PREAMBLE
Preoperative investigations are essential for planning, stratification, optimisation and perioperative management of patients undergoing surgical procedures and to improve patient outcomes. However, preoperative investigation practices are not uniform despite published guidelines from professional bodies across the globe, due to various factors including socio-economic, demographic and medico-legal considerations.[123456789] The practices prevalent in the Indian subcontinent involve ordering from minimal needed to battery of investigations.[13710111213] With the advent of auto analysers, the practice of ordering of battery of investigations has become more prevalent. Often, many of these investigations may not influence the perioperative management and outcomes.[3121415] With widespread availability of ultrasound, more anaesthesiologists are getting trained in the perioperative use of ultrasound. Exploring the utility of ultrasound for predicting possible difficult airway, therefore, was also considered. There are no available guidelines on the time frame of the validity of previous investigation reports (Validity Time for Previous Investigations - VTPIN), when a patient is scheduled for surgery. Taking these considerations into account, the Indian Society of Anaesthesiologists (ISA) endeavoured to formulate evidence-based practice guidelines for preoperative investigations. The guidelines are prepared to promote judicious ordering of preoperative investigations, with focus on the perioperative management strategies. The guidelines are expected to aid in better patient outcomes considering the geographic, demographic, socio-economic and medico-legal aspects.
Uniform ordering of investigations will not be appropriate in all surgical populations. The investigations ordered depend upon the type and urgency of surgery (elective, semi-elective, emergency), patient’s current physiological status, associated co-morbidities and the medications. The ordering of preoperative investigations also considers the complexity of the surgery as categorised, for example by the National Institute of Clinical Excellence (NICE) based on invasiveness of the surgery as minor, intermediate and major or complex surgery.[4] The ordering of the investigations needs to be individualised in patients scheduled for emergency surgery, specialised surgical interventions (such as cardiothoracic, vascular, neurological, transplant surgery) and in those with severe systemic disease.
Separate guidelines are required to address paediatric, obstetric and bariatric population as they have specific pathophysiological considerations.
Hence, the practice guidelines from the ISA on preoperative investigations are aimed at patients with American Society of Anesthesiologists physical status (ASA PS) 1 and 2, scheduled for elective surgery.
These guidelines should not be substituted for good clinical judgement (based on detailed history, clinical evaluation and review of medications) and the attending anaesthesiologist may consider individualising the decision on further investigations.
Tests for viral markers including coronavirus disease 2019 (COVID-19) are ‘screening modalities’ and are not considered for formulating the current guidelines. The ordering of preoperative investigations may have been by an anaesthesiologist not attending to the management of the patient on the day of the surgery and it is imperative on the attending anaesthesiologist to review the reports rationally and proceed with anaesthetic management.
Focus of the guidelines
These clinical practice guidelines provide recommendations for routine preoperative investigations in ASA PS 1 and 2 patients scheduled for elective surgical procedures. The guidelines also focus on the validity in terms of time frames for previously performed investigations when the patient is scheduled for a surgical procedure.
The normal range of laboratory tests is derived from samples collected from apparently healthy persons and subjecting their results to statistical tests to determine the mean and range of the values. A 95% confidence interval refers to the probability that the laboratory test reports conducted on healthy persons will fall within this predefined range, 95% of the times. In other words, it also means that there is a 5% probability of a healthy person’s report falling outside this defined range.[16] False positive reports can contribute to unnecessary delay, referral, and further evaluation.[7] Detailed history and clinical evaluation should therefore, precede ordering preoperative investigations.
METHODOLOGY
The proposal from SBB for formulating the practice guidelines for preoperative investigations was approved by the general body of the ISA. The Core Committee (CC) consisting of the President and Secretary, ISA along with 7 other members (SBB, HSS, PD, RG, SK, UG, ZA) was constituted. An expert group consisting of 17 members with academic standing in the speciality spread across India and a biostatistician, was formed to assist the CC in formulation of the guidelines.
For the purpose of these guidelines, routine preoperative investigations are defined as those tests which may influence the perioperative anaesthetic management and outcome in patients scheduled for elective surgeries independent of the specific clinical condition.
For the current guidelines, expert consensus was sought to categorise common elective surgical procedures, based on the invasiveness and duration of surgery. The CC prepared a list of commonly performed surgical procedures and conducted an anonymous survey among the expert group using Google form. The experts were asked to categorise each elective surgical procedure as minor, intermediate or major. Their responses were collected, tabulated and as per the consensus (defined as agreement of ≥75%), the surgical procedures were categorised into appropriate sections [Table 1].
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Table 1: Examples for categorisation of surgical procedures based on invasiveness and duration of surgery
The CC performed review of literature, identified the major aspects related to the topic and framed 10 preliminary research questions (RQs) based on population, intervention, comparator and outcomes (PICO). Each RQ was allotted to a focused group of two to three experts and dedicated virtual meetings were held subsequently to refine and finalise the RQs. Subsequently, each of these expert groups performed further review of published evidences and discussed with the CC.
A literature search was conducted for relevant full-text articles in the English language published between 01 January 2010 and 25 November 2021. The search was conducted with compatible keyword combinations in online databases PubMed, Embase, Google Scholar and Cochrane Library [Table 2]. All studies with patient population scheduled for elective non-speciality surgery were included provided the study population consisted of either ASA PS 1 and/or 2. Studies where ASA PS 3 patients constituted <5% of the total study population or where the population included ASA PS 1, 2 and higher but categorisation of data and outcomes was available separately for ASA PS 1 and 2 patients, were also included [Table 3].
Table 2: Search strategies for published evidence
Table 3: Inclusion and exclusion criteria
Meta-analyses and systematic reviews published after January 2010 were reviewed for references for relevant studies. Furthermore, bibliography of each identified study was scanned for additional relevant references. Those studies that assessed the cost impact as the only outcome or did not mention the ASA grading of the study population were excluded. Published guidelines, narrative reviews, editorials, opinions and correspondence articles were excluded though they were scanned for relevant references.
The CC reviewed each searched original research article for its relevance for inclusion in systematic review. As part of the evidence collection and analysis process, randomised controlled trials, cohort studies, cross-sectional studies and case control studies were considered suitable for the systematic review. Each individual group of experts tabulated the important data from the collected evidence. Systematic review of included studies was conducted and feasibility of meta-analysis of the same was explored. Where there was lack of data/missing information in the articles, the corresponding authors were contacted through e-mail to seek raw data. Quality of evidence based on the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach was ascertained and appropriate certainty level (High, Moderate, Low or Very Low) was provided for each article and for the systematic review.[17] If the certainty level of evidence was graded as very low or low, a ‘weak’ recommendation was made, and a ‘strong’ recommendation was made if the certainty level of evidence was graded as high or moderate.
A three-step Delphi methodology was followed to arrive at consensus on the recommendations[18] [Figure 1]. Prior to round one of Delphi, the CC prepared draft recommendations for each RQ along with evidence summary tables containing data of all the studies included for the systematic review [Tables 4 and 5].
Figure 1: The three-step Delphi method
Table 4: Evidence summary for complete blood count, renal function, liver function, serum electrolytes, coagulation profile, blood glucose, 12-lead electrocardiogram, chest X-ray
Table 5: Evidence summary for preoperative sonographic airway assessment to predict difficult laryngoscopy
Round One: RQs along with the draft recommendations and the collected evidences were sent by e-mail (via anonymous Google Survey Form) to each of the 16 subject experts. They were asked to provide responses as ‘accept’ or ‘reject’ or ‘review’ for all the draft recommendations. When review was opted, experts were to comment if any clarification or modification was required. The completed responses from the experts were returned to the CC. Affirmation as ‘accept’ or ‘reject’ for each draft recommendation by 75% or more experts was considered as a consensus. If the affirmation to accept or reject was less than 75% and if ‘review’ option was opted for, those recommendations were revised as per the suggestions.
Round Two: The revised draft recommendations along with the summary of expert opinions from round 1 were circulated by e-mail (via anonymous Google Survey Form) to each expert for the second round to seek a consensus. Similar methodology as per round 1 was followed.
Round Three: This was an open virtual meeting of all experts along with the CC where consensus was reached for the unresolved draft recommendations through ‘show of hands’ and active deliberations. These were suitably redrafted as per the suggestions from the experts. After reaching consensus, the recommendations were made final.
Overall, from conception to the formulation of guidelines, the CC held 2 physical meetings and 63 virtual meetings among themselves and 48 virtual meetings with the experts.
The summary of the final recommendations [Table 6] was presented to the Governing Council and General Body of ISA and was formally approved.
Table 6: Practice Guidelines from the Indian Society of Anaesthesiologists on preoperative investigations
To know the prevailing practice patterns of ordering the preoperative investigations among Indian anaesthesiologists, the CC prepared a structured questionnaire for the survey which was subsequently validated by independent experts. This questionnaire was circulated among the 5838 delegates of the national conference of ISA conducted from 25 to 28 November, 2021.
GUIDELINES AND RECOMMENDATIONS
Complete blood count
In ASA PS 1 and 2 patients scheduled to undergo elective surgery, will routine preoperative complete blood count testing change anaesthetic management or patient outcomes after surgery?
Literature review regarding complete blood count (CBC) revealed that some of the available studies had tested individual components of CBC, that is, haemoglobin or haematocrit, total and differential leukocyte count and platelet count, while others had tested CBC as a whole.[3111213192021222324]
Anaemia is a global health issue with a prevalence rate of approximately 14% in ASA PS 1 and 2 preoperative patients.[3111213192021222324252627] This can contribute to adverse events such as tachycardia, arrhythmias, increased risk of infection, heart failure in the perioperative period. It can also contribute to increased duration of hospital stay, rates of intensive care admission and blood transfusion, which carry their own associated risks.
Few of the studies have used haemoglobin as the parameter reflective of anaemia while few have used haematocrit. For the purpose of current guidelines, ‘haemoglobin’ is uniformly used as the investigation parameter. Nine studies (n = 27697) tested the effects of preoperative haemoglobin/haematocrit on immediate perioperative outcomes [Table 4].[31112131920212223] Most studies included combinations of minor, intermediate and major surgeries. Review of evidence indicates the need for haemoglobin testing preoperatively in patients scheduled for intermediate to major surgeries. However, evidence was equivocal regarding minor surgeries. There was no evidence on outcomes related to increased haemoglobin levels.[20]
Both leukocytosis and leukopenia can potentially contribute to adverse outcomes in the perioperative period. Among four studies that tested TLC (n = 25817),[11121320] leukocytosis was associated with adverse outcomes in patients undergoing intermediate and major surgeries. However, leukopenia did not influence the perioperative outcomes.[20] [Table 4].
The abnormal platelet counts may influence the perioperative management strategies and outcomes. Low platelet counts may have adverse implications for both central neuraxial and peripheral nerve blocks. Three studies (n = 24617) reported no influence on the perioperative outcome with platelet count <1.5 x 106/mm3.[111220] Increased platelet counts also can have adverse implications related to thrombotic mechanism. Three studies (n = 24617) reported no influence on the perioperative outcome with platelet count >4.5 x 106/mm3 [Table 4].[111220] However, extreme levels of platelet count in these patients were not reported. Identifying the lowest and highest levels of platelet counts with respect to uneventful perioperative outcomes could be the focus of future research.
When central or peripheral nerve blocks are planned, the practitioner is advised to refer to the latest guidelines on regional anaesthesia and anticoagulation. The guidelines related to the influence of various drugs from the alternative systems of medicine which may have effect on platelet count or functioning needs to be considered.[28]
Regarding CBC testing, two studies (n = 153) involving minor and intermediate surgeries did not report any adverse outcomes.[2329] Among those with abnormal CBC, in three studies (n = 1444) involving minor, intermediate and major surgeries, 131 patients required further investigations, delay, or referral, 7 patients required postponement of the scheduled surgical procedure or change in management approach and 12 patients required blood or blood product transfusion[32430] [Table 4].
The evidence was favouring CBC for intermediate and major surgeries when individual component data was taken together with CBC. Based on the existing evidence and practices among anaesthesiologists and the hospital set ups, it was suggested by the experts that preoperative CBC would be of high utility with respect to management and outcomes for minor surgeries also.
Online survey conducted as a part of this guideline formulation showed that of the total 1169 survey respondents, majority (n = 753) were in favour of ordering CBC as a preoperative investigation rather than individual components. Majority of the respondents, that is, 998, 1052, 1169 also practiced ordering CBC prior to minor, intermediate and major surgeries respectively [Supplementary Appendix 1, available online].
SUPPLEMENTARY APPENDIX 1
Recommendation 1: Preoperative complete blood count testing is suggested for patients undergoing minor, intermediate and major surgery
Renal function tests
In ASA PS 1 and 2 patients scheduled to undergo elective surgery, will routine preoperative renal function testing change anaesthetic management or patient outcomes after surgery?
Among the renal function tests, serum creatinine is more specific than blood urea and even the estimated glomerular filtration rate (eGFR) calculation is based on the serum creatinine value and hence serum creatinine was considered as the main parameter, changes in which may influence the outcome.
Out of the 11 available studies [Table 4],[311121320212324293031] 9 studies estimated serum creatinine.[31112132021243031] Two studies involving intermediate surgeries (n = 21165) and one study (n = 670) involving intermediate and major surgeries showed abnormal creatinine to have no influence on outcomes.[112023] Six studies (n = 3547) involving all three surgery categories, showed adverse outcomes in 18 patients having high preoperative serum creatinine levels.[31213243031] Two studies involving minor and intermediate surgeries that tested blood urea only (n = 153) did not report any adverse outcomes[2329] [Table 4].
Hypoxaemia, haemodynamic instability, direct organ handling, technique and duration of the procedures are some of the factors which can contribute to acute kidney injury in the perioperative period in intermediate and major surgeries.[3233] The consensus among the experts was in favour of ordering preoperative serum creatinine before intermediate and major surgeries to guide the patient management.
Online survey conducted as a part of this guideline formulation showed that of the total 1169 survey respondents, 474, 771 and 1112 respondents preferred to get preoperative RFT in minor, intermediate and major surgeries, respectively [Supplementary Appendix 1, available online].
Recommendation 2a: Preoperative serum creatinine estimation is NOT suggested for patients undergoing minor surgery.
Recommendation 2b: Preoperative serum creatinine estimation is suggested for patients undergoing intermediate and major surgery.
Serum electrolytes
In ASA PS 1 and 2 patients scheduled to undergo elective surgery, will routine preoperative serum electrolytes (Na, K) testing change anaesthetic management or patient outcomes after surgery?
Alterations in serum sodium and serum potassium may be associated with medical and surgical disorders, drug intake and have a potential to affect the anaesthetic management and the outcomes.[34353637] One study involving intermediate surgeries (n = 20915),[20] and two studies involving minor and intermediate surgeries (n = 765) did not report any adverse outcomes related to deranged serum electrolytes.[2123] Three studies involving all three categories of surgeries (n = 608), showed influence on outcomes in five patients with deranged serum sodium.[132430] Evidence with outcomes related to altered serum potassium independently were not available [Table 4].
Online survey conducted as a part of this guideline formulation showed that of the total 1169 survey respondents, 233, 453, 1040 respondents preferred to get preoperative serum electrolytes in minor, intermediate and major surgeries, respectively [Supplementary Appendix 1, available online].
Recommendation 3: Preoperative serum sodium and potassium estimation is NOT suggested for patients undergoing minor, intermediate and major surgery.
Liver function tests
In ASA PS 1 and 2 patients scheduled to undergo elective surgery, will routine preoperative liver function testing change anaesthetic management or patient outcomes after surgery?
Liver function tests (serum albumin, serum bilirubin, alanine aminotransferase (ALT), aspartate aminotransferase (AST) and alkaline phosphatase) assess the synthetic and metabolic functions of the liver (PT/INR is a sensitive marker for synthetic function of the liver; it is addressed under coagulation profile as a separate parameter). Low albumin levels have been reported to be independent predictors of the perioperative outcomes.[3839]
On evidence review, six relevant studies (n = 18338)[31120232930] for preoperative liver function tests (LFT) were identified of which four studies conducted on patients undergoing minor and/or intermediate surgery (n = 17806) did not show any influence of LFT on outcomes.[11202329] In two studies involving patients scheduled for minor, intermediate and major surgeries (n = 532), among patients who had altered preoperative LFT, 21 patients required further investigations, referral or delay, while three patients required blood transfusion.[330] Individual components of LFT did not have any adverse impact on the outcomes as reported in a study conducted on patients undergoing intermediate surgeries (n = 17450)[20] [Table 4].
Online survey conducted as a part of this guideline formulation showed that of the total 1169 survey respondents, 106, 300 and 904 respondents preferred to get preoperative LFT in minor, intermediate and major surgeries, respectively [Supplementary Appendix 1, available online].
Recommendation 4a: Preoperative liver function testing is NOT suggested for patients undergoing minor and intermediate surgery
Recommendation 4b: Preoperative liver function testing is suggested for patients undergoing major surgery
Coagulation profile
In ASA PS 1 and 2 patients scheduled to undergo elective surgery, will routine preoperative coagulation profile (Prothrombin Time/International Normalised Ratio, activated Partial Thromboplastin Time) testing change anaesthetic management or patient outcomes after surgery?
Abnormalities in preoperative coagulation tests (PT/INR, aPTT) may influence the perioperative management strategy.[404142]
One study involving intermediate surgeries (n = 15643),[20] two studies involving minor and intermediate surgeries (n = 55),[2329] and one study involving intermediate and major surgeries (n = 670),[21] did not report adverse outcomes related to abnormal coagulation profile. In three studies involving all three categories of surgeries (n = 1446),[132430] change in approach or change in management plan was observed in 11 patients with abnormal preoperative coagulation reports [Table 4].
When regional techniques are planned in patients on anticoagulants, the practitioner is advised to refer to the latest guidelines on regional anaesthesia and anticoagulation. The guidelines related to the influence of various drugs from the alternative systems of medicine which may have effect on coagulation needs to be considered.[28]
Online survey conducted as a part of this guideline formulation showed that, of the total 1169 survey respondents, 460, 811 and 1056 respondents preferred to get preoperative coagulation profile in minor, intermediate and major surgeries, respectively [Supplementary Appendix 1, available online].
Recommendation 5: Preoperative coagulation profile (PT/INR and aPTT) testing is NOT suggested for patients undergoing minor, intermediate and major surgery.
Blood glucose
In ASA PS 1 and 2 non-diabetic patients scheduled to undergo elective surgery, will routine preoperative blood glucose estimation change anaesthetic management or patient outcomes after surgery?
Patients are considered as non-diabetic if during preanaesthetic evaluation, there is no history, finding or previous investigation report suggestive of diabetes mellitus. In such patients, role of preoperative blood glucose estimation on perioperative outcomes needs to be evaluated. In one study involving intermediate surgeries (n = 500), no patient had abnormal blood glucose.[11] In five studies involving all three categories of surgeries (n = 2894), amongst patients with elevated blood glucose preoperatively, eight required referral and six needed a ‘change in approach’[312132430] [Table 4].
Detection of single increased blood glucose level during preoperative investigation in patients without diabetes mellitus and its potential influence on major outcomes such as cancellation, infection in the cited evidences were considered by the experts, followed by further deliberations before arriving at the recommendation.
Online survey conducted as a part of this guideline formulation showed that of the total 1169 survey respondents, 748, 863 and 1083 respondents preferred to get preoperative blood glucose estimation in minor, intermediate and major surgeries, respectively [Supplementary Appendix 1, available online].
Recommendation 6: In non-diabetic patients, pre operative blood glucose estimation is NOT suggested when scheduled to undergo minor, intermediate and major surgery.
12-lead electrocardiogram
In ASA PS 1 and 2 non-cardiac patients scheduled to undergo elective surgery, will routine preoperative 12-lead electrocardiogram testing change anaesthetic management or patient outcomes after surgery?
Preoperative 12-lead electrocardiogram testing can detect pre-existent or ongoing myocardial ischaemic changes, endocardial or pericardial pathology and may also reflect electrolyte disorders and underlying co-morbidities.[31112] One study involving intermediate surgeries (n = 420) reported no adverse outcome in patients with ECG changes.[11] Four studies involving all three categories of surgeries (n = 2436) reported ECG changes resulting in minor impact (further investigation, referral or delay) in 58 patients and a change in approach in 3 patients. One patient required postponement of the surgical procedure due to new onset ECG changes in the operating room[3121324] [Table 4].
Non-cardiac status of a patient is reflected by the absence of history, clinical findings or reports suggestive of cardiovascular disease. The incidence of cardiovascular diseases increases with age.[4344] The cardiovascular disease death rate in India is much higher than the global average.[4546] When patients at risk as per these evidences (by age) present for incidental surgery, cardiac events are more likely to be encountered in the perioperative period.[47] Published evidence along with this information was considered and deliberated by the experts before arriving at the recommendations.
Online survey conducted as a part of this guideline formulation showed that of the total 1169 survey respondents, 609, 834 and 1110 respondents preferred to get preoperative 12-lead ECG test in minor, intermediate and major surgeries, respectively. Majority (932/1169) of the ISA members were in favour of designating an age criterion for routine preoperative ECG testing. Among these 932 respondents, majority (n = 837) were in favour of ECG testing at 45 years of age and above [Supplementary Appendix 1, available online].
Recommendation 7a: In non-cardiac patients, pre operative 12-lead electrocardiogram testing is suggested at age 45 years and above, when scheduled to undergo minor and intermediate surgery.
Recommendation 7b: Preoperative 12-lead electro cardiogram testing is suggested for all patients undergoing major surgery.
Chest X-ray
In ASA PS 1 and 2 patients scheduled to undergo elective surgery, will routine preoperative chest X-ray testing change anaesthetic management or patient outcomes after surgery?
Preoperative chest X-ray findings have the potential to influence the perioperative management but the utility of this investigation needs to be considered in view of the radiation hazards. In one study involving intermediate surgeries (n = 470), 10 patients with abnormal preoperative chest X-ray findings developed mild intraoperative bronchospasm.[11] In 4 studies involving all 3 categories of surgeries (n = 2162), among those with abnormal preoperative chest X-ray findings, minor impact (further investigations, referral or delay in starting the procedure) was observed in 21 patients and a change in management required in 9 patients[3121324] [Table 4].
Some of the radiographic changes may not be of relevance such as those indicative of older pathology (tuberculosis, obstructive and restrictive lung diseases). The chest imaging can also reveal certain cardiovascular and pulmonary changes attributable to the impact of smoking, pollution or cardiac disorder and tend to have cumulative effect with increasing age. Minor radiographic changes observed in younger individuals may not impact the perioperative management.[48] These factors along with the evidences were collectively considered and deliberated by the experts during Delphi consensus, prior to arriving at the recommendations.
Online survey conducted as a part of this guideline formulation showed that of the total 1169 survey respondents, 319, 602 and 982 respondents preferred to get preoperative chest X-ray testing in minor, intermediate and major surgeries, respectively. Approximately 51% (598/1169) of the respondents to the online survey were in favour of age based routine chest X-ray testing in patients scheduled for surgery. Though majority (n = 561), were in favour of routine chest X-ray testing in patients aged 45 years and above, 239 among them were in favour of testing at patient age at or above 60 years [Supplementary Appendix 1, available online].
Recommendation 8a: Preoperative chest X-ray testing is NOT suggested for patients undergoing minor surgery.
Recommendation 8b: Preoperative chest X-ray testing is suggested for patients aged 50 years and above, undergoing intermediate and major surgery
Airway
In ASA PS 1 and 2 patients scheduled to undergo elective surgery, will routine preoperative ultrasonographic airway assessment predict difficult airway?
Increasing accessibility of ultrasonogram (USG) for the anaesthesiologists has enabled its utility for preoperative airway assessment. Preliminary data suggests that USG would be one of the important preoperative airway assessment tools. Airway ultrasonography could predict difficult laryngoscopy more reliably than the clinical parameters in 20 out of the 22 studies[49505152535455565758596061626364656667686970] [Table 5]. These studies had used varied USG parameters as predictors of difficult airway. With the available evidences, a specific parameter or a combination of parameters to predict a difficult airway cannot be suggested. Since airway ultrasound is an evolving field, further research may be able to conclusively demonstrate the USG parameters that have high sensitivity and specificity for predicting difficult laryngoscopy.
Recommendation 9: Routine preoperative ultra sonographic airway assessment is NOT suggested for predicting difficult laryngoscopy.
Validity time for previous investigations (VTPIN)
In ASA PS 1 and 2 patients scheduled to undergo elective surgery, what is the validity time for previous investigations provided the patient’s underlying condition remains stable in the intervening period?
The Validity Time for Previous Investigations (VTPIN) refers to the acceptable interval from the time of previous testing for any purpose, to current preoperative evaluation.
One study (n = 235010) concluded that normal blood test reports (CBC, LFT, RFT, serum sodium, and coagulation profile (PT/INR, aPTT) obtained within the last 2 months from the date of surgery did not differ significantly in their influence on the outcomes studied compared to those which were performed within 1 or 2 weeks prior to surgery.[71] A retrospective cohort study (n = 932)[72] considered the preoperative test reports (CBC, blood glucose, RFT, coagulation tests, ECG and chest x-ray) obtained for the first surgical procedure and compared with the test reports obtained for re-interventions (6-84 months interval). The preoperative test reports obtained for second surgery performed 12 months after the first intervention, remained largely unaltered and minor alterations did not have any influence on the outcomes.
Recommendation 10a: The acceptable validity time (VTPIN) for a previously performed normal complete blood count, renal function tests, liver function tests, coagulation profile, is suggested to be 2 months provided the clinical condition of the patient has not changed in the intervening period.
Recommendation 10b: The acceptable validity time (VTPIN) for a previously performed normal 12-lead electrocardiogram and chest X-ray, is suggested to be 12 months provided the clinical condition of the patient has not changed in the intervening period.
Limitations and evidence updates
Non-availability of randomised controlled trials and inadequacy of data in the available studies (definitions, outcomes, follow-up, testing pattern, etc.) were major limitations for performing the meta-analysis. The certainty level for the available literature was low or very low and hence the recommendations formulated for all the RQs are weak.
After the formulation of the final recommendations, the core committee reviewed additional publications satisfying the original search strategy (25 November 2021 till 03 May 2022). In one study (n = 170, age 15-45 years), majority of the patients were routinely tested for CBC, RFT, serum electrolytes, blood glucose, 12-lead electrocardiogram and chest X-ray. In those patients where reports were abnormal, there was no influence on the outcomes. The categorisation of patients in terms of the nature of surgery was not available.[73] Four studies (n = 2700) concluded preoperative ultrasonographic airway assessment to be a better assessment tool for predicting difficult laryngoscopy compared to routinely used clinical parameters.[74757677]
One study (n = 150, 18-60 years) concluded that preoperative ultrasonographic airway assessment was not superior to clinical evaluation in predicting difficult laryngoscopy.[78] The outcomes from these additional evidences were in agreement with the formulated recommendations. Hence, these guidelines stand valid with the latest evidence.
A ready reckoner is recommended to be downloaded for display for educational and clinical purposes (eg, in pre-anaesthesia check-up clinics, wards and other areas) [Supplementary Appendix 2, available online].
SUPPLEMENTARY APPENDIX 2
The seven members of the core committee: SBB – S Bala Bhaskar, HSS – Harsoor SS, PD – Pradeep A Dongare, RG – Rakesh Garg, SK – Sudheesh Kannan, UG – Umesh Goneppanavar, ZA – Zulfiqar Ali.
Financial support and sponsorship
This guidelines project is fully supported and sponsored by the Indian Society of Anaesthesiologists
Conflicts of interest
There are no conflicts of interest.
Acknowledgements
The authors gratefully acknowledge the external reviewer, Dr Sumesh Arora, Senior Staff Specialist, Prince of Wales Hospital, Australia for insightful comments on the manuscript. Authors express deep appreciation for the following for their help in validating the contents of the ISA Preoperative Investigations Survey: Dr Debendra Tripathy, Dr Edward Johnson, Dr Hetal Vadera, Dr Kannan M, Dr Madhusudan Upadya, Dr Manpreet Singh, Dr Raj Tobin, Dr Sanjeev Palta, Dr Susheela Taxak, Dr Upendra Goud. The authors also extend their gratitude to the following for their help at various phases during preparation of the guidelines – Dr Gordon Guyatt (Canada), Dr Kuchelababu V (Past President, ISA National), Dr Venkatagiri KM (President, ISA National), Dr Sunidhara Reddy, Dr Jason Doctor.
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