Severe poisonings in Sweden : demography, intensive care, and death

Background: Poisonings are common and diverse in their origins, clinical presentations, and outcomes. Poisoning accounts for a substantial number of hospital admissions with need for a higher level of care. The hospital mortality is low but never the less around 1,000 people die from poisoning each year in Sweden. Patients suffering from the most severe poisonings are treated in the intensive care unit and may suffer a cardiac arrests prior to admission or during hospitalisation. A significant proportion of patients dies outside of hospital. Robust information regarding these patients is scares.

Aim: The overall aim of the thesis was to increase knowledge about patients suffering from severe poisoning in Sweden. The specific aims were to describe national data for characteristics, short and long-term mortality for patients treated in the intensive care unit (ICU) due to poisoning, to compare key characteristics and outcomes between out-of-hospital cardiac arrest caused by poisoning vs. other causes, and to describe the national patient population deceased due to poisoning including toxicology results.

Methods and results: Four epidemiological studies are included in the thesis. Study I and II were cohort studies based on three national registers, the Swedish intensive care register, the national patient register, and the cause of death register. Variables were collected for all adult patients treated in a Swedish ICU during 2010-2011, with 8,155 registered ICU admissions. Patients had a median age of 38 years and men and women were equally represented. Almost half of the patients had a previous hospitalisation due to poisoning. Approximately 30% were unconscious on admission to the ICU and 14.6% were mechanically ventilated during their stay. The in-hospital mortality was 1.9% and the subgroup with the highest mortality was older men without a previously known poisoning. The population’s one-year mortality was 4.5% and also here it was higher for older men. The whole population had a nine-fold increased risk of death during the year following ICU admission compared to population based controls. The highest mortality was found in women between 19-39 years, with a 50 times higher mortality compared to controls and the clear majority of deaths after hospital discharge (94%) was caused by suicide and/or accidents. Study III was a cohort study based on the Swedish register for cardiopulmonary resuscitation, the national patient register, and the cause of death register. All adult patients with an out-of-hospital cardiac arrest (OHCA) during 2007-2021 were included. In total, 66,261 OHCA patients were included, of whom 5.2% were found to receive a diagnosis of poisoning. Poisoned OHCA patients had a median age of 43 years (compared to 73 of the whole group) and included more men. The cardiac arrests due to poisoning were less likely to be witnessed and less likely to have a shockable first rhythm. Despite this, they had a somewhat lower mortality than the other cardiac arrests groups (84% vs 88%). Study IV was a cohort study which included all adult patients who died from poisoning between 2000-2021, according to the cause of death register. Variables were also added from the national forensic database. The results showed that 1.3% of annual deaths in Sweden were caused by poisoning (n poisoning deaths=27,057/n deaths=2,018,495). Patients who died due to poisoning had a median age of 53 years and 70% were men. In total, 87% of these deaths underwent some sort of forensic examination. Drugs (synthetic narcotics and opioids) caused 46% of deaths and alcohols caused 33%. Positive toxicologic tests were found in 83% of patients. Temporal trends show an increase in opioids, antidepressants/neuroleptics, and sedative/antiepileptic substances in femoral blood of patients who died around 2014-2017.

Conclusion: Poisoning is a common cause of ICU admission, non-medical OHCA, and death in Sweden. Many patients have a previous history of poisoning before ICU admission, and a mix of substances is the most common poisoning. The ICUmortality is low but the long-term mortality is high for these often young patients, and death is in many cases caused by a new poisoning. Patients with OHCA due to poisoning are younger than patients with OHCA of other causes and have better survival. Deaths out of hospital are often due to illicit drug use.

List of scientific papers

I. Lindqvist E, Edman G, Hollenberg J, Nordberg P, Ösby U, Forsberg S. Intensive care admissions due to poisoning. Acta Anaesthesiol Scand. 2017 Nov;61(10):1296-1304.
https://doi.org/10.1111/aas.13005

II. Lindqvist E, Edman G, Hollenberg J, Nordberg P, Forsberg S. Longterm mortality and cause of death for patients treated in Intensive Care Units due to poisoning. Acta Anaesthesiol Scand. 2019 Apr;63(4):500-505.
https://doi.org/10.1111/aas.13289

III. Lindqvist E, Hollenberg J, Ringh M, Nordberg P, Forsberg S. Out-ofhospital cardiac arrest caused by poisoning – a Swedish nationwide study over 15 years. Resuscitation. 2023 Dec 1;193:110012.
https://doi.org/10.1016/j.resuscitation.2023.110012

IV. Lindqvist E, Hollenberg J, Ringh M, Nordberg P, Svensson L, Druid H, Forsberg S. Death and forensic toxicology in Swedish poisonings. [Submitted]