A mathematical model for pressure-based organs behaving as biological pressure vessels.

We introduce a mathematical model that describes the allometry of physical characteristics of hollow organs behaving as pressure vessels based on the physics of ideal pressure vessels. The model was validated by studying parameters such as body and organ mass, systolic and diastolic pressures, internal and external dimensions, pressurization energy and organ energy output measurements of pressure-based organs in a wide range of mammals and birds. Seven rules were derived that govern amongst others, lack of size efficiency on scaling to larger organ sizes, matching organ size in the same species, equal relative efficiency in pressurization energy across species and direct size matching between organ mass and mass of contents. The lung, heart and bladder follow these predicted theoretical relationships with a similar relative efficiency across various mammalian and avian species; an exception is cardiac output in mammals with a mass exceeding 10 kg. This may limit massive body size in mammals, breaking Cope's rule that populations evolve to increase in body size over time. Such a limit was not found in large flightless birds exceeding 100 kg, leading to speculation about unlimited dinosaur size should dinosaurs carry avian-like cardiac characteristics.

Prophylactic use of proton pump inhibitors post-cardiac surgery.

AIMS/BACKGROUND: Gastrointestinal bleeding significantly increases morbidity and mortality rates postoperatively in patients undergoing cardiac surgery. The prophylactic prescribing of proton pump inhibitors post-cardiac surgery is currently a class IIa recommendation of the European Association of Cardio-Thoracic Surgery. METHOD: A retrospective review of patients who underwent cardiac surgery between July and December 2019 in the authors' hospital was carried out, using discharge summaries. New treatment charts were introduced with a pre-printed proton pump inhibitor included in the 'regular medication' section of the treatment chart and two reaudits were performed using the same methodology. RESULTS: Before the intervention, 47% were prescribed omeprazole postoperatively, compared to 74% (P<0.001) and 66% (P=0.008) in the first and second reaudits respectively. Gastrointestinal bleeding was more common pre-intervention (4% vs 1% respectively; P=0.10). CONCLUSIONS: This intervention resulted in a statistically significant improvement in the prescription of postoperative omeprazole and a decrease in gastrointestinal bleeds. However, other risk factors such as diabetes mellitus, arteriosclerosis and procedure urgency may have contributed to the absence of statistical significance in the latter.

Video-Assisted Thoracoscopic Versus Robotic-Assisted Thoracoscopic Thymectomy: Systematic Review and Meta-analysis.

OBJECTIVE: Minimally invasive thoracic surgical procedures, performed with or without the assistance of a robot, have gained popularity over the last decade. They have increasingly become the choice of intervention for a number of thoracic surgical operations. Minimally invasive surgery decreases postoperative pain, hospital stay and leads to a faster recovery in comparison with conventional open methods. Minimally invasive techniques to perform a thymectomy include video-assisted thoracoscopic surgery (VATS) or robotic-assisted thoracoscopic surgery (RATS). In this study, we aim to systematically review and interrogate the literature on minimally invasive thymectomy and draw a meta-analysis on the outcomes between the two approaches. METHODS: An extensive electronic health database search was performed on all articles published from inception to May 2015 for studies describing outcomes in VATS and RATS thymectomy. RESULTS: A total of 350 patients were included in this study, for which 182 and 168 patients underwent RATS and VATS thymectomy, respectively. There were no recorded in-hospital deaths for either procedure. There was no statistical difference in conversion to open, length of hospital stay, or postoperative pneumonia. Operational times for RATS thymectomy were longer. CONCLUSIONS: The VATS and RATS thymectomy offer good and safe operative and perioperative outcomes. There is little difference between the two groups. However, there is poor evidence basis for the long-term outcomes in minimally invasive procedures for thymectomy. It is imperative that future studies evaluate oncological outcomes both short and long term as well as those related to safety.

A large pulmonary arteriovenous malformation causing cerebrovascular accidents.

The incidence of pulmonary arteriovenous malformations (PAVMs) is 2.5 in 100,000. 80% are associated with Osler-Weber-Rendu syndrome or hereditary haemorrhagic telangiectasia. We report the case of a 70-year-old man with a 6 cm spherical mass incidentally found on chest X-ray. There was a localised systolic bruit over the right lower zone posteriorly; however, he was asymptomatic. He had suffered a stroke, affecting his right hand and his speech, from which he recovered. He experienced regular transient ischaemic attacks, on an average of every 2 months. He underwent a right lower lobectomy and on ligating the right lower lobe pulmonary artery the saturations of oxygen rose from 92% to 97%, demonstrating a significant right to left extracardiac shunt. Postoperative recovery was excellent and 1 year later the patient reports no further neurological symptoms. 40% of such lesions exhibit symptoms, however, only one-third are neurological. Treatment should be by percutaneous embolisation.

Squamous cell carcinoma of unknown origin metastasising to the right atrium causing acute heart failure.

We describe a case of metastasis to the heart, which was initially suspected to be a myxoma, causing acute right heart failure. Emergency surgery was carried out by opening the right atrium and superior vena cava, and debulking the tumour in a piecemeal fashion, providing temporary relief of symptoms. The histology showed this to be metastatic squamous cell carcinoma possibly of head and neck origin. This is extremely rare, with few published cases. Full endoscopic and CT, including positron emission tomography CT, investigation of the head and neck was performed with no primary findings. Only two such cases of squamous cell carcinoma of unknown origin metastasising to the heart have been described, and, in both cases, the patients died within several weeks of diagnosis. This patient remains alive 2 months postoperatively and is receiving radiotherapy to the chest, but his prognosis remains poor.