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Department of Anaesthesia, Sree Chitra Tirunal Institute for Medical Sciences & Technology, Trivandrum, Kerala, India
To the Editor:
We read with great interest the article by Usichenko et al. (1) reporting the reduction of venipuncture pain by cough trick (CT). Finding a way to reduce the venipuncture pain is important, however, we believe that there were several problems with the study.
There are at least two most important goals to achieve during venous cannulation (VC). First, there should be little or no pain, and second, to achieve success during first attempt, especially at least during when there is only one visible peripheral vein. Although, authors of the present study have shown the effectiveness of their study in reducing the venipuncture pain; they failed to analyze the success or failure of the method they described. The success or failure of a VC largely depends on various factors and includes size and type of cannula and vein chosen, visibility of vein, and movement or steadiness of the arm during VC. It is never easy to cannulate the vein if the arm is not in steady state, and one can understand that keeping the vein in the steady state while patient is coughing is not only difficult but also has the potential to cause injury to patients and/or assistants holding the hand of the patient involved in the procedure. This could happen by "open needle and cannula" if the patient suddenly moves the arm during the procedure while coughing. Furthermore, we also believe that the merits of the study are doubtful under the condition in which there is poor visibility of vein because of any reason (dark skin, cold extremity, "shock state") or in neurosurgical patients when increase in intracranial pressure is a concern. Authors have described the incidence of arm movement with CT, but how they differentiated between the arm withdrawal due to pain or CT we could not fully understand.
Usichenko et al. (1) further reported the tendency of heart rate to decrease during the procedure. Surprisingly, in a volunteer study (2), it was shown that in the absence of arterial hypotension, there was a concomitant increase in supine heart rate and blood pressure and a sustained postcough increase in supine heart rate that, in contrast, is contradictory to the findings of Usichenko et al. (1). Moreover, they failed to mention about the vasovagal reaction, a potential side effect of coughing and venipuncture (3,4) that could have the synergistic effect if performed simultaneously. The authors’ study, we feel, would have been strengthened had they analyzed the risk versus benefit ratio. If we had to choose between either inflicting a minor pain to the patient during VC (which can be easily alleviated by local anesthetic spray or injection) or "loosing" a vein (especially if it is single) because of sudden movement of the arm that could occur while coughing, we would definitely prefer to choose the former. However, we would be little hesitant to insert the IV cannula in a patient who is asked to cough simultaneously during the procedure.
References
Department of Anesthesiology and Intensive Care Medicine, University of Greifswald, Greifswald, Germany
In Response:
We appreciate the interest of Drs. Sinha and Manikandan in our recent study. Their comments concerning the potential application of the cough trick (CT) in clinical practice can be definitely cleared after appropriate clinical trial. The queries about the secondary end points of our study need immediate clarification.
1. Indeed, we did not analyze the success of venipuncture (VP) because this was not the objective of the study. Moreover, the failure of the VP at the first attempt was defined as one of discontinuation criteria.
2. The subjects were trained to cough with moderate intensity without moving their arms before the VP that (a) assured successful procedure and (b) allowed to distinguish the withdrawal reaction (if any) at the moment of VP with CT. All of these have been described, although very briefly, in the Methods section in our article (1).
3. As to the "increased supine heart rate," the moderate single cough should not be expected to produce noticeable chronotropic response. In order to achieve the heart rate changes (usually transitory tachycardia), the routine test procedure is to ask the subject to cough as vigorous as possible and not only once, but three times (2). An exact comparison with the cited paper could not be warranted because we used different methods of measuring heart rate and recorded it at different time points.
4. We did not observe the vasovagal reactions, probably due to the same moderate intensity of cough. As far as the VP itself, which without CT can cause vasovagal reactions with severe complications (3,4), the subjects in our study were punctured in supine position.
We completely agree with Drs. Sinha and Manikandan about the relative clinical contraindications of CT and do not recommend this procedure to junior doctors who have technical problems with VP itself. We presume that there is a large population of patients that have visible veins, do not have increased intracranial pressure, and are not in shock to be included in the study on the clinical success/failure rate of the CT.
References
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