562
peritoneum and patient position on cardiac performance
during laparoscopic cholecystectomy. This was done via a
noninvasive transthoracic bioimpedance monitor.
Table 1. Demographic data
ASA I & II
ASA III
Total
Patients (n)
30
7
37
Age (yr)
48.7 ± 13.6
66.5 ± 10.1
7 (18.9%)
6
1
52.1 ± 14.7
7 (18.9%)
34 (91.9%)
4 (8.1%)
69.8 ± 21.8
Cardiac history
Female patients (n)
Male patients (n)
Operating time (min)
0
28
3
Materials and methods
Patients
The study was conducted at the Mary Imogene Bassett Hospital, a 180-bed
community teaching hospital in a rural setting. All patients admitted for
laparoscopic cholecystectomy by a single surgeon were eligible for enroll-
ment over a 7-month period. The protocol was approved by the hospital’s
Institutional Review Board, and informed consent was obtained. Prior to
the procedure, each patient completed a short questionnaire targeting car-
diac comorbidities, exercise tolerance, and current medications. Patients
were excluded if they were under 18 years of age or unable to provide
informed consent for the study.
ately prior to each of these five events; thus, each patient was observed at
11 event levels.
Changes in measurements of —HR, CI, SV, and LVEDV—over the 11
event levels were compared between the two ASA (American Society of
Anesthesiologists) strata (classes I and II vs class III) using two by 11
mixed analysis of variance (ANOVA).
In this model, the main effect for event and the interaction of event by
ASA stratum constituted within-subject effects, with the main effect of
ASA stratum being a between-subjects effect. Type III sum of squares was
used for all analysis. The nature of any significant main effects was ex-
plored further through post hoc pairwise comparisons (Scheffe’s test). If
significant interaction effects were present, they were explored further
through graphic methods to clarify whether the interaction was of an or-
dinal or disordinal nature.
Anesthesia
A standard balanced anesthesia protocol comprised of propofol (2 mg/kg),
fentanyl (2–3 g/kg), flurane, and vecuronium (0.1 mg/kg) was used.
Anesthesia was titrated to maintain heart rate and blood pressure within
2
0% of baseline. Ventilation was adjusted to maintain end-tidal carbon
dioxide (CO ) at 34–35 mmHg. Inotropic agents and/or beta-blockers were
used if deemed absolutely necessary.
2
Results
Forty-one patients were initially enrolled in the study. Data
for four patients could not be retrieved from the IQ monitor.
The demographic data of the 37 patients included in the
study are summarized in Table 1. The mean age was 52 ± 14
years (range, 28–77). The ASA class III patients were older
and had some type of cardiac comorbidity (hypertension,
prior myocardial infarction (MI), or coronary artery bypass
grafting (CABG). The majority of patients (91.9%) were
women. Mean operative time was 69.8 ± 21.8 mins. There
were no adverse perioperative cardiac events.
Technique
Each patient was connected to an IQ transthoracic bioimpedance monitor
via two pairs of bifunctional electrodes (Renaissance Technologies, New-
town, PA, USA) in the preanesthesia area by one of two technicians.
Patients were then brought to the operating room, and a baseline set of
hemodynamic measurements was obtained with the patient supine prior to
the induction of anesthesia. Blood pressure was obtained via arm cuff.
After the induction of anesthesia, laparoscopic cholecystectomy was
performed via the standard four-trocar technique. Insufflation of the abdo-
men with CO2 was maintained at a pressure of 15 mmHg (Stryker, San
Diego, CA, USA). The reverse Trendelenburg position was standardized at
an angle of 30°. A Foley catheter was not used. At the end of each pro-
cedure, the patient was monitored with the IQ in the recovery room for a
period of 30 min.
The hemodynamic effects of anesthesia, insufflation of
the abdomen, and patient position are summarized in 5
2
Tables 2–5. CI (Table 2) was 3.48 L/min/m at baseline. It
2
decreased to 2.63 L/min/m (p ס
0.003) with induction of
anesthesia, as shown by the change from baseline to prein-
sufflation. Pneumoperitoneum further decreased CI to 2.42
2
Data collection
L/min/m (p ס
0.17), a nonsignificant decrease. Placing the
2
patient in RT position resulted in a CI of 2.34 L/min/m ,
which was not a significant change. Placing the patient back
in a flat position also did not significantly improve hemo-
The mean arterial pressure was measured every 5 min via arm cuff. Cardiac
index (CI), stroke volume (SV), mean left ventricular end diastolic volume
(LVEDV), and heart rate (HR) were measured continuously by the IQ
2
dynamics, as the preflat CI 2.84 L/min/m increased to 2.91
monitor. Data were specifically examined at the following events; baseline
prior to anesthesia, following induction of anesthesia, insufflation of CO2,
placement of the patient in reverse Trendelenburg position (RT), placement
of the patient in a flat position, and following the procedure in the recovery
room. To examine the impact of a specific event, data points were analyzed
2
L/min/m with this change. At the end of the case, the CI
2
returned to 3.20 L/min/m . Of note, patients accommodated
to the combined hemodynamic depression, as evidenced by
2
the increase in CI from 2.34 L/min/m with RT to 2.84
5
mins prior to and 5 mins after each event. After 10 mins in RT with
2
L/min/m (p ס
0.001) at the preflat reading. This change
pneumoperitoneum, each patient was placed in a flat position to reexamine
the specific effect of patient position. All data were collected on a floppy
disk at the end of each case and saved for analysis.
represents 30 mins of operating time in the RT position with
pneumoperitoneum.
The changes seen in SV (Table 3) and LVEDV (Table
) supported these findings. SV decreased significantly with
4
Statistical analysis
anesthesia from baseline 83.69 ml to 73.88 ml (p ס
0.007).
LVEDV did not change significantly from baseline 123.05
ml to 114.97 ml preinsufflation. Insufflation decreased SV
to 64.92 ml (p ס
0.009) and LVEDV to 102.06 ml (p ס
Prior to the start of the procedure, a baseline level consisting of the average
of the endpoint at three consecutive readings was obtained. Subsequently,
three consecutive readings were similarly averaged at induction, insuffla-
tion, reverse Trendelenberg, the flat position, and the conclusion of the
procedure. In addition, three consecutive readings were obtained immedi-
0
.01). RT did not produce any significant changes in either
parameter (SV, 63.87 ml and LVEDV, 104.30 ml). During