Decreases in arterial oxygen saturation in paediatric outpatients during transfer to the postanaesthetic recovery room

Arterial oxygen saturation was measured by pulse oximetry in two groups of paediatric outpatients breathing room air during transport from the operating room to the postanaesthetic recovery room. In Group I (n = 60) readiness for transfer from OR to PARR was decided clinically. In Group II (n = 50) additional criteria of oxygen saturation (SaOe) greater than or equal to 98 per cent with end-tidal gas N2O less than or equal to 10 per cent and CO2 less than or equal to 45 mmHg were met. A higher incidence of desaturation (SaO2 less than or equal to 90 per cent) occurred in Group I (27 per cent) than in Group II (eight per cent) (P less than 0.05). More children under 2 yr desaturated in Group I (50 per cent) than Group II (17 per cent) (P greater than 0.05 less than 0.10). Twenty-two patients in each group had a recent history of upper respiratory tract infections. In these patients, desaturation was more marked in those in Group I (32 per cent) than in Group II (five per cent) (P less than 0.05). Within each group, the incidence of desaturation during transport was similar in patients with or without a recent URI.     

Warming during cardiopulmonary bypass is associated with jugular bulb desaturation.

The objective of this study was to characterize cerebral venous effluent during normothermic nonpulsatile cardiopulmonary bypass. Thirty-one (23%) of 133 patients met desaturation criteria (defined as jugular bulb venous oxygen saturation less than or equal to 50% or jugular bulb venous oxygen tension less than or equal to 25 mm Hg) during normothermic cardiopulmonary bypass (after hypothermic cardiopulmonary bypass at 27 degrees to 28 degrees C). Cerebral blood flow, calculated using xenon 133 clearance methodology, was significantly (p less than 0.005) higher in the saturated group (33.7 +/- 10.3 mL.100 g-1.min-1) than in the desaturated group (26.2 +/- 6.9 mL.100 g-1.min-1), whereas the cerebral metabolic rate for oxygen was significantly lower (p less than 0.005) in the saturated group (1.28 +/- 0.39 mL.100 g-.min-1) than in the desaturated group (1.52 +/- 0.36 mL.100 g-1.min-1) at normothermia. The arteriovenous oxygen difference at normothermia was lower in the saturated group (3.92 +/- 1.12 mL/dL) than in the desaturated group (5.97 +/- 1.05 mL/dL). Neuropsychological testing was performed in 74 of the 133 patients preoperatively and on day 7 postoperatively. There was a general decline in mean scores of all tests postoperatively in both groups with no significant difference between the groups. We conclude that cerebral venous desaturation represents a global imbalance in cerebral oxygen supply-demand that occurs during normothermic cardiopulmonary bypass and may represent transient cerebral ischemia. These episodes, however, are not associated with impared neuropsychological test performance as compared with the performance of patients with no evidence of desaturation.     

An observational study of practice during transfer of patients from anaesthetic room to operating theatre

We observed practice during transfer of 80 patients from anaesthetic room to operating theatre, to determine the duration of apnoea and the time without monitoring during the transfer process. Median (IQR [range]) time from disconnection of the breathing system in the anaesthetic room to the first breath in theatre was 54 (44-65 [27-196]) s, and from disconnection of the pulse oximetry probe to the first reading in theatre was 90 (74-103 [44-182]) s. In four patients (5%) arterial oxygen saturation fell to 94%, with the greatest desaturation observed 11%. The transfer process may represent a window of opportunity for the occurrence of harm or the first step in a chain of events leading to harm, and is difficult to justify on patient safety grounds.     

Arterial desaturation during induction in healthy adults: should preoxygenation be a routine?

We studied the haemoglobin saturation of one hundred healthy patients equally divided into two groups. Group 1 patients received three minutes of preoxygenation prior to thiopentone induction followed by inhalational anaesthetics. Group 2 patients breathed room air prior to induction. None of the patients in Group 1 showed any arterial oxygen desaturation during the five minutes of the induction period, whereas 21 patients in Group 2 showed definite desaturation (P less than 0.005), of which fifteen patients had a saturation of 90% or less (P less than 0.005) and six had a saturation of 85% or less. Since those were healthy patients and the anaesthetics were given by experienced anaesthetists, we concluded that some form of preoxygenation should be used in all patients receiving general anaesthesia.     

Ventilation and gas exchange during sleep in patients with interstitial lung disease.

Ventilation and gas exchange during overnight sleep was studied in a group of seven patients with severe interstitial lung disease (mean vital capacity 50%, mean diffusing capacity 46% predicted), to see whether clinically significant oxygen desaturation occurred. Patients with a history of loud snoring or clinically significant airflow obstruction were excluded. Sleep was fragmented in these patients, but all achieved rapid eye movement (REM) sleep. All patients showed episodes of oxygen desaturation during sleep--mean (SEM) awake arterial oxygen saturation (SaO2) was 92.9% (0.3%) compared with a mean minimum SaO2 during sleep of 83.2% (2.1%) (p less than 0.01). These episodes were, however, transient, and mean SaO2 showed only a slight fall between wakefulness and sleep (non-REM 91.5%, REM 90.4%; NS). Furthermore, SaO2 during non-REM sleep correlated well (p less than 0.001) with SaO2 during wakefulness. Respiratory frequency showed a significant fall between wakefulness and sleep--21.1 (1.8) versus 17.3 (1.5) breaths per minute (p less than 0.02). Our data suggest that nocturnal oxygen treatment need not be considered in patients with interstitial lung disease unless the level of oxygenation while they are awake indicates the need for such treatment.     

Hypoxaemia in adults in the post-anaesthesia care unit

Continuous pulse oximetry was performed on 173 adults after general anaesthesia for elective inpatient surgery, throughout their post-anaesthesia care unit (PACU) stay. Supplemental oxygen was administered for greater than or equal to 30 min after arrival and subsequently discontinued before discharge to the ward. The mean and minimum oxyhaemoglobin saturation (SpO2) after discontinuing oxygen were lower than those values achieved during oxygen administration and preoperatively (P less than 0.001). At least one hypoxaemic episode (SpO2 less than or equal to 90% for greater than or equal to 15 sec) occurred in 70 subjects (41%) and 45 of these had a moderate-severe episode (SpO2 greater than or equal to 90% for less than or equal to 2 min or SpO2 less than or equal to 85%). The hypoxaemic episodes began 20 +/- 20 min (range 1-100; median 15) after discontinuing supplemental oxygen. Cyanosis was detected in only four of the 70 patients who desaturated. Factors associated with hypoxaemia were: ASA physical status class; surgical duration greater than or equal to 90 min; and preoperative mean SpO2 less than 95%. Factors not associated with hypoxaemia were: age, sex, % ideal body weight, smoking history, preoperative minimum SpO2, premedication and type of surgery. In conclusion, after discontinuing supplemental oxygen in the PACU, hypoxaemia was common, difficult to detect clinically, and associated with ASA class, surgical duration and preoperative mean SpO2.     

Oxygen desaturation and breathlessness during corridor walking in chronic obstructive pulmonary disease: effect of oxitropium bromide.

BACKGROUND--Although exercise induced desaturation can occur in patients with chronic obstructive pulmonary disease (COPD), little is known about its frequency during everyday exercise, or how it relates to dyspnoea or prior drug treatment. METHODS--The effects of 200 micrograms inhaled oxitropium bromide, an anticholinergic bronchodilator drug, on spirometric values, dyspnoea score, and oxygen saturation during corridor walking and cycle ergometry were studied in a double blind, randomised, placebo controlled study. RESULTS--Oxitropium produced a small increase in forced expired volume in one second (FEV1) from 0.76 (0.28) 1 to 0.93 (0.69) 1 and in six minute walking distance from 311 (93) m to 332 (86) m, but did not change progressive cycle exercise duration. Resting and end exercise breathlessness levels were reduced in both forms of exercise after oxitropium. Resting oxygen saturation fell significantly after active bronchodilator from 92.9% (3.7%) to 92.0% (4.1%) but the nadir saturation during exercise was unchanged. The patients desaturated more during corridor walking than cycle ergometry [walking 7.8% (4.4%), cycle ergometry 2.1% (2.1%)]. Baseline walking distance was related to FVC, resting breathlessness and resting oxygen saturation (multiple r2 = 0.46) but only resting saturation correlated with end exercise breathlessness (r2 = -0.25). Improvements in symptoms or exercise performance after oxitropium could not be predicted by changes in spirometric indices or oxygen saturation. CONCLUSIONS--In patients with COPD arterial oxygen desaturation during self-paced walking is common, of greater severity than that during cycle ergometry, but is unaffected by inhaled oxitropium bromide. The factors that predict initial performance are not appropriate markers of functional improvement after an active bronchodilator drug.     

Recovery room oxygenation: A comparison of nasal catheters and 40 per cent oxygen masks

One hundred and sixty-one ASA physical status I-III patients undergoing elective surgery were evaluated using nasal catheters versus 40 per cent O2 venturi masks. Twenty-one per cent of the patients arrived in the recovery room with hypoxia as measured with a pulse oximeter (SaO2 less than 90 per cent). Fifteen minutes later all patients who arrived hypoxic were well oxygenated on their chosen oxygen therapy. Only one patient that arrived normoxic became hypoxic using a nasal catheter 15 minutes later. There was no statistical difference between patients given 40 per cent O2 by mask versus patients given oxygen by nasal catheter. The mean SaO2 for the group given 40 per cent O2 at 15 minutes was 96.7 +/- 2.15 per cent versus 96.6 +/- 2.48 per cent for nasal catheters. Nasal catheters are as effective as 40 per cent O2 masks for treating hypoxia in the recovery room. Obesity and age were statistically significant risk factors in the patients that arrived hypoxic. Patients were 47.4 +/- 15.6 years in the hypoxic group versus 38.3 +/- 15.6 years in the non-hypoxic group (p less than 0.001). Patients having an endotracheal tube with intermittent positive pressure ventilation or having a premedication were more apt to be hypoxic on arrival. These last two factors were closely associated and may reflect bias. The patient's gender, history of smoking, presence of obstructive lung disease, not including asthma, location of incision, or type of anaesthetic were not statistically significant risk factors.     

Arterial desaturation in HIV positive patients undergoing sputum induction.

Arterial oxygen saturation (SaO2) was monitored continuously during and immediately after sputum induction in 41 HIV positive patients with respiratory symptoms and in 20 symptomless medical and nursing staff, who acted as control subjects. Arterial oxygen desaturation (defined as SaO2 less than or equal to 92%) occurred during sputum induction and persisted for up to 20 minutes after the end of the procedure in 11 of the 20 patients with Pneumocystis carinii pneumonia and in nine of the 21 patients with other respiratory diagnoses. None of the control subjects showed oxygen desaturation. Neither the severity of chest radiographic abnormalities, the alveolar-arterial oxygen gradient (both measured before sputum induction), nor baseline SaO2 prospectively identified the patients who developed oxygen desaturation. Two patients, one with pneumocystis pneumonia, developed dyspnoea and had a fall in arterial oxygen saturation to 84% within 10 minutes of starting sputum induction. The procedure was abandoned in both patients and in two further patients, who developed severe nausea and reaching but no oxygen desaturation. Sputum induction in HIV positive patients with respiratory symptoms may induce a fall in SaO2 that persists after this procedure. This may be important if other procedures are performed soon after sputum induction.     

Monitoring fiberoptic intubation using non-invasive pulse oximetry

Non-invasive measurements of oxygen saturation are attractive because continuous information is provided, which may result in improved patient care. We evaluated a new finger pulsoximeter as a measure of arterial oxygen saturation during fiberoptic intubation. Secondly, we studied the kinetics of oxygen-haemoglobin desaturation during the procedure. In 15 patients investigated, 118 simultaneous comparisons between in vivo (Pulsoximeter Nellcor N 101) and in vitro (CO-Oximeter Corning 2500) oxygen-haemoglobin saturation were made. Statistical analysis of these pooled data yielded an excellent correlation (r = 0.94, P less than 0.001). Our results demonstrate that non-invasive oxygen monitoring during fiberoptic intubation is reliable, and we detected oxygen desaturation of less than 80% if ventilation was not assisted.     

Diagnosis of clinically unrecognized endobronchial intubation in paediatric anaesthesia: which is more sensitive,pulse oximetry or capnography?

In a prospective, randomized, single-blind study of combined pulse oximetry and capnography in 196 children whose anaesthetic was managed by endotracheal intubation we observed 10 patients with 14 episodes of endobronchial intubation (EBI). Pulse oximetry provided the first diagnostic clue in 13 events; the one event first diagnosed by capnography was also accompanied by oxygen desaturation. Two EBI occurred immediately after the initial intubation (‘primary’ EBI). Twelve episodes of EBI in eight patients occurred after correct initial endotracheal tube position (‘secondary’ EBI). EBI gave rise to eight episodes of ‘minor’ desaturation (oxygen saturation (Spo₂) ≤ 95%≥ 60 s); four resulted in ‘major’ desaturation (Spo₂≤ 85% for 30 s). Only three EBI events produced clinical signs or symptoms. Seven patients were less than 1 year; EBI was not, however, related to age. A high frequency (5.1%) of clinically unrecognized EBI was found in infants and children. A persistent yet small, reduction in oxygen saturation provided the early evidence of secondary EBI in the majority of cases. Clinical signs and capnography proved least effective in the early diagnosis of secondary EBI.     

Effect of oxygen on tachycardia and arterial oxygen saturation during colonoscopy.

OBJECTIVE: To evaluate the effect of supplementary oxygen on heart rate and arterial oxygen saturation during colonoscopy. DESIGN: Controlled study. SETTING: Two university hospitals, Denmark. SUBJECTS: 40 patients having colonoscopy. INTERVENTIONS: 20 patients were given supplementary oxygen through nasal prongs (2 L/min), and 20 patients breathed room air during colonoscopy. All patients were given conscious sedation and were monitored with a pulse oximeter during colonoscopy. MAIN OUTCOME MEASURES: Tachycardia (pulse rate>100 min(-1)) and arterial oxygen desaturation (SpO2<90%) during colonoscopy. RESULTS: There were no differences in the incidence of tachycardia or mean heart rate during endoscopy between the two groups, and no patient developed symptomatic cardiac arrhythmias or hypotensive episodes. 10 patients in the room air compared with none in the oxygen treatment group (p = 0.0004) had one or more episodes during which arterial oxygen saturation fell below 90% during colonoscopy, and mean oxygen saturation was higher in the oxygen treatment group than in the room air group (p < 0.001). No clinical complications occurred in either group. CONCLUSION: Hypoxaemia and tachycardia are common during routine colonoscopy. The use of supplemental oxygen prevented hypoxaemia, but had no significant effect on heart rate.     

Arterial desaturation in healthy children during and after minor surgery

Pulse oximetry (PO) was applied to 79 otherwise healthy children during and after minor ENT surgery under general anaesthesia in private practice. The PO data were not available to the anaesthetist unless desaturation to less than or equal to 85% was present for greater than or equal to 30 s. This occurred in 12 and 9 cases during anaesthesia and recovery, respectively, only 8 and 5 cases, respectively, being diagnosed clinically. Desaturation during and after anaesthesia was more common in children undergoing adenoidectomy than during procedures for which endotracheal intubation was not performed. During recovery, desaturation was more likely to occur in the same patients again. Lower values of SaO2 were found in younger children and in children resisting or crying at induction. There was a (weak) negative correlation between SaO2 and HR. As clinically undiagnosed desaturation occurs even in healthy children undergoing minor surgical procedures, a more widespread use of PO during and after anaesthesia may be advisable.     

Continuous monitoring of arterial oxygen saturation with pulse oximetry during transfer to the recovery room

The incidence of hypoxemia in the immediate postoperative period was determined using a pulse oximeter for continuous monitoring of arterial oxygen saturation (SaO2) in 95 ASA class I or II adult patients breathing room air during their transfer from the operating room to the recovery room. Hypoxemia was defined as 90% SaO2 (arterial oxygen partial pressure (PaO2) approximately equal to 58 mm Hg). Severe hypoxemia was defined as 85% SaO2 (PaO2 approximately equal to 50 mm Hg). Hypoxemia occurred in 33 (35%) patients; severe hypoxemia occurred in 11 (12%). Postoperative hypoxemia did not correlate significantly with anesthetic agent, age, duration of anesthesia, or level of consciousness. There was a statistically significant correlation (P less than 0.05) between hypoxemia and obesity. All three patients with a history of mild asthma became severely hypoxemic even though none had perioperative evidence of obstructive disease, also a statistically significant (P less than 0.003) finding.     

Intraoperative events diagnosed by expired carbon dioxide monitoring in children

Expired carbon dioxide measurements (PECO₂) were used (1) to assess the adequacy of initial alveolar ventilation, and (2) to document intraoperative airway events and metabolic trends. Three hundred and thirty-one children were studied. Thirty-five intraoperative events were diagnosed by continuous PeCO₂ monitoring; 20 were potentially life-threatening problems (malignant hyperthermia, circuit disconnection or leak, equipment failure, accidental extubation, endobronchial intubation, or kinked tube); only two of these were also diagnosed clinically. The duration of anaesthesia may be a factor: 3.9 hours for cases with events vs. 2.5 hours for cases without events (p < 0.002). There was a higher incidence of hypercarbia (peak expired PeCO₂≥ 50) in children who were not intubated (29 per cent) compared to those who had an endotracheal tube in place (12 per cent) (p = 0.0001). Hypocarbia (peak expired PeCO₂≤30) was more frequent in intubated cases (11 per cent) than in unintubated cases (three per cent) (p = 0.03). There was a high incidence of hypocarbia in infants less than one year of age (p = 0.02). We conclude: (1) lifethreatening airway problems are common during anaesthesia in paediatric patients; (2) quantitative measurement of PECO₂ provides an early warning of potentially catastrophic anaesthetic mishaps; (3) the incidence of events increases with duration of anaesthesia.     

Hypoxia during upper gastrointestinal endoscopy with and without sedation and the effect of pre-oxygenation on oxygen saturation

In Study A, the incidence of arterial oxygen desaturation was studied using pulse oximetry (SaO2) in 100 sedated and 100 nonsedated patients breathing room air who underwent diagnostic upper gastrointestinal endoscopy. Hypoxia (SaO2 92% or less of at least 15 s duration) occurred in 17% and 6% of sedated patients and nonsedated patients, respectively (p < 0.03). Mild desaturation (SaO2 94% or less and less than 15 s duration) occurred in 47% of sedated patients compared with 12% of nonsedated patients (p < 0.001). In Study B, the effects of supplementary oxygen therapy and the effects of different pre-oxygenation times on arterial oxygen saturation (SaO2) in sedated patients were studied using pulse oximetry. One hundred and twenty patients who underwent diagnostic upper gastrointestinal endoscopy with intravenous sedation were studied. Patients were randomly allocated to one of four groups: Group A (n = 30) received no supplementary oxygen while Groups B-D received supplementary oxygen at 4 1 x min(-1) via nasal cannulae. The pre-oxygenation time in Group B (n = 30) was zero minutes, Group C (n = 30) was 2 min and Group D (n = 30) was 5 min before sedation and introduction of the endoscope. Hypoxia occurred in seven of the 30 patients in Group A and none in groups B, C and D (p < 0.001). We conclude that desaturation and hypoxia is common in patients undergoing upper gastrointestinal endoscopy with and without sedation. Sedation significantly increases the incidence of desaturation and hypoxia. Supplementary nasal oxygen at 4 1 x min(-1) in sedated patients abolishes desaturation and hypoxia. Pre-oxygenation confers no additional benefit.     

Oxygen saturation and cardiovascular changes during fibreoptic intubation under general anaesthesia

Sixty patients who required fibreoptic nasotracheal intubation were studied. Arterial oxygen saturation, arterial blood pressure and heart rate were monitored continuously during fibreoptic intubation under deep halothane anaesthesia. There were significant decreases (p less than 0.001) in arterial blood pressure and heart rate despite administration of intravenous colloid and atropine. Almost one third of the patients (18 out of 60) suffered a decrease in arterial oxygen saturation below 90% during the intubation sequence and in five patients the saturation fell below 80%. The episodes of desaturation were not related to the induction-intubation time or to the grade of laryngeal visibility at direct laryngoscopy.     

Hypoxaemia produced by an oesophageal stethoscope: A case report

A seven-month-old child with complex cyanotic heart disease desaturated dramatically following induction of anaesthesia. While a degree of hypoxaemia would have been acceptable in this infant, pulse oximetry detected an abrupt desaturation prompting the anaesthetist to consider other less common causes of cyanosis. This episode of desaturation subsided with the removal of a 12 french oesophageal stethoscope which had been inserted following induction. Further attempts to re-insert this oesophageal probe led to repeated episodes of desaturation. The most likely cause of this desaturation was a reduction in pulmonary blood flow due to compression by the oesophageal probe of an aorto-pulmonary collateral posterior to the oesophagus.     

Supplemental oxygen after ambulatory surgical procedures

The aim of this study was to determine the need for supplemental oxygen during recovery from general anesthesia for ambulatory surgery in healthy women without obesity or respiratory disease. Arterial oxygen saturation by pulse oximetry (SpO2) was monitored throughout the first postoperative hour in 164 patients. The patients breathed room air during recovery. Supplemental oxygen was given only to those who became hypoxemic (SpO2 less than or equal to 92%). It was discontinued at the end of 15 minutes and reinstituted for another 15 minutes if hypoxemia recurred. Twelve patients (7%) became hypoxemic and required supplemental oxygen for various periods of time up to 105 minutes. The need for supplemental oxygen increased with increasing age (P less than 0.05) but was not associated with a history of cigarette smoking, tracheal intubation, amount of opioids or sedatives given intraoperatively, anesthetic duration, or level of consciousness during recovery. Hypoxemia was neither predictable nor clinically apparent. We recommend that, unless arterial oxygenation is monitored, ambulatory patients should routinely receive supplemental oxygen during recovery from general anesthesia.     

Preoxygenation techniques: the value of nitrous oxide

Changes in arterial oxygen saturation during induction of anaesthesia and intubation were studied using the pulse oximeter. Seventy-five young ASA I patients undergoing elective uncomplicated surgery were divided equally into three groups. The patients were preoxygenated with 100% oxygen, 50% oxygen: 50% nitrous oxide or 30% oxygen: 70% nitrous oxide for 1 min. All were then induced with thiopentone, paralysed with suxamethonium and orally intubated. Arterial oxygen saturations were continuously recorded by a separate investigator. All groups showed similar arterial desaturation during suxamethonium-induced apnoea and intubation, but the degree of desaturation was not clinically significant and no patient showed clinical signs of hypoxaemia. Preoxygenation with mixtures of oxygen and nitrous oxide can hasten the build-up of alveol nitrous oxide concentration and help to smooth induction without compromising oxygenation of patients.