Sir:
We wish to report that the use of henna (Lawsonia inermis) usually by women of Asian or Afro-Asian origin has considerable implications for monitoring during anaesthesia. A 38-year-old patient of Afro-Asian origin, from Somalia, required ventouse delivery in the operating room. She was medically fit and had heavy staining of her palms, fingers, soles and toes owing to repeated application of ground henna leaves. This is usually carried out by women from these cultures to mark auspicious events, in this case the birth of a child. She had a working epidural which was topped up with 10 mL bupivacaine 0.5% prior to attempted ventouse delivery.
Pulse oximetry (Datex, Finland) failed to produce a waveform or reading from any of the fingers or toes. Equipment failure was excluded by trying the probe on members of the staff. A change of oximeter (Ohmeda Biox 3700e, USA) also failed to produce a signal. The good volume peripheral pulses and warm palms excluded vasoconstriction as the possible cause for this failure. Repeated attempts to clean the fingers with soap and water or alcohol proved futile. The patient was subsequently monitored successfully by applying the probe to the ear lobe.
Darker shades of nail varnish are known to cause pulse oximetry failure. Henna, when newly applied, causes a black discolouration of the skin, which fades into the desired orange/yellow colour after a few days. During this initial phase it absorbs all visible light, possibly allowing only infrared rays to pass through, resulting in failure of pulse oximeters. (J. T. B. Moyle, personal communication).
Unlike nail varnish, henna penetrates the superficial layers of the skin and hence cannot be removed immediately by common solvents.
This is important for anaesthetists as the pulse oximeter is an important monitor in these populations, as clinical detection of desaturation is difficult and it is not always possible to place the probe on the ear lobes.
M. NIRMALAN
Manchester Royal Infirmary, Manchester
J. BALDWIN
St Mary's Hospital, Manchester
