How do you deal with anaesthesia in a child with a murmur?
In a review on anaesthesia-related cardiac arrest in children, Linda Mason states that murmurs should be characterised before anaesthesia, especially in infants. (1) It is accepted that auscultation skills are on the wane as new diagnostic modalities emerge. (2) However, it is impossible to refer every murmur heard for special investigation, since about 50-72% of paediatric murmurs are normal or innocent. (3,4) With a wide description of incidence of innocent murmurs (depending on the experience of the examiner and examining conditions) and a very low incidence (0.5%) of cardiac disease in children, it is difficult to confidently make a decision. (5) Some important considerations are given in Table I.
Innocent and pathological murmurs
The characteristics of innocent and pathological murmurs are given in Tables II and III. The difficulty is that there is overlap in the findings with an innocent or pathological murmur. Coleman et al. (6) studied a cohort of 444 children with innocent murmurs (21% of the total number investigated). Innocent murmurs were defined as those murmurs with no cardiac lesion (83%), or with a minor lesion (17%). The minor lesions were atrial septal defect (ASD), small ventricular septal defect (VSD), mild pulmonary stenosis or regurgitation, and patent ductus arteriosus (PDA). Coleman found that a clinical diagnosis of VSD was as often disproved as confirmed and that the clinical diagnosis of ASD was seldom confirmed. Mild pulmonary stenosis was rarely clinically diagnosed but frequently discovered on cardiac catheterisation. Two of their patients developed bacterial endocarditis (with a small VSD and insignificant pulmonary stenosis). It is therefore clear that although lesions may be haemodynamically insignificant, there are other consequences. The intensity of small VSD murmurs may vary from 2/6 to 6/6 and can be early systolic rather than pansystolic. (8)
Any murmur detected preoperatively should be evaluated to determine whether it is innocuous. In the vast majority of cases this should be determined by clinical means (although it is not foolproof). This evaluation can be done by a general practitioner or a specialist anaesthetist. Referrals could be to a paediatrician or a paediatric cardiologist.
Clinical evaluation of murmurs in children (7,9)
The clinical evaluation should start with historical features that may suggest that the murmur is pathological. For example prematurity, other congenital malformations, feeding intolerance, failure to thrive, respiratory symptoms, particularly repeated infections, cyanosis, chest pain, syncope, or a family history of sudden death are all worrying. Table IV shows the questions to ask. Examination should be in a quiet room, the patient preferably lying down. Sitting in the mother's lap can help pacify the child.
If palpation indicates increased precordial activity, an ASD, moderate to large VSD significant PDA may be present. A thrill may be felt at the lower left sternal border (VSD), left upper sternal border (pulmonary valve stenosis) or suprasternal notch (aortic stenosis). Both brachial and femoral pulses bilaterally should be equal in timing and intensity and blood pressure in the right arm normal, to exclude aortic coarctation.
The first heart sound ([S.sub.1]) is normally single sound caused by closure of the mitral (MV) and tricuspid (TV) valves. If S1 inaudible, some other sound is obscuring (think VSD, AV regurgitation, PDA, severe pulmonary stenosis). The murmurs that cause this effect are often called holosystolic. If S1 appears split it is either caused by a click or by asynchronous closure of the MV and TV. Pulmonary valve (PV) ejection clicks begin shortly after AV valve closure, vary with respiration and are best heard at the upper left sternal border. Aortic valve clicks begin shortly after S1 and are loudest at the apex. Mitral valve clicks are best heard at the apex when standing.
The second heart sound ([S.sub.2]) is caused by closure of the aortic and pulmonary valve, and has two components, the aortic second sound ([A.sub.2]) and the pulmonary second sound ([P.sub.2]). The sound splits during inspiration as more blood is drawn into the right ventricle and subsequently the PV closes later. A loud, single [S.sub.2] indicates pulmonary hypertension (with RV overload) or congenital heart disease involving the semilunar valves. Murmurs are graded 1-6/6, and are timed as early, middle or late systolic. The 'character' of the murmur may help with diagnosis. A 'harsh' murmur occurs when blood flows at high velocity from a high- to a low-pressure chamber. Examples are VSD and semilunar valve stenosis. 'Whooping' or 'blowing' sounds occur at the apex with mitral regurgitation, and a crescendodecrescendo 'flow murmur' describes the innocuous functional murmur. However, similar murmurs may also be heard with ASD, mild semilunar valve stenosis, subaortic obstruction, aortic coarctation, and very large VSD.
Most pathological murmurs do not change in intensity during position changes, the most important exception being the murmur of hypertrophic cardiomyopathy (HOCM) (Table III). The venous hum is heard all over the anterior chest and is present if the child is upright and disappears when he lies down or with pressure over the jugular vein. The position of highest intensity of murmurs varies with lesions (Table V).
The ASD is most frequently incorrectly diagnosed. A differentiation between a functional murmur and ASD is given in Table VI.
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Which children with murmurs can then be anaesthetised, and which would have to be further investigated? McEwan et al. suggested a logical sequence that it is useful to follow. (5) A modified version of this is given in Fig. 1. Most murmurs will be innocent and one can proceed to anaesthesia. Without corroborating history, the most dangerous lesions that must be excluded are HOCM and aortic stenosis. Both lesions may be asymptomatic with only the murmur, but may cause fatal haemodynamic derangement during anaesthesia. In both conditions the ECG usually shows left ventricular hypertrophy and left axis deviation. Be wary of any child with an R wave in V5 or V6 that is greater than 40mV. Refer such ECGs for evaluation. Other dangerous lesions such as significant pulmonary stenosis, tetralogy of Fallot or coarctation of the aorta will usually have typical symptoms, signs and ECG abnormalities. (5)
Although 'insignificant' lesions such as ASD, small VSD or pulmonary stenosis may be of no haemodynamic importance, there is the possibility of endocarditis. Surgery that may cause a bacterial surge must be covered by antibiotics (dentectomy, oral surgery, upper respiratory tract surgery, genitourinary instrumentation or surgery, and gastrointestinal procedures). The perioperative guidelines for antimicrobial therapy were recently upgraded and a summary is shown in Table VII. (10) The risk of dental procedures has been shown to be smaller than previously thought, and prophylaxis is only necessary when there is manipulation of gingival tissue or the periapical region of teeth or perforation of the oral mucosa. Prophylaxis is also only necessary in certain 'at-risk' cardiac conditions (Table VII). (10)
Most children with heart murmurs will have an insignificant murmur that is unlikely to cause haemodynamic problems during anaesthesia. However, every murmur must be thoroughly evaluated clinically and if there is uncertainty about the innocuous nature of the murmurs according to the suggested algorithm, the surgery should be postponed. Otherwise anaesthesia can be administered with appropriate antibiotic prophylaxis. The child should be referred postoperatively for evaluation and follow-up since some seemingly insignificant murmurs may over years be unmasked as specific pathology.
In a nutshell
* Cardiac murmurs in children may have serious haemodynamic implications during anaesthesia and surgery.
* Innocuous and pathological murmurs have characteristics that differ, but there is unfortunately also overlap.
* Most murmurs (>70%) are innocuous and anaesthesia can be safely administered.
* It is essential to investigate any murmur detected preoperatively to exclude dangerous murmurs.
* An appropriate history and thorough clinical examination will enable diagnosis of most innocuous murmurs.
* For some cardiac lesions perioperative antimicrobial prophylaxis is necessary for some procedures.
* Patients should be referred for postoperative evaluation and follow-up.
* Patients and parents should be informed of the implications and need for prophylaxis and follow-up.
(1.) Mason LM. An update on the etiology and prevention of anaesthesia-related cardiac arrest in children. Paediatr Anaesth 2004; 14: 412416.
(2.) Pelech AN. The cardiac murmur. When to refer? Pediatr Clin North Am 1998; 45: 107-122.
(3.) Hurrell DG, Bachman JW, Feldt RH. How to evaluate murmurs in children. Postgrad Med 1989; 86: 239-241.
(4.) McLaren, MJ Lachman AS, Pocock WA, et al. Innocent murmurs and third heart sounds in black schoolchildren. Brt Heart J 1980; 43: 6773.
(5.) McEwan AI, Birch M, Bingham R. The preoperative management of the child with a heart murmur. Paediatr Anaesth 1995; 5: 151156.
(6.) Coleman EN, Doig WB. Diagnostic problems with innocent murmurs in children. Lancet 1970; ii: 228-232.
(7.) McConnell ME, Adkins SB, Hannon DW. Heart murmurs in paediatric patients: When do you refer? Am Fam Physician 1999; 60: 558-565.
(8.) Van der Hauwart L, Nadas AS. Auscultary findings in patients with small ventricular septal defect. Circulation 1961; 23: 886-891.
(9.) Prevention of infective endocarditis. Guidelines from the American Heart Association. A guideline from the American Heart Association rheumatic fever, endocarditis, Kawasaki disease Committee, Cardiovascular disease in the young, and the Council on clinical cardiology, Council on cardiovascular surgery and anaesthesia, and the Quality of care and outcomes research interdisciplinary working group. Wilson W, Taubert KA, Gewitz M, et al. Circulation 2007; 115:&NA; downloaded from circ.ahajournals.org, ISSN: 1524-4539
(10.) Von Ungern-Sternberg BS, Habre W. Pediatric anesthesia--potential risks and their assessment: part I. Paediatr Anaesth 2006; 17: 206-215.
JOHAN DIEDERICKS, MMed (Anes), FCA (SA), BA Professor and Head, Department of Anaesthesiology, University of the Free State, Bloemfontein
Johan Diedericks has a clinical interest in paediatric anaesthesia, particularly paediatric cardiothoracic anaesthesia, and a research interest in cardiac function in anaesthesia.
Table I. Considerations of a murmur discovered at preoperative visit * Is it dangerous? May it cause haemodynamic instability intraoperatively? * In some lesions (e.g. ASD or VSD) paradoxical embolism and a reversion to a fetal-type circulation may occur during anaesthesia (transitional circulation) * * Is antibiotic prophylaxis indicated; what drug and what dose? * Should the case be postponed and the murmur investigated (expensive)? * Should surgery continue with later follow up? * Could it be ignored? * Patient and parent information and reassurance and continuity of follow-up ** Hypoxia, hypercarbia, acidosis, hypotension, hypothermia, painful stimulation are precipitants. Pulmonary hypertension increases this risk. ASD = atrial septal defect. VSD = ventricular septal defect. Table II. Characteristics of innocent murmurs (5-7) * Early systolic or continuous * Soft (3/6 or less) * Crescendo-decrescendo * Examples: * Still's murmur--most common, 'musical or vibratory, groaning, squeaking, creaking, rasping', 1-3/6, no thrill, inside apex or low parasternal, but may be over whole precordium, softer or disappear on standing, reappears on squatting * Pulmonary ejection murmur--systolic, high-pitched 'blowing', second left interspace, may be heard at the apex, left sternal border, aortic area and neck, normal split-second heart sound during inspiration (not expiration) * Supraclavicular arterial bruit (rare) * Late systolic cardiorespiratory murmur (rare) * Continuous murmur (venous hum)--systolic and diastolic hum, loudest in sitting during inspiration, disappears or diminishes in the supine position or with pressure over the supraclavicular area due to reduced jugular venous flow Table III. Characteristics of pathological murmurs (5-7) * Diastolic, pansystolic or late systolic * Usually loud (3/6 or more) * Associated with a thrill * Symptoms or signs of cardiac disease * Continuous * S1 inaudible or not single * Most do not change significantly on standing (the systolic murmur of the rare, but dangerous, hypertophic obstructive cardiomyopathy increases on standing) (7) * Examples: All murmurs caused by cardiac lesions. Some people classify ASD, small VSD, mild pulmonary stenosis or regurgitation, and PDA as innocent murmurs. Although these lesions may be haemodynamically innocent during anaesthesia, children may develop bacterial endocarditis (6) Table IV. Questions to determine the clinical effect of a murmur (9) Children * Does he/she run? Like peers? * Is he/she calmer or slower than peers? Cyanosis * Does he/she turn blue? During feeding/when crying? * Does he/she lose consciousness? * Does he/she stop playing and squat? Infant * Is feeding prolonged? * Does he/she sweat during normal care? * Does he/she have swollen eyes in the morning? Table V. Areas of highest intensity for common paediatric murmurs (7) Area Murmur Upper right sternal border Aortic stenosis, venous hum Upper left sternal border Pulmonary stenosis, pulmonary flow murmurs, ASD, PDA Lower left sternal border Still's murmur, VSD, tricuspid regurgitation, HOCM, subaortic stenosis Apex Mitral regurgitation Table VI. Differentiation between an ASD and innocent murmur (1) Physical sign Innocent murmur ASD Precordial activity Normal Increased [S.sub.1] Normal Normal [S.sub.2] Splits, moves with respiration Fixed widely split Systolic murmur Crescendo- Crescendo- (supine) decrescendo decrescendo Possible vibration lower left sternal border 'Flow' at upper sternal border Systolic murmur Decrease in Does not change (standing) intensity Diastolic murmur Venous hum Inflow 'rumble' across tricuspid valve area Table VII. Cardiac lesions at risk of endocarditis and the surgical procedures that require prophylaxis. Regimens according to the American Heart Association (9,10) At-risk cardiac Operative procedures Bacterial prophylaxis lesions requiring prophylaxis suggested for children * Prosthetic valves Prophylaxis for Single dose 30-60 dental procedures minutes before * Previous infective that involve: procedure: endocarditis * Manipulation of Oral or unable to * Congenital heart gingival tissue take oral disease (CHD): medication: * Manipulation of the * Unrepaired periapical region * Amoxilhn 50 mg/kg cyanotic CHD, of teeth po including palliative shunts * Perforation of the * Ampicillin 50 and conduits oral mucosa mg/kg or cefazolin or ceftriaxone IV No prophylaxis for: or IM * Repaired congenital heart * Injections of local Allergic to defects with anaesthesia in penicillins or prosthetic material non-infected tissue ampicillin--oral: within 6 months of surgery (not yet * Dental radiographs * Cephalexin 50 epithelialised) mg/kg PO or * Repaired CHD with * Placement or * Chndamycin 20 residual defects adjustment of mg/kg PO or removable * Cardiac prosthodontic or * Azithromycin or transplants with orthodontic clarithromycin 15 valvular disease appliances mg/kg PO * Placement of Allergic as above, orthodontic unable to take oral brackets medication: * Shedding of * Cefazolin or deciduous teeth ceftriaxone 50 mg/kg IM or IV * Bleeding from trauma to lips or * Clindamycin 20 oral mucosa mg/kg IM or IV Respiratory tract- invasive procedures that incise the mucosa: * Tonsillectomy As above * Adenoidectomy Choose agent active against viridans * Bronchoscopic group of biopsy (but not for streptococci. bronchoscopy that Consider vancomycin does not break with beta lactam- mucosa) sensitive patients or methicillin * Procedures to treat resistance established infection and drainage of abscess or empyema Gastrointestinal and As above genitourinal tract (GIT & GUT): * No prophylaxis for procedures * Only prophylaxis when there is established GIT or GUT infection Infected skin, skin As above structure or musculoskeletal tissue