all good points above. to add a little more detail if you're interested (i didn't look up the official codes but for the most part the examples are accurate)
As mentioned above, the hospital gets paid on a DRG, say sepsis. Many DRGs are individual, some are doublets or triplets, which means they have a MCC (major complication or comorbidity, these are diagnoses like acute CHF or respiratory failure or ATN) or CC (blood loss anemia, CKDIII or above). Sepsis is a triplet - so you can have sepsis (low bill), sepsis with blood loss anemia (middle), sepsis with respiratory failure (high). This is why you are getting all these queries to specify if the respiratory failure is acute, hypercapnic, acute on chronic, etc. Loss of specificity can impact losing an MCC and makes your sick af patient look not so bad. this does not impact clinical care but has massive ramifications on the bottom line and quality metrics.
you mentioned these patients are having critical care time billed. CC time may be the cream of the crop in medical billing but it is a rounding error compared to the figures we are talking about in DRGs. Here are some rough figures for sepsis due to finger osteo. expected pay was 15k. payor tried to deny the CC and said appropriate payment was more like 8k. that's a 7k difference over 1 line of text in your note. Also, as mentioned above, the hospital doesn't collect money from your professional fee billing. the caveat being if you are employed they might be recouping a small amount from your RVU. Nota bene, your RVU has 3 compnents - work, malpractice, and practice expense. if you are employed, the hospital is definitely keeping the last 2 and probably skimming a little from the first.
DRGs are also divided into surgical and medical. I believe all surgical DRGs pay higher than all medical DRGs. there is a special category of DRGs called PRE (you can google "major diagnostic category 0" for more info) that override all other DRGs- they include things like transplants and trachs. Traching a pt is the #1 moneymaker that an intensivist can offer the hospital by a long shot. really long. you can take a look at the DRG weights
here. I dont know if there is a more up to date list.
Cases that are very short or long LOS compared to the expected DRG do not get paid by the DRG- they utilize trim points. a short trim point (pt discharged way faster than expected) is a per diem rate, usually the DRG payment divided by the GMLOS (which gives a daily rate that is multipled by the actual patient LOS). Long trim points are the DRG plus some other per diem, either the same daily rate as the short trim point or more likely some other contracted rate. trim points are rare though and usually don't pay as well compared to the DRG rates.
it is rare that uninsured patient's give zero payment. they usually end up getting some sore of federal emergency insurance post discharge and the hospital can recoup payment. the hospital can also write off massive amounts of care that help cushion the blow substantially. this is not to say your health system is flush with cash- 2022 hit many health care systems hard financially. As CMS wants to continue to save money, the reigns will only become tighter.
Readmission are a whole 'nother ball of wax that greatly affects payment
tl;dr: hospital gets a flat fee per patient no matter what happens. Discharge the patient (or trach them) ASAP . your billing has zero to minimal contribution overall.