This work aimed to assess the effect of regional climatic differences on postoperative bleeding in Egyptian patients undergoing cardiac surgery with cardiopulmonary bypass, by comparing outcomes between patients from hot climate zones (Upper Egypt) and those from moderate climate zones (Lower Egypt).

Egypt experiences extremely high ambient temperatures, especially during the summer months, with daily highs frequently exceeding 40°C. Such climatic extremes can influence physiological homeostasis in surgical patients by altering fluid balance, cardiovascular strain, and hemostatic function.

Seasonal and climatic variations have been linked to changes in cardiovascular surgical outcomes, including mortality, length of stay, and complication rates. Several large observational studies have noted increased bleeding or transfusion requirements in surgeries performed under certain environmental conditions, though findings remain inconsistent.

Inclusion Criteria:

• Age ≥18 years.
• Both sexes.
• Egyptian nationality.
• Underwent open-heart surgery with cardiopulmonary bypass.
• Complete medical records and postoperative bleeding data are available.

Exclusion Criteria:

• Emergency surgeries
• Pre-existing coagulopathy
• Use of anticoagulants not discontinued prior to surgery
• Re-do surgeries

This retrospective observational study involved 400 Egyptian patients, comprising both sexes, aged≥ 18 years, underwent open-heart surgery with cardiopulmonary bypass. This research took place over a two-year period between June 2023 and June 2025, following approval from the ethical committee of Al-Azhar University Hospitals.

The data will be available upon a reasonable request from the corresponding author after the end of study for one year.

After the end of study for one year.

The data will be available upon a reasonable request from the corresponding author.