Hypertension

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Hypertension

Definition & Classification

Hypertension is a sustained elevation of arterial blood pressure. Classification follows the 2017 ACC/AHA guidelines:

Category	Systolic (mm Hg)		Diastolic (mm Hg)
Normal	< 120	and	< 80
Elevated	120–129	and	< 80
Stage 1 HTN	130–139	or	80–89
Stage 2 HTN	≥ 140	or	≥ 90
Hypertensive crisis	≥ 180	and/or	≥ 120

A hypertensive emergency is defined as severe BP elevation (typically ≥ 180/110 mm Hg) with new or worsening pressure-related end-organ injury (encephalopathy, ACS, aortic dissection, acute kidney injury, etc.).

— Goldman-Cecil Medicine, p. 743

Types

Primary (Essential) Hypertension (~85–90% of cases) No single reversible cause can be identified. The primary vascular abnormality is elevated systemic vascular resistance.

Secondary Hypertension (~10–15% of cases) A specific, often treatable cause can be found. Key causes include:

Renal artery stenosis (atherosclerotic or fibromuscular dysplasia)
Primary aldosteronism
Pheochromocytoma / paraganglioma
Cushing syndrome
Coarctation of the aorta
Obstructive sleep apnea
Hypothyroidism / hyperthyroidism
Drug-induced (cocaine, methamphetamine, NSAIDs, OCPs)

— Goldman-Cecil Medicine, p. 744; Katzung's Basic & Clinical Pharmacology, p. 269

Pathophysiology

Blood pressure follows the hydraulic equation:

BP = Cardiac Output (CO) × Peripheral Vascular Resistance (PVR)

Physiologically, BP is regulated at four anatomic sites: arterioles, postcapillary venules, heart, and kidney.

Key regulatory mechanisms include:

Baroreflexes — carotid and aortic baroreceptors inhibit central sympathetic discharge when pressure rises; disruption leads to labile hypertension
RAAS — reduced renal perfusion activates renin → angiotensin II → vasoconstriction + aldosterone secretion → sodium/water retention → ↑ blood volume
Renal pressure-natriuresis — in hypertension, this system is "reset" at a higher pressure level
Sympathetic nervous system — augmented SNS activity, especially in obesity, raises cardiac output and PVR
Nitric oxide/endothelin balance — endothelial dysfunction reduces vasodilatory NO and increases vasoconstrictive endothelin-1

Contributors to essential hypertension:

Obesity (especially visceral fat): activates SNS, RAAS, induces insulin resistance, compresses renal medulla
High dietary sodium / low potassium
Heavy alcohol use (≥ 3 drinks/day)
Genetic factors (heritability ~30%): polygenic, with variants in angiotensinogen, ACE, AT₁ receptor, β₂-adrenoceptor, α-adducin, uromodulin genes; rare mendelian forms include Liddle syndrome (ENaC gain-of-function), Gordon syndrome, apparent mineralocorticoid excess

— Goldman-Cecil Medicine, pp. 743–744; Katzung's, pp. 269–270

Clinical Presentation

Hypertension is largely asymptomatic ("silent killer"). When symptoms occur, they are usually due to target organ damage, not elevated BP itself.

Signs on examination:

Hypertensive retinopathy — earliest sign (arteriolar narrowing, AV nicking, flame hemorrhages, papilledema in severe cases)
Cardiac enlargement (LVH) on ECG/CXR
Elevated creatinine

Symptoms suggesting secondary causes:

Paroxysmal headache, sweating, palpitations → pheochromocytoma
Snoring, daytime somnolence → obstructive sleep apnea
Muscle weakness, hypokalemia → primary aldosteronism
Weak femoral pulses, lower-extremity BP < upper → coarctation of aorta

— Goldman-Cecil Medicine, pp. 743–744

Diagnosis

Three goals at initial evaluation:

Accurate BP measurement — should be confirmed outside the office (home BP monitoring or ambulatory BP monitoring). White-coat hypertension (elevated only in office) and masked hypertension (normal in office, elevated outside) must be differentiated.
Cardiovascular risk factor assessment — dyslipidemia, diabetes, smoking, family history, CKD
Screen for secondary hypertension in selected patients (young age, resistant HTN, sudden onset, unprovoked hypokalemia, abdominal bruit, etc.)

Baseline investigations:

Urinalysis, urine albumin-to-creatinine ratio
Serum electrolytes (Na, K), creatinine/eGFR
Fasting glucose, HbA1c
Fasting lipid panel
ECG (LVH, ischemia)
Thyroid function

— Goldman-Cecil Medicine, p. 743

Target Organ Damage & Complications

Organ	Manifestation
Brain	Stroke (ischemic > hemorrhagic), hypertensive encephalopathy, vascular dementia
Heart	LVH, coronary artery disease, heart failure (HFpEF and HFrEF)
Kidney	Hypertensive nephrosclerosis, CKD, proteinuria
Eyes	Hypertensive retinopathy, risk of retinal vein/artery occlusion
Vasculature	Aortic dissection, peripheral arterial disease, aneurysm

Hypertension carries a 2.5× (men) to 3.9× (women) age-adjusted risk for peripheral arterial disease and substantially increases stroke and MI risk. — Textbook of Family Medicine 9e

Treatment

Lifestyle Modifications (for all stages)

Dietary sodium restriction (< 2.3 g/day; in resistant HTN, reduces BP as much as a single drug)
Weight loss (each kg ↓ reduces systolic BP ~1 mm Hg)
DASH diet (rich in fruits, vegetables, low-fat dairy, low sodium)
Regular aerobic exercise
Limit alcohol to ≤ 2 drinks/day (men), ≤ 1 (women)
Smoking cessation (reduces overall cardiovascular risk)

Pharmacotherapy

All antihypertensive drugs act at one or more of the four anatomic control sites (arterioles, venules, heart, kidney) to reduce CO and/or PVR.

First-line drug classes:

Class	Examples	Key Notes
Thiazide/thiazide-like diuretics	Chlorthalidone, HCTZ, indapamide	Preferred for most; chlorthalidone preferred over HCTZ
ACE inhibitors	Lisinopril, ramipril, enalapril	Preferred in diabetes, CKD, HF; avoid in pregnancy
ARBs	Losartan, valsartan, irbesartan	Preferred when ACE inhibitors not tolerated (cough)
Calcium channel blockers (CCBs)	Amlodipine (dihydropyridine), diltiazem/verapamil (non-DHP)	Preferred in isolated systolic HTN, elderly
Beta-blockers	Metoprolol, carvedilol, atenolol	Preferred in CAD, HFrEF, post-MI

Other agents:

RAAS inhibitors: The renin-angiotensin-aldosterone system contributes to ~40% of essential hypertension cases (20% with high renin, 20% with low renin). ACE inhibitors and ARBs are first-line in diabetic nephropathy and proteinuric CKD. — Katzung's, p. 269
Aldosterone antagonists (spironolactone, eplerenone): Effective in primary aldosteronism and resistant hypertension
Vasodilators (hydralazine, minoxidil): Reserved for severe or resistant hypertension; hydralazine causes reflex tachycardia and at doses ≥ 400 mg/day carries a 10–20% risk of lupus-like syndrome in slow acetylators
Centrally acting agents (clonidine, methyldopa): Methyldopa is safe in pregnancy

Resistant hypertension — BP uncontrolled despite 3 drugs (including a diuretic) at optimal doses. Consider renal denervation, screening for secondary causes, and sodium restriction.

BP Targets

General population: < 130/80 mm Hg (ACC/AHA 2017)
CKD with proteinuria: < 130/80 mm Hg
Elderly (≥ 65 years): < 130 systolic if tolerated

Hypertensive Emergency vs. Urgency

	Emergency	Urgency
BP	≥ 180/120 mm Hg	≥ 180/120 mm Hg
End-organ damage	Present	Absent
Treatment	IV agents (labetalol, nicardipine, nitroprusside); reduce MAP by ≤ 25% in first hour	Oral agents; gradual reduction over 24–48 h

Common emergencies: hypertensive encephalopathy, hemorrhagic stroke, acute MI, aortic dissection, acute pulmonary edema, eclampsia, acute kidney injury.

Sources:

Goldman-Cecil Medicine, International Edition, pp. 743–749
Katzung's Basic and Clinical Pharmacology, 16th Edition, pp. 269–280
Textbook of Family Medicine, 9th Edition

Tramadol for labour pain

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Tramadol for Labour Pain

Background: Pain of Labour

Labour pain is among the most intense pain experiences encountered clinically. It has two distinct phases:

First stage (uterine contractions + cervical dilation): Visceral pain carried by C fibres alongside sympathetic nerves, referred to the T10–L1 dermatomes (lower abdomen, then lumbosacral region and thighs as labour progresses)
Second stage (perineal distension + fetal descent): Somatic pain via the pudendal nerve (S2–4), involving T10–S4 dermatomes

Pain intensity is influenced by parity, fetal size and presentation, maternal anxiety, labour augmentation, and genetic factors.

— Morgan and Mikhail's Clinical Anesthesiology, 7e; Miller's Anesthesia, 10e

Tramadol: Mechanism of Action

Tramadol is an atypical centrally acting analgesic with a dual mechanism:

Weak μ-opioid receptor agonism (and minor κ/δ activity) — via its active metabolite O-desmethyltramadol (M1)
Monoamine reuptake inhibition — inhibits neuronal reuptake of serotonin and norepinephrine, enhancing descending inhibitory pain pathways

This dual action means tramadol provides analgesia at lower opioid receptor occupancy than pure opioids, theoretically reducing — though not eliminating — opioid-related side effects.

Use in Labour

Tramadol is used as a systemic analgesic during labour, predominantly in settings where neuraxial (epidural/spinal) analgesia is unavailable, refused, or contraindicated. It is widely used in low- and middle-income countries as a cost-effective alternative.

Route and Dosage

Intramuscular (IM): 100 mg — most common route in labour; can be repeated after 4 hours (max ~400 mg/24h)
Intravenous (IV): 50–100 mg, slower administration to reduce side effects
Patient-controlled analgesia (PCA): IV tramadol PCA has been studied as a labour analgesic in settings where epidural analgesia is not available

Efficacy

Tramadol provides moderate analgesia for labour pain. Comparative studies generally show:

Superior to placebo
Comparable to or slightly better than pethidine (meperidine) for pain scores in some trials
Inferior to epidural analgesia — epidural remains the gold standard for labour pain relief
Less effective than remifentanil PCA
Onset: ~15–30 minutes (IM); ~5–10 minutes (IV)
Duration: ~4–6 hours (IM)

Maternal Side Effects

Side Effect	Notes
Nausea and vomiting	Most common (~20–40%); more frequent than with pethidine in some studies
Sedation / dizziness	Dose-related; generally milder than morphine
Respiratory depression	Less than with traditional opioids due to ceiling effect on opioid receptor binding
Serotonin syndrome	Risk if combined with SSRIs, MAOIs, other serotonergic drugs
Seizures	Threshold lowering — caution in patients with history of seizures or pre-eclampsia/eclampsia
Pruritus	Less common than with neuraxial morphine or pethidine

Placental Transfer and Neonatal Effects

All opioids cross the placenta — tramadol is no exception. This is the most clinically significant concern with its use in labour.

Key neonatal considerations:

Placental transfer is rapid and significant: Umbilical vein/maternal vein ratio approaches 0.9–1.0, indicating near-complete transfer
Neonatal respiratory depression: The active metabolite M1 accumulates in the neonate due to immature hepatic CYP2D6 metabolism and prolonged neonatal half-life
Reduced Apgar scores: Reported in some studies, particularly with larger doses or delivery close to time of administration
Decreased FHR (fetal heart rate) variability: A class effect of all CNS depressants; complicates interpretation of cardiotocography (CTG)
Prolonged time to sustained respiration: Risk increases when delivery occurs within 1–4 hours of administration
Neonatal abstinence syndrome: With repeated or high doses

The neonatal effects are considered less severe than pethidine (which has the additional problem of normeperidine accumulation — a neuroexcitatory metabolite with a half-life of 13–23 hours, up to 3× longer in the neonate). However, tramadol is not free of neonatal risk.

Naloxone should be immediately available to reverse neonatal respiratory depression.

— Miller's Anesthesia, 10e, p. 8844; Morgan and Mikhail's Clinical Anesthesiology, 7e, p. 1608

Tramadol vs. Other Systemic Opioids in Labour

Drug	Key Feature	Neonatal Concern
Pethidine (meperidine)	Historically most used; now mostly abandoned	Normeperidine neurotoxic metabolite; ↑ neonatal depression, low Apgar
Morphine	Significant sedation; used for latent-phase rest	Active metabolite M6G; significant neonatal depression
Fentanyl IV/PCA	Rapid onset (2–4 min), no active metabolites, short duration	Neonatal effects generally less than pethidine at standard doses
Remifentanil PCA	Shortest acting; best systemic option; rapidly metabolised by fetal/neonatal plasma esterases	Maternal respiratory depression/apnoea risk; requires 1:1 monitoring
Nalbuphine / Butorphanol	Mixed agonist-antagonists; ceiling on respiratory depression	Generally well tolerated
Tramadol	Moderate efficacy; dual mechanism; less neonatal depression than pethidine	Crosses placenta readily; M1 accumulates in neonate

Contraindications and Cautions

Seizure disorders / eclampsia — tramadol lowers seizure threshold; avoid or use with great caution
Concurrent serotonergic drugs (SSRIs, MAOIs, linezolid, triptans) — risk of serotonin syndrome
CYP2D6 ultra-rapid metabolisers — excessive M1 production → exaggerated opioid effect in both mother and neonate (relevant with breastfeeding post-delivery)
Hepatic or renal impairment — reduced clearance; dose reduction needed
Concurrent CNS depressants — additive respiratory depression

Practical Position

In clinical practice:

Neuraxial analgesia (epidural/CSE) remains the most effective method for labour pain and should be offered to all women who request it. It also has physiological benefits: blunting sympathetic surges reduces maternal tachycardia and hypertension, avoids hyperventilation-induced fetal hypoxia, and can convert dysfunctional labour patterns.
Tramadol is a reasonable second-line systemic option in settings where neuraxial analgesia is unavailable or declined, offering moderate pain relief with a more favourable neonatal profile than pethidine.
Remifentanil PCA is the preferred systemic opioid where available, but requires 1:1 nursing monitoring for maternal apnoea.
Timing matters: administer systemic opioids early in labour to maximise the interval between administration and delivery, reducing neonatal exposure.
Neonatal resuscitation equipment and naloxone must always be immediately available when any systemic opioid is used in labour.

— Miller's Anesthesia, 10e, pp. 8843–8845; Barash's Clinical Anesthesia, 9e, pp. 3486–3487; Morgan & Mikhail's Clinical Anesthesiology, 7e, pp. 1607–1608

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