Analgesia for major laparoscopic abdominal surgery: a randomised feasibility trial using intrathecal morphine.

Effective pain control enhances patient recovery after surgery. Laparoscopic techniques for major abdominal surgery are increasingly utilised to reduce surgical trauma. Intrathecal morphine is an attractive analgesic option that is gaining popularity. However, limited evidence guides its use in the setting of laparoscopic surgery. In addition, enhanced recovery after surgery pathways advocate opioid-sparing techniques. We conducted a feasibility trial to compare intrathecal morphine with non-neuraxial analgesia in laparoscopic or laparoscopic-assisted major abdominal surgery to inform the design of a future large clinical trial. This multicentre, double-blind, randomised controlled trial was conducted at two tertiary hospitals in Australia. Fifty-one patients were randomly allocated to receive either intrathecal morphine (intervention group) or a sham subcutaneous injection of normal saline in the lumbar area (control group) immediately before the induction of general anaesthesia. Co-primary outcomes were patient recruitment and successful adherence to treatment allocation as per the study protocol. The primary endpoints of feasibility and protocol adherence were met with a 46% recruitment rate (51 of 110 eligible patients) and 96% protocol adherence. There was only one patient with failed access to the intrathecal space. For secondary endpoints, fewer patients in the intrathecal morphine group required opioids in the post-anaesthesia care unit, their postoperative pain scores at rest were lower across the four time-points measured (p = 0.007), but not dynamic pain scores (p = 0.061), and pruritus was more common following intrathecal morphine (p = 0.007). Total oral morphine equivalents until postoperative day 3 were less in the intrathecal morphine group (median (95%CI) difference 82 (-13 to 168) mg), but this reduction was not statistically significant (p = 0.10). These findings support conducting a definitive clinical trial.

The effect of advanced recovery room care on postoperative outcomes in moderate-risk surgical patients: a multicentre feasibility study.

Postoperative complications are common and may be under-recognised. It has been suggested that enhanced postoperative care in the recovery room may reduce in-hospital complications in moderate- and high-risk surgical patients. We investigated the feasibility of providing advanced recovery room care for 12-18 h postoperatively in the post-anaesthesia care unit. The primary hypothesis was that a clinical trial of advanced recovery room care was feasible. The secondary hypothesis was that this model may have a sustained impact on postoperative in-hospital and post-discharge events. This was a multicentre, prospective, feasibility before-and-after trial of moderate-risk patients (predicted 30-day mortality of 1-4%) undergoing non-cardiac surgery and who were scheduled for postoperative ward care. Patients were managed using defined assessment checklists and goals of care in an advanced recovery room care setting in the immediate postoperative period. This utilised existing post-anaesthesia care unit infrastructure and staffing, but extended care until the morning of the first postoperative day. The advanced recovery room care trial was deemed feasible, as defined by the recruitment and per protocol management of > 120 patients. However, in a specialised cancer centre, recruitment was slow due to low rates of eligibility according to narrow inclusion criteria. At a rural site, advanced recovery room care could not be commenced due to logistical issues in establishing a new model of care. A definitive randomised controlled trial of advanced recovery room care appears feasible and, based on the indicative data on outcomes, we believe this is warranted.

Volatile anaesthesia and peri-operative outcomes related to cancer: a feasibility and pilot study for a large randomised control trial.

Published data suggest that the type of general anaesthesia used during surgical resection for cancer may impact on patient long-term outcome. However, robust prospective clinical evidence is essential to guide a change in clinical practice. We explored the feasibility of conducting a randomised controlled trial to investigate the impact of total intravenous anaesthesia with propofol vs. inhalational volatile anaesthesia on postoperative outcomes of patients undergoing major cancer surgery. We undertook a randomised, double-blind feasibility and pilot study of propofol total intravenous anaesthesia or volatile-based maintenance anaesthesia during cancer resection surgery at three tertiary hospitals in Australia and the USA. Patients were randomly allocated to receive propofol total intravenous anaesthesia or volatile-based maintenance anaesthesia. Primary outcomes for this study were successful recruitment to the study and successful delivery of the assigned anaesthetic treatment as per randomisation arm. Of the 217 eligible patients approached, 146 were recruited, a recruitment rate of 67.3% (95%CI 60.6-73.5%). One hundred and forty-five patients adhered to the randomised treatment arm, 99.3% (95%CI 96.2-100%). Intra-operative patient characteristics and postoperative complications were comparable between the two intervention groups. This feasibility and pilot study supports the viability of the protocol for a large, randomised controlled trial to investigate the effect of anaesthesia technique on postoperative cancer outcomes. The volatile anaesthesia and peri-operative outcomes related to cancer (VAPOR-C) study that is planned to follow this feasibility study is an international, multicentre trial with the aim of providing evidence-based guidelines for the anaesthetic management of patients undergoing major cancer surgery.

Integration of the Duke Activity Status Index into preoperative risk evaluation: a multicentre prospective cohort study.

BACKGROUND: The Duke Activity Status Index (DASI) questionnaire might help incorporate self-reported functional capacity into preoperative risk assessment. Nonetheless, prognostically important thresholds in DASI scores remain unclear. We conducted a nested cohort analysis of the Measurement of Exercise Tolerance before Surgery (METS) study to characterise the association of preoperative DASI scores with postoperative death or complications. METHODS: The analysis included 1546 participants (≥40 yr of age) at an elevated cardiac risk who had inpatient noncardiac surgery. The primary outcome was 30-day death or myocardial injury. The secondary outcomes were 30-day death or myocardial infarction, in-hospital moderate-to-severe complications, and 1 yr death or new disability. Multivariable logistic regression modelling was used to characterise the adjusted association of preoperative DASI scores with outcomes. RESULTS: The DASI score had non-linear associations with outcomes. Self-reported functional capacity better than a DASI score of 34 was associated with reduced odds of 30-day death or myocardial injury (odds ratio: 0.97 per 1 point increase above 34; 95% confidence interval [CI]: 0.96-0.99) and 1 yr death or new disability (odds ratio: 0.96 per 1 point increase above 34; 95% CI: 0.92-0.99). Self-reported functional capacity worse than a DASI score of 34 was associated with increased odds of 30-day death or myocardial infarction (odds ratio: 1.05 per 1 point decrease below 34; 95% CI: 1.00-1.09), and moderate-to-severe complications (odds ratio: 1.03 per 1 point decrease below 34; 95% CI: 1.01-1.05). CONCLUSIONS: A DASI score of 34 represents a threshold for identifying patients at risk for myocardial injury, myocardial infarction, moderate-to-severe complications, and new disability.

A randomised controlled trial comparing deep neuromuscular blockade reversed with sugammadex with moderate neuromuscular block reversed with neostigmine.

Deep neuromuscular block aims to improve operative conditions during laparoscopic surgery with a lower intra-abdominal pressure. Studies are conflicting on whether meaningful improvements in quality of recovery occur beyond emergence, and whether lower intra-abdominal pressure is achieved. In this pragmatic randomised trial with 1:1 allocation, adults undergoing elective laparoscopic surgery were allocated to moderate neuromuscular block reversed with neostigmine, or deep neuromuscular block reversed with sugammadex. Allocation was revealed to the anaesthetist only. Primary outcome was cognitive recovery of the Postoperative Quality of Recovery Scale, 7 days after surgery. Secondary outcomes included recovery in other domains of the Postoperative Quality of Recovery Scale at 15 min and 40 min; days 1, 3, 7, 14; and 1 and 3 months after surgery. Chi-square test was used for the primary outcome, and generalised linear mixed model for recovery over time between groups. Of 350 participants randomised, 140 (deep) and 144 (moderate) were analysed for the primary outcome. There was no difference in the Postoperative Quality of Recovery Scale cognitive domain at day 7 (deep 92.9% vs. moderate 91.8%, OR 1.164; 95%CI 0.486-2.788, p = 0.826), or at any other time-point. No significant difference was observed for physiological, emotive, activities of daily living, nociception, or overall recovery. Length of stay in the recovery area (mean (SD) deep 108 (58) vs. moderate 109 (57) min, p = 0.78) and hospital (1.8 (1.9) vs. 2.6 (3.5) days, p = 0.019) was not different. Intra-abdominal pressure and surgical operating conditions were not different between groups. Deep neuromuscular block did not improve quality of recovery compared with moderate neuromuscular block in operative laparoscopic surgery over a 1-h duration.

Impact of a risk-stratified thromboprophylaxis protocol on the incidence of postoperative venous thromboembolism and bleeding.

Efforts to reduce postoperative venous thromboembolism are challenging due to heterogeneity in thromboprophylaxis practice. As a result, a 'one-size-fits-all' approach that accounts for surgery-specific risk, but fails to account for patient-level variation, is often adopted by healthcare networks. Updated clinical practice guidelines have advocated an individualised risk-stratified approach that balances the risk:benefit ratio associated with thromboprophylaxis; however, there are limited data confirming effectiveness of these recommendations on the incidence of postoperative venous thromboembolism and bleeding. We developed the surgical-thrombo-embolism-prevention protocol, a novel risk-stratified algorithm that classified patients into low-, intermediate-, and high-risk profiles according to surgical procedure and patient baseline medical risk. Expert-endorsed risk-specific thromboprophylaxis strategies were then applied. A staged quality improvement program was developed to implement the protocol. We postulated that compliance with the protocol would reduce postoperative venous thromboembolism rates without increasing the incidence of postoperative bleeding. Between June 2013 and March 2018, we evaluated the efficacy, safety and sustainability of this risk-stratified approach in 24,953 surgical admissions at a dedicated cancer centre. By final implementation, program compliance was 91%. Postoperative venous thromboembolism rates reduced from 3.1 per 1000 surgical admissions to 0.6 per 1000 surgical admissions (relative risk reduction 79%; p < 0.005). Postoperative bleeding rates also declined from 10.0 per 1000 surgical admissions to 6.3 per 1000 surgical admissions (relative risk reduction 37%; p = 0.02). Sustained improvement was evident more than 3 years after implementation. Implementation of the surgical-thrombo-embolism-prevention protocol significantly reduced the incidence of postoperative venous thromboembolism supporting its validation at other institutions.

Guidelines for Perioperative Care in Elective Colorectal Surgery: Enhanced Recovery After Surgery (ERAS®) Society Recommendations: 2018.

BACKGROUND: This is the fourth updated Enhanced Recovery After Surgery (ERAS®) Society guideline presenting a consensus for optimal perioperative care in colorectal surgery and providing graded recommendations for each ERAS item within the ERAS® protocol. METHODS: A wide database search on English literature publications was performed. Studies on each item within the protocol were selected with particular attention paid to meta-analyses, randomised controlled trials and large prospective cohorts and examined, reviewed and graded according to Grading of Recommendations, Assessment, Development and Evaluation (GRADE) system. RESULTS: All recommendations on ERAS® protocol items are based on best available evidence; good-quality trials; meta-analyses of good-quality trials; or large cohort studies. The level of evidence for the use of each item is presented accordingly. CONCLUSIONS: The evidence base and recommendation for items within the multimodal perioperative care pathway are presented by the ERAS® Society in this comprehensive consensus review.

Effect of beta-blockers on cancer recurrence and survival: a meta-analysis of epidemiological and perioperative studies.

BACKGROUND: The biological perturbation associated with psychological and surgical stress is implicated in cancer recurrence. Preclinical evidence suggests that beta-blockers can be protective against cancer progression. We undertook a meta-analysis of epidemiological and perioperative clinical studies to investigate the association between beta-blocker use and cancer recurrence (CR), disease-free survival (DFS), and overall survival (OS). METHODS: Databases were searched until September 2017, reported hazard ratios (HRs) pooled, and 95% confidence intervals (CIs) calculated. Comparative studies examining the effect of beta-blockers (selective and non-selective) on cancer outcomes were included. The Newcastle Ottawa Scale was used to assess methodological quality and bias. RESULTS: Of the 27 included studies, nine evaluated the incidental use of non-selective beta-blockers, and ten were perioperative studies. Beta-blocker use had no effect on CR. Within subgroups of cancer, melanoma was associated with improved DFS (HR 0.03, 95% CI 0.01-0.17) and OS (HR 0.04, 95% CI 0.00-0.38), while endometrial cancer had an associated reduction in DFS (HR 1.40, 95% CI 1.10-1.80) and OS (HR 1.50, 95% CI 1.12-2.00). There was also reduced OS seen with head and neck and prostate cancer. Non-selective beta-blocker use was associated with improved DFS and OS in ovarian cancer, improved DFS in melanoma, but reduced OS in lung cancer. Perioperative studies showed similar variable effects across cancer types, albeit from a limited data pool. CONCLUSION: Beta-blocker use had no evident effect on CR. The beneficial effect of beta-blockers on DFS and OS in the epidemiological or perioperative setting remains variable, tumour-specific, and of low-level evidence at present.

Systematic review and consensus definitions for standardised endpoints in perioperative medicine: postoperative cancer outcomes.

BACKGROUND: The Standardising Endpoints for Perioperative Medicine group was established to derive an appropriate set of endpoints for use in clinical trials related to anaesthesia and perioperative medicine. Anaesthetic or analgesic technique during cancer surgery with curative intent may influence the risk of recurrence or metastasis. However, given the current equipoise in the existing literature, prospective, randomised, controlled trials are necessary to test this hypothesis. As such, a cancer subgroup was formed to derive endpoints related to research in onco-anaesthesia based on a current evidence base, international consensus and expert guidance. METHODS: We undertook a systematic review to identify measures of oncological outcome used in the oncological, surgical, and wider literature. A multiround Delphi consensus process that included up to 89 clinician-researchers was then used to refine a recommended list of endpoints. RESULTS: We identified 90 studies in a literature search, which were the basis for a preliminary list of nine outcome measures and their definitions. A further two were added during the Delphi process. Response rates for Delphi rounds one, two, and three were 88% (n=9), 82% (n=73), and 100% (n=10), respectively. A final list of 10 defined endpoints was refined and developed, of which six secured approval by ≥70% of the group: cancer health related quality of life, days alive and out of hospital at 90 days, time to tumour progression, disease-free survival, cancer-specific survival, and overall survival (and 5-yr overall survival). CONCLUSION: Standardised endpoints in clinical outcomes studies will support benchmarking and pooling (meta-analysis) of trials. It is therefore recommended that one or more of these consensus-derived endpoints should be considered for inclusion in clinical trials evaluating a causal effect of anaesthesia-analgesia technique on oncological outcomes.

The effect of anaesthetic technique during primary breast cancer surgery on neutrophil-lymphocyte ratio, platelet-lymphocyte ratio and return to intended oncological therapy.

Inflammation and immunosuppression contribute to the pathogenesis of cancer. An increased neutrophil-lymphocyte ratio reflects these processes and is associated with adverse cancer outcomes. Whether anaesthetic technique for breast cancer surgery influences these factors, and potentially cancer recurrence, remains unknown. We conducted a secondary analysis in patients enrolled in an ongoing trial of anaesthetic technique on breast cancer recurrence. The primary hypothesis was that postoperative neutrophil-lymphocyte ratio is lower in patients allocated to receive propofol-paravertebral rather than inhalational agent-opioid anaesthesia for primary breast cancer surgery. Among 397 patients, 116 had differential white cell counts performed pre-operatively and postoperatively. Pre-operative neutrophil-lymphocyte ratio was similar in the propofol-paravertebral 2.3 (95%CI 1.8-2.8) and inhalational agent-opioid anaesthesia 2.2 (1.9-3.2) groups, p = 0.72. Postoperative neutrophil-lymphocyte ratio was lower (3.0 (2.4-4.2) vs. 4.0 (2.9-5.4), p = 0.001) in the propofol-paravertebral group. Propofol-paravertebral anaesthesia attenuated the postoperative increase in the neutrophil-lymphocyte ratio.

A pilot study of cardiopulmonary exercise testing and cardiac stress positron emission tomography before major non-cardiac surgery.

Cardiac events are a common cause of peri-operative morbidity. Cardiopulmonary exercise testing can objectively assess risk, but it does not quantify myocardial ischaemia. With appropriate dietary preparation to suppress basal myocardial glucose uptake, positron emission tomography with 18 F-fluorodeoxyglucose can identify post-ischaemic myocardium, providing an attractive complement to exercise testing. We aimed to investigate the feasibility of this diagnostic algorithm. Patients referred for cardiopulmonary exercise testing before major cancer surgery were prospectively recruited. Exercise testing and positron emission tomography imaging were performed after a high fat-low carbohydrate meal. Protocol feasibility (primary end-point) included compliance with pre-test diet instructions and the completion of tests. Stress myocardial perfusion imaging was performed if either exercise testing or positron emission tomography was equivocal or positive for ischaemia. We recorded cardiac complications for 30 postoperative days. We enrolled 26 participants, 20 of whom completed protocol. Twenty-one participants proceeded to surgery: myocardial injury or infarction was diagnosed in three participants, two of whom had positive or equivocal positron emission tomography but negative myocardial perfusion imaging. We have shown that pre-operative cardiac positron emission tomography after cardiopulmonary exercise testing is feasible; protocol deviations were minor and did not affect image quality. Our findings warrant further investigation to compare the diagnostic utility of cardiac positron emission tomography imaging with standard pre-operative stress tests.

The enhanced recovery after surgery (ERAS) Greenie Board: a Navy-inspired quality improvement tool.

The United States Navy uses a visual feedback system for pilots, named 'the Greenie Board', to improve flight manoeuvres on aircraft carriers. Given that increased compliance with enhanced recovery after surgery protocols reduces postoperative complications, we decided to apply a similar feedback system to our institutional enhanced recovery programme. We undertook a prospective 12-month audit of 194 patients assigned to our enhanced recovery programme and evaluated adherence to the anaesthesia-related components of our protocol, before and after implementing a Greenie Board. A compliance score was calculated by summing points for adherence to: intra-operative antibiotic prophylaxis; temperature management; goal-directed intravenous fluid therapy; postoperative nausea and vomiting prophylaxis; and postoperative fluid restriction. The score for each patient was then colour-coded and anonymously displayed for each anaesthetist on a Greenie Board within the operating theatre suite. Protocol adherence improved significantly following introduction, with 'Green' scores (acceptable compliance) increasing from 33% to 72% of patients (p < 0.0001). The greatest improvement was seen with anti-emetic prophylaxis (49% to 70%, p = 0.004) with a consequent reduction in postoperative nausea and vomiting (OR 0.42, 95% CI 0.19-0.88, p = 0.021). We did not observe a decrease in other postoperative complications nor hospital length of stay. We conclude that this US Navy-inspired feedback system is an easily implemented, low-cost quality improvement tool that significantly improved adherence to intra-operative components of our enhanced recovery protocol. The system lends itself to global scaling to drive quality improvement in healthcare delivery and would be suited to institutions without electronic medical records, including low-resource countries.

Endothelial progenitor cell mobilization by preoperative exercise: a bone marrow response associated with postoperative outcome.

BACKGROUND: Preoperative anaemia is associated with increased morbidity in patients undergoing major surgery. Whether erythrocytes are the only bone-marrow-derived cell lineage that associates with increased surgical complications is unknown. This prospective observational trial studied the mobilization of endothelial progenitor cells (EPCs) in response to exercise in association with postoperative complications. METHODS: After IRB approval, 60 subjects undergoing major thoracic surgery were exercised to exhaustion (peak V̇(O2)). Peripheral blood collected before and after peak exercise was quantified for EPC lineages by fluorescence-activated cell sorter analysis. Complication analysis was based on the Clavien-Dindo classification. RESULTS: Exhaustive exercise increased EPC [CD45-133+34+ cells=150 (0.00-5230) to 220 (0.00-1270) cells µl(-1); median change (range)=20 (-4,180-860) cells µl(-1); P=0.03] but not mature endothelial cell (EC) subpopulations. Pre-exercise levels [odds ratio (OR)=0.86, 95% confidence interval (CI): 0.37-2.00, P=0.72), change after exercise as a continuous variable (OR=0.95, 95% CI: 0.41-2.22, P=0.91) and a positive response after exercise (change >0 cells µl(-1); OR=0.41, 95% CI: 0.13-1.28, P=0.12) were not statistically significantly associated with the incidence of postoperative complications. Post-hoc receiver operating characteristic curve analyses revealed that subjects with a CD45-133+34+ increase ≥60 cells µl(-1) in response to exercise suffered fewer postoperative complications [86% sensitivity, 48% specificity and AUC=0.67 (95% CI: 0.52-0.81)]. CONCLUSIONS: Preoperative exercise induces EPC into the peripheral circulation. Subjects with a poor EPC response had a pre-existing propensity for postoperative complications. This warrants further research into the role of bone marrow function as a critical component to endothelial repair mechanisms. CLINICAL TRIAL REGISTRATION: IRB 2003-0434 (University of Texas M.D. Anderson Cancer Center, Houston, TX, USA).

Perioperative epidural analgesia reduces cancer recurrence after gastro-oesophageal surgery.

BACKGROUND: Recent interest has focused on the role of perioperative epidural analgesia in improving cancer outcomes. The heterogeneity of studies (tumour type, stage and outcome endpoints) has produced inconsistent results. Clinical practice also highlights the variability in epidural effectiveness. We considered the novel hypothesis that effective epidural analgesia improves cancer outcomes following gastro-oesophageal cancer surgery in patients with grouped pathological staging. METHODS: Following institutional approval, a database analysis identified 140 patients, with 2-year minimum follow-up after gastro-oesophageal cancer surgery. All patients were operated on by a single surgeon (2005-2010). Information pertaining to cancer and survival outcomes was extracted. RESULTS: Univariate analysis demonstrated a 1-year 14% vs. 33% (P = 0.01) and 2-year 27% vs. 40% [hazard ratio (HR)=0.59; 95% CI, 0.32-1.09, P = 0.087] incidence of cancer recurrence in patients with (vs. without) effective (> 36 h duration) epidural analgesia, respectively. Multivariate analysis demonstrated increased time to cancer recurrence (HR = 0.33; 95% CI: 0.17-0.63, P < 0.0001) and overall survival benefit (HR = 0.42; 95% CI: 0.21-0.83, P < 0.0001) at 2-year follow-up following effective epidural analgesia. Subgroup analysis identified epidural-related cancer recurrence benefit in patients with oesophageal cancer (HR = 0.34; 95% CI: 0.16-0.75, P = 0.005) and in patients with tumour lymphovascular space infiltration (LVSI), (HR = 0.49; 95% CI: 0.26-0.94, P = 0.03). Effective epidural analgesia improved estimated median time to death (2.9 vs. 1.8 years, P = 0.029) in patients with tumour LVSI. CONCLUSIONS: This study found an association between effective post-operative epidural analgesia and medium-term benefit on cancer recurrence and survival following oesophageal surgery. A prospective study that controls for disease type, stage and epidural effectiveness is warranted.

Asystole following spinal anaesthesia: the hazards of intrinsic cardiac reflexes.

Unwanted initiation of intrinsic cardiac reflexes can precipitate bradycardia and cardiac arrest after spinal anaesthesia. We report the case of a 40-year-old man who suffered sudden asystolic cardiac arrest following spinal anaesthesia prior to planned abdominal surgery, likely due to the initiation of one or more intrinsic cardiac reflexes including the Bezold-Jarisch reflex, the reverse Bainbridge reflex and the pacemaker stretch reflex. The characteristics of this patient placed him at increased risk of this underappreciated cause of bradycardia and hypotension. We present a summary of the physiology and clinical features relevant to this case and the considerations for avoidance of similar complications after spinal anaesthesia.

A pilot study evaluating predictors of postoperative outcomes after major abdominal surgery: Physiological capacity compared with the ASA physical status classification system.

BACKGROUND: This pilot study compared the risk predictive value of preoperative physiological capacity (PC: defined by gas exchange measured during cardiopulmonary exercise testing) with the ASA physical status classification in the same patients (n=32) undergoing major abdominal cancer surgery. METHODS: Uni- and multivariate logistic regression models were fitted to measurements of PC and ASA rank data determining their predictive value for postoperative morbidity. Receiver operating characteristic (ROC) curves were used to discriminate between the predictive abilities, exploring trade-offs between sensitivity and specificity. RESULTS: Individual statistically significant predictors of postoperative morbidity included the ASA rank [P=0.038, area under the curve (AUC)=0.688, sensitivity=0.630, specificity=0.750] and three newly identified measures of PC: PAT (% predicted anaerobic threshold achieved, <75% vs > or =75%), DeltaHR1 (heart rate response from rest to the anaerobic threshold), and HR3 (heart rate at the anaerobic threshold). A two-variable model of PC measurements (DeltaHR1+PAT) was also shown to be statistically significant in the prediction of postoperative morbidity (P=0.023, AUC=0.826, sensitivity=0.813, specificity=0.688). CONCLUSIONS: Three newly identified PC measures and the ASA rank were significantly associated with postoperative morbidity; none showed a statistically greater association compared with the others. PC appeared to improve predictive sensitivity. The potential for new unidentified measures of PC to predict postoperative outcomes remains unexplored.