- How the Holmium Laser works
- Use for Urological surgical interventions
- Comparing surgical techniques
How the Laser works
Holmium Laser Features
The Holmium Laser has reached an important role in applications to urological diseases, mainly due to its unique features. It is a versatile tool that can fragment all types of stones and has the ability to cut, coagulate and remove soft tissue. These characteristics make it particularly useful for surgical applications, especially for endoscopic surgery because the laser is transmitted through silicon dioxide fibres (thin and flexible).
The Holmium Laser is a pulsating laser using photovaporization. It produces very high temperatures at the cellular level (above 100°C) causing water vaporization and thus tissue vaporization.
There are several models of the Holmium Laser designed according to their applications. Each is classified according to the maximum power developed. The laser which deals with all possible applications is the Holmium Laser VersaPulse ® PowerSuiteTM 100 W and has the following characteristics: the energy per pulse is between 0.2 and 4 joules, the frequency 5-50 Hz, the power between 0 to 100 W and the pulse duration is limited to a maximum of 600 microseconds.
To vaporize water (skin and soft tissue) the laser energy has to be produced with sufficient intensity in order to reach temperatures above the boiling point and fast enough to prevent energy losses through thermal conduction.
The diffusion of thermal energy produced with the Holmium Laser is minimal because the laser pulse duration of approximately 600 μsec (0.60 ms) and the estimated thermal relaxation time for the soft tissue is about 310 ms.
The Holmium Laser is a solid laser. The active source is a chemical element of the rare earth metal “Holmium (Ho)” which is located inside a YAG crystal composed of the elements yttrium-aluminum-garnet.
The laser operates at a wavelength of 2100 nm (Fig. 2) near the infrared region of the electromagnetic spectrum. The optical absorption coefficient in water is high (Fig. 3) and, as the tissue is almost entirely composed of water, the Holmium wavelength is significantly absorbed in this environment.
Most of the Holmium energy is absorbed superficially, therefore cutting or ablating superficially which avoids the risk of thermal injury to adjacent tissue. The zone of thermal coagulation is between 0.5 and 1.0 mm which is sufficient to achieve a satisfactory haemostasis.
Effects on the tissue using a Holmium Laser
The effect of incision, vaporization or coagulation that Holmium Laser produces on the tissue is mainly due to the distance between the end of the fibre (Fig. 4a) and the tissue and to the physical phenomenon called “Moses Effect” (Fig. 4b) i.e., the pulse of laser energy causes the formation of a bubble of steam at the end of the fibre which expands and lengthens the pulse duration (Video 1). When the last energy of the pulse is sent out – and while the bubble is still being formed – the laser beam passes through the water vapour that is inside the bubble and, because the absorption coefficient of the water vapour in the laser is low, most of the laser energy is deposited into the distal end of the bubble.
If the tip of the fibre is 5mm or more away from the surface of the tissue, the vapour bubble collapses, the water absorbs the laser energy and there is no effect on the tissue. As the end of the fibre progresses, the steam bubble makes contact with the tissue or the stone. The closer you are to the fibre the bigger the effect. If the tip of the fibre is less than 5mm, but not in contact with the tissue, the effect of the coagulation is prominent. When in contact the effect of vaporization, cutting or fragmentation is prominent.
Applications for urological surgery
What is the prostate?
The prostate is a male reproductive organ. It is located below the bladder and in front of the rectum. It is a gland in the shape of a chestnut and it weighs approximately 20 grams. The urethra passes through the centre of the prostate gland; urine leaves the bladder passing through the prostate.
Its main function is to add volume to the ejaculation, thus improving the motility and viability of sperm.
Benign Prostatic Hyperplasia
From the age of 45-50 years the prostate may begin to grow in a disorderly manner, resulting in what is known as benign prostatic hyperplasia (BPH) – a non-cancerous enlargement of the prostate gland. This growth often results in a series of obstructive problems when urinating. With age there is a higher risk of developing this disease.
Prostate growth can cause a number of symptoms which are divided into two types:
- Weak urinating stream (strength and size)
- Difficulty starting to urinate
- A sense that the bladder has not emptied completely
- Weak and intermittent urinary stream
- Prolonged dribbling at the end of urination
- Occasional incontinence
- Occasionally it is impossible to urinate (urinary retention)
- Getting up at night to urinate (nocturia)
- Frequent urination
- Having to go quickly to the toilet when feeling the need to urinate
Specialists will analysethe symptoms in order to reach the appropriate diagnosis.
There are various questionnaires which will help determine at which point of the illness the patient is. The most used are the IPSS (International Prostate Symptom Score) and the ICV (Quality-of-life Index). These questionnaires will enable the specialist to decide upon treatment http://www.usrf.org/questionnaires/AUA_SymptomScore.html
Depending on the patient’s condition and symptoms, there are several options for treating BPH.
The urologist will decide which course of action would be the best:
- Observation and periodic check-ups
- Treatment with medication
- Surgical intervention
When the prostate grows, symptoms worsen and the treatment with medication is not sufficient, it is time to operate and permanently remove the hyperplastic tissue. There are two possibilities for surgery: a laparoscopy (via the urethra) or a laparotomy (open surgery).
– Transurethral prostatic resection (TUR or TURP)
Transurethral resection of the prostate is a widely used technique which provides good results but can presenta number of complications:
- The patient will need a urinary catheter for several days.
- Due to blood loss during surgery, between 5%-15% require a blood transfusion.
- Patients in treatment with antiplatelet or anticoagulant medication have a high risk of bleeding.
- Other complications include urinary incontinence and impotence.
– Open Surgery (Adenomectomy)
An incision is made below the navel and the hyperplastic tissue (prostate adenoma) is removed. Open surgery is performed on greatly enlarged prostates. Possible complications are:
- Hospital stay for 5 to 8 days
- Risk of bleeding – between 5%-10% of patients require blood transfusion.
- Urinary incontinence and impotence
– Holmium Laser Treatment
The Holmium Laser treatments use laser energy to remove the prostate tissue that causes obstruction. The Holmium Laser treatment provides immediate relief of symptoms, improves the quality of life and has a low risk of complications. This treatment is usually performed using spinal or epidural anaesthesia. Due to the special characteristics of the laser, any size prostate can be treated.
The Holmium Laser penetrates superficially, avoiding thermal damage to adjacent tissue which would delay the relief of symptoms. There is a lower risk of post-operative complications than other more invasive surgical procedures (TUR or Open Surgery) and the recovery is quicker.
Blood loss, if any, is minimal. Patients usually return home without a catheter, either a few hours after the laser treatment or after spending the night in the hospital.
Pain relief is normally not necessary; patients can return to normal life shortly after treatment.
Benefits of treatment of BPH with the Holmium Laser:
- Safe and effective procedure
- Immediate relief of symptoms
- Virtually no blood loss
- Short hospital stay or treatment as an out-patient
- Patients taking anticoagulant medication can be treated
The 100 Watt Holmium Laser VersaPulse ® PowerSuiteTM (Lumenis) with its fibers and accessories provides the widest versatility of laser treatments on the market with the ability to vaporize and ablate prostatic tissue (HoLAP/HoLEP), incise strictures, ablate tumours and fragment stones.
The Holmium Laser combines the qualities of the carbon dioxide CO2 and the Neodymium lasers: YAG – providing the ability to cut and coagulate in a single device.
The characteristic of the wavelength of the Holmium Laser (2140 nm) is that the penetration depth is limited to 0.5 mm. It develops an energy that instantly vaporizes the tissue, removing it before it can conduct heat and produce a deeper thermal damage to surrounding tissue.
One of its main advantages is its haemostatic quality. Cauterizing the tissue during vaporization or incision minimizes blood loss.
The effect to coagulation associated with the Holmium Laser contrasts with the coagulative effects associated with other lasers such as the Neodymium: YAG or KTP laser (green light laser) where the wavelengths penetrate deeper into the tissue, resulting in a thermal destruction of more of the tissue which can lead to more acute irritant effects slowing down recovery.
The main applications of the Holmium Laser in the field of urology are laser lithotripsy and the treatment of benign prostatic hyperplasia (BPH).
The Holmium Laser can fragment all kinds of stones regardless of their composition or location. It can successfully treat almost any stone located in any part of the kidney, urethral tract or bladder.
The benefits of treatment of stones with the Holmium Laser are:
- Less blood loss during the treatment
- More effective treatment of any type of stone
- Less movement of the stone during the treatment
- Easier access by using very small and flexible fibers
- Higher degree of success in a single treatment (> 90%)
BPH can be treated either by vaporization or using the HoLAP technique (Holmium Laser Ablation Surgery). Vaporization is particularly suitable for small prostates; the HoLEP technique (Holmium Laser Enucleation of the Prostate) can treat all kinds of prostates, regardless of size.
The main advantages of Holmium Laser for the treatment of benign prostatic hyperplasia (BPH) are:
- Effective treatment of any size prostate using a minimally invasive procedure
- Provides immediate relief of symptoms
- Achieves lasting results
- Low post-operative morbidity
- Minimal blood loss
- Minimal associated complications
- Fewer days of hospitalisation and catheterisation
- Prostate tissue is available for subsequent histological analysis
Using the Holmium Laser for the minimally invasive treatment of BPH or stones leads to better results and has certain advantages compared to other types of treatment or types of laser, making the Holmium Laser an essential tool for the treatment of these pathologies.
Comparing surgical techniques
Benign prostatic hyperplasia (BPH) is a urologic disease that can be treated with Holmium Laser technique mainly by using HoLEP and HoLAP (enucleation and vaporization technique with the Holmium Laser)
Since the introduction of these minimally invasive surgical techniques, they have been subject to rigorous scientific studies to examine if they are equivalent to or better than traditional procedures such as transurethral prostatic resection (TUR/TURP) or open adenomectomy.
The results show that the Holmium Laser treatment leads to fewer complications and a faster return to normal activity (life) for the patient.
Clinical studies of greater relevance and reliability to evaluate the effectiveness and advantages of the different surgical techniques are the randomised clinical trials in which the allocation of patients to different groups of the study is done in a random manner.
Comparative studies of different surgical techniques for the treatment of BPH typically carry out an evaluation of a number of parameters that help to measure the degree of success of the treatments, such as:
International Prostatic Symptom Score (IPSS) and the Symptom Score Index of the American Urological Association (AUA)
They are indices that evaluate the symptoms of BPH.
They can be classified as asymptomatic (0), mild (1 to 7), moderate (8 to19) and severe (20 to 35).
Peak urine flow rate (QMax)
Measures the maximum urinary flow rate (ml / sec). The lower the QMax the more likely to have BPH.
Normally a QMax < 15 ml / sec shows deterioration in the normal uroflowmetry and may be due to an obstruction caused by a benign prostatic growth.
Post-Void Residual Urine Test (PVR)
This measures the volume of urine left in the bladder immediately after urination; it measures the urinating efficiency.
A volume larger than 100 ml is often a symptom of suffering from BPH.
Quality of Life Index (QOL)