Sunday, July 1, 2018

Laser and its Medical Applications

                         Laser and its Medical Applications
                                         Dr. Dwijesh Kumar Panda
Laser is an acronym for Light Amplification by Stimulated Emission of Radiation. It is a device that produces intense focused coherent (monochromatic) light. There are three types of lasers: gas, liquid and solid state lasers. All these have many medical uses. In this article, I shall outline these uses after discussing basic principles and operations of lasers.
When an atom is supplied energy from outside, it receives it in discrete amount because its energy states are discrete (quantized). The atomic electron “jumps” from its lowest (ground) state to upper (excited) states. This is absorption. Once in the excited state, the atom emits a photon after a short time which is called spontaneous emission. If there are other photon present, they stimulate the atom to emit more photons which is called stimulated emission.
            In certain cases like ruby which is a crystal with CV2O3 impurity in AC2O3, the chromium atom has a long- lived or metastable state in between its ground and first excited state, i.e., the atom can stay in this state without emitting any photon for a time longer than its first excited state. As a result all the electron that are excited to its first excited state come down to the intermediate state as a result of which they stay there for a long time and this metastable state gets crowded. We can say that electrons are “pumped” from the ground state to the intermediate metastable state. This is called “optical pumping”. Eventually these electrons come down to the ground state by emitting large number of photons: each electron emitting one photon and the photons stimulate others to come down. All of these photons have some wavelength. As a result, the light is intense and coherent. All this is illustrated in Fig 1.
Fig. 1. Stimulated Emission
Figure 2 is a schematic diagram of Ruby laser in operation showing a ruby rod (gain medium) inside a coiled lamp which is the source of power called the “optical pump”. At one end of the rod there is high reflecting mirror and at the other end there is a partially transparent mirror, which, apart from reflecting light, allows optical power of the laser to come out. The entire system is called a laser oscillator.


Lasers are used predominantly as a source of energy to effect tissue destruction but also provide a coherent energy source for phototherapy or confocal microscopy, which allows for real-time imaging of tissues.
Lasers destroy tissue through one of these mechanisms, including production of heat (photothermal), destruction of chemical bonds (photoablative), or reaction with a photosensitizer (photochemical). Selective photothermolysis describes the use of specific wavelengths of laser energy to target specific chromophores and thus minimize damage to adjacent tissues. The interaction between the laser and tissue depends upon the wavelength, power, duration of exposure, and properties of the target tissue.
 Lasers are used in a variety of clinical applications commonly related to external structures such as the skin and cornea. However, minimally invasive technology allows access to deeper structures including the gastrointestinal mucosa, biliary tree, bronchial structures and urinary tract via endoscopy, and hollow and solid organ surfaces via laparoscopy and thoracoscopy.
The eye and skin are the organs that are more susceptible to damage by laser radiation. The biological effects induced by nonionizing radiation are similar for coherent and incoherent sources: however, laser radiation produces greater radiant exposures. In the workplace, eye protection is required by the United States Occupational Safety and health Administration (OSHA)
CLINICAL UTILITY OF LASERS — Lasers are used in a variety of clinical applications commonly related to external structures that are easily reached, such as the skin and cornea. Minimally invasive technology allows access to deeper structures including the gastrointestinal mucosa, biliary tree, bronchial structures, and urinary tract via endoscopy and hollow or solid organ surfaces via laparoscopy and thoracoscopy. Most commonly, tissue ablation occurs as a consequence of thermal effects.
·      Dermatology – Progress in laser and light therapy technology has led to the development of safer and more efficient methods of achieving the desired effects on skin. Skin cooling limits inadvertent damage to tissues adjacent to the targeted sites.
·      Gastroenterology – Pulse dye lasers and Q-switched solid-state lasers are used to fragment gallstones identified during choledochoscopy and ablate mucosal tumors. Confocal laser endomicroscopy has aided in the differentiation between dysplastic and malignant tissue.
·      In bronchoscopy, lasers are used to either photocoagulate or vaporize tissues obstructing the airway. They can also be used to make concise radial incisions to enhance airway dilation in central airway strictures. Lasers have also been used to remove blebs and bullae during thoracoscopy.
·      Cardiology and cardiac surgery – Laser energy is used to create transmural channels in ischemic myocardium to restore myocardial perfusion in a procedure called Trans myocardial laser revascularization. The procedure can be performed using a carbon dioxide or holmium: YAG laser.
·      Ophthalmology – The excimer laser is used to remove a precise amount of corneal stroma during laser-assisted in-situ keratomileusis (LASIK), which is one of the most common applications of laser.
·      General surgery – In general surgery, laser energy can be used to provide hemostasis or to ablate tumors identified in solid organs such as the liver.
·      Gynecology – The Nd: YAG or carbon dioxide laser is used for tissue ablation in a variety of gynecologic applications.
·      Urology – Lasers can be used to fragment ureteral stones but are becoming more popular for the treatment of benign prostatic hyperplasia. Benign prostatic hyperplasia is a condition that causes urinary symptoms in men, such as the frequent need to urinate, inability to empty the bladder, trouble starting urination and frequent urinary tract infections. These are caused by an enlarged prostate blocking normal urine flow.
·      Green Light laser therapy treats benign prostatic hyperplasia by removing the excess prostate tissue that is blocking urine flow. After the patient is put to sleep, a fiber is placed into the urethra and passed to the prostate where it is quickly heated, vaporizing the extra prostate tissue. This procedure usually results in a very quick resolution of all urinary symptoms in most patients. Green Light laser therapy provides many benefits over the more traditional therapy for benign prostatic hyperplasia. There is a much quicker recovery time with laser therapy; most procedures are done on an outpatient basis and the patient goes home a few hours after surgery. There is a much lower risk for bleeding. Results are almost immediate, versus waiting several months for results with medications. The risk of complications, such as erectile dysfunction or bladder injury, are also lower. Greenlight laser therapy also has the additional benefit of not needing a catheter after surgery or only needing it for less than 24 hours
·      Vascular surgery – Lasers are commonly used to manage the visible signs of chronic venous disease. Several types of lasers might be used depending upon the size and depth of the vein to be treated.
·      Dentistry – Although incoherent light may be used in conjunction with photoactive dental bleaching systems, coherent light produced from a diode laser has also been found to be effective.
I acknowledge discussion with Prof. Trilochan Pradhan, on fundamental principles and operational aspects of laser.
  1. Boulnois, JL. Photophysical processes in recent medical laser developments: A review. Lasers Med Science 1986; 1:47.
Declaration:  I declare that this article has not been reproduced. Submitted to the Secretary, Odisha Bigyan Academy for publication in “Science Horizon”
                                                Dr. Dwijesh Kumar Panda, M.D, Ph.D. (Medicine)
                                                 Senior Scientist awardee, Odisha Bigyan Academy.
                                                                     Contact: (0674) 2543122.

Insomnia in elderly people

Insomnia in elderly people
Dr. Dwijesh Kumar Panda
 Insomnia is a condition of impaired sleep, with difficulties in initiating or maintaining sleep. It is a very common medical complaint in primary care patients. The prevalence of insomnia is over 60 percent.  Insomnia is associated with multiple consequences that have a negative impact on quality of life and the ability to perform normal functions. In addition, insomnia is a strong predictor of the development of psychiatric disorders
Medication side effects – Medications that are being used for other indications may have arousal or stimulant properties that can exacerbate sleep disturbances. These include opioids, steroids, beta-receptor agonists, many antidepressants, and psychostimulants.
 Symptoms of insomnia — People with insomnia often:
●Have trouble falling or staying asleep
●Feel tired or sleepy during the day
●Forget things or have trouble thinking clearly
●Get cranky, anxious, irritable, or depressed
●Have less energy or interest in doing things
●Make mistakes or get into accidents more often than normal
●Worry about their lack of sleep
Measures to improve insomnia 
 ●Sleep only long enough to feel rested and then get out of bed
●Go to bed and get up at the same time every day
●Do not try to force yourself to sleep. If you can't sleep, get out of bed and try again later.
●Have coffee, tea, and other foods that have caffeine only in the morning
●Avoid alcohol in the late afternoon, evening, and bedtime
●Avoid smoking, especially in the evening
●Keep your bedroom dark, cool, quiet, and free of reminders of work or other things that cause you stress
●Solve problems you have before you go to bed
●Exercise several days a week, but not right before bed
●Avoid looking at phones or reading devices ("e-books") that give off light before bed. This can make it harder to fall asleep.
Other things that can improve sleep include:
●Relaxation therapy, in which you focus on relaxing all the muscles in your body 1 by 1
●Working with a counselor or psychologist to deal with the problems that might be causing poor sleep
 Medicines to help sleep — Yes, there are medicines to help with sleep. But you should try them only after you try the techniques described above. You also should not use sleep medicines every night for long periods of time. Otherwise, you can become dependent on them for sleep.
Insomnia is sometimes caused by mental health problems, such as depression or anxiety. If that's the case for you, you might benefit from an antidepressant rather than a sleep aid. Antidepressants often improve sleep and can help with other worries, too.
Addressing the environment — Environmental steps that appear to help reduce insomnia include:
Keeping patient rooms cool, well ventilated, and with low light at night
The use of white noise machines.
Limitations on the use of computers, smartphones, and iPads at night and other stimuli
(Television, loud music)
Lifestyle modifications — a number of lifestyle modifications may promote a more regular sleep pattern and can be instituted in a palliative care setting. These include reducing or avoiding:
Daytime naps
Large meals or excessive fluids at bedtime
Stimulants (caffeine)
Benzodiazepines — while being the most commonly prescribed class of medications for insomnia in the general population, benzodiazepines are associated with adverse effects that should be carefully considered in the palliative care patient
Nonbenzodiazepines — Nonbenzodiazepines are a class of prescription medicines that are somewhat similar to benzodiazepines. These medications may have fewer side effects compared with benzodiazepines because they work more on sleep centers and less on other areas of the brain. They tend to be short acting, so they are also less likely to produce hangover sedation in the morning. Some can also be prescribed for a longer period of time.
Nonbenzodiazepines used to treat insomnia include zaleplon , eszopiclone , zolpidem,  and zolpidem extended release, Zolpidem is also available as a dissolving tablet, an oral liquid spray, and as a dissolving tablet at a lower dose for middle of the night use,
Do not take these medicines with alcohol or other sedating drugs, and do not take more medicine than your doctor recommends.
Melatonin — Melatonin is a neurohormone secreted by the pineal gland that can assist with maintaining sleep-wake cycle. It is a widely available over-the-counter agent that is often used to alleviate insomnia, despite the lack of prospective data
PREGABALIN has shown efficacy for generalized anxiety disorder (GAD) in comparison with placebo in several randomized trials. Pregabalin inhibits calcium currents via high-voltage-activated channels containing the a2d-1 subunit, though the relationship of this mechanism to its efficacy in GAD is not known. It was approved in 2006 for the treatment of anxiety in Europe. Pregabalin is not approved for treating GAD by the US Food and Drug Administration. The doses for pregabalin range from 50 to 300 mg, though many patients may need a total daily dose of greater than 150 mg. Side effects include sedation and dizziness. Tolerance, withdrawal, and dependence are possible, but pregabalin is generally better tolerated than benzodiazepines
Dementia — Patients with dementia are at an increased risk for experiencing insomnia as a potential symptom of their underlying dementia illness or from associated conditions (sun downing, agitation, or other delirium).
Maximizing exposure to natural light in the mornings and light exercise, when feasible, can help entrain more normal circadian rhythms.

Insomnia is a condition of impaired sleep, with difficulties in initiating or maintaining sleep, and/or experiencing sleep as nonrestorative and unrefreshing, despite having the appropriate opportunity for sleep to occur. It is estimated that insomnia affects over 70 percent of palliative care patients.
Addressing environmental issues may help address external factors exacerbating insomnia in these patients. This includes keeping patient rooms cool, well ventilated, and with low light at night, the use of white noise machines, and limitations on the use of computers at night and other stimuli ( television, loud music)
A number of lifestyle modifications may promote a more regular sleep pattern and can be instituted in a palliative care setting. These include reducing or avoiding daytime naps, large meals before bedtime, drinking a large amount of fluid in the evening, or stimulants, including caffeine. Daytime light exposure and activity levels should be increased when possible.
Clinicians and staff should minimize disruptions of a patient’s sleep. Regardless of setting, dimming lights in the vicinity of the palliative care patient’s room may provide a simple cue to others to maintain a calm, quiet, sleep-promoting environment.
Medications be prescribed for insomnia only after attempting nonpharmacological-based modifications. There is no single pharmacologic approach that can be recommended for all patients. The approach to the selection of a sleep aid must be individualized, and the lowest effective dose should be administered. As with most drugs, patients in palliative care must be carefully and continually monitored for both positive effect and the development of adverse effects, particularly as the patient’s disease progresses.