When changes in pathological pain intensity were studied in relation to changes of the urinary pH, a correlation could be established in the majority of cases. Two opposite kinds of relationship were observed when curves of the variations in pain intensity were compared with those of the urinary pH.

Patients who had experienced pain associated with chronic pathological lesions over prolonged periods of time were instructed to record carefully the relative intensity of their pain at regular intervals, such as every hour.

No analgesics were administered for at least six hours before or during the test period which was continued as long as possible, even for twenty four hours. Patients were instructed to concentrate on a single painful area and to estimate the degree of pain intensity. They were told to consider an average degree of pain during each hour rather than momentary peaks during the observation period or the pain at the moment of recording. The degree was recorded in relative terms of no pain, slight, moderate, severe, very severe and unbearable, or as figures from 0 to 10.

A pain pattern

Fig. 6. A pain pattern is recognized by comparing the concomitant changes present in the curves of pain intensity with those of the urinary pH. The parallel variations of the two curves indicate an alkaline pattern with the pain more intensive when the urine is more alkaline, as seen in a case of carcinoma of the colon with painful abdominal mass.

Urine specimens were obtained each hour immediately after the pain intensity observations were recorded and the pH was determined electro metrically. Two curves—for the hourly variations in pain intensity and for urine pH—were then plotted.

Two distinct types of correlations were found. In the first, the two curves paralleled each other, the pain being more intense when the urine pH was higher, and less severe when the pH was lower. (Figs. 6 and 7) Because the maximal pain of this type of correlation is associated with a change toward alkalinity, this was called an alkaline pattern of pain.

The alkaline pattern of pain

Fig. 7. The alkaline pattern of pain in which the concomitant variations in the curves of pain intensity and urinary pH are parallel, seen in a case of arthritis.

In the second type of correlation, the two curves varied inversely, pain being most marked when the urine was most acid, and least so when the urine was most alkaline. (Figs. 8 and 9) This second type was called acid pattern of pain because of its association with a change toward acidity. Considering the highly subjective nature of pain, the inconsistencies which occur are minor. Fig. 10 shows these curves followed during days.

The correlation between the pain intensity and urine pH curves arc relative rather than absolute. The general level of urine pH apparently depends upon other factors. Consequently, only the fluctuations of the hydrogen ion concentration, rather than the absolute levels, are considered in this relationship to pain.

An acid pain pattern is seen in a case of carcinoma

Fig. 8. An acid pain pattern is seen in a case of carcinoma of the prostate with metastatic bone lesions, in which the concomitant variations of the curves of pain intensity and urinary pH are divergent.

Changes in pain intensity were found to have a similar dualistic correlation with other factors as well as the acid base balance—with potassium content of blood serum, for example. Studies were made to compare the concomitant changes in pain intensity and in potassium content of blood serum. In several cases the acid and alkaline patterns of these pains were determined through the relationship to urinary pH variations. At different moments, especially when the pain was markedly different in intensity, blood was obtained by finger puncture, and collected in glass capillaries. After clotting, the serum was immediately separated and the potassium content measured using a flame photometer. Curves of the values of pain intensity at these moments, established by the method previously mentioned, and of the concomitant K+ content were compared. Figs. 11 and 12 show the two curves in two cases in which, the two pain patterns—acid and alkaline, were primarily recognized. The cases with high serum potassium values and with parallel changes between the two curves—pain intensity and K+ content—were seen to correspond to alkaline pain pattern; the other cases with less serum potassium and opposite variations of the two curves were seen to correspond to the acid pain pattern.

An acid pattern of pain recognized by the divergent variations

Fig. 9. An acid pattern of pain recognized by the divergent variations of the curves of pain intensity and urinary pH is seen in a case of phantom limb.

We extended the study of the pain pattern, as revealed by concomitant variations of pain intensity and body acid base balance, from cancer cases, in which a frank dualism had been seen, to other painful conditions. It was interesting to note that, in many conditions, pain can have one or the other pattern but there are some conditions in which only one pattern is consistendy found. Pain following trauma of any kind—the pain of post operative and accidental wounds, burns and fractures, for example—always has an alkaline pattern. This is also true for the pain of gallbladder colic. In other conditions, either pattern may be present and must be determined by analysis. For instance, the pain of neuritis and simple headache has an acid pattern in some cases, alkaline in others.

variations of the curves of pain intensity and urinary pH

Fig. 10. The pain pattern can be recognized also through the characteristic opposite variations of the curves of pain intensity and urinary pH, followed during successive days—instead of hours—as seen in the above curves of a case of cancer of the rectum. (Courtesy of Dr. Rognoni).

In rheumatoid arthritis, an alkaline pain is almost constantly found. In osteoarthritis, the pain is of an acid type. In arthritic patients in whom this relationship did not seem to hold, it was possible to recognize not only the existence of both rheumatoid and osteoarthritis but also to note that the pain pattern, as shown by test, was related to the more painful condition. We utilized the diagnosis of the type of pain present as an indication of the nature of painful processes. We will see later how this correlation has been confirmed by therapeutic trials.

Pain pattern and potassium in blood serum

Fig. 11. Pain pattern and potassium in blood serum. The comparison of the concomitant changes in the curves of pain intensity and those of the amount of potassium in blood serum shows parallel variations in a case with an alkaline pattern.

Two types of pain associated with two different conditions present in the same individual have been found to occur more frequendy than expected, although usually not simultaneously active.

In most patients with two or more anatomically separated painful foci, parallel variations occurred between the curves of the different pains. Only in occasional cases were the two pains found to vary simultaneously but in opposite fashion. Their opposite patterns were well described by patients who observed "the two pains act as if they were part of a balance; when one goes up, the other goes down, and the opposite." In Figure 13, the pain curve of lesion A is seen to vary inversely with the curve of urinary pH, while the pain curve of lesion B is parallel with the urinary pH curve. Thus, the pain of lesion A is of an acid pattern while that of lesion B is of alkaline pattern.

Divergent variations between pain intensity

Fig. 12. Divergent variations between pain intensity changes and those of the blood serum potassium in a case of acid pain pattern.

Pains

Fig. 13. Pains. Acid and alkaline pains can co exist on different lesions, as seen in a patient with multiple osseous metastases from breast carcinoma. Lesion A, which corresponds to an acid pattern, shows divergent variations between the curve of urinary pH and that of its pain intensity, while for lesion B, with an alkaline pattern, the variations of the curves of pain intensity and of urinary pH are parallel.

Also interesting to note is the persistence of the same pattern for pains associated with chronic conditions. We have headache patients, for example, in whom, during the 20 years since we first determined the pattern of pain, there has been no changes of pattern. In others, on the contrary, changes occur rapidly. In a case of sciatica, we have seen rapid and frequent changes in pattern, especially in response to therapeutic measures.

The changes induced in the pain intensity

Fig. 14. The changes induced in the pain intensity by the administration of an acidifying agent indicate the pattern present. Pain with an acid pattern is intensified following oral administration of 1.5 cc. of a 50% sol. of phosphoric acid. Urinary pH changes reflect the induced systemic acidification.

Worthy of being noted is the correlation found between variations in pain intensity and changes in the acid base balance of the body even in cases in which nerves are directly involved in lesions and in which a mechanical pathogenesis usually has been accepted. This would indicate that the chemical factor mentioned above has a role in the pathogenesis of pain even in these cases.