The Effect of PVC Packaging on the Acidity of 0.9% Saline

Abstract

Intravenous fluids in polyvinyl chloride (PVC) packaging are known to be acidic. We proposed to determine the effect of PVC packaging on the pH of 0.9% saline solutions by comparing the predicted and measured pH of 0.9% saline equilibrated with atmospheric carbon dioxide and the measured pH of commercial solutions of 0.9% saline in PVC and polypropylene packaging. Calculation of pH was made from available physical chemistry constants and data. Measurement was made of the pH of 12 samples of prepared 0.9% saline equilibrated with atmospheric carbon dioxide. Comparison with the pH of seven commercial samples of saline in PVC packaging for intravenous use was undertaken. Further comparison was made between commercial samples of 0.9% saline in PVC or polypropylene packaging. The calculated pH of 0.9% saline was 5.61 at 20°C. The median pH of the prepared samples was statistically significantly less acidic than the median pH of the PVC packaged samples for intravenous use: 5.47 vs 4.60, P<0.05. The median pH of the PVC packaged saline was also statistically significantly more acidic than the pH of the polypropylene packaged saline: 4.62 vs 5.71, P<0.05. The acidity of the intravenous solutions of 0.9% saline packaged in PVC was much greater than expected and is only partially explained by dissolved carbon dioxide. This acidity could be a result of packaging in PVC.

The influence of the irrigating solution on articular cartilage in arthroscopic surgery: A systematic review

“…Normal saline (0.9%) has an average pH of 5 and potentially as low as 4.6. 31 Ringer's lactate has an average pH of 6.5, with similar electrolytes as plasma. 32 Maroudas also described the electrolyte activity of articular cartilage as similar to that of Ringer's solution.…”

“…42 Increased osmolarity leading to chondroprotective effects is a conclusion that most of the included studies agreed with. 25,[28][29][30][31] Previous studies have also demonstrated that after mechanical injury to the articular cartilage, a decrease in extracellular osmolarity resulted in more extensive chondrocyte death compared with a higher osmolarity. 43,44 One study found that during drilling, chondrocyte death was significantly reduced by raising osmolarity and reducing Ca2+ content.…”

Why Is Saline So Acidic (and Does It Really Matter?)

“…Studies comparing (i) the theoretical pH of saline derived using the principles outlined above, (ii) the pH of saline prepared in the laboratory in the absence of PVC, and (iii) clinical grade saline from a widely used commercial source packaged in PVC based material revealed that whilst prepared samples had a very similar pH to that predicted (median 5.47), the median pH of the PVC packaged saline was 4.6. Interestingly, the pH of saline in polypropylene packaging was 5.71, suggesting a particular property of PVC to be culpable 1. Of interest, concerns that constituents and degradation products of PVC/DEHP packaging might have endocrine disrupting effects have meant that polyethylene and polypropylene containers for intravenous solutions are increasingly favoured in their stead10.…”

“…In fact it is quite acidic: pH being reported as low as 4.6 1. Why does this simple solution have a pH so far removed from the physiology it is designed to support?…”

Association of Hyperchloremia With Hospital Mortality in Critically Ill Septic Patients

“…0.9% saline is in reality a non-neutral solution (12) and has a supraphysiologic amount of chloride when compared to plasma (154 vs ~100 mEq/L, respectively) (13, 14). The consequent hyperchloremic metabolic acidosis derived from the liberal use of chloride-rich solutions has been described as a common but poorly recognized disorder in critically ill patients (15, 16), with numerous detrimental consequences (17, 18), particularly in those with severe sepsis and septic shock (19).…”