Rahul Balasubramanian1, Jobin Jose Maprani2, Sandra Paulson3, Suresh G4, S Manu Ayyan5, Vimal Rohan K6

1Department of Emergency Medicine, St James Hospital, Chalakudy, Thrissur, Kerala, India
2Department of Emergency Medicine, Amala Institute of Medical Sciences, Thrissur, Kerala, India
3Department of Community Medicine, Amala Institute of Medical Sciences, Thrissur, Kerala, India
4Department of Emergency Medicine, Government Medical College, Kannur, Pariyaram, Kerala, India
5Department of Emergency Medicine & Trauma, Jawaharlal Institute of Postgraduate Medical Education & Research, Puducherry, India
6Department of Emergency Medicine, Government Medical College Kannur, Pariyaram, Kerala, India

Keywords: Corrosive, dialysis, emergency medicine, formic acid, intubation, mortality


OBJECTIVE: The objective is to evaluate the outcome of early emergency intubation and early dialysis in formic acid (FA) poisoning and to determine the clinical features associated with its mortality.

METHODS: It is a retrospective cohort study of 78 patients who presented to the emergency medicine department from July 2008 to June 2015 with alleged history and clinical features of FA poisoning. The outcome of early intubation and early dialysis was studied in terms of 7-day and 30-day mortality. The outcome was compared in severe and not severe groups separately. Severity was graded according to Med-Tu chart used for corrosive poisoning.

RESULTS: In the severe group (n = 53), early dialysis was done in 15 patients. There was 53% (n = 8) 30-day mortality. In the group where early dialysis was not done there was a significant increase in mortality 92.1% (n = 35). This was statistically significant with a P = 0.003. In a similar fashion 7-day mortality was analyzed in the severe group where mortality was higher when early dialysis was not done. In not severe group early dialysis has minimally decreased the mortality. Early intubation in severe group did not demonstrate any mortality benefit. Patients who were intubated early and not intubated early had equally high mortality. In not severe group, intubation could not make any significant difference in mortality.

CONCLUSION: In this retrospective study, we observed that early dialysis in the severe group has a better outcome in terms of 7-day and 30-day mortality.


Formic acid (FA) is a toxic chemical compound that has application in both agriculture and industry. Rubber latex is coagulated using a diluted solution of FA. In rubber-growing regions, rubber processing is done as a cottage business, which leaves FA readily available in homes. Its simple accessibility in homes makes it a popular agent for intentional self-harm in the northern part of Kerala. Other sectors that employ FA include paper, tanning, electroplating, and disinfectant manufacturing.[1]

FA poisoning has a significant death rate. Because FA is corrosive, irritating, and fuming, FA toxicity affects the respiratory system.[2] When they arrive at the emergency department (ED) on time, their airway is protected by early endotracheal intubation while under laryngoscopic visualization. This guarantees sufficient oxygenation of the tissue, which improves the prognosis. FA can be dialyzed because of its comparatively low molecular weight. Since hemodialysis reverses the systemic effects of FA, it proves to be an effective treatment.[3,4] Renal failure and severe metabolic acidosis are caused by FA. FA is a protoplasmic toxin that damages cells by acting directly on proteins or indirectly on tissue ions.[5]

Although FA poisoning and intentional self-harm are relatively common in our state, there are few research on the subject in the literature. Evaluating the effects of these two interventions, which are implemented one after the other in their respective departments, is extremely insightful. In light of this, a study was carried out to determine how early intubation and dialysis enhance survival in cases of intentional self-harm involving the intake of FA.

Material and Methods

The study is carried out at a teaching institution at the tertiary level that handles an extensive number of emergencies in the state’s northern region. This retrospective cohort study was carried out on patients who were diagnosed with intentional self harm using FA and who were older than 18 years. After receiving approval from the institute’s ethical and research committees, patients who were diagnosed with intentional self harm using FA and admitted to the hospital between July 2008 and August 2015 were included as study participants. After getting clearance from the Ethics Committee and Research Committee of the institute, demographic data, symptoms at presentation to the ED, investigations, and acute complications (hematuria, respiratory distress, oropharyngeal burns, hematemesis, melena, drooling of saliva, vomiting, gastrointestinal [GI] perforation, and dyspnea) were recorded from the case records as well as telephonic interviews. Patient consent was not taken due to the retrospective nature of the study; secondary data from the patient’s case sheet were collected on a case-tocase basis. The study was certified by the Institutional Ethical and Research Committee of Academy of Medical Sciences Pariyaram, Kannur, Kerala, India, as per reference no. 23/2014/ACME dated February 07, 2014.

All the patients were managed by securing airway patency and supportive care that included intravenous fluids, correction of acidosis, and prophylactic antibiotics, along with blood transfusions and hemodialysis when indicated.

Depending on the severity of their toxic exposure, patients were split into two groups: Severe and not severe. The Med-Tu chart, which is used to grade corrosive toxicity, was followed for determining the severity of the condition.[6] In each group, the results of early dialysis and early intubation were examined independently. Any intubation performed within 4 h of FA use is considered early intubation. Dialysis completed 5 h or less after ingesting FA was regarded as early.[6]

Criteria for inclusion

Any patient over the age of eighteen who came to the ED claiming to have a history of intentional self-harm using FA exclusion criteria: Patients whose record data could not be obtained.

For descriptive statistics, the continuous variables are presented as median with interquartile range (IQR) and categorical variables as absolute numbers and percentages. All data were assessed for the normality assumption by a Shapiro–Wilk test. Differences between the groups based on mortality were compared with independent-samples t-test for the continuous variables and Chi-square test (with yates continuity correction) for the categorical data. The association of symptoms and signs on admission (hematuria, respiratory distress, oropharyngeal burns, hematemesis, melena, drooling of saliva, vomiting, GI perforation, dyspnea), concentration of FA used for consumption, as well as complications of FA poisoning and mortality (30-day mortality), were analyzed using Chi-squared tests. The study was certified by the Institutional Ethical and Research Committee of Academy of Medical Sciences, Pariyaram, Kannur, as per reference no. 23/2014/ACME dated February 07, 2014.


During the study, a total of 90 patients had presented to the ED with deliberate self-harm with FA out of which only 78 were included in the study since the records of the 12 study participants were not available. Figure 1 shows the flow diagram of the study participants. Patients were graded to severe and not severe in accordance with Med-Tu chart. 53 (68%) were severe and 25 (32%) were not severe. Table 1 shows the demographic, clinical, and biochemical profile of the study participants.

Figure 2 depicts the different interventions that the patients underwent. The different combinations and their frequency are clearly mentioned. Patients were graded to severe and not severe in accordance with Med-Tu chart. 53 (68%) were severe and 25 (32%) were not severe. The primary outcomes were 7-day and 30-day mortality. Out of 25 cases, 21 (84%) had no mortality in 30 days. In the severe group, 43 (81.1%) had mortality in 30 days. Only 10 (18.9%) patients survived after 30 days in severe group. In 78 patients, 47 (60.2%) had 30-day mortality. Total mortality on day one and 30 days were 47% and 60%, respectively.

At the conclusion of 30 days, Table 2 compares the clinical, biochemical, and demographic features of deceased individuals and those who survived.

Differences between the groups based on mortality were compared with an independent-sample t-test for the continuous variables and Chi-square test (with yates continuity correction) for the categorical data. The P < 0.05 was taken to be statistically significant. The difference in the mortality pattern of patients who underwent early dialysis and early intubation can be seen in the data presented in Tables 3 and 4.


There was a noteworthy rise in mortality of 92.1% (n = 35) in the group that did not receive early dialysis. At P = 0.003, this was statistically significant. The severe group’s 7-day mortality was examined in a similar manner. The death rate for patients who started dialysis early was 53% (n = 8). When early hemodialysis was not performed, mortality rose to 84.2% (n = 32)(P = 0.032). Three patients (12%) in the not-severe group(n=25) underwent early dialysis, and after 30 days, there was no fatality. Twenty-two patients did not receive early dialysis. 18.2% of the population died (P=0.420). When 7-day mortality was calculated, there was no mortality in the group receiving early dialysis, and in the group who did not, there was a mortality rate of 13% (n = 3) (P = 0.586). The results that we got in the study are in consensus with the data in the literature.[7,8]

Severe intravascular hemolysis is indicated by the rapid appearance of hemoglobinuria. Studies carried out on animal models in vivo and in vitro are less frequent because hemodialysis expedites the removal of FA and helps rectify metabolic acidosis. Hemodialysis lowers the amounts of FA in blood and other bodily fluids, as demonstrated by endogenous and hemodialysis elimination of FA (Fick principle).[9] In the absence of dialysis, the elimination half-life of FA is 6.04 ± 3.26 h (P = 0.004). This exceeds the elimination half-life (1.80 ± 0.78 h) determined during dialysis. This evidence clearly shows that systemic toxicity is reduced when FA is consumed early in the dialysis process.[10] In addition, early dialysis helps lessen the strain on the liver, where it gets metabolized as demonstrated in rat liver models.[11]

A case report presents yet another piece of data supporting the importance of early hemodialysis.[12] In one instance, the concentration of the blood drawn upon hospital admission was 370.3 µg/mL; however, after 6.5 h of hemodialysis, it dropped to 13.9 µg/mL. It demonstrates how early hemodialysis lowers blood FA’s absolute concentration.[13-20] In 47.1% of instances (n = 25) in the severe category, early intubation was performed. Within 30 days, there was an 80% (n = 20) mortality rate in this group.

In 28 patients, early intubation was not done. The mortality rate in this group was 82.1% (P = 1.00). Similarly, after 7 days, the mortality rate for the group receiving early intubation (n = 25) was 76% (n = 19), while the mortality rate for the group receiving delayed intubation (n = 28) was 75% (P = 0.93). Only two patients (8%) in the not severe group (n = 25) underwent early intubation; both patients lived for a full 30 days. Of the patients, 23 (92%) did not have an early intubation, and the mortality rate was 17.4% (n = 4) (P = 0.520). In a similar vein, just two patients underwent early intubation in a span of 7 days, and both of them recovered. An IQR of 30 indicates the importance of early hemodialysis, grouping where early intubation was not done, mortality was 13% (n = 3) (P = 0.586). When poisoning is severe, the outcome may be more dependent on systemic effects and other local effects of FA, such as GI perforation, than the outcome due to intubation.

The greatest predictors for mortality in our study were dyspnoea on presentation, GI perforation, free fluid in the abdomen, and visual symptoms, with percentages of 100%, 100%, 93.8%, and 83.3%, respectively. 33.4% (101) of mucosal erosions and 32.1% (97) of oral ulcerations in Dalus et al.’s study had severe mouth burns. They came to the conclusion that one of the best indicators of death is oropharyngeal burns.

Oropharyngeal burns are one of the factors we used in our study to grade burn severity. In addition, a high correlation between oropharyngeal burns and death is demonstrated by our study. Of the 49 (62.8%) patients with oropharyngeal burns, 40 (81.6%) died within 30 days. Twenty-two (37.2%) of the patients who did not have oral burns died within 30 days (P = 0.00). Saliva drooling was observed in 40 (51.3%) of the patients. Twenty-seven (67%) of the individuals in the group died within 30 days. Yet another clinical characteristic for grading severity is the drooling of saliva. In our analysis, 16 patients (20.5%) experienced perforation; of these, 15 (94%) died within 30 days (P = 0.002). According to a study by Dalus et al, 39 people (12%), had GI perforations. In this, there was a 100% death rate. Thus, the findings in both studies are comparable.[7,21]


1. This is a single-centred retrospective study, so can be subjected to selection bias. Which may affect the external validity of the findings

2. The time for early intubation was arbitrarily chosen

3. Loss of records results in selection bias and an overestimate or an underestimate of an association.


The study was conducted with the aim of assessing the outcome of early emergency intubation and early emergency dialysis in patients with deliberate self-harm with FA. We observed that early emergency dialysis of patients in the severe group significantly decreased 7-day (P = 0.033) mortality and 30-day (P = 0.003) mortality. In the not severe group, mortality was lower compared to the severe group but early dialysis has not significantly reduced the 7-day and 30-day mortality rates when compared to the severe group. Emergency clinicians should focus on the early emergency dialysis of patients presenting with FA ingestion. In the not severe group, the presence of clinical features associated with mortality has to be considered too.

How to cite this article: Balasubramanian R, Maprani JJ, Paulson S, Suresh G, Ayyan SM, Vimal Rohan K. Outcome of early emergency intubation and early emergency dialysis in deliberate self-harm with formic acid in a tertiary care center in South India: A retrospective cohort study. Turk J Emerg Med 2024;24:111-6.

Ethics Committee Approval

The study was certified by the Institutional Ethical and Research Committee of Academy of Medical Sciences Pariyaram, Kannur, Kerala, India, as per reference no. 23/2014/ACME dated February 07, 2014.

Author Contributions

RB: Conceptualization (lead); writing – original draft (lead); formal analysis (lead); writing – review and editing (equal). JM: Methodology (lead); writing – review and editing (equal). SP: Conceptualization (supporting); Writing – original draft (supporting); Writing – review and editing (equal). SG: Conceptualization (supporting); Project Administration (lead). MA: Software (lead); writing – review and editing (equal). VRK: Supervision (lead); Resources and Software (supporting).

Conflict of Interest

None Declared.

Financial Disclosure



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