Material Event (Form 8-K)

Item 8.01 Other Events

As previously disclosed, on August 20, 2024, SeaStar Medical Holding Corporation, (the "Company"), entered into an At the Market Offering Agreement (the "ATM Agreement") with H.C. Wainwright & Co., LLC (the "Agent"), as sales agent, pursuant to which the Company may offer and sell shares of the Company's common stock, par value $0.0001 per share (the "Shares"), from time to time in an at-the-market public offering. On July 10, 2025, the Company determined to suspend sales under the ATM Agreement and terminated the continuous offering of the initial aggregate offering price of $25,000,000. As of August 8, 2025, the Company had sold an aggregate of $6.8 million in shares of its common stock under the ATM Agreement.

The Company has determined to resume sales under the ATM Agreement, up to an aggregate offering price of $2,166,305. The Shares sold under the ATM Agreement will be offered and sold pursuant to the Company's shelf registration statement on Form S-3 (Registration No. 333-275968), which was initially filed with the Securities and Exchange Commission (the "SEC") on December 8, 2023 and declared effective on December 22, 2023, and a prospectus supplement and the accompanying prospectus relating to the at-the-market offering filed with the SEC on August 8, 2025.

Because there is no minimum offering amount required pursuant to the ATM Agreement, the total number of Shares to be sold under the ATM agreement, if any, and proceeds to the Company, if any, are not determinable at this time. The Company expects to use any net proceeds for general corporate purposes, which may include additions to working capital and capital expenditures.

The Company retains broad discretion over the use of the net proceeds and reserves the right to use these proceeds for different purposes or uses which have not been listed above. Until the Company uses the net proceeds, it intends to invest the funds in investment grade, interest-bearing securities or hold such proceeds in deposit accounts.

A copy of the opinion of the Company's counsel relating to the validity of the Shares that may be sold pursuant to the ATM Agreement is filed herewith as Exhibit 5.1.

This Current Report on Form 8-K, including the exhibits filed herewith, shall not constitute an offer to sell or the solicitation of an offer to buy the Shares that may be sold pursuant to the ATM Agreement, nor shall there be any offer, solicitation or sale of the Shares in any state or country in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such state or country.