Scottish Court of Session Decisions

In September 1991, the pursuer and respondent, Mrs. Stewart, was admitted to the Royal Infirmary, Edinburgh. She required a surgical operation. The anaesthetist was a Dr. Armstrong. The defenders and reclaimers are the Health Board having responsibility for the Infirmary, and for the actings of Dr. Armstrong. Dr. Armstrong intended to insert a catheter into Mrs. Stewart's jugular vein, at a point where the vein runs close to the carotid artery. Instead, the catheter punctured the artery. Dr. Armstrong removed the catheter and compressed the artery to stem bleeding. As a result, Mrs. Stewart suffered a period of partial paralysis and certain other residual problems. In this action, Mrs. Stewart avers fault on the part of Dr. Armstrong, and seeks reparation. After proof, the Lord Ordinary held fault to have been established, and found the Board liable in agreed damages of £100,000. The Board reclaim.

Dr. Armstrong adopted what is known as "the Seldinger technique" for catheterization of the jugular vein. That technique involves a number of steps or stages prior to actual catheterization. Putting the matter shortly, the earlier steps are directed towards finding the vein, and confirming that the vessel which one has found is indeed the vein and not the nearby artery; whereas the latter stages, proceeding upon the basis that one has indeed found the vein, are directed to the satisfactory insertion of the catheter into that vein.

Not all of the grounds of fault originally pled were insisted upon in the submissions to the Lord Ordinary. It was still alleged that Dr. Armstrong was at fault in not carrying out procedures of rapid infusion, which would have made catheterization of the jugular vein unnecessary. The Lord Ordinary has not however found that ground of fault to be established; and it is not necessary for us to deal with it further. It was further submitted that Dr. Armstrong had failed in his professional duty, in relation to two tests, included in the Seldinger technique, designed to check that the jugular vein and not the carotid artery had been penetrated.

The later stages of the Seldinger technique (involving insertion of a guide-wire into and down the blood vessel, over which first a dilator, and then the catheter itself are introduced) are of course crucial, in terms of fact and causation: it was the insertion of the catheter itself which punctured the artery, and led to damage. But no failure of duty is said to have occurred in the course of these later stages. The point is that they would not have been embarked upon, and so the injury would not have occurred, but for a failure in carrying out the two immediately prior checks.

For the purposes of this reclaiming motion, matters can be narrowed down still further. What we have called the earlier stages of the Seldinger technique involve the drawing off of a small quantity of blood via a needle into a syringe. The fact that blood can thus be drawn into a syringe confirms that the tip of a needle is in a blood vessel; and the colour of the blood in the syringe is an indication of whether the blood vessel is a vein or an artery. This process is carried out initially with what is called a "seeker" needle. If that provides an indication of venous blood, a larger-gauge needle is inserted on the line of the seeker needle, with blood again being drawn into a syringe, providing confirmation that the tip of this needle is in a blood vessel, and making a further "colour" test possible indicating whether the blood is venous or arterial. In accordance with the technique adopted by Dr. Armstrong, colour-testing in this way is not regarded as sufficient: it is followed up by a further test, described as a "flow test". Before the Lord Ordinary, fault was alleged in relation to both the colour test and the flow test. The Lord Ordinary has not held fault to be established in relation to the colour test, and counsel for Mrs. Stewart did not ask us to reverse his decision in that respect. The stage of events at which the Lord Ordinary has held fault to be established is the carrying out of the flow test. The issue in this reclaiming motion is accordingly limited to that finding, and fault at that stage.

When the larger needle has been inserted, and blood aspirated into the syringe attached to that needle, then if that blood satisfies the colour test, the original seeker needle and its syringe are taken away. Aspiration and a satisfactory colour test having been achieved, the syringe attached to the larger needle is no longer required. However, the needle itself has to be kept in place. It is through this needle that the guide-wire is introduced, and indeed the needle is referred to as the "guide-wire needle". Before the guide-wire can be inserted into the needle, the syringe must be removed. And removal of the syringe is the next step after the colour test has been satisfied. It is at this stage, prior to the guide-wire being inserted, that the flow test can be carried out. With the removal of the syringe, the proximal end of the needle is exposed and, provided that the aperture at the tip of the needle is still within the blood vessel, blood can pass from that blood vessel through the bore of the needle and out at the aperture at the proximal end, which is now free of the syringe. The flow test consists of an observation of the blood coming out through the needle, when the syringe is removed. Unlike venous blood, blood in the arteries is pumped by the heart, so that the flow is pulsatile; and blood in the arteries is at a much higher pressure than blood in the veins. We shall come to the other suggested possibilities; but if the aperture at the tip of the needle is fully in an artery, and unobstructed, the blood emerging from the needle can be expected to spurt out in such a way as to reveal the arterial characteristics of pressure and pulsatility. It is perhaps worth noting that the flow test, like the colour test, is a test by observation alone: no other steps are taken, or techniques applied. Nor is it suggested that the observation involves any kind of prolonged or detailed scrutiny. The word "check" might be more suitable than the word "test" as a description of both the colour test and the flow test, since all that happens is that the anaesthetist looks at blood on each occasion, to see whether its appearance is arterial or venous. If the anaesthetist regards the blood emerging from the needle in the flow test as venous, he will proceed to insert the guide-wire. Dr. Armstrong did so.

As we have observed, the Lord Ordinary's finding of fault relates to this specific stage of the procedure - the flow test. While he made that finding, he does not say, at least in so many words, whether as a matter of fact he is holding that the blood which came from the needle spurted out under pressure and was pulsatile as it could be expected to be if the aperture at the tip of the needle was in the artery and unobstructed; nor does he say in so many words whether he is holding, as a matter of fact, that the aperture at the tip of the needle was thus in the artery and unobstructed. Moreover, while a finding that there was spurting pulsatile blood which Dr. Armstrong somehow failed to take into account before proceeding to insert the guide-wire would evidently provide a basis for a finding of fault on his part, Dr. Armstrong's evidence was directly to the contrary. As the Lord Ordinary narrates, "He explained that the blood emerging from the guide needle had 'dribbled' out. It had no pulse". It is not suggested that the two accounts can be reconciled; and if, as counsel for the pursuer contended, the Lord Ordinary is to be read, by implication, as finding that blood spurted out in a pulsatile manner, he must be rejecting Dr. Armstrong's account. The Lord Ordinary does not say that he considers Dr. Armstrong to have been lying in this respect; nor does he discuss how, if the blood was as obviously arterial as this factual account suggests, Dr. Armstrong might fail to recognise it as such, or how he could then give the account which he gave in evidence. Furthermore, in presenting their respective submissions to us, counsel for the parties were at odds as to what the Lord Ordinary had concluded as a matter of fact. While counsel for the pursuer contended that the Lord Ordinary had implied that there was what one may call an obvious or typical arterial flow, counsel for the Board read the Lord Ordinary as having come to the conclusion that Dr. Armstrong's negligence consisted in his not having had sufficient data for the flow test, in order to justify proceeding to the next stage - a conclusion for which it was submitted there was no adequate basis in the evidence. In asking us to recall the Lord Ordinary's interlocutor, counsel for the Board contended that the Lord Ordinary had also erred in a number of other major respects. We shall return to these. But while the primary contention advanced on behalf of the pursuer was to the effect that there was no basis for reviewing the Lord Ordinary's decision and the facts upon which it was based, this argument understandably expanded into a contention that if for any reason this court felt obliged to review the Lord Ordinary's decision, then the matter being open to us, we ourselves should hold that the evidence established negligence on the part of Dr. Armstrong in conducting the flow test, on the basis which counsel for the pursuer attributed to the Lord Ordinary.

An appellate court will of course always be slow to interfere with a decision on fact made by the judge who heard the evidence. In suggesting that we should not do so, junior counsel for the pursuer naturally referred us to the well-known passage in the speech of Lord Thankerton, in Thomas v. Thomas 1947 S.C. (H.L.) 45 at page 54. He further referred us to Clarke v. Edinburgh and District Tramways Company 1919 SC (HL) 35. He submitted that this was not a case in which the Lord Ordinary's reasoning was unsatisfactory, nor a case in which the evidence did not support the decision, and that it was indeed a case where the Lord Ordinary had made a "simple determination of a plain question of fact" - a phrase drawn from the speech of Lord Buckmaster in Clarke at page 36. On the other hand, senior counsel for the pursuer acknowledged that there was a difficulty in the way in which the Lord Ordinary had formulated his Opinion. However one may describe the decision reached by the Lord Ordinary in this case, we are satisfied that it was not a simple determination of a plain question of fact of the kind envisaged by Lord Buckmaster. And while much that the Lord Ordinary says is directed to an analysis of the evidence, and to reasoning based thereon, we have come to the view not only that his factual conclusions are insufficiently identified, but in particular that his opinion contains no sufficient explanatory reasoning, leading to a conclusion either that Dr. Armstrong's factual account of what he saw was false and that there was a typical arterial emission of blood or that there was an emission of blood so meagre that it could be described as providing insufficient data for Dr. Armstrong to reach any conclusion on the flow test. That being so, we are satisfied that the Lord Ordinary's decision on fault, and whatever decision on fact underlies it, cannot be allowed to stand. That being so in these respects, the matter becomes one for us; and we have thought it more useful to refer to the Lord Ordinary's other and more detailed observations in the context of our own consideration of the matter, rather than in the context of the primary attack upon, and defence of, the Lord Ordinary's Opinion.

The only direct evidence as to the nature and appearance of the flow of blood from the needle came from Dr. Armstrong himself. There is no suggestion from the Lord Ordinary, nor was it submitted by counsel for the pursuer, that this evidence could be rejected as incredible or unreliable upon the basis of Dr. Armstrong's own evidence alone, or of the way in which he gave it. Equally, if his factual evidence that the blood dribbled and had no pulse is not rejected, there is no other witness who can speak directly as to the sufficiency for test purposes of what he saw. Furthermore, there is no other witness who can speak directly as to how Dr. Armstrong acted, or what he did, between removing the syringe and introducing the guide-wire to the needle. In these circumstances, the opinion evidence of experts (including Dr. Armstrong himself) had to form the basis of the pursuer's case not only on the question of whether Dr. Armstrong was negligent in established circumstances, but also as the only means of rebutting Dr. Armstrong's evidence as to what those circumstances were (by demonstrating that on a balance of probabilities what he described could not have occurred). Moreover expert evidence would afford the only means of establishing, again on a balance of probabilities, a version (or alternative versions) of events which "must" have occurred, in which (or in each of which) it could be said that the exercise of reasonable skill and care would have led a competent anaesthetist such as Dr. Armstrong not to embark upon and carry through the further steps ending in catheterization itself. At proof therefore, the Lord Ordinary heard opinion evidence from experts on such matters as whether, with the tip of the needle in the carotid artery, the emission of blood at the stage of the flow test could have an appearance other than that of spurting in a pulsatile manner; if so, what appearance, or range of appearances, the emission might have; whether these might be as described by Dr. Armstrong; what the causes might be for the emission not being a pulsatile spurt; and in relation to the various hypothetical possibilities, whether negligence must or need not be inferred. In relation to these various issues, questions of likelihood or probability of cause arose for the Lord Ordinary, and arise now for us. And these in turn involve questions as to whether the statistical improbability, or rarity, of a potential cause for blood from the artery being emitted from the needle in the way described by Dr. Armstrong provides a sufficient basis for rejecting his evidence, holding that the facts must have been otherwise, and holding further that those facts, or alternative versions of fact, must (or must each) as a matter of probability have involved negligence on his part.

Apart from Dr. Armstrong, expert evidence was given by Dr. A.B.M. Telfer, formerly a consultant anaesthetist at Glasgow Royal Infirmary, and Professor Allan Aitkenhead of the University Hospital, Nottingham. The pursuer's case depends essentially upon the evidence of Professor Aitkenhead, for the primary proposition, that contrary to Dr. Armstrong's evidence there must have been an unimpeded arterial flow from the needle. The alternative proposition, that the flow must have provided insufficient data to justify further procedure, derives from elements in the evidence of both Professor Aitkenhead and Dr. Telfer. In relation to the Lord Ordinary's Opinion, counsel for the pursuer submitted that he had accepted the former proposition, while counsel for the defenders submitted that he had accepted (without a proper justification in the evidence) the latter proposition. At all events, the Lord Ordinary appears to have proceeded upon the basis that one or other of these propositions had been established. If that were indeed the appropriate conclusion upon the evidence, Dr. Armstrong's evidence would have to be rejected, and it might not be necessary to make a choice between the two propositions, which ex hypothesi would be the only possibilities, and each of which would entail fault, since in either event it would have been negligent to proceed further. For the pursuer, it was submitted not merely that that had been the Lord Ordinary's conclusion, but that it should be ours. For the defenders, it was submitted that while Professor Aitkenhead had at one stage apparently propounded the view that these were the only possibilities, he had in fact accepted (and the Lord Ordinary had failed to appreciate that he had accepted) that these were not the only possibilities, and that a flow such as Dr. Armstrong described might occur. That was in any event the proper conclusion on the evidence of all the expert witnesses, taken as a whole.

Against that background, and turning to the evidence, what is to be observed at the outset is that the central issue relates to the possible position or positions of the aperture at the tip of the needle, not only when the flow test occurred, but shortly before and after that specific stage, when blood was aspirated into the syringe, and when the guide-wire was introduced through the needle into the artery itself. While the needle and its internal bore, in section, are round, towards its tip its cylindrical form is bevelled across its full diameter, producing an aperture which in the plane of the bevelled surface is not circular, but in lay terms oval, and with the bevel producing, to one side of the needle, a sharp tip. It is moreover to be noted that this asymmetrical tip would normally enter the wall of the artery not at right angles to the line of the artery, but at an angle to that line.

Plainly, on a needle being inserted through the skin, it might stop without entering any significant blood vessel, so that there would quite simply be no question of aspirating blood into the syringe, of blood being emitted from the needle on removal of the syringe or of the guide-wire being introduced through the needle into a blood vessel. Equally, at the other extreme, if the whole of the aperture at the tip of the needle lay at all times fully within the lumen of the artery, with nothing to prevent or limit the arterial blood passing through the aperture into the needle, blood could be aspirated, it would be emitted with arterial characteristics if the syringe were removed, and a guide-wire introduced into the needle could pass down it and through the aperture into the lumen of the artery.

The crucial questions for the witnesses, the Lord Ordinary and now ourselves relate to the middle ground, if any, between these extremes. And these crucial questions turn substantially upon quite specific questions as to whether, and if so how, the flow of arterial blood into the needle, and its pressure at the outer end of the needle, might be reduced, and its pulsatility at the outer end of the needle affected, because of the aperture being at least partially obstructed as a result of the aperture being only partly in the lumen, and partly in the wall of the artery. Moreover, that question itself is in some measure complicated by a set of further questions. Even if at the time of the flow test it is possible for the blood emitted to lack arterial pressure and pulsatility, can that happen (as a result of movement of the needle or otherwise) in cases where, as here, blood was satisfactorily aspirated immediately before the syringe was removed and emission of blood from the needle occurred, or where (again as in this case) immediately after the flow test a guide-wire is successfully passed not merely down the length of the needle, but on from the needle down the lumen of the artery? Would not the hypothetical obstruction of the aperture at the tip of the needle, assuming that it could reduce the pressure and pulsatility of the arterial blood to a degree where the appearance would be of venous blood emerging from the needle, also prevent satisfactory aspiration some moments before, and satisfactory passing of the guide-wire from the needle into the lumen some moments after the flow test itself? And if these earlier and later stages were achieved successfully, does that indicate that the flow of blood out of the needle, at the intervening stage of the flow test, would be unobstructed and plainly arterial?

Leaving aside for the moment any implications which might be drawn from the aspiration of blood into the syringe, or from the passing of the guide-wire, the possibility of partial obstruction of the aperture at the time of the flow test was considered in some detail in the course of the evidence. Professor Aitkenhead expressed the belief that the force and pressure through this size of needle would have been obvious if it had been observed correctly - so obvious that one would not need to refer to the evidence of anyone who was there and purported to have seen what was going on. Professor Aitkenhead had previously described the "free flow" of blood when the tip of the needle lies correctly in the lumen, and said that through needles of this size, he could not envisage a situation, between free flow and no flow, where there was simply a sluggish flow. However, he acknowledged that the position of the needle could affect the flow of blood from the artery into the needle (although he described this as theoretical, since, if that was the case, no blood could have been aspirated into the syringe). He said that if there were a diminished flow, the most likely reason would be because the needle was only partly in the vessel, either the tip just entering, or because it was beginning to go out through the back wall. While he emphasised that these conditions would also affect the ability to aspirate blood, and would not affect the colour of the blood, he accepted the possibility of interference with flow, depending on the exact position of the tip of the needle, going on to say that this "would be a contra indication to inserting the guide-wire" and almost certainly would mean the guide-wire would not enter the vessel. Early in his evidence, however, explaining that this was quite a large needle, so that blood flowed freely out of the end, Professor Aitkenhead distinguished the situation where the needle lies in a vein and "it's dark blood and it sort of trickles out" from the situation of arterial blood which is bright red and "spurts out in a pulsatile fashion". That being the generally accepted position when there is an unobstructed flow, it is not perhaps clear how a flow from an artery, if diminished to a trickle because of the exact position of the tip of the needle "would be a contra indication to inserting the guide-wire". Unless there was some separate contra indication, due to colour or pulsatility, a trickle similar to that expected from a vein would apparently be an indication that one could proceed. But overall, Professor Aitkenhead's view is evidently that such a trickle would not emerge in the flow test if there had been satisfactory aspiration beforehand, and, if it occurred, would "almost certainly" not be followed by successful insertion of the guide-wire into the vessel.

For Dr. Armstrong, explaining how an artery could produce the flow which he saw was not of course a primary question: his evidence as to what he saw is not an inference from a theoretical causal explanation. This is perhaps worth emphasising, since counsel for the pursuer, in discussing the possibility of obstruction as an explanation for what Dr. Armstrong saw, treated that possibility as "Dr. Armstrong's hypothesis"; and indeed the Lord Ordinary says that Dr. Armstrong "speculated" on the range of possibilities which might have accounted for the combination of a low and non-pulsatile blood flow from the guide needle and free access for the guide-wire. The essential position of Dr. Armstrong in evidence is that he was able to aspirate into the syringe, did see a non-pulsatile dribble of blood and was able to insert the guide-wire. It is important to bear that evidence in mind: it will not fall to be rejected simply because one might not see it as satisfactorily explained. So far as explanations are concerned, Dr. Armstrong, like Professor Aitkenhead, saw a diminution of flow as explicable if the aperture were partly obstructed in the artery wall. Unlike Professor Aitkenhead, Dr. Armstrong did not see that as inconsistent with successful prior aspiration or successful subsequent insertion of the guide-wire. With the help of a sketch, illustrating various possible positions of the needle and aperture, he distinguished the "ideal" position, with the aperture fully in the lumen (so that "you would see that by blood spurting out, and it may spurt out anything from three inches to three feet"), from various positions where you are not in the ideal position "but you can aspirate blood". Moreover, in relation to various positions where the aperture is not fully in the lumen, Dr. Armstrong's evidence was that you "decrease the size of the bore where it goes into the artery and therefore blood can only flow back through that narrow orifice much more slowly and you won't get a spurting effect. Blood will eventually dribble back". In relation to another position, Dr. Armstrong said that again enough of the bevel was inside the artery to be able to aspirate blood, "but the actual hole of the bore is vastly reduced so blood can't pour back, it can only trickle past that obstruction, past the small hole and then up the bore of the guide-wire needle". According to Dr. Armstrong, one could use the argument for these positions all over the area of the artery.

In addition to situations where you could successfully aspirate with the aperture partially occluded, Dr. Armstrong gave evidence that "when you take the syringe off it's very difficult to maintain the needle in exactly the same position it was, and it's very common for the needle to...move a millimetre or even two millimetres...". That being so "you are initially able to aspirate blood but blood does not gush back, it trickles back". Dr. Armstrong also gave evidence as to insertion of the guide-wire, in situations where, at the stage of the flow test, the hypothesis is that the tip of the needle is in a position where the aperture is partially obstructed. Speaking generally, he said that he never used excess pressure in putting in the guide-wire: if he was requiring a bit of extra pressure to push in, he would stop and start the procedure again completely. However, the needle could move inside the artery: it could be in one position, and by the very act of introducing the guide-wire, the needle could be pushed into the ideal position, without one knowing. In other situations, there could be a flap caused by the needle cutting through the vessel wall, which could obstruct movement into the needle, but would be pushed aside by the guide-wire going the other way. On being asked whether it was possible to have a situation where one did not get a spurt of blood, but could get the guide-wire into the artery without undue pressure, Dr. Armstrong said that it was a frequent occurrence. He explained that when performing deliberate arterial puncture, in other arterial vessels, "what we encounter quite often is we think we are in the artery but the flow characteristics aren't correct for an artery but we believe we must be in the artery, and what we do then is assume that something like that has occurred, and put down a guide-wire...". Being partially in the artery can thus explain not having characteristic arterial blood flow, but getting the guide-wire in.

Leaving aside the question of frequency, and specific questions as to pulsatility to which we will come, it appears to us that Dr. Armstrong provides an explanation as to how, on occasion, a needle which is in fact inserted into the artery might allow aspiration, produce a trickle comparable to venous flow and permit insertion of the guide-wire in some circumstances without movement of the needle between one step and the next, and in other circumstances with a slight movement, which, though unintended, could understandably occur. Assuming no movement at all, Professor Aitkenhead's evidence does not appear to us to negate the possibility of all three steps being achieved in the way explained by Dr. Armstrong; nor does his evidence appear to us to negate the possibility of slight movement between stages, making a diminished flow at the flow test compatible with unobstructed aspiration and insertion of the guide-wire. Indeed, so far as movement is concerned, Professor Aitkenhead himself points out that there is movement, not of the needle but of the artery wall, between diastolic and asystolic positions. While such movement would negate the needle tip simply resting against the inside of the artery wall, at least in certain locations, it also appears to provide a possibility of alterations in the extent to which the aperture is or is not obstructed.

Dr. Armstrong's account of what he saw was of course not merely that the flow was a dribble, but also that there was no pulse. It is perhaps a matter of language, or of degree: perhaps the words "dribble" and "trickle" inherently imply a non-pulsative flow. Since Professor Aitkenhead did not really envisage any diminished flow, after successful aspiration and before successful insertion of the guide-wire, his evidence does not go into the detailed question of whether a flow which was so diminished as to be consistent with a venous flow in volume, might nonetheless show a degree of pulsatility, which should perhaps be seen and would reveal that the flow was indeed from an artery. But while the position of counsel for the pursuer was primarily that of Professor Aitkenhead - that the flow must have been a full and obvious arterial one - the submission appeared at times to be widened, so as to embrace the factual possibility that there had been a diminished flow as described by Dr. Armstrong, but that it must nonetheless have been observably pulsatile. Even if it were established that a flow diminished by a degree of obstruction would still retain a pulsatile character, and even if it were established that a "trickle" or "dribble", comparable with a venous trickle or dribble, would nonetheless, even if coming from an artery, always have some pulsatile element, it would not follow that this pulsatile element would in all circumstances be identified by an ordinarily competent anaesthetist exercising a reasonable degree of care and skill. Nor does there appear to be evidence that this would be the case. But given Dr. Armstrong's explicit evidence that there was no pulse, and the overall need to assess his reliability and credibility, it is plainly appropriate to give specific consideration to this matter, and in particular to the evidence of Dr. Telfer, on whom, in this respect, counsel for the pursuer particularly relied.

The Lord Ordinary describes Dr. Telfer as a careful and balanced witness. It is however to be noted that in connection with the issue of pulsatility, the Lord Ordinary says that it appeared to him that "when he was not prompted" Dr. Telfer inclined to the view that if one had a flow of arterial blood it would possess the characteristics of arterial blood. And noting that questioning in re-examination had produced some qualification of opinions expressed in cross-examination, the Lord Ordinary says that it was when Dr. Telfer was "speaking for himself" that he found the evidence most persuasive. Not having had the Lord Ordinary's advantage of actually hearing Dr. Telfer's evidence, we think it right for us to note and apply the distinction which he draws, and to have regard to what Dr. Telfer says when speaking for himself, rather than when any answers appear perhaps to have "gone along with" an element of suggestion in the question.

At an early stage, in examination-in-chief, Dr. Telfer said that he thought that "If you have a proper unobstructed connection in the middle of it, presumably that flow will also be pulsatile" but added that it would depend on the bore, diameter, size, of the connection into the vessel, how pulsatile. He is therefore apparently speaking for himself in introducing the hypothesis of a "proper unobstructed" connection in the middle of the artery as the situation in which the flow will presumably be pulsatile. And on that hypothesis of an unobstructed needle, he shares the view of others, that it would not be possible to mistake the flow for venous blood. "If it is unobstructed you will get a pattern". He goes on to describe the non-pulsatile venous flow, trickling in a steady form. And on being asked what might account for arterial blood trickling rather than spurting from the needle, he raises the possibility of a partially obstructed needle and "not getting the full flow pattern": "I think these are the reasons why you can get this obstructed or partially obstructed flow, which will not show the pattern".

After further questioning by the court, in reply to a question about pulsatility at the point of inspection, Dr. Telfer said "I would say it would be damped. I don't want you to think the pulse would completely disappear". But faced with the hypothesis that in this case the needle was partly in the wall and partly in the lumen, he is asked whether it is possible in his view for the flow of blood out of the needle, once the syringe was removed, to be such as could be mistaken for venous blood. His reply is "Yes, there is if this particular scenario is correct, yes". Similarly, but perhaps more specifically, in re-examination, counsel redirects Dr. Telfer's attention to the question of recognition of pulsatility. On the hypothesis that the tip of the needle is partially obstructed, but is sufficiently in the artery in order to aspirate blood and for blood to dribble from the needle when the syringe is removed, Dr. Telfer is asked whether, if the blood was coming out in a sort of dribble, it must be obvious to an ordinary competent anaesthetist exercising a degree of skill and care that there is such pulsatility there. The answer is "No".

That is no doubt the kind of answer which the Lord Ordinary sees as having been prompted in some measure; and it is evident from the court's own questions at the time that the Lord Ordinary had in mind the possibility that if the blood flow fell so low that there was no observable pulsatility, it might perhaps have fallen so low that there was no sufficient flow for the test to be useable. There are certainly points in Dr. Telfer's evidence where he appears to express (or go along with?) this approach, envisaging that if one was not really happy one would withdraw and begin again. But while he says that "most times there would be some degree of pulsation", he goes on to observe that "whether you see it and realise that is what it was, that is an individual observation". And when it is put to him in cross-examination by counsel for the pursuer that he is saying that he would expect there to be a detectable pulse in the arterial blood coming out of the needle, and that that test is always available, his reply is "I would have to say that I just know in practice it is not as simple as that. I understand that sounds nice". He is there plainly "speaking for himself". And it does not appear to us that his evidence is to the effect that with diminution due to partial obstruction, the only situation in which there will not be a detectable pulse is one where there is so little blood that the competent anaesthetist would recognise it as too little for the purposes of the test. When it was put to him (by the court) that there could be a situation in which the flow from an artery was so low that any pulsatile character was eliminated, and the court asked him how low the blood flow must be in that situation and whether it would be comparable at that level with a normal flow from a venous source, Dr. Telfer said "I think there is a sort of level and it may well be compatible with the venous source". Again, he appears to be "speaking for himself" and it appears to us that in his view, pulsatility may have disappeared, and yet the flow may be compatible with a venous source.

Since one is checking whether the needle is in a vein, and the colour test has allowed one to proceed to this stage, we do not see how it could be a counter indication to further steps that one has found a non-pulsatile and apparently venous flow. The Lord Ordinary says that when Dr. Telfer was speaking for himself, the impression he left was that if there was a flow from an artery it would have pulsatile character, albeit there "might be some" dampening of the pulse where there was partial obstruction. Dr. Telfer does not so express matters. It appears that Dr. Telfer could envisage a point at the end of the spectrum, where there was so little flow, that one would withdraw and start again. But he sees it as a spectrum, and within that spectrum, no doubt towards its lower end, it seems plain to us that Dr. Telfer envisages situations in which there is the limited flow consistent with presence in a vein, and pulsatility being dampened to such a degree as not to be evident to an anaesthetist exercising reasonable care.

If a flow such as Dr. Armstrong described can occur, notwithstanding that the needle is in the artery rather than the vein, it is not easy to see why his evidence that it did occur should be rejected, even if such an occurrence can be described as unexpected or rare or unlikely. If such an occurrence were not relatively unexpected or rare or unlikely, then at some point on the gamut of frequency the flow test would no doubt be discarded as of no practical use. But it is important to note that while the colour test and flow test are relied upon, as a practical basis for proceeding to full catheterization, there was a body of evidence indicating that these tests are not regarded as reliable in any absolute or fool-proof sense. Dr. Telfer said they were not very reliable tests, that an inadvertent catheterization could result, and that this was a recognised complication. He said that he thought about 4% was a fair average for an inadvertent carotid puncture, describing it as probably the commonest complication of the attempted cannulation. Dr. Armstrong also said that the tests were recognised to be not reliable. If they were positive, they were definitely reliable but "quite often they will give you a negative result in that you think they are in the right place but the result is wrong". Both he and Dr. Telfer referred to papers published on the subject, and two of these were gone into in some detail in evidence. While it was submitted to us that these papers were essentially related to a special group (and while it is accepted that Mrs. Stewart was not suffering from such low blood pressure that that could account for a misleading flow test) we are quite unable to read either the papers in question or the evidence as a whole as establishing that the tests can be expected to be absolutely reliable for patients comparable to Mrs. Stewart. And particularly in the light of the evidence of obstruction, as a possible cause of misleading flow tests, we see no reason to doubt Dr. Telfer's evidence on this matter. It is no doubt perturbing that on occasion the results are misleading. As the papers show, the profession is dissatisfied that the success rate is not even higher. We are not persuaded that these tests are fool-proof, with arterial blood always appearing either as obviously arterial, or as a flow so meagre that it could not be construed as coming from a vein.

In our opinion the evidence other than Dr. Armstrong's direct evidence of what he saw shows that what he describes would not occur very often, but could well occur on occasion. He gives a clear and circumstantial account of it having occurred on this occasion. Both the general evidence and his particular evidence lead us to reject the suggestion that there must have been either a full arterial flow, or too little for any inference to be drawn. In terms of fault, we find it difficult to imagine how he would have proceeded, had there been a full arterial flow, since ignoring such a flow would entail the most crass negligence, and apparently subsequent perjury. We accept Dr. Armstrong's factual account, and reject the allegations of fault. We allow the reclaiming motion, recall the Lord Ordinary's interlocutor of 2 April 1997, sustain the defenders' second and third pleas-in-law and repel the pursuer's pleas.