Anthropogenic change decouples a freshwater predator's density feedback.

Intraspecific interactions within predator populations can affect predator-prey dynamics and community structure, highlighting the need to better understand how these interactions respond to anthropogenic change. To this end, we used a half-century (1969-2018) of abundance and size-at-age data from Lake Erie's walleye (Sander vitreus) population to determine how anthropogenic alterations have influenced intraspecific interactions. Before the 1980s, the length-at-age of younger walleye (ages 1 and 2) negatively correlated with older (age 3 +) walleye abundance, signaling a 'density feedback' in which intraspecific competition limited growth. However, after the early 1980s this signal of intraspecific competition disappeared. This decoupling of the density feedback was related to multiple anthropogenic changes, including a larger walleye population resulting from better fisheries management, planned nutrient reductions to improve water quality and transparency, warmer water temperatures, and the proliferation of a non-native fish with novel traits (white perch, Morone americana). We argue that these changes may have reduced competitive interactions by reducing the spatial overlap between older and younger walleye and by introducing novel prey. Our findings illustrate the potential for anthropogenic change to diminish density dependent intraspecific interactions within top predator populations, which has important ramifications for predicting predator dynamics and managing natural resources.

Positive fluid balance is associated with complications after elective open infrarenal abdominal aortic aneurysm repair.

BACKGROUND: Open abdominal aortic aneurysm (AAA) repair is associated with cardiac and respiratory complications and an overall mortality rate of 2 to 8%. We hypothesised that excessive fluid administration during the perioperative period contributes to complications and poor outcome after AAA repair. METHODS: This was a retrospective cohort study. Medical records were analysed for fluid balance and complications in 100 consecutive patients treated by open AAA repair at a single centre between 2002-2005. Mortality and all major adverse events (MAE) such as myocardial infarction (MI), cardiac arrhythmia (Arr), pulmonary oedema (PO), pulmonary infection (PI), and acute renal failure (ARF) were included in the analysis. Level of care and hospital stay, were also recorded. RESULTS: There were no in-hospital deaths. MAE occurred in 40/100 (40%): MI (6%); Arr (14%); PO (14%); PI (25%); ARF (8%). Complications were not predicted by preoperative cardiovascular risk factors, operative and clamp time, or blood loss. Patients with complications had significantly greater cumulative positive fluid balance on postoperative day 0 (p<0.01), day 1 (p<0.05), day 2 (p<0.03) and day 3 (p<0.04). This relationship also existed for individual complications such as MI, and pulmonary oedema. These patients had significantly longer ICU/HDU (p<0.002) and hospital stay (p<0.0001). CONCLUSIONS: Serious complications are common after elective open AAA repair, and we have shown that positive fluid balance is predictive of major adverse events increased HDU/ICU and overall hospital stay.

The Belfast approach to managing complex lower limb vascular injuries.

INTRODUCTION: Complex lower limb vascular injuries (CLVIs) in high-energy penetrating or blunt trauma are associated with an unacceptably high incidence of complications including amputation. Traumatic ischaemia and ischaemia-reperfusion injury (IRI) of skeletal muscle often lead to limb loss, the systemic inflammatory response syndrome (SIRS) which affects remote organs and even the potentially fatal multiple organ dysfunction syndrome (MODS). Surgical care of CLVIs everywhere, including Northern Ireland until 1978, was governed by an anxiety to restore arterial flow quickly often using expedient and flawed repair techniques while a damaged major vein was frequently ligated. MATERIALS AND METHODS: A new policy centred on early intraluminal shunting of both artery and vein, restoring arterial inflow and venous outflow, respectively, was introduced at the Regional Vascular Surgery Unit of The Royal Victoria Hospital, Belfast in 1979. It imposed a disciplined one-stage comprehensive approach to treatment involving a sequence of operative manoeuvres in which all damaged anatomical elements receive meticulous and optimal attention unshackled by time constraints. RESULTS: Comparisons drawn between the pre-shunt period of unplanned treatment (1969-1978) and the post-shunt period centred on the use of shunts (1979-2000) showed that early shunting of both artery and vein in both penetrating (P) and blunt (B) injuries significantly reduced the necessity for fasciotomy (P: p=0.016, B: p=0.02) and caused a significant fall in the incidence of contracture (P: p=0.018, B: p=0.02) and of amputation (P: p=0.009, P: p=0.012). CONCLUSIONS: The policy of early shunting of artery and vein in CLVIs has proved to be of great benefit in terms of significantly improved outcomes, better operative discipline and harmonious collaboration among the specialists involved.

Periods of low atmospheric pressure are associated with high abdominal aortic aneurysm rupture rates in Northern Ireland.

Seasonal and circadian variation in the incidence of ruptured abdominal aortic aneurysm (RAAA) has been reported. We explored the role of atmospheric pressure changes on rupture incidence and its relationship to cardiovascular risk factors. During a three year-period, 1st April 1998 and 31st March 2001, data was prospectively acquired on 144 Ruptured Abdominal Aortic Aneurysm (RAAA) presenting to the Regional Vascular Surgery Unit at the Royal Victoria Hospital, Belfast, Northern Ireland. For each patient the chronology of acute onset of symptoms and presentation to the regional vascular unit was recorded, along with details of standard cardiovascular risk factors. During the same period meteorological data including atmospheric pressure and air temperature were recorded daily at the regional meteorological research unit, Armagh. We then analyzed the monthly mean values for daily rupture incidence in relation to the monthly values for atmospheric pressure, pressure change and temperature. Furthermore atmospheric pressure on the day of rupture, and day preceding rupture, were also analyzed in relation to days without rupture presentation and between individual ruptures for various cardiovascular risk factors. Data demonstrated a significant monthly variation in aneurysm rupture frequency, (p<0.03, ANOVA). There was also a significant monthly variation in mean barometric atmospheric pressure, (p<0.0001, ANOVA), months with high rupture frequency also exhibiting low average pressures in the months of April (0.24 +/- 0.04 ruptures per day and 1007.78 +/- 1.23 mB) and September (0.16 +/- 0.04 ruptures per day and 1007.12 +/- 1.14 mB), respectively. The average barometric pressures were found to be significantly lower on those days when ruptures occurred (n=1127) compared to days when ruptures did not occur (n=969 days), (1009.98 +/- 1.11 versus 1012.09 +/- 0.41, p<0.05). Full data on risk factors was available on 103 of the 144 rupture patients and was further analyzed. Interestingly, RAAA with a known history of hypertension, (n=43), presented on days with significantly lower atmospheric pressure than those without, (n=60), (1008.61 +/- 2.16 versus 1012.14 +/- 1.70, p<0.05). Further analysis of ruptures grouped into those occurring on days above or below mean annual atmospheric pressure 1013.25 (approximately 1 atmosphere), by Chi-square test, revealed three cardiovascular risk factors significantly associated with low-pressure rupture, (p<0.05). Data represents mean +/- SEM, statistical comparisons with Student t-test and ANOVA. These data demonstrate a significant association between periods of low barometric pressure and high incidence of ruptured aneurysm, especially in those patients with known hypertension. The association between rupture incidence and barometric pressure warrants further study as it may influence the timing of elective AAA repair.

Radial artery mycotic pseudoaneurysm in a haemophiliac: a potentially fatal complication of arterial catheterization.

We present a case of radial artery pseudoaneurysm formation in a haemophiliac patient, which developed after radial artery cannulation. Haematologists and anaesthetists should be aware of this potentially fatal condition.

The use of tonometry to predict mortality in patients undergoing abdominal aortic aneurysm repair.

OBJECTIVE: To assess the reliability of intramucosal pH (pHi) of the sigmoid colon, IL-6 concentration and the APACHE II score in predicting outcome in patients undergoing elective abdominal aortic aneurysm repair. DESIGN: Prospective study. METHODS: In 42 patients, measurements were made of the sigmoid pHi with the silicone tonometer and plasma IL-6 by enzyme linked immuno-sorbent assay (ELISA). The daily postoperative APACHE II scores were also calculated. In 29 patients a preoperative left ventricular ejection fraction was determined by gated radionuclide angiography. RESULTS: Four out of 42 patients who were studied died. The lowest perioperative pHi, the peak postoperative IL-6 concentration and APACHE II scores were significantly different in the survivors in comparison to the non-survivors. In the non-survivors, the fall in pHi preceded the time of patient's demise by at least 4 days. Significant correlations were observed between changes in pHi, IL-6 and APACHE II. Using receiver operating characteristic curves, pHi was shown to be the most predictive of mortality compared to the other variables. The simplicity, speed and practicality of using the tonometer adds to its superiority over the latter measurements. No relationship was found between ventricular ejection fraction, pHi and outcome. CONCLUSION: Although the number of patients is small, these results support pHi as a valuable predictor of outcome and also suggest a role for the gut in initiating the IL-6 and physiological responses.

Intramucosal acidosis and systemic host responses in abdominal aortic aneurysm surgery.

OBJECTIVES: To assess the specific host responses to systemic endotoxemia and tumor necrosis factor (TNF) activation after abdominal aortic aneurysm surgery by measuring antiendotoxin core antibodies (EndoCab) immunoglobulin (Ig)G and IgM, and soluble p55TNF receptor concentrations. The role of the gut in initiating these immune responses was evaluated by correlating the systemic markers to changes in the intramucosal pH of the sigmoid colon. DESIGN: Retrospective, reevaluation study. SETTING: Vascular unit of a university hospital. PATIENTS: Eleven patients who underwent abdominal aortic aneurysm repair surgery were selected from a larger patient cohort (n = 42) on the basis of their clinical outcome (four patients had fatal complications and seven patients had an uneventful recovery). INTERVENTIONS: After induction of anesthesia, intramucosal pH of the sigmoid colon was measured using tonometry. Blood samples were obtained from indwelling catheters or direct venipuncture preoperatively, during surgery, and daily until postoperative day 5. MEASUREMENTS AND MAIN RESULTS: Those patients who died developed intramucosal acidosis of the sigmoid colon intraoperatively. Significant consumption of both IgG and IgM EndoCab antibodies was found in all patients. By measuring the concentration of antibodies to a neutral antigen, i.e., tetanus toxoid, the consumption of IgG EndoCab antibody concentrations was shown to be a specific host response. In all patients, reciprocal changes in the serum concentrations of p55TNF receptor and interleukin (IL)-6 were observed. The percentage increase in p55TNF receptor and the concentration of IL-6 were significantly higher in the nonsurvivor group by 48 hrs. There were significant correlations between, intramucosal pH and EndoCab antibodies, intramucosal pH and p55 TNF receptor, and p55 TNF receptor and IL-6. CONCLUSIONS: The development of colonic ischemia is associated with a significant consumption of IgG EndoCab antibodies and a simultaneous increase in soluble p55TNF receptor. This study provides further support for the concept that gut-derived endotoxin and the generation of TNF may play a role in the pathogenesis of complications after abdominal aortic aneurysm surgery.

The generation of byproducts of lipid peroxidation following carotid endarterectomy.

The aim of this study was to determine whether free radical-induced lipid peroxidation occurs following transient carotid clamping. Jugular vein plasma levels of malondialdehyde (MDA) and diene conjugates (DC) were estimated in 24 patients undergoing carotid endarterectomy, at the beginning of the operation (To), just prior to clamping the carotid artery before the shunt was removed for closure of the arteriotomy (Ts), and at 30 (T30), 60 (T60), 120 (T120), 180 (T180) and 300 (T300) seconds after the clamps were released. Carotid clamp times were recorded. Significant elevations in the concentrations of both MDA and DC were observed at T60 after clamp release (MDA = 559 +/- 64 pmol/ml, DC = 428 +/- 32 units/ml), in comparison to concentrations at To (MDA = 408 +/- 34 pmol/ml, p < 0.01; DC = 374 +/- 28 units/ml, p < 0.05), returning to baseline at T300. There was a significant correlation between the percentage rise in MDA concentration and the duration of clamp-induced ischaemia (r = 0.45, p = 0.03). The significance of this burst of MDA and DC is unclear especially as the one patient who sustained a postoperative neurological deficit displayed no rise in the concentration of either. If this rise is related to free radical generation following ischaemia-reperfusion injury it may play an important role in influencing the clinical outcome in the patients.

Fractures of the distal interphalangeal joint.

Fractures at the distal interphalangeal joint present a therapeutic challenge to the hand surgeon because of the relatively small bones and joint surfaces involved and the limited internal fixation devices available. Knowing which patients and which fractures are best treated surgically is key to a successful result. The normal anatomy and biomechanics of the joint are outlined and overviewed and the anatomy, etiology, therapy, and classification are discussed. Comminuted fractures of the articular surface of the distal phalanx are presented as are epiphyseal fractures of the distal phalanx. Avulsion of the profundus tendon (jersey finger) is discussed, emphasizing Leddy and Packer's Types I, II, and III injuries and the recommended treatment. Condylar fractures of the articular surface of the middle phalanx at the distal interphalangeal joint are the subject of the next section, with London's classification scheme and recommended treatment. Finally, complex open injuries and replantation through the distal interphalangeal joint are presented with guidelines for salvage and treatment.

Cross leg flap in a bilateral traumatic amputee.

A case report of a bilateral traumatic amputee who underwent a cross leg flap to preserve a knee disarticulation level amputation is presented. Salvage of amputated parts in the lower extremities to preserve stamp length provided our patient with better stability and decreased energy expenditure with ambulation.

Effect of low-dose dopamine on sigmoid colonic intramucosal pH in patients undergoing elective abdominal aortic aneurysm repair.

The effect of low-dose dopamine administration on intramucosal pH (pHi) of the sigmoid colon and on postoperative function of various organs in patients undergoing elective abdominal aortic aneurysm repair was examined. Nineteen patients were randomized to two groups; nine received dopamine at a rate of 3 micrograms per kg per min for 24 h from induction of anaesthesia and ten control patients received fluids without dopamine. pHi was measured with a silicone tonometer and daily samples of blood were taken for measurement of liver transaminase activity, arterial oxygen saturation and creatinine concentration. Mean(s.e.m.) pHi fell to a significantly lower minimum value in those receiving dopamine compared with control patients (6.86(0.10) versus 7.11(0.08), P < 0.05). Five of the nine patients given dopamine developed intramucosal acidosis compared with only one of the ten control patients (P = 0.06). After operation the mean(s.e.m.) aspartate transaminase concentration in patients given dopamine rose from 33(2) to 80(17) units/l (P < 0.01); in control patients it rose from 32(3) to 59(16) units/l (P = 0.054). No differences between the groups was observed in the postoperative ratio of arterial oxygen saturation to inspired oxygen fraction or creatinine concentrations. These results indicate that dopamine has no beneficial effect on bowel mucosal oxygenation and function of the various organs in patients undergoing aortic aneurysm repair.

Reduction of free radical generation minimises lower limb swelling following femoropopliteal bypass surgery.

Oxygen-derived free radicals have been implicated as contributors to the development of lower limb oedema observed after femoropopliteal bypass grafting. This study investigates the occurrence of free radical-induced lipid peroxidation after this operation and the possible effects of allopurinol (xanthine oxidase inhibitor) in reducing free radical injury in order to minimise lower leg oedema. Twenty-nine patients undergoing femoropopliteal bypass surgery were randomised in a double blind fashion into two groups; those in one were given allopurinol 200 mg orally (n = 15) at 24 h and 2 h preoperatively and again at 24 h postoperatively, while those in the second group received a placebo (n = 14). Daily lower limb volume was calculated to assess swelling. Blood samples were taken from the femoral vein for measurements of malondialdehyde (MDA), an end product of lipid peroxidation, before the application of the femoral artery clamp, just prior to and immediately after clamp release, and at 20 minute intervals thereafter for 1 hour. The increase in lower limb volume in the placebo group was almost twice (8.9 +/- 1.6%) that of the allopurinol group (4.6 +/- 1%; p = 0.02). Six out of the 14 patients receiving placebo suffered swelling of 10% or more of original lower limb volume in comparison to only one out of 15 in those given allopurinol (p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Bowel ischaemia and organ impairment in elective abdominal aortic aneurysm repair.

In 30 patients undergoing elective repair of abdominal aortic aneurysm the intramucosal pH (pHi) of the sigmoid colon was measured. Blood for endotoxin assay was taken at intervals before, during and after surgery. Daily measurements were made of liver transaminase activity and of arterial partial pressure of oxygen (PaO2). The mean (s.e.m.) peak systemic endotoxin concentration in those who developed intramucosal acidosis (pHi below 7.00) was 90(14) pg/ml, compared with 42(5) pg/ml in those who did not (P < 0.01). In the 14 patients whose pHi fell below 7.00, the mean (s.e.m.) postoperative rise in aspartate transaminase activity was 346(74) per cent, compared with 181(20) per cent in those whose pHi remained above this level (P < 0.05). The mean (s.e.m.) postoperative ratio of PaO2 to the fraction of inspired oxygen was 177(11) mmHg in those with intramucosal acidosis, compared with 260(24) mmHg in those whose pHi remained above 7.00 (P < 0.01). These results demonstrate a relationship between bowel ischaemia, endotoxaemia and organ impairment following elective aneurysm repair.

Bipolar coagulation at different energy levels: effect on patency.

Determining the extent of damage caused by bipolar coagulation at different levels is critical in microsurgery. If no significant damage occurs at known levels, this technique can be used instead of ligation, saving considerable time. One hundred eighty Sprague-Dawley rats were divided into six groups of 30 each. The effects of bipolar coagulation were assessed at either 2 or 10.4 watts at the junction between the common femoral artery and a branch vessel. Three common clinical settings were used: branch coagulation without interruption of blood flow in the common femoral artery; branch coagulation with interruption of blood flow for 30 minutes; and branch coagulation with arterial anastomosis 3-5 mm distal to the branch. Control procedures without coagulation were performed on the contralateral vessels. The animals were re-explored at 5-7 days. No differences occurred in patency of the coagulated vessels at 2 or 10.4 watts of delivered energy as compared with controls. Recanalization of the side branch occurred in approximately 80% (144/180) of specimens. Extensive damage to endothelium, tunica intima, and tunica media occurred for 1-2 mm around the site of the coagulated branch. The forceps pick-up test demonstrated little difference in flow of the cauterized vessel compared with controls. However, the cauterized vessel had a clinically weaker pulse stream of the transected common femoral artery. Recanalization of the coagulated side branch commonly occurred with a fibrin cap at the end of the vessel. Manipulation of the branch vessel frequently caused rebleeding. Our study shows that bipolar coagulation can be used effectively if coagulation is located at least 2 mm from the main vessel.

Endotoxaemia, the generation of the cytokines and their relationship to intramucosal acidosis of the sigmoid colon in elective abdominal aortic aneurysm repair.

Ischaemia of the large bowel occasionally occurs following abdominal aortic aneurysm repair and may lead to multiple system organ failure (MSOF). Intramucosal acidosis of the sigmoid colon is a good indicator of sigmoid colonic ischaemia. Intramucosal pH of the sigmoid colon was measured using the silicone tonometer in 21 patients undergoing abdominal aortic aneurysmectomy. Samples were taken for plasma endotoxin, tumour necrosis factor (TNF) and interleukin-6 (IL-6) measurements preoperatively, half-hourly during the operation, 2-hourly for the next 12 h, 4-hourly for a further 48 h and 8-hourly thereafter until the fifth day. The intramucosal pH of the sigmoid colon fell to less than 7.00 peri-operatively in 10 patients, four of whom developed diarrhoea; in comparison, this did not occur in any of the 11 whose pH remained greater than 7.00 (p = 0.036). Higher peak concentrations of endotoxin, TNF and IL-6 were found in those patients whose intramucosal pH fell to less than 7.00 compared to those whose pH remained greater than 7.00 (mean +/- S.E.M. pg/ml, endotoxin = 112 +/- 24 vs. 58 +/- 6, p < 0.05; TNF = 26 +/- 8 vs. 7 +/- 2, p < 0.05; IL-6 = 213 +/- 59 vs. 87 +/- 12, p = 0.09). In the two patients who died, both from the group with pH level less than 7.00, concentrations of IL-6 were considerably higher than that in most of the other patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Lipid peroxidation as a cause of lower limb swelling following femoro-popliteal bypass grafting.

We examined the role of free radical induced lipid peroxidation in lower limb swelling in patients following femoro-popliteal bypass grafting. In 20 patients undergoing this operation blood samples were taken from the femoral vein via a cannula before the femoral artery clamp was applied, just prior to and immediately after clamp release and at 10 min intervals thereafter for 1 h for measurements of malondialdehyde (MDA) and vitamin E. The concentration of MDA was significantly elevated at 40 min after reperfusion (mean +/- S.E.M., 573 +/- 83 pmol/ml) compared to just before clamp release (359 +/- 41 pmol/ml; p < 0.01). This was associated with a corresponding fall in the concentration of vitamin E at the time of peak MDA rise (5.68 +/- 0.28 to 5.29 +/- 0.28 mumol/mM cholesterol, p < 0.05) suggesting its utilisation as an antioxidant. The degree of oedema was related to the changes in MDA and vitamin E. Thus, in the 15 patients with greater than 10% increase in lower limb volume the rise in the concentration of MDA was 364 +/- 44 to 693 +/- 76 pmol/ml (p = 0.0001) while that in the five, whose swelling was less than 10%, was 344 +/- 40 to 559 +/- 243 pmol/ml (p = 0.25). A significant fall in vitamin E was found only in the group with greater than 10% lower limb oedema (5.90 +/- 0.33 to 5.40 +/- 0.34 mumol/mM cholesterol, p < 0.01), in comparison to those with less than 10% swelling (5.01 +/- 0.35 to 5.04 +/- 0.50 mumol/mM cholesterol).(ABSTRACT TRUNCATED AT 250 WORDS)

Delayed presentation of bilateral popliteal artery injury.

We describe a patient who developed serious vascular complications following gunshot wounds to both popliteal fossae. There was minimal evidence of vascular injury on presentation to hospital, in particular ankle systolic pressures were normal. Five days following the initial injuries he was found to have a false aneurysm of the popliteal artery in his right leg and an arteriovenous fistula affecting the popliteal vessels of his left leg. The roles of arteriography and Doppler pressure studies in assessment of possible peripheral vascular injury following penetrating trauma are discussed. It is emphasised that a high index of suspicion and careful clinical review is essential if vascular injuries and their complications are not to be missed.

Risk of rupture of postangiographic femoral false aneurysm.

The surgical management of 50 false aneurysms caused by transfemoral arterial catheterization was reviewed to document the incidence and effects of rupture before repair. Twelve false aneurysms ruptured, leading to shock in six patients, distal ischaemia in three and stroke in one. The mean(s.d.) time from catheterization to rupture was 2.8(1.7) (range 1-6) days. Postoperative complications occurred in seven patients with ruptured and eight with non-ruptured aneurysms (P < 0.04). The mean(s.d.) age of patients with ruptured aneurysms was 67.2(6.3) (95 per cent confidence interval 63.5-70.8) years and those without 58.5(9.1) (95 per cent confidence interval 55.3-61.7) years (P < 0.008). On multiple regression analysis, age, peripheral vascular disease and raised plasma liver enzyme levels on admission were found to be significant independent predictive variables for rupture (all P < 0.05). It is recommended that patients with these risk factors undergo urgent operative correction of femoral false aneurysm.