How long does seasickness usually last

Seasickness - current aspects of an ancient ailment

Pathophysiology
The “Sensory Mismatch Theory”, based on the concept of the contradiction between spatial information and the perception of movement, has established itself as an explanation of the pathophysiology of seasickness. The biogenic amine histamine is held responsible as one of the relevant central triggers for the symptoms of the disease.

Fig. 1: Life raft during wave exposure at about 1m wave height (original illustration from [11])

Little is known about the "sopite syndrome" that occurs at the beginning of seasickness and its effects on the general performance of soldiers. This is to be investigated in a project that has just started.

therapy
In addition to the anticholinergics (scopolamine), the H1-Antihistamines (cinnarizine, dimenhydrinate) are the pharmacological backbone of the therapy, but at the cost of side effects that, among other things, impair vigilance and thus considerably reduce the navigator's fitness to drive in complex situations.

Vitamin C also has a certain antihistamine effect and is usually almost free of undesirable side effects. Our own results of a placebo-controlled crossover study showed a reduction in the symptoms of kinetosis by the administration of 2 g of vitamin C, especially in women and younger men.

Conclusion
The problem area "seasickness" is not only a challenge with regard to therapy - from the sopite syndrome to the full picture of kinetosis - but also requires a look at the tension between the serviceability of the person concerned with and without medication.

Key words: Seasickness, histamine, sopite syndrome, therapy, ability to serve

Keywords: seasickness, histamine, sopite syndrome, therapy, fitness for service

introduction

Kinetosis (motion sickness) is the term used to describe the vegetative symptom complex that occurs as a result of the organism's physiological reactions to actual and apparent movements of itself or the environment [1]. Movement diseases are as old and well-known as the respective forms of movement themselves - be it on land in a vehicle, in an aircraft or at sea - whereby seasickness is certainly the best-known form of kinetosis.

Historically, the problems of seasickness run through history right up to the famous Lord Nelson, who is said to have suffered from seasickness throughout his life. In the full picture of its manifestation, seasickness leads to an extensive inability to act, a very serious feeling of illness and, due to the recurrent vomiting, in some cases to considerable medical problems.

In an exaggerated formulation, Wolfgang Hausner, an Austrian parade sailor, put it in a nutshell: “First you are afraid that you will die, then that you won't”.

In fact, it can be problematic for a ship's command if a significant part of the crew of a ship suffers from symptoms of seasickness in bad weather, especially because in such a weather situation special demands are often made on the crew - be it during maneuvers, load securing or in combat and dangerous situations.

In addition, there is a trend towards smaller crews in both military and civil shipping, meaning that it is less and less possible to replace the individual on board in the event of sick leave, and each crew member has to perform increasingly diverse and complex tasks.

Against this background, seasickness must also be considered in the German Navy, with its usually relatively young crews and an increasing proportion of women. Young people and women in particular are actually more susceptible to kinetosis, so that seasickness is also a current problem area for the navy [2 - 5].

Even if the habituation is to be expected and hoped for in most of those affected - with the effect that after a few days the susceptibility will decrease significantly - there is a proportion of people who do not adequately habituate. And there are also swell situations that are so difficult that a large part of the crew becomes seasick despite normal habitat.

Fig. 2: Results of the perceived severity of the symptoms (original illustration from (11)])
Against this background, the scientific examination of the phenomenon of seasickness continues to be of considerable importance in maritime medicine.

On the pathomechanism of seasickness

The "Sensory Mismatch Theory"
The theory of the "sensory mismatch" as a trigger for the development of seasickness as a special form of kinetosis has become generally accepted. Accordingly, the transmission of contradicting information from the vestibular, visual and somatosensory systems to different centers of the brain (hypothalamus, pons, medulla oblongata) and to the center of equilibrium in the cerebellum is discussed as the cause
[6-8]. This happens when the sense organs provide contradicting information about the spatial position and movement of the body. The delayed occurrence of kinetosis after movement is attributed to the neural mechanisms in the cerebellum and nucleus vestibularis, above all to the synthesis of neurotransmitters such as histamine. Depending on the target concentration of the individual neurotransmitters, a certain time interval is required to trigger the respective symptoms. In addition to histamine, serotonin, acetycholine and glutamate receptors should be mentioned in this context [9].

The role of histamine in the pathophysiology of seasickness
In this context, histamine seems to play a special role. For example, it is known that foods rich in histamine can worsen seasickness symptoms. The biogenic amine is believed to be partly responsible for triggering vomiting in seasickness [10, 11]. Histamine is formed from the amino acid histidine with the help of the enzyme histidine decarboxylase and stored in tissue mast cells, basophilic granulocytes and nerve cells. In animal experiments, a direct connection between seasickness and histamine metabolism has been demonstrated. Excessive exercise resulted in increased histamine concentrations in the inner ear and in the brain of the test animals [6, 12]. These findings and the fact that antihistamines are used with good clinical efficacy in the treatment of seasickness [7] underscore the important role of histamine in the development of this kinetosis.

The severity or severity of seasickness and the resulting symptoms are unpredictable and vary from person to person. The physical symptoms of seasickness include fatigue, concentration and coordination disorders, paleness, hypersalivation, hyperventilation, headaches, nausea and vomiting [5, 13 - 16]. In addition to the physical symptoms, the so-called Sopite syndrome should be mentioned. Sopite syndrome specifically describes the manifestations of seasickness that occur without physical symptoms. These include above all psychological symptoms such as persistent fatigue, depressive moods, apathetic behavior, reluctance to work and, in particular, hyperosmia, the increased sense of smell [17].

It is known that getting used to the situation can lead to a decrease in symptoms related to seasickness [18].

The "Sopite Syndrome" - still many questions - open

It is also still unclear to what extent the early symptoms of seasickness and especially the -Sopite - syndrome affect the capacity of the person concerned on board. Initial study results in this research field suggest a significant reduction in multitasking cognitive abilities in the case of mild motion sickness and Sopite syndrome [19].

Fig. 3: Number of test persons who had to leave the exposure prematurely at least once due to the severity of the symptoms (original figure from [11])

The question also arises to what extent, in addition to attention and the ability to concentrate, physical abilities such as strength, coordination and endurance in particular are negatively influenced by the early forms of seasickness and Sopite syndrome and whether and when the person affected even perceives their limitations themselves .

The investigation of the effects of the Sopite syndrome appears to be of great importance, since the ship's command has to be able to rely on the key personnel without restrictions in heavy seas, in particular, and cannot convince himself of the performance of the individual in individual cases.

Knowledge of the restrictions to be expected when seasickness begins before the full screen occurs with vomiting and incapacity for work and, in particular, knowledge of the self-perception of one's own vigilance disorders can in future help in difficult situations to use the most suitable personnel effectively for the benefit of all under the given conditions.

Therapeutic strategies in the treatment of seasickness

The important role of histamine in the pathophysiology of seasickness is also reflected in the established therapeutic strategies:

Preparations from the substance group of antihistamines represent an important group of active substances in therapy, including cinnarizine (pericephal®), Meclozine (postadoxin®) and dimenhydrinate (Vomex®, Travel tablets®, SuperPep chewing gum®). Anticholinergics in the form of scopolamine-containing transdermal patches (transdermal therapy system scopolamine = TTS-S) [20, 21] are also widely used. What all these substances have in common is that they cannot completely prevent or suppress seasickness, but are able to influence the symptoms in a significantly favorable manner.

However, this is paid for by a relatively wide range of side effects of the substances mentioned: The most common of them include tiredness, slower reactions, and coordination and concentration disorders [22, 23]. Scopolamine-containing plasters also lead to accommodation disorders and dry mouth [24]. The use of these drugs therefore poses a safety risk for many activities on board a ship [21, 25 - 27].

In addition to these pharmacological approaches, general and naturopathic measures are also used to suppress seasickness. There are individual data on the fact that ginger can be used as an alternative antiemetic with few side effects [28, 29]. Furthermore, resting or sleeping has proven to be advantageous, and special approaches such as horizon goggles to reduce the sensory mismatch are also repeatedly discussed.

Influence of high-dose vitamin C on symptoms of seasickness
The presumed symptom-relieving efficacy of high-dose vitamin C was pursued in an initial approach at the Naval Medical Institute of the Navy (SchiffMedInstM) as part of a prospective, randomized, double-blind and placebo-controlled study approach. The standardized effects of vitamin C were tested experimentally on volunteers in a life raft in a wave pool.

The background to this study was a previously described inverse relationship between the blood levels for vitamin C and histamine, so that a certain antihistamine effect was assigned to vitamin C as a working hypothesis, which could have a positive effect on the symptoms of seasickness [30 - 35].

Two 20-minute exposure of 70 (63 evaluable) test persons in the life raft in swell after taking 2 g of vitamin C versus 2 g of citric acid was able to confirm the hypothesis: Some data showed significantly that the respective wave exposure under the medication with vitamin C. was found to be less uncomfortable compared to exposure to placebo. This could be demonstrated on the one hand in the evaluation of the direct comparison of both exposures, but also in the maximum possible length of stay in the life raft for those who had to leave the life raft prematurely at least once because of severe symptoms.

Women overall and younger men (<27 years) benefited more from vitamin C compared to placebo. In addition, the previously known considerable habituation effect to the swell was shown overall through often fewer symptoms on the second day of exposure, regardless of the test medication [11].

In the test arrangement, vitamin C has proven to be suitable for positively influencing the symptoms of seasickness. The extent to which this positive effect of vitamin C, which is almost free of side effects, can also be used in practice at sea under real bad weather conditions must be investigated in a future field study on board.

Seasickness and capacity for service - a field of tension

Against the background of the sometimes very serious symptoms of seasickness, the question arises whether the person concerned is directly required for the direct operation of the ship or not, whether he urgently needs to remain "on post" for the safety of the ship even in heavy seas or can be treated as a patient and, if necessary, lay in the bunk In the latter case, side effects of the therapeutic agents are certainly acceptable if they can improve the state of nausea.

In the other case, when the person concerned is needed immediately, it becomes much more difficult because it is necessary to weigh up which “evil” has fewer disadvantages: an important functionary, without medication on duty, but with discomfort up to nausea / vomiting and reduced performance - the so-called "Sopite Syndrome" - or an improved member of the crew, who may, however, show relevant side effects of the therapeutic agents, which can significantly reduce the ability of the person concerned to drive. Particular attention should be paid to tiredness, concentration and accommodation disorders.

Research outlook

The problem area "seasickness" on board modern naval ships therefore requires the search for several possible solutions:

On the one hand, substances or measures should be found and investigated that are able to favorably influence the symptoms without impairing the ability to circulate through their spectrum of side effects.

On the other hand, the limitation of performance in the course of the illness "seasickness" from the first symptoms to full vomiting / incapacity and the so-called sopite syndrome (not primarily somatic aspects of early seasickness) should be examined in order to be able to assess with which persons the crew who are not yet under any medication can currently be fully reckoned with in a difficult situation.

central message

  • Seasickness is still a relevant problem in shipping.
  • To explain the pathophysiology of seasickness, the "sensory mismatch theory" has prevailed; Histamine is one of the central trigger substances.
  • Anticholinergics and antihistamines form the backbone of therapy, but the undesirable side effects can impair the ability to drive.
  • Vitamin C in high doses shows effectiveness in reducing the symptoms of seasickness.
  • Whether the so-called Sopite syndrome has relevant negative effects on the performance of the seafarer is currently being investigated.

literature

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Date: 04.03.2016

Source: Military Medical Monthly 2016/2