Riassunto del corso di Sistemi di Supporto alla Vita

P D

ERITONEAL IALYSIS

This is another technique and it is based on a more physiologic principle even though it is not the

best situation. Normally, the patients that are on peritoneal dialysis, after some time, are switched

to hemodialysis.

Actually, peritoneal dialysis was born before dialysis because this didn’t require any artificial filter

or any artificial membrane. Peritoneal dialysis started around the beginning of the 20s, then it was

abandoned and then it came back at the end of 70s.

We use the peritoneum membrane as the dialysate (filtering) membrane. It is a membrane present

in our abdomen and it is highly perfused. Therefore, a huge amount of blood and very large

exchange surface is available in the peritoneum. The idea is to fill the peritoneum cavity with a

dialysate fluid, leave it there for some hours and then we scavenge it out.

It is not so nice for the patient but he can do whatever he wants: he can move, go to work, drive,

and so on. The problem is that we will have to go out with some liters of water inside. 96

A dialysate solution is made to stay inside the peritoneal cavity and by contact some mass exchange

takes place between blood and the dialysate. Also ultrafiltration can take place: not so huge

ultrafiltration but a sufficient one if we add with glucose the dialysis fluid. We increase the osmotic

capacity of the dialysate fluid to make it able to take masses out from blood.

The problem is that the patient has to wear a catheter in the abdomen: the fluid is sent inside, the

tube is clamped and closed. Then, the tube is connected again to a waste reservoir and by gravity

eliminates all this fluid. Then, again, some other amount of liquid is put inside the cavity, resides

there for 4÷6 hours, depending on the necessities, and then it is again wash out. The problem is that

there are some cross-contaminations because we eliminate catabolites that come back into the

patient because they are stuck on the tube: when the clean dialysate fluid is administered to the

patient, it will be already polluted so the dialysis will be a little impaired. There is a big problem of

infection because the patient is ambulant and so he can acquire any kind of infection disease.

Moreover, the over-solicitation of the peritoneal membrane can cause peritonitis that can cause

death. Infections, inflammations are all negative effects affecting the patient. Then, patients cannot

be put any longer on peritoneal dialysis and have to be switched on hemodialysis.

The pros of this kind of technique are that we can perform the therapy at home many times during

the day, the patient is free to move and so he is not compelled to stay for hours in the hospital. It is

more in favor of a home-dialysis treatment.

There are different possibilities:

 CAPD is continuous ambulatory peritoneal dialysis, where ambulatory refers to the fact that

the patient can move

 IPD is intermittent peritoneal dialysis: we fill in the cavity, then we leave it some time after

which we empty the cavity and then we fill it again

We can also have different modalities of this: we can have a bag, which is attached to the

belt, and continuously fills the abdomen until it is emptied. We might also have another bag

and a small pump, so we could empty the abdomen. This would be a sort of a continuous

process. 97

 CCPD is cyclic continuous peritoneal dialysis

This is the most modern system, in which we have two bags. We can have a nocturnal dialysis

so it is provided with a huge number of sensors, is save and very controlled. We have a small

machine, two plastic bags that are weighted so we have a sort of piston pump. We move the

pistons to create the flow rate of dialysate that enters the abdomen. Then we make it to

reside for a little time and then we make the other bag to fill by releasing the compression.

We go on in giving and taking out liquids cyclically. In this way, we can administer dialysis

during the night for 8 hours and so during the day the patient will be absolutely free from

the dialysis machine. The machine is also equipped with sensors and in case the

disconnection of tubes takes place. The machine must be very safe and must put the patient

in the condition to make the correct connections. The different bags have different ports,

inlet and outlet ports. The tubings have different connections to be connected to these ports

so that the patient, even if is elderly or ill, cannot make any mistake in connecting the tubings

of the abdomen to the machine.

In the most modern, the patient has two ports on the abdomen and so inserts the tubing

into the port, like it is done for oncologic treatment when people are prepared to undergo a

therapy cyclically without being hurt too much.

There are no or very low problems related to hypertension or hypotension because the continuous

performance of this therapy doesn’t allow the liquid to be too much inside the patient. It resembles

somehow the normal diuresis because the patient undergoes dialysis more or less every day or

many times in the same day.

These patients have metabolic dysfunction due to the glucose added in the dialysis fluid to enhance

ultrafiltration and so they tend to gain weight because some diffusion of the glucose takes place.

After a while, the peritoneum loses its capacity to filter because after some inflammations all the

cellular structures of the membrane change, so patients are turned to hemodialysis.

Hemodialysis therapy is more used to treat kidney distress. We use peritoneal dialysis for the

elderly, people with some vasculature problems (they cannot accept the presence of the fistula),

people that can’t go to the hospital.

The life of people undergoing dialysis is very bad. They also acquire side pathologies.

Hemodialysis and hemodiafiltration use a lot of water: standard hemodialysis uses 180 l of water

per session, while hemodiafiltration uses 370 l of water per session. It’s huge quantity and this

makes these therapies unavailable in those regions where pollution of water is present, where poor

or no water is present, where war is present, where earthquakes are present. Therefore, these

quantities of water must be reduced. Moreover, low water consumption could permit to perform

hemodialysis at home.

Finally, personalization of the treatment is needed. 98

Lez. 11 – 5.06.2015

Respiration Assistance: Lung Support

Lung support can be applied by acting on the air (gas) side or on the blood side. In the gas side the

connection is with a so-called ventilator. The ventilator is a device connected to the patient though

tubings and the access of this machine to the patient is made through the endotracheal tube

(through the mouth or by performing a tracheostomy: the endotracheal tube is inserted inside the

trachea in the frontal part of the neck). In this situation, when the patient is connected to the

endotracheal tube by tracheostomy, most of the times the patients are anesthetized.

There are also some other conditions where the patients are assisted by a tracheostomic approach:

those attaining to the patients that underwent very severe neural disease, i.e. the patients that lose

any neural control because they break the first discs of the vertebral column. Therefore, the spinal

cord is broken in the immediate vicinity of the cerebellum and so the patients become tetraplegic.

They can’t perform any movement (neither active nor passive movements), comprised the

respiratory movement. They have to be assisted by a machine. This kind of machine, for normal

people, consists in the maintenance of the patient connected to the machine and, substantially,

incapable to do anything. Patients must stay in bed so they are moved to specialized centers. Only

rich people can be assisted by movable machines because they are very expensive.

One of the options, instead of performing tracheostomy, is to use the so-called iron lung (polmone

d’acciaio). It is a negative pressure machine. It is a large cylinder in which the patient is placed lying

on a bed. Then everything is closed and only the head emerges. Normally, these patients are able

to move only their eyes and, if they are lucky, their mouth (they can’t speak). Inside the machine,

negative pressure and positive pressure are activated. While the negative pressure is applied, the

atmosphere inside the cylinder becomes negative. So the chest of the patient is compelled to

expand (the vacuum is created). Then, when we switch to the positive pressure, the patient is put

under pressure and so the chest recoils. In this way, it is possible to oxygenate blood and to live.

Obviously, the life of these kind of patients does not exist. It depends also on the age the trauma

happens. If you are young, you can maybe learn new strategies.

We need to ventilate patients for many reasons:

 During anesthesia: the patient can’t breath so we need to ventilate the patient during the

surgery. This is not true for the central period of cardiac surgery because when the patient

undergoes cardiac surgery he is assisted by ECC and there we have the oxygenator. However,

in the transient period, before ECC is set and after it’s removed, but before the awakening

of the patient, he has to be ventilated. Moreover, after cardiac surgery the patient can’t

breath spontaneously for different reasons so he needs to be assisted by respiratory point

of view. Some of these reasons are:

o The heart has been treated but, even if it’s healed, it may have strange working

modalities.

o After ECC patients can acquire many side effects: pulmonary edema (liquid

accumulation in the blood) and impairment in the distribution of flow rates and of

peripheral oxygenation. 99

o The patient may have a psychological problem that is the fear to breath. After the

ECC you have a very long scar on your chest because you have undergone a median

sternotomy so all the stern has been cut, and the chest has been opened and then

closed with metallic clamps. After few days the stern is completely closed. The

patients fear to reopen the chest (the wounds or the sternum) by breathing. This

doesn’t happen. He tends to breath with short breaths, but their efficiency in terms

of oxygenation is very low. Therefore, blood is not sufficiently oxygenated and so the

patient needs to be assisted.

o The patient may need to have a prolonged anesthesia after cardiac surgery for any

reason so, until he is anesthetized, he can’t breathe spontaneously.

 In case of very heavy acute respiratory distress syndrome.

 In case of pneumonia or other kind of pathologies that may charge the patient from the

respiratory point of view.

This kind of ventilation can be applied to neonates and babies, too. Neonates may need it also

because they may have inhaled some meconium during labor and during birth. Meconium is a waste

product produced by the fetus in the amniotic fluid. In the amniotic liquid the fetus cannot breathe

adding oxygen to blood: the mother oxygenates his blood thanks to the placenta, which is produced

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after the 12 week and grows together with the fetus. The fetus is connect