Capnography and Respiratory Depression - tri …

1 2008tVol. 108, No. 235 Capnography and Respiratory Depression Is Capnography a good way to monitor at-risk postsurgical patients?A prospective trial examines the depres-sion is an adverseevent usually associ-ated with high opi-oid doses inopioid-naive patients thosewho have not been takingopioids regularly but it mayalso occur with normal opioiddoses. A literature review bySmith found no consistent statis-tics on the prevalence of opioid-related adverse events inpostsurgical patients, with fig-ures ranging downward to one-tenth that sleep apnea(OSA), in which the upper air-way may, at intervals, becomepartly or completely occludedduring sleep, also places hospi-talized patients at higher risk forrespiratory complicationsbecause opioids can relax pha-ryngeal tone and increase theairway occlusion already foundin people with , 3 Epidemiologic data from adecade ago indicated a preva-lence of undiagnosed OSA of upto 5% in Western countries,4butbecause the rate of obesity, amajor risk factor for OSA, hasincreased since that time, theprevalence of OSA may now beeven higher than 5%.

2 Manypeople with OSA have neverbeen diagnosed with the condi-tion. In one study of patientsundergoing hip or knee replace-ment surgery, of 101patients with OSA were notdiagnosed with the conditionuntil after their surgery, and one-third of them suffered a sub-stantial Respiratory or cardiaccomplication. 2 Regardless of whether OSA ispresent, any postsurgical patientreceiving opioids for pain shouldbe routinely assessed for changesto the sedation level and respira-tion. This is usually done by directobservation of the sedation leveland the depth, regularity, and rateof respirations (see MonitoringSedation, Pain Control,February2002).

3 Pulse oximetry is some-times used in addition to assessrespiratory status. A pulse oximetermeasuresthe percentage of the patient shemoglobin that is saturatedwith oxygen; it consists of amonitor and sensor attached tothe patient s finger. But results ofpulse oximetry may be decep-tive, especially when the patientis receiving supplemental oxy-gen, because pulse oximetry maydetect a high enough level ofarterial oxygen saturation evenwhen the respiration , 6 Pulse oximetry doesnot detect changes in respirationrate, pauses in breathing, orexhaled carbon dioxide (CO2)levels, important early indicatorsof Respiratory Depression , anddeclining ventilation in patientson supplemental oxygen maynot be recognized until bradyp-nea progresses to apnea, whichcan lead to harm or even Capnography ,a nasal can-nula delivers supplemental oxy-gen andmeasures respiration,including exhaled CO2(alsoknown as end-tidal CO2), apneicevents (measured by a set thresh-old level, such as any pause inbreathing longer than 20 sec-onds), and Respiratory rate (meas-ured in breaths per minute).

4 Placing the Capnography moduleon the patient s face is similar toinitiating a nasal cannula for sup-plemental oxygen. Breath samplesare obtained through both nos-ControlBy Rob Hutchison, PharmD,and Les Rodriguez, MPH, RN, CPANO verview: In order to determine whether opioid-naive patientsat risk for Respiratory Depression are better monitored with eithercapnography or pulse oximetry and Respiratory -rate assessment,the authors conducted a randomized, prospective trial. In 54opioid-naive postoperative orthopedic patients at one hospital, Capnography resulted in greater detection of Respiratory depres-sion, and the authors conclude that Capnography may be moreappropriate for use with postsurgical high-risk patients takingopioids on the general care nursing unit.

5 Capnography s sensi-tivity in the detection of pauses in breathing in the sedatedpatient may have the added advantage of indicating thosepatients who may be at risk for obstructive sleep apnea. Furtherresearch is needed to confirm these most patients tolerateopioid analgesics without seriousadverse events on the generalcare nursing unit, studies of newtechnologies such as capnogra-phy should focus on patients athigh risk for opioid-inducedrespiratory Depression . We per-formed a randomized, prospec-tive trial of patients who ve hadorthopedic surgery and arereceiving opioids and are at riskfor OSA, in order to determinewhether Capnography alone is more sensitive than pulseoximetry with respiration rateassessment by observation orauscultation to detect pri-mary outcome measured wasrespiratory Depression : anepisode was defined as a respira-tory rate of six breaths perminute or fewer, an apneic eventlasting longer than 20 seconds,an end-tidal CO2level greaterthan 60 mmHg, or oxygen satu-ration less than 88%.

6 (The firsttwo of these could be measuredin both groups; of the latter two,end-tidal CO2level greater than60 mmHg could be measuredonly in the Capnography groupand oxygen saturation only inthe control group.) A secondary outcome meas-ured was pauses in breathingduring sleep, one of the risk fac-tors for moderate-to-severe OSAthat s listed in the 2006 AmericanSociety of AnesthesiologistsPractice Guidelinesfor thePerioperative Management ofPatients with Obstructive outcomes meas-ured were time in the postanes-thesia care unit (PACU), distanceambulated on the first postoper-ative day (as recorded by a phys-ical therapist)

7 , and morphineequivalent consumed (asrecorded for the 36 hours andconverted by a pharmacist tostandard parenteral morphineequivalence, using the criterialisted in Parenteral MorphineEquivalents,at left). The patients pain intensity (as measured on a0-to-10 pain-rating scale) wascollected during the three postop-erative time periods: in thePACU, the remainder of the first24 hours after surgery spent onthe general care nursing unit, andthe first full day after institu-tional review board approvalfrom Presbyterian Hospital ofDallas, 54 opioid-naive patientswho were consecutively admittedbetween October 2006 andJanuary 2007 for orthopedic sur-gery and who met inclusion crite-ria were enrolled in the studyand randomized in the PACU tothe Capnography group (n = 29)trils, and oxygen is deliveredthrough small pin holes.

8 Theextension in front of the mouthcan be used to obtain readings ifthe patient breathes through themouth instead of the Capnography typicallyrequires about 15 minutes of ini-tial staff education. For many years, capnographywas used primarily during sur-gery; more recently, monitorshave become more portable andpractical for use on the generalcare nursing unit. Emergencymedical technicians are alsobeginning to use it more use of Capnography outsidethe operating room is new andnot indicated for every determining factor is cost: isthe cost of purchasing, using,and maintaining a small numberof devices balanced against thecost of adverse events?

9 36 AJNtFebruary 2008tVol. 108, No. 2 Settings for the Alaris EtCO2 Capnography Module* End-tidal carbon dioxide: 60 mmHg (high), 0 mmHg (low) Respiratory rate: 40 breaths per minute (high), 6 breaths perminute (low) Apnea (no breathing): 20 seconds* All settings were established by the author; this is the firstreported randomized, prospective, controlled study of the use ofcapnography on general care Morphine Equivalents*Hydromorphone mg Fentanyl mg Hydrocodone PO10 mg Oxycodone PO20 mg Meperidine IV100 mg * All doses above are equivalent to morphine IV10 mg. Onthe day of surgery, the amount of parenteral morphine equiva-lent includes doses on the postanesthesia care unit and on themedical surgical unit.

10 Doses are based on single dose studiesand given over a 4-hour period. Ashburn MA, Lipman AG. Principles of Analgesia Use in the Treatment of AcutePain and Cancer ed. Glenview, IL: American Pain Society. 2008tVol. 108, No. 237then on the general care nursingunit for 36 hours by the clini-cians caring for the patients. RESULTS With regard to demographiccharacteristics (sex, age, bodymass index, opioid allergy, typeof orthopedic procedure, andlength of stay), there were nostatistically significant differencesbetween the two groups (seeTable 1, page 38). Respiratory Depression wasdetected at a significantly higherrate in the Capnography group (t test = ; P= ).