De­hy­dra­tion does more than make peo­ple thirsty. It can place ad­di­tion­al strain on the heart and car­dio­vas­cu­lar sys­tem, par­tic­u­lar­ly when flu­id loss be­comes sig­nif­i­cant.

Ac­cord­ing to Brodie Marthaler, MD, a car­di­ol­o­gist at Mayo Clin­ic Health Sys­tem in Eau Claire, Wis­con­sin, the heart has to work hard­er when the amount of flu­id cir­cu­lat­ing in the blood­stream falls.

“Think of the heart as a pump. For it to work prop­er­ly, enough blood needs to re­turn to it with every heart­beat,” Marthaler said.

“When you be­come de­hy­drat­ed, the amount of flu­id cir­cu­lat­ing in your blood­stream de­creas­es. That means less blood re­turns to the heart, so it has to work hard­er to keep blood mov­ing through­out your body.”

The body has sev­er­al mech­a­nisms to com­pen­sate for the loss of flu­ids. Blood ves­sels nar­row to help main­tain blood pres­sure, while the heart rate in­creas­es to keep blood cir­cu­lat­ing.

How­ev­er, as de­hy­dra­tion be­comes more se­vere, these com­pen­sato­ry mech­a­nisms may no longer be suf­fi­cient. Vi­tal or­gans, in­clud­ing the brain, kid­neys, liv­er and di­ges­tive sys­tem, may then fail to re­ceive enough blood to func­tion prop­er­ly.

Recog­nis­ing the

warn­ing signs

The symp­toms of de­hy­dra­tion can vary de­pend­ing on its sever­i­ty. As flu­id loss in­creas­es, peo­ple may ex­pe­ri­ence a rac­ing heart­beat or pal­pi­ta­tions, fa­tigue, light­head­ed­ness, dizzi­ness, changes in vi­sion, short­ness of breath or chest dis­com­fort.

“If de­hy­dra­tion be­comes se­vere, it can lead to heat­stroke or faint­ing,” Marthaler said. “These are med­ical emer­gen­cies and should be eval­u­at­ed by a health­care pro­fes­sion­al im­me­di­ate­ly.”

Cer­tain groups are par­tic­u­lar­ly vul­ner­a­ble to de­hy­dra­tion, in­clud­ing old­er adults, chil­dren, ath­letes and peo­ple who work out­doors.

Peo­ple with heart dis­ease are al­so at in­creased risk.

“Peo­ple with heart fail­ure or oth­er forms of heart dis­ease should be es­pe­cial­ly care­ful,” Marthaler said. “Their hearts may have less re­serve to re­spond to the added stress of de­hy­dra­tion.”

He ex­plained that some peo­ple with heart con­di­tions al­so take med­ica­tions that re­move flu­id from the body, low­er blood pres­sure or slow the heart rate. These med­ica­tions can lim­it the body’s abil­i­ty to com­pen­sate for de­hy­dra­tion.

Cer­tain med­ica­tions, in­clud­ing di­uret­ics and GLP-1 re­cep­tor ag­o­nists, may al­so in­crease the need for peo­ple to pay at­ten­tion to their flu­id in­take.

Stay­ing ahead

of de­hy­dra­tion

There is no sin­gle amount of wa­ter that every­one needs to drink each day. For most healthy peo­ple, thirst can pro­vide a use­ful in­di­ca­tion that flu­ids are need­ed.

Peo­ple who know they will be ex­er­cis­ing for an ex­tend­ed pe­ri­od or spend­ing con­sid­er­able time out­doors in hot weath­er should in­crease their flu­id in­take be­fore­hand and con­tin­ue drink­ing reg­u­lar­ly.

De­hy­dra­tion is not al­ways im­me­di­ate­ly ob­vi­ous. Oth­er signs can in­clude a dry mouth, dry skin, dark or foamy urine and a burn­ing sen­sa­tion dur­ing uri­na­tion.

Urine colour can al­so pro­vide a sim­ple in­di­ca­tion of hy­dra­tion. Pale or clear urine gen­er­al­ly sug­gests ad­e­quate hy­dra­tion, while dark­er urine can in­di­cate that more flu­ids are need­ed.

Wa­ter is gen­er­al­ly an ex­cel­lent choice for main­tain­ing hy­dra­tion. How­ev­er, when a per­son is sig­nif­i­cant­ly de­hy­drat­ed, re­plac­ing elec­trolytes may al­so be im­por­tant.

The blood con­tains elec­trolytes such as sodi­um, potas­si­um and mag­ne­sium. Con­sum­ing flu­ids along­side foods con­tain­ing some salt can help re­place both flu­ids and elec­trolytes. Peo­ple tak­ing part in pro­longed ex­er­cise or en­durance ac­tiv­i­ties may al­so ben­e­fit from drinks con­tain­ing elec­trolytes.

Al­co­hol, mean­while, can con­tribute sig­nif­i­cant­ly to de­hy­dra­tion be­cause it af­fects the way the brain and kid­neys reg­u­late flu­ids and can in­crease flu­id loss. High­ly caf­feinat­ed bev­er­ages may al­so con­tribute to flu­id loss in some cir­cum­stances.

For peo­ple try­ing to re­hy­drate, wa­ter or elec­trolyte-con­tain­ing drinks may be prefer­able to sug­ary drinks and soft drinks.

Marthaler said pre­vent­ing de­hy­dra­tion is gen­er­al­ly eas­i­er than try­ing to cor­rect it af­ter sig­nif­i­cant flu­id loss has oc­curred.

“The best way to pre­vent de­hy­dra­tion is to stay ahead of it. Make drink­ing flu­ids a reg­u­lar part of your day. Drink­ing small­er amounts through­out the day is of­ten more ef­fec­tive than con­sum­ing a large amount all at once,” he said.

He al­so ad­vised peo­ple to plan ahead when ex­er­cis­ing, gar­den­ing or work­ing out­doors, par­tic­u­lar­ly in hot and hu­mid con­di­tions.

“If you’ll be gar­den­ing, ex­er­cis­ing or work­ing out­doors in hot, hu­mid weath­er, plan ahead, stay aware of how you’re feel­ing and ad­just your ac­tiv­i­ties if need­ed,” Marthaler said.

For peo­ple with heart dis­ease, old­er adults and those tak­ing med­ica­tions that af­fect flu­id bal­ance, main­tain­ing ad­e­quate hy­dra­tion re­quires par­tic­u­lar at­ten­tion.

Recog­nis­ing the ear­ly signs of de­hy­dra­tion, plan­ning for pe­ri­ods of heat or phys­i­cal ac­tiv­i­ty and reg­u­lar­ly con­sum­ing ap­pro­pri­ate flu­ids can help re­duce the strain placed on the car­dio­vas­cu­lar sys­tem and pro­tect over­all health.