Unfortunately this is a complex issue and cannot be resolved simply by reading Acts 15:29, and then extrapolating from that one text an injunction against blood transfusions. There are issues of exegesis that become involved, and this leads to interpretation which itself has to include various problems of context. For instance, who were being addressed by the abstinence order of this verse? All Christians? No. The letter that was to be circulated among the various Christian congregations of that time only referred to Gentile Christians. Thus whatever Acts 15:29 means it applied at a certain moment in time, to a certain section of Christians that existed at that time.
The problems of exegesis are therefore contextually interwoven around several subtext issues which thus makes interpreting this section of Acts intensely difficult. There are various points of delineation that need to be addressed:
1 What does "apecho" translated as "abstain" mean? Is it purely a dietary term involving the ingesting of fluids into the body? The fact that it is used with "idolatry" and "fornication" shows that it has a range of meanings extending to conditions beyond the human digestive system. For this reason several mainline conservative scholars believe that "abstaining from blood" takes in, not only the need to refrain from taking into the body but to avoid any contact with blood whatever. Thus abstaining from blood can, using "abstaining from idolatry" as a locus, mean also "abstaining from spilling blood.
2 How many prohibitions are listed in vs 29? Three? or Four? The Watchtower has always assumed that it was four: Idolatry, blood, strangled meat, and fornication. But this ignores the use of the Greek "kai" which Freddy Franz, Watchtower wunderkind, translated as "and". Lets digress a moment, and look at this little word:
How many groups are sighted as being in heaven in Rev 20:4? Two, if you take "kai" to mean "and" as in:1 Those who sat on thrones [acc to Wt theology= 144000] AND 2 Those who were Great Tribulation martyrs. In order for Franz to make only one group appear in heaven this is how he manipulated the word "kai": "Those who sat on thrones, YES, the great Tribulation martyrs.
Now lets look at Acts 15:29, paying attention to how we can apply "kai", 1 idolatry and 2 blood, yes, strangled animals 3 fornication. We can see from this that the the list of prohibitions may actually have been three, not four. This is in fact favoured by a majority of interpreters. [See Bible Knowledge Commentary - pg 395] If this is the case then the prohibition against blood is purely a dietary issue, referring back to Gen 9, where blood should be drained from an animal before eating, and has nothing to do with medical ethics and practice.
3 Were these prohibitions to be permanent? According to the Watchtower they were. But others are not so sure.
Again remember that these prohibitions were legislated when an issue occurred in the Primitive Church: a threatened split in the Church caused by the two divisions of Jewish and Gentile Christians. As long as that division persisted, the letter sent out to Gentile Christians asking THEM [not the Jewish section] to observe 15:29 would be in force. [See vs 19, where Freddy referred to the addressees as "those of the nations" Most intelligible translations read: "Those among the Gentiles" NASB]
By the 21st century, when this division is no longer prevalent, the issue addressing that division is correspondingly irrelevant.
By the time the Bible canon was completed, and distributed, especially the Pauline corpus which was written some thirty years and more after this event, True Christians would have a complete record of God's will on the subject. Especially relevant would be Rom 14. Where Acts 15:29 was a blanket prohibition for Gentile believers, now Paul reveals that a measure of conscience becomes involved, and Christians, whatever their ethnic background, should learn to flex their theological sinews in making their own decisions.
Also curiously enough, Acts 15 was relevant at a time when such things as "prophets" as a unique sub group were still current in the Church [Acts 15:32] When this office would pass away as the Watchtower insists that it would, the relevance of this part of the Bible would be in its historical content, not prohibitive analysis.
Thus Acts 15 is by no means so inflexible a construct that it requires only one authorized and censured version of interpretation. Christians have long discovered something that the arrogant strangers to God's word who fraudulently pose as God's exclusive spokesmen in the Watchtower, have not. And this is to tolerate and accept various possible permutations of evidence, all of which are based on sound biblical exegesis.
Back then we can see the loving reaction of the two groups within Christianity. The decision made at the Jerusalem involved doctrinal and practical matters. Jewish Christians agreed doctrinally to drop the need for circumcision, and the Gentiles agreed to adopt certain moral and dietary codes that they previously had had. The principle today is the same. We must accept differing opinions, knowing that no one or no group possesses absolute truth.
We must all struggle with biblical revelation, and whether such things as blood transfusions have any connection, no matter how tenuous with Acts 15 becomes moot, not inscribed in stone. Most intelligent Christians would consider it foolish to hang so much, including a possible danger to ones life or ones loved, on a circumstance that involves interpretation of a complex Bible passage..