Pulse oximetry in the recovery room

Haemoglobin oxygen saturation (SO2) was measured percutaneously with a pulse oximeter, in a group of 150 healthy ambulant volunteers to determine the range of normal values. The measuring site was not arterialised in advance. SO2 was below 94% in 13.3% of cases, while in no case was it below 90%. SO2 was then measured in 350 patients in the recovery room after a variety of surgical and anaesthetic procedures. Only 1.1% of patients who received additional oxygen following general anaesthesia exhibited an SO2 below 90%, compared to 16.7% of similar cases who did not receive additional oxygen. Administration of additional oxygen raised the SO2 above 90% in all the latter cases. In only 55.3% of those who did not receive additional oxygen was the SO2 above 94%, compared to 86.7% of normal volunteers and 73.9% of patients who received additional oxygen. This study reiterates the need to administer supplemental oxygen to all patients in the recovery room, unless facilities are available to measure SO2. A lower alarm limit of 90% is appropriate for the peri-operative period when using the Criticare Systems 501 oximeter.     

Regional cerebral oximetry after oxygen administration

Editor—We read with interest the report of Stoneham andMartin¹ showing that the administration of oxygen 100% can antagonizethe neurological deficits after carotid cross-clamping. Thiswas attributed to an     

Pulse oximetry in methaemoglobinaemia

The results of pulse oximetry saturation in a patient with a high level of methaemoglobinaemia, who subsequently underwent intravenous methylene blue treatment, are presented. The reasons for the erroneously low values after treatment are explained. Pulse oximeters currently available are not helpful in patients treated with methylene blue and should be used with caution in patients who present with cyanosis of unknown origin.     

Pulse oximetry from the nasal septum

Study Objective: To evaluate the accuracy of the nasal septum site for pulse oximetry measurement of arterial oxyhemoglobin saturation (SpO₂) in hypothermic patients.

Design: Prospective study.

Setting: Operating theater of a public hospital.

Patients: Fourteen hypothermic (temperature 34.6°C to 36°C) patients (eight males and six females) undergoing a major surgical abdominal procedure.

Interventions: Fifty estimations of SpO₂ were simultaneously made by a flex sensor probe applied at the nasal septum site and by a finger sensor probe using a pulse oximeter. The results were compared with arterial oxygen saturation (SaO₂) as measured by arterial blood gas sampling.

Measurements and Main Results: In 18% of the estimations, the finger probe produced unmeasurable results. The nasal septum probe did not produce any unmeasurable results (p = 0.0055). In the remaining 41 estimations, a comparison of the measurements from the nasal septum versus the controls showed a mean difference of 0.15 and a limit of agreement of -0.106 to +0.398. A comparison of the measurements from the finger probe versus the controls showed a mean difference of 2.27 and a limit of agreement of 1.986 to 2.551.

Conclusion: Monitoring SpO₂ at the nasal septum site is more reliable than monitoring it at the finger site in hypothermic patients.     

Postoperative recovery of arterial oxygen saturation determined by pulse oximetry in pediatric patients

Small children are physiologically subject to arterial oxygen desaturation. However, few reports have referred to the risk factors related to postanesthetic hypoxemia and the duration of hypoxemia. The purpose of this study was to clarify these two aspects. Eighty-five ASA physical status I infants and children were included in the study. They were scheduled for minor surgery. Fifty-six underwent oral endotracheal intubation, and 29 patients breathed from a mask. Anesthesia was maintained with Enflurane or Halothane and nitrous oxide.Arterial oxygen saturation was measured with a pulse oximeter. The measurements were started shortly after patients arrival in the recovery room, and conducted every 5min at least for 1 hour. Ten patients had Sp_{O 2} values of less than 95%. In all except one, Sp_{O 2} decreased within 10min after arrival in the recovery room. Age, height, and weight of these 10 children were significantly different from the remaining 75, but there were no significant differences in anesthetic duration and postanesthetic awakefulness between the group with postanesthetic hypoxemia and the one without. The importance of monitoring the clinical condition of pediatric patients after general anesthesia is universally acknowledged. Monitoring with the pulse oximeter has proven very useful and shows that, unless oxygen saturation is monitored, all children should receive supplemental oxygen.(Nishimura M, Uchiyama, A, Nakano S, et al.: Postoperative recovery of arterial oxygen saturation determined by pulse oximetry in pediatric patients. J Anesth 7: 16–20, 1993)     

Care of obstetric patients during the immediate postanesthesia period

STUDY OBJECTIVE: To determine the level of care available to obstetric patients during the immediate postanesthesia period. DESIGN: Mail and telephone survey of members of anesthesia departments in Michigan. SETTING: All Michigan hospitals with licensed obstetric beds. PATIENTS: Patients recovering from general or major regional anesthesia following an operative delivery. INTERVENTIONS: The factors determining patient care were the physical suitability of the recovery site, skills and experience of personnel providing care in postanesthesia care units (PACUs), and adjustments in care patterns by anesthesia personnel. MEASUREMENTS AND MAIN RESULTS: Most obstetric PACUs are staffed by labor and delivery nurses whose assignment to the unit is only part of their overall patient care responsibilities within the labor and delivery area (88.2% of hospitals with more than 2,000 annual births and performing cesarean deliveries in the obstetric suite; 92.3% of hospitals with 500 to 1,999 annual births and performing cesarean deliveries in the obstetric suite). Obstetric PACUs in the remaining hospitals in either group are staffed by dedicated nurses who are permanently assigned to these units. Preparation of labor and delivery nurses for PACU duties varies greatly, but 60.0% of hospitals with more than 2,000 annual births and 30.8% of hospitals with 500 to 1,999 annual births provide no special training. Concern about the level of expertise available in obstetric PACUs staffed by labor and delivery nurses was expressed by almost every respondent and has led to a practice pattern followed by most anesthesia personnel of transferring patient care responsibility only after patients have regained consciousness, cardiovascular stability, and ventilatory adequacy. Several institutions also allow anesthesia personnel to summon nurses from the surgical PACU or to transfer patients to alternate recovery sites, such as the surgical PACU or the intensive care unit (ICU). CONCLUSIONS: In many obstetric PACUs, the level of expertise of personnel needs to be upgraded to ensure the safety of patients recovering from general or major regional anesthesia and to comply with existing care standards.     

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.     

Pulse oximetry in closed limb fractures.

Recent sporadic reports have described the role pulse oximetry might play in monitoring trauma victims, and specifically in the assessment of patients with limb fractures where doubt exists concerning the adequacy of limb blood flow distal to the fracture after manipulation. The results of a prospective study to determine the changes in arterial oxygen saturation as shown by pulse oximetry before and after manipulation are presented. The results suggest that the pulse oximeter may be of use in confirming the presence or absence of adequate blood flow distal to a fracture, but that this information should be considered in the light of the clinical findings. The role of pulse oximetry in the early detection of a compartment syndrome complicating a closed limb fracture has yet to be determined.