Does anemia cause high venous co2?

Most likely no...: Although this is a complex issue where several factors contribute. Co2 generation is a function of aerobic metabolism and decarboxylation of tca cycle intermediates. Significant anemia reduces o2 delivery to tissues and increases reliance on anaerobic metabolism --> tissue acidosis. A metabolic acidosis leads to respiratory compensation (which lowers blood co2). Whole books written about this.