Ischemic priapism as a model of exhausted metabolism

Abstract

In vivo metabolic studies typically concern complex open systems. However, a closed system allows better assessment of the metabolic limits. Ischemic priapism (IP) constitutes a special model of the compartment syndrome that allows direct sampling from a relatively large blood compartment formed by the corpora cavernosa (CC). The purpose of our study was to measure metabolic changes and the accumulation of end products within the CC during IP. Blood gas and biochemical analyses of aspirates of the CC were analyzed over an 8-year period. Mean ± SD pH, pCO₂ , pO₂ , O₂ -saturation, lactate, and glucose of the aspirated blood were determined with a point-of-care analyzer. Forty-seven initial samples from 21 patients had a pH of 6.91 ± 0.16, pCO₂ of 15.3 ± 4.4 kPa, pO₂ of 2.4 ± 2.0 kPa, and an O₂ -saturation of 19 ± 24% indicating severe hypoxia with severe combined respiratory and metabolic acidosis. Glucose and lactate levels were 1.1 ± 1.5 and 14.6 ± 4.8 mmol/L, respectively. pH and pCO₂ were inversely correlated (R² = 0.86; P < 0.001), glucose and O₂ -saturation were positively correlated (R² = 0.83; P < 0.001), and glucose and lactate were inversely correlated (R² = 0.72; P < 0.001). The positive correlation of CO₂ and lactate (R² = 0.69; P < 0.001) was similar to that observed in vitro, when blood was titrated with lactic acid. The observed combined acidosis underscores that IP behaves as a closed system where severe hypoxia and glycopenia coexist, indicating that virtually all energy reserves have been consumed.

Keywords: Corpus cavernosum; glycopenia; lactic acidosis; priapism; respiratory acidosis.

Figure 1

Plot of blood gas analyses of priapism samples on a nomogram for systemic arterial blood gasses. Adapted from (Ichihara et al. 1984).

Figure 2

Various relations between metabolic parameters; (A) inverse linear relationship between pH and pCO₂; (B) inverse linear relationship between pH and lactate; (C) comparison of in vitro and in vivo relationships between pCO₂ and lactate. The slope in vivo is higher, indicating that there is residual oxidative metabolism with additional production of CO₂; (D) inverse relationship between pCO₂ and O₂‐saturation; (E) inverse relationship between lactate concentration and glucose concentration indicating production of lactate with consumption of glucose; (F) relationship between glucose concentration and O₂‐saturation indicating simultaneous glucose and oxygen consumption.