Acute chest syndrome (sickle cell)

Acute Chest Syndrome

Atul Jindal (MD, DM)Assistant Professor

AIIMS, Raipur

OverviewDefinition

Pathophysiology

Clinical features

Challenges in the diagnosis of ACS

Course & Outcome

Monitoring & Investigations

Treatment of ACS

Chronic complications & Prevention

DefinitionAcute Chest Syndrome (ACS) is defined as an acute illness characterised by fever and/or respiratory symptoms, accompanied by a new pulmonary infiltrate on chest X-ray.

Pathophysiology

EtiologyPulmonary infection - identified in 38% who underwent extensive samplingSeasonal variation - 3 times more common in winterMore common in children<10 years - Viral infection (commonest RSV)Mycoplasma pneumonia (14%), Staph, pneumococcus, H.influenzae

EtiologyFat embolism Microvascular pulmonary infarctionHypoventilation/atelectasis - rib pain, opiate narcosis, post-operative periodAsthma

Clinical FeaturesSecond most common reason for hospitalisation Nearly half of patients present initially with a painful VOC ACS will often develop 24-72 hr after the onset of severe pain

Symptoms & Signs

Data from Vichinsky et al, 1997, 2000

Clinical signs often precede the CXR findings.

Sometimes Chest examination can be normal and hence it is important that the diagnosis is not excluded at this stage.

Challenges in the Diagnosis of ACS

Pulmonary embolism - CT angioFluid overload - Fluid balance chartOpiate narcosis - Monitoring of RR, sedation, and pain scoresAlveolar hypoventilation due to pain

Monitoring and Investigations

High Clinical suspicion + Clinical features = Straight forward diagnosisDiagnosis can be difficult

clinical features may be fewhypoxia is difficult to determine on clinical examination unless severeRadiological signs often lag behind the physical signs

Monitoring and Investigations

Standard monitoring includesAt-least 4 hrly SpO2 (on Air), HR, RR, BPDaily Clinical examinationCBC, CXR, Cr, LFT, Blood C/S, Bld group and cross match, ABG, Sputum C/S and PCR if facilities available

Investigations - CXR

Investigations - CBCAcute fall in Hb conc. or Platelet count are often seen

Decreasing platelet count to <2lac is an independent risk factor for neurological complications and the need for mechanical ventilation

Reticulocyte count - normal count excludes red cell aplasia by parvo B 19.

Investigations - Biochemical tests

RFT & LFT - MODS as a consequence of Systemic fat embolismCRP - monitor progressABG - on room air (if SpO2<94%)

Patients in clear resp. distress or in whom SpO2 falls rapidly to <85% when O2 is removed need escalation of therapy.PaO2 < 82 mm hg (70% of cases)

Investigations - other Investigations

CT - high sensitivity and specificity (84% and 97%)

High radiation dose - not recommendedUse in Pulm. EmbolismSecretory Phospholipase A2 (sPLA2) - levels elevated in ACS

ACS - TreatmentOxygen - titrate to SpO2>95% or within 3% of patient baseline valueIVF - Euvolemic (maintain I/O Chart)Pain relief - Adequate analgesia with frequent review and assessment of pain and sedation scores and cardiorespiratory monitoringIncentive Spirometry & Chest Physiotherapy Antimicrobials - treat for organisms for community acquired pneumonia + atypical organisms

ACS - Treatment

Blood Transfusion -

ACS - TreatmentRespiratory SupportBronchodilators -

Demonstrable reversible airway diseaseHistory s/o asthmaAcute bronchospasm

ACS - Treatment iNO - case reports , No RCT - insufficient evidenceCorticosteroids - Significant variability in their efficacy

Current evidence - mild to moderate ACS - not recommended due to its adverse effectsIf associated with Acute Asthma - Yes

ACS - Chronic complications

Scarring Pulmonary fibrosisChronic Sickle Lung DiseasePoor Lung Function

ACS - PreventionHydroxyurea - Significantly decrease the incidence of ACS in patients with recurrent severe pain and also in unselected children with HbSS.Long term transfusion - has been shown to decrease the incidence of ACS in patients who are being transfused for stroke prevention.Transfusion in preoperative period significantly reduces the incidence of post-operative ACS.Consider HSCT if both fails in preventing ACS episodes.

SCD - Wheeze or Asthma?

Asthma in SCD - 17%-48%

Challenge - Asthma or SCD?

Wheezing: common in SCD and independently associated with morbidity

Cooperative Study - out of 1722 ACS episodes - 11% were wheezing at admission and 26% ultimately had during the course.

SCD - Wheeze or Asthma?

Episode of wheezing producing shortness of breath is associated increased risk of future episode of ACS (IRR 1.7, p=0.04)

SCD - Wheeze or Asthma?

NHLBI guidelines

1) Assess for signs and symptoms of respiratory

problems by history and physical examination;

2) In patients with signs or symptoms of respiratory

problems, further assessment (including pulmonary

function testing) is recommended.

SCD - Wheeze or Asthma?

Knight-Madden and Greenough have termed “Recurrent Wheezing in

Sickle Cell Disease (RWIS)”.

Once we have a better understanding of the mechanisms underlying

airway abnormalities in SCD we can begin to explore the impact of

therapeutic interventions on recurrent wheezing, airway obstruction,

and/or asthma on short and long term SCD outcomes.

This is an important, understudied area that warrants further

investigation in an attempt to reduce morbidity and mortality in these

patients.