Clinical
Practice Guideline
for
HYPERTENSION
Developed for the
Aerospace Medical
Association
by their constituent
organization
American Society of
Aerospace Medicine Specialists
Overview: The relationship between blood pressure (BP) and risk of
cardiovascular disease (CVD) events is continuous, consistent, and independent
of other risk factors. The higher the
BP, the greater is the chance of myocardial infarctions, heart failure, stroke,
and kidney disease. For individuals
40–70 years of age, each increment of 20 mmHg in systolic BP (SBP) or 10 mmHg
in diastolic BP (DBP) doubles the risk of CVD across the entire BP range from
115/75 to 185/115 mmHg.
The
7th Joint National Committee on Prevention, Detection, Evaluation,
and Treatment of High Blood Pressure (JNC VII) classification of hypertension,
based on two or more properly measured readings, with confirmation of an
elevated reading in the contralateral arm, at each of two or more visits after
an initial screen, is listed in Table I.
Table I. Blood Pressure Classification.1
|
Condition |
SBP (mmHg) |
DBP (mmHg) |
|
Normal
BP |
<120 |
and <80 |
|
Pre-HTN |
120-139 |
or 80-89 |
|
HTN
|
140-159 > 160 |
or 90-99 or > 100 |
1These definitions apply to adults on no antihypertensive
medications and who are not acutely ill.
If disparity exists in categories between SBP and DBP, the higher value
defines the severity of the HTN.
For
aeromedical purposes, the USAF defines hypertension for flying personnel as a
3-day average systolic blood pressure greater than 140mm Hg or a 3-day average
diastolic blood pressure greater than 90mm Hg.
Asymptomatic trained flying personnel with average systolic blood
pressure ranging between 141 mmHg and 160 mmHg, or average diastolic blood
pressure ranging between 91 mmHg and 100 mmHg, may remain on flying status for
up to 6 months (from the date the elevated blood pressure was first identified)
while undergoing non-pharmacological intervention to achieve acceptable values.
While HTN is the
dominant risk factor for stroke, coronary disease is associated with a number
of other risk factors that are often co-morbid with HTN, and should be
addressed at the same time. These
include obesity, dyslipidemia, diabetes, cigarette smoking, and physical inactivity. Additional but non-modifiable risk factors
for CVD include a family history of premature CVD and the patient’s age.
The recommendations
of JNC VII include considering identifiable causes of HTN in all patients,
especially when HTN is initially diagnosed under the age of 35, or when the
onset HTN is rapid, or when a patient’s HTN does not respond to treatment. Although most HTN is idiopathic, relatively
common causes of secondary hypertension include alcohol use, obesity, sleep
apnea, and renal disease; these are readily addressed by history, physical
exam, or initial lab studies. Pursuing a
work-up for rarer causes of secondary HTN (e.g., renal vascular disease) should
be guided by consultation with an internist or nephrologist.
Lifestyle
modifications, which are listed in Table II, are often effective at treating
HTN and associated with improvement in a patient’s other major CVD risk factors
and should always be considered as first-line treatment. If lifestyle modifications alone are
inadequate JNC VII recommends thiazide-type diuretics for most patients with
HTN, either alone or in combination with another class of drug.
Table II.
Lifestyle modifications for treatment of hypertension:
|
Modification |
Recommendation |
Approximate SBP Reduction (Range) |
|
Weight reduction (10kg/22lbs) |
Maintain
normal body weight (body mass index 18.5–24.9 kg/m2). |
5–20 mmHg |
|
Adopt Dietary Approaches to Stop
Hypertension (DASH) eating plan |
Consume
a diet rich in fruits, vegetables, and low fat dairy products with a reduced content of saturated
and total fat. |
8–14 mmHg |
|
Dietary sodium reduction |
Reduce
dietary sodium intake to no more than 100 mmol per
day (2.4
g sodium or 6 g sodium chloride). |
2–8 mmHg |
|
Physical activity |
Engage
in regular aerobic physical activity such as brisk walking (at least 30 min per day, most days of the week). |
4–9 mmHg |
|
Moderation of alcohol consumption |
Limit
consumption to no more than 2 drinks (1 oz or 30 mL ethanol; e.g., 24 oz
beer, 10 oz wine, or 3 oz 80-proof whiskey) per day in most men and to no
more than 1 drink per day in women and lighter weight persons. |
2–4 mmHg |
Aeromedical Concerns: The long term vascular complications of HTN are an increased risk of cardiovascular events such as myocardial infarction and stroke, potentially resulting in sudden incapacitation, or death. Because lifestyle modifications are considered to be first line interventions, and are associated with negligible aeromedical side effects, each aviator should be individually evaluated for potential benefit from lifestyle modifications, used alone, or in combination with medication(s). While numerous medications are effective in lowering BP, some drugs have modes of action that may adversely affect the flyer. Medications that act via direct vasodilatation or autonomic vasoregulation are avoided in favor of those that work via volume reduction, such as diuretics, or via the renin-angiotensin axis, such as angiotensin converting enzyme inhibitors (ACEi), or angiotensin receptor blockers (ARB). Medications that affect cognitive capacity (e.g., central α-adrenergic agonists) should also be avoided or used with great caution.
Medical
Work-up: Initial evaluation of
hypertension in an aviator should not differ from a non-aviator. It should include a thorough history and
physical examination, and a review of the medical record for past blood
pressure readings. History should focus
on diet, alcohol, sodium intake and family history. The physician should directly question
whether the aviator has experienced symptoms of flushing, headaches, nocturia,
chest pain or claudication. A thorough
physical should include an examination for carotid bruits, hypertensive retinal
changes, reduced or absent pedal pulses, a pulsatile abdominal mass, and an S4
heart sound or murmur. Any aviator under
the age of 35 with hypertension, or with sudden onset of marked hypertension at
any age, or whose hypertension does not readily respond to treatment should be
evaluated for secondary hypertension. If the clinical history suggests concomitant
coronary artery disease, a maximal Bruce Protocol Stress Test or other
appropriate diagnostic/screening test should be accomplished.
The extent of such a work-up should be determined in consultation with an internal medicine specialist. Basic studies for every aviator with hypertension should include a hematocrit, fasting glucose, lipid profile, serum electrolytes, blood urea nitrogen, serum creatinine, and a urinalysis. Nonpharmacologic therapy or lifestyle modifications are recommended for initial treatment of hypertension in the range of systolic 140-159 and/or diastolic 90-99 mm Hg. Possible modalities include weight reduction if overweight, limiting alcohol ingestion, regular exercise, smoking cessation, decreased dietary sodium, and increased dietary potassium. Additional risk factors, such as hyperlipidemia, should also be looked for. A common concern in the aeromedical community is that mild elevation in blood pressure is just “white coat hypertension.” The latest opinion is that this entity is not a normal variant and needs to be watched closely, as it does have evidence of target organ effects.
Subsequent evaluations for aviators waivered for hypertension should include fasting glucose, electrolytes, blood urea nitrogen, creatinine and urinalysis. A resting electrocardiogram should also be performed and compared with prior tracings. Blood pressure should be measured annually, followed by a three-day blood pressure check if it is elevated. Weight changes should be monitored. The aviator should be questioned concerning the development of symptoms related to coronary artery disease or medications.
In clinical
trials, antihypertensive therapy has been associated with reductions in stroke
incidence of approximately 35–40%; myocardial infarction, 20–25%; and heart failure,
more than 50%. The Framingham Heart
Study confirmed the benefit of long-term antihypertensive therapy on CVD
disease incidence and mortality with a 40% reduction of a 10-year risk of CVD
death for treated versus untreated HTN.
For aeromedical purposes the goal of antihypertensive therapy in
patients with uncomplicated HTN is to reach a BP below 140/90 mmHg.
The classes
of antihypertensive agents available to military aviators include diuretics
(thiazide, with or without triamterene), ACEi (lisinopril
or ramipril) and ARB (losartan). These
drugs are effective as monotherapy, and when used as such may be granted
unrestricted waiver. The combination of
diuretic with ACEi or ARB is synergistic, and usually
very effective at lowering BP; it is restricted to non-high performance
aircraft. Beta-blocker (specifically
atenolol) may be used as a third line drug, when diuretic combined with ACEi or ARB is insufficient. (Beta-blockers are often poorly tolerated in
aviators due to fatigue, reduced exercise capacity, and impotence; whether used
alone or in combination they are restricted to non-high performance aviators). The civilian community uses a broader range
of antihypertensive medications.
Initial and
renewal evaluations of HTN should include a thorough aeromedical summary and
documentation of review of the chart for past blood pressure readings. Table III outlines concerns that should be
considered and, where applicable, addressed in the waiver submission.
Table III.
History and physical guidelines for hypertension
waiver submission.
|
Initial Waiver |
Renewal Waiver |
|
History:
Physical examination:
Basic laboratory studies:
|
History:
Physical examination:
Basic laboratory studies:
|
Aeromedical
Disposition (military): The
aviator whose blood pressure is controlled by diet or exercise is no longer
considered to be hypertensive for surveillance purposes, and a waiver is not
required. However, any aviator initially
found to have a three-day blood pressure > 140/90 that responded to
life-style intervention should have blood pressure rechecks every three months
during the first year following discovery, and at least every six months
thereafter. Pharmacologic treatment
needs to be instituted if the blood pressure is still elevated after the
six-month period of observation. The
three classes of anti-hypertensive agents available to military aviators,
diuretics, ACEi agents and ARB agents are the
commonest and probably most useful drugs for blood pressure reduction. Use of beta-blockers is not recommended for
high performance aircraft due to its effect on heart rate. Centrally acting
medications are not presently permitted in military aviation, specifically,
methyldopa, reserpine, guanethidine, guanabenz and guanadrel.
Aeromedical
Disposition (civilian): Hypertension that requires treatment with
medications is the most common medical condition that the medical certification
division deals with. For the purpose of
the current examination of an airman, a blood pressure is considered elevated
if the blood pressure in the aviation medical examiner’s office is 155/95 or
greater. A “good” AME will repeat the BP
morning and evening and average for three days and average them. IF the results
average less than mentioned above, then the AME may issue a medical
certificate. Due to the size of the population the Federal Air Surgeon allows
Recertification of
civilian first and second-class airmen requires a yearly evaluation. The
evaluation is to include mention of any complications of hypertension, side
effects of medications, and serum potassium level if indicated. Third class
airmen are required to provide the same information as above but only with each
examination, i.e. every three years or as indicated by a special issuance.
Unlike military aviation, all currently available classes of medications are
permitted in civil aviation with the exception of several centrally acting
medications such as methyldopa, reserpine, guanethidine, guanabenz and
guanadrel. Use of beta-blockers is not recommended during aerobatic or
agricultural spraying flights due to its effect on heart rate during to
G-loading. A brand new medication in a new drug class, specifically a rennin
blocker called aliskiren or trade name Tekturna that was approved by the FDA in
March 2007 has not been accepted as a FAA medication.
Aeromedical
Disposition (NASA): Astronaut certification follows closely the military
experience. Well-controlled hypertension with no signs of end organ damage is
waiverable for all crew positions.
Waiver
Experience (military): Asymptomatic aviators with an average SBP ranging between 141 mmHg and
160 mmHg or an average DBP ranging between 91 mmHg and 100 mmHg who are without
evidence of end organ damage may remain on flying status for up to six months
(from the date the elevated blood pressure was first identified) while undergoing
non-pharmacological intervention to achieve acceptable values. Aviators with hypertension responsive to
life-style modifications should have serial BP rechecks quarterly to
semi-annually during the first year to assure continued lifestyle modifications. The rated or non-rated aviator with a history
of isolated HTN who remains normotensive using lifestyle modifications does not
require a waiver.
Failure to
achieve blood pressure control with lifestyle modifications, or initial blood
pressure average exceeding 160 mmHg systolic or 100 mmHg diastolic, requires
initiation of pharmacotherapy. After
clinical control of hypertension with stable medication(s) dosing (requiring a
minimum of 7 days after the last dosage adjustment, to allow cerebral autoregulation
to stabilize, and to document control), submit documentation for waiver
consideration.
Almost 90% of
military submitted for waiver for hypertension have received waivers (180 out
of 202 from May 2001 to present). An
unrestricted waiver is possible if adequate control of blood pressure
(three-day average < 140/90) and the absence of end-organ damage is
confirmed.
Waiver Experience (civilian): Hypertension with medication was the number one
pathology code listed for issued airmen and the most commonly used medication
in those airmen that have been issued a medical certificate in the FAA. As of 2007, there were 10,154 first-, 13,536
second-, and 40, 848 third-class airmen granted medical certification for
hypertension controlled with medication.
Waiver
Experience (NASA): Lisinopril is the most commonly used medication due
to the extensive experience in the military aviation community. Other
medications would be considered on an individual basis.
References:
1. Chobanian AV, et.al. The Seventh Report of the Joint National
Committee on Prevention, Detection, Evaluation, and Treatment of High Blood
Pressure: The JNC VII Express. National Heart, Lung, and Blood Institute. NIH. 2003:34 Retrieved 2 Feb 05,
http://www.nhlbi.nih.gov/guidelines/hypertension/jncintro.htm
2. DeHart
RL, Davis JR, eds.
Fundamentals of
Aerospace Medicine. 3rd Ed. Philadelphia: Lippincott Williams&Wilkins; 2002.
3. Hajjar I, Kotchen TA. Trends in prevalence,
awareness, treatment, and control of hypertension in the United States,
1988-2000. JAMA 2003; 290: 199.
4. Lewington S, Clarke R, Qizilbash
N, et al. Age-specific relevance of
usual blood pressure to vascular mortality: a meta-analysis of individual data
for one million adults in 61 prospective studies. Lancet 2002; 360: 1903.
5. Sytkowski PA, D'Agostino RB,
Belanger AJ, et al. Secular trends in long-term sustained hypertension,
long-term treatment and cardiovascular mortality. The
6. Turnbull
F. Effects of different blood-pressure-lowering regimens on major
cardiovascular events: results of prospectively-designed overviews of randomised trials.
Lancet
2003; 362: 1527.
Update:
January 19, 2008