Transcutaneous Oxygen Monitoring of Patients

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					                 Transcutaneous                      Oxygen        Monitoring of Patients
               Undergoing Surgical                               Removal of Wisdom Teeth
                                 Utilizing            GENERAL ANESTHESIA

                                                     Richard A. Kraut, D. D. S.*

   Ambulatory general anesthesia is commonly used                     various intravenous sedation techniques are utilized
to control pain and anxiety during surgical removal                   during surgical removal of wisdom teeth."
of wisdom teeth.' 2 A recent report of over 5,000                        The interference of anesthetic gases with transcu-
naso-endotracheal intubations for outpatient anes-                    taneous oxygen sensors has been investigated by
thesia at Ohio State University, indicated their tech-                Eberhard and Mindt who have shown that, with a
nique to be "relatively free of significant complica-                 "large size cathode (mm range) and a membrane with
tions".3 The most recent survey performed by                          low permeability for oxygen such as mono-axially
Southern California Society of Oral and Maxillofa-                    oriented polyethylene", there is less than a 5% re-
cial Surgeons, indicates that members of that Society                 duced reading due to nitrous oxide.'2 Their data also
performed about 257,000 general anesthetics per                       indicated that enflurane concentrations of 2% do not
year, from 1973-1978, without a single death.' The                    produce any measurable interference with the trans-
Oral and Maxillofacial Surgery Residency Program                      cutaneous oxygen sensor described above, as long
at Brooke Army Medical Center continues to use                        as a polarization voltage of - 600mV was used. These
the spontaneous-ventilation general anesthesia tech-                  findings confirm the previous work of Marshall, et
nique described by Schow, et al.4We have completed                    al., who demonstrated the usefulness of transcuta-
over 1100 cases utilizing this technique without a                    neous oxygen monitoring in neonates during sur-
significant anesthetic complication. The effects of                   gery.13
spontaneous enflurane general anesthesia on the PO2                      The establishment of the validity of transcutaneous
of patients undergoing oral surgery has not been                      oxygen monitoring in adults, as well as understand-
studied in the past, due to the inability to monitor                  ing the effects of nitrous oxide and enflurane on
P02 noninvasively.                                                    transcutaneous oxygen monitoring, led to the use
   Surface electrodes for monitoring partial pressure                 of this technique to monitor patients undergoing
of oxygen in neonatal and pediatric patients have                     surgical removal of wisdom teeth. This study was
been commercially available since 1975.5 Recent                       designed to determine the changes in partial pressure
equipment modification has made transcutaneous                        of oxygen experienced by patients having wisdom
oxygen monitoring possible in adults. The initial                     teeth removed under general anesthesia.
confusion that occurred when transcutaneous P02
(PtO2) and arterial P02 (PaO2) values differed has now                Method
been thoroughly investigated and resolved.6The the-                      Twenty-six consecutive ASA I adult patients who
oretical basis of transcutaneous blood gas measure-                   requested general anesthesia in association with re-
ments, as well as the variety of physiological param-                 moval of their impacted wisdom teeth constituted
eters that can result in differences in the PtO2 and                  the study group. The patients were informed of pos-
PaO2, are now understood.6789 Although different                      sible risks and signed an institutionally approved
from the PaO2, the PtO2 correlates with the PaO2 in                   consent from prior to being enrolled in this study.
hemodynamically stable adults.679 '' Schachter, et                    A complete history and physical examination, in-
al., concluded that PtO2 monitoring is a valuable                     cluding a CBC and UA, were performed 48 hours
trend indicator that allows observation of acute                      prior to surgery. The patients were advised to refrain
changes associated with the cardiovascular system.8                   from eating or drinking for eight hours prior to their
Significant changes in PtO2 have been reported where                  surgical appointment.
                                                                         On the morning of surgery, the patients changed
                                                                      into hospital clothing and were seated in a semi-
*Lielutenuant Colonel, DC, and Chief, Oral and NMaxillofacial Stur-   supine position in a contoured dental chair with their
gery Service, Brooke Army Medical Center, Fort Sam Houstonl,          back, neck and head inclined 30° from the floor and
Texas 78234                                                           their legs elevated. The following monitors were
  The opinions or assertionis contained herein are the private        connected prior to the induction of anesthesia:
views of the author and are not to be construed as reflecting the     transcutaneous oxygen monitor, electrocardi-
views of the Department of the Armv or Department of Defense.         ograph, pneumotachygraph, automatic hands-off
  This research project was stupported bv an outreach granit from     blood pressure monitor and a precordial stetho-
USAI1DR.                                                              scope. An intravenous line was established with an
132                                                                                                ANESTHESIA PROGRESS
18 gauge intracath using 5% dextrose in lactated          tween 90 and 150 mmHg. A segment of the patients
Ringer's solution. A .4 mg dose of atropine, 8 mg         showed a marked rise in PtO2 when the enflurane
of dexamethasone and a 3 rug defasciculating dose         and nitrous oxide were discontinued at the termi-
of curare were administered intravenouslv. A full face    nation of surgery (Figure 1). A second gr-oup re-
mask was used to oxygenate the patient with 100%          tained the level of PtO2 they had established during
oxygen for 60 seconds. Induction was accomplished         surgery, in spite of receiving 100% oxvgen via the
with 100 mg of methohexital, relaxation with 100 mg       endotracheal tube, which was still in place. This
of succinylcholine. The patient's vocal cords were        second group met the extubation re(quirement of
exposed with a laryngoscope and an LTA Kit was            responding to the verbal command to open their
utilized to aniestlhetize the trahelaea and an oral en-   eyes. They were extubated and had uneventful
dotracheal tul)e was place(l. After verification of       recovery periods.
e(ual l)reath sotIn(ls b)ilaterally, the patienit w%as       Repeated measurements analvsis of variance was
started on 70% nitrous oxide. :30% oxvgen and(i 1 .55%    performed. Two different group means emerged.
enflurane, delivered through an enflurane vaporizer       The two groups did not behave the same wav across
and a Bain anesthetic circuit with a fresh gas flow of    time. The group time interaction of the two group
100 cc per kilogram per minute.                           means are significantly different, P < .001. Group A
   Two percent lidocaine with 1:100,000 epinephrine       consisted of 15 patients, 11 males and four females.
was utilized to anesthetize the operative sites. A        Group B consisted of nine patients, three males and
throat pack was placed and the patient maintained on      six females. There was one male and one female
70% nitrous oxide and 30% oxygen throughout the           whose PtO2 values were between Group A and B;
surgical procedure. The percentage of enflurane was       their records are excluded froimn Figure 1, for the
continuallv reduced during the surgery to as low a        sake of claritv. Groups A and B differ starting with
level as possible, consistent with the patient's vital    pre-induction oxygenation and remain different,
signs and maintenance of a favorable operating en-        though parallel, until the end of surgerv when Group
vironment. During the removal of the last tooth,          A showed a 150 mm rise in PtO2 while Group B failed
the enflurane was discontinued and the patient main-      to show an increase in PtO2, in the face of 100%
tained on 70% nitrous oxide, 30% oxygen for the           oxvgen administered via an endotracheal tube. The
last few minutes of surgery. When surgery was com-        emergence of two distinct groups led to a review of
pleted, the patient was placed on 100% oxygen until       all records in an effort to discern what factors place
they were able to respond to a verbal command to          a patient in Group A or Group B. The records were
open their eyes. At that time, the patient was extu-      audited for RBC, hemoglobin, hematocrit, height/
bated and recovered in the Oral and Maxillofacial         weight ratio, smoking historv, use of medication,
Surgery recovery area, until they were ready for          previous anesthetic exposure, scheduled time of sur-
discharge to the care of their escort.                    gery, length of surgery, fluctuation of blood pres-
   The Roche Model 5302 Cutaneous Oxygen Mon-             sure and/or pulse, as well as sexual makeup of each
itor was used on all patients in this study. The sensor   group. All of the audited criteria failed to separate
was applied at the left midclavicular line 3 cm below     Group A and B.
the clavicle and heated to 45°C. This sensor uses a
large size cathode, a mono-axially oriented polyeth-      Discussion
ylene membrane and is polarized to -600mV. The               There are multiple factors that affect the PO,, some
oxygen monitor's recorder was used to generate a          of which are: the functional capabilities of the lung,
permanent record of each patient's PtO2 from the          the volume of the lung, the amount of alveolar- ven-
time the sensor was placed until after extubation.        tilation, the concentration of oxvgen in inhaled gases
                                                          (FiO2), the oxyhemoglobin disassociation curve,
Results                                                   age, the barometric pressure, the partial pressure of
   The study group consisted of 15 males ranging in       the alveolar oxygen concentration and the perfusioni
age from 18 to 34 with a mean of 22.33 years and 11       of the lungs. ' '' In dealing with ASA I patients, all
females ranging in age from 18 to 24 with a mean of       being treated with identical anesthetic teclhnique, in
20.45 years. All 26 patients tolerated the anesthesia     the same operating room bv the same anestlhetic
and surgery without complication. Surgical time           team, it is surprising to see the emergency of two
ranged from eight minutes to 30 minutes with 15           distinct patient populations.
minutes as the median and a mean of 15.8 minutes.            Churchill-Davidson list numerous pre, intra an(l
All patients were able to open their eyes on com-         postoperative factors that mav cause hvpoxia.'" Re-
mand and were extubated within two minutes of             view of anesthetic records, as well as history anid
completion of surgery.                                    physical examinations, failed to disclose anyv factors
   Initial inspection of the PtO2 indicated a marked      known to contribute to relative hvpoxia during geni-
rise during the pre-induction oxygenation period,         eral anesthesia. The fact that Group A and B differ
as well as during the controlled ventilation period       from the pre-intubation phase of the anesthetic, pre-
surrounding intubation. While breathing sponta-           cludes diffusion anoxia as the giroup discriminator.'
neously, the patients arrived at a plateau PtO2 be-          Upon completion of the 26 patients reported in
SEPT/OCT. 1982                                                                                               1:3:3
this study, we have continued to use transcutaneous                                         2. Gelfman S S Driscoll E J Thrombophlebitis following intra-
oxygen monitoring while administering general                                                  venous anesthesia and sedation: An annotated literature re-
                                                                                               view. Anesth Prog 24:194-197 1977.
anesthesia. We continue to see two distinct patient
groups; however, we are still unable to determine                                           3. Gontv A A Racey G L Nasal endotracheal intubation for out-
what it is that separates patients into these groups.                                          patient anesthesia. J Oral Surg 38:191-195 1980.
                                                                                            4. Schow S R Shelton D W WVatson R L Spontaneous-ventila-
                                                                                               tion general anesthesia for outpatients using enflurane. J Oral
                                                                                               Surg 37:840-844 1979.
  390        Group A-----         Group B-
                                                                                            5. McDowell J W Thiede W H Usefulness of the transcutanieous
0 330             ,                                                                            PO2 monitor during exercise testing in adults. Chest 78:853-
   300                                                                                         855 1980.2
= 270                                                                         / /
                                                                                            6. Lubbers D W Theoretical basis of the transcutaneous blood
v) 18+:                     %       ,                                                          gas measurements. Crit Care Med 9:721-733 1981.
   ISOt               +..-                                                                  7. Eberhard P NMindt W Shafer R Cutaneous blood gas monii-
  60                                    50-------------                                        toring in the adult. Crit Care Med 9:702-705 1981.
                                                                                            8. Schachter E N et al. Transcutaneous oxygen and carbon diox-
   60                                                                                          ide monitoring. Arch Surg V 116:1193-1196 1981
   30                                                                                       9. Shoemaker W C Vidvasagar D Physiological and clinical sig-
          L~~~~~~~~~~~            I     ,I,,,//
             2   3 4 5      6 7    8 9 10 11 12 13 14         5" 16 17 18 19 20 21 22 23       nificance of PtcO, and PtcCO2 measurements. Crit Care NIed
                                                                                               9:689-690 1981.
                                             TIME (minutes)

                                        Figure 1                                           10. Tremper K K et al. Continuous transcutaneous oxygen mon-
                                                                                                 itoring during respiratory failure, cardiac decompensation,
Meani transcultanieouis P02 (PtO2) measured during surgical removal                              cardiac arrest and CPR. Crit Care Med 8:377-381 1980.
of wisdom teeth. All patients were intubated four minutes after                            11.   Kraut RA Transcutaneous oxygen monitoring of patients
the start of oxygenation. The time line is suspended between 15                                  undergoinig surgical removal of wisdom teeth. Anesth Prog
and 16 minutes. Anesthetics running longer than 23 minutes are                                   3:70-71 1982.
graphed with 16 minutes being four minutes prior to extubation.                            12.   Eberhard P Mindt W Interference of anesthetic gases at skin
                                                                                                 surface sensors for oxvgen and carbon dioxide. Crit Care
                                                                                                 Med 9:717-720 1981.
   The auithor wishes to express his appreciation to                                       13.   Marshall TA Kattwinkel J Berrv FA Shaw A Transcutaneous
LTC Arthur L. Badgett and Mr. Vondal Hutchins of                                                 oxygen monitoring of neonates during surgery. J Pediatr Surg
Patient Administration Systems and Biostatistics Ac-                                             15(6):797-804 1980.
tivity of the USA Health Services Command for per-                                         14.   Wilson R F Principles and techniques of critical care. Kala-
forming statistical analysis of the data generated in                                            mazoo, Michigan, Upjohn 1970 Sect f p. 30.
this study.                                                                                15.   Kirby R R Respiratory vs cardiovascular dysfunction - how
                                                                                                 can we differentiate? Am Society of Anesth Refresher Course
                       BIBLIOGRAPHY                                                              Lect 1980 Lect 102 p. 1-7.
1. Lytle J J Yoon C 1978 Anesthesia morbidity and mortality                                16.   Wvlie W D Churchill-Davidson H C A practice of anesthesia.
   survev: Southern Califonria society of oral and maxillofacial                                 ed 4 Philadelphia W B Saunders Co. 1978 p. 187-188.
   surgeonis. J Oral Surg 38:814-819 1980.                                                 17.   Fink B R Diffusion Anoxia. Anesthesiology 16:511-519, July

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134                                                                                                                             ANESTHESIA PROGRESS

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