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1.
Surgery ; 174(2): 268-276, 2023 08.
Article in English | MEDLINE | ID: mdl-37221106

ABSTRACT

BACKGROUND: To compare the outcomes of sac invagination and sac ligation in patients undergoing open Lichtenstein repair of indirect inguinal hernia. METHODS: A systematic review in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement standards was conducted to identify all randomized controlled trials comparing the outcomes of sac invagination and sac ligation in patients undergoing open Lichtenstein repair of indirect inguinal hernia. Random effects modeling was applied to calculate pooled outcome data. RESULTS: Analysis of 843 patients with 851 hernias from 6 randomized controlled trials suggested no difference between the sac invagination and sac ligation techniques in terms of recurrence (risk difference: 0.00, P = .91), chronic pain (risk difference: 0.00, P = .98), operative time (mean difference: -0.15, P = .89), hematoma (odds ratio: 0.93, P = .93), seroma (odds ratio: 1.00, P = 1.00), surgical site infection (odds ratio: 1.68, P = .40), or urinary retention (odds ratio: 0.85, P = .78); however, ligation of sac resulted in more early postoperative pain as measured by visual analog scale score at 6 hours postoperatively (mean difference: -0.92, P < .00001), at 12 hours postoperatively (mean difference: -0.94, P = .001), at 24 hours postoperatively (mean difference: -1.08, P < .00001), and on day 7 postoperatively (mean difference: -0.99, P = .009). The quality and certainty of the available evidence were moderate. CONCLUSION: Evidence from randomized controlled trials with moderate certainty suggests that ligation of indirect inguinal hernia sac during open Lichtenstein repair may not improve the outcomes regarding recurrence, chronic pain, or operative complications but may result in more early postoperative pain. Future randomized controlled trials with more robust statistical power and methodological quality would help improve the available evidence's certainty.


Subject(s)
Chronic Pain , Hernia, Inguinal , Humans , Chronic Pain/etiology , Hernia, Inguinal/surgery , Hernia, Inguinal/complications , Herniorrhaphy/adverse effects , Herniorrhaphy/methods , Randomized Controlled Trials as Topic , Pain, Postoperative/epidemiology , Pain, Postoperative/etiology , Surgical Mesh/adverse effects , Recurrence
2.
Ann Hepatobiliary Pancreat Surg ; 27(1): 6-19, 2023 Feb 28.
Article in English | MEDLINE | ID: mdl-36245071

ABSTRACT

A systematic review was conducted in compliance with PRISMA statement standards to identify all studies reporting outcomes of laparoscopic resection of benign or malignant lesions located in caudate lobe of liver. Pooled outcome data were calculated using random-effects models. A total of 196 patients from 12 studies were included. Mean operative time, volume of intraoperative blood loss, and length of hospital stay were 225 minutes (95% confidence interval [CI], 181-269 minutes), 134 mL (95% CI, 85-184 mL), and 7 days (95% CI, 5-9 days), respectively. The pooled risk of need for intraoperative transfusion was 2% (95% CI, 0%-5%). It was 3% (95% CI, 1%-6%) for conversion to open surgery, 6% (95% CI, 0%-19%) for need for intra-abdominal drain, 1% (95% CI, 0%-3%) for postoperative mortality, 2% (95% CI, 0%-4%) for biliary leakage, 2% (95% CI, 0%-4%) for intra-abdominal abscess, 1% (95% CI, 0%-4%) for biliary stenosis, 1% (95% CI, 0%-3%) for postoperative bleeding, 1% (95% CI, 0%-4%) for pancreatic fistula, 2% (95% CI, 1%-5%) for pulmonary complications, 1% (95% CI, 0%-4%) for paralytic ileus, and 1% (95% CI, 0%-4%) for need for reoperation. Although the available evidence is limited, the findings of the current study might be utilized for hypothesis synthesis in future studies. They can be used to inform surgeons and patients about estimated risks of perioperative complications until a higher level of evidence is available.

3.
World J Gastrointest Surg ; 15(12): 2747-2756, 2023 Dec 27.
Article in English | MEDLINE | ID: mdl-38222004

ABSTRACT

BACKGROUND: Hajibandeh index (HI), derived from combined levels of C-reactive protein, lactate, neutrophils, lymphocytes and albumin, is a modern predictor of peritoneal contamination and mortality in patients with acute abdominal pathology. AIM: To validate the performance of HI in predicting the presence and nature of peritoneal contamination in patients with acute abdominal pathology in a larger cohort study and to synthesis evidence in a systematic review and meta-analysis. METHODS: The STROBE guidelines and the PRISMA statement standards were followed to conduct a cohort study (ChiCTR2200056183) and a meta-analysis (CRD42022306018), respectively. All adult patients undergoing emergency laparotomy for acute abdominal pathology were eligible. The accuracy of the HI was evaluated using receiver operating characteristic (ROC) curve analysis in the cohort study and using weighted summary area under the curve (AUC) under the fixed and random effects modelling in the meta-analysis. The Quality Assessment of Diagnostic Accuracy Studies 2 criteria were used for methodological quality assessment of the included studies. RESULTS: A total of 1437 patients were included (700 from the cohort study and 737 from the literature search). ROC curve analysis of the cohort study showed that the AUC of HI for presence of contamination, purulent contamination and feculent contamination were 0.79 [95% confidence interval (CI): 0.76-0.82, P < 0.0001], 0.76 (95%CI: 0.72-0.80, P < 0.0001), and 0.83 (95%CI: 0.79-0.86, P < 0.0001), respectively. The meta-analysis showed that the pooled AUC of HI for presence of contamination, purulent contamination and feculent contamination were 0.79 (95%CI: 0.75-0.83), 0.78 (95%CI: 0.74-0.81), and 0.80 (95%CI: 0.77-0.83), respectively. CONCLUSION: The HI is a strong and accurate predictor of intraperitoneal contamination. Although the available evidence is robust, it is limited to the studies conducted by our evidence synthesis group. We encourage other researchers to validate performance of HI in predicting the presence of intraperitoneal contamination and more importantly in predicting mortality following emergency laparotomy.

4.
Eur J Public Health ; 32(5): 807-812, 2022 10 03.
Article in English | MEDLINE | ID: mdl-35997587

ABSTRACT

BACKGROUND: Effective shielding measures and virus mutations have progressively modified the disease between the waves, likewise healthcare systems have adapted to the outbreak. Our aim was to compare clinical outcomes for older people with COVID-19 in Wave 1 (W1) and Wave 2 (W2). METHODS: All data, including the Clinical Frailty Scale (CFS), were collected for COVID-19 consecutive patients, aged ≥65, from 13 hospitals, in W1 (February-June 2020) and W2 (October 2020-March 2021). The primary outcome was mortality (time to mortality and 28-day mortality). Data were analysed with multilevel Cox proportional hazards, linear and logistic regression models, adjusted for wave baseline demographic and clinical characteristics. RESULTS: Data from 611 people admitted in W2 were added to and compared with data collected during W1 (N = 1340). Patients admitted in W2 were of similar age, median (interquartile range), W2 = 79 (73-84); W1 = 80 (74-86); had a greater proportion of men (59.4% vs. 53.0%); had lower 28-day mortality (29.1% vs. 40.0%), compared to W1. For combined W1-W2 sample, W2 was independently associated with improved survival: time-to-mortality adjusted hazard ratio (aHR) = 0.78 [95% confidence interval (CI) 0.65-0.93], 28-day mortality adjusted odds ratio = 0.80 (95% CI 0.62-1.03). W2 was associated with increased length of hospital stay aHR = 0.69 (95% CI 0.59-0.81). Patients in W2 were less frail, CFS [adjusted mean difference (aMD) = -0.50, 95% CI -0.81, -0.18], as well as presented with lower C-reactive protein (aMD = -22.52, 95% CI -32.00, -13.04). CONCLUSIONS: COVID-19 older adults in W2 were less likely to die than during W1. Patients presented to hospital during W2 were less frail and with lower disease severity and less likely to have renal decline.


Subject(s)
COVID-19 , Aged , Aged, 80 and over , C-Reactive Protein , COVID-19/epidemiology , Cohort Studies , Disease Outbreaks , Female , Humans , Male
5.
Int J Surg ; 102: 106645, 2022 Jun.
Article in English | MEDLINE | ID: mdl-35533852

ABSTRACT

OBJECTIVES: To compare performance of the Hajibandeh Index (HI) and National Emergency Laparotomy Audit (NELA) score in predicting postoperative mortality in patients undergoing emergency laparotomy. METHODS: In compliance with STROCSS guidelines for observational studies a cohort study was conducted. All patients aged over 18 who underwent emergency laparotomy between January 2014 and January 2021 in our centre were considered eligible for inclusion. The HI and NELA indices in predicting 30-day and 90-day postoperative mortality were compared. The discrimination of each test was evaluated using Receiver Operating Characteristic (ROC) curve analysis, classification using the classification table and calibration using a plotted diagram of the expected versus observed mortality rates. RESULTS: Analysis of 700 patients showed that the predictive performance of the HI and NELA models were comparable (30-day mortality: AUC: 0.86 vs 0.87, P = 0.557; 90-day mortality: AUC: 0.81 vs 0.84, P = 0.0607). In terms of 30-day mortality, HI was significantly better than the NELA model in predicting postoperative mortality in patients aged over 80 (AUC: 0.85 vs 0.72, P = 0.0174); however, the performances of both tools were comparable in patients with ASA status above 3 (AUC: 0.82 vs 0.82, P = 0.9775), patients with intraperitoneal contamination (AUC: 0.77 vs 0.85, P = 0.0728) and patients who needed a bowel resection (AUC: 0.85 vs 0.88, P = 0.2749). In terms of 90-day mortality, HI was significantly better than the NELA model in predicting mortality in patients aged over 80 (AUC: 0.82 vs 0.71, P = 0.0214); however, NELA had better predictive value in patients with intraperitoneal contamination (AUC: 0.76 vs 0.85, P = 0.0268); the performances of both tools were comparable in patients with ASA status above 3 (AUC: 0.77 vs 0.80, P = 0.2582), and patients who needed a bowel resection (AUC: 0.81 vs 0.86, P = 0.05). Both tools were comparable in terms of classification and calibration. CONCLUSIONS: Hajibandeh index was better than the NELA score in predicting postoperative 30-day and 90-day mortality in patients aged over 80 undergoing emergency laparotomy. Its performance in predicting 30-day and 90-day mortality was comparable with NELA score in other subgroups except 90-day mortality in patients with intraperitoneal contamination where the performance of NELA was better. We encourage other researchers to validate HI in predicting mortality following emergency laparotomy.


Subject(s)
Laparotomy , Aged , Cohort Studies , Humans , Laparotomy/adverse effects , ROC Curve , Retrospective Studies , Risk Assessment
6.
Langenbecks Arch Surg ; 407(3): 937-946, 2022 May.
Article in English | MEDLINE | ID: mdl-35039923

ABSTRACT

AIMS: We aimed to compare the outcomes of iatrogenic gallbladder perforation (IGP) versus no gallbladder perforation in patients undergoing laparoscopic cholecystectomy. METHODS: A systematic review and meta-analysis was conducted in compliance with PRISMA statement standards. We searched the MEDLINE, EMBASE, CINAHL Scopus, and CENTRAL to identify eligible studies. The last search was run on 17 October 2021. The outcome of interest included surgical site infection (SSI), postoperative collection, operative time, and length of hospital stay. Random effects modelling was applied to calculate pooled outcome data. The certainty of evidence was assessed using GRADE system. RESULTS: Analysis of 5366 patients from 11 observational studies suggested that IGP during laparoscopic cholecystectomy does not increase the risk of SSI (OR: 1.48, 95% CI 0.57-3.86, P = 0.42) and postoperative collection (RD: 0.00, 95% CI - 0.00-0.01, P = 0.41) but may result in longer operative time (MD 10.28 min, 95% CI 7.40-13.16, P < 0.00001) and length of hospital stay (MD 0.51 days, 95% CI 0.15-0.87, P = 0.005). The results remained consistent through sensitivity analyses. The quality of available evidence was judged to be moderate, and the GRADE certainty of the evidence was judged to be high. CONCLUSIONS: The best available evidence suggests that IGP during laparoscopic cholecystectomy may not increase the risk of SSI and postoperative collection but may result in longer operative time and length of hospital stay. Whether prompt retrieval of spilled stones, adequate peritoneal irrigation, and intraoperative use of prophylactic antibiotic contribute to the above findings remains unknown.


Subject(s)
Cholecystectomy, Laparoscopic , Gallbladder Diseases , Cholecystectomy, Laparoscopic/adverse effects , Cholecystectomy, Laparoscopic/methods , Gallbladder Diseases/surgery , Humans , Iatrogenic Disease , Operative Time , Surgical Wound Infection/epidemiology , Surgical Wound Infection/etiology
7.
Eur J Public Health ; 32(1): 133-139, 2022 02 01.
Article in English | MEDLINE | ID: mdl-33999142

ABSTRACT

BACKGROUND: In response to the COVID-19 pandemic, many countries mandated staying at home to reduce transmission. This study examined the association between living arrangements (house occupancy numbers) and outcomes in COVID-19. METHODS: Study population was drawn from the COPE study, a multicentre cohort study. House occupancy was defined as: living alone; living with one other person; living with multiple other people; or living in a nursing/residential home. Outcomes were time from admission to mortality and discharge (Cox regression), and Day 28 mortality (logistic regression) analyses were adjusted for key comorbidities and covariates including admission: age, sex, smoking, heart failure, admission C-reactive protein (CRP), chronic obstructive pulmonary disease, estimated glomerular filtration rate, frailty and others. RESULTS: A total of 1584 patients were included from 13 hospitals across UK and Italy: 676 (42.7%) were female, 907 (57.3%) were male, median age was 74 years (range: 19-101). At 28 days, 502 (31.7%) had died. Median admission CRP was 67, 82, 79.5 and 83 mg/l for those living alone, with someone else, in a house of multiple occupancy and in a nursing/residential home, respectively. Compared to living alone, living with anyone was associated with increased mortality: within a couple [adjusted hazard ratios (aHR) = 1.39, 95% confidence intervals (CI) 1.09-1.77, P = 0.007]; living in a house of multiple occupancy (aHR = 1.67, 95% CI 1.17-2.38, P = 0.005); and living in a residential home (aHR = 1.36, 95% CI 1.03-1.80, P = 0.031). CONCLUSION: For patients hospitalized with COVID-19, those living with one or more people had an increased association with mortality, they also exhibited higher CRP indicating increased disease severity suggesting they delayed seeking care.


Subject(s)
COVID-19 , Aged , Cohort Studies , Female , Hospitalization , Humans , Male , Pandemics , SARS-CoV-2
8.
Nature ; 2021 Mar 31.
Article in English | MEDLINE | ID: mdl-33790436
9.
Int J Epidemiol ; 50(2): 420-429, 2021 05 17.
Article in English | MEDLINE | ID: mdl-33683344

ABSTRACT

BACKGROUND: C-reactive protein (CRP) is a non-specific acute phase reactant elevated in infection or inflammation. Higher levels indicate more severe infection and have been used as an indicator of COVID-19 disease severity. However, the evidence for CRP as a prognostic marker is yet to be determined. The aim of this study is to examine the CRP response in patients hospitalized with COVID-19 and to determine the utility of CRP on admission for predicting inpatient mortality. METHODS: Data were collected between 27 February and 10 June 2020, incorporating two cohorts: the COPE (COVID-19 in Older People) study of 1564 adult patients with a diagnosis of COVID-19 admitted to 11 hospital sites (test cohort) and a later validation cohort of 271 patients. Admission CRP was investigated, and finite mixture models were fit to assess the likely underlying distribution. Further, different prognostic thresholds of CRP were analysed in a time-to-mortality Cox regression to determine a cut-off. Bootstrapping was used to compare model performance [Harrell's C statistic and Akaike information criterion (AIC)]. RESULTS: The test and validation cohort distribution of CRP was not affected by age, and mixture models indicated a bimodal distribution. A threshold cut-off of CRP ≥40 mg/L performed well to predict mortality (and performed similarly to treating CRP as a linear variable). CONCLUSIONS: The distributional characteristics of CRP indicated an optimal cut-off of ≥40 mg/L was associated with mortality. This threshold may assist clinicians in using CRP as an early trigger for enhanced observation, treatment decisions and advanced care planning.


Subject(s)
C-Reactive Protein , COVID-19 , Adult , Aged , Biomarkers , C-Reactive Protein/analysis , Hospitalization , Humans , Prognosis , Retrospective Studies , SARS-CoV-2
10.
Geriatrics (Basel) ; 5(1)2020 Mar 19.
Article in English | MEDLINE | ID: mdl-32204573

ABSTRACT

Older people have a high incidence of adverse outcomes after urgent care presentation. Identifying high-risk older patients early is key to targeting interventions at those patients most likely to benefit. This study used the Frailsafe three-point screening questions amongst older Emergency Department (ED) attendees. Consecutive unplanned ED attendances in patients aged ≥75 were assessed for Frailsafe status. The primary outcome was mortality at 180 days. A Frailsafe screen was completed in 356 patients, of whom 194/356 (54.5%) were Frailsafe positive. The mean age was 85.8 for Frailsafe screen positive and 82.2 for Frailsafe screen negative patients (p < 0.001). A positive Frailsafe screen was a predictor of death within 180 days of presentation to the ED and remained so after adjustment (AOR = 3.23, 95% CI 1.45-7.19, p = 0.004). A positive Frailsafe screen was an independent predictor of a new care home admission at 180 days (AOR = 8.95, 95% CI 2.01-39.83, p = 0.004). A positive Frailsafe screen was also predictive of a number of secondary outcomes, such as length of stay of >28 days (AOR 3.42, 95% CI 1.41-8.31, p = 0.007) and re-attendance within 30 days of discharge after admission (OR = 2.73, 95% CI 1.27-5.88, p = 0.01). Frailsafe screen results independently predict a range of outcomes amongst older ED attendees.

11.
Acta Chir Belg ; 117(6): 370-375, 2017 Dec.
Article in English | MEDLINE | ID: mdl-28602153

ABSTRACT

BACKGROUND: The number of surgical procedures performed in elderly and frail patients has greatly increased in the last decades. However, there is little research in the elderly emergency general surgery patient. The aim of this study was to assess the prevalence of frailty in the emergency general surgery population in Belgium. Secondly, we examined the length of hospital stay, readmission rate and mortality at 30 and 90 days. METHODS: We conducted a prospective observational study at Ghent University Hospital. All patients older than 65 admitted to a general surgery ward from the emergency department were eligible for inclusion. Primary endpoint was mortality at 30 days. Secondary outcomes were mortality at 90 days, readmissions and length of stay. Cross-sectional observations were performed using the Fisher exact test, Mann-Whitney U-test, or one-way ANOVA. We performed a COX multivariable analysis to identify independent variables associated with mortality at 30 and 90 days as well as the readmission risk. RESULTS: Data were collected from 98 patients in a four-month period. 23.5% of patients were deemed frail. 79% of all patients underwent abdominal surgery. Univariate analyses showed that polypharmacy, multimorbidity, a history of falls, hearing impairment and urinary incontinence were statistically significantly different between the non-frail and the group. Frail patients showed a higher incidence for mortality within 30 days (9% versus 1.3% (p = .053)). There were no differences between the two groups for mortality at 90 days, readmission, length of stay and operation. Frailty was a predictor for mortality at 90 days (p= .025) (hazard ratio (HR) 10.83 (95%CI 1.34-87.4)). Operation (p= .084) (HR 0.16 (95%CI 0.16-1.29)) and the presence of chronic cardiac failure (p= .049) (HR 0.38 (95%CI 0.14-0.99)) were protective for mortality at 90 days. CONCLUSION: Frailty is a significant predictor for mortality for elderly patients undergoing emergency abdominal/general surgery. LEVEL OF EVIDENCE: Level II therapeutic study.


Subject(s)
Abdomen, Acute/mortality , Abdomen, Acute/surgery , Emergencies , Frail Elderly , Frailty , Surgery Department, Hospital , Aged , Belgium , Female , Follow-Up Studies , Geriatric Assessment , Hospitals, University , Humans , Male , Patient Readmission , Predictive Value of Tests , Prospective Studies , Surgical Procedures, Operative/methods , Treatment Outcome
12.
Ecotoxicol Environ Saf ; 72(8): 2046-57, 2009 11.
Article in English | MEDLINE | ID: mdl-19767103

ABSTRACT

Pit lakes are increasingly common worldwide and have potential to provide many benefits. However, lake water toxicity may require remediation before beneficial end uses can be realised. Three treatments to remediate AMD (pH approximately 4.8) pit lake water containing elevated concentrations of Al and Zn from Collie, Western Australia were tested in mesocosms. Treatments were: (a) limestone neutralisation (L), (b) phosphorus amendment (P), and (c) combined limestone neutralisation and phosphorus amendment (L+P). Laboratory bioassays with Ceriodaphnia cf. dubia, Chlorella protothecoides and Tetrahymena thermophila assessed remediation. Limestone neutralisation increased pH and reduced heavy metal concentrations by 98% (Al) to 14% (Mg), removing toxicity to the three test species within 2 months. Phosphorus amendment removed toxicity after 6 months of treatment. However, phosphorus amendment to prior limestone neutralisation failed to reduce toxicity more than limestone neutralisation alone. Low concentrations of both phosphorus and nitrogen appear to limit phytoplankton population growth in all treatments.


Subject(s)
Calcium Carbonate/chemistry , Environmental Restoration and Remediation/methods , Fresh Water/chemistry , Metals, Heavy/toxicity , Phosphorus/chemistry , Water Pollutants, Chemical/toxicity , Acids/analysis , Acids/toxicity , Aluminum/analysis , Aluminum/toxicity , Biological Assay , Environmental Monitoring , Hydrogen-Ion Concentration , Kinetics , Metals, Heavy/analysis , Mining , Nitrogen/analysis , Phosphorus/analysis , Phytoplankton/drug effects , Phytoplankton/growth & development , Phytoplankton/metabolism , Toxicity Tests, Chronic , Water Pollutants, Chemical/analysis , Zinc/analysis , Zinc/toxicity
13.
Article in English | MEDLINE | ID: mdl-16473031

ABSTRACT

Live holding of lobsters is a major part of the post-harvest process in lobster fisheries. Following capture, animals are placed in factory tanks and held for varying lengths of time for recovery from stress due to handling, air exposure, disturbance and environmental variations. The aim of the present study was to determine the pattern of response of a range of immune and physiological parameters over varying holding periods and assess their possible application as a measure of recovery from stress of post-harvest procedures and in the determination of an appropriate duration of acclimation prior to live transport. The effect of holding duration on the following immune parameters: total haemocyte counts (THC), haemolymph clotting times, haemolymph pH, haemolymph protein concentration and the differential proportion of haemocytes, was assessed. Lobsters brought to the factory were placed in holding tanks and sampled over a period of up to 10 days. Two studies were conducted, the first on lobsters from different catch groups and the second on lobsters from the same day's catch from the same area. Experiments were conducted on adult animals (10-12 animals/treatment group) with a different group of lobsters being sampled at each time point. Various immune parameters showed alterations with time during holding. A consistent observation was significantly prolonged clotting times following four days of holding. The haemolymph pH showed a strong positive correlation to clotting time and the hyaline cell proportion showed a strong negative correlation with semi-granular cells. Although the levels of THC, clotting time and differential cell counts after one day of holding were similar to those observed in other studies on rested post-harvest lobsters, suggesting that the lobsters had recovered from the acute stress of capture and transport, subsequent alterations in pH, clotting time and differential cell counts indicated other physiological adjustments were still occurring for up to 4 days post capture. Overall the results suggest that though the effects of post-harvest procedures on the immune parameters appear to be resolved after a short duration of holding at low temperatures, no single immune parameter can provide predictable indication of the acclimation process.


Subject(s)
Immune System/physiology , Palinuridae/physiology , Adaptation, Physiological , Animals , Cell Count , Hemocytes/cytology , Hemocytes/physiology , Hemolymph/microbiology , Hemolymph/physiology , Hyalin/metabolism , Hydrogen-Ion Concentration , Proteins/analysis , Proteins/metabolism , Stress, Physiological , Time Factors
14.
Mar Pollut Bull ; 45(1-12): 148-56, 2002.
Article in English | MEDLINE | ID: mdl-12398379

ABSTRACT

Crude oils produced in the North West shelf of Western Australia are highly volatile, a characteristic not shared by most of the Northern Hemisphere crude oils on which internationally accepted toxicity test protocols were developed. Because of this volatility and some other factors, the LC50 and EC50 values obtained from acute toxicity tests will be significantly affected by the changes of toxicant concentration in test solutions during the period of exposure. To address these issues all steps of a standard protocol for crude oil toxicity testing have been revised. A systematic study has been performed on factors which affect petroleum hydrocarbon solubilisation in aqueous systems during test solution preparations. The influence of mixing time, agitation energy and volume/ interface ratio on a hydrocarbon concentration in a water-soluble fraction (WSF) was studied for heavy, medium and light crude oils. A study of the sensitivity of marine unicellular algae to WSF of crude oils was conducted with Isochrysis sp., Nannochloropsis-like sp. and Nitzchia closterium. Total concentrations of hydrocarbons dissolved in test solutions were estimated by UV-spectrometry and GC/FID chemical analyses. When the toxicant concentration decreased during the exposure period, the EC50 values derived from initial or final concentrations either underestimate or overestimate toxicity, respectively. Therefore, weighted average concentrations (WAC) calculated for the whole test period were recommended for expressing hydrocarbon concentrations in test solutions of crude oils. Toxicity indices calculated from WAC of total hydrocarbons for different crude oils can be compared regardless of the rates of hydrocarbon loss.


Subject(s)
Eukaryota , Hydrocarbons/toxicity , Petroleum , Water Pollutants/toxicity , Hydrocarbons/chemistry , Lethal Dose 50 , Reproducibility of Results , Research Design , Specimen Handling
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