Does sexual conflict increase juvenile survival by reducing cannibalism?

To test the hypothesis that male harassment of females reduces adult female time spent on the water foraging (water use), and thus cannibalism by adult females on juveniles, we manipulated heterospecific prey availability, and social context in adult water striders and measured their effects on: 1) cannibalism of juveniles, 2) activity of adults and 3) habitat use of adults and juveniles. Cannibalism rarely occurred with alternative prey present, but was common without alternative prey. Without alternative prey, females cannibalized much more than males, but contrary to predictions, male presence did not reduce cannibalism rates. Male presence decreased female water use; however, this was counteracted by the fact that the lack of alternative prey increased female water use and activity while on the water. Furthermore, in groups of 4 males with 4 females, lack of alternative prey reduced male activity while on the water. Thus the predicted negative effect of sexual conflict on cannibalism was reduced by female and male responses to low food availability. Juveniles increased time off the water when more females or males were more on the water and active. Overall, cannibalism rates depended on alternative prey, male-female social dynamics, female foraging and juvenile refuge use.

Intraoperative neuroprotective interventions prevent spinal cord ischemia and injury in thoracic endovascular aortic repair.

OBJECTIVE: Transient and permanent paraparesis and paraplegia (spinal cord injury [SCI]) are reported in up to 13% of patients undergoing thoracic endovascular aortic repair (TEVAR) for descending thoracic aortic aneurysm, thoracoabdominal aortic aneurysm, and thoracic aortic dissection. We hypothesize that aggressive intraoperative and postoperative neuroprotective interventions prevent or significantly reduce all SCI in TEVAR. METHODS: Using a prospectively maintained, Institutional Review Board-approved database, we retrospectively reviewed all TEVARs performed in a university tertiary referral center from 2005 to 2014 to study the incidence of all transient and permanent lower extremity SCI. Only TEVARs for traumatic aortic tear were excluded. Arch debranching and carotid subclavian bypass were performed before TEVAR in patients with arch involvement. All patients had moderate systemic hypothermia (34°C), mean arterial pressure ≥90 mm Hg, and hemoglobin ≥10 g/dL. Patients received mannitol (12.5 g), methylprednisolone (30 mg/kg), and naloxone (1 µg/kg/h). Patients in whom >12 cm of aortic coverage was planned had spinal fluid drained to a pressure of <8 mm Hg intraoperatively and postoperatively until normal leg strength was confirmed. The main outcome measure was transient or permanent SCI. RESULTS: One hundred fifty-five patients had TEVAR between 2005 and 2014. Mean age was 74 years, and 56.1% were male. Descending thoracic aortic aneurysm was present in 91.6%, thoracoabdominal aortic aneurysm in 8.4%, and dissection in 28.8%. Presentation was acute in 42.5%. The procedure included carotid-subclavian bypass in 18.7% of patients. Seventy-two percent of patients had spinal fluid drainage. Mean aortic coverage was 25 cm. Eighty-one percent of patients had >12 cm aortic coverage, and 49% had complete coverage of the thoracic aorta (coverage from subclavian to celiac artery). In-hospital mortality was 1.94%. Stroke occurred in 1.32% of patients. No patient had renal failure. SCI occurred in 0.65% (1 of 154) of patients. CONCLUSIONS: SCI in TEVAR can be significantly reduced by using proactive intraoperative and postoperative neuroprotective interventions that prolong spinal cord ischemic tolerance and increase spinal cord perfusion and oxygen delivery.

The effect of intercostal artery reimplantation on spinal cord injury in thoracoabdominal aortic aneurysm surgery.

OBJECTIVE: Intercostal artery (ICA) reimplantation (ICAR) is thought to decrease spinal cord injury (SCI) in thoracic aortic aneurysm and thoracoabdominal aortic aneurysm (TAAA) surgery. Patients treated from 1989 to 2005 without ICAR were compared with those treated from 2005 to 2013 with ICAR to determine whether ICAR reduced SCI. We hypothesized that ICAR would reduce SCI, especially in the highest-risk patients. METHODS: This was a retrospective analysis using a prospectively maintained Investigational Review Board-approved database from a university tertiary referral center. The analysis included all patients (n = 805) undergoing thoracic aortic aneurysm and TAAA surgery from 1989 to 2013. The main outcome measure was any transient or permanent paraplegia or paraparesis (SCI). From 1989 to 2004, ICAR was not performed in patients, and open ICAs were ligated; from 2005 to 2013, open ICAs at T7 to L2 were reimplanted in patients with Crawford type I, II, and III TAAAs. Surgical technique was cross clamp without assisted circulation. Anesthetic management was the same from 1989 to 2013. Demographic, intraoperative, and outcome variables were assessed by univariate and multivariate analysis. Observed/expected ratios for paralysis were calculated. RESULTS: A total of 540 patients had surgery before 2005, and 265 had surgery after 2005, when ICAR was begun. There were 275 type I, II, and III TAAAs before 2005 and 164 after 2005. Aneurysm extent, acuity, SCI, mortality, renal failure, and pulmonary failure were the same in patients treated before and after 2005. Multivariate modeling of all patients showed type II TAAA (P = .0001), dissection (P = .00015), and age as a continuous variable (P = .0085) were significant for SCI. Comparing only type I, II, and III TAAAs, there was no difference in SCI between those with ICAR after 2005 and those without ICAR before 2005 (5.1% vs 8.8%; P = .152). In a subanalysis of the highest-risk patients (type II, dissection, acute), ICAR was not significant (P = .27). Observed/expected ratios ratios were 0.23 before 2005 and 0.16 after 2005 (χ2 = .796; P = .37). CONCLUSIONS: Although there was a small decrease in SCI with ICAR, reattaching ICAs did not produce a statistically significant reduction in SCI, even in the highest-risk patients.

Postoperative renal failure in thoracoabdominal aortic aneurysm repair with simple cross-clamp technique and 4°C renal perfusion.

OBJECTIVE: Acute renal failure (ARF) is reported in up to 12% of patients after thoracoabdominal aortic aneurysm (TAAA) repair with assisted circulation. ARF increases mortality, reduces quality of life, and increases length of hospital stay. This study analyzes ARF after TAAA repair done without assisted circulation. METHODS: A retrospective analysis of all patients treated for TAAA from 2000 to 2013 was performed using a concurrently maintained, institutionally approved database. All surgeries used simple cross-clamp technique, with moderate systemic hypothermia (32°-33°C) and renal artery perfusion with 4°C solution. Serum creatinine concentration was measured preoperatively and 1 day, 3 days, 7 days, and 30 days after surgery, and Cockcroft-Gault estimated glomerular filtration rate (eGFR) was calculated. Kidney injury was classified by RIFLE (Risk, Injury, Failure, Loss of kidney function, End-stage renal disease) eGFR criteria. Changes in eGFR, kidney injury, ARF, dialysis, length of stay, mortality, and risk factors for ARF were analyzed with SAS-JMP software (SAS Institute, Cary, NC) for univariate analysis and multivariate modeling. RESULTS: From 2000 to 2013, 455 patients had TAAA surgery; 116 (25.5%) were acute. Mean preoperative eGFR was 62.3 mL/min. Mean renal ischemia time was 58.9 minutes. Eighteen patients (4%) had ARF; nine (2%) required temporary dialysis, and three (0.66%) required permanent dialysis. In univariate analysis, age, renal ischemia time, acuity, baseline eGFR, previous aortic surgery, surgical blood loss, and return to operating room for bleeding complications were significant for ARF (P < .05). Sex, aneurysm extent by Crawford type, cardiac index and mean arterial pressure after reperfusion, and use of loop diuretics were not significant for ARF. In a stepwise deletion model, acute (P = .0377), previous aortic surgery (P = .0167), return to operating room (P = .0213), and age (P = .0478) were significant for ARF. Surgical blood loss (P = .0056) and return to operating room (P = .0024) were significant for postoperative dialysis in multivariate analysis. Only surgical blood loss was significant for permanent dialysis in a multivariate model (P = .0331). CONCLUSIONS: Very low ARF after TAAA repair can be achieved by simple cross-clamp technique with moderate systemic hypothermia and profound renal cooling. Age, preoperative eGFR, previous aortic surgery, return to operating room, and surgical blood loss were significant for ARF. Return to operating room for bleeding and surgical blood loss were significant for dialysis. Baseline eGFR <30 mL/min and postoperative dialysis were significant for mortality. Most patients with ARF, even those with temporary dialysis after TAAA repair, recover renal function to near preoperative levels.

Complications of spinal fluid drainage in thoracic and thoracoabdominal aortic aneurysm surgery in 724 patients treated from 1987 to 2013.

OBJECTIVE: To study complications from spinal fluid drainage in open thoracic/thoracoabdominal and thoracic endovascular aortic aneurysm repairs to define risks of spinal fluid drainage. DESIGN: Retrospective, prospectively maintained, institutionally approved database. SETTING: Single institution university center. PARTICIPANTS: 724 patients treated from 1987 to 2013 INTERVENTIONS: The authors drained spinal fluid to a pressure≤6 mmHg during thoracic aortic occlusion/reperfusion in open and ≤8 mmHg after stent deployment in endovascular procedures. Low pressure was maintained until leg strength was documented. If bloody fluid appeared, drainage was stopped. Head computed tomography (CT) and, if indicated, spine CT and magnetic resonance imaging (MRI) were performed for bloody spinal fluid or neurologic deficit. MEASUREMENTS AND MAIN RESULTS: Spinal fluid drainage was studied for bloody fluid, CT/MRI-identified intracranial and spinal bleeding, neurologic deficit, and death. Seventy-three patients (10.1%) had bloody fluid; 38 (5.2%) had intracranial blood on CT. One patient had spinal epidural hematoma. Higher volume of fluid drained and higher central venous pressure during proximal clamping were associated with intracranial blood. Most patients with intracranial blood were asymptomatic. Six patients had neurologic deficits: of the 6, 3 died (0.4%), 1 (0.1%) had permanent hemiparesis, and 2 recovered. Three of the six deficits were delayed, associated with heparin anticoagulation. CONCLUSIONS: 10% of patients had bloody spinal fluid; half of these had intracranial bleeding, which was almost always asymptomatic. In these patients, immediately stopping drainage and correcting coagulopathy may decrease the risk of serious complications. Neurologic deficit from spinal fluid drainage is uncommon (0.8%), but has high morbidity and mortality.