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Use of an in vivo oxygen electrode to determine the effect of hemorrhagic shock on liver oxygen tension
Use of an In Vivo Oxygen Electrode to Determine the Effect of Hemorrhagic Shock on Liver Oxygen Tension John M. Hartong, LTC MC,’ El Paso, Texas Robert S. Dixon, CPT VC, El Paso, Texas Thelma T. Meyers, DAC, El Paso, Texas
The development of a small portable oxygen analyzer that utilizes a disposable in vivo catheter for the measurement of arterial and tissue oxygen tension (PO,) has been the subject of several recent reports [l-4]. Gold et al [5] compared the standard benchtype electrode (Radiometer) with the in vivo electrode (International.Biophysics Corporation [IBC], 2700 DuPont Drive, Irvine, CA 92264) in tonometered blood and found the in vivo electrode to be more accurate. The IBC in vivo catheter was used to study the effect of hemorrhagic shock on liver POs and is the subject of this report. Material and Methods A healthy population of laboratory bred beagle dogs, averaging 10 kg in weight, was used for the study. Food was withheld 12 hours before surgery. Prior to induction of anesthesia, the animals were given atropine sulfate (0.04 mg/kg) and acepromazine maleate (0.5 mg/kg). Anesthesia was induced by intravenous injection of 2.5 per cent thiamylal sodium and maintained with methoxyflurane and oxygen via cuffed endotracheal tube. The skin was prepared for surgery utilizing povidoneiodine soap and solution. One (control group) or both femoral arteries (shock group) were cannulated with PE240 catheters to which a three-way stopcock was fitted. One femoral artery cannula was connected via a pressure transducer (Hewlett-Packard, Las Cruces, NM 88001) to an Electronics for Medicine DR-8 physiologic monitor allowing continuous measurement of arterial pressure. The second femoral artery cannula was used to bleed the animals in the shock group directly into an ACD blood collection bag to produce hypovolemic shock and for infusion during the resuscitation period. A midline abdominal incision was made and the IBC POz probe was placed into the liver through an 18 gauge needle. A differential surface electrode was wetted with saline and attached to a defatted area of skin near the abdominal incision. An IBC Model 210 gaseous oxygen sensor was inserted in the anestheticoxygen delivery system at the endotracheal tube. Liver POz
and fraction of inspired oxygen (FIOz) were monitored on each animal with the IBC Multipurpose Differential Oxygen Analyzer. Following a 45 minute stabilization period, the animals in the shock group were bled down to a pressure of 40 torr over a 5 minute period and maintained at that level for 2 hours with repeated blood withdrawal as necessary. The shed volume averaged 400 cc and represented 55 to 60 per cent of the calculated total blood volume. Liver POz and FIOs readings were taken at 15 minute intervals, arterial PO:! at 30 minute intervals and at 1 hour after resuscitation. Arterial POz (PaOz) was measured with an IL Model 113 pH/Gas Analyzer (Instrumentation Laboratories, 113 Hartwell Ave, Lexington, MA 02173). At the end of the shock period, resuscitation was accomplished by rapidly returning the shed blood plus an equal volume of Ringer’s lactate solution through a 16 gauge medicut inserted into the cephalic vein. Results
There were five animals in each of the two groups. One animal in the shock group died. In the control group Pa02 values averaged 373 torr, FIOs averaged 509 torr, and liver POs averaged 44.4 torr. In the shock group Pa02 values averaged 380 torr, FIOz averaged 519 torr, and liver POs averaged 19.7 torr. Results are illustrated in Figure 1. Application of an unpaired t test indicates the difference in liver PO;! values between the two groups to be highly significant (p
From the TraumaCenter, William Beaumont Army Medical Center, El Paso, Texas. * Present address and reprint requests: Department of Surgery, the Frederick C. Smith Clinic, Marion, Ohio 43302.
Volume 133, May 1977
in vivo PO2 probe has been
demonstrated in a variety of clinical and laboratory situations [l-4,6,7]. Use of the probe in critical care areas of the hospital should become more common-
607
Hartong, Dixon, and Meyers
therapy, but will also allow rapid assessment of that therapy. Caution should be exercised in interpreting results obtained in patients anesthetized with halothane. Halothane has been noted to significantly increase PO2 readings at oxygen tension levels below 105 torr whereas enflurane and methoxyflurane do not affect readings [9]. Summary
Figure 1. Comparison of tissue POP, PaOp, and F102 levels between 5 animals undergoing hemorrhagic shock and resuscitation and 5 controls.
place as the required equipment is relatively inexpensive, small, portable, battery-powered, and easily obtained, does not require a technician or special training, and although its insertion into tissue is an invasive procedure, it is equivalent to an intramuscular injection. The results of this study and those reported by others [1,3,8] d emonstrate markedly decreased peripheral and central tissue PO2 in low flow states despite normal or very high PaOz. .In some instances, tissue PO2 approaches the critical mitochondrial level (4 to 6 torr). Oxygen therapy in patients with trauma, gastrointestinal hemorrhage, cardiogenic shock, cardiopulmonary bypass, and a host of other conditions that cause a low flow state is frequently determined on the basis of PaOn. These results suggest that this basis for decisions regarding oxygen therapy, by mechanical ventilation or otherwise, is inadequate in this clinical setting. Improvement in the flow state by whatever means indicated, not alteration of oxygen therapy, is the proper course of action. Measurement of muscle PO2 in patients during and after cardiopulmonary bypass surgery has demonstrated that tissue PO2 decreases during bypassing despite an increase in Pa02 to 400 torr and begins to increase as soon as bypassing is terminated and pulsatile flow is returned[l,8]. The existence of a group of patients in an unrecognized low flow state with marginal, adequate, or normal vital signs, temperature, and color of the extremities, electrocardiograms, observations of mental status, and acceptable, normal, or elevated Pa02 is highly probable. Such parameters are all frequently used but constitute indirect means of measuring tissue perfusion. Measurement of tissue PO2 will not only identify this group of patients to enable institution of corrective
608
Measurement of arterial and liver tissue oxygen tension (POz) in animals subjected to hemorrhagic shock demonstrates a significant (p
The American Journal of Surgery
The development of a small portable oxygen analyzer that utilizes a disposable in vivo catheter for the measurement of arterial and tissue oxygen tension (PO,) has been the subject of several recent reports [l-4]. Gold et al [5] compared the standard benchtype electrode (Radiometer) with the in vivo electrode (International.Biophysics Corporation [IBC], 2700 DuPont Drive, Irvine, CA 92264) in tonometered blood and found the in vivo electrode to be more accurate. The IBC in vivo catheter was used to study the effect of hemorrhagic shock on liver POs and is the subject of this report. Material and Methods A healthy population of laboratory bred beagle dogs, averaging 10 kg in weight, was used for the study. Food was withheld 12 hours before surgery. Prior to induction of anesthesia, the animals were given atropine sulfate (0.04 mg/kg) and acepromazine maleate (0.5 mg/kg). Anesthesia was induced by intravenous injection of 2.5 per cent thiamylal sodium and maintained with methoxyflurane and oxygen via cuffed endotracheal tube. The skin was prepared for surgery utilizing povidoneiodine soap and solution. One (control group) or both femoral arteries (shock group) were cannulated with PE240 catheters to which a three-way stopcock was fitted. One femoral artery cannula was connected via a pressure transducer (Hewlett-Packard, Las Cruces, NM 88001) to an Electronics for Medicine DR-8 physiologic monitor allowing continuous measurement of arterial pressure. The second femoral artery cannula was used to bleed the animals in the shock group directly into an ACD blood collection bag to produce hypovolemic shock and for infusion during the resuscitation period. A midline abdominal incision was made and the IBC POz probe was placed into the liver through an 18 gauge needle. A differential surface electrode was wetted with saline and attached to a defatted area of skin near the abdominal incision. An IBC Model 210 gaseous oxygen sensor was inserted in the anestheticoxygen delivery system at the endotracheal tube. Liver POz
and fraction of inspired oxygen (FIOz) were monitored on each animal with the IBC Multipurpose Differential Oxygen Analyzer. Following a 45 minute stabilization period, the animals in the shock group were bled down to a pressure of 40 torr over a 5 minute period and maintained at that level for 2 hours with repeated blood withdrawal as necessary. The shed volume averaged 400 cc and represented 55 to 60 per cent of the calculated total blood volume. Liver POz and FIOs readings were taken at 15 minute intervals, arterial PO:! at 30 minute intervals and at 1 hour after resuscitation. Arterial POz (PaOz) was measured with an IL Model 113 pH/Gas Analyzer (Instrumentation Laboratories, 113 Hartwell Ave, Lexington, MA 02173). At the end of the shock period, resuscitation was accomplished by rapidly returning the shed blood plus an equal volume of Ringer’s lactate solution through a 16 gauge medicut inserted into the cephalic vein. Results
There were five animals in each of the two groups. One animal in the shock group died. In the control group Pa02 values averaged 373 torr, FIOs averaged 509 torr, and liver POs averaged 44.4 torr. In the shock group Pa02 values averaged 380 torr, FIOz averaged 519 torr, and liver POs averaged 19.7 torr. Results are illustrated in Figure 1. Application of an unpaired t test indicates the difference in liver PO;! values between the two groups to be highly significant (p
From the TraumaCenter, William Beaumont Army Medical Center, El Paso, Texas. * Present address and reprint requests: Department of Surgery, the Frederick C. Smith Clinic, Marion, Ohio 43302.
Volume 133, May 1977
in vivo PO2 probe has been
demonstrated in a variety of clinical and laboratory situations [l-4,6,7]. Use of the probe in critical care areas of the hospital should become more common-
607
Hartong, Dixon, and Meyers
therapy, but will also allow rapid assessment of that therapy. Caution should be exercised in interpreting results obtained in patients anesthetized with halothane. Halothane has been noted to significantly increase PO2 readings at oxygen tension levels below 105 torr whereas enflurane and methoxyflurane do not affect readings [9]. Summary
Figure 1. Comparison of tissue POP, PaOp, and F102 levels between 5 animals undergoing hemorrhagic shock and resuscitation and 5 controls.
place as the required equipment is relatively inexpensive, small, portable, battery-powered, and easily obtained, does not require a technician or special training, and although its insertion into tissue is an invasive procedure, it is equivalent to an intramuscular injection. The results of this study and those reported by others [1,3,8] d emonstrate markedly decreased peripheral and central tissue PO2 in low flow states despite normal or very high PaOz. .In some instances, tissue PO2 approaches the critical mitochondrial level (4 to 6 torr). Oxygen therapy in patients with trauma, gastrointestinal hemorrhage, cardiogenic shock, cardiopulmonary bypass, and a host of other conditions that cause a low flow state is frequently determined on the basis of PaOn. These results suggest that this basis for decisions regarding oxygen therapy, by mechanical ventilation or otherwise, is inadequate in this clinical setting. Improvement in the flow state by whatever means indicated, not alteration of oxygen therapy, is the proper course of action. Measurement of muscle PO2 in patients during and after cardiopulmonary bypass surgery has demonstrated that tissue PO2 decreases during bypassing despite an increase in Pa02 to 400 torr and begins to increase as soon as bypassing is terminated and pulsatile flow is returned[l,8]. The existence of a group of patients in an unrecognized low flow state with marginal, adequate, or normal vital signs, temperature, and color of the extremities, electrocardiograms, observations of mental status, and acceptable, normal, or elevated Pa02 is highly probable. Such parameters are all frequently used but constitute indirect means of measuring tissue perfusion. Measurement of tissue PO2 will not only identify this group of patients to enable institution of corrective
608
Measurement of arterial and liver tissue oxygen tension (POz) in animals subjected to hemorrhagic shock demonstrates a significant (p
The American Journal of Surgery