As Christmas 2020 approaches it is time to reflect on the impact that coextensive volume and pressure mapping (CoEVPM) has had on the practice of medicine in such a relatively short time. The idea was first patented as long ago as 2001, but only brought to the attention of fluidphysiology.org in 2016. Let’s take some recent case examples of the benefits of CoEVPM in this auspicious year of 2020…
Mr J was extricated from a motor vehicle accident looking pale, his pulse thin and rapid. The paramedic strapped a CoEVPM cuff on his arm, and got the following reading; p115, ABP 82/ 40, eCVP 4. Confident that Mr J was bleeding rather than tensioning, she just inserted an intravenous cannula for restrictive volume resuscitation and blue lighted Mr J to the E.D. On arrival a doctor did a trauma POCUS and excluded pneumothorax.
Ms K came to A&E with a tense tender abdomen and a rapid heart rate. CoEVPM on arrival revealed p 122, ABP 85/35 and eCVP 5. After balanced saline and antibiotics her CoEVPM improved to p 115, ABP 97/45, eCVP 7. In Critical Care they used the critical care CoEVPM monitor which revealed a lot more information about Ms K’s peripheral vascular circuit. For instance, they noted that her average venous elastance was only 5 (normal >100). Ms K was admitted to Surgical High Dependency Unit after emergency laparotomy, and continued to receive balanced saline at about 200 ml/h. CoEVPM p. 97, ABP 98/55, eCVP 9. Average venous elastance was not much changed at 9. In critical care we are particularly careful to keep the mean capillary pressure as low as possible during fluid resuscitation in order to avoid transient transendothelial hyper-filtration which causes avoidable oedema, and this we achieved with a little norepinephrine infusion. The Boss is a great believer in the Guytonian notion of a mean cardiac filling pressure which is independent of cardiac output; most experts these days reckon that in most cases the venule to small vein inflection pressure represents MCFP, and so that is our target pressure for fluid resuscitation here on Middleton ICU. Me, I’d be happy to target eCVP, but that is an ongoing and probably unresolvable controversy. By the third day Ms K was looking greatly improved with p. 89, ABP 105/70, eCVP 13. The Boss was happy with her MCFP, but there were some other signs that her circulation had not yet fully stabilised. Ms K’s total sensed volume was unsurprisingly high, and we planned to reduce it by a period of deresuscitation therapy. But her pulsed volume and average venous elastance remained worryingly low, so we were cautious not to precipitate another drop in her cardiac output. The students like to be shown vascular compliance stack graphics on teaching ward rounds to help them understand the new physiology, but I think most of them just conclude that a career in Orthopaedics would be far simpler and more lucrative.
Anaesthetists everywhere are using CoEVPM to unravel the mysteries of circulatory changes during general and regional anaesthesias. The Journals seem to carry no other research. All of a sudden the brightest and the best students want to become Anaesthetists. And the new vocation of peri-operative medicine has a new favourite toy.
They tell me the biggest impact for the NHS has been from the availability of CoEVPM in every GP Surgery. Over-65s get their CoEVPM performed (instead of the old-fashioned blood pressure measurement) at every opportunity, and this has allowed for earlier identification of normal-ejection fraction heart failure with renal insufficiency. Fewer people attending A&E and fewer patients needing dialysis has to be a good thing.
Anyway, 2020 has been a year to remember on many fronts; U.K. became Europe’s strongest economy for the first time since the Battle of Waterloo, but who would have guessed that after Donald Trump’s first term as POTUS Americans would vote for Abstract truncated at Word Count Limit.