Evaluation of prognostic risk models for postoperative pulmonary complications in adult patients undergoing major abdominal surgery: a systematic review and international external validation cohort study

BACKGROUND

Stratifying risk of postoperative pulmonary complications after major abdominal surgery allows clinicians to modify risk through targeted interventions and enhanced monitoring. In this study, we aimed to identify and validate prognostic models against a new consensus definition of postoperative pulmonary complications.

METHODS

We did a systematic review and international external validation cohort study. The systematic review was done in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. We searched MEDLINE and Embase on March 1, 2020, for articles published in English that reported on risk prediction models for postoperative pulmonary complications following abdominal surgery. External validation of existing models was done within a prospective international cohort study of adult patients (≥18 years) undergoing major abdominal surgery. Data were collected between Jan 1, 2019, and April 30, 2019, in the UK, Ireland, and Australia. Discriminative ability and prognostic accuracy summary statistics were compared between models for the 30-day postoperative pulmonary complication rate as defined by the Standardised Endpoints in Perioperative Medicine Core Outcome Measures in Perioperative and Anaesthetic Care (StEP-COMPAC). Model performance was compared using the area under the receiver operating characteristic curve (AUROCC).

FINDINGS

In total, we identified 2903 records from our literature search; of which, 2514 (86·6%) unique records were screened, 121 (4·8%) of 2514 full texts were assessed for eligibility, and 29 unique prognostic models were identified. Nine (31·0%) of 29 models had score development reported only, 19 (65·5%) had undergone internal validation, and only four (13·8%) had been externally validated. Data to validate six eligible models were collected in the international external validation cohort study. Data from 11 591 patients were available, with an overall postoperative pulmonary complication rate of 7·8% (n=903). None of the six models showed good discrimination (defined as AUROCC ≥0·70) for identifying postoperative pulmonary complications, with the Assess Respiratory Risk in Surgical Patients in Catalonia score showing the best discrimination (AUROCC 0·700 [95% CI 0·683-0·717]).

INTERPRETATION

In the pre-COVID-19 pandemic data, variability in the risk of pulmonary complications (StEP-COMPAC definition) following major abdominal surgery was poorly described by existing prognostication tools. To improve surgical safety during the COVID-19 pandemic recovery and beyond, novel risk stratification tools are required.

FUNDING

British Journal of Surgery Society.

Expression of adiponectin and its receptors in avian species

Adipose tissue is a dynamic endocrine organ secreting a variety of hormones that affect physiological functions within the central nervous system, cardiovascular system, reproductive, and immune systems. The endocrine role of avian adipose tissue remains enigmatic as many of the classical hormones found in mammalian adipose tissue have not been found in avians. This mini-review summarizes our current knowledge on avian adiponectin, one of the most abundant adipose tissue hormones, and its receptors. We cloned the genes encoding chicken adiponectin and its receptors, AdipoR1 and AdipoR2. Using anti-chicken adiponectin antibody, we found that chicken adipose tissue and plasma predominantly contain a unique polymer of adiponectin with a mass greater than 669kDa, unlike mammalian adiponectin which is found as three distinct oligomers. Mass spectrometric analyses of chicken adiponectin revealed certain post-translational modifications that are likely to favor the unique multimerization of adiponectin in chickens. Unlike adiponectin, the nucleotide sequences of chicken AdipoR1- and AdipoR2 cDNA are highly similar to that of mammalian adiponectin receptors. Both adiponectin and adiponectin receptors are widely expressed in several tissues in the chicken. Herein, we review the unique biochemistry of adiponectin as well as expression of adiponectin and its receptors in the chicken. Future studies should focus on elucidating the role of adiponectin, AdipoR1, and AdipoR2 on metabolism, steroidogenesis, and adipose tissue remodeling during growth and reproduction in birds.

Methionine restriction affects oxidative stress and glutathione-related redox pathways in the rat

Lifelong dietary methionine restriction (MR) is associated with increased longevity and decreased incidence of age-related disorders and diseases in rats and mice. A reduction in the levels of oxidative stress may be a contributing mechanistic factor for the beneficial effects of MR. To examine this, we determined the effects of an 80% dietary restriction of Met on different biomarkers of oxidative stress and antioxidant pathways in blood, liver, kidney and brain in the rat. Male F-344 rats were fed control (0.86% methionine) or MR (0.17% methionine) diets for up to six months. Blood and tissues were analyzed for glutathione (GSH) concentrations, related enzyme activities and biomarkers of oxidative stress. MR was associated with reductions in oxidative stress biomarkers including plasma 8-hydoxydeoxyguanosine (8-OHdG) and 8-isoprostane and erythrocyte protein-bound glutathione after one month with levels remaining low for at least six months (P < 0.05). Levels of free GSH in blood were increased after 1-6 months of MR feeding whereas liver GSH levels were reduced over this time (P < 0.05). In MR rats, GSH peroxidase activity was decreased in liver and increased in kidney compared with controls. No changes in the activities of GSH reductase in liver and kidney and superoxide dismutase in liver were observed as a result of MR feeding. Altogether, these findings indicate that oxidative stress is reduced by MR feeding in rats, but this effect cannot be explained by changes in the activity of antioxidant enzymes.

Gonadotrophin-inhibitory hormone receptor expression in the chicken pituitary gland: potential influence of sexual maturation and ovarian steroids

Gonadotrophin-inhibitory hormone (GnIH), a hypothalamic RFamide, has been found to inhibit gonadotrophin secretion from the anterior pituitary gland originally in birds and, subsequently, in mammalian species. The gene encoding a transmembrane receptor for GnIH (GnIHR) was recently identified in the brain, pituitary gland and gonads of song bird, chicken and Japanese quail. The objectives of the present study are to characterise the expression of GnIHR mRNA and protein in the chicken pituitary gland, and to determine whether sexual maturation and gonadal steroids influence pituitary GnIHR mRNA abundance. GnIHR mRNA quantity was found to be significantly higher in diencephalon compared to either anterior pituitary gland or ovaries. GnIHR mRNA quantity was significantly higher in the pituitaries of sexually immature chickens relative to sexually mature chickens. Oestradiol or a combination of oestradiol and progesterone treatment caused a significant decrease in pituitary GnIHR mRNA quantity relative to vehicle controls. GnIHR-immunoreactive (ir) cells were identified in the chicken pituitary gland cephalic and caudal lobes. Furthermore, GnIHR-ir cells were found to be colocalised with luteinising hormone (LH)beta mRNA-, or follicle-stimulating hormone (FSH)beta mRNA-containing cells. GnIH treatment significantly decreased LH release from anterior pituitary gland slices collected from sexually immature, but not from sexually mature chickens. Taken together, GnIHR gene expression is possibly down regulated in response to a surge in circulating oestradiol and progesterone levels as the chicken undergoes sexual maturation to allow gonadotrophin secretion. Furthermore, GnIHR protein expressed in FSHbeta or LHbeta mRNA-containing cells is likely to mediate the inhibitory effect of GnIH on LH and FSH secretion.

Pituitary progesterone receptor expression and plasma gonadotrophin concentrations in the reproductively dysfunctional mutant restricted ovulator chicken

Female mutant restricted ovulator (RO) chickens of the White Leghorn strain carry a naturally occurring single nucleotide mutation in the very low density lipoprotein receptor (VLDLR) gene. Due to this mutation, RO hens fail to express a functional VLDLR protein on the oocyte membrane, which results in an impaired uptake of circulating yolk precursor macromolecules. Mutant RO hens subsequently develop hyperlipidemia and generally fail to lay eggs due to follicular atresia. Since RO hens also reportedly have three-fold higher basal plasma estrogen concentrations, combined with four-fold lower levels of circulating progesterone as compared to wild-type (WT) hens, we hypothesized that RO hens would have an increased abundance of pituitary progesterone receptor (PR) mRNA and PR isoforms A and B as well as alterations in circulating gonadotrophin levels. Quantitative PCR assays revealed significantly greater (P<or=0.05) pituitary PR mRNA abundance in RO hens as compared to WT hens. Similarly, pituitary PR isoforms A and B quantities were significantly greater (P<or=0.05) in the RO hens compared to WT hens. In addition, mutant RO hens had significantly greater plasma concentrations of luteinizing hormone, follicle stimulating hormone, estrone, and estradiol, but lower circulating progesterone levels. Collectively, elevated circulating estrogen and/or decreased progesterone levels may have contributed to the upregulation of PR mRNA and PR isoforms A and B in the RO hen pituitary gland. Lastly, in order to gain a more complete understanding of why RO hens are reproductively dysfunctional, a model is proposed that links humoral and ovarian factors to observed and putative changes in the hypothalamic-pituitary axis.

Adiponectin gene is expressed in multiple tissues in the chicken: food deprivation influences adiponectin messenger ribonucleic acid expression

Adiponectin is a cytokine hormone originally found to be secreted exclusively by white adipose tissue. However, recent evidences suggest that adiponectin is also produced in brown adipose tissue and skeletal muscle. The present study investigated the expression of adiponectin mRNA in various tissues in the chicken. We also studied the effect of food deprivation on adiponectin gene expression in adipose tissue, liver, anterior pituitary gland, and diencephalon in the chicken. The open reading frame of chicken adiponectin cDNA consists of 735 nucleotides that were 65-68% homologous to various mammalian adiponectin cDNAs. The deduced amino acid sequence of chicken adiponectin contains 22 glycine-X-Y repeats (in which X and Y represent any amino acid) at the N-terminal end as found in the mammalian adiponectin. By RT-PCR and Northern analysis, we detected chicken adiponectin mRNA transcript in adipose tissue, liver, anterior pituitary gland, diencephalon, skeletal muscle, liver, kidney, ovary, and spleen but not in blood. Adiponectin mRNA expression in various tissues was quantitated using real-time quantitative PCR and found to be the highest in adipose tissue, followed by liver, anterior pituitary, diencephalon, kidney, and skeletal muscle. We also found that adiponectin mRNA quantity was significantly decreased after a 48-h food deprivation in adipose tissue, liver, and anterior pituitary gland but not in diencephalon. Our results provide novel evidence that, unlike mammals, adiponectin gene is expressed in several tissues in the chicken and that its expression is influenced by food deprivation.

Swan-Ganz catheter-induced pulmonary artery pseudoaneurysm formation: three case reports and a review of the literature

The use of Swan-Ganz catheters has increased tremendously since they were first introduced in 1970. Their ability to give vital hemodynamic measurements in critically ill patients makes their use invaluable when providing quality medical care. The formation of pulmonary artery (PA) pseudoaneurysm from a Swan-Ganz catheter-induced perforation of the PA is a rare but potentially fatal complication of Swan-Ganz catheter use. Three case presentations and a review of the literature are presented.

Surgical treatment of carcinoid tumours

Carcinoid tumours are the most common endocrine tumour of the gut comprising 75% of appendicular tumours and a third of ileal tumours. They are also an incidental finding in 1% of post mortems. Carcinoid syndrome however is rare and it is estimated that two cases would appear in a quarter of a million population over a decade. We have reviewed a consecutive series of carcinoid tumours accrued from 1976-1999 in order to further study the natural history of the disease and also to examine the relationship between pathological tumour size, extent of disease and prognosis for each tumour site. In this 19 year period 145 patients were treated for the disorder. The bronchus was the commonest site (35.9%) with appendix (24.8%) and ileal (13.8%) carcinoids comprising the majority of known primaries. Overall midgut carcinoids comprised 40.7% of the series with the carcinoid syndrome present in 20.3%. A significant group was constituted by those patients presenting with metastatic disease and an uncertain site of primary tumour (9.7%). Metastatic disease was not found on presentation or follow up in any patient with a foregut primary tumour less than 2 cm diameter or a midgut primary tumour less than 1 cm diameter; a direct correlation of size and metastases being found above these levels. Overall survival for all groups was 60% at 5 years with the best prognosis being seen in patients with bronchial or appendicular carcinoids. Other clinical features, pathology, extent of disease and prognosis of carcinoid tumour will be discussed along with the role of current management strategies.

Balloon angioplasty or stent placement in patients with azotemic renovascular disease: a retrospective comparison of clinical outcomes

In this study comparing functional outcomes of renal angioplasty alone (PTRA) or angioplasty with stent placement in patients with renal artery stenosis (> or =60%) and renal insufficiency, 69 patients were treated with PTRA or stent placement. After censoring, the PTRA group included 15 patients with a mean age of 75 years, mean serum creatinine (Cr) of 2.9 +/- 1.4 mg/dL, and mean follow-up of 10 months. The stent placement group included 40 patients with a mean age of 71 years, mean Cr of 2.6 +/- 1.2 mg/dL, and mean follow-up of 12 months. Stenting was performed primarily in four cases and after suboptimal angioplasty in the remainder. Benefit was defined as either stabilization (+/-20%) or improvement in serum Cr levels. Technical success was achieved in 16 of 17 (94%) PTRA patients and 55 of 58 (95%) patients receiving stents. Complications included one surgically repaired axillary pseudoaneurysm, one distal stent positioning requiring a second stent, one stent protruding 5 mm into the aorta, two dissections requiring additional stents, one retroperitoneal hematoma, and one intrarenal atheroembolism treated with thrombolysis. Three patients (mean initial Cr 3.9 mg/dL) required hemodialysis within 30 days of stenting. One patient discontinued dialysis after stenting. There were two procedure-related deaths. An overall benefit was seen in 40% of patients after PTRA and 66% of patients after stent placement. For the stent placement and PTRA groups, cumulative clinical benefit was 77% and 80%, respectively, at 3 months; 69% and 64%, respectively, at 6 months; 61% and 41%, respectively, at 12 months; and 48% and 14%, respectively, at 24 months. A 50% loss of cumulative benefit was seen 34 months after stenting and 11.5 months after PTRA. In the stent and PTRA groups, benefit was noted in 77% and 57%, respectively, of patients with an initial Cr of 2.3 or less, 53% and 25%, respectively, of patients with an initial Cr level higher than 2.3, and 44% and 17%, respectively, of patients with an initial Cr level of 3.0 mg/dL or more. For patients with renal insufficiency, renal artery stenting provides superior clinical results compared with PTRA, mostly because late deterioration occurs after PTRA. Outcomes are related to pretreatment serum Cr level.

Value of CT angiography for postoperative assessment of patients with iliac artery aneurysms who have received endovascular grafts

OBJECTIVE

The purpose of the study was to assess the usefulness of CT angiography for follow-up of patients with iliac artery aneurysms who have undergone endovascular treatment.

SUBJECTS AND METHODS

Twelve patients with iliac artery aneurysms (10 true aneurysms and two pseudoaneurysms) were examined with CT angiography within 1 week of receiving transfemorally placed endovascular grafts. All patients underwent follow-up CT angiography from 3 to 30 months (mean, 11 months) later. Follow-up CT angiography at 6 months or later (mean, 14 months) was also available in 10 patients. All studies were obtained after i.v. contrast administration using 3-mm collimation, 1.6-2.0 pitch, 2-mm retrospective reconstruction, and with subsequent three-dimensional rendering and multiplanar reformation. The shape and patency of the graft, perigraft thrombosis, and the size of the aneurysm were assessed.

RESULTS

All grafts remained patent and without deformity. Complete thrombosis of the aneurysm was shown by initial postoperative CT angiography in 11 patients and confirmed by follow-up studies. A single case of a perigraft leak was revealed by CT angiography and confirmed by follow-up angiography. No aneurysm showed change in size at late follow-up.

CONCLUSION

CT angiography is an accurate method for evaluating endovascular devices. CT angiography can be used as a primary technique for follow-up of patients who have undergone endovascular repair of iliac aneurysms.