Prevalence and predictors of severe Crohn's disease at a tertiary hospital in South Africa.

Background Predicting severe Crohn's disease (SCD) can assist in planning risk reduction therapy for SCD, thereby improving disease outcomes. Objective To determine the prevalence and predictors of SCD in a sample of South African patients. Methods This was a retrospective chart review of patients with Crohn's disease (CD) attending the Gastroenterology Unit at a tertiary hospital in Durban, South Africa. Demographic and clinical variables at diagnosis of CD were collected and analysed for statistical association with development of SCD (defined as the presence of >/= 1 of the following over the course of CD: complex perianal disease, colonic resection >/= 2 small bowel resections, a single small bowel resection > 50cm, or construction of a definitive stoma). The prognostic utility of statistically significant variables was investigated by establishing their sensitivity, specificity, and predictive values for SCD.  Results The study consisted of 93 patients. The rate of SCD was 64.5%, with 63.3 % of patients developing SCD within 1 year of CD diagnosis. Ileocolonic location (p = 0.046) and penetrating disease at initial diagnosis of CD (p = 0.021) were statistically associated with SCD. The sensitivity, specificity, positive predictive value, and negative predictive value of ileocolonic location for SCD was 72.7%, 47.4%, 66.7% and 54.6%. The sensitivity, specificity, positive predictive value, and negative predictive value of penetrating disease for SCD was 85.7%, 41.7%, 30.0% and 91.0%. Conclusion Most patients with CD developed SCD within 1 year of their CD diagnosis. CD with a penetrating phenotype at diagnosis is a good predictor for the devleopment of SCD and should be further investigated.

The clinicopathological spectrum and treatment outcomes in metastatic colorectal cancer in the KwaZulu-Natal province of South Africa.

BACKGROUND: In high-income countries (HICs) 17-20% of colorectal cancer (CRC) patients have metastatic CRC (mCRC) at the time of diagnosis, of which 10-25% are or become resectable, and a further 4-11% of patients will develop metachronous metastases. The study aimed to establish the prevalence and pattern of metastatic CRC to document treatment outcomes in KwaZulu-Natal (KZN), and to compare results to international norms. METHODS: The study population comprised patients with mCRC presenting between 2000 and 2019. Demographics, primary tumour site, spectrum of metastatic disease and resection rate were assessed. RESULTS: MCRC occurred in 33% of the CRC patient population. Eight hundred and thirty-six patients had metastatic disease, comprising Africans (325, 38.8%), Indians (312, 37.3%), Coloureds (37, 4.4%) and Whites (161, 19.2%). Six hundred and fifty-four patients (79%) had synchronous metastases and 182 patients had metachronous metastases (21%). Single organ metastases occurred in 596 patients (71.2%) (M1A) and multiple organ metastasis occurred in 240 patients (28.7%) (M1B). Metastases occurred in the liver (613), lung (240) and peritoneum (85). Fifty-two patients (6.2%) underwent resection of their metastases. CONCLUSION: The prevalence of stage IV CRC in our setting is at the upper limit of international norms. mCRC occurred in 33%, with similar proportions in all races. Resection rate for metastases is low.

A South African central hospital's experience with malignant colorectal obstruction.

BACKGROUND: The spectrum and outcome of colorectal cancer (CRC) presenting with obstruction is not well studied in low- to middle-income countries (LMIC) and could have implications for health policy. This study aimed to address this deficit in an LMIC setting. METHODS: A retrospective analysis was conducted of patients with large bowel obstruction, during the period 2000-2019 from the prospective Inkosi Albert Luthuli Central Hospital (IALCH) CRC registry data. Data analysed included the site of CRC, tumour differentiation, management of patients with obstructive CRC, resection margins post resection, oncological management and reasons for failure to receive oncological therapy. Patient follow-up and recurrence were recorded. RESULTS: Malignant obstruction from CRC occurred in 510 patients (20% of the CRC registry). Median age at presentation was 57 years (IQR 48-67). One hundred and seventy-six (34.5%) and 135 (26.5%) had stage III and IV disease respectively. Moderately differentiated cancer was seen in 335 (65.6%). Management was resection (370; 72.5%), diverting colostomy (123; 24.1%) and stent insertion (55; 10.8%). Twenty-one patients (5.7%) had positive resection margins. Recurrence occurred in 34 patients (6.7%), all of whom had initially undergone resection, giving a recurrence rate of 9.8% in those receiving surgery. Median disease-free interval for patients developing recurrence was 21 months (IQR 12-32). CONCLUSION: One in five patients with CRC presented with obstruction. These patients were younger than in high incomecountry (HIC) series. Over 70% underwent resection. Stomas were used twice as frequently as stents to relieve the obstruction, a finding that is the reverse of that in HICs.

Outcomes of haemorrhagic radiation proctitis at a South African tertiary hospital.

BACKGROUND: Haemorrhagic radiation proctitis occurs in 5-10% of patients undergoing radiotherapy. In our resourceconstrained South African setting, this study aimed to describe the clinicopathological spectrum and management of radiation proctitis referred to a tertiary centre, to address the deficit in our setting-specific understanding of the condition. METHODS: This was a sub-analysis of data from an existing colorectal cancer registry at the Inkosi Albert Luthuli Central Hospital in Durban. We reviewed the registry for all patients between 2008 and 2019 with haemorrhagic radiation proctitis and describe the various patient characteristics, treatments and outcomes for these patients. RESULTS: Fifty-eight patients with haemorrhagic radiation proctitis were identified. Colonoscopy findings included bleeding (58 patients), endoscopic proctitis (30 patients) and rectal stricture (7 patients). The median time elapsed between radiotherapy and development of symptoms was 16.5 months (IQR 12-25). Median number of argon plasma coagulation (APC) sessions for endoscopic healing or symptom resolution was three sessions (IQR 2-4). At follow-up, 35 patients had complete healing and 19 patients had symptom improvement. Complications occurring during or after APC therapy included rectal ulceration (2 patients) and rectovaginal fistula (1 patient). CONCLUSION: APC is a safe and effective treatment modality with complete resolution or significant improvement in symptomatology in the vast majority of patients with three or four treatments. Morbidity is likely to be related to ongoing radiation effects.

Quantifying the relationship of HIV infection with clinicopathological spectrum and outcome among patients with colorectal cancer in a South African population.

Introduction: Literature is limited on HIV and colorectal cancer (CRC) in sub-Saharan Africa despite it being the epicentre of the HIV epidemic. Purpose: To compare clinicopathological features and outcome of CRC in HIV-negative and HIV-positive patients. Methods: Retrospective analysis of a prospective CRC database. Demographic details, HIV status, anatomical site, disease stage, treatment and follow-up were documented. Results: Of 715 patients with CRC, 145 and 570 tested positive and negative respectively for HIV. Median age was 45 (IQR 36-53 and 57 (IQR 45-66) years among HIV-positive and HIV-negative patients respectively (p<0.0001). Tumour differentiation differed between the two groups (p=0.003) but staging was not different (p=0.6). Surgical resection rate was 52% for HIV-positive patients versus 59% for HIV-negative patients (p=0.07). Median follow-up was 9 (IQR 2-20.5) months for HIV-positive patients and 12 (IQR 6-29) months for HIV-negative patients (p=0.154). Recurrence rate was 14.7% among HIV positive patients and 6.8% in HIV negative patients (p=0.089). Conclusion: When compared with HIV-negative patients, HIV-positive patients with CRC presented at a younger age and tended to have lower surgical resection rates. There was no difference between the two groups with CRC in terms of anatomical sub-site distribution, disease staging and recurrence rates.

Risk factors associated with unplanned ICU admissions following paediatric surgery: A systematic review.

Background: Unplanned admissions to the intensive care unit (ICU) have important implications in the general management of patients. Research in this area has been conducted in the adult and non-surgical population. To date, there is no systematic review addressing risk factors in the paediatric surgical population. Objectives: To synthesise the information from studies that explore the risk factors associated with unplanned ICU admissions following surgery in children through a systematic review process. Methods: We conducted a systematic review of published literature (PROSPERO registration CRD42020163766), adhering to the Preferred Reporting of Observational Studies and Meta-Analysis (PRISMA) statement. The Population, Exposure, Comparator, Outcome (PECO) strategy used was based on: population - paediatric population, exposure - risk factors, comparator - other, and outcome - unplanned ICU admission. Data that reported on unplanned ICU admissions following paediatric surgery were extracted and analysed. Quality of the studies was assessed using the Newcastle-Ottawa Scale. Results: Seven studies were included in the data synthesis. Four studies were of good quality with the Newcastle-Ottawa Scale score ≥7 points. The pooled prevalence (95% confidence interval) estimate of unplanned ICU stay was 2.69% (0.05 - 8.6%) and ranged between 0.06% and 8.3%. Significant risk factors included abnormal sleep studies and the presence of comorbidities in adenotonsillectomy surgery. In the general surgical population, younger age, comorbidities and general anaesthesia were significant. Abdominal surgery and ear, nose and throat (ENT) surgery resulted in a higher risk of unplanned ICU admission. Owing to the heterogeneity of the data, a meta-analysis with risk prediction could not be performed. Conclusion: Significant patient, surgical and anaesthetic risk factors associated with unplanned ICU admission in children following surgery are described in this systematic review. A combination of these factors may direct planning toward anticipation of the need for a higher level of postoperative care. Further work to develop a predictive score for unplanned ICU stay is desirable. Contributions of the study: Unplanned admissions to the intensive care unit (ICU) have been acknowledged as an overall marker of safety.[1] Awareness of this concept has encouraged research to determine the incidence and risk factors of these occurrences. This research has been interrogated in a systematic review process with beneficial conclusions drawn; however, these studies included adults and non-surgical patients.[2-4] To date, we have not been able to find a systematic review addressing the risk factors associated with unplanned ICU admissions in paediatric surgical patients.

Quantifying the relationship of HIV infection with clinicopathological spectrum and outcome among patients with colorectal cancer in a South African population

Introduction: Literature is limited on HIV and colorectal cancer (CRC) in sub-Saharan Africa despite it being the epicentre of the HIV epidemic, Purpose: To compare clinicopathological features and outcome of CRC in HIV-negative and HIV-positive patients. Methods: Retrospective analysis of a prospective CRC database. Demographic details, HIV status, anatomical site, disease stage, treatment and follow-up were documented. Results: Of 715 patients with CRC, 145 and 570 tested positive and negative respectively for HIV. Median age was 45 (IQR 36-53 and 57 (IQR 45-66) years among HIV-positive and HIV-negative patients respectively (p<0.0001). Tumour differentiation differed between the two groups (p=0.003) but staging was not different (p=0.6). Surgical resection rate was 52% for HIV-positive patients versus 59% for HIV-negative patients (p=0.07). Median follow-up was 9 (IQR 2-20.5) months for HIV-positive patients and 12 (IQR 6-29) months for HIV-negative patients (p=0.154). Recurrence rate was 14.7% among HIV positive patients and 6.8% in HIV negative patients (p=0.089). Conclusion: When compared with HIV-negative patients, HIV-positive patients with CRC presented at a younger age and tended to have lower surgical resection rates. There was no difference between the two groups with CRC in terms of anatomical sub-site distribution, disease staging and recurrence rates

Age is a predictor of significant endoscopic findings in dyspepsia patients in South Africa.

BACKGROUND: Dyspepsia is the commonest indication for endoscopy. Current American guidelines recommend that all dyspepsia patients ≥ 60 years undergo endoscopy to exclude significant pathology. The use of this age cut-off has never been analysed in South Africa. We aimed to compare different age cut-offs as predictors of significant endoscopic findings in patients with a primary diagnosis of dyspepsia. METHODS: A retrospective chart review of 1 000 consecutive endoscopies done at Madadeni Provincial Hospital, KwaZulu-Natal, from 2014 to 2016 was performed. All patients with dyspepsia were identified and divided into age ≥ 60 and < 60 cohorts and < 45 and ≥ 45 cohorts. Demographic data, significant endoscopic findings (tumour, ulcer, and stricture) and non-significant findings (gastritis, hiatus hernia, candidiasis, and oesophagitis, normal) were recorded. RESULTS: 584 patients (58.4%) presented with dyspepsia, with a median age of 49 years (interquartile range: 14-87). There were 142 males (24.4%) and 442 females (75.6%). 432 (74%) patients in the age < 60 cohort and 152 (26%) in the age ≥ 60 cohort . There were 238 (41%) patients in the < 45 cohort and 346 (59%) patients in the ≥ 45 cohort. In the age < 60 cohort, 6.7% of patients had significant findings, compared to 17.1% of patients in the age ≥ 60 cohort (p-value < 0.001). In the age ≥ 60 cohort, the positive predictive value (PPV) of endoscopy was 17%, negative predictive value (NPV) (93%) and odds ratio (OR) (2.87) p < 0.001. In the age < 45 cohort, 4.2% of patients had significant findings, compared to 13% of patients in the ≥ 45 cohort (p-value < 0.001). In the age ≥ 45 cohort, the PPV was 13%, NPV (96%) and OR (3.41) p < 0.001. There is no overall difference in significant endoscopic findings between the age ≥ 45 and age ≥ 60 groups (p = 0.230). CONCLUSION: Age is a predictor of significant endoscopic findings in dyspepsia patients. Patients ≥ 60 years with dyspepsia symptoms should undergo a routine endoscopy in the absence of alarm symptoms. The current ACG guidelines can be applied in the South African context.

Alarm features as predictors of major findings in a rural South African upper endoscopic service.

BACKGROUND: Alarm features are commonly used to identify patients who require an endoscopy to rule out significant upper-gastrointestinal (GI) pathology. Validation of these features in a rural South African (SA) setting has implications for the provision of endoscopy services and was the aim of this study. METHODS: This was a retrospective chart review of 1 000 consecutive endoscopies performed at a rural SA regional/ referral hospital over three years. Demographic data, indication for endoscopy (upper GI bleed, dyspepsia, dysphagia, anaemia, weight loss, age) and major endoscopic findings (defined any tumour, ulcer, or stricture) were recorded. A multivariate logistic regression analysis was done to identify risk factors for major endoscopic findings. RESULTS: The median age of the study sample was 51.0 (range14.0-88.0) years. Males (306/1 000) accounted for 30.6% of the study population. The prevalence of alarm features in the study sample was as follows: upper GI bleed - 16.6%; dyspepsia - 58.4%; dysphagia - 10.3%; anaemia - 3.5%; weight loss - 0.3%. The following alarm features were statistically significant in detecting a major endoscopic finding: age > 60 (OR: 2.67, CI: 1.82-3.96), male gender (OR: 1.52, CI: 1.03-2.24), dysphagia (OR: 12.16, CI: 4.33-34.19) and upper GI bleed (OR: 2.77, CI: 1.03-7.47), p < 0.05. CONCLUSION: Dysphagia, age > 60, male gender, and upper GI bleed are identifiable risk factors for major endoscopic findings. Not all the alarm features for major endoscopic findings that are established elsewhere can be applied in our rural SA setting.

Admissions for post-discharge surgical site infection at a quaternary South African public sector hospital.

BACKGROUND: Reports of post-discharge admissions for surgical site infection (SSI) in African settings are lacking. This information could assist with allocating resources within hospitals, as well as developing targeted interventions aimed at reducing post-discharge SSI. The primary objective of this study was to determine trends in admissions for post-discharge SSI at a South African quaternary/teaching hospital. The secondary objective was to determine trends in mortality rates for these admissions. METHODS: This was a retrospective review of adult admissions for post-discharge SSI at a quaternary/teaching South African hospital between 2006 and 2015. Admissions for post-discharge SSI were identified using the hospital administrative database and appropriate International Classification of Disease, 10th Revision codes. Mortality was determined from the discharge disposition for each admission. Data were analysed with simple regression and trend line statistics. The geospatial distribution of post-discharge SSI, based on the residential postal codes recorded on the hospital administrative database for each admission, was determined using the Power Map® software program. RESULTS: There was no change in admissions for post-discharge SSI over the study period (p = 0.17). Mortality in elderly admissions declined during the study period (p = 0.03). Most admissions for post-discharge SSIs originated from urban areas. CONCLUSION: Despite the implementation of universal SSI prevention methods, admissions for post-discharge SSI remained consistent during the study period. Urban areas appeared to be more.

General attitudes toward research: a pilot survey of HIV-positive surgical patients.

BACKGROUND: The general attitude of HIV-positive surgical patients toward research has not been described, and it is uncertain whether interventions aimed at improving general attitudes toward research are required in this group. The aim of this pilot survey was to address the aforementioned paucity in the literature. METHOD: This was a prospective survey of 39 HIV-positive surgical patients. The 7-item Research Attitudes Questionnaire (RAQ) and a demographic characteristics questionnaire were administered to each study participant. Likert responses for the RAQ were converted into numeric values, and cumulative research attitude scores were computed for each study participant. A descriptive analysis of study participant responses to the RAQ was performed. Statistical associations between demographic characteristics and cumulative research attitude scores were also assessed. RESULTS: Depending on the RAQ item, between 74.3% and 95.9% of study participants responded positively toward research. Negative responses ranged between 0.0% and 10.3%, while neutral responses to RAQ items ranged between 2.6% and 23.1%. Female study participants had lower median research attitudes scores when compared with their male counterparts (p = 0.014). CONCLUSION: In general, study participants expressed a positive attitude toward research. The proportion of neutral responses for some RAQ items suggests there are certain aspects of research which require clarification to prospective research participants. Efforts should be made to improve female HIV-positive surgical patients' overall attitude toward research.

A standardised protocol for the evaluation of small extracellular vesicles in plasma by imaging flow cytometry.

Flow cytometry provides robust, multi-parametric and quantitative information on single cells which also exhibits enormous potential as a tool for small particle characterisation. Small extracellular vesicle (sEV) detection by flow cytometry remains compromised due to the high prevalence of swarm detection, which is defined by the simultaneous illumination of more than one sEV, recorded as a single event. Detection of sEVs by imaging flow cytometry presents a major advantage by having the ability to resolve single particles from swarm detection based on the image features recorded for each event. In this study, we provide a simplified protocol that facilitates the removal of both swarm events and aggregated particles to improve the accuracy of sEV analysis. Our results indicate that imaging flow cytometry should be at the forefront as a robust and sensitive technique for sEV characterisation.

Preoperative serum sodium measurements and postoperative inpatient mortality: A case-control analysis of data from the South African Surgical Outcomes Study.

BACKGROUND: Abnormal preoperative serum sodium measurements have been shown to be associated with increased postoperative mortality in US and European surgical populations. It is possible that such measurements are also associated with increased postoperative mortality in a South African (SA) setting, but this is yet to be confirmed. Establishing whether preoperative serum sodium measurements are associated with postoperative mortality could have implications for perioperative risk stratification in SA settings. OBJECTIVES: To determine whether preoperative serum sodium measurements are associated with postoperative mortality in SA surgical patients. METHODS: This was an unmatched case-control study of patient data (demographics, comorbidities, procedure-related variables, and preoperative serum sodium measurements) collected during the South African Surgical Outcomes Study. Data were analysed using recommended statistical methods for unmatched case-control studies. RESULTS: The study population comprised 103 patients and 410 controls. Cases were defined as patients who suffered postoperative inpatient mortality, while controls were defined as patients who did not suffer postoperative inpatient mortality. Preoperative hypernatraemia (i.e. a preoperative serum sodium measurement >144 mEq/L) was independently associated with a four-fold higher risk of postoperative inpatient mortality compared with a normal preoperative serum sodium measurement of 135 - 144 mEq/L (odds ratio (OR) 4.21, 95% confidence interval (CI) 1.19 - 14.83, p=0.025). Preoperative hyponatraemia (i.e. a preoperative serum sodium measurement <135 mEq/L) was not independently associated with a higher or lower risk of postoperative inpatient mortality compared with a normal preoperative serum sodium measurement (OR 1.39, 95% CI 0.70 - 2.76, p=0.346). CONCLUSIONS: Preoperative hypernatraemia, but not preoperative hyponatraemia, is a risk factor for postoperative inpatient mortality in SA surgical patients.

Preoperative serum sodium measurements and postoperative inpatient mortality: A case-control analysis of data from the South African Surgical Outcomes Study

Background. Abnormal preoperative serum sodium measurements have been shown to be associated with increased postoperative mortality in US and European surgical populations. It is possible that such measurements are also associated with increased postoperative mortality in a South African (SA) setting, but this is yet to be confirmed. Establishing whether preoperative serum sodium measurements are associated with postoperative mortality could have implications for perioperative risk stratification in SA settings.Objectives. To determine whether preoperative serum sodium measurements are associated with postoperative mortality in SA surgical patients.Methods. This was an unmatched case-control study of patient data (demographics, comorbidities, procedure-related variables, and preoperative serum sodium measurements) collected during the South African Surgical Outcomes Study. Data were analysed using recommended statistical methods for unmatched case-control studies.Results. The study population comprised 103 patients and 410 controls. Cases were defined as patients who suffered postoperative inpatient mortality, while controls were defined as patients who did not suffer postoperative inpatient mortality. Preoperative hypernatraemia (i.e. a preoperative serum sodium measurement >144 mEq/L) was independently associated with a four-fold higher risk of postoperative inpatient mortality compared with a normal preoperative serum sodium measurement of 135 - 144 mEq/L (odds ratio (OR) 4.21, 95% confidence interval (CI) 1.19 - 14.83, p=0.025). Preoperative hyponatraemia (i.e. a preoperative serum sodium measurement <135 mEq/L) was not independently associated with a higher or lower risk of postoperative inpatient mortality compared with a normal preoperative serum sodium measurement (OR 1.39, 95% CI 0.70 - 2.76, p=0.346).Conclusions. Preoperative hypernatraemia, but not preoperative hyponatraemia, is a risk factor for postoperative inpatient mortality in SA surgical patients

Major histocompatibility complex genes partly explain early survival in house sparrows.

Environmental factors and genetic incompatibilities between parents have been suggested as important determinants for embryonic mortality and survival. The genetic set-up of the immune system, specifically the highly polymorphic major histocompatibility complex (MHC) may also influence individual resistance to infections. MHC proteins are important for an appropriate adaptive immune response and enable T-cells to separate 'self' from 'non-self'. Here we investigate the importance of MHC functional diversity for early development in birds, more specifically, if offspring survival and body mass or size depends on number of different functional MHC alleles, specific functional MHC alleles or similarity of MHC alleles in the parents. Unhatched eggs are common in clutches of many bird species. In house sparrows (Passer domesticus), embryo and nestling mortality can exceed 50%. To control for environmental factors, our study was carried out on an aviary population. We found that one specific functional MHC allele was associated with reduced nestling survival, which was additionally supported by lower body mass and a smaller tarsus when nestlings have been 6 days old. Another allele was positively associated with tarsus length at a later nestling stage (nestlings 12 days old). These results indicate that MHC alleles might influence pathogen resistance or susceptibility.

Integrated multidisciplinary community service for chronic obstructive pulmonary disease reduces hospitalisations.

BACKGROUND: Hospitalisations for chronic obstructive pulmonary disease (COPD) exacerbation affect patient outcomes and healthcare costs. The long-term impact of an integrated COPD disease-management approach on hospitalisation remains controversial. AIM: The aim of this study was to evaluate whether a multidisciplinary community service reduces respiratory hospitalisations for COPD patients. METHODS: A total of 346 patients was followed for a mean duration of 27.3 months. The number of admissions, total bed days for respiratory (COPD exacerbation or pneumonia) or general medical causes and length of stay (LOS) per respiratory admission was compared before and after referral with the service. A secondary multivariate analysis examined which clinical parameters best predict benefit from such service. RESULTS: The total respiratory admission and hospital bed days after referral were reduced by 31% (288 vs 417, P < 0.001) and 40.4% (1637 vs 2746, P < 0.0001) respectively, compared with the equivalent duration prior. The average LOS for each respiratory admission was also significantly reduced after referral (6.61 vs 5.70, P = 0.02). Overall, 55% patients experienced a reduction in admission frequency and hospital days. The impact on admission frequency and hospital days was the greatest in those with an at least moderate disease (GOLD ≥2, odds ratio (OR): 3.2, 95% confidence interval (CI): 1.2, 8.9; P = 0.019) and those who completed pulmonary rehabilitation (PR) (OR: 1.7, 95% CI: 1.1, 2.8; P = 0.04). In contrast, general medical admissions increased, one-third attributable to a cardiovascular cause both before and after referral. CONCLUSIONS: The implementation of COPD multidisciplinary community service was associated with reduced respiratory hospitalisations in the long term. Patients with moderate or severe disease and who are able to complete PR are much more likely to benefit.

The impact of acute preoperative beta- blockade on perioperative cardiac morbidity and all-cause mortality in hypertensive South African vascular surgery patients.

BACKGROUND: Acute ß-blockade has been associated with poor perioperative outcomes in non-cardiac surgery patients, probably as a result of P-blocker-induced haemodynamic instability during the perioperative period, which has been shown to be more severe in hypertensive patients. OBJECTIVE: To determine the impact of acute preoperative ß-blockade on the incidence of perioperative cardiovascular morbidity and all-cause mortality in hypertensive South African (SA) patients who underwent vascular surgery at a tertiary hospital. METHODS: We conducted two separate case-control analyses to determine the impact of acute preoperative ß-blockade on the incidence of major adverse cardiovascular events (MACEs, a composite outcome of a perioperative troponin-I leak or all-cause mortality) and perioperative troponin-I leak alone. Case and control groups were compared using χ2, Fisher's exact, McNemar's or Student's t-tests, where applicable. Binary logistic regression was used to determine whether acute preoperative -blocker use was an independent predictor of perioperative MACEs/troponin-I leak in hypertensive SA vascular surgery patients. RESULTS: We found acute preoperative ß-blockade to be an independent predictor of perioperative MACEs (odds ratio (OR) 3.496; 95% confidence interval (CI) 1.948 - 6.273; p<0.001) and troponin-I leak (OR 5.962; 95% CI 3.085 - 11.52; p<0.001) in hypertensive SA vascular surgery patients. CONCLUSIONS: Our findings suggest that acute preoperative ß-blockade is associated with an increased risk of perioperative cardiac morbidity and all-cause mortality in hypertensive SA vascular surgery patients.

Selection from parasites favours immunogenetic diversity but not divergence among locally adapted host populations.

The unprecedented polymorphism in the major histocompatibility complex (MHC) genes is thought to be maintained by balancing selection from parasites. However, do parasites also drive divergence at MHC loci between host populations, or do the effects of balancing selection maintain similarities among populations? We examined MHC variation in populations of the livebearing fish Poecilia mexicana and characterized their parasite communities. Poecilia mexicana populations in the Cueva del Azufre system are locally adapted to darkness and the presence of toxic hydrogen sulphide, representing highly divergent ecotypes or incipient species. Parasite communities differed significantly across populations, and populations with higher parasite loads had higher levels of diversity at class II MHC genes. However, despite different parasite communities, marked divergence in adaptive traits and in neutral genetic markers, we found MHC alleles to be remarkably similar among host populations. Our findings indicate that balancing selection from parasites maintains immunogenetic diversity of hosts, but this process does not promote MHC divergence in this system. On the contrary, we suggest that balancing selection on immunogenetic loci may outweigh divergent selection causing divergence, thereby hindering host divergence and speciation. Our findings support the hypothesis that balancing selection maintains MHC similarities among lineages during and after speciation (trans-species evolution).