Biomedical subjects
Publications and source records attributed to R Hickman.
In this review of a 25-year experience in full time surgical research, special emphasis is placed on the suitability of such a post for a female surgeon and on the particular skills that a woman can bring to such a position.
The metabolism of lidocaine to monoethylglycinexylidide has been found useful as an indicator of liver function in association with liver transplantation. It has been postulated that this is due to the common effect of hypoxic damage on liver function and lidocaine metabolism. The effects of hypoxia on the elimination of lidocaine and the formation of monoethylglycinexylidide and on indexes of liver function were investigated with the isolated perfused pig liver preparation. This study was performed at similar hepatic effluent lidocaine concentrations of approximately 5 micrograms.ml-1 in normoxic (n = 7) and hypoxic (n = 8) livers of similar mass harvested from male Landrace x Large White pigs and perfused at standard unit hepatic flow rates. Whole blood lidocaine extraction ratio was 0.63 +/- 0.02 in normoxic livers (30% O2 at oxygenator inflow). It was significantly less (0.23 +/- 0.03) in livers subjected to hypoxia (2% O2 at oxygenator inflow), as were hepatic clearance (57.1 +/- 2.1 vs. 20.3 +/- 3.1 ml.min-1.100 gm-1), intrinsic clearance (1,706 +/- 182 vs. 284 +/- 53 ml.min-1.100 gm-1) and monoethylglycinexylidide formation as indicated by monoethylglycinexylidide/lidocaine ratios in the hepatic venous effluent (0.379 +/- 0.061 vs. 0.073 +/- 0.014) (p < 0.01). Hepatic oxygen consumption, adenine nucleotide status and bile flow were significantly impaired by hypoxia. Whereas perfusate potassium concentration increased early, AST levels showed delayed increases and ALT levels showed no changes. These changes correlated strongly with hepatic lidocaine elimination (p < 0.01). We conclude that lidocaine metabolism may be an early indicator of severe hepatic hypoxia.
Lidocaine is administered to assess donor or recipient liver function during hepatic transplantation. This study was performed to determine whether lidocaine administered at a constant concentration affected hepatic function or had demonstrable effects on hepatocellular ultrastructure. Fourteen pigs were randomly allocated to receive either a two-stage infusion of lidocaine hydrochloride or of saline. Transhepatic blood samples were taken and ultrasonic portal venous and hepatic arterial blood flow readings made on animals anesthetized with isoflurane in nitrous oxide. Liver biopsies were taken for histological analysis and determination of adenine nucleotide status prior to and after 2 hr of the two-stage infusion. A mean systemic constant plasma lidocaine concentration of 5.9 micrograms/ml was achieved during the second hour of infusion. There were no differences between the two groups in a large number of indices of hepatic function and plasma composition prior to and during the second hour of the respective infusions. Hepatic blood flow was also similar at these times. On histological examination there were no electron microscopic changes that could be specifically attributed to the administration of lidocaine. However, there were progressive changes with time. This study suggests that in anesthetized pigs a constant lidocaine concentration of about 6 micrograms/ml has no detrimental effect on hepatic function. Progressive hepatic ultrastructural changes occurred that could not be attributed to the administration of lidocaine. These may be the result of anesthetic administered or the surgery performed.
Previous studies of total and ionized calcium in the plasma of liver transplant recipients have been conducted in patients with preexisting liver disease or who received blood transfusion. The intraoperative decline in plasma total and ionized calcium has been attributed to the effects of liver disease and/or the citrate in transfused blood. The present study was conducted in normal porcine recipients of liver stored either with EuroCollins or University of Wisconsin (UW) solution for 6 hr, compared with livers flushed with Ringer's lactate without storage. No blood transfusion was given. Mean total plasma calcium levels declined significantly after storage with UW solution to a nadir approximately 65-70% of preoperative levels. This decline persisted for two to five days. Mean levels of plasma ionized calcium declined lowest after flushing with UW solution but only to 82% of preoperative (NS). There was an increase in plasma total magnesium in the recipients of livers flushed with EuroCollins or UW solutions, which resolved within 30 min and which was probably related to magnesium content of the flushing solution. It is concluded that while the changes in plasma total and ionized calcium are moderate and of little clinical significance, they could be aggravated under clinical conditions by massive blood transfusion. Changes in plasma magnesium seemed to be directly attributable to the magnesium content of flushing solutions but the same relationship did not exist for changes in plasma calcium.
In vivo and ex vivo liver function was compared using the same livers to exclude interanimal variation in hepatic function. Six male pigs were anesthetized, and catheters and perivascular flow probes placed for transhepatic sampling and hepatic arterial and portal venous flow measurement. After a 2-h in vivo study period, the livers were resected and studied immediately afterwards for a further 2 h ex vivo as an isolated perfused preparation (Experiment A). Hepatic function in a further 6 pig livers (Experiment B) was studied ex vivo only for comparison with the ex vivo livers from Expt. A to determine whether the prior in vivo study had affected hepatic function. Despite using the same livers with similar total hepatic blood flows, (0.91 +/- 0.16 ml.g-1 x min-1) in vivo and (0.84 +/- 0.03 ml.g-1 x min-1) ex vivo, hepatic oxygen consumption (6.5 +/- 0.9 vs 2.6 +/- 0.2 ml O2 x 100 g-1), adenosine-5-triphosphate content (5.22 +/- 0.62 vs 4.14 +/- 0.71 microM.g liver-1) and bile flow (15.1 +/- 1.2 vs 6.0 +/- 1.0 ml.h-1) were initially less ex vivo and remained so throughout the study, while perfusate potassium (initially) (3.7 +/- 0.1 vs 6.4 +/- 0.3 meq.l-1), and aspartate aminotransferase (50 +/- 9 vs 76 +/- 5UL-1) was consistently higher than in vivo values. Initial hepatic energy charge (0.620 +/- 0.034 vs 0.552 +/- 0.061) and total adenine nucleotides 12.49 +/- 0.60 vs 11.66 +/- 0.62 microM.g liver-1) were not different and remained so subsequently.(ABSTRACT TRUNCATED AT 250 WORDS)
This study was conducted to determine whether the administration of tri-iodothyronine (T3) to brain-dead donor pigs would improve hemodynamic instability, serum levels of thyroid hormones, or the outcome of transplantation of donor livers. Brain death was caused in young pigs (25-38 kg) by rapid inflation of an intracranially implanted balloon catheter. The animals were maintained on a ventilator and frequent measurements of acid/base balance, electrolytes, and glucose were made. At the end of 16 hr, livers were removed and implanted into prepared recipients. Serum-free tri-iodothyronine fell to zero at the end of 16 hr, and there was a 4-6-fold decline in free thyroxine (T4). The levels of serum reverse T3 (rT3) however, increased up to 6-fold. In animals treated with tri-iodothyronine 2 micrograms/hr, the serum levels of free T3 and T4 were not changed but the levels of serum reverse T3 (rT3) increased further. There were no apparent correlations between any hemodynamic parameter and serum thyroid hormone levels in the donors. After the liver transplants, recipients could be divided into those that survived longer than 6 days and those that did not. Although there were significant differences in the plasma levels of alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase, there was no correlation between survival and whether the donor had received tri-iodothyronine. Although other hormones, including insulin and cortisol, may also be necessary, there is no indication from these studies that the administration of tri-iodothyronine to brain-dead donors of liver grafts benefits the serum hormone levels in the donors or the subsequent survival of the recipients.
Plasma lidocaine decay after injection was studied in five anaesthetized pigs and fitted to a two compartment open model. Derived pharmacokinetic parameters were employed to rapidly achieve plateau concentrations within 60 min of starting a two stage infusion of lidocaine hydrochloride. Hepatic extraction and clearance of lidocaine at steady state were determined in 10 pigs by transhepatic sampling and measurement of hepatic arterial and portal venous blood flow using perivascular ultrasonic flow probes placed at laparotomy. These data were compared with similar studies performed in man as well as the sheep, dog, monkey and cat. The lidocaine extraction ratio of 0.60 in the pig was found to be similar to that determined by others in man.
We investigated systemic effects and possible mechanisms for lethality of intravenously infused cocaine in spontaneously breathing and mechanically ventilated unconscious Landrace male pigs weighing about 26 kg (25.75 +/- 0.25 kg) that were pretreated with either saline solution (groups 1 and 3) or iso-ompa (tetraisopropyl pyrophosphoramide), a specific plasma cholinesterase inhibitor (groups 2 and 4). Pigs were made unconscious with sodium thiopental and ventilated with 70% nitrous oxide and 30% oxygen. A carotid arterial cannula and a Swan-Ganz catheter were inserted for hemodynamic monitoring. Pigs in groups 1 and 2 were then allowed to breathe spontaneously and groups 3 and 4 were mechanically ventilated. After obtaining a stable state, as judged by cardiovascular and respiratory parameters, the pigs were infused intravenously with cocaine hydrochloride (0.8 mg/kg/min) until the time of cardiac arrest. Respiratory and cardiovascular parameters, blood temperature, and sodium and potassium levels were monitored. The times of occurrence of respiratory arrests (RA), cardiac arrests (CA), and convulsions were recorded. Our results showed that RA is the primary cause of death in spontaneously breathing pigs and that mechanical ventilation significantly delayed the occurrence of CA (p < 0.05). Significant decreases in cardiac output, mean blood pressure, and heart rate as well as significant increases in systemic and pulmonary vascular resistances, central venous and pulmonary wedge pressures, and blood K+ levels were noted in mechanically ventilated pigs (p < 0.05). Variable hemodynamic responses were noticed in spontaneously breathing pigs. Our results also showed that no significant changes occurred in blood catecholamine levels when compared with baseline values associated with the infusion of toxic doses of cocaine.(ABSTRACT TRUNCATED AT 250 WORDS)
Current knowledge of liver regeneration after reduced liver transplantation is limited. Warm ischemia is one component of the reduced liver transplantation procedure that could have an impact on the regenerative response. To study this effect, we performed partial hepatectomy on male Long-Evans rats, with animals divided into four groups: group 1 underwent partial hepatectomy only; group 2 underwent partial hepatectomy and 40 min of ischemia; group 3 underwent partial hepatectomy, 40 min of ischemia and portocaval shunt surgery; and group 4 underwent partial hepatectomy and orthotopic autograft surgery. Group 5 consisted of sham-operated animals. Animals were killed 4, 24, 48, 72 and 96 hr after surgery. Thymidine kinase activity, mitotic index, a liver mass index and ornithine decarboxylase levels were used as parameters of liver regeneration. Aspartate transaminase was recorded. Maximal thymidine kinase and mitotic index were observed in group 1 animals at 24 hr. In groups 2, 3 and 4 maximal thymidine kinase activity and mitotic activity were observed 24 hr later at 48 hr. The magnitude of the peak response in these groups appeared to correlate with the duration of portal venous occlusion, with greatest increases occurring in those groups where portal stasis was most prolonged. The increase in liver mass for these groups was also delayed with respect to group 1 animals. The anticipated peak in ornithine decarboxylase levels was seen at 4 hr in group 1. The ornithine decarboxylase response in the other groups was disorganized, with delay of the recorded peaks.(ABSTRACT TRUNCATED AT 250 WORDS)
Laryngoscopy and endotracheal intubation is a potent sympathetic stimulus in adults. Neonates are frequently intubated, but few data exist on the cerebral effects of this intervention. The cardiovascular and intracranial effects of laryngoscopy and endotracheal intubation were studied in 17 hypercarbic neonatal piglets. The mean arterial pressure in the study group (11 piglets) increased significantly within 2 minutes of the stimulus, and remained elevated for almost 14 minutes. The intubated animals showed significantly more haemorrhage in the basal area of the brain than the 6 control animals. The distribution suggests bleeding in the choroid plexus of the 4th ventricle. The significance of such bleeds is not immediately apparent, since none of the animals was grossly neurologically affected by the intervention. However, subtle long-term neurological deficits cannot be excluded and this aspect requires further study. Laryngoscopy and endotracheal intubation may cause non-lethal haemorrhage in the choroid plexus and central canal of the hindbrain in hypercarbic, neonatal piglets.
Present techniques for renal transplantation in the rat include a period of 20-25 minutes warm ischemia. Our method combines a recently described sleeve anastomotic technique for the renal artery, conventional end-to-end anastomosis of the renal vein, and implantation of the ureter into the bladder. This has resulted in a reproducible ischemic interval of 12-14 minutes. Plasma creatinine and histological features in animals sacrificed from 10 to 30 days after transplantation were within normal limits with no evidence of ischemic damage. A further advantage of the technique is that kidneys can be exchanged between the donor and recipient. It is recommended that this procedure, which reduces the ischemic interval by up to 50%, should be learned and employed in studies of renal transplantation in the rat, especially if such studies include the prior administration of cyclosporine, which may aggravate the effects of ischemia.
The precise cause of allograft dysfunction after renal transplantation often cannot be established by non-invasive means. In clinical practice, radionuclide scans form an integral part of the clinician's armamentarium in the assessment of these patients. Unfortunately, in the clinical setting more than one pathological process may be responsible for the impaired function, making it difficult to correlate the scan appearances with the pathology. In this study in rats we compared the renal DTPA scan appearances of the various pathological processes which may cause renal allograft dysfunction in the immediate post-transplant period.
Induction of unrepairable DNA damage, accumulation of misrepaired DNA damage, and generation of imbalances in competing biochemical and/or metabolic processes have been proposed to explain the relationship between radiation-induced DNA damage and cell lethality. Theoretically, the temperature dependence of the critical DNA repair process(es) should be 1) either independent of or identical to the temperature dependence of cell killing if the first two hypotheses are correct, and 2) different if the third hypothesis is correct. To test this, exponentially growing rat 9L brain tumor cells were left at 37 degrees C or equilibrated for 3-14 h at 20 degrees C before irradiation. Cells were irradiated and allowed to repair at either 20 degrees C or 37 degrees C. Alternatively, the cells were irradiated at one of these temperatures and immediately shifted to the other temperature for repair. DNA damage was assessed by the alkaline elution technique; cell kill was assessed by a clonogenic assay. 9L cells maintained at 20 degrees C or 37 degrees C sustained the same amount of DNA damage as measured by alkaline elution. DNA repair instantaneously assumed the rate characteristic of the postirradiation temperature. For 9L cells equilibrated, irradiated, and repaired at 20 degrees C, the half-time of the fast phase of the DNA repair decreased by a factor of approximately 2 and the half-time of the slow phase decreased by a factor of approximately 5 over that measured in cells incubated, irradiated and repaired at 37 degrees C. Although the rate of DNA repair decreased substantially at 20 degrees C, the survival of 9L cells that were equilibrated and irradiated at 20 degrees C was greater (p less than 10(-4)) than those incubated and irradiated at 37 degrees C, when assayed by an immediate plating protocol. In addition, the survival of 9L cells equilibrated and irradiated at 20 degrees C and then shifted to 37 degrees C immediately after irradiation was greater (p less than 10(-2)) than that obtained with any other delayed plating protocol. Thus, the temperature dependence of the DNA repair processes measured by alkaline elution was different from the temperature dependence of cell killing measured either by an immediate or delayed plating protocol. These data support the hypothesis that many irradiated 9L tumor cells die because of imbalances in sets of competing biochemical and/or metabolic processes.
It has been suggested recently that preoperative plasma thyroid hormone levels may be used to predict the success of liver transplantation in prospective recipients and also perhaps that postoperative levels may be used to identify rejection. In the present study of unimmunosuppressed porcine recipients of liver allografts, two groups of animals were identified--those that died within five days postoperatively and the other group that were longer survivors. On the first postoperative day plasma levels of total and free T4 and total and free T3 declined and of total rT3 increased. In survivors these levels returned towards normal within three days, while they persisted in nonsurvivors. As there was no obvious cause of graft failure in nonsurvivors, the state might be considered to represent primary graft nonfunction in pigs, and the changes in plasma thyroid hormone levels may be predictive of this condition; a study in patients may confirm this.
It has been suggested recently that patients with fulminant liver failure should be prepared for transplantation by early hepatectomy, yet the acute effects of removal of the liver upon the coagulation profile and certain hormones are not known. This study was conducted on totally hepatectomized pigs that survived up to 27 hr. Measurements were made of serum insulin, plasma glucagon (IRG and GLI), glucose, catecholamines, and the coagulation profile. The increase in serum insulin was directly related to levels of plasma glucose--there was a 100-fold increase in animals with plasma glucose levels greater than 400 mg/100 ml and none when blood glucose was less than 100 mg/100 ml. Plasma glucagon showed a sharp transient increase within 1 hr of hepatectomy and a slow rise thereafter with levels apparently unrelated to serum insulin or plasma glucose. There was a transient increase in plasma adrenaline but a sharp continuous increase in plasma norepinephrine. No changes of note occurred in the coagulation profile--even levels of fibrinogen only declined by 20% in 27 hr. The study has shown that early total hepatectomy is safe as far as changes in coagulation are concerned but changes in serum insulin and especially plasma norepinephrine may be of more significance.
Elevation of serum insulin and plasma glucagon have been reported during and immediately after clinical and experimental liver transplantation and in patients with cirrhosis and surgically created or spontaneous portacaval shunts. There is controversy about the relative roles of portal diversion and impaired liver function in the genesis of these elevated levels of pancreatic hormones. End-to-side portacaval shunt was made in normal pigs which were fitted with catheters which allowed transhepatic sampling during and for 4 hr after the operation. Within 5 min of opening the shunt, there was a sixfold increase in portal venous insulin concentrations but hepatic clearance of insulin and the arterial concentration were unaltered. The increase in insulin was sustained for 2 hr. A twofold increase occurred within 1 hr in portal venous glucagon concentration which appeared to be predominantly of pancreatic origin and which continued for the 4 hr of the study. Hepatic glucose uptake did not occur after portacaval shunting despite levels of glucose elevated two-fold by iv infusion. There were no changes in aspartate aminotransferase, hepatic tissue energy charge, or total adenine nucleotides, suggesting that hepatic function was intact. It is concluded that portal diversion results in an increase in insulin and glucagon secretion and in the absence of hepatic uptake of glucose. This is a novel observation with relevance especially in liver transplantation when portal diversion for at least 1 hr forms part of the procedure.(ABSTRACT TRUNCATED AT 250 WORDS)
As efforts to assess the viability of liver grafts continue, the recent description of noninvasive measurement by fluorimetry or magnetic resonance spectrometry of adenine nucleotides has brought energy charge into focus again as an index of viability. Many previous studies have been conducted in human donor livers that have clinical relevance but which cannot be standardized, or in rats in which the hepatic artery is not anastomosed. In the present study, pig livers were definitively rendered ischemic for 1 or 2 hr. In one group the livers were then revascularized (intact) while in the other, the livers were removed during the final 20-30 min of the ischemic period and were subjected to autograft. There was a marked difference in survival between the intact and the autograft groups. One hour of ischemia in the intact group was associated with survival comparable to that of autograft controls (8-100 days); 2 hr of ischemia caused shortened survival, ranging from 2 to 18 days. In the recipients of autografts, survival after 1 hr of ischemia ranged from 3 to 16 days; after 2 hr of ischemia no autograft recipient survived overnight. The energy charge returned to the preoperative level after 2 hr of ischemia in both intact and autograft groups. The concentrations remained depressed after 2 hr of ischemia in autografted animals, thus being associated with survival. However, the patterns of total adenine nucleotide and adenosine triphosphate were not always similar to those of energy charge. The concentrations of aspartate aminotransferase were similarly elevated in all ischemic groups irrespective of duration or subsequent survival. There was, however, a close association between euglobulin lysis times (ELT) and survival. In the autograft recipients of livers subjected to 2 hr of ischemia that did not survive overnight the ELT remained significantly shortened. It is concluded that adenine nucleotide metabolism is important as an index of viability, but that concentrations of total and individual adenine nucleotides and the energy change all need to be computed. There does, however, appear to be an absolute relationship between survival and euglobulin lysis time that would be clinically useful in patients undergoing liver transplantation or hepatic vascular exclusion.
This study compared the function of reduced grafts prepared in situ or ex vivo and transplanted immediately or after 4 hr of cold storage. Measurements of acid/base balance, plasma electrolytes, albumin, and urea showed no differences between groups. There was no difference between the increase and decline of plasma AST in recipients of grafts transplanted immediately after either ex vivo or in situ reduction; the increase in plasma AST of recipients of stored grafts was up to 10-fold and persisted until the end of the study at 7 days, with some decline. Plasma fibrinogen decreased intraoperatively but levels were restored within 24 hr in all groups; plasma prothrombin and partial thromboplastin times were not significantly disturbed. The patterns of decline and return of tissue adenine nucleotides were similar in all groups. While the regenerative response measured by tissue thymidine kinase and mitotic figures was not different between the groups, comparison with results from a group of partially hepatectomized animals showed a 3-4-fold depression in response in reduced liver grafts. The contributions of the effects of ischemia, flushing, and preservation to the depressed regenerative response of reduced liver grafts need to be determined. The present studies suggest however, that with regard to functional assessment, results are not affected either by ex vivo or in situ reduction of the graft, or by cold storage for 4 hr.