SeaStar Medical Holding Corp

This proxy statement (the “Proxy Statement”) is furnished in connection with the solicitation by the Board of Directors (the “Board”) of SeaStar Medical Holding Corporation (the “Company”) of proxies to be voted at our Special Meeting of Stockholders to be held on Thursday, December 18, 2025 (the “Special Meeting”), at 10 am MST, and at any continuation, postponement, or adjournment of the Special Meeting. The Special Meeting will be held virtually via live webcast. You will be able to attend the Special Meeting online by visitingwww.proxypush.com/ICU. You will be able to vote your shares electronically and submit your written questions prior to and during the meeting through the online website.

Holders of record of our common stock, par value $0.0001 per share (the “Common Stock”), as of the close of business on November 3, 2025 (the “Record Date”), will be entitled to notice of and to vote at the Special Meeting and at any continuation, postponement, or adjournment of the Special Meeting. As of the Record Date, there were 35,865,834 shares of Common Stock outstanding and entitled to vote at the Special Meeting. Each share of Common Stock is entitled to one vote on any matter presented to stockholders at the Special Meeting.

The Company will begin mailing, or otherwise make available to stockholders, instructions on how to access the proxy materials and how to vote to stockholders on or about November 14, 2025. In this Proxy Statement, “Company”, “we”, “us”, and “our” refer to SeaStar Medical Holding Corporation.

Proposals

At the Special Meeting, you will be asked:

• To approve an amendment to our Third Amended and Restated Certificate of Incorporation (the “Certificate of Incorporation”) to effect a reverse stock split of our Common Stock at a ratio of 1-for-10 (the “Reverse Stock Split”), without reducing the authorized number of shares of the Common Stock, to be effected in the sole discretion of the Board at any time within one year of the date of the Special Meeting without further approval or authorization of stockholders (the “Reverse Stock Split Proposal”);

• To approve an amendment to our Certificate of Incorporation to reduce the number of authorized shares of common stock by 25,000,000 to 425,000,000 shares (the “Authorized Share Proposal”); and

• To approve a proposal to adjourn or postpone the Special Meeting to a later date or dates, if necessary, to permit further solicitation and vote of proxies if there are insufficient votes for, or otherwise in connection with, the approval of the Reverse Stock Split Proposal or the Authorized Share Proposal (the “Adjournment Proposal”).

We know of no other business that will be presented at the Special Meeting. If any other matter properly comes before the stockholders for a vote at the Special Meeting, however, the proxy holders named on the Company’s proxy card will vote your shares in accordance with their best judgment.

Recommendations of the Board

The Board recommends that you vote your shares as indicated below. If you return a properly completed proxy card, or vote your shares by telephone or Internet, your shares of Common Stock will be voted on your behalf as you direct. If not otherwise specified, the shares of Common Stock represented by the proxies will be voted, and the Board recommends that you vote:

• FOR the Reverse Stock Split Proposal;

• FOR the Authorized Share Proposal; and

• FORthe Adjournment Proposal

If any other matter properly comes before the stockholders for a vote at the Special Meeting, the proxy holders named on the Company’s proxy card will vote your shares in accordance with their best judgment.

Information About This Proxy Statement

Why you received this Proxy Statement. You are viewing or have received these proxy materials because our Board is soliciting your proxy to vote your shares at the Special Meeting. This Proxy Statement includes information that we are required to provide to you under the rules of the Securities and Exchange Commission (“SEC”) and that is designed to assist you in voting your shares.

Printed Copies of Our Proxy Materials. You have received or will receive printed copies of our proxy materials, and instructions regarding how you can vote are contained on the proxy card included in the materials.

Householding. The SEC’s rules permit us to deliver a single set of proxy materials to one address shared by two or more of our stockholders. This delivery method is referred to as “householding” and can result in significant cost savings. To take advantage of this opportunity, we have delivered only one set of proxy materials to multiple stockholders who share an address, unless we received contrary instructions from the impacted stockholders prior to the mailing date. We agree to deliver promptly, upon written or oral request, a separate copy of the proxy materials, as requested, to any stockholder at the shared address to which a single copy of those documents was delivered. If you prefer to receive separate copies of the proxy materials, contact Continental Stock Transfer and Trust Company at 1-800-509-5586 or in writing at Continental Stock Transfer and Trust, 1 State Street 30 th Floor, New York, NY 10004-1561.

If you are currently a stockholder sharing an address with another stockholder and wish to receive only one copy of future proxy materials for your household, please contact Continental Stock Transfer and Trust Company at 1-800-509-5586 or in writing at Continental Stock Transfer and Trust, 1 State Street 30 th Floor, New York, NY 10004-1561.