Preoperative Investigations: Practice Guidelines from the Indian Society of Anaesthesiologists

Abstract

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].Table 1: Examples for categorisation of surgical procedures based on invasiveness and duration of surgeryThe 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 evidenceTable 3: Inclusion and exclusion criteriaMeta-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 methodTable 4: Evidence summary for complete blood count, renal function, liver function, serum electrolytes, coagulation profile, blood glucose, 12-lead electrocardiogram, chest X-rayTable 5: Evidence summary for preoperative sonographic airway assessment to predict difficult laryngoscopyRound 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 investigationsTo 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 1Recommendation 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 is suggested for patients undergoing minor surgery. Recommendation Preoperative serum creatinine is suggested for patients undergoing intermediate and major surgery. In ASA PS 1 and 2 patients scheduled to undergo elective surgery, will routine preoperative serum testing change anaesthetic management or patient outcomes after surgery? in serum and serum may be associated with and surgical and have a to the anaesthetic management and the study involving intermediate surgeries (n = and two studies involving minor and intermediate surgeries (n = did not report any adverse outcomes related to serum Three studies involving all three of surgeries (n = showed influence on outcomes in patients with serum Evidence with outcomes related to serum were not available [Table 4]. Online survey conducted as a part of this guideline formulation showed that of the total 1169 survey respondents, respondents preferred to get preoperative serum in minor, intermediate and major surgeries, respectively [Supplementary Appendix 1, available online]. Recommendation 3: Preoperative serum and is suggested for patients undergoing minor, intermediate and major surgery. 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? function tests serum and the and of the liver is a for function of the it is coagulation as a Low levels have been reported to be independent of the perioperative evidence relevant studies (n = for preoperative liver function tests were identified of which four studies conducted on patients undergoing minor and/or intermediate surgery (n = did not any influence of on In two studies involving patients scheduled for minor, intermediate and major surgeries (n = among patients had preoperative patients required further investigations, or delay, while three patients required blood components of did not have any adverse impact on the outcomes as reported in a study conducted on patients undergoing intermediate surgeries (n = [Table 4]. Online survey conducted as a part of this guideline formulation showed that of the total 1169 survey respondents, and respondents preferred to get preoperative in minor, intermediate and major surgeries, respectively [Supplementary Appendix 1, available online]. Recommendation Preoperative liver function testing is suggested for patients undergoing minor and intermediate surgery Recommendation Preoperative liver function testing is suggested for patients undergoing major surgery In ASA PS 1 and 2 patients scheduled to undergo elective surgery, will routine preoperative coagulation testing change anaesthetic management or patient outcomes after surgery? in preoperative coagulation tests may influence the perioperative management study involving intermediate surgeries (n = two studies involving minor and intermediate surgeries (n = and one study involving intermediate and major surgeries (n = did not report adverse outcomes related to abnormal coagulation In three studies involving all three of surgeries (n = change in approach or change in management was in 11 patients with abnormal preoperative coagulation reports [Table 4]. When regional are in patients on 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 of the total 1169 survey respondents, and respondents preferred to get preoperative coagulation in minor, intermediate and major surgeries, respectively [Supplementary Appendix 1, available online]. Recommendation 5: Preoperative coagulation and testing is suggested for patients undergoing minor, intermediate and major surgery. In ASA PS 1 and 2 patients scheduled to undergo elective surgery, will routine preoperative blood change anaesthetic management or patient outcomes after surgery? are considered as if there is no history, or previous investigation report of In such patients, of preoperative blood on perioperative outcomes needs to be In one study involving intermediate surgeries (n = no patient had abnormal blood In studies involving all three of surgeries (n = patients with blood required and needed a in [Table 4]. of increased blood level preoperative investigation in patients and its influence on major outcomes such as in the evidences were considered by the followed by further before at the Online survey conducted as a part of this guideline formulation showed that of the total 1169 survey respondents, and respondents preferred to get preoperative blood in minor, intermediate and major surgeries, respectively [Supplementary Appendix 1, available online]. Recommendation 6: In patients, blood is suggested when scheduled to undergo minor, intermediate and major surgery. 12-lead In ASA PS 1 and 2 patients scheduled to undergo elective surgery, will routine preoperative 12-lead testing change anaesthetic management or patient outcomes after surgery? Preoperative 12-lead testing can or or and may also and study involving intermediate surgeries (n = reported no adverse outcome in patients with studies involving all three of surgeries (n = reported changes in minor impact or in patients and a change in approach in 3 patient required postponement of the surgical procedure due to changes in the [Table 4]. status of a patient is by the of history, clinical or reports of disease. The of with The disease rate in India is higher than the global When patients at risk as per these evidences for surgery, events are more to be in the perioperative Published evidence along with this information was considered and by the experts before at the recommendations. Online survey conducted as a part of this guideline formulation showed that of the total 1169 survey respondents, and respondents preferred to get preoperative 12-lead test in minor, intermediate and major surgeries, Majority of the ISA members were in favour of an for routine preoperative Among these respondents, majority (n = were in favour of testing at of and [Supplementary Appendix 1, available online]. Recommendation In patients, 12-lead testing is suggested at and when scheduled to undergo minor and intermediate surgery. Recommendation Preoperative 12-lead testing is suggested for all patients undergoing major surgery. In ASA PS 1 and 2 patients scheduled to undergo elective surgery, will routine preoperative chest testing change anaesthetic management or patient outcomes after surgery? Preoperative chest have the to influence the perioperative management but the utility of this investigation needs to be considered in of the In one study involving intermediate surgeries (n = 10 patients with abnormal preoperative chest In 4 studies involving all 3 of surgeries (n = among those with abnormal preoperative chest minor impact investigations, or in the was in patients and a change in management required in 9 [Table 4]. of the changes may not be of relevance such as those of and The chest can also and changes to the impact of or and to have effect with changes in may not impact the perioperative These factors along with the evidences were considered and by the experts Delphi consensus, prior to at the recommendations. Online survey conducted as a part of this guideline formulation showed that of the total 1169 survey respondents, and respondents preferred to get preoperative chest testing in minor, intermediate and major surgeries, of the respondents to the online survey were in favour of based routine chest testing in patients scheduled for surgery. majority (n = were in favour of routine chest testing in patients and among were in favour of testing at patient at or [Supplementary Appendix 1, available online]. Recommendation Preoperative chest testing is suggested for patients undergoing minor surgery. Recommendation Preoperative chest testing is suggested for patients and undergoing intermediate and major surgery In ASA PS 1 and 2 patients scheduled to undergo elective surgery, will routine preoperative airway assessment predict difficult of for the anaesthesiologists has its utility for preoperative airway data that would be one of the important preoperative airway assessment could predict difficult more than the clinical in of the [Table These studies had used as of difficult With the available a specific parameter or a of to predict a difficult airway be airway ultrasound is an further research may be to the that have high and for predicting difficult Recommendation preoperative sonographic airway assessment is suggested for predicting difficult time for previous investigations In ASA PS 1 and 2 patients scheduled to undergo elective surgery, is the validity time for previous investigations provided the patient's in the The Time for Previous Investigations refers to the interval from the time of previous testing for any to current preoperative study (n = that normal blood test reports serum and coagulation within the 2 from the of surgery did not in their influence on the outcomes to those which were performed within 1 or 2 prior to A cohort study (n = considered the preoperative test reports blood glucose, coagulation tests, and chest for the surgical procedure and with the test reports for The preoperative test reports for second surgery performed 12 after the intervention, and minor did not have any influence on the outcomes. Recommendation The validity time for a previously performed normal complete blood count, renal function tests, liver function tests, coagulation profile, is suggested to be 2 provided the clinical of the patient has not in the period. Recommendation The validity time for a previously performed normal 12-lead and chest is suggested to be 12 provided the clinical of the patient has not in the period. and evidence of randomised controlled and of data in the available studies testing were major for the The certainty level for the available literature was low or very low and hence the recommendations for all the RQs are After the formulation of the final the reviewed additional the original search November In one study (n = majority of the patients were tested for CBC, serum electrolytes, blood glucose, 12-lead and chest In those patients where reports were there was no influence on the outcomes. The categorisation of patients in terms of the of surgery was not studies (n = preoperative airway assessment to be a better assessment for predicting difficult to used clinical study (n = that preoperative airway assessment was not to clinical evaluation in predicting difficult The outcomes from these additional evidences were in agreement with the recommendations. Hence, these guidelines with the latest evidence. A is to be for for and clinical in and other [Supplementary Appendix 2, available online].SUPPLEMENTARY APPENDIX members of the SBB A and This guidelines is and by the Indian Society of Anaesthesiologists of There are no of

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