Conflict of Interest Declaration
The ILCOR Continuous Evidence Evaluation process is guided by a rigorous ILCOR Conflict of Interest policy. The following Task Force members and other authors were recused from the discussion as they declared a conflict of interest: (none applicable)
The following Task Force members and other authors declared an intellectual conflict of interest and this was acknowledged and managed by the Task Force Chairs and Conflict of Interest committees: (insert names or declare none applicable)
CoSTR Citation
Perkins GD, Olasveengen TM, Mancini, MB , Chung S, Considine J, Kudenchuck P, Semeraro F, Smith C, Morley PT -on behalf of the International Liaison Committee on Resuscitation Basic Life Support Task Force.
Drowning Consensus on Science with Treatment Recommendations [Internet] Brussels, Belgium: International Liaison Committee on Resuscitation (ILCOR) Advanced Life Support Task Force, 2020 Jan 1. Available from: http://ilcor.org
Methodological Preamble
The continuous evidence evaluation process for the production of Consensus on Science with Treatment Recommendations (CoSTR) started with an ILCOR systematic review originally published in 2015 with evidence tables originally created by Quan and Bierens, and later updated by Perkins and Olasveengen with additional involvement of clinical content experts from the Basic Life Support Task Force. The update performed in September 2019 identified an additional 6 relevant cohort studies reporting on the influence of age,(Al-Quareshi 2017 1799) salinity,(Al-Quareshi 2017 1799; Jeong 2016 123; Omar 2017 237) submersion duration,(Al-Quareshi 2017 1799; Joanknecht 2015 123; Shenoi 2016 669) and whether the submersion was witnessed.(Al-Quareshi 2017 1799; Tobin 2017 39). This evidence for adult and pediatric literature was sought and considered by the Basic Life Support and Pediatric Task Forces. These data were taken into account when formulating the Treatment Recommendations.
PICOST
The PICOST (Population, Intervention, Comparator, Outcome, Study Designs and Timeframe)
Population: In adults and children who are submerged in water
Intervention: Does any particular factor in search-and-rescue operations (eg, duration of submersion, salinity of water, water temperature, age of victim)
Comparators: compared with no factors
Outcomes: Survival to hospital discharge with good neurological outcome and survival to hospital discharge were ranked as critical outcomes. Return of spontaneous circulation (ROSC) was ranked as an important outcome.
Study Designs: Randomized controlled trials (RCTs) and non-randomized studies (non-randomized controlled trials, interrupted time series, controlled before-and-after studies, cohort studies) are eligible for inclusion. It is anticipated that there will be insufficient studies from which to draw a conclusion; case series will be included in the initial search and included as long as they contain ≥ 5 cases.
Timeframe: All years and all languages were included as long as there was an English abstract; unpublished studies (e.g., conference abstracts, trial protocols) were excluded. Literature search updated to Oct 1st, 2019.
Consensus on Science
Age
For the critical outcome of survival with favorable neurologic outcome, we identified very-low-certainty evidence from 12 observational studies (downgraded for bias inconsistency, indirectness, and imprecision) comprising 4105 patients.(Frates RC Jr 1981 1006; Nagel 1990 422; Quan 1990 586; Anderson 1991 27; Niu 1992 81; Mizuta 1993 186; Kyriacou 1994 137; Al-Mofadda 2001 300; Blasco Alonso 2005 20; Nitta 2013 1568; Quan 2014 790) Of the 8 pediatric studies, 6 found that young age, variably defined as less than 3, 4, 5, or 6 years, was not associated with favorable neurologic outcome.(Frates RC Jr 1981 1006; Nagel 1990 422; Quan 1990 586; Niu 1992 81; Mizuta 1993 186; Al-Mofadda 2001 300) A single pediatric study including 166 children aged less than 15 years reported better outcomes in children aged less than 5 years (RR, 0.12; 95% CI, 0.03–0.44).(Kyriacou, 1994, 137)
Four studies considered drowning victims of all ages; 3 found no relationship between age and outcome.(Anderson 1991 27; Blasco Alonso 2005 20; Nitta 2013 1568) One reported worse outcomes among children aged greater than 5 years (RR, 0.66; 95% CI, 0.51–0.85).(Quan 2014 790)
For the critical outcome of survival, we identified very-low-certainty evidence (downgraded for risk of bias, inconsistency, indirectness, and imprecision) from 6 observational studies, which included 1313 patients.(Orlowski 1979 176; Mosayebi 2011 187; Claesson 2012 1072; Dyson 2013 1114; Claesson 2014 644; Vahatalo 2014 604) Three studies found that age was not associated with outcome.(Mosayebi 2011 187; Dyson 2013 1114; Vahatalo 2014 604) Two showed better outcomes associated with younger ages (less than 58 years: RR, 0.27; 95% CI, 0.08–0.96(Claesson 2012 1072); less than 46 years: RR, 0.98; 95% CI, 0.99–0.99),(Claesson 2014 644) and 1 favored older age (3 years or older: RR, 1.51; 95% CI, 1.19–1.9).(Orlowski 1979 176)
EMS Response Interval
No studies were identified that addressed the critical outcome of survival with favorable neurologic outcome.
For the critical outcome of survival, we identified very-low-certainty evidence (downgraded for risk of bias, indirectness, and imprecision) from 2 observational studies, including 746 patients in the Swedish EMS OHCA registry.(Claesson 2008 381; Claesson 2012 1072) EMS response intervals of less than 10 minutes were associated with better survival: RR of 0.29 (95% CI, 0.13–0.66)(Claesson 2008 381) and reported OR of 0.44 (95% CI, 0.06–0.83).(Claesson 2012 1072)
Salinity
For the critical outcome of survival with favorable neurologic outcome, we identified very-low-certainty evidence (downgraded for risk of bias, indirectness, and imprecision) from 6 observational studies(Mizuta 1993 186; Blasco Alonso 2005 20; Forler 2010 14; Quan 2014 790) which included 3584 drowning victims, of which 980 occurred in salt water and 2604 in fresh water. Two showed salt water was associated with better outcomes (RR, 1.3; 95% CI, 1.12–1.5 (Blasco Alonso 2005 20) ; RR, 1.2; 95% CI, 1.1–1.4 (Mizuta 1993 186)), and 4 showed water type was not associated with outcome (RR, 1.1; 95% CI, 0.95–1.2 (Forler 2010 14) ; RR, 1.14; 95% CI, 0.9–1.4 (Quan 2014 790) RR, 1.1; 95% CI 0.70 – 1.72 (Jeong 2016 1799); RR 1.15 ;95% CI 0.91 – 1.45 (Al-Quareshi 2017 1799)).
For the critical outcome of survival, we identified very-low-certainty evidence (downgraded for risk of bias imprecision, inconsistency, indirectness, and imprecision) from 5 studies.(Orlowski 1979 176; Bierens 1990 1390; Dyson 2013 1114) One reported better outcomes for salt water (RR, 1.34; 95% CI, 1.19–1.52),(Bierens 1990 1390) 3 showed no difference (RR, 1.22; 95% CI, 0.95–1.56),(Orlowski 1979 176) RR 0.88; 95% CI, 0.40 – 1.92 (Jeong 2016 1799); RR 0.94; 95% CI, 0.62 – 1.4, (Omar 2017 237) and 1 showed worse survival in cases with salt water drowning (RR, 0.18; 95% CI, 0.03–1.43).(Dyson 2013 1114)
Submersion Duration
For the purposes of this review, we considered studies in 3 groups. We defined those with short submersion intervals (less than 5–6 minutes), those with intermediate duration (less than 10 minutes), and those with prolonged submersion intervals (less than 15–25 minutes).
Short Submersion Intervals (Less Than 5–6 Minutes).
For the critical outcome of survival with favorable neurologic outcome, we identified moderate-certainty evidence from 15 observational studies (downgraded for bias and indirectness, upgraded for dose response), which included 2746 cases.(Kruus 1979 315; Frates RC Jr 1981 1006; Quan 1990 586; Anderson 1991 27; Niu 1992 81; Mizuta 1993 186; Kyriacou 1994 137; Graf 1995 312; Al-Mofadda 2001 300; Torres 2009 234; Quan 2014 790; Kieboom 2015 h418) All studies noted worse outcomes among patients with submersion durations exceeding 5 minutes (RRs ranged between 0.05 (Quan 2014 790) and 0.61. (Kyriacou 1994 137)) The 943/1075 patients (87.7%) who had outcome information available and were submerged for short durations had good outcomes compared to 139/1238 (11.2%) with longer submersion durations.
For the critical outcome of survival, we identified low-certainty evidence (downgraded for risk of bias, indirectness, and imprecision; upgraded for dose response) from 6 observational studies comprising 392 cases.(Orlowski 1979 176; Kaukinen 1984 34; Bierens 1990 1390; Veenhuizen 1994 906; Mosayebi 2011 187) All studies noted worse outcomes among patients with prolonged compared to short submersion durations (RRs ranged between 0.27(Kaukinen 1984 34) and 0.83 (Veenhuizen 1994 906)). The 204/217 patients (94.0%) submerged for short durations had good outcomes compared to 54/98 (55.1%) with longer submersion durations.
Intermediate Submersion Intervals (Less Than 10 Minutes).
For the critical outcome of survival with favorable neurologic outcome, we identified moderate-certainty evidence (downgraded for bias, indirectness, and imprecision; upgraded for dose response) from 9 observational studies that included 2453 cases.(Kruus 1979 315; Quan 1990 586; Quan 1992 909; Mizuta 1993 186; Kyriacou 1994 137; Graf 1995 312; Suominen 1997 111; Quan 2014 790; Kieboom 2015 h418) All studies noted worse outcomes among patients with prolonged submersion durations compared with intermediate submersion durations (RRs ranged between 0.02 (Quan 2014 790) and 0.45 (Kyriacou 1994 137; Graf 1995 312)). The 787/1019 patients (77.2%) submerged for intermediate durations had good outcomes compared to the 36/962 (3.7%) with longer submersion durations.
For the critical outcome of survival we identified low-certainty evidence (downgraded for bias indirectness and imprecision; upgraded for dose response) from 2 observational studies (Bierens 1990 1390; Panzino 2013 178) comprising 121 cases. The first study (Bierens 1990 1390) reported 56/73 (77%) of those submerged for less than 10 minutes survived compared with none of the 7 patients who were submerged for more prolonged periods survived (RR not estimable; absolute difference 76.7%; 39.7%–94.9%). The second study (Panzino 2013 178) also noted better survival among those submerged for less than 10 minutes (46/50 (96%) survived) compared with those submerged for more than 10 minutes (2/5 (40%) survived).(Panzino 2013 178)
Prolonged Submersion Intervals (Less Than 15–25 Minutes).
For the critical outcome of survival with favorable neurologic outcome, we identified low-certainty evidence (downgraded for bias and imprecision, upgraded for dose response) from 3 observational studies that included 739 cases.(Quan 1990 586; Mizuta 1993 186; Kieboom 2015 h418) In one study (n=398),(Mizuta 1993 186) submersion less than 20 minutes was associated with improved survival (289/370 (78%) good outcome versus 1/27 (4%) good outcome; RR, 0.05; 95% CI, 0.01–0.31). The second study (Quan 1990 586) reported better outcomes if submersion duration was less than 25 minutes (68/101, or 67%) versus submersion duration longer than 25 minutes (0/4, 0%).(Quan 1990 586) The fourth study, which included hypothermic children in cardiac arrest, observed 12/66 (18%) survivors who were submerged for less than 25 minutes compared with 0/39 who were submerged for more than 25 minutes.(Kieboom 2015 h418)
For the critical outcome of survival, we identified very-low-certainty evidence (downgraded for bias, indirectness, and imprecision) from a single study (Kaukinen 1984 34) comprising 49 patients. Cases with a submersion interval of less than 15 minutes had an overall survival rate of 82% (33/39) compared with none of the 2 victims whose submersion duration exceeded 15 minutes (RR not estimable; absolute difference, 84.6%; 17.3%–92.8%).
Water Temperature
For the critical outcome of survival with favorable neurologic outcome, we identified very-low-certainty evidence (downgraded for bias, inconsistency, indirectness, and imprecision) from 2 studies (Quan 2014 790; Kieboom 2015 h418) of 1254 cases. The largest study (n=1094) included all unintentional drownings in open waters (lakes, ponds, rivers, ocean) in a single large region, collected from medical examiners, EMS systems, and all regional hospitals.(Quan 2014 790) Water temperatures were measured within a month of the drowning incident. Univariate analysis according to temperatures less than or greater than 6°C or less than or greater than 16°C found no difference in neurologic survival: RR, 1.11 (95% CI, 0.9–1.37); RR, 1.02 (95% CI, 0.81–1.27); absolute difference, −0.5% (−7.5% to 6.1%), respectively. Multivariate analysis also showed that water temperature was not associated with outcome. The second study included 160 hypothermic children who required resuscitation after submersion. Water temperatures were estimated based on the season. Submersion in the winter (water temperature estimated as 0°C–8°C) was associated with better outcomes than submersion in spring or summer (water temperature 6°C–28°C) (univariate OR, 4.55; 95% CI, 1.37–15.09).
For the critical outcome of survival, we identified very-low-certainty evidence (downgraded for risk of bias, indirectness and imprecision) from a single study (Claesson 2012 1072) that included 250 patients. This study included only drowning victims who had an OHCA and received EMS care, and it included those with intentional (suicide and homicide) drowning. This study showed no relationship between water temperature less than or greater than 15°C and outcome (RR, 0.94; 95% CI, 0.34–2.62; absolute difference, 0.36%, −6.4% to 6.5%).
Witnessed Status
The definition of witnessed versus unwitnessed was inconsistently defined in the studies reviewed. It was often unclear if witnessed related to the submersion or time of cardiac arrest.
For the critical outcome of survival with favorable neurologic outcome, we found very-low-certainty evidence (downgraded for indirectness and imprecision) from 3 observational study (Nitta 2013 1568) involving 2707 patients. Two studies reported better neurological outcomes when the event was witnessed (unadjusted OR, 16.33; 95% CI, 5.58–47.77). Adjusted OR, 11.8; 95% CI, 2.84–49.08); (Nitta 2013 1568) unadjusted OR, 2.6; 95% CI 1.69–4.01; adjusted OR 3.27, 95% CI 2.0–5.36.(Tobin 2017 39). Neither of the analysis analyses included submersion duration, which several studies have reported is an independent predictor.
For the critical outcome of survival, we found low-certainty evidence (downgraded for risk of bias, indirectness, and imprecision) from 4 studies (Claesson 2008 381; Dyson 2013 1114; Nitta 2013 1568; Claesson 2014 644) involving a total of 2857 victims. Two studies (Claesson 2012 1072; Claesson 2014 644) were from the same EMS system, and both used multivariate analysis. The smaller study (255 victims) showed that witnessed status was not significantly associated with improved survival (RR, 0.55; 95% CI, 0.17–1.75; absolute difference, 3%; −3.1% to 11.2%).(Claesson 2012 1072) However, in the larger subsequent study from that same EMS system, witnessed status predicted better outcome (reported univariate analysis P=0.05; adjusted OR, 2.5; 95% CI, 1.38–4.52).(Claesson 2014 644) A further study (Dyson 2013 1114) showed no association of witnessed status with improved survival (RR, 0.82; 95% CI, 0.26–2.59). A large observational study from Japan (Nitta 2013 1568) reported an unadjusted OR of 7.38 (95% CI, 3.81–14.3) and an adjusted OR of 6.5 (95% CI, 2.81–15.02), although the unusual population of much older victims, most drowning in bathtubs, with very low favorable outcomes limited the generalizability of these findings.
Treatment Recommendations
We recommend that submersion duration be used as a prognostic indicator when making decisions surrounding search and rescue resource management/operations (strong recommendation, moderate-certainty evidence for prognostic significance).
We suggest against the use of age, EMS response time, water type (fresh or salt), water temperature, and witness status when making prognostic decisions (weak recommendation, very-low-certainty evidence for prognostic significance).
We acknowledge that this review excluded exceptional and rare case reports that identify good outcomes after prolonged submersion in icy cold water.
Justification and Evidence to Decision Framework Highlights
The 2015 Consensus on Science and Treatment Recommendation benefitted from significant feedback from ILCOR Task Forces and through public consultation, the drowning research and clinical community. In making the original recommendations, the task force placed priority on producing simple guidance that may assist those responsible for managing search and rescue operations. The public comments highlighted the difficult moral dilemmas facing the rescuer in these often emotionally charged and fast-moving environments requiring dynamic risk assessments which consider the likelihood a favourable outcome with the risks posed to those undertaking the rescue. The key finding of the 2015 review was that submersion durations of less than 10 minutes are associated with a very high chance of favorable outcome, and submersion durations more than 25 minutes are associated with a low chance of favorable outcomes.
The findings from the six new papers identified in this update,(Al-Quareshi 2017; Jeong 2016 123; Omar 2017 237; Joanknecht 2015 123; Shenoi 2016 669; Tobin 2017 39;] are consistent with the 2015 treatment recommendation. The previously identified limitations of this review (exclusion of factors after the victim is rescued e.g. bystander CPR (Fukuda 2019 111; Tobin 2017 39; Fukuda 2019 166) and specialist interventions e.g. ECMO (Bauman 2019 29; Biermann 2018 e751; Draggan 2016 86; Romlin 1995 e521; Hilmo 2014 1204; Seodudy 2017; Burke 2016 19; Weuster 2016 157] lack of prospective validation of submersion duration as a clinical decision rule) persist. Similarly, rare and exceptional case reports of survival after prolonged (>30 minutes) submersion continue to be reported.(Mann 2019; Romlin 2015 e-521; Draggan 2016 86), highlighting the need for individual, case by case decisions which balance risk and potential for benefit.
Knowledge Gaps
Submersion duration should be assessed in all future drowning studies and part of multivariate analyses. To better clarify the value of this predictor, studies should include all victims rescued from the water and not only sub-categories.
Attachments
Evidence-to-Decision Table: BLS-856 Drowning
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