5 considerable variability country country median death rates 3 elective 10 emergency surgery anaesthesia excellent track record patient safety described leading medical specialty addressing issues 6 yet apparent perioperative process still great potential hazard host factors anaesthesia one ronald howard pioneer decision analysis wanted develop scale would clearly confer risk rather percentages coined term microprobability refer event chance one million concept micromort micro mortality one million chance death 7 face risk simply alive may exacerbated indulging various activities mobile app available illustrating many micromorts involved daily activities see httpsplaygooglecomstoreappsdetailsidcomzanzibartechmicromorts use micromorts allows us actually quantify risk translate whole numbers micromort denotes one million chance death onetime dangerous events concept easily understood compared one million chance course rare also everyday occurrence example chance particular individuals winning weekly lottery less 1 32 million people conversely jackpot gets almost every week somebody micromorts expression acute risks event completed risk gone risk surgical anaesthesia range various daytoday activities audits risk death general anaesthetic alone vary considerably geographically may around one death 100 000 operations developed country 8 equates 10 micromorts per operation risk death average riding motorcycle 60 miles skydiving micromorts rely aggregated risk data calculations applicability specific circumstances individuals limited contrast micromorts also unit called microlife risk gain representing 30minute change life expectancy 9 way measuring impact longterm habits human body example smoking two cigarettes cost one microlife whereas bonus life gained taking statin daily one microlife per day 20 minutes moderate exercise daily two microlives per day userfriendly microlife calculator see httpjournalsbmjcomsitemicrolives available people general notoriously bad calculating risk concept micromort microlife useful explaining various risks daily perioperative practice general public shared decisionmaking healthcare context often depends understanding numerical information either text graphical format perception harm benefit associated particular options important many health decisions surprisingly patients many doctors severe problems mastering host numerical concepts prerequisites understanding information harm benefit medical treatments 10 highly educated people still difficulty relatively simple numeracy questions 11 numeracy influences processing numerical nonnumerical information less numerate individuals susceptible framing effects easily affected nonnumerical information mood states less sensitive different levels numerical risk 12 berlin numeracy test new psychometric instrument assessing statistical numeracy risk literacy educated population 13 typically takes three minutes complete online version also available see httpwwwriskliteracyorg statisticians clinicians psychologists recommended use numerical opposed verbal descriptions risk communication 1416 addition probability information way people perceive risk message may influenced framing risk information risk comparisons messages qualitative content trust 17 conveying relative risks alone without absolute risk baseline risk example nontransparent framing comparing benefits harm using different scales reporting benefits big numbers relative risk reduction harm small numbers absolute risk increases another way altering risk perception example 1995 contraceptive pill scare uk alarming figure 100 increase relative thrombosis caused thirdgeneration oral contraceptive pills much terrifying humble increment absolute risk one 7000 two 7000 18 humans prone unwittingly tricking representative bias risk assessment gambling pursuits purchasing lottery tickets odds winning lottery one million buying two tickets double chance two million apparent 100 increase however odds winning jackpot buying two lottery tickets hardly changes 999999 999998 change 00001 nontransparent mismatched framings common phenomena even scientific research published leading medical journals studies revealed half articles report relative risks odds ratios one third adopt mismatched framing riskbenefit discussion 19 20 risk communication incomplete misleading numerical descriptions hinders shared decisionmaking patients likely familiar concept risk human nature many understand relativity perhaps even choose ignore use gambling example recent 640 million lottery usa created much excitement scramble buy tickets odds winning approximately one 175 million number may mean much relative terms chance winning 175 times less struck lightning given year fact helps conceptualise probability life zero risk certainty branch medicine risks less acceptable communicating risk information important unfortunately difficult might expected patients values preference essential elements shared decisionmaking 2011 report perioperative care surgical patients published national confidential enquiry patient outcome death principally recommended assessment mortality risk made explicit patient recorded clearly consent form medical record 21 spreadsheet developed quantify mortality risk surgery calculating mortality rates life expectancy adjustment various parameters age sex comorbidities renal function physical fitness body mass index 22 online calculator available estimating perioperative mortality order assist shared decisionmaking patients doctors nonsurgical intervention option see httpssitesgooglecomsiteinformrisk complex nature perioperative period gives rise potential significant risk patients directing efforts towards patient safety uncomplicated inexpensive yet significantly improve quality perioperative care world health organizations surgical safety checklist example simple cheap effective method reducing avoidable complications resulting surgery 23 moreover use checklist likely provide net financial benefit healthcare system cost intervention low scenarios reduction morbidity medicolegal claims anaesthesia medical discipline applied science related art perioperative risk reduction identification intervention prevention highrisk patients account 15 surgical procedures 80 deaths 24 however still major challenge identify accurately reliably patients high risk postoperative mortality morbidity cardiopulmonary exercise testing cpet measure aerobic capacity becoming widely employed estimated number tests performed uk alone estimated excess 14 000 per year 25 based possible association preoperative aerobic fitness subsequent survival surgery cpet used triaging patients occult cardiorespiratory disease investigation optimisation strategies major operations 26 nonetheless none derived variables ventilatory anaerobic threshold maximal oxygen uptake regarded cornerstone prediction survival major surgery 27 european society cardiologys guidelines preoperative cardiac risk assessment perioperative cardiac management published 2009 questioned role cpet risk assessment surgery emphasised substitute stress testing routine practice 28 scientific statement american heart association also highlighted lack randomised trials support recommendations diagnostic prognostic applications cpet 29 reliance upon single factor predicting future risk like gambling rational assessment since test infallible single variable estimate extent survival quality life although physical fitness appears important component 30 31 preoperative testing screening exercise stable patients strategic part perioperative risk reduction programme susceptible patients risk assessment always tailored individual patients preoperative tests reserved test results would positively influence change perioperative management drive optimise risk lead unnecessary investigation intervention really optimising risk assessment comprehensive history taking physical examination concerns malpractice liability result excessive unnecessary consultation hospitalisation testing treatment paradoxically safety hazard patients doctors false positive findings leading costly possibly harmful treatments investigations delays surgery quantity tests confused quality care pharmacological panacea perioperative risk optimisation one main objectives risk identification determine individuals could benefit protective therapeutic intervention intervention potentially dangerous eg coronary artery stenting careful selection absolutely essential however fairly safe simple pharmacological treatments promising regard may necessary investigate patients aggressively expensive even hazardous techniques indication surgery strong assume worst instigate protective measures anyway last decade statins investigated extensively potential multimodal effects modifying number aspects perioperative morbidity mortality 3234 possible pleiotropic effects statin therapy reduction myocardial infarction stroke prevention atrial fibrillation improvement vascular draft survival protection renal insufficiency inhibition malignant cell growth 34 perioperative applications statins offlabel primary indication lipidlowering drugs available generic form relatively inexpensive good safety profile 35 however latest cochrane review statins vascular surgery insufficient evidence conclude use statins resulted either reduction increase outcomes examined also observed widespread use statins population make difficult researchers undertake large randomised trials needed demonstrate effect 36 perioperative pharmacological interventions certain benefits may associated risk could outweigh advantages data poise trial suggested routine administration perioperative betablockers untitrated relatively high dose starting day operation increased risk stroke overall mortality noncardiac surgery presence favourable outcomes cardiovascular parameters 37 38 poise ii generated similar controversy recently use perioperative aspirin 39 anaesthesia servicebased speciality dealing specific incidentrelated risks yet reached peak despite acknowledged leading medical speciality designing failsecure systems probably specialty healthcare reached critical target six sigma defect rate 6 40 perioperative period could made safer revolutionising risk management tactics corresponding interventions preventing complications improving patient outcomes suggested technical aspects anaesthesia could delegated robots 41 ready new role perioperative risk strategists external funding competing interests declared