Hypertensive disorder accounts for 10-15% of pregnancy.
Pregnancy indused hypertension[PIH]-
- Preeclampsia and Eclamsia syndrome
- Chronic hypertension without protinuria
- Chronic HTN with superimposed preeclampsia / eclamsia
- Gestational HTN or transient HTN of third trimester
Preeclampsia and Eclamsia syndrome:
☛ Hypertension ,protinuria and generalized edema after 20 wks of gestation
☛ If superimposed by convulsion called eclampsia.
Chronic HTN :
☛ Present before 20 Wk and beyond 12 Wk
☛ When accomplished with preeclampsia called superimposed
☛ Occur late in third trimester or post partum.
☛ Comes back to normal within 2 wks of delivery.
☛ Not associated with proteinuria or generalized edema.
Exact etiology not known, It is a “disease of theories”.
☛ Abnormal placentation and failure of normal invasion of trophoblastic cells.
☛ Maladaptation of maternal spiral arteries.
☛ abnormal villous development and placental insufficiency.
☛ Imbalance of vasoconstrictor and vasodilatory substances.
☛ ↑ TxA2 and ↓PGE2, I2.
☛ The lowr resistance plasenta becomes high resistance due to inadequet trophoblastic invasion and maternal spiral artery remain tightly constricted.
Spiral artery of myometrium remain constricted
↓ 30% of uteroplacental flow
Placental trophoblastic relese mitogens and cause endothelial injury
Relese of “fibronectin”
Causes PG imbalance
↓PGE2 and ↑ Thromboxane
Fibronectin causes widespred endothelial damage and leads to –
- Placental insufficiency
- Coagulation abnormality
- Renal failure
- Placental aggargation
- loss of capillary integrity with leakage of fluids and proteins.
Almost all system are affected due to widespred vasoconstriction and endothelial damage-
1) Cardiovascular system [CVS]-
3 Sets of abnormalities can be presents
① High cardiac output, low to normal plasma volume, High SVR, low filling pressure
② Normal cardiac output,high SVR,loe filling pressure.
③ Highly elevated SVR , low blood volume, decresed left ventricular function.
Incresed blood pressure mainly because of ↑ CO rather than ↓ SVR especially in early course.
↓ plasma volume as much as 30%. Failure to increase plasma volume by 20-24 wks usually foretells Preeclampsia.
Red cell mass usually maintained.
☛ Hematocrit usually raised.
☛ ↓ in colloidal oncotic pressure due to ↓ plasma proteins.
☛ Salt and water retention.
☛ ↑ed circulating levels of Renin,Angiotensin, Catecholamine’s and ANF.
Pulmonary edema– vasoconstriction, endothelial damage, ↓ colloid oncotic pressure,↑ ed capillary leakage is responsible for leakage into extra vascular compartment and cause pulmonary edema.
Associated coagulation abnormalities:
☛ ↓ in platelet count- as much as ≤ 40,000
☛ Bleeding time is increased.
☛ Fibrin degradation product ↑ed.
- Hemolysis: characterized by abnormal peripheral blood smear, increased bilirubin levels.
- Elevated liver enzymes- ↑ed aspartate level ≥ 70IU/ L, LDH ≥600 U/L
- Low platelet count- ≤ 1LAC/MM3 CAN GO UPTO 25,000/MM3
Rate of fall of platelet count is more important, platelet generally return to normal after 72 hrs of delivery but can persist for longer period.
Patient c/o epigastric pain, nausea, vomiting, bleeding episodes, hematuria.
Treatment; whole blood, FFP, platelets, plasmapharesis, supportive treatment of liver and kidney.
In fulminant cases, delivery of fetus irrespective of gestation.
2) Respirtory system-
- Airway edema due to retention of water into tissues, ↓ed plasma oncotic pressure,↑ capillary pressure
- Potential airway compromise
- Increased incidence of failed ventilation and intubation
- Reduced volumes and capacities
- depression Mgso4 therapy,sedatives and anti- convulsant t/t is on.
- Shift of O2 dissociation curve to left due to ↑ed levels of COHB, due to destruction of RBC’S.
Pul. Edema- ↓edoncotic pressure,↑ endothelial damage, ↑ capillary permeability.
-Elevated liver enzymes
AST ≥ 70 U/L
LDH ≥ 600 U/L
– Generalised swelling and periportal haemorrhage causes epigastric pain, subcapsular haematoma.
☛ endothelial damage
☛ glomerular and tubular injury
☛ ↑ blood uric acid levels
☛ ↓ creatinine clearance,
☛ oligourea →ARF
☛ permanent glomerular sclerosis may need permanent dialysis therapy.
5) Central nervous system-[CNS]
☛ Hyperreflexia, CNS irritability
☛ intacranial haemorrhage
☛ focal thrombosis and hemorrhage
☛ visual disturbances, retinal hemorrhage
☛ occipital blindness
6) UTERUS AND PLACENTA–
☛ uterus become hyeperactive and sensitive to oxytocin
☛ may cause uterine atony
☛ decresed uteroplacental blood flow.
☛ premature labour
☛ fibrin deposits and multiple infarcts
7) FETAL MORBIDITY-
☛ Resp. distress,premature birth.
☛ Muconium aspiration
- Minimise vasospasm by t/t of antihypertensive, Mgso4 and improvement in circulation
- Improve intravascular volume
- Reduce CNS hyperactivity
- Correct acid base balance
- Correct electrolytes imbalance
- Early detection of coagulation,liver and kidney dysfunction.
- Hospitalization,eclampsia room,
- Bed restin left lateral position to improve uteroplacental circulation and avaoiding aortocaval compression
- Adequate water and sodium intake to avoid Na depletion and thereby i↑ rennin-angiotensin production
- Diuretics are routionly not recomonded unless there is pulmonary edema
- Control of seizures amd management of airway in eclamptic patient
- Mgso4 therapy and antihypertensives
Role of Anaesthetist→
- Intensive care management
- Control of airway
- Cardiac monitoring
- Support of ventilation
- Labour analgesia
- Elective/ emergency caesarian section
- Neonatal resuscitation
Uses- prophylactic therapy to prevent eclampsia and for treatment of eclampsia.
Mechanisum of action→
- Vasodilation- Non- sedative vadilatory action,improves cerebral,renal and utoro-placental circulation, mild anti- hypertensive action, reduces rennin and angiotensin activity. Attenuates vascular responses to presser substances.
- Tocolysis- ↓ uterine activity and improvesuterine blood flow
- Potent cerebral vasodilator- works better than other anticonvalsant.
- ↑ prostacycline relese by endotheline cells and by ↓ platelet aggregation.
- 4 gm i.v 20% solution bolous over 10 min followed by 10 gm 50% i.m, 5 gm in each buttock and 5gm every 4 hrly alternatively in each buttoks.
- 4gm iv over 10 min followed by iv infusion 1gm iv.
☛ Urine output ≥ 25 ml/hr
☛ Knee jerk +
☛ RR ≥ 12/MIN
☛ THERAPEUTIC LEVEL- 4-8 MEQ/L
☛ ECG changes- 5-10 ( wide qrs,prolonged PR )
☛ Loss of deep tendon reflex- 10 meq/l
☛ SA nodal and AV nodal block- 15 meq/l
☛ RESP. paralysis- ≥ 15
☛ Cardiac arrest – 25
- Muscle weekness – Due to decrese relese of Ach at motor nerve ending, ↑ed sensitivity to non- depolarizing muscle relaxant and there potentiation.
- Respiratory insufficiency-
- Neonatal effects- mg readialy crosses placenta,low apgar score, decresed muscle tone,resp depression/Apnea.
Anti- hypertensive agent:
☛ Hydralazine: 5-10mg i.v,slow onset 20-30 min. Duration- 2-3 hrs, causes fetal distress.
☛ Alpha- methyl dopa: 250 mg qid/tds
LABETOLOL → Start 20 mg i.v upto 1-3 mg/kg, onset 1-2 min,duration- 2-3 hr. increases uterine and placental blood flow.
NIFEDIPINE → 5-10 MG SUBLINGUAL/ORAL
Maternal sequalae of HTN:
CVA,HELLP, Convulsion, Occipital blindness, pul. Edema, Renal failure.
Check list before instituting epidural block/spinal anesthesia :
- Working large bore i.v line
- NBM status
- Coagulation profile should be normal.
- Control of hypertension
- Hydration status
- Urine output in 24 hrs
- Last dose of Mgso4/ antihypertensive
- Airway examination.
- Aspiration prophylaxis
- Probe oximeter and o2 supplimentaion
- Left lateral tilt
Recommended techniques of general anaesthesia for caeserian section:
- Aspiration prophylaxsis– H2 blocker,Non- particulate antacids,Metoclopramide
- Routine monitoring – ECG,SpO2,EtCO2,nibp,SUCTION EQUIPMENT,Aids for difficult intubation should be kept ready, NM Monitoring, Antihypertensive and inotrops should be available.
- Left lateral displacement of uterus.
- Preoxygenation with 100% O2 for 3-5 min
- Cricoids pressure after induction
- Give drug to blunt pressure response
- Facilitation of intubation with succhynylcholine and maintain cricoids pressure till ET T ube cuff is inflated.
- Ventilate with 50% o2 + 50% N2O and volatile anesthetic as necessary
- Maintain normocarbia and use of muscle relaxation as necessary vec/atracurium.
- Neuromuscular monitoring if patient of Mgso4
- After delivery,↑ N2o to 70% discontinue or reduce volatile anesthetic.
- Administer BZP and opioids ,oxytocin to drip
- Insert nasogastric tube before sx.
- Reverse neuromuscular blockeds after reflexes +.
- Extubate the patient awake,obeying commands with after adequate reversal of NM blocking agents. Dr.Nagesh