Download pre-operative assessment of the respiratory system

PRE-OPERATIVE ASSESSMENT OF
THE RESPIRATORY SYSTEM
REGISTRAR: Dr Aucamp
CONSULTANT: Dr Prins
INTRODUCTION
Goal: Determine the risk to the patient
Why:
• Contribute significantly to perioperative
morbidity and mortality
• Costly
• Longest length of stay
Estimation of risk should be a standard element of
all preoperative medical evaluations.
DEFINITION
Differing definitions account for the variability in frequency
Proposed definition by O'Donohue:
A pulmonary abnormality that produces identifiable disease or dysfunction
that is clinically significant and adversely affects the clinical course
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Atelectasis
Infection, including bronchitis and pneumonia
Prolonged mechanical ventilation and respiratory failure
Exacerbation of underlying chronic lung disease
Bronchospasm4
O'Donohue, WJ. Postoperative pulmonary complications: When are preventive and therapeutic measures necessary? Postgrad Med 1992; 91:167.
EFFECT OF MEDICAL CONSULTATION
ON SURGICAL OUTCOMES
No study has shown a decrease in perioperative morbidity
associated with medical consultation9
The practice of medical consultation is widespread
Assuming consultants make evidence-based
recommendations, it is reasonable to infer that
consultation will improve the care of the surgical patient.....
if consultative recommendations are implemented
Phy, MP, Vanness, DJ, Melton LJ, 3rd, et al. Effects of a hospitalist model on elderly patients with hip fracture. Arch Intern Med 2005; 165:796.
GENERAL PRINCIPLES OF CONSULTATION
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Determine the question and respond to it
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Establish the urgency of the consultation and provide a timely response.
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“Look for yourself”; confirm the history and physical examination and check test results.
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Be as brief as appropriate; be definitive and limit the number of recommendations.
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Be specific, including medication details.
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Provide contingency plans; anticipate potential problems and questions.
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“Honour thy turf”; don't steal other physician's patients.
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Teach with tact; consult, don't insult.
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Talk is cheap and effective; direct verbal communication is crucial.
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Follow-up to ensure that recommendations are followed
PERIOPERATIVE PULMONARY PHYSIOLOGY
Complications follow logically as an extension of normal perioperative pulmonary
physiology
Thoracic and upper abdominal surgery is associated with a reduction in lung volumes:
• VC is reduced by 50 to 60 % and may remain decreased for up to one week.
• FRC is reduced by about 30%
Important factors:
• Diaphragmatic dysfunction
• Postoperative pain and splinting
Reduction of the FRC below closing volumes contributes to atelectasis, pneumonia,
and V/Q mismatching
Microatelectasis
PERIOPERATIVE PULMONARY PHYSIOLOGY
Decreased TV, loss of sighing breaths, and increase in RR occur
after abdominal and thoracic surgery
Residual effects of anesthesia itself and postoperative opioids
Inhibition of cough and impairment of mucociliary clearance
Lower abdominal surgery to a lesser degree.
Reductions in lung volumes are not seen with surgery on the
extremities
RISK FACTORS
PATIENT RELATED
• Age
• Chronic lung disease
• Asthma
• Smoking
• Obesity
• Obstructive sleep apnoea
• Pulmonary hypertension
• Heart failure
• General health status
SURGERY RELATED
• Surgical site
• Duration of surgery
• Type of anesthesia
• Type of neuromuscular blockade
PATIENT RELATED FACTORS
AGE
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? influence of age as an independent predictor of postoperative pulmonary complications
Early studies were not adjusted for overall health status or known pulmonary disease
ACP review made the novel observation that age >50 years was an important independent
predictor of risk
CHRONIC LUNG DISEASE
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Early reports estimated complications at relative risks between 2.7 and 6.0
A more recent systematic review, found the impact less than previously estimated
Among studies that used multivariable analysis to adjust for patient-related confounders, the
odds ratio 2.3614
There appears to be no prohibitive level of pulmonary function below which surgery is
absolutely contraindicated
Benefit of surgery must be weighed against the known risks
PATIENT RELATED FACTORS
ASTHMA
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Well controlled patients with peak flow of >80% of predicted or personal best can proceed
to surgery at average risk16
SMOKING
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Risk factor and has been demonstrated since 1944
Increased risk even among those without chronic lung disease
Relative risk 1.4 to 4.3
Risk declines only after eight weeks of preoperative cessation
Paradoxically, those who had stopped smoking less than eight weeks earlier had a higher risk
than current smokers17
OBESITY
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Obesity should not affect patient selection for otherwise high-risk procedures
PATIENT RELATED FACTORS
OBSTRUCTIVE SLEEP APNOEA
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While the literature is still emerging, we should consider OSA to be a probable risk factor
OSA increases the risk of critical respiratory events immediately after surgery, including early
hypoxemia and unplanned reintubation17
Patients with an ODI4% of >5 were more likely to have postoperative respiratory (8 versus
1%) complications
PULMONARY HYPERTENSION
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Increases pulmonary complication rates after surgery, regardless of the underlying etiology
History of pulmonary embolus
NYHA functional class ≥ 2
Intermediate or high risk surgery
Duration of anesthesia > 3 hours.
PATIENT RELATED FACTORS
HEART FAILURE
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Higher risk in HF than in COPD
Suggested by data from the ACP review, with odds ratio of 2.93 for HF patients and 2.36 for
patients with COPD14
The original Goldman cardiac risk index has been shown to predict postoperative pulmonary
as well as cardiac complications21
GENERAL HEALTH STATUS
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Functional dependence and impaired sensorium each increase risk
ASA classification correlates well with pulmonary risk and is one of the most important
predictors
Patients with significant preexisting lung disease would be classified in a higher ASA class
ASA class >2 confers a 4.87 fold increase in risk14.
The inability to exercise predicts 79% of pulmonary complications15.
PROCEDURE RELATED RISK FACTORS
SURGICAL SITE
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Single most important factor in predicting the overall risk of postoperative pulmonary
complications
Significantly higher for thoracic and upper abdominal surgery than for lower abdominal and
all other procedures
The impact of laparoscopic surgery on pulmonary complication rates is not well established
Lower pulmonary complication rates expected but not evaluated as an endpoint
DURATION OF SURGERY
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Surgical procedures lasting more than 3-4h are associated with a higher risk
A less ambitious, briefer procedure should be considered in a very high risk patient
PROCEDURE RELATED RISK FACTORS
TYPE OF ANESTHESIA
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Conflicting data with regard to spinal or epidural anesthesia vs general anesthesia
A comprehensive review was done and it appears likely that GA leads to a higher risk than do
epidural or spinal anesthesia
Further studies are required to confirm this observation
Regional nerve block is associated with lower risk and should be considered when possible
for high risk patients
TYPE OF NEUROMUSCULAR BLOCKADE
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Pancuronium, a long-acting neuromuscular blocker, leads to a higher incidence of
postoperative residual neuromuscular blockade
Higher incidence of postoperative pulmonary complications in those patients with residual
neuromuscular blockade
PREOPERATIVE CLINICAL EVALUATION
A careful history and physical examination are NB!
History of:
• Exercise intolerance
• Chronic cough
• Unexplained dyspnoea
The physical examination may identify findings suggestive of unrecognized pulmonary disease:
• Decreased breath sound
• Dullness to percussion
• Wheezes
• Rhonchi
• Prolonged expiratory phase
Which may predict an increase in the risk of pulmonary complications
PREOPERATIVE PULMONARY FUNCTION TESTING
• The value of routine preoperative pulmonary function testing
remains controversial
• There is consensus that all candidates for lung resection
should undergo preoperative pulmonary function testing.
• Such testing should be performed selectively in patients
undergoing other surgical procedures
LUNG RESECTION
INITIAL EVALUATION
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Detailed medical history, incl. coexisting disease to ensure the optimal treatment of
that disease
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History should include functional capacity and the degree of limitation of activity.
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A history of smoking or COPD may lead to preoperative therapeutic interventions such
as bronchodilators and/or steroids
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The physical examination should include an evaluation for signs of metastatic spread
and the presence of HF and PHT
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All of these might change the treatment mode and determine that the patient may
not be a suitable surgical candidate.
PULMONARY SPECIFIC EVALUATION
STAGE I ASSESSMENT
Spirometry
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Spirometry is a simple, inexpensive, standardized and readily available test
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FEV1, FVC, FEF mid expiratory phase (FEF25-75%) and MVV have been extensively studied
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FVC reflects lung volume, while FEV1 and FEF25-75% reflects airflow
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MVV reflects muscle strength and correlates with postoperative morbidity
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FEV1 is regarded as being the best for predicting complications of lung resection in the initial assessment
Diffusion Capacity
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DLCO reflects alveolar membrane integrity and pulmonary capillary blood flow in the patient’s lungs
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Retrospective studies have reported that actual DLCO (as % of the predicted value) and predicted
postoperative DLCO are important predictors of mortality and postoperative complications
Arterial Blood Gas Levels
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Arterial blood gas levels have not been extensively studied as predictor of postoperative complications
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Hypercapnia (PCO2 >45 mmHg) in arterial blood has been a relative contraindication to lung resection
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A few studies however did not find that a PCO2 > 45mmHg was predictive of postoperative complications
PULMONARY SPECIFIC EVALUATION
INCREASED POSTOPERATIVE COMPLICATIONS AND MORTALITY
For pneumonectomy:
FEV1
MVV
DLCO
FEF25-75%
< 2L or < 60% of predicted
< 55% of predicted
< 50% of predicted
< 1.6L/s
For lobectomy:
FEV
MVV
DLCO
FEF25-75%
< 1L
< 40% of predicted
< 50% of predicted
< 0.6L/s
For wedge resection :
FEV1
DLCO
< 0.6L
< 50% of predicted
If values more than required for pneumonectomy above are achieved, no further testing is
indicated and that the patient is at low risk
Datta, D, Lahiri, B. Preoperative evaluation of patients undergoing lung resection surgery. Chest 2003; 123:2096.
PULMONARY SPECIFIC EVALUATION
STAGE II ASSESSMENT
Quantitative ventilation-perfusion scan or Differential lung scan
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The percentage of radioactivity contributed by each lung correlates with the contribution to the function
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Normally the right lung contributes 55% and the left lung 45% of lung function.
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The predicted FEV1 of residual lung following surgery can be calculated
Patients, who undergo a differential lung scan may be allowed to undergo surgery if:
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Predicted postoperative FEV1
> 40% of predicted
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Predicted postoperative DLCO > 40% of predicted
Patients whom do not meet these criteria should undergo further evaluation before surgery can be undertaken
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Patients with a predicted postoperative FEV1 <30 percent predicted are particularly singled out
Other tests assessing differential lung function include
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Bronchospirometry,
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lateral position testing and
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total unilateral pulmonary artery occlusion (invasive, special equipment, technical expertise
PULMONARY SPECIFIC EVALUATION
STAGE III ASSESSMENT
Exercise testing stresses the entire cardiopulmonary and oxygen delivery system
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Good estimate of cardiopulmonary reserve
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HR, BP, ECG and O2 saturation are measured, as well as the measurement of exhaled gasses.
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The VO2; VO2max; carbon dioxide output and minute ventilation can be measured
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VO2max or peak VO2 indicates whether the patient has the reserve to counter the multiple physiologic
stresses that accompany surgery
Two major types of exercise tests have been used
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Fixed exercise challenge, in which a sustained level of work is performed
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Incremental exercise testing in which the work is sequentially increased to a desired end point
Stair climbing: For many years, surgeons have utilized stair climbing as a preoperative screening tool. Though
poorly standardized, this form of testing has been shown to identify patients at increased risk for lung
resection.
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Attainment of a lower altitude (less than 12m) on a symptom-limited stair climbing test was associated
with increased cardiopulmonary complications, mortality, and cost, compared with climbing to a higher
altitude (22m)
Those who were able to climb > 8 flights of stairs, at their own pace, were less likely to experience
complications than those who could climb < 7 flights of stairs
Patients who climbed between 7-8 flights of stairs had an intermediate risk of complications (30%)
PULMONARY SPECIFIC EVALUATION
Integrated cardiopulmonary exercise testing:
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The most important measurement during cardiopulmonary exercise testing that correlates with
postoperative complications is the level of work achieved
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Measured by VO2max
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An early report demonstrated no mortality in patients able to achieve a VO2max in excess of 1 L/min,
compared with 75 percent mortality in those with a VO2max below 1 L/min31.
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Expressing VO2max in terms of mL/kg per min, which takes into account the patient's body mass, may
increase the predictive power of the test
Current guidelines from the ACCP considers patients with:
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VO2max <10 mL/kg per min
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VO2max <15 mL/kg per min predicted postoperative FEV1 and DLCO <40% predicted, to be at high risk for
perioperative death and cardiopulmonary complications
6 min walk test
OTHER SURGERY
PULMONARY FUNCTION TESTING
There is considerable debate regarding the role of preoperative pulmonary function testing for risk
stratification
Two reasonable goals that could potentially justify the use of preoperative PFTs:
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ID of a group of patients for whom the risk of the proposed surgery is not justified by the benefit
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ID of a subset of patients at higher risk for whom aggressive perioperative management is warranted
Bedside spirometry is widely available, and measures of the forced expiratory volume in one second (FEV1) and
forced vital capacity (FVC) have been frequently reported.
Increased risk:
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FEV1
<70 % predicted
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FVC
<70 % predicted
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FEV1/FVC ratio
<65 %
There is little support from the literature that any of these goals is routinely met other than for lung resection
surgery
Other factors conferred higher odds ratios for pulmonary complications than did abnormal spirometry
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ASA class >3 and chronic mucous hypersecretion.
OTHER SURGERY
RECOMMENDATION:
Based on a systematic review, a 2006 American College of Physicians
guideline recommends that clinicians not use preoperative spirometry
routinely for predicting the risk of postoperative pulmonary complications
A reasonable approach to patient selection for preoperative pulmonary
function testing follows:
• Obtain PFTs for patients with COPD or asthma if clinical evaluation cannot
determine if the patient is at their best baseline and that airflow
obstruction is optimally reduced
• Obtain PFTs for patients with dyspnea or exercise intolerance that remains
unexplained after clinical evaluation
• PFTs should not be used as the primary factor to deny surgery
• PFTs should not be ordered routinely prior to abdominal surgery or other
high risk surgeries
OTHER SURGERY
ARTERIAL BLOOD GAS ANALYSIS
• No data suggest that the finding of PCO2 >45mmHg identifies high-risk
patients who would not have otherwise been identified based upon
established clinical risk factors
• The risk associated with this degree of PaCO2 elevation is not necessarily
prohibitive, although it should lead to a reassessment of the indication
• Hypoxemia has generally not been identified as a significant independent
predictor of complications after adjustment for potential confounders.
• Current data do not support the use of preoperative arterial blood gas
analyses to stratify risk for postoperative pulmonary complications
EXERCISE TESTING
• There are no data to support its routine use in the evaluation of patients
prior to general surgery.
OTHER SURGERY
CHEST RADIOGRAPHS
• Abnormal CXR are seen with increasing frequency with age
• CXR add little to the clinical evaluation in identifying healthy patients at risk
As an example, one study screened 905 surgical admissions for the presence of clinical factors that were
thought to be risk factors for an abnormal preoperative CXR
• No risk factors in 368 patients; of these, only one (0.3%) had an abnormal CXR, which did not affect
the surgery
• 504 patients had identifiable risk factors; of these, 114 (22%) had significant abnormalities on
preoperative CXR
A meta-analysis of studies of routine preoperative CXR
• Of 14,390 preoperative x-rays, there were only 140 unexpected abnormalities and only 14 cases
where the chest x-ray was abnormal and influenced management.
The available literature does not allow an evidence-based determination of which patient will benefit
from a preoperative CXR however, it is reasonable to obtain preoperative CXR:
• in patients with known cardiopulmonary disease and in
• those over age 50 years undergoing high risk surgical procedures, including upper abdominal,
aortic, esophageal, and thoracic surgery.
PULMONARY RISK INDICES
CARDIOPULMONARY RISK INDEX
A combined CPRI was proposed based upon the Goldman
criteria for cardiac risk, adding:
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Obesity (BMI >27 kg/m2)
Cigarette smoking within eight weeks of surgery
Productive cough within five days of surgery
Diffuse wheezing or rhonchi within five days of surgery
FEV1/FVC <70%
PaCO2
>45 mmHg
Results of this scoring system have been mixed
Limitation of this index is the requirement for PFT and ABG
PULMONARY RISK INDICES
BROOKS-BRUNN RISK INDEX
A different set of proposed criteria for a risk index
Six factors were independently associated with increased pulmonary
risk after abdominal surgery:
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Age >60
Obesity (BMI >27 kg/m2)
Impaired cognitive function
History of cancer
Smoking history in past eight weeks
Upper abdominal incision
In a subsequent validation cohort by the same author, the original model validated
relatively well, but other factors emerged as significant
PULMONARY RISK INDICES
MULTIFACTORIAL RISK INDEX FOR POSTOPERATIVE RESPIRATORY FAILURE
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Investigators have more recently published the most ambitious multifactorial risk index to predict
postoperative respiratory failure
This index is modelled after the widely used cardiac risk indices
Procedure-related risk factors dominate the index with type of surgery and emergency
surgery being the most important predictors
New observations in this study included the importance of:
• Abdominal aortic aneurysm repair
• Emergency surgery
• Metabolic factors
as risk factors
• Investigators have also reported a similar index to predict postoperative pneumonia.
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These indices significantly advance the field of preoperative pulmonary risk assessment
They rely upon readily available clinical information
A limitation is that most of the factors are not modifiable.
SUMMARY
Postoperative pulmonary complications are an important source of
perioperative morbidity and mortality
A careful history and physical examination are the most important
tools for preoperative risk assessment in evaluating patients for
potential postoperative pulmonary complications
No role for preoperative ABG analyses to identify high risk patients or
to deny surgery
CXR should be obtained in patients undergoing high risk surgery who
are > 50 years, or if cardiac or pulmonary disease is suggested by
the clinical evaluation
PFT should be reserved for patients with uncharacterized dyspnea or
exercise intolerance and for those with COPD or asthma where
clinical evaluation cannot determine if airflow obstruction has been
optimally reduced
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