I just now discovered this thread Deb, and am adding my prayers. My Husband had sepsis (combined with high fever, respiratory distress, kidney failure, basically similar to your Son?) a couple of years ago. Because of his other chronic health problems and the severity of his sepsis, they used a just out of clinical trials drug called Xigris. He survived!
I also learned from a pharmacist friend of mine, God bless her, that the drug they give to people who are on the vent (Versed) builds up in the body and the longer they are on it, the harder it is to get them off of the ventilator.
So, my non-medical opinion is make sure they are not already overdosing him on Versed, and time the attempt to extubate him for when the last dose is about to wear off, as I seem to recall the drug itself can decrease the body's own attempts to breathe. Read the Contraindications and special caution section of this:
http://en.wikipedia.org/wiki/Midazolam ( copied that part to save you time "Additional caution is required in critically ill patients as accumulation of midazolam and its active metabolites may occur.[43] Kidney or liver impairments may slow down the elimination of midazolam leading to prolonged and enhanced effects.") - that is the reason as to why it can build up in the body. In side effects there is this "Sedation,
respiratory depression and due to a reduction in systematic vascular resistance hypotension and an increase in heart rate can occor."
Thanks to a search engine I found a few other things that might be helpful:
http://www.rcjournal.com/contents/02.05/02.05.0275.pdf
http://www.rxmed.com/b.main/b2.phar...aphs/CPS- (General Monographs- V)/VERSED.html
http://psyweb.com/Drughtm/jsp/versed.jsp - see warnings, copied here to save you time "WARNINGS: Serious respiratory adverse events have occurred after administration of oral VERSED, most often when VERSED was used in combination with other central nervous system depressants. These adverse events have included respiratory depression, airway obstruction, oxygen desaturation, apnea, and rarely, respiratory and/or cardiac arrest (see box WARNING). When oral midazolam is administered as the sole agent at recommended doses respiratory depression, airway obstruction, oxygen desaturation, and apnea occur infrequently (see DOSAGE AND ADMINISTRATION)." Even though they are talking about oral administration, it is likely useful with regard to IV also.
If your Son starts showing a lot of agitation, that could be a symptom of what they call 'paradoxical effect', not good.
So....I will hope and pray they can get him off of the Versed and the vent soon. My husband was on the vent for 3 or 4 days, max, and remained in the hospital for 2 more weeks after that.
p.s. here is info on Xigris, which has some serioius possible side effects itself; it is used as a last ditch effort type med if patient is in imminent risk of likely death, and I hope and pray that your Son is not in that category!
http://en.wikipedia.org/wiki/Drotrecogin_alfa
http://www.xigris.com/Pages/index.aspx
