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.

[FIGURE 1 OMITTED]

Assessment algorithm

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)

In summary

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.

References

(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