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

  • Stage 1
  • Stage 2

 

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:

  • Diet, especially, alcohol and sodium intake
  • Botanicals/supplements
  • Cigarette smoking/tobacco use
  • Physical inactivity
  • Dyslipidemia
  • Diabetes mellitus
  • Sleep apnea (snoring, observed apneas)
  • Family history of premature cardiovascular disease
  • Symptoms: flushing, headaches, nocturia, chest pain, claudication. 

Physical examination:

  • Weight (BMI)
  • Hypertensive retinal changes
  • Thyroid
  • Auscultation for carotid, abdominal, and femoral bruits
  • Heart and lungs
  • Abdominal exam for enlarged kidneys, masses, and abnormal aortic pulsation
  • Lower extremity exam for edema  & pulses
  • Neurological assessment

Basic laboratory studies:

  • Hematocrit/hemoglobin
  • Fasting glucose
  • Lipid profile
  • Serum electrolytes
  • Serum calcium
  • Blood urea nitrogen
  • Serum creatinine
  • Urinalysis
  • Resting electrocardiogram (ECG)
  • Thyroid stimulating hormone (TSH)

 

History:

  • Symptoms related to coronary artery disease or medications
  • Diet (e.g., alcohol and sodium intake) and supplements
  • Cigarette smoking/tobacco use
  • Physical inactivity
  • Other medical conditions since last waiver granted

Physical examination:

  • Blood pressure readings over the course of the previous waiver
  • Weight changes
  • Hypertensive retinal changes
  • Auscultation for carotid, abdominal, and femoral bruits
  • Heart and lungs
  • Abdominal exam for enlarged kidneys, masses, and abnormal aortic pulsation
  • Lower extremity exam for edema  & pulses
  • Neurological assessment

Basic laboratory studies:

  • Serum electrolytes (if on HCTZ)

 

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 AMEs to issue an unrestricted medical certificate.  For an Initial medical certificate the airman has to provide a status report that mentions family history, medications and whether the airman is at increased risk of heart disease. They are also to provide lab testing to include lipid panel and fasting blood sugar. On this initial examination, the AME must obtain an Electrocardiogram. 

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

Framingham Heart Study 1950 to 1990.  Circulation 1996; 93:  697.

 

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