Foley's catheter is a self retaining balloon catheter for constant drainage of the urinary bladder. There is a main channel, which drains the urine from the bladder. There is a side channel, which communicates with the balloon near the tip of the catheter. When it is in the bladder, it is inflated with sterile normal saline so that the catheter remains in the bladder. One uses sterile saline, so that if the balloon bursts accidentally, its contents will not contaminate the bladder and cause infection. Have a look at my 3D model of the catheter as shown below, before I tell you the story.
I was teaching the undergrads the technique of using a Foley's catheter. I taught them the theory, showed them a video, and then asked them to go see a catheter being passed in a patient preoperatively.. One of them had a difficulty.
"Sir, why use sterile normal saline?"
"What would you like to use instead?" I asked.
"Tap water" he said. "It is freely available, cheap and abundant."
"Won't the woman get cystitis if the balloon bursts and the unsterile water enters the bladder?" a girl from the same batch of students asked him before I could say anything. She seemed to be good at her studies and/or her thinking.
"That is right" I said. "Some people use any fluid anywhere. That can harm patients. I remember one of our professors using milk for checking tubal patency in place of methylene blue. Unfortunately the milk was not sterile evaporated milk, as is the recommendation. It was milk sold by the government's dairy. When I asked him about whether it could cause infection, he said, "No. It is sterile. It is pasteurized." It was sad that he did not know pasteurized milk was free of tubercle bacilli, but not of pathogens that can cause surgical infections. I don't know what happened to that patient, nor do I know what is happening to his patients where is practicing his art now."
They were suitably impressed.
"If we want to save some money by not using 5-10 ml of sterile normal saline" I said, "why not use the patient's urine? We could collect it after passing the catheter, and inject it into the balloon. Since it is the patient's own urine, it will not harm her even if the balloon bursts."
They laughed. No one gave the right answer to that question. Just then a senior consultant in the unit walked by, and said, "shall we put methylene blue solution into the woman's bladder? Then we will know immediately if the bladder gets opened."
I looked at the students, who caught on and laughed.
"Better not" I said. "A filled bladder is more likely to get injured than an empty one. Let us be more cautious during our surgery instead, and let us use methylene blue only if we suspect a bladder injury."
We completed the operation under discussion as usual without opening the bladder and there was no occasion to use any methylene blue solution or milk, and definitely not tap water.
"Sir, why use sterile normal saline?"
"What would you like to use instead?" I asked.
"Tap water" he said. "It is freely available, cheap and abundant."
"Won't the woman get cystitis if the balloon bursts and the unsterile water enters the bladder?" a girl from the same batch of students asked him before I could say anything. She seemed to be good at her studies and/or her thinking.
"That is right" I said. "Some people use any fluid anywhere. That can harm patients. I remember one of our professors using milk for checking tubal patency in place of methylene blue. Unfortunately the milk was not sterile evaporated milk, as is the recommendation. It was milk sold by the government's dairy. When I asked him about whether it could cause infection, he said, "No. It is sterile. It is pasteurized." It was sad that he did not know pasteurized milk was free of tubercle bacilli, but not of pathogens that can cause surgical infections. I don't know what happened to that patient, nor do I know what is happening to his patients where is practicing his art now."
They were suitably impressed.
"If we want to save some money by not using 5-10 ml of sterile normal saline" I said, "why not use the patient's urine? We could collect it after passing the catheter, and inject it into the balloon. Since it is the patient's own urine, it will not harm her even if the balloon bursts."
They laughed. No one gave the right answer to that question. Just then a senior consultant in the unit walked by, and said, "shall we put methylene blue solution into the woman's bladder? Then we will know immediately if the bladder gets opened."
I looked at the students, who caught on and laughed.
"Better not" I said. "A filled bladder is more likely to get injured than an empty one. Let us be more cautious during our surgery instead, and let us use methylene blue only if we suspect a bladder injury."
We completed the operation under discussion as usual without opening the bladder and there was no occasion to use any methylene blue solution or milk, and definitely not tap water.
