ANAESTHESIA FOR PATIENT WITH VSD UNDERGOING NON CARDIAC SURGERY

Dr. Adham A.monem Saleh, M.D.

Lecturer of Anesthesia, Intensive care, and Pain management.

Ain Shams university

Situation

A male child 5 years old, presented to the ED with acute appendicitis. He is a known case of unrepaired VSD. The decision of open appendectomy was made.

O/E: mild orthopnea, mild wheezes, pansystolic murmur, no cyanosis.

Preop. labs were within normal range, except for leukocytosis.

Echo: VSD with RVSP=70 mmHg, RV++.

VSD

Most common CHD (20-30%): 2.6 – 5.7 per 1000 live births.

Types:

I.

Subpulmonary (5 – 7 %) , ass. With aortic valve insufficiency II.

III.

IV.

Perimembranous (80% ) , ass with tricuspid valve abnormality AV canal (5 – 8 %) Muscular (5 – 20%)

ANATOMY

Pathophysiology  L→R shunt predominantly during systole. The septal defect is anatomically close to the RVOT such that the shunted blood bypasses the RV cavity. Hence RV hypertrophies sec to pul. HTN only.  Adaptive mechanisms include ↑Stroke volume, contractility, Heart rate & myocardial mass.

FEATURES OF VSD BASED ON SIZE

Small Med Shunt

L→R L→R

Large

L→R R→L

Gradient

High 20mmHg None

Large with ↑ PVR

R→L None

↑PVR

─ ± + +

RVP

N mild↑ ↑ ↑↑

RVH

No Mild Yes Yes

Natural History

   i.

- Spontaneous closure of defects <5mm before 2-5 years of age - Natural course depends on: ii.

iii.

Size of defect changes in PVR Changes in the above with age  Large defects lead to CHF in infancy (2- 6 weeks of life) Failure to thrive Recurrent Resp. tract infections Eisenmenger ’ s syndrome

Clinical features

Cardiomegaly Restrictive VSD: Pansystolic murmur Left sternal border radiating across the sternum Non restrictive VSD:Decrescendo murmur or absent murmur

ECG:

LVH

Echo:

LV enlarged , PA dilated RVH proportionate to degree of PHT

PREOP EVALUATION OF CHD PATIENT

1.

A.

B.

Review underlying anatomy & physiology of cardiac lesion Previous cardiac surgeries – palliative vs. reparative Evaluate existing residual or sequelae 2.

Assess other congenital anomalies 3.

A.

Review information from last cardiological examination Recent cardiac cath, echo B.

C.

Functional status Current medication 4.

i.

ii.

iii.

iv.

Assess risk factors Pulmonary HTN Cyanosis Arrhythmias Vent. dysfunction

6. Review proposed surgical procedure A.

B.

Elective vs. emergent Expected length & invasiveness 7. Plan treatment of potential complications A.

Dysrhythmias B.

C.

Pulmonary hypertension Ventricular dysfunction 8. Plan postop. care A.

Monitoring B.

Pain management C.

Cardiology follow up 9. Discuss anesthetic plan & risk with patient/parent

History:

  Infants:  Cyanosis   Respiratory difficulty Failure to thrive Children  Chronic cough   Cyanosis Poor feeding     Failure to thrive ↓ activity during exercise Fatigue Syncope

Examination:

Airway Cardiac Respiratory

Investigation:

CBC, Electrolytes ECG, CXR, ABG Echo, Cath.

Fasting Guidelines:

Avoid dehydration/hypovolemia

Premedication:

Benefits: Anxiolysis ↑cooperation ↓separation anxiety ↓cardiovascular liability Detrimental effects: Hypoventilation Hypotension Pain on administration

INFECTIVE ENDOCARDITIS

Congenital heart disease (CHD)

 Unrepaired cyanotic CHD, including palliative shunts and conduits  Completely repaired congenital heart defect with prosthetic material or device, whether placed by surgery or by catheter intervention, during the first 6 months after the procedure  Repaired CHD with residual defects at the site or adjacent to the site of a prosthetic patch or prosthetic device (which inhibit endothelialization)  History of IEC

OR Preparation:

Equipment Anesthesia machine check Prepare for invasive monitoring Set alarm limits appropriate for age & patient Emergency drugs Infusions & infusion pump Monitoring Pulse Oximetry NIBP ECG Capnography Urine Output, Temperature CVP IBP TEE

Anesthetic Goals

1.

2.

3.

4.

Bubble avoidance Optimizing O2 delivery & ventilatory function ↓ L→R shunt Avoid hypovolemia

Bubble Avoidance:

1.

2.

3.

4.

5.

6.

7.

Remove all bubbles from IV tubing Connect IV tubing to the venous cannula while there is free flow of fluid or blood Eject small amount of solution from syringe to clear air from needle to hub before injection Aspirate injection port of 3 way before injection to clear air Hold the syringe upright to keep bubbles at the plunger end Do not inject the last ml from the syringe Do not leave a central line open to air

Induction:

In L→R shunts with ↑ pulmonary blood flow, speed of inhalation induction is unchanged.

“We found more episodes of severe hypotension & an increased incidence of bradycardia and emergent drug use in the patients that received halothane than in patients who received sevoflurane” (Anesth Analg 2001;92:1152 – 8)

Intravenous:

Time to appear in systemic circulation is unchanged.

Thiopentone:↓ SVR, well tolerated in normovolemic, stable patients.

Propofol: Significant ↓ in SVR & MAP.

Ketamine: ↑ SVR, ↑ L→R shunt.

Etomidate: minimal cardiovascular effect.

HEMODYNAMIC GOALS

1.

2.

3.

Reduction of L→R shunt (avoid increased SVR) Slight increase in preload as hypovolemia is poorly tolerated (Why ??) If there is pulm. HTN, avoid factors that increase PVR ………………, and avoid decreased SVR…………

Hypovolemia is poorly tolerated in these patients, Why ?

The low resistance pulmonary circulation tends to

steal

volume from the high resistance systemic circulation. This is further increased by the systemic arterial vasoconstriction of hypovolemia.

Intraoperatively

 O 2 saturation starts to drop, what happened ???!!!

↑ PVR

PEEP High airway pressures Atelectasis Hypoxia Hypercarbia Acidosis ↑ HCT Drugs

↓ SVR

Anesth. agents Vasodilators Neuraxial blocks

Eisenmenger’s syndrome  ↑ PVR and Pulm HTN  of shunt  RVSP exceeds LVSP  reversal hypoxia, cyanosis……., worsened by drop in SVR.

 TTT: - Decrease PVR: hyperventilate with 100% O 2 , Pulm. Vasodilators (NO, Milrinone, Isoprenaline, Dobutamine, PGE1, Endothelin antagonist “Bosentan”) , treatment of the precipitating cause.

- Maintain SVR: systemic vasoconstrictors - Combination: Milrinone or Dobutamine /+ Norepinephrine infusion

CENTRAL NEURAXIAL BLOCKADE ??

Merit: ↓ SVR  ↓ L  R shunt.

Demerits: 1) IPPV allows hypervent & ↓ PVR 2) Vasodil due to sudden profound fall in SVR can reverse shunt

PREGNANCY & L→R SHUNTS

Modest L→R shunts are well tolerated during pregnancy Anaesthetic management should pay attention to: 1.

Care to avoid bubble infusion 2.

3.

LOR to saline rather than air during epidural catheterization Early administration of labor analgesia as pain ↑ SVR & catecholamine release worsening L→R shunt 4.

5.

Slow onset of epidural anaesthesia is preferred Monitoring of SpO2 & provision of supplementary O2