Field Study on Intravenous Iloprost for Treatment of Severe Frostbite at High Altitude

Patients will be assessed using Cauchy classification. Proportion of patients presenting with grade 3 + 4 frostbite in relation to the total number of patients with frostbite presenting at Everest ER Unit/format: proportion (%)

The proportion of the number of patients who successfully completed at least one round of iloprost treatment under field conditions in relation to the number of eligible patients. Denominator explicitly: eligible grade 3-4 patients (Cauchy classification) Unit/format: proportion (%)

Unit/format: time (hours or minutes)

Unit/format: proportion (%) Adverse effects will be graded using CTCAE (CTCAE = Common Terminology Criteria for Adverse Events) severity criteria.

Proportion of mild adverse effects in the field setting will then be compared with in-hospital settings.

Unit/format: proportion (%) Adverse effects will be graded using CTCAE (Common Terminology Criteria for Adverse Events) severity criteria. In a second step proportion of severe adverse events during field treatment will be compared with proportions of in-hospital treatment

Proportion of discontinued field treatments in relation to all initiated field treatments.

Unit/format: proportion (%) + categorical reason counts

Unit/format: proportion (%) Number of treatments discontinued due to adverse reactions in relation to all treatments discontinued (both in the field)

Notes and reports will be analysed using a thematic analysis approach to categorise logistical challenges.

Reported as: themes/categories with illustrative summaries (qualitative)

Number of logistical challenges, classified using a logistical challenge themes arising from qualitative analysis of field notes and staff reports. Possible themes expected include challenges related to equipment availability or functionality, personnel issues, environmental barriers.

Reported as: counts (n) and percentages (%) (number of challenges within one respective category in relation to all registered logistical challenges)

Number of logistical challenges resolved in relation to all challenges recorded within one defined logistical challenge theme.

Reported as: percentage (%) The logistical challenges themes will be arising from qualitative analysis of field notes and staff reports.

Time-to-treatment in the field will be calculated as the elapsed time between the documented thawing time and the documented start time of the first iloprost administration, as recorded in clinical charts/notes. Each case will be classified by logistical challenge status (no challenge vs challenge occurred). For cases with a challenge, resolution status will be recorded as resolved during the study period vs unresolved/persisting, and challenges will also be assigned to a logistical challenge category. Time-to-treatment will be summarized as mean (SD) within each stratum (e.g., none vs resolved vs unresolved, and by category) and compared across strata.

Baseline tissue at risk will be quantified using the Hennepin Frostbite Score at-risk component, documented at initial assessment (before 1st treatment administration). Results will be summarised as score values (mean [SD]).

At 6 and 12 months, the digital salvage rate will be calculated as the proportion of digits at risk that are not amputated, where "digits at risk" and "amputated" are determined using the Hennepin Frostbite Score methodology and follow-up documentation. Results will be reported as n/N and % with 95% confidence intervals, and may be compared with prespecified historical proportions from the literature (one-sample proportion testing as applicable).

Amputation status (any vs none) will be ascertained from clinical charts, operative notes and self reports at six and twelve months after treatment completion. Results will be reported as n (%) with 95% confidence intervals, and may be compared with pre-specified historical rates from the literature if feasible.

At 6 and 12 months after treatment completion, the number of joints salvaged per participant will be determined from the Hennepin Frostbite Score tissue-at-risk mapping and documented final tissue loss/amputation level. Results will be summarized per participant (e.g., mean [SD] and/or distributional summaries) at each timepoint.

Pain intensity will be recorded using the Numeric Rating Scale (NRS) 0-10 as documented in clinical charts/notes at baseline (initial clinical assessment) and self reported at 6 months and 12 months follow-up. The outcome will be change from baseline in NRS score at each follow-up timepoint (follow-up minus baseline). Results will be summarised as mean (SD) at 6 and 12 months (and mean (SD) change), with within-person comparisons over time analysed using paired t-tests.

Upper-extremity function will be assessed using the QuickDASH (11-item self-reported questionnaire about Disabilities of the Arm, Shoulder and Hand (DASH)) at baseline, 6 months, and 12 months. The outcome will be change from baseline in QuickDASH score at each follow-up timepoint (follow-up minus baseline). Results will be summarised as mean (SD) at 6 and 12 months (and mean (SD) change), with within-person comparisons over time analysed using paired t-tests (or pre-specified nonparametric alternatives if assumptions are not met).

This assessment will only be undertaken in patients whit frostbites on the upper extremity.

Foot/ankle function will be assessed using the Foot and Ankle Ability Measure (FAAM) - Activities of Daily Living (ADL) subscale, a self-reported questionnaire, at baseline, 6 months, and 12 months. The outcome will be change from baseline in FAAM-ADL score at each follow-up timepoint. Results will be summarised as mean (SD) at 6 and 12 months (and mean (SD) change), with within-person comparisons analysed using paired t-tests (or pre-specified nonparametric alternatives if assumptions are not met).

This assessment will only be undertaken in patients with frostbites affecting the lower extremities.