If one envisions circulating chemicals more or less continuously, then a PICC line should be adequate. PICC is an acronym for Peripherally Inserted Central Catheter. They insert a small catheter through a peripheral vein, like one in your upper arm, and guide it through that vein until it reaches a larger vein close to the heart. The procedure requires a degree of medical expertise and a means of following the progress of the catheter while you're inserting it - they use an ultrasound.
This is quite a bit more than what the typical free trader is capable of, unless the unit has such capability built in. It's possible; it's a 100,000 credit machine, there must be something in there for that value. However, the clever player may find other uses for that kind of imaging tech; you may not want that kind of a tool in your player's hands. Alternately, the prospective passenger may need to have the procedure done at a hospital or clinic before reporting for boarding, but that implies additional cost. Still likely to be cheaper than mid passage, but there's nothing in canon about checking in at a clinic before going on a low passage.
A port in a major artery is also no small thing. It likewise implies skilled medical services or a very competent machine. Unless you run with the competent machine idea, you run into the same canon issues the PICC line has: this isn't the kind of thing you do without solid medical training - you basically can't do this without Medical 1 or maybe 2, and failure could hospitalize or kill them before you even launch your ship.
Either the low berth unit has very good independent or semi-independent capability to place these lines, or you're left with using either plain ol' fashioned IVs (which still require a bit of skill) or some sort of inhalation system to get whatever chemicals you want into the passenger's system.
I wore a PICC line for fourteen weeks after surgical incisions got infected with MRSA. Insertion used a small portable ultrasound to track the end of the PICC from its insertion point in my left bicep until it reached the desired position near the heart. Took all of a minute. Smearing my arm and chest with the gel that they use for the ultrasound sensor took longer than inserting the line. Removal didn't even require that; they just pulled it out while I was talking to another nurse and I didn't even know they had started until they were already done.
A competent Registered Nurse can do the procedure, so that's Medic 2. Once the PICC was in, I just had to visit a clinic once a week to have blood samples drawn through the PICC. After the nurse demonstrated the procedure for the first time, I administered the antibiotics, the anticoagulants to keep the PICC from clogging, and the antiseptics to keep the PICC ports sterile all by myself, three times a day. So actual use of the PICC is Medic-0.
Superficial mishap indicates one PICC port is clogged (it has two). Minor mishap indicates both ports are clogged. Major mishap indicate the PICC tube collapses, requiring the entire PICC be removed and replaced with a new one. Destroyed mishap indicates the PICC ruptured a blood vessel, which requires surgery due to internal bleeding. Level of surgery required depends on how close to the heart the rupture occurred.
I would think that for a cold berth (passenger completely frozen) a PICC would not be necessary, only a (large) injection. A chill berth, where the passenger is placed in a cold-induced hibernation (similar to some cold-water drowning cases), a PICC could be used to circulate a biodegradable organic antifreeze to keep ice crystals from forming in the cells— failure of which could be the main source of low berth mishaps, depending on what organ(s) are affected, fatality might be due to localized frostbite of brain, lungs, heart, whatever due to incomplete circulation of the fluid. Lesser mishaps could be due to the same cause, except the organs involved are not necessarily life-threatening (eyes— blind in one eye, larynx/esophagus— laryngitis and trouble swallowing, stomach— ulcer, etc.)
I say biodegradable antifreeze because that's something the kidneys could filter out of the bloodstream once the passenger is awakened. "For the next 24 hours or so, your urine will be kind of a fluorescent yellow, and your vision will have kind of a pink tinge due to the chemical in your blood affecting your retinas. Don't worry about it, that's normal for people who use low berths." (By the way, those specific colors come from the chemicals used for fluourescene angiograms done by my ophthalmologist, though in that case the pink vision only lasts 15 minutes or so.)
Given that Traveller already has increasingly capable medical scanners at various tech levels, there's no reason why a canonical scanner wouldn't be able to monitor the insertion of a PICC without the need of a separate ultrasound machine.
