Observational study of perioperative P tc co2 and S p o2 in non-ventilated patients receiving epidural infusion or patient-controlled analgesia using a single earlobe monitor (TOSCA) †

Undetected Respiratory Depression in People with Opioid Use Disorder

BACKGROUND

Opioid-related deaths are increasing globally. Respiratory complications of opioid use and underlying respiratory disease in people with Opioid Use Disorder (OUD) are potential contributory factors. Individual variation in susceptibility to overdose is, however, incompletely understood. This study investigated the prevalence of respiratory depression (RD) in OUD treatment and compared this to patients with chronic obstructive pulmonary disease (COPD) of equivalent severity. We also explored the contribution of opioid agonist treatment (OAT) dosage, and type, to the prevalence of RD.

METHODS

There were four groups of participants: 1) OUD plus COPD ('OUD-COPD', n = 13); 2) OUD without COPD ('OUD', n = 7); 3) opioid-naïve COPD patients ('COPD'n = 13); 4) healthy controls ('HC'n = 7). Physiological indices, including pulse oximetry (SpO₂%), end-tidal CO₂ (ETCO₂), transcutaneous CO₂ (TcCO₂), respiratory airflow and second intercostal space parasternal muscle electromyography (EMG_para), were recorded continuously over 40 min whilst awake at rest. Significant RD was defined as: SpO₂%< 90% for > 10 s, ETCO₂ per breath > 6.6 kPa, TcCO₂ overall mean > 6 kPa, respiratory pauses > 10 s RESULTS: At least one indicator was observed in every participant with OUD (n = 20). This compared to RD episode occurrence in only 2/7 HC and 2/13 COPD participants (p < 0.05,Fisher's exact test). The occurrence of RD was similar in OUD participants prescribed methadone (n = 6) compared to those prescribed buprenorphine (n = 12).

CONCLUSIONS

Undetected RD is common in OUD cohorts receiving OAT and is significantly more severe than in opioid-naïve controls. RD can be assessed using simple objective measures. Further studies are required to determine the association between RD and overdose risk.

Comparison of Fentanyl plus different doses of dexamethasone with Fentanyl alone on postoperative pain, nausea, and vomiting after lower extremity orthopedic surgery

Intravenous patient controlled analgesia (PCA) with opioids to provide perioperative analgesia is commonly used after orthopedic surgery, but have side-effects. Addition of adjutant drugs results in reducing the side-effects and the dosage of opioids. The aim of current study was to evaluation the analgesic efficacy of combination of fentanyl and dexamethasone (8 and 16 mg) in compared with fentanyl alone in patients undergoing orthopedic surgery of the lower extremity. In a double-blind clinical trial, 102 patients were randomly allocated to receive PCA, which included: F+S group (fentanyl 1 mcg/ml + isotonic saline), F+8mD group (fentanyl 1 mcg/ml + dexamethasone 8 mg/ml), and F+16mD group (fentanyl 1 mcg/ml + dexamethasone 16 mg/ml). Anesthesia technique and rescue analgesia regimen were standardized. Postoperatively, pain was assessed based on visual analog scale (VAS). In addition, we evaluated the postoperative nausea and vomiting (POVN) in different groups. In over the post-operative period, the mean VAS-score was significantly lower in the F+16mD group than the F+S and the F+8mD groups (p<0.001 and p<0.01, respectively). In addition, the incidence of PONV significantly was lower in the F+18mD group than the F+S group (p<0.05). We conclude that the addition of preoperative intravenous high dose of dexamethasone (16 mg) to fentanyl was effective in reducing postoperative pain and PONV after orthopedic surgery of the lower extremity.

[Neuraxial Morphine for Postoperative Analgesia after Caesarean Deliveries]

The use of neuraxial morphine, in combination with nonopioid analgesic regimens for postoperative analgesia after Caesarean deliveries is common practice, especially in the Anglo-American world. Neuraxial morphine offers a longer-lasting superior analgesia than intravenous opioids or patient-controlled analgesia. If neuraxial anaesthesia is being used for a caesarean delivery, it may be recommended to concomitantly administer neuraxial morphine for the postoperative analgesia.A low dose of neuraxial morphine in a healthy parturient bears a low morbidity and mortality risk. The optimal frequency, duration and modality of respiratory monitoring for patients at low risk for respiratory depression is dependent on the dose of morphine administered and the patient-specific and obstetric risk profile.

A prospective, randomized, open label, controlled study investigating the efficiency and safety of 3 different methods of rectus sheath block analgesia following midline laparotomy

BACKGROUND

There is a controversy regarding the efficacy of rectus sheath block (RSB). The aim of the present study was to evaluate analgesic efficacy and safety of three different methods of RSB in postoperative pain management after midline laparotomy.

METHODS

A prospective, randomized, controlled, open-label clinical trial with 4 parallel groups was conducted in a tertiary care hospital in Finland. A total of 57 patients undergoing midline laparotomy were randomized to the control group (n = 12) or to 1 of the 3 active RSB analgesia groups: single-dose (n = 16), repeated-doses (n = 12), or continuous infusion (n = 17). Opioid consumption with iv-patient-controlled analgesia pump was recorded, and pain scores and patients' satisfaction were surveyed on an 11-point numeric rating scale for the first 48 postoperative h. Plasma concentrations of oxycodone and levobupivacaine were analyzed. All adverse events during the hospital stay were recorded.

RESULTS

Oxycodone consumption was less during the first 12 h in the repeated-doses and in the continuous infusion groups (P = .07) and in numerical values up to 48 h in the repeated-doses group. Plasma oxycodone concentrations were similar in all 4 groups. Pain scores were lower in the repeated-doses group when coughing during the first 4 h (P = .048 vs. control group), and at rest on the first postoperative morning (P = .034 vs. the other 3 groups) and at 24 h (P = .006 vs. the single-dose group). All plasma concentrations of levobupivacaine were safe. The patients' satisfaction was better in the repeated-doses group compared with the control group (P = .025). No serious or unexpected adverse events were reported.

CONCLUSIONS

RSB analgesia with repeated-doses seems to have opioid sparing efficacy, and it may enhance pain relief and patients' satisfaction after midline laparotomy.

Portable respiratory polygraphy monitoring of obese mothers the first night after caesarean section with bupivacaine/morphine/fentanyl spinal anaesthesia

Background: Obesity, abdominal surgery, and intrathecal opioids are all factors associated with a risk for respiratory compromise. The aim of this explorative trial was to study the apnoea/hypopnea index 1st postoperative night in obese mothers having had caesarean section (CS) in spinal anaesthesia with a combination of bupivacaine/morphine and fentanyl. Methods: Consecutive obese (BMI >30 kg/m 2) mothers, ≥18 years, scheduled for CS with bupivacaine/morphine/fentanyl spinal anaesthesia were monitored with a portable polygraphy device Embletta /NOX on 1 st postoperative night. The apnoea/hypopnea index (AHI) was identified by clinical algorithm and assessed in accordance to general guidelines; number of apnoea/hypopnea episodes per hour: <5 "normal", ≥5 and <15 mild sleep apnoea, ≥15 and <30 moderate sleep apnoea, ≥ 30 severe sleep apnoea. Oxygen desaturation events were in similar manner calculated per hour as oxygen desaturation index (ODI). Results: Forty mothers were invited to participate: 27 consented, 23 were included, but polysomnography registration failed in 3. Among the 20 mothers studied: 11 had an AHI <5 ( normal), 7 mothers had AHI ≥5 but <15 ( mild OSAS) and 2 mothers had AHI ≥15 ( moderate OSA), none had an AHI ≥ 30. The ODI was on average 4.4, and eight patients had an ODI >5. Mothers with a high AHI (15.3 and 18.2) did not show high ODI. Mean saturation was 94% (91-96%), and four mothers had mean SpO 2 90-94%, none had a mean SpO2 <90%. Conclusion: Respiratory polygraphy 1 st night after caesarean section in spinal anaesthesia with morphine in moderately obese mothers showed AHIs that in sleep medicine terms are considered normal, mild and moderate. Obstructive events and episodes of desaturation were commonly not synchronised. Further studies looking at preoperative screening for sleep apnoea in obese mothers are warranted but early postop respiratory polygraphy recording is cumbersome and provided sparse important information.

Portable respiratory polygraphy monitoring of obese mothers the first night after caesarean section with bupivacaine/morphine/fentanyl spinal anaesthesia

Background: Obesity, abdominal surgery, and intrathecal opioids are all factors associated with a risk for respiratory compromise. The aim of this observational study was to explore the use of portable respiratory polygraphy for monitoring of obese mothers for respiratory depression the first night after caesarean section (CS) with bupivacaine/morphine/fentanyl spinal anaesthesia. Methods: Consecutive obese (BMI >30 kg/m 2) mothers, ≥18 years, scheduled for CS with bupivacaine/morphine/fentanyl spinal anaesthesia were monitored with a portable polygraphy device Embletta /NOX on the first postoperative night. The apnoea-hypopnea index (AHI) was identified by clinical algorithm and assessed in accordance to general guidelines. Results: Forty mothers were invited to participate: 27 consented, 23 were included, but polysomnography registration failed in 3. Among the 20 mothers: 11 had an AHI <5; 7, AHI 5-15; and 2, AHI >15. The oxygen desaturation index (ODI) was on average 4.4, and eight patients had an ODI >5. Those mothers with a high AHI (15.3 and 18.2) did not show high ODI or signs of hypercapnia on transcutaneous CO 2 registration. Mean saturation was 94% (91-96), and four mothers had mean saturation between 90-94%, but none had a mean SpO 2 <90%. Mean nadir saturation was 71% (range, 49-81%).  None of the mothers showed clinical signs or symptoms of severe respiratory depression, shown by routine clinical monitoring. Conclusion: We found portable polygraphy registration during early post-CS in moderately obese mothers having had intrathecal morphine/fentanyl cumbersome and although episodes of oxygen saturation decrease were noticed, obstructive events and episodes of desaturation were commonly not synchronised. Upper airway obstructions seem not be of major importance in this clinical setting. Monitoring of respiratory rate, SpO 2 and possibly transcutaneous CO 2 in mothers at high risk of respiratory distress warrants further studies. Preoperative screening in obese patients, at risk for sleep breathing disorder, is of course of value.

Transcutaneous Carbon Dioxide Measurements in Women Receiving Intrathecal Morphine for Cesarean Delivery: A Prospective Observational Study

BACKGROUND

Neuraxial morphine is the most commonly used analgesic technique after cesarean delivery. The incidence of respiratory depression is reported to be very low (0%-1.2%) in this patient population as measured by pulse oximetry and respiratory rates. However, hypercapnia may be a more sensitive measure of respiratory depression. In the current study, the incidence of hypercapnia events (transcutaneous CO2 [TcCO2] >50 mm Hg) for ≥2-minute duration was evaluated using the Topological Oscillation Search with Kinematical Analysis monitor in women who received intrathecal morphine for postcesarean delivery analgesia.

METHODS

Healthy women (>37 weeks of gestation) scheduled for a cesarean delivery with spinal anesthesia with intrathecal morphine were recruited. Baseline STOP-BANG sleep apnea questionnaire and TcCO2 readings were obtained. Spinal anesthesia was initiated with 12 mg hyperbaric bupivacaine, 15 µg fentanyl, and 150 µg morphine. The Topological Oscillation Search with Kinematical Analysis monitor was reapplied in the postanesthesia care unit and TcCO2 measurements obtained for up to 24 hours. Supplemental opioid administration and adverse respiratory events were recorded. The primary outcome was the incidence of hypercapnia events, defined as a TcCO2 reading >50 mm Hg for ≥2 minutes in the first 24 hours after delivery.

RESULTS

Of the 120 women who were recruited, 108 completed the study. Thirty-five women (32%; 99.15% confidence interval, 21%-45%) reached the primary outcome of a sustained hypercapnia event. The median time (interquartile range [IQR]) from intrathecal morphine administration to the hypercapnia event was 300 (124-691) minutes. The median (IQR) number of events was 3 (1-6) and longest duration of an event was 25.6 (8.4-98.7) minutes. Baseline median (IQR) TcCO2 measurements were 35 (30-0) mm Hg and postoperatively, median (IQR) TcCO2 measurements were 40 (36-43) mm Hg, a difference of 5 mm Hg (99.15% confidence interval of the difference 2-8 mm Hg, P < .001). The incidence of hypercapnia events was 5.4% in women with a baseline TcCO2 value ≤31 mm Hg, 22.5% with a baseline TcCO2 between 32 and 38 mm Hg, and 77.4% with a baseline TcCO2 >38 mm Hg (P < .001).

CONCLUSIONS

Hypercapnia events (>50 mm Hg for ≥2-minute duration) occurred frequently in women receiving 150 μg intrathecal morphine for postcesarean analgesia. Higher baseline TcCO2 readings were observed in women who had hypercapnia events.

Analysis of Physiological Respiratory Variable Alarm Alerts Among Laboring Women Receiving Remifentanil

BACKGROUND

Remifentanil may be used by laboring women for analgesia, despite controversy because of potential apneas. We evaluated candidate variables as early warning alerts for apnea, based on prevalence, positive predictive rate, sensitivity for apnea event detection, and early warning alert time intervals (lead time) for apnea.

METHODS

We performed a secondary analysis of respiratory physiological data that had been collected during a prospective IRB-approved study of laboring women receiving IV patient-controlled boluses of remifentanil 20 to 60 μg every 1 to 2 minutes. Analyzed data included the respiratory rate (RR), end-tidal CO2 (EtCO2), pulse oximetry (SpO2), heart rate (HR), and the Integrated Pulmonary Index (IPI; Capnostream 20; Medtronic, Boulder, CO) that had been recorded continuously throughout labor. We defined immediate early warning alerts as any drop in a variable value below a prespecified threshold for 15 seconds: RR < 8 breaths per minute (bpm), EtCO2 < 15 mm Hg, and SpO2 < 92%. We defined alerts as "sustained" when the value remained below the threshold for ≥ 10 further seconds. The IPI value (1 to 10; 10 = healthy patient, ≤4 = immediate attention required, 1 = dire condition) was generated from a proprietary algorithm using RR, EtCO2, SpO2, and HR parameters. Apnea was defined as maximal CO2 < 5 mm Hg for at least 30 consecutive seconds.

RESULTS

We counted 62 apneas, among 10 of 19 (52.6%) women who received remifentanil (total dose 1725 ± 1392 μg, administered over 160 ± 132 minutes). We counted 331 immediate early warning alerts for the variables; 271 (82%) alerts were sustained for ≥10 seconds. The positive predictive value of alerts for apnea was 35.8% (99% confidence interval [CI]: 27.1-45.6), 28.9% (99% CI: 20.8-38.7), 4.3% (99% CI: 1.9-9.6), and 24.6% (99% CI: 18.3-32.2) for RR, EtCO2, SpO2, and IPI, respectively. The sensitivity for apnea event detection was 100% (99% CI: 90.3-100) for RR (<8 bpm) and IPI (≤4); 75.8% (99% CI: 59.8-86.9) for EtCO2 <15 mm Hg; and 14.5% (99% CI: 6.5-29.4) for SpO2 <92%. We found a statistically significant difference in the timing of RR, EtCO2, SpO2, and IPI alerts for apnea; Friedman's Q = 33.53; P < .0001. The EtCO2 had a median (interquartile range) lead time of -0.2 (-12.2 to 0.7) seconds, and SpO2 had a median (interquartile range) lead time of 40.0 (40.0 to 40.0) seconds.

CONCLUSIONS

The majority of women receiving IV remifentanil for labor analgesia experienced apneas. Alerts for EtCO2 (<15 mm Hg), RR (<8 bpm), and IPI (≤4) detected most apneas, whereas SpO2 alerts missed the majority of apneas. All variables had a low positive predictive rate, demonstrating the limitations of the respiratory monitors utilized as early warning surveillance for apneas in this setting.

Target-controlled versus fractionated propofol sedation in flexible bronchoscopy: A randomized noninferiority trial

BACKGROUND AND OBJECTIVE

Fractionated propofol administration (FPA) in flexible bronchoscopy (FB) may lead to oversedation and an increased risk of adverse events, because a stable plasma concentration of propofol is not maintainable. The purpose of this randomized noninferiority trial was to evaluate whether target-controlled infusion (TCI) of propofol is noninferior to FPA in terms of safety in FB.

METHODS

Coprimary outcomes were the mean lowest arterial oxygen saturation (SpO₂ ) during FB and the number of propofol dose adjustments in relation to procedure duration. Secondary outcomes were the number of occasions with SpO₂  < 90% and/or oxygen desaturations of >4% from baseline, number of occasions with systolic blood pressure < 90 mm Hg, cough frequency, cumulative propofol dose, recovery time, maximum transcutaneous CO₂ , mean SpO₂ and O₂ delivery during FB.

RESULTS

Seventy-seven patients were included. TCI was noninferior to FPA in terms of mean (standard deviation) lowest SpO₂ during the procedure (88.3% (5.4%) vs 86.9% (7.3%)) and required fewer dose adjustments (0.04/min vs 0.28/min, P < 0.001) but a higher cumulative propofol dose (264 vs 194 mg, P = 0.003). All other secondary outcomes were comparable between the groups.

CONCLUSION

We suggest that TCI of propofol is a favourable sedation technique for FB with equal safety issues and fewer dose adjustments compared with FPA.

Understanding Heroin Overdose: A Study of the Acute Respiratory Depressant Effects of Injected Pharmaceutical Heroin

Opioids are respiratory depressants and heroin/opioid overdose is a major contributor to the excess mortality of heroin addicts. The individual and situational variability of respiratory depression caused by intravenous heroin is poorly understood. This study used advanced respiratory monitoring to follow the time course and severity of acute opioid-induced respiratory depression. 10 patients (9/10 with chronic airflow obstruction) undergoing supervised injectable opioid treatment for heroin addiction received their usual prescribed dose of injectable opioid (diamorphine or methadone) (IOT), and their usual prescribed dose of oral opioid (methadone or sustained release oral morphine) after 30 minutes. The main outcome measures were pulse oximetry (SpO2%), end-tidal CO2% (ETCO2%) and neural respiratory drive (NRD) (quantified using parasternal intercostal muscle electromyography). Significant respiratory depression was defined as absence of inspiratory airflow >10s, SpO2% < 90% for >10s and ETCO2% per breath >6.5%. Increases in ETCO2% indicated significant respiratory depression following IOT in 8/10 patients at 30 minutes. In contrast, SpO2% indicated significant respiratory depression in only 4/10 patients, with small absolute changes in SpO2% at 30 minutes. A decline in NRD from baseline to 30 minutes post IOT was also observed, but was not statistically significant. Baseline NRD and opioid-induced drop in SpO2% were inversely related. We conclude that significant acute respiratory depression is commonly induced by opioid drugs prescribed to treat opioid addiction. Hypoventilation is reliably detected by capnography, but not by SpO2% alone. Chronic suppression of NRD in the presence of underlying lung disease may be a risk factor for acute opioid-induced respiratory depression.

The impact of patients controlled analgesia undergoing orthopedic surgery

INTRODUCTION

The currently common musculoskeletal disorders have been increasingly treated surgically, and the pain can be a limiting factor in postoperative rehabilitation.

RATIONALE

Patient controlled analgesia (PCA) controls pain, but its adverse effects can interfere with rehabilitation and in the patient discharge process. This study becomes important, since there are few studies evaluating this correlation.

OBJECTIVES

To compare the outcomes of patients who used and did not use patient controlled analgesia in postoperative orthopedic surgery with respect to pain, unscheduled need for O2 (oxygen), and time of immobility and in-hospital length of stay.

METHODS

This is an observational, prospective study conducted at Hospital Abreu Sodré from May to August 2012. The data was daily obtained through assessments and interviews of patients undergoing total hip arthroplasty (THA) and total knee arthroplasty (TKA), thoracolumbar spine arthrodesis (long PVA), cervical spine arthrodesis (cervical AVA) and lumbar spine arthrodesis (lumbar PVA).

RESULTS

The study showed some differences between groups, namely: the painful level was higher in the group undergoing lumbar PVA without PCA compared with the group with PCA (p=0.03) and in the group of long PVA without PCA in the early postoperative period. This latter group used O2 for a longer time (p=0.09).

CONCLUSION

In this study, PCA was useful for analgesia in patients undergoing lumbar PVA and probably would have influenced the usage time of O2 in the group of long PVA in face of a larger sample. The use of PCA did not influence the time of leaving the bed and the in-hospital length of stay for the patients studied.

Cardiorespiratory complications of neuraxial opioids in patients with obstructive sleep apnea: a systematic review

We sought to determine the rate of cardiorespiratory complications following neuraxial opioid administration in the setting of obstructive sleep apnea (OSA). This systematic review of the leading biomedical databases originated from a university-affiliated, tertiary-care teaching hospital. A systematic search of Medline, Embase, Cochrane Central Register of Controlled Trials, Cochrane Database of Systematic Reviews, and the International Pharmaceutical Abstracts Database (1970 - September 2011) was undertaken. Cardiorespiratory complications were stratified into minor and major based on existing OSA literature. Five studies, including a total of 121 patients, were selected for analysis. All studies comprised low-quality evidence. Six major cardiorespiratory complications were reported among 5 (4.1%) patients and included three deaths, one cardiorespiratory arrest, and two episodes of severe respiratory depression. Five of these complications occurred during continuous fentanyl-containing epidural infusions and without concurrent positive airway pressure treatment. The rate of cardiorespiratory complications following the administration of neuraxial opioids to surgical patients with OSA is difficult to determine.

Transcutaneous carbon dioxide levels and oxygen saturation following caesarean section performed under spinal anaesthesia with intrathecal opioids

BACKGROUND

Intrathecal opioids can be associated with respiratory depression which may have serious consequences. We describe the use of a non-invasive monitor (TOSCA) to measure transcutaneous carbon dioxide levels and percentage of haemoglobin oxygen saturation in post-caesarean section patients in two hospitals which used different intrathecal opioids.

METHODS

Eighty-nine women undergoing caesarean section were monitored postoperatively until 08.00h on the first postoperative day. In addition to hyperbaric bupivacaine, patients from Hospital 1 received intrathecal diamorphine 300μg: those from Hospital 2 received intrathecal fentanyl 15μg and postoperative intramuscular morphine 10mg and were given morphine patient-controlled analgesia. Data from TOSCA were analysed the following day. Respiratory depression was defined as oxygen saturations <90% or transcutaneous carbon dioxide levels >7kPa for >2min or the need for medical intervention for clinical respiratory depression.

RESULTS

Sustained hypercapnia was recorded in 8/45 (17.8%) patients from Hospital 1 and 3/44 (6.8%) from Hospital 2. Sustained oxygen saturations <90% were recorded in one patient from Hospital 2 and none from Hospital 1. The overall incidence of respiratory depression was 17.8% in Hospital 1 and 9.1% in Hospital 2. The median duration of hypercapnia was 9min [IQR 5.8-12.4] in Hospital 1 and 11.5min [IQR 7-32.8] in Hospital 2. No patient required medical intervention.

CONCLUSIONS

The incidence of opioid-induced respiratory depression detected by TOSCA is higher than previously reported by other monitoring methods. TOSCA may have a role in detecting subclinical respiratory depression in the obstetric population. Further studies with a control population are needed.

Evaluation of a transcutaneous carbon dioxide monitor in patients with acute respiratory failure

BACKGROUND

Non-invasive measurement of oxygenation is a routine procedure in clinical practice, but transcutaneous monitoring of PCO(2)(PtCO(2)) is used much less than expected.

METHODS

The aim of our study was to analyze the value of a commercially available combined SpO(2)/PtCO(2) monitor (TOSCA-Linde Medical System, Basel, Switzerland) in adult non-invasive ventilated patients with acute respiratory failure. Eighty critically ill adult patients, requiring arterial blood sample gas analyses, underwent SpO(2) and PtCO(2) measurements (10 min after the probe was attached to an earlobe) simultaneously with arterial blood sampling. The level of agreement between PaCO(2) - PtCO(2) and SaO(2) - SpO(2)was assessed by Bland-Altman analyses.

RESULTS

Both, SaO(2) from blood gas analysis and SpO(2) from the transcutaneous monitor, and PaCO(2) and PtCO(2) were equally useful. No measurements were outside of the acceptable clinical range of agreement of ± 7.5 mmHg.

CONCLUSIONS

The accuracy of estimation of the TOSCA transcutaneous electrode (compared with the "gold standard" blood sample gas analysis) was generally good. Moreover, TOSCA presents the advantage of the possibility of continuous non-invasive measurement. The level of agreement of the two methods of measurement allows us to state that the TOSCA sensor is useful in routine monitoring of adults admitted to an intermediate respiratory unit and undergoing non-invasive ventilation.

Opioids, Ventilation and Acute Pain Management

Despite the increasing use of a variety of different analgesic strategies, opioids continue as the mainstay for management of moderate to severe acute pain. However, concerns remain about their potential adverse effects on ventilation. The most commonly used term, respiratory depression, only describes part of that risk. Opioid-induced ventilatory impairment (OIVI) is a more complete term encompassing opioid-induced central respiratory depression (decreased respiratory drive), decreased level of consciousness (sedation) and upper airway obstruction, all of which, alone or in combination, may result in decreased alveolar ventilation and increased arterial carbon dioxide levels.

Concerns about OIVI are warranted, as deaths related to opioid administration in the acute pain setting continue to be reported. Risks are often said to be higher in patients with obstructive sleep apnoea. However, the tendency to use the term ‘obstructive sleep apnoea’ to encompass the much broader spectrum of sleep- and obesity-related hypoventilation syndromes and the related misuse of terminology in papers relating to obstructive sleep apnoea and sleep-disordered breathing remain significant problems in discussions of opioid-related effects.

Opioids given for management of acute pain must be titrated to effect for each patient. However, strategies aiming for better pain scores alone, without highlighting the need for appropriate monitoring of OIVI, can and will lead to an increase in adverse events. Therefore, all patients must be monitored appropriately for OIVI (at the very least using sedation scores as a ‘6th vital sign’) so that it can be detected at an early stage and appropriate interventions triggered.

Respiratory complications of obesity

Obesity, well known as a cardiovascular risk factor, can also lead to significant respiratory complications. The respiratory changes associated with obesity extend from a simple change in respiratory function, with no effect on gas exchange, to the more serious condition of hypercapnic respiratory failure, characteristic of obesity hypoventilation syndrome. More recently, it has been reported that there is an increased prevalence of asthma which is probably multifactorial in origin, but in which inflammation may play an important role. Hypoventilation in the obese subject is the result of complex interactions that involve changes in the ventilatory mechanics and anomalies in breathing control. Two other conditions (COPD and sleep apnea-hypopnea syndrome [SAHS], often present in obese patients, can trigger or aggravate it. The prevalence of hypoventilation in the obese is under-estimated and the diagnosis is usually established during an exacerbation, or when the patient is studied due to suspicion of SAHS. Ventilatory management of these patients includes either CPAP or NIV. The choice of one or another will depend on the underlying clinical condition and whether or not there is another comorbidity. Both NIV and CPAP have demonstrated their effectiveness, not only in the control of gas exchange, but also in improving the quality of life and survival of these patients.

Recent advance in patient monitoring

Recent advance in technology has developed a lot of new aspects of clinical monitoring. We can monitor sedation levels during anesthesia using various electroencephalographic (EEG) indices, while it is still not useful for anesthesia depth monitoring. Some attempts are made to monitor the changes in sympathetic nerve activity as one of the indicators of stress, pain/analgesia, or anesthesia. To know the balance of sympathetic and parasympathetic activity, heart rate or blood pressure variability is investigated. For trend of cardiac output, low invasive monitors have been investigated. Improvement of ultrasound enables us to see cardiac structure and function continuously and clearer, increases success rate and decreases complication of central venous puncture and various kinds of nerve blocks. Without inserting an arterial catheter, trends of arterial oxygen tension or carbon dioxide tension can be monitored. Indirect visualization of the airway decreases difficult intubation and makes it easier to teach tracheal intubation. The changes in blood volume can be speculated non-invasively. Cerebral perfusion and metabolism are not ordinary monitored yet, but some studies show their usefulness in management of critically ill. This review introduces recent advances in various monitors used in anesthesia and critical care including some studies of the author, especially focused on EEG and cardiac output. However, the most important is that these new monitors are not almighty but should be used adequately in a limited situation where their meaning is confirmed.

In-hospital resuscitation: opioids and other factors influencing survival

PURPOSE

"Code Blue" is a standard term used to alertt hospital staff that a patient requires resuscitation. This study determined rates of survival from Code Blue events and the role of opioids and other factors on survival.

METHODS

Data derived from medical records and the Code Blue and Pharmacy databases were analyzed for factors affecting survival.

RESULTS

During 2006, rates of survival from the code only and to discharge were 25.9% and 26.4%, respectively, for Code Blue events involving cardiopulmonary resuscitation (CPR; N = 216). Survival rates for events not ultimately requiring CPR (N = 77) were higher, with 32.5% surviving the code only and 62.3% surviving to discharge. For CPR events, rates of survival to discharge correlated inversely with time to chest compressions and defibrillation, precipitating event, need for airway management, location and age. Time of week, witnessing, postoperative status, gender and opioid use did not influence survival rates. For non-CPR events, opioid use was associated with decreased survival. Survival rates were lowest for patients receiving continuous infusions (P < 0.01) or iv boluses of opioids (P < 0.05).

CONCLUSIONS

One-quarter of patients survive to discharge after a CPR Code Blue event and two-thirds survive to discharge after a non-CPR event. Opioids may influence survival from non-CPR events.

Improvement in accuracy of transcutaneous measurement of oxygen with resumption of spontaneous ventilation in mechanically ventilated patients after off pump coronary artery bypass procedure: a prospective study

INTRODUCTION

Transcutaneous measurement of gases depends on the degree of skin perfusion. Mechanical ventilation causes alteration in the peripheral perfusion. The aim of this prospective observational study was to assess change in the accuracy of interchangeability of arterial blood gases with those obtained transcutaneously at various phases of mechanical ventilation such as controlled mandatory, synchronized intermittent mandatory, continuous positive airway pressure ventilations, spontaneous breathing trail and spontaneous ventilation after extubation of endotracheal tube.

METHODS

Thirty-two adult patients who underwent uncomplicated off pump coronary artery bypass surgery in a tertiary care medical center were subjected to transcutaneous measurements of gases from the sensor placed on the chest during postoperative ventilation. Arterial blood gas analysis was performed at predetermined time intervals and transcutaneous measurements were repeated each of those time.

RESULTS

Fifty-four sets of data were obtained during controlled ventilation and fifty during spontaneous. Correlation coefficient for oxygen increased from 0.46 (P = 0.0004) during controlled ventilation to 0.75 (P < 0.0001) during spontaneous. Bland-Altman and mountain plots suggested better inter- changeability of values between arterial blood gas and transcutaneous gas monitoring. The bias for oxygen changed from 21 during controlled ventilation to 25 during spontaneous ventilation and the precision from 7.1 to 6.4. There was no change in the accuracy of transcutaneous carbon dioxide values during either phase of ventilation.

CONCLUSION

The accuracy of transcutaneously measured values of oxygen improved significantly during spontaneous ventilation.

Transcutaneous carbon dioxide monitoring in infants and children

OBJECTIVE

To review the technology required for and the applications of transcutaneous carbon dioxide (TC-CO2) monitoring in infants and children.

DATA SOURCE

A computerized, bibliographic search regarding the applications of transcutaneous carbon dioxide (TC-CO2) monitoring in infants and children.

RESULTS

Although the direct measurement of P(a)CO2 remains the gold standard, it provides only a single measurement of what is often a rapidly changing and evolving clinical picture. Given these concerns, there remains a clinical need for a means to continuously monitor P(a)CO2 without the need for repeated blood gas analysis. Although initially introduced into the neonatal intensive care unit; with improvements in the technology, TC-CO2 monitoring can now be used in infants, children and even adults. When compared with end-tidal carbon dioxide (ET-CO2) monitoring techniques, TC-CO2 monitoring has been shown to be equally as accurate in patients with normal respiratory function and more accurate in patients with shunt or ventilation-perfusion inequalities. TC-CO2 monitoring can be applied in situations that generally preclude ET-CO2 monitoring such as high frequency ventilation, apnea testing, and noninvasive ventilation. TC-CO2 monitoring has also been used in spontaneously breathing children with airway and respiratory issues such as croup and status asthmaticus as well as to monitor metabolic status during treatment of acidosis related to diabetic ketoacidosis.

CONCLUSIONS

Transcutaneous carbon dioxide monitoring may be a useful adjunct in various clinical scenarios in infants and children. It should be viewed as a complimentary technology and may be used in combination with ET-CO2 monitoring.

The effects of different analgesic regimens on transcutaneous CO2 after major surgery

Ventilatory impairment may be detected by a rise in transcutaneous carbon dioxide levels (PtcCO(2)). This observational study assessed the clinical utility of PtcCO(2) monitoring in the postoperative period, and quantified the effect of different peri-operative analgesic regimens on postoperative respiratory function. Following pre-operative baseline PtcCO(2) recording, continuous PtcCO(2) monitoring was performed in 30 patients after major colorectal surgery for up to 24 h. Mean postoperative values of PtcCO(2) were 1.3 kPa (95% CI 1.0-1.5) higher than pre-operative values (p < 0.001). Patients receiving intravenous opioid patient controlled analgesia had a significantly higher elevation in postoperative PtcCO(2) compared to patients receiving epidural infusion analgesia, 1.8 kPa (CI 1.5-2.1) vs 0.7 kPa (CI 0.5-0.9) respectively (p < 0.001). The mean rise in PtcCO(2) following a single intravenous bolus of morphine delivered via PCA was 0.05 kPa (SEm 0.01), peaking at 12 min post-dose. The transcutaneous capnometer successfully recorded data for 98% of the total time it was applied to patients.

Assessment, physiological monitoring, and consequences of inadequately treated acute pain

Postoperative pain is a major health care issue. Several factors have contributed to inadequate postoperative pain control, including a lack of understanding of preemptive pain management strategies, mistaken beliefs and expectations of patients, inconsistencies in pain assessment practices, use of as-needed analgesics that patients must request, and lack of analgesic regimens that account for interindividual differences and requirements. Untreated acute pain has the potential to produce acute neurohumoral changes, neuronal remodeling, and long-lasting psychologic and emotional distress and may lead to prolonged chronic pain states. To effectively manage postoperative pain, nurses must be able to adequately assess pain severity in diverse patient populations, understand how to monitor physiologic changes associated with pain and its treatment, be prepared to address the psychosocial experiences accompanying pain, and know the consequences of inadequate analgesia. It is important for nurses to be aware of relevant research and evidence-based guidelines that are available to guide pain assessments and patient monitoring practices.

Assessment, physiological monitoring, and consequences of inadequately treated acute pain

Postoperative pain is a major health care issue. Several factors have contributed to inadequate postoperative pain control, including a lack of understanding of preemptive pain management strategies, mistaken beliefs and expectations of patients, inconsistencies in pain assessment practices, use of as-needed analgesics that patients must request, and lack of analgesic regimens that account for inter-individual differences and requirements. Untreated acute pain has the potential to produce acute neurohumoral changes, neuronal remodeling, and long-lasting psychological and emotional distress, and may lead to prolonged chronic pain states. To effectively manage postoperative pain, nurses must be able to adequately assess pain severity in diverse patient populations, understand how to monitor physiological changes associated with pain and its treatment, be prepared to address the psychosocial experiences accompanying pain, and know the consequences of inadequate analgesia. It is important for nurses to be aware of relevant research and evidence-based guidelines that are available to guide pain assessments and patient-monitoring practices.