Predictors and outcomes of withholding and withdrawal of life-sustaining treatments in intensive care units in Singapore: a multicentre observational study

BACKGROUND

Clinical practice guidelines on limitation of life-sustaining treatments (LST) in the intensive care unit (ICU), in the form of withholding or withdrawal of LST, state that there is no ethical difference between the two. Such statements are not uniformly accepted worldwide, and there are few studies on LST limitation in Asia. This study aimed to evaluate the predictors and outcomes of withholding and withdrawal of LST in Singapore, focusing on the similarities and differences between the two approaches.

METHODS

This was a multicentre observational study of patients admitted to 21 adult ICUs across 9 public hospitals in Singapore over an average of three months per year from 2014 to 2019. The primary outcome measures were withholding and withdrawal of LST (cardiopulmonary resuscitation, invasive mechanical ventilation, and vasopressors/inotropes). The secondary outcome measure was hospital mortality. Multivariable generalised mixed model analysis was used to identify independent predictors for withdrawal and withholding of LST and if LST limitation predicts hospital mortality.

RESULTS

There were 8907 patients and 9723 admissions. Of the former, 80.8% had no limitation of LST, 13.0% had LST withheld, and 6.2% had LST withdrawn. Common independent predictors for withholding and withdrawal were increasing age, absence of chronic kidney dialysis, greater dependence in activities of daily living, cardiopulmonary resuscitation before ICU admission, higher Acute Physiology and Chronic Health Evaluation (APACHE) II score, and higher level of care in the first 24 h of ICU admission. Additional predictors for withholding included being of Chinese race, the religions of Hinduism and Islam, malignancy, and chronic liver failure. The additional predictor for withdrawal was lower hospital paying class (with greater government subsidy for hospital bills). Hospital mortality in patients without LST limitation, with LST withholding, and with LST withdrawal was 10.6%, 82.1%, and 91.8%, respectively (p < 0.001). Withholding (odds ratio 13.822, 95% confidence interval 9.987-19.132) and withdrawal (odds ratio 38.319, 95% confidence interval 24.351-60.298) were both found to be independent predictors of hospital mortality on multivariable analysis.

CONCLUSIONS

Differences in the independent predictors of withholding and withdrawal of LST exist. Even after accounting for baseline characteristics, both withholding and withdrawal of LST independently predict hospital mortality. Later mortality in patients who had LST withdrawn compared to withholding suggests that the decision to withdraw may be at the point when medical futility is recognised.

Biological evaluation of hepatitis C virus helicase inhibitors

A small chemical library has been synthesized and assayed for inhibition of HCV helicase activity. This study provides the structure-activity relationship of the reported inhibitors, with emphasis placed on the aminophenylbenzimidazole moiety and the linkers. Our data highlight the importance of preserving the aminophenylbenzimidazole core and the hydrophobic linkers for biological activity. The development of a robust HCV helicase assay is also described.

Arylalkylidene rhodanine with bulky and hydrophobic functional group as selective HCV NS3 protease inhibitor

Arylalkylidene rhodanines 2(a-d) inhibit HCV NS3 protease at moderate concentrations. They are better inhibitors of other serine proteases such as chymotrypsin and plasmin. However, the selectivity of arylmethyliden e rhodanines (8a, 9a) with bulkier and more hydrophobic functional groups increases by 13- and 25-fold towards HCV NS3 protease respectively.

Isolation of a novel protein tyrosine phosphatase inhibitor, 2-methyl-fervenulone, and its precursors from Streptomyces

High-throughput screening identified an extract from Streptomyces sp. IM 2096 with inhibitory activity toward several protein tyrosine phosphatases (PTPs). Four 1,2,4-triazine compounds 2096A-D (1-4) were isolated from this extract and their structures elucidated by interpretation of spectroscopic data and confirmed by degradation and synthesis. The novel glycocyamidine derivatives 1 and 2 are diastereomers and may interconvert. Both are inactive in the PTP inhibition assay. Compounds 1 and 2 are unstable and partially decompose to 3 and glycocyamidine (5) at room temperature. Compound 3, known as MSD-92 or 2-methyl-fervenulone, is a broad-specificity PTP inhibitor with comparable potency to vanadate. The imidazo[4, 5-e]-1,2,4-triazine (4), inactive in the PTP-inhibition assay, may be a degradation product of 3.

Solid-phase synthesis of potential protein tyrosine phosphatase inhibitors via the Ugi four-component condensation

A library of 108 alpha,alpha-difluoromethylenephosphonic acids was prepared by Ugi four-component condensation using Rink-NH2 resin, 4-[(diethoxyphosphinyl) difluoromethyl]benzoic acid, and a set of 18 aldehydes and 6 isonitriles. Following resin cleavage, the diethylphosphonate esters were hydrolyzed with trimethylsilyl bromide to yield the free acids which were assayed for inhibition of PTP alpha, PTP beta and PTP epsilon.

Binary sibling neuronal cell fate decisions in the Drosophila embryonic central nervous system are nonstochastic and require inscuteable-mediated asymmetry of ganglion mother cells

Asymmetric cell division is a widespread mechanism in developing tissues that leads to the generation of cell diversity. In the embryonic central nervous system of Drosophila melanogaster, secondary precursor cells-ganglion mother cells (GMCs)-divide and produce postmitotic neurons that take on different cell fates. In this study, we show that binary fate decision of two pairs of sibling neurons is accomplished through the interplay of Notch (N) signaling and the intrinsic fate determinant Numb. We show that GMCs have apical-basal polarity and Numb localization and the orientation of division are coordinated to segregate Numb to only one sibling cell. The correct positioning of Numb and the proper orientation of division require Inscuteable (Insc). Loss of insc results in the generation of equivalent sibling cells. Our results provide evidence that sibling neuron fate decision is nonstochastic and normally depends on the presence of Numb in one of the two siblings. Moreover, our data suggest that the fate of some sibling neurons may be regulated by signals that do not require lateral interaction between the sibling cells.

On the functional overlap between two Drosophila POU homeo domain genes and the cell fate specification of a CNS neural precursor

The approximately 200 distinct neurons comprising each hemisegment of the Drosophila embryonic CNS are derived from a stereotypic array of approximately 30 progenitor stem cells, called neuroblasts (NBs). Each NB undergoes repeated asymmetric divisions to produce several smaller ganglion mother cells (GMCs), each of which, in turn, divides to produce two neurons and/or glia cells. To understand the process by which cell type diversity is generated in the CNS, we are focusing on identifying genes that affect cell identity in the NB4-2 lineage from which the RP2 motoneuron is derived. We show here that within the early part of the NB4-2 lineage, two closely linked and structurally related POU homeo domain genes, pdm-2 (dPOU28) and pdm-1 (dPOU19), both encode proteins that accumulate to high levels only in the first GMC (GMC4-2a) and not in its progeny, the RP2 motoneuron. Our results from the genetic and developmental analysis of pdm-1 and pdm-2 demonstrate that these genes are not required for the birth of GMC4-2a; however, they are both involved in specifying the identity of GMC4-2a and, ultimately, in the genesis of RP2 neurons, with pdm-2 being the more dominant player in this process. In mutant animals where both pdm-1 and pdm-2 functions are removed, GMC4-2a fails to express markers consistent with a GMC4-2a identity and no mature (Eve protein expressing) RP2 neurons are produced. We demonstrate that in some mutant combinations in which no mature RP2 neurons are produced, some GMC4-2a cells can nevertheless divide. Hence, the failure of the POU mutants to produce mature RP2 neurons is not attributable to a block in GMC4-2a cell division per se but, rather, because the GMC4-2a cells fail to acquire their correct cellular identity.

Two closely linked Drosophila POU domain genes are expressed in neuroblasts and sensory elements

We have characterized two Drosophila POU genes designated dPOU-19 and dPOU-28. These genes are transcribed as 3.1- and 2.2-kilobase mRNAs, respectively, which accumulate maximally during the first 12 hr of embryogenesis. The mRNAs encode 601- and 475-amino acid deduced proteins; their POU domains are most related to those of the human OCT1 and OCT2. Both genes give similar nervous system expression patterns and map to an indistinguishable site at 33F on the cytological map. Transcription of the genes is first observed in the cellular blastoderm. In the course of embryonic development, expression is observed in the neuroectoderm, with subsets of neuroblasts in the procephalic and germband central nervous system as well as a subset of peripheral nervous system elements. The expression patterns of the two POU genes suggest a possible functional role for these putative transcription factors in neurogenesis and neurospecification.

Induction of labour using a concentrated oxytocin infusion administered in geometric progression in a peristaltic infusion pump

A new regime for oxytocin titration was introduced into the Labour Ward, Alexandra Hospital, Singapore. It utilises an oxytocin infusion of 10, 20 or 40 mU/ml administered in geometric progression in a peristaltic infusion pump. A total of 91 patients classified according to parity and cervical score were studied. An overall vaginal delivery rate of 92.3% was obtained. The mean induction-delivery time for nulliparous and multiparous patients was 5.3 hrs (+/- 2.6 hrs) and 3.6 hrs (+/- 1.9 hrs) respectively. Almost 90% of patients who had a successful induction required only one pint of infusion. Of those babies who were delivered vaginally, all had an Apgar score of 7 or more at 5 minutes.