(1) Characteristics of Fine Pulse The fine pulse is characterized by a pulse body that resembles silk, with a pulse vessel that is thinner than a normal pulse. When palpated, the pulse feels small and delicate, somewhat akin to the second string of a violin. Through years of clinical practice, I believe that fine pulse and thin pulse are merely different names for the same pulse type. Clinically, a standard fine pulse should be thread-like. (2) Mechanism of Formation and Diagnostic Significance of Fine Pulse 1. Blood Deficiency (or Blood Loss) The primary mechanism for the formation of fine pulse is blood deficiency. A fine pulse is one of the main pulse types used to diagnose blood deficiency in clinical practice. If a fine pulse is detected, we can further inquire whether the patient experiences symptoms such as dizziness, palpitations, limb numbness, or dizziness upon standing. If these symptoms are present, a diagnosis of blood deficiency can be confirmed. Various causes leading to insufficient or deficient blood, including acute and chronic bleeding, result in a reduced volume of blood flowing through the vessels, thus forming a fine pulse. 2. Yin Deficiency Chronic consumptive diseases or patients with a constitution of Yin deficiency may exhibit a fine pulse due to insufficient Yin blood filling the vessels; or due to vomiting, diarrhea, or excessive sweating (caused by illness or mismanagement), significant damage to Yin fluids can lead to acute Yin blood deficiency, resulting in a fine pulse. 3. Severe Yang Deficiency Although it is relatively rare for a fine pulse to occur due to Yang deficiency, severe Yang deficiency can indeed lead to a fine pulse. For example, in the “Treatise on Febrile Diseases” (Shang Han Lun) 280, it states: “In the case of Shaoyin disease, the pulse is fine and weak, and the patient only desires to sleep.” This fine pulse primarily arises because Qi is the commander of blood; severe Yang deficiency, particularly of Heart Yang and Kidney Yang, results in insufficient Yang energy to propel blood through the vessels, leading to a fine pulse due to inadequate Qi and blood filling the pulse pathways. 4. Simultaneous Retreat of Zheng and Xie, Indicating Improvement The above three points have been elaborated upon in ancient TCM texts and modern textbooks, and we will not elaborate further. Below, we will focus on the fourth mechanism for the formation of fine pulse: the simultaneous retreat of Zheng (correct Qi) and Xie (pathogenic factors), indicating improvement in the condition. Zhang Zhongjing states, “On the third day of febrile disease, if the Shaoyang pulse is small, it indicates recovery” (Shang Han Lun 270). Why does a “small Shaoyang pulse” indicate recovery? By the third day of the febrile disease, the condition has progressed to the Shaoyang stage, and upon palpation, the pulse is found to be small, which is a fine pulse. What does this fine pulse indicate? Zhang Zhongjing believes that this means the illness is nearing resolution. Why? Because the pathogenic Qi has weakened, and Zheng and Xie are no longer in conflict; the patient’s pulse is not rapid, not taut, and not large, but small. This indicates that both Zheng and Xie have retreated from the battlefield; the pathogenic factors have retreated because they are nearly eradicated, and the correct Qi has retreated because there is no longer a need for conflict. The simultaneous retreat of Zheng and Xie leading to a fine pulse is similar to the mechanism observed after a “battle sweat” (zhanzhan), where experienced clinicians have observed a typical battle sweat: during hot weather, a patient receiving intravenous fluids may feel cold and shiver, followed by a temperature reading of 40 degrees Celsius. Western medicine may interpret this as a reaction to the infusion, and some may require antipyretics, but the patient soon breaks into a profuse sweat, and the high fever subsides. This is what we refer to as a battle sweat, where cold shivering occurs alongside fever, or the patient feels “immediately feverish”; during the cold shivering, they do not feel hot, but when the high fever occurs, they then feel the heat. This can also be described as an immediate fever followed by a profuse sweat, and subsequently, both the cold shivering and high fever resolve. In our historical medical texts, this is referred to as “battle sweat resolution.” What is the mechanism of battle sweat? It is the struggle between Zheng and Xie, where Zheng prevails over Xie, especially when the cold pathogenic factor retreats, leading to a profuse sweat and self-resolution of the illness. During the process of temperature reduction after battle sweat, the most common pulse manifestation is a relatively weak pulse, with the second most common being a fine pulse; both are referred to as “pulse quiet, body cool.” A quiet pulse indicates that the pulse is neither rapid nor forceful, and the pulse is fine and weak. In the later stages of illness, a fine and weak pulse often appears, indicating that the patient’s correct Qi is deficient, and Zheng and Xie have simultaneously retreated. If a fine and weak pulse is observed after a severe illness, it reflects a deficiency of correct Qi, and appropriate tonifying herbs may be used. However, if the fine and weak pulse arises from a sudden illness with battle sweat resolution, this indicates the simultaneous retreat of Zheng and Xie, and we should avoid medication, allowing for ample rest and consumption of light foods such as rice porridge. At this time, it is crucial not to use warming tonics; otherwise, within a few days, the patient may develop a fever again, as described by Ye Tianshi, “Though the stove smoke has extinguished, there is still fire in the ashes,” indicating a resurgence of latent heat. Of course, there are indeed many cases of high fever or even delirium due to infusion reactions, which should be diagnosed through a combination of medical history, clinical manifestations, and the medications used. If it is an infusion reaction, the infusion should be immediately stopped, and various methods from both TCM and Western medicine should be employed to reduce fever and counteract allergies to prevent complications. During my years as a rural physician, I encountered two patients with temperatures that reached the maximum; one case was due to an infusion reaction, resulting in high fever and delirium, which was successfully treated through a combination of TCM and Western medicine. “On the third day of febrile disease, if the Shaoyang pulse is small,” Zhang Zhongjing’s statement indicates that the pulse has predictive value. If a fine pulse is detected in a patient with Shaoyang disease, it can be reliably predicted that the fever will subside today or at the latest tomorrow, and this prediction is quite reliable, as the pulse often appears before other symptoms. However, the premise is that we have diagnosed the febrile disease as being in the Shaoyang stage, or Shaoyang’s stagnant fire, and upon palpation, the pulse is fine, but the patient’s usual pulse is not fine. In this case, the fine pulse is indeed conclusive evidence of the simultaneous retreat of Zheng and Xie, indicating that the condition is improving. We can inform the patient that they are recovering, and this is unlikely to be incorrect. Therefore, the predictive nature of the pulse is one aspect of the importance of pulse diagnosis. (3) Differential Diagnostic Significance of Fine Pulse 1. If the primary issue is heart blood deficiency, the pulse may also present as a left cun pulse that is uniquely deep; if liver blood deficiency is predominant, it may present with a fine string-like pulse. 2. If liver and kidney Yin deficiency is predominant, the pulse may also present as a weak deep pulse; if heart and lung Yin deficiency is predominant, it may present as a deep pulse at the cun position. 3. In cases of severe Yang deficiency, the pulse may also present as a weak pulse, and in severe cases, it may present as a fine pulse. 4. In cases of simultaneous retreat of Zheng and Xie, indicating improvement, the pulse often presents as fine, soft, and gentle. The fine pulse that appears during the simultaneous retreat of Zheng and Xie, indicating improvement, differs somewhat from the fine pulse produced by the previous three mechanisms; it comes on softly and gently, with a calm and unhurried quality, and may even feel somewhat weak.
