Fouzia Anis Khan  ( Department of Anaesthesiology, The Aga Khan University Hospital, Karachi. )
Iffat Anjum  ( Department of Anaesthesiology, The Aga Khan University Hospital, Karachi. )
Rehana S. Kamal  ( Department of Anaesthesiology, The Aga Khan University Hospital, Karachi. )

A case is reported where reduced oxygen saturationwas detected bya pulse oximeter before clinical signs of pulmonary oedema appeared. A 45 years old, 82 kilogram lady presented for emergency surgery with subacute intestinal obstruction. She had no previous history of any cardiovascular, respiratory or metabolic disorder. She underwent partial colectomy and colostomy. Two days later she was again brought to the opera­ting room for revision of colostomy. On pre-opcra­tive examination she was conscious and orien­tated, afebrile, heart rate of 135 beats/minute and a respiratory rate of 45/minute. She was in a posi­tive balance of + 1350 mls over the last 24 hours. On chest auscultation, she had only left basal crc­pitations. The preoperative arterial blood gases showed a P02 of 90.6mm of Hg and oxygen satura­tion of 97.3% on 8 L of oxygen per minute via MC mask. The patient was preoxygenated through the Magill\'s circuit and a pulse oximeter probe (Oh­media Biox 3700) was attached to her forefinger which showed an oxygen saturation of 98%. Ana­esthesia was induced with a sleep dose of thiopen­tone, and 100mgs of suxamethonium. She was in­tubated with cricoid pressure and anaesthesia maintained with fifty per cent nitrous oxide and oxygen, pancuronium and pethidine. Intraopera­tively she remained stable and her oxygen satura­tion remained at 96%. The patient was reversed with atropine and neostigmine. After reversal, but before extubation she was noticed to have difficulty in breathing and the oxygen saturation dropped to 87% on 8L/min-ute of oxygen. The ventilation was thereafter as­sisted and the saturation showed very slight im­provement to 89%. Chest auscultation at this stage did not reveal any new findings. Nerve stimulator showed a fully reversed block. Arterial blood gases showed a pH of 7.38, pCO2 of 46.4 mm of Hg, P02 of 55 mm of Hg, bicarbonate 24, base excess 2.2 and oxygen saturation 87.8%. She was transferred to the Intensive Care Unit with an endotracheal tube in situ and connected to a T piece circuit on 12 L/minute humidified oxygen. Her oxygen satu­ration was monitored continuously and was 90%. A chest x-ray was done. On endotracheal tube suctioning slightly pinkish tinged secretions were observed. Chest auscultation at that stage did not reveal any new findings. She was given frusemide 40 mgs I.V stat’ and her oxygen saturation im­proved dramatically to 96-97% after diuresis. Her chest x-ray when received supported the findings of early pulmonary oedema. She was extubated one hour later.

The major causes of pulmonary oedema in the perioperative period are cardiac failure, fluid overload, airway obstruction, acid aspiration, gas embolism, allergy, higher oxides of nitrogen, reac­tions to blood and blood products¹. Usually pul­monary oedema does not present itself in the recovery because of peripheral vasodilatation. Only when peripheral vasoconstriction occurs due to pain or cold, fluid shifts from peripheral to central compartment and clinical pulmonary oed­ema occurs². Pulse oximeter is a non-invasive instrument that detects hypoxie hypoxia and is accurate within 2%. Its use is now becoming a routine in the intraopcrative period³. In our case the diagnosis of pulmonary oedema would have been delayed if the oxygen saturation monitoring was not used. Pulse oximetry as an early warning device could be an additional use of this useful non- invasive moni­tor.

1. Fisher, M and Stevenson, LF. Unexplained acute pul­monary oedema related to anaesthesia. Anaesth. Inten­sive Care, 1986; 14: 29.
2. Mason, R.A. The pulse oximeter - an early warning device? (letter). Anaesthesia, 1987; 42: 784.
3. Taylor, M.D. and Whitwam, J.G.The current status of pulse oximetry. Clinical value of continuous noninvasive oxygen saturation monitoring. Anaesthesia, 1986; 41:943.