Journal of Pediatric Surgery VOL 25. NO 2

FEBRUARY 1990

Postoperative Analgesia in Children: A Prospective Study of Intermittent Intramuscular Injection Versus Continuous Intravenous Infusion of Morphine By Margo

Hendrickson,

Laura Myre,

Dale G. Johnson,

Michael

E. Matlak,

Richard E. Black, and John J. Sullivan

Salt Lake City, Utah 0 Few advancements in postoperative pain control in children have been made despite longstanding inadequacies in conventional intramuscular analgesic regimens. While overestimating narcotic complication rates, physicians often underestimate efficacious doses, nurses are reluctant to give injections. and many children in pain shy away from shots. This study prospectively focuses on the safety, efficacy, and complication rate of intermittent intramuscular (IM) versus continuous intravenous infusion (IV) of morphine sulfate (MS) in 46 nonventilated children following major chest, abdominal, or orthopedic surgical procedures. Twenty patients assigned to the IM group had a mean age of 6.17 years and a mean weight of 23.0 kg. Twenty-six patients assigned to the IV group had a mean age of 6.74 years and a mean weight of 27.4 kg. The mean IM MS dose was 12.3 ag/ kg/ h while the mean IV dose was 19.6 bglkglh (P < .ODl). Postoperative pain was assessed with a linear analogue scale from 1 to 10 (1, “doesn’t hurt”; 10, “worst hurt possible”) for 3 days following operation. Using the analysis of covariance (ANACOVA). nurse, parent, and patient mean pain scores in the IV group were significantly lower than those of the IM group when controlled for age, MS dose, and complications (P < .W7). Nurse assessment of pain correlated well with the patient and parent assessments (Pearson correlation coefficients > 0.6). Not only did IV infusion give better pain relief than IM injections, but there were no major complications such as respiratory depression. Minor complications in this study (nausea, urinary retention, drowsiness, vomiting, hallucinations, lightheadedness, and prolonged ileus) were not significantly different between IM and IV groups. Continuous IV morphine infusion is a safe and more effective means of postoperative pain control in children. D 1990 by W. B. Saunders Company.

INDEX WORDS: Postoperative infusion; intravenous morphine.

pain:

analgesia;

The reasons in children are several. Many children either cannot communicate their discomfort or they withdraw as a means of coping with pain. Others withhold complaints about pain because they fear injections? Physicians are often reluctant to give narcotics to children because injections are painful and because they fear narcotic side effects such as respiratory depression and addiction. Recently, the administration of continuous intravenous (IV) morphine sulfate (MS) has been reported to be successful and safe in relieving both postoperative pain and pain caused by terminal malignancy in children.“S16 The efficacy and complication rate of continuous IV MS versus conventional intermittent intramuscular (IM) injections on the routine surgical ward were compared in this study. Pain was assessed on a linear analogue scale by nurses, parents, and patients. MATERIALS

AND

METHODS

Study patients were limited to those with major chest, abdominal,

or orthopedic operations and who were also eligible for transfer to the surgical ward from the recovery room. Patients requiring ventilator support following operation were excluded from the study. After prior approval from our Institutional Review Board, subjects were randomized into the IM and IV groups. In the recovery room, a standardized order form for IV MS infusion was completed by the surgical housestaff. The weight (kg) of the patient was multiplied by 0.5 to establish the total amount of MS (mg) to be added to a 500 cc bottle of IV solution. This standardized the concentration of the MS

narcotic

T

HE TREATMENT of pain is one of the most important aspects of postoperative care rendered by a surgeon. Nevertheless, the optimum postoperative analgesic regimen remains controversial. Several studies have reported major inadequacies in postoperative pain control in adultsle6 and children.7W’0 Journal of Pediatric Surgery, Vol 25, No 2 (February). 1990: pp 185-191

From the Primary Children’s Medical Center and the Department of Surgery, University of Utah Health Sciences Center, Salt Lake City, UT. Presented at the 20th Annual Meeting of the American Pediatric Surgical Association, Baltimore, Maryland, May 28-31, 1989. Address reprint requests to Dale G. Johnson, MD. Primary Children’s Medical Center, 320 Twelfth Ave. Salt Lake City. UT 84103. 0 1990 by W.B. Saunders Company. 0022-3468/90/2502-0001$03.00/0

185

186

HENDRICKSON ET AL

infusion to 1 rg/kg/cc. A loading dose was often, but not always, given by the anesthesiologist in the operating room or the recovery room. The infusion was started when the patient arrived on the surgical ward, about 1 hour after operation. The initial rate was set between 20 cc/h (20 ng/kg/h) and 40 cc/h (40 wg/kg/h), amounts proven to be efficacious in children by Beasley and Tibballs” and Lynn et al.” The rate was then adjusted by the nursing staff between limits of 10 cc/h and 40 cc/h according to the pain response of the patient. A rate increase of 5 cc was allowed every 30 minutes until 40 cc/h was reached. A physician’s order was required for rates in excess of 40 cc/h. Children weighing less than 10 kg received an MS solution twice the standard concentration but infused at one half the rate to avoid fluid and electrolyte problems. Narcotic overdose was prevented by placing a volume limited burette in line with the IV bottle (Fig 1). A maximum of 50 cc (wt G 10 kg) or 100 cc (wt > 10 kg) was placed in the burette at any

MORPHINE INFUSION

VOLUME LIMITING BURETTE

INTRAVENOUS INFUSION PUMP

Table 1. Morphine

Compatibility

With Selected

Compatible

Medications Incompatible

Amikacin

Gentamicin

Chlorthiazide

Ampicillin

Glycopyrrolate

Haloperidol

Atropine

Heparin

Meperidine

Carbenicillin

Hydrocortisone

Methicillin

Cefamandoie

Hydroxyzine

Pentobarbital

Cefazolin

Metoclopramide

Phenobarbital

Cefotaxima

Nafcillin

Phenytoin

Cefoxitin

Penicillin

Sodium bicarbonate

Ceftizoxime

Potassium chloride

Cefuroxime

Promethazine

Cephalothin

Scopolamine

Chloramphenicol

Ticarcillin

Chlorpromazine

Tobramycin

Cimetidine

Bactrim/Septra

Clindamycin

Vancomycin

one time. If an accidental bolus was delivered by the infusion pump, the patient would receive only a maximum dose of 0.1 mg/kg. This represents a safe amount for IV injection and is the total amount delivered by a standard IM injection. Additional safety measures included electrocardiogram (ECG) monitoring plus bag and mask resuscitation equipment kept at the bedside. A vial of naloxone (a MS antagonist), with the dose calculated for each patient, was kept at the bedside throughout the duration of MS infusion. Morphine infusion is compatible with crystalloid solutions and total parenteral nutrition. The MS infusion can also be added to or run in line with many medications. Drugs that are compatible or incompatible with morphine are listed in Table 1. The comparison group of patients received IM injections of 0.1 mg/kg MS on a as needed basis every 3 hours. Pain was assessed on a linear analogue scale.“,‘* This consisted of a IO-inch horizontal line with an unlabeled mark at every one inch interval. “Doesn’t hurt” was printed on the left end and “worst hurt possible” was printed on the right end of the scale. The nurse, parent, and patient indicated the amount of pain experienced by the patient by pointing to a mark on the line. The score was then recorded as the length in inches from the left end of the scale. A higher number represented more severe pain and a lower number represented less severe pain. Pain was assessed when the patient returned to the surgical ward, every 2 hours during the next &hour period, and then once every 8 hours through the third postoperative day. IV MS rates were recorded for each time interval. The amount and timing of IM injections were similarly recorded. Patients were evaluated for any complications or side effects associated with narcotic administration. These parameters included respiratory depression, hypotension, urinary retention, nausea, vomiting, drowsiness, lethargy, lightheadedness, hallucinations, agitation, or blurred vision. The date and time of the first bowel movement or flatus was also recorded. RESULTS

PATIENTIJ Fig 1.

Volume limited IV morphine delivery system.

Of the 46 patients entered into the study, 20 received intermittent IM MS analgesia while 26 received continuous IV MS. There were no significant differences between the IM or IV groups in age, sex, or weight (Table 2). Table 3 lists the types of major chest, abdominal, or orthopedic operations that the patients received in the IM and IV groups. Nissen fundoplica-

POSTOPERATIVE PAIN CONTROL IN CHILDREN

Table 2. Age, Weight,

and Sex of Morphine (Mean

Study Groups

+ SEMI

Intramuscular Mean age (yr)

187

6.17

Intravenous

+ 1.06

8.74

l-16

Range Mean weight (kg)

23.05

Range

‘;I

*p
:. :.:.>: . . . :.>>: ::::.::~ ..,....I ..:.-: . . .

;:z::’ .>>:: :.:.:.: .a:.*. .;:.:;;:;

::::y *...*... :.>:.:a

Patient IV

Fig 2. Total mean pain scores as assessed by nurse, parent, and patient.

Pearson correlation coefficients were used to determine the relationship of pain score reporting between the nurse, parent, and patient. Although the nurse, parent, and patient mean pain scale scores all correlated highly with each other, the pain scale scores of the nurse and patient had the highest correlation coefficient (0.8529). This coefficient was significantly higher (P < .05) than the correlation coefficient between the nurse and parent (0.7492) or the parent and patient (0.6148). The correlation coefficients between the nurse/parent and the parent/patient were not statistically significant. ._

‘------I *p:.:.. ..:.:.: .*...*. *:::::; .*.a.*. .*...-. .*.*.a. .*.*.*. ...

Parent •j

q

6-i

Procedures

i%o

%26

3?* n=26

tion was the single most common operation, while operations such as enterolysis, excision or biopsy of intraabdominal mass, cholecystectomy, splenectomy, nephrectomy, and simple appendectomy were categorized as exploratory laparotomy. Total mean pain scale scores for IM and IV morphine administration were compared using analysis of covariance (ANACOVA). When controlled for age, MS dose, and complications, a statistically significant difference (P < .007) was found between the IM and IV pain scores reported by the nurse, parent, and patient (Fig 2). When not controlling for age, MS dose, and complications, only the mean total pain scale scores of the IM group, as observed by the nurse, were significantly higher (P < .05, Student’s t test, Bonferoni correction) than pain scores of the IV group. The mean pain scores were further divided into an early postoperative period (8 to 16 hours immediately following operation) and the first, second, and third postoperative days. Pain scores of the IM group were consistently higher than those in the IV group for all periods (Fig 3). Significance between IM and IV pain scale scores, using the Student’s t test with Bonferoni correction, was observed only for the nurses’ assessment of pain in the first, second, and third postoperative days (P < .05). Table 3. Operative

correction)

3-15

Sex Female

Bonferoni

(t-test,

Bonferoni

-t-

TI

I

Correction)

l-

I

TI

Chest Pectus repair

0

3

Abdominal Nissen fundoplication

7

3

Ruptured appendicitis

1

4

Colon pull-through

0

1

Colostomy

0

2

Small bowel resection

3

1

Diaphragmatic hernia repair

1

0

Exploratory laparotomy

6

8

hY TIME

Orthopedic Tendon transfer

0

2

Osteotomy

2

2

20

26

Total

Postop

1

Day 2

Day 3

AFTER OPERATION

Fig 3. Mean pain scores divided into postoperative periods (NS, nurse; PA, parent; PT. patient).

HENDRICKSON ET AL

*

*p