By Bruce V. Voss, M.D-
In the book, Stress and Performance in Diving, Drs. Bachrach and Egstrom list four major predisposing conditions for panic' The state of the diver, coupled with stressors (i.e. cold) lead to impaired functioning. When you add the fourth condition, unforeseen events, you then have a recipe for panic. Within the realm of "state of diver" are listed entities such as physical condition, disease, fatigue, drugs, emotional level, and training.
This article deals with the singular issue of drugs and the diver. Drugs can be defined as "...any substance, synthetic or extracted from plant or animal tissue ... which is used as a mendicant to prevent or cure disease (Butterworth Medical Dictionary)"'. A handy schema to use in referring to drugs is to consider them either prescription or non-prescription medications. The latter can be further divided into illicit or legal medications. I would venture to say that most physical conditions that are being treated by a physician are managed with prescription medications versus non-prescription. The former include those medications for chronic condition, i.e. high blood pressure, heart rhythm problems, respiratory problems such as asthma, chronic obstructive pulmonary disease, bronchitis, etc. The non-prescription medications include the legal (or non-controlled) meds, i.e. alcohol, sinus medications, car/sea sickness pills, headache prescriptions, pain pills, etc. In the illicit category would be the hallucinogens, stimulants like cocaine and amphetamines, euphorics like marijuana, etc., which stimulate the nervous system.
An important distinction needs to be made here. That is, that the autonomic nervous system or the part of the nervous system that responds automatically to the environment (internal or external) can be subdivided into two components. The sympathetic nervous system is the "flight or fight" system and is opposed by the parasympathetic system. These two control body functions and are involuntary and don't require conscious input. The sympathetic nervous system involves increases in sweating, heart rate, blood sugar, and temperature in response to stimuli. The parasympathetic nervous system acts in the opposite direction and opposes a sympathetic nervous system input. Although one exception is the increase in gastrointestinal secretion in response to parasympathetic input. Activation of the sympathetic system is by way of epinephrine (adrenaline) and norepinephrine (noradrenaline). Drugs that activate the sympathetic system can do so because they are chemically similar to epinephrine/norepinephrine, i.e. ephedrine, pseudoephedrine, phenylephrine, phenylpropanolamine, or they can cause a release of those two mediators, i.e. cocaine, amphetamines, etc. Another mechanism for activation would be to give a drug that blocks the parasympathetic system (i.e. anticholinergic agent) and so have unopposed sympathetic activity (adrenergic). In essence, the balance between parasympathetic and sympathetic stimulation dictates the physiologic response that the patient shows, i.e. sympathetic or parasympathetic response.
In terms of legitimate, prescription medications used by physicians, an anatomic schema might serve us well. To start with, many people take meds to control mood, to enhance their sense of well being, and to enhance some personal experience, etc. While the schizophrenics and manic-depressives probably aren't highly represented in the technical diving community, I would guess that there are some divers out there who do take their daily "Valium or Prozac" or even amphetamine. (Remember the hyperactive child in your neighborhood? Well he was diagnosed as having "attention deficit disorder and has in fact grown up and is being treated with amphetamines.) Beyond the obvious problems of diving at depth and being on meds that alter mood and/or perception, the real unknown is the effect of depth on the medications' physiological effect. In the case of drugs known as psychotropics, one medication that has been used at depth (in the hyperbaric chamber) is Diazepam, i.e. Valium. That also is in a controlled environment and one that lends itself to intervention easier than at say 200 fsw/60 msw in open water. In fact, the late Jefferson Davis, M.D. in his "Medical Examination of Sports Scuba Divers" categorically excluded candidates for diving if they are on psychotropics or the nonprescription legitimate drugs that are used for mood altering or enhancing effects, alcohol is probably at the top of the list. We are all aware that alcohol intoxicates and decreases performance, but there are some other effects that this "drug" has associated with it. First, it dilates or opens up the blood vessels, which allows more blood to be brought to the skin and, therefore, more heat lost. It is associated with increased risk of vomiting and, therefore, aspiration (or inhaling stomach acid, contents, etc., into the lungs.) It, like tea and coffee, is a diuretic, which means it causes you to urinate more, which means your circulating blood volume decreases (less free water is available to dilute the blood volume). This predisposes divers to decompression sickness (DCS). Also, it will act in a manner that is more than additive (that is, 1 + 1 is greater than 2) when you couple it with nitrogen narcosis. Not to be excluded, caffeine (that is, coffee, tea and colas) has come under attack in the last few years. There is data to show that coffee will raise blood pressure, which, in the right individuals and diving at depth could give an unwanted hypertensive response. Also it can cause ectopy (extra beats) in the heart. This could lead to a fatal dysrrhythmia (malignant and erratic heart beat). While on the topic of caffeine and mood altering drugs, some of us do use caffeine preparations to combat fatigue. Getting "wired" from a caffeine-type agent and then diving, while it may enhance your attentiveness, it will also increase your heart rate, metabolic rate, respiratory rate and oxygen consumption rate, which in, and of itself is a recipe for disaster. The next area of concern is the respiratory tract. While we probably won't see the "Blue Bloaters" and "Pink Puffers" (chronic bronchitis and emphysematous patients respectively); we probably will see the diver who enjoys his/her cigarettes after their dive, or the diver who says he/she gets a little tight in the chest during a certain season or climate change. And what of the diver who has a yearly bout of bronchitis, lays off the cigarettes, and gets antibiotics for 10 days? Does that diver have an increased risk for barotrauma? Many would say yes. But with cyclical changes and a paucity of findings, these individuals will continue to dive. There are a variety of medications that can be prescribed with respect to the respiratory tract.
The majority of patients with respiratory meds in all likelihood will probably be using, bronchodialators, i.e. Ventolin, Proventil, or a theophylline mixture, i.e. Theodur. While the drugs themselves don't have a track record of causing problems at depth, the underlying condition that would cause one to use these meds do. If the pulmonary condition is bad enough to require bronchodilators, then few would disagree that the patient shouldn't be diving. Also, some patients with respiratory problems may be using, a prescription antihistamine. Usually these have the side affect of sedation. Needless to say, sedation and diving is a bad combination. There are a class of nonprescription "cold" meds, like the ephedrine or pseudoephedrine (Sudafed, Actifed) based meds that will cause an increase in heart rate, blood pressure, and will make you rather jittery or nervous. These affects come about because the drug is being used systemically, that is, in an oral form that circulates in the whole body. If the diver instead uses a locally applied, i.e. topical, agent like neosynephrine nose drops, the systemic effect will be less. Neosynephrine is an agent that acts as a vaso constrictor. It makes blood vessels, especially in the mucus membranes, shrink in size temporarily. This gives relief from the feeling of "congestion" in the sinuses/nose.
Lumping the gastrointestinal and genito-urinary systems together, there are a few meds that while they are used in these areas, there are effects elsewhere. Patients with spastic colitis or irritable bowel syndrome may be taking anti-cholinergic agents. These slow down the natural "parasympathetic nervous system". The end result can be decreased sweating, light insensitivity, blurring of the vision, dry mouth, etc. Also, the heart rate may increase. The decreased sweating can increase the risk of heat stroke in hot climates, etc. Also, some divers have been taking medications for ulcers, acid reflux or a hiatal hernia. A popular class of agents for these mild maladies is the histamine type two (H-2) blockers or antagonists. Cimetidine (Tagamet) or Ranitidine (Zantac) are in vogue. These may cause sedation/drowsiness or headaches, with Zantac causing less side effects than Tagamet. Some patients may also use a drug called Reglan (metoclopramide) for acid reflux. This drug is capable of producing sedation and "extra pyramidal reactions". In essence, musculo-skeletal reactions like spasms or contractions, etc. For those patients suffering Montezuma's revenge and taking Lomotil, there is also a word of caution. Lomotil is a combination of atropine (an anti-cholinergic) and diphenoxylate, a relative of meperidine (Demerol). Demerol is a narcotic and as such can and does cause sedation and respiratory depression, whose affects could be additive or synergistic when coupled with nitrogen narcosis. As an aside, antibiotics by themselves, seem to be OK, but the havoc they can cause in the GI tract can be unpleasant. First of all, they can cause nausea and vomiting. Also, many of them can cause a "colitis" picture with a resultant diarrhea that can not only be profuse, but can cause an acid base imbalance in the blood. The logical question would be, "Why would anyone with diarrhea want to dive?" Well, after paying a sizable amount of money for a dive trip and equipment, and while being selfmedicated from the local drugstore, it is really a question of not what's probable, but what's possible. And as far as human nature goes, anything is possible. A quick word about nausea and vomiting, since there are a wide variety of agents for nausea, ranging from pills to patches.
Most of these meds like Atarax, Antivert, Benadryl, Compazine, Phenergan, Thorazine, and Tigan, can cause sedation and when combined with nitrogen narcosis or DCS, the results may be very unpredictable. Some of these agents have as side-effects neurological ramifications besides just sedation. Those neurological effects can range from muscle spasms and seizures to coma and death. Obviously, a diver exhibiting those effects will be a liability to himself/ herself as well as to others.
Similar to antibiotics are the anti-viral agents. Most of these are injected, but there are a couple that are used in pill form and may be around in the diving population. It is not likely that an HIV positive patient under active anti-viral therapy would be diving, but it is likely that a patient with a history of herpes (genital/oral or shingles) may be. Since as a professor in medical school once said, "...The difference between love and herpes is that herpes is forever." Therefore, a drug that may be used long term in a diving individual is acyclivir (Zovirax). This agent does have a history of causing nausea, vomiting, and headaches. Divers using this agent should be aware of those side effects. Another agent used to decrease the symptoms of a viral complaint, that is, the common cold, is a drug called amantidine (Symetrel). You should know that this agent can also cause nausea, dizziness, and insomnia.
Moving on to the urinary tract, a major class of medications used here are the antispasmotics (the anti-cholinergic class) which, as stated before, can cause a dry mouth, blurred vision, increased heart rate, and sensitivity of the eyes to light. Also, decreased sweating can occur. Some of the agents in this class are Cystospaz, Ditarpan, Luvsin, Urised. Some of these agents if used in excess (or possibly coupled with DCS, nitrogen narcosis, etc.) have the propensity to proceed to a full-blown cholinergic crisis (Hypercholinergic State). That would entail restlessness, irritability, tremors, convulsions, and respiratory failure. There is another class of drugs that are used for stimulation of the male urinary tract, specifically for male sexual dysfunction (objective dysfunction, not just a feeling of inadequacy). This class is an adrenergic antagonist or blocker, specifically alpha '-. Daytohimbin is one of those drugs (yohimbine is the generic name) and it allows unopposed stimulation of the cholinergic system. The patient can exhibit decreased urine output, agitation/ irritability, increased blood pressure/heart rate, tremors, nervousness, headache and dizziness. Obviously, this is not a good thing to have happen while diving. In some patients, the physician may prescribe the drug Benemid (probenecid) to increase blood levels of penicillin and other antibiotics. What has also been found, though, is that this drug may increase the blood levels of lorazepam (a Valium type of drug), oral sulfonylureas (pills used to decrease blood sugar in diabetics) and the anti-inflammatory drugs like Tylenol, Ibuprofen (Motrin, Advil), etc.
The next area of medical management that is disproportionately represented in most people, and probably in more than a few divers, is the cardiovascular system. The intervention in this area runs the gamut from management of high blood pressure and heart rate control, to control of angina (chest pain). There is a multitude of agents used in cardiovascular conditions, but the most popular classes are the beta and calcium channel Mockers, alpha Mockers, ACE (Angiotension Converting Enzyme) inhibitors, diuretics, anti arrhythmics, vasodilators and vasopressors.
Taken as a whole, any patient taking these medications should think seriously about not diving while under the influence of them. Their collective side effects can range from low blood pressure and fast heart rate to bronchoconstriction (narrowing of the breathing passages) and severe, even fatal, aberrant heart rhythms. We also must keep in mind that we, as individuals, use medications and drugs that are not only not prescribed, but also in some cases outlawed by current federal regulations. Marijuana, cocaine, and alcohol are popular agents that affect the cardiovascular system as well as other systems. While used primarily for their euphoric and stimulating properties, these three alone can be unpredictable but in combination can be lethal. If you then add a hyperbaric situation, you have gone from an unpredictable situation to a potentially lethal combination of events that also threatens the other divers present. In an interesting recent medical report, it was found that while both alcohol and cocaine individually can cause cardiac damage, together their effect was more than 1) plus I greater than 2) additive'. Needless to say, with the complexity of the individual drugs and their interactions with each other, any diver undertaking their use while diving would be well served in seeking professional advice. The potential scenario of the respective drug and its unknown contribution to a hyperbaric scenario, cannot be underestimated nor predicted accurately.